diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index a4ad9df0ead23..22d50881e3955 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -16864,7 +16864,7 @@ namespace ts {
                 if (source.flags & (TypeFlags.Object | TypeFlags.Conditional) && source.aliasSymbol &&
                     source.aliasTypeArguments && source.aliasSymbol === target.aliasSymbol &&
                     !(source.aliasTypeArgumentsContainsMarker || target.aliasTypeArgumentsContainsMarker)) {
-                    const variances = getAliasVariances(source.aliasSymbol);
+                    const variances = getAliasVariances(source.aliasSymbol, relation === assignableRelation ? isRelatedTo : compareTypesAssignable);
                     if (variances === emptyArray) {
                         return Ternary.Maybe;
                     }
@@ -17095,7 +17095,7 @@ namespace ts {
                         // We have type references to the same generic type, and the type references are not marker
                         // type references (which are intended by be compared structurally). Obtain the variance
                         // information for the type parameters and relate the type arguments accordingly.
-                        const variances = getVariances((<TypeReference>source).target);
+                        const variances = getVariances((<TypeReference>source).target, relation === assignableRelation ? isRelatedTo : compareTypesAssignable);
                         // We return Ternary.Maybe for a recursive invocation of getVariances (signalled by emptyArray). This
                         // effectively means we measure variance only from type parameter occurrences that aren't nested in
                         // recursive instantiations of the generic type.
@@ -17988,13 +17988,13 @@ namespace ts {
             return result;
         }
 
-        function getAliasVariances(symbol: Symbol) {
+        function getAliasVariances(symbol: Symbol, compareTypes: (source: Type, target: Type) => Ternary) {
             const links = getSymbolLinks(symbol);
             return getVariancesWorker(links.typeParameters, links, (_links, param, marker) => {
                 const type = getTypeAliasInstantiation(symbol, instantiateTypes(links.typeParameters!, makeUnaryTypeMapper(param, marker)));
                 type.aliasTypeArgumentsContainsMarker = true;
                 return type;
-            });
+            }, compareTypes);
         }
 
         // Return an array containing the variance of each type parameter. The variance is effectively
@@ -18002,11 +18002,12 @@ namespace ts {
         // generic type are structurally compared. We infer the variance information by comparing
         // instantiations of the generic type for type arguments with known relations. The function
         // returns the emptyArray singleton when invoked recursively for the given generic type.
-        function getVariancesWorker<TCache extends { variances?: VarianceFlags[] }>(typeParameters: readonly TypeParameter[] = emptyArray, cache: TCache, createMarkerType: (input: TCache, param: TypeParameter, marker: Type) => Type): VarianceFlags[] {
+        function getVariancesWorker<TCache extends { variances?: VarianceFlags[] }>(typeParameters: readonly TypeParameter[] = emptyArray, cache: TCache, createMarkerType: (input: TCache, param: TypeParameter, marker: Type) => Type, compareTypes: (source: Type, target: Type) => Ternary): VarianceFlags[] {
             let variances = cache.variances;
             if (!variances) {
                 // The emptyArray singleton is used to signal a recursive invocation.
                 cache.variances = emptyArray;
+                let encounteredMaybeResult = false;
                 variances = [];
                 for (const tp of typeParameters) {
                     let unmeasurable = false;
@@ -18018,14 +18019,28 @@ namespace ts {
                     // invariance, covariance, contravariance or bivariance.
                     const typeWithSuper = createMarkerType(cache, tp, markerSuperType);
                     const typeWithSub = createMarkerType(cache, tp, markerSubType);
-                    let variance = (isTypeAssignableTo(typeWithSub, typeWithSuper) ? VarianceFlags.Covariant : 0) |
-                        (isTypeAssignableTo(typeWithSuper, typeWithSub) ? VarianceFlags.Contravariant : 0);
+
+                    const subResult = compareTypes(typeWithSub, typeWithSuper);
+                    const superResult = compareTypes(typeWithSuper, typeWithSub);
+                    let variance = (subResult ? VarianceFlags.Covariant : 0) |
+                        (superResult ? VarianceFlags.Contravariant : 0);
+                    if (subResult === Ternary.Maybe || superResult === Ternary.Maybe) {
+                        variance |= VarianceFlags.Unmeasurable;
+                        encounteredMaybeResult = true;
+                    }
                     // If the instantiations appear to be related bivariantly it may be because the
                     // type parameter is independent (i.e. it isn't witnessed anywhere in the generic
                     // type). To determine this we compare instantiations where the type parameter is
                     // replaced with marker types that are known to be unrelated.
-                    if (variance === VarianceFlags.Bivariant && isTypeAssignableTo(createMarkerType(cache, tp, markerOtherType), typeWithSuper)) {
-                        variance = VarianceFlags.Independent;
+                    if (variance === VarianceFlags.Bivariant) {
+                        const otherResult = compareTypes(createMarkerType(cache, tp, markerOtherType), typeWithSuper);
+                        if (otherResult === Ternary.Maybe) {
+                            variance |= VarianceFlags.Unmeasurable;
+                            encounteredMaybeResult = true;
+                        }
+                        if (otherResult) {
+                            variance = VarianceFlags.Independent;
+                        }
                     }
                     outofbandVarianceMarkerHandler = oldHandler;
                     if (unmeasurable || unreliable) {
@@ -18038,17 +18053,22 @@ namespace ts {
                     }
                     variances.push(variance);
                 }
-                cache.variances = variances;
+                if (!encounteredMaybeResult) {
+                    cache.variances = variances;
+                }
+                else {
+                    cache.variances = undefined;
+                }
             }
             return variances;
         }
 
-        function getVariances(type: GenericType): VarianceFlags[] {
+        function getVariances(type: GenericType, compareTypes: (source: Type, target: Type) => Ternary): VarianceFlags[] {
             // Arrays and tuples are known to be covariant, no need to spend time computing this.
             if (type === globalArrayType || type === globalReadonlyArrayType || type.objectFlags & ObjectFlags.Tuple) {
                 return arrayVariances;
             }
-            return getVariancesWorker(type.typeParameters, type, getMarkerTypeReference);
+            return getVariancesWorker(type.typeParameters, type, getMarkerTypeReference, compareTypes);
         }
 
         // Return true if the given type reference has a 'void' type argument for a covariant type parameter.
@@ -19313,7 +19333,7 @@ namespace ts {
                 if (source.aliasSymbol && source.aliasTypeArguments && source.aliasSymbol === target.aliasSymbol) {
                     // Source and target are types originating in the same generic type alias declaration.
                     // Simply infer from source type arguments to target type arguments.
-                    inferFromTypeArguments(source.aliasTypeArguments, target.aliasTypeArguments!, getAliasVariances(source.aliasSymbol));
+                    inferFromTypeArguments(source.aliasTypeArguments, target.aliasTypeArguments!, getAliasVariances(source.aliasSymbol, compareTypesAssignable));
                     return;
                 }
                 if (source === target && source.flags & TypeFlags.UnionOrIntersection) {
@@ -19435,7 +19455,7 @@ namespace ts {
                     (<TypeReference>source).target === (<TypeReference>target).target || isArrayType(source) && isArrayType(target)) &&
                     !((<TypeReference>source).node && (<TypeReference>target).node)) {
                     // If source and target are references to the same generic type, infer from type arguments
-                    inferFromTypeArguments(getTypeArguments(<TypeReference>source), getTypeArguments(<TypeReference>target), getVariances((<TypeReference>source).target));
+                    inferFromTypeArguments(getTypeArguments(<TypeReference>source), getTypeArguments(<TypeReference>target), getVariances((<TypeReference>source).target, compareTypesAssignable));
                 }
                 else if (source.flags & TypeFlags.Index && target.flags & TypeFlags.Index) {
                     contravariant = !contravariant;
@@ -19758,7 +19778,7 @@ namespace ts {
                 if (getObjectFlags(source) & ObjectFlags.Reference && getObjectFlags(target) & ObjectFlags.Reference && (
                     (<TypeReference>source).target === (<TypeReference>target).target || isArrayType(source) && isArrayType(target))) {
                     // If source and target are references to the same generic type, infer from type arguments
-                    inferFromTypeArguments(getTypeArguments(<TypeReference>source), getTypeArguments(<TypeReference>target), getVariances((<TypeReference>source).target));
+                    inferFromTypeArguments(getTypeArguments(<TypeReference>source), getTypeArguments(<TypeReference>target), getVariances((<TypeReference>source).target, compareTypesAssignable));
                     return;
                 }
                 if (isGenericMappedType(source) && isGenericMappedType(target)) {
diff --git a/tests/baselines/reference/complexClassStructureNoCrash.js b/tests/baselines/reference/complexClassStructureNoCrash.js
new file mode 100644
index 0000000000000..6b75d91aca977
--- /dev/null
+++ b/tests/baselines/reference/complexClassStructureNoCrash.js
@@ -0,0 +1,438 @@
+//// [complexClassStructureNoCrash.ts]
+const { assign } = Object
+
+export type Name = string
+export type List<T> = ReadonlyArray<T>
+export type Payload<T> = Record<string, unknown>
+
+export type Stage = Raw | Filled | Linked
+export abstract class Raw { protected readonly rawTag = 'Raw' }
+export abstract class Filled extends Raw { protected readonly filledTag = 'Filled' }
+export abstract class Linked extends Filled { protected readonly linkedTag = 'Linked' }
+export type Final = Linked
+
+type Stageable<S extends Stage, C extends Stage, T> = S extends C ? T : T | undefined
+export type Fillable<S extends Stage, T> = Stageable<S, Filled, T>
+export type Linkable<S extends Stage, T> = Stageable<S, Linked, T>
+
+export type Kind = Node['kind']
+export type Category = 'Entity' | 'Module' | 'Sentence' | 'Expression'
+export type NodeOfKind<K extends Kind, S extends Stage> = Extract<Node<S>, { kind: K }>
+export type NodeOfKindOrCategory<Q extends Kind | Category, S extends Stage> =
+  Q extends Kind ? NodeOfKind<Q, S> :
+  never
+
+export type Node<S extends Stage = Final>
+  = Parameter<S>
+  | NamedArgument<S>
+  | Import<S>
+  | Body<S>
+  | Catch<S>
+  | Entity<S>
+  | DescribeMember<S>
+  | ClassMember<S>
+  | Sentence<S>
+
+abstract class $Node<S extends Stage> {
+  readonly stage?: S
+  abstract readonly kind: Kind
+
+  constructor(payload: Record<string, unknown>) {
+    assign(this, payload)
+  }
+ 
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+    return this.kind === kindOrCategory
+  }
+}
+
+export class Parameter<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Parameter'
+}
+
+export class NamedArgument<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'NamedArgument'
+  readonly value!: Expression<S>
+}
+
+export class Import<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Import'
+  readonly entity!: Reference<S>
+}
+
+export class Body<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Body'
+  readonly sentences!: List<Sentence<S>>
+}
+
+export type Entity<S extends Stage = Final>
+  = Package<S>
+  | Program<S>
+  | Test<S>
+  | Describe<S>
+  | Module<S>
+  | Variable<S>
+
+
+export class Package<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Package'
+  readonly imports!: List<Import<S>>
+  readonly members!: List<Entity<S>>
+}
+
+export class Program<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Program'
+  readonly body!: Body<S>
+}
+
+export class Test<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Test'
+  readonly body!: Body<S>
+}
+
+export class Describe<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Describe'
+  readonly members!: List<DescribeMember<S>>
+
+  tests(): List<Test<S>> { return this.members.filter((member): member is Test<S> => member.is('Test')) }
+  methods(): List<Method<S>> { return this.members.filter((member): member is Method<S> => member.is('Method')) }
+  variables(): List<Variable<S>> { return this.members.filter((member): member is Variable<S> => member.is('Variable')) }
+  fixtures(): List<Fixture<S>> { return this.members.filter((member): member is Fixture<S> => member.is('Fixture')) }
+}
+
+export class Variable<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Variable'
+  readonly value!: Fillable<S, Expression<S>>
+
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+    return [this.kind, 'Sentence', 'Entity'].includes(kindOrCategory)
+  }
+}
+
+export type Module<S extends Stage = Final> = Class<S> | Singleton<S> | Mixin<S>
+
+export class Class<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Class'
+  readonly mixins!: List<Reference<S>>
+  readonly members!: List<ClassMember<S>>
+  readonly superclass!: Fillable<S, Reference<S> | null>
+}
+
+export class Singleton<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Singleton'
+  readonly mixins!: List<Reference<S>>
+  readonly members!: List<ObjectMember<S>>
+  readonly superCall!: Fillable<S, {
+    superclass: Reference<S>,
+    args: List<Expression<S>> | List<NamedArgument<S>>
+  }>
+}
+
+export class Mixin<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Mixin'
+  readonly mixins!: List<Reference<S>>
+  readonly members!: List<ObjectMember<S>>
+}
+
+export type ObjectMember<S extends Stage = Final> = Field<S> | Method<S>
+export type ClassMember<S extends Stage = Final> = Constructor<S> | ObjectMember<S>
+export type DescribeMember<S extends Stage = Final> = Variable<S> | Fixture<S> | Test<S> | Method<S>
+
+export class Field<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Field'
+  readonly value!: Fillable<S, Expression<S>>
+}
+
+export class Method<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Method'
+  readonly parameters!: List<Parameter<S>>
+  readonly body?: Body<S>
+}
+
+export class Constructor<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Constructor'
+  readonly parameters!: List<Parameter<S>>
+  readonly body!: Body<S>
+  readonly baseCall?: { callsSuper: boolean, args: List<Expression<S>> }
+}
+
+export class Fixture<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Fixture'
+  readonly body!: Body<S>
+}
+
+export type Sentence<S extends Stage = Final> = Variable<S> | Return<S> | Assignment<S> | Expression<S>
+
+export class Return<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Return'
+  readonly value?: Expression<S>
+}
+
+export class Assignment<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Assignment'
+  readonly variable!: Reference<S>
+  readonly value!: Expression<S>
+}
+
+export type Expression<S extends Stage = Final>
+  = Reference<S>
+  | Self<S>
+  | Send<S>
+  | Super<S>
+  | New<S>
+  | If<S>
+  | Throw<S>
+  | Try<S>
+
+abstract class $Expression<S extends Stage> extends $Node<S> {
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+    return kindOrCategory === 'Expression' || super.is(kindOrCategory)
+  }
+}
+
+export class Reference<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Reference'
+  readonly name!: Name
+}
+
+export class Self<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Self'
+}
+
+export class Send<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Send'
+  readonly receiver!: Expression<S>
+  readonly message!: Name
+  readonly args!: List<Expression<S>>
+}
+
+export class Super<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Super'
+  readonly args!: List<Expression<S>>
+}
+
+export class New<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'New'
+  readonly instantiated!: Reference<S>
+  readonly args!: List<Expression<S>> | List<NamedArgument<S>>
+}
+
+export class If<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'If'
+  readonly thenBody!: Body<S>
+  readonly elseBody!: Fillable<S, Body<S>>
+}
+
+export class Throw<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Throw'
+}
+
+export class Try<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Try'
+}
+
+export class Catch<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Catch'
+}
+
+//// [complexClassStructureNoCrash.js]
+const { assign } = Object;
+export class Raw {
+    constructor() {
+        this.rawTag = 'Raw';
+    }
+}
+export class Filled extends Raw {
+    constructor() {
+        super(...arguments);
+        this.filledTag = 'Filled';
+    }
+}
+export class Linked extends Filled {
+    constructor() {
+        super(...arguments);
+        this.linkedTag = 'Linked';
+    }
+}
+class $Node {
+    constructor(payload) {
+        assign(this, payload);
+    }
+    is(kindOrCategory) {
+        return this.kind === kindOrCategory;
+    }
+}
+export class Parameter extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Parameter';
+    }
+}
+export class NamedArgument extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'NamedArgument';
+    }
+}
+export class Import extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Import';
+    }
+}
+export class Body extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Body';
+    }
+}
+export class Package extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Package';
+    }
+}
+export class Program extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Program';
+    }
+}
+export class Test extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Test';
+    }
+}
+export class Describe extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Describe';
+    }
+    tests() { return this.members.filter((member) => member.is('Test')); }
+    methods() { return this.members.filter((member) => member.is('Method')); }
+    variables() { return this.members.filter((member) => member.is('Variable')); }
+    fixtures() { return this.members.filter((member) => member.is('Fixture')); }
+}
+export class Variable extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Variable';
+    }
+    is(kindOrCategory) {
+        return [this.kind, 'Sentence', 'Entity'].includes(kindOrCategory);
+    }
+}
+export class Class extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Class';
+    }
+}
+export class Singleton extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Singleton';
+    }
+}
+export class Mixin extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Mixin';
+    }
+}
+export class Field extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Field';
+    }
+}
+export class Method extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Method';
+    }
+}
+export class Constructor extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Constructor';
+    }
+}
+export class Fixture extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Fixture';
+    }
+}
+export class Return extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Return';
+    }
+}
+export class Assignment extends $Node {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Assignment';
+    }
+}
+class $Expression extends $Node {
+    is(kindOrCategory) {
+        return kindOrCategory === 'Expression' || super.is(kindOrCategory);
+    }
+}
+export class Reference extends $Expression {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Reference';
+    }
+}
+export class Self extends $Expression {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Self';
+    }
+}
+export class Send extends $Expression {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Send';
+    }
+}
+export class Super extends $Expression {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Super';
+    }
+}
+export class New extends $Expression {
+    constructor() {
+        super(...arguments);
+        this.kind = 'New';
+    }
+}
+export class If extends $Expression {
+    constructor() {
+        super(...arguments);
+        this.kind = 'If';
+    }
+}
+export class Throw extends $Expression {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Throw';
+    }
+}
+export class Try extends $Expression {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Try';
+    }
+}
+export class Catch extends $Expression {
+    constructor() {
+        super(...arguments);
+        this.kind = 'Catch';
+    }
+}
diff --git a/tests/baselines/reference/complexClassStructureNoCrash.symbols b/tests/baselines/reference/complexClassStructureNoCrash.symbols
new file mode 100644
index 0000000000000..252e22f96f497
--- /dev/null
+++ b/tests/baselines/reference/complexClassStructureNoCrash.symbols
@@ -0,0 +1,989 @@
+=== tests/cases/compiler/complexClassStructureNoCrash.ts ===
+const { assign } = Object
+>assign : Symbol(assign, Decl(complexClassStructureNoCrash.ts, 0, 7))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+export type Name = string
+>Name : Symbol(Name, Decl(complexClassStructureNoCrash.ts, 0, 25))
+
+export type List<T> = ReadonlyArray<T>
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>T : Symbol(T, Decl(complexClassStructureNoCrash.ts, 3, 17))
+>ReadonlyArray : Symbol(ReadonlyArray, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2016.array.include.d.ts, --, --), Decl(lib.es2019.array.d.ts, --, --))
+>T : Symbol(T, Decl(complexClassStructureNoCrash.ts, 3, 17))
+
+export type Payload<T> = Record<string, unknown>
+>Payload : Symbol(Payload, Decl(complexClassStructureNoCrash.ts, 3, 38))
+>T : Symbol(T, Decl(complexClassStructureNoCrash.ts, 4, 20))
+>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
+
+export type Stage = Raw | Filled | Linked
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Raw : Symbol(Raw, Decl(complexClassStructureNoCrash.ts, 6, 41))
+>Filled : Symbol(Filled, Decl(complexClassStructureNoCrash.ts, 7, 63))
+>Linked : Symbol(Linked, Decl(complexClassStructureNoCrash.ts, 8, 84))
+
+export abstract class Raw { protected readonly rawTag = 'Raw' }
+>Raw : Symbol(Raw, Decl(complexClassStructureNoCrash.ts, 6, 41))
+>rawTag : Symbol(Raw.rawTag, Decl(complexClassStructureNoCrash.ts, 7, 27))
+
+export abstract class Filled extends Raw { protected readonly filledTag = 'Filled' }
+>Filled : Symbol(Filled, Decl(complexClassStructureNoCrash.ts, 7, 63))
+>Raw : Symbol(Raw, Decl(complexClassStructureNoCrash.ts, 6, 41))
+>filledTag : Symbol(Filled.filledTag, Decl(complexClassStructureNoCrash.ts, 8, 42))
+
+export abstract class Linked extends Filled { protected readonly linkedTag = 'Linked' }
+>Linked : Symbol(Linked, Decl(complexClassStructureNoCrash.ts, 8, 84))
+>Filled : Symbol(Filled, Decl(complexClassStructureNoCrash.ts, 7, 63))
+>linkedTag : Symbol(Linked.linkedTag, Decl(complexClassStructureNoCrash.ts, 9, 45))
+
+export type Final = Linked
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>Linked : Symbol(Linked, Decl(complexClassStructureNoCrash.ts, 8, 84))
+
+type Stageable<S extends Stage, C extends Stage, T> = S extends C ? T : T | undefined
+>Stageable : Symbol(Stageable, Decl(complexClassStructureNoCrash.ts, 10, 26))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 12, 15))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>C : Symbol(C, Decl(complexClassStructureNoCrash.ts, 12, 31))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>T : Symbol(T, Decl(complexClassStructureNoCrash.ts, 12, 48))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 12, 15))
+>C : Symbol(C, Decl(complexClassStructureNoCrash.ts, 12, 31))
+>T : Symbol(T, Decl(complexClassStructureNoCrash.ts, 12, 48))
+>T : Symbol(T, Decl(complexClassStructureNoCrash.ts, 12, 48))
+
+export type Fillable<S extends Stage, T> = Stageable<S, Filled, T>
+>Fillable : Symbol(Fillable, Decl(complexClassStructureNoCrash.ts, 12, 85))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 13, 21))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>T : Symbol(T, Decl(complexClassStructureNoCrash.ts, 13, 37))
+>Stageable : Symbol(Stageable, Decl(complexClassStructureNoCrash.ts, 10, 26))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 13, 21))
+>Filled : Symbol(Filled, Decl(complexClassStructureNoCrash.ts, 7, 63))
+>T : Symbol(T, Decl(complexClassStructureNoCrash.ts, 13, 37))
+
+export type Linkable<S extends Stage, T> = Stageable<S, Linked, T>
+>Linkable : Symbol(Linkable, Decl(complexClassStructureNoCrash.ts, 13, 66))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 14, 21))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>T : Symbol(T, Decl(complexClassStructureNoCrash.ts, 14, 37))
+>Stageable : Symbol(Stageable, Decl(complexClassStructureNoCrash.ts, 10, 26))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 14, 21))
+>Linked : Symbol(Linked, Decl(complexClassStructureNoCrash.ts, 8, 84))
+>T : Symbol(T, Decl(complexClassStructureNoCrash.ts, 14, 37))
+
+export type Kind = Node['kind']
+>Kind : Symbol(Kind, Decl(complexClassStructureNoCrash.ts, 14, 66))
+>Node : Symbol(Node, Decl(complexClassStructureNoCrash.ts, 21, 7))
+
+export type Category = 'Entity' | 'Module' | 'Sentence' | 'Expression'
+>Category : Symbol(Category, Decl(complexClassStructureNoCrash.ts, 16, 31))
+
+export type NodeOfKind<K extends Kind, S extends Stage> = Extract<Node<S>, { kind: K }>
+>NodeOfKind : Symbol(NodeOfKind, Decl(complexClassStructureNoCrash.ts, 17, 70))
+>K : Symbol(K, Decl(complexClassStructureNoCrash.ts, 18, 23))
+>Kind : Symbol(Kind, Decl(complexClassStructureNoCrash.ts, 14, 66))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 18, 38))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Extract : Symbol(Extract, Decl(lib.es5.d.ts, --, --))
+>Node : Symbol(Node, Decl(complexClassStructureNoCrash.ts, 21, 7))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 18, 38))
+>kind : Symbol(kind, Decl(complexClassStructureNoCrash.ts, 18, 76))
+>K : Symbol(K, Decl(complexClassStructureNoCrash.ts, 18, 23))
+
+export type NodeOfKindOrCategory<Q extends Kind | Category, S extends Stage> =
+>NodeOfKindOrCategory : Symbol(NodeOfKindOrCategory, Decl(complexClassStructureNoCrash.ts, 18, 87))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 19, 33))
+>Kind : Symbol(Kind, Decl(complexClassStructureNoCrash.ts, 14, 66))
+>Category : Symbol(Category, Decl(complexClassStructureNoCrash.ts, 16, 31))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 19, 59))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+
+  Q extends Kind ? NodeOfKind<Q, S> :
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 19, 33))
+>Kind : Symbol(Kind, Decl(complexClassStructureNoCrash.ts, 14, 66))
+>NodeOfKind : Symbol(NodeOfKind, Decl(complexClassStructureNoCrash.ts, 17, 70))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 19, 33))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 19, 59))
+
+  never
+
+export type Node<S extends Stage = Final>
+>Node : Symbol(Node, Decl(complexClassStructureNoCrash.ts, 21, 7))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 23, 17))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+
+  = Parameter<S>
+>Parameter : Symbol(Parameter, Decl(complexClassStructureNoCrash.ts, 45, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 23, 17))
+
+  | NamedArgument<S>
+>NamedArgument : Symbol(NamedArgument, Decl(complexClassStructureNoCrash.ts, 49, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 23, 17))
+
+  | Import<S>
+>Import : Symbol(Import, Decl(complexClassStructureNoCrash.ts, 54, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 23, 17))
+
+  | Body<S>
+>Body : Symbol(Body, Decl(complexClassStructureNoCrash.ts, 59, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 23, 17))
+
+  | Catch<S>
+>Catch : Symbol(Catch, Decl(complexClassStructureNoCrash.ts, 230, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 23, 17))
+
+  | Entity<S>
+>Entity : Symbol(Entity, Decl(complexClassStructureNoCrash.ts, 64, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 23, 17))
+
+  | DescribeMember<S>
+>DescribeMember : Symbol(DescribeMember, Decl(complexClassStructureNoCrash.ts, 136, 83))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 23, 17))
+
+  | ClassMember<S>
+>ClassMember : Symbol(ClassMember, Decl(complexClassStructureNoCrash.ts, 135, 72))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 23, 17))
+
+  | Sentence<S>
+>Sentence : Symbol(Sentence, Decl(complexClassStructureNoCrash.ts, 160, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 23, 17))
+
+abstract class $Node<S extends Stage> {
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 34, 21))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+
+  readonly stage?: S
+>stage : Symbol($Node.stage, Decl(complexClassStructureNoCrash.ts, 34, 39))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 34, 21))
+
+  abstract readonly kind: Kind
+>kind : Symbol($Node.kind, Decl(complexClassStructureNoCrash.ts, 35, 20))
+>Kind : Symbol(Kind, Decl(complexClassStructureNoCrash.ts, 14, 66))
+
+  constructor(payload: Record<string, unknown>) {
+>payload : Symbol(payload, Decl(complexClassStructureNoCrash.ts, 38, 14))
+>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
+
+    assign(this, payload)
+>assign : Symbol(assign, Decl(complexClassStructureNoCrash.ts, 0, 7))
+>this : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>payload : Symbol(payload, Decl(complexClassStructureNoCrash.ts, 38, 14))
+  }
+ 
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+>is : Symbol($Node.is, Decl(complexClassStructureNoCrash.ts, 40, 3))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 42, 5))
+>Kind : Symbol(Kind, Decl(complexClassStructureNoCrash.ts, 14, 66))
+>Category : Symbol(Category, Decl(complexClassStructureNoCrash.ts, 16, 31))
+>kindOrCategory : Symbol(kindOrCategory, Decl(complexClassStructureNoCrash.ts, 42, 32))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 42, 5))
+>NodeOfKindOrCategory : Symbol(NodeOfKindOrCategory, Decl(complexClassStructureNoCrash.ts, 18, 87))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 42, 5))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 34, 21))
+
+    return this.kind === kindOrCategory
+>this.kind : Symbol($Node.kind, Decl(complexClassStructureNoCrash.ts, 35, 20))
+>this : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>kind : Symbol($Node.kind, Decl(complexClassStructureNoCrash.ts, 35, 20))
+>kindOrCategory : Symbol(kindOrCategory, Decl(complexClassStructureNoCrash.ts, 42, 32))
+  }
+}
+
+export class Parameter<S extends Stage = Final> extends $Node<S> {
+>Parameter : Symbol(Parameter, Decl(complexClassStructureNoCrash.ts, 45, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 47, 23))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 47, 23))
+
+  readonly kind = 'Parameter'
+>kind : Symbol(Parameter.kind, Decl(complexClassStructureNoCrash.ts, 47, 66))
+}
+
+export class NamedArgument<S extends Stage = Final> extends $Node<S> {
+>NamedArgument : Symbol(NamedArgument, Decl(complexClassStructureNoCrash.ts, 49, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 51, 27))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 51, 27))
+
+  readonly kind = 'NamedArgument'
+>kind : Symbol(NamedArgument.kind, Decl(complexClassStructureNoCrash.ts, 51, 70))
+
+  readonly value!: Expression<S>
+>value : Symbol(NamedArgument.value, Decl(complexClassStructureNoCrash.ts, 52, 33))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 51, 27))
+}
+
+export class Import<S extends Stage = Final> extends $Node<S> {
+>Import : Symbol(Import, Decl(complexClassStructureNoCrash.ts, 54, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 56, 20))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 56, 20))
+
+  readonly kind = 'Import'
+>kind : Symbol(Import.kind, Decl(complexClassStructureNoCrash.ts, 56, 63))
+
+  readonly entity!: Reference<S>
+>entity : Symbol(Import.entity, Decl(complexClassStructureNoCrash.ts, 57, 26))
+>Reference : Symbol(Reference, Decl(complexClassStructureNoCrash.ts, 189, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 56, 20))
+}
+
+export class Body<S extends Stage = Final> extends $Node<S> {
+>Body : Symbol(Body, Decl(complexClassStructureNoCrash.ts, 59, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 61, 18))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 61, 18))
+
+  readonly kind = 'Body'
+>kind : Symbol(Body.kind, Decl(complexClassStructureNoCrash.ts, 61, 61))
+
+  readonly sentences!: List<Sentence<S>>
+>sentences : Symbol(Body.sentences, Decl(complexClassStructureNoCrash.ts, 62, 24))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Sentence : Symbol(Sentence, Decl(complexClassStructureNoCrash.ts, 160, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 61, 18))
+}
+
+export type Entity<S extends Stage = Final>
+>Entity : Symbol(Entity, Decl(complexClassStructureNoCrash.ts, 64, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 66, 19))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+
+  = Package<S>
+>Package : Symbol(Package, Decl(complexClassStructureNoCrash.ts, 72, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 66, 19))
+
+  | Program<S>
+>Program : Symbol(Program, Decl(complexClassStructureNoCrash.ts, 79, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 66, 19))
+
+  | Test<S>
+>Test : Symbol(Test, Decl(complexClassStructureNoCrash.ts, 84, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 66, 19))
+
+  | Describe<S>
+>Describe : Symbol(Describe, Decl(complexClassStructureNoCrash.ts, 89, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 66, 19))
+
+  | Module<S>
+>Module : Symbol(Module, Decl(complexClassStructureNoCrash.ts, 108, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 66, 19))
+
+  | Variable<S>
+>Variable : Symbol(Variable, Decl(complexClassStructureNoCrash.ts, 99, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 66, 19))
+
+
+export class Package<S extends Stage = Final> extends $Node<S> {
+>Package : Symbol(Package, Decl(complexClassStructureNoCrash.ts, 72, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 75, 21))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 75, 21))
+
+  readonly kind = 'Package'
+>kind : Symbol(Package.kind, Decl(complexClassStructureNoCrash.ts, 75, 64))
+
+  readonly imports!: List<Import<S>>
+>imports : Symbol(Package.imports, Decl(complexClassStructureNoCrash.ts, 76, 27))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Import : Symbol(Import, Decl(complexClassStructureNoCrash.ts, 54, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 75, 21))
+
+  readonly members!: List<Entity<S>>
+>members : Symbol(Package.members, Decl(complexClassStructureNoCrash.ts, 77, 36))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Entity : Symbol(Entity, Decl(complexClassStructureNoCrash.ts, 64, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 75, 21))
+}
+
+export class Program<S extends Stage = Final> extends $Node<S> {
+>Program : Symbol(Program, Decl(complexClassStructureNoCrash.ts, 79, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 81, 21))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 81, 21))
+
+  readonly kind = 'Program'
+>kind : Symbol(Program.kind, Decl(complexClassStructureNoCrash.ts, 81, 64))
+
+  readonly body!: Body<S>
+>body : Symbol(Program.body, Decl(complexClassStructureNoCrash.ts, 82, 27))
+>Body : Symbol(Body, Decl(complexClassStructureNoCrash.ts, 59, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 81, 21))
+}
+
+export class Test<S extends Stage = Final> extends $Node<S> {
+>Test : Symbol(Test, Decl(complexClassStructureNoCrash.ts, 84, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 86, 18))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 86, 18))
+
+  readonly kind = 'Test'
+>kind : Symbol(Test.kind, Decl(complexClassStructureNoCrash.ts, 86, 61))
+
+  readonly body!: Body<S>
+>body : Symbol(Test.body, Decl(complexClassStructureNoCrash.ts, 87, 24))
+>Body : Symbol(Body, Decl(complexClassStructureNoCrash.ts, 59, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 86, 18))
+}
+
+export class Describe<S extends Stage = Final> extends $Node<S> {
+>Describe : Symbol(Describe, Decl(complexClassStructureNoCrash.ts, 89, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+
+  readonly kind = 'Describe'
+>kind : Symbol(Describe.kind, Decl(complexClassStructureNoCrash.ts, 91, 65))
+
+  readonly members!: List<DescribeMember<S>>
+>members : Symbol(Describe.members, Decl(complexClassStructureNoCrash.ts, 92, 28))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>DescribeMember : Symbol(DescribeMember, Decl(complexClassStructureNoCrash.ts, 136, 83))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+
+  tests(): List<Test<S>> { return this.members.filter((member): member is Test<S> => member.is('Test')) }
+>tests : Symbol(Describe.tests, Decl(complexClassStructureNoCrash.ts, 93, 44))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Test : Symbol(Test, Decl(complexClassStructureNoCrash.ts, 84, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+>this.members.filter : Symbol(ReadonlyArray.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>this.members : Symbol(Describe.members, Decl(complexClassStructureNoCrash.ts, 92, 28))
+>this : Symbol(Describe, Decl(complexClassStructureNoCrash.ts, 89, 1))
+>members : Symbol(Describe.members, Decl(complexClassStructureNoCrash.ts, 92, 28))
+>filter : Symbol(ReadonlyArray.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 95, 55))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 95, 55))
+>Test : Symbol(Test, Decl(complexClassStructureNoCrash.ts, 84, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+>member.is : Symbol(is, Decl(complexClassStructureNoCrash.ts, 103, 45), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 95, 55))
+>is : Symbol(is, Decl(complexClassStructureNoCrash.ts, 103, 45), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3))
+
+  methods(): List<Method<S>> { return this.members.filter((member): member is Method<S> => member.is('Method')) }
+>methods : Symbol(Describe.methods, Decl(complexClassStructureNoCrash.ts, 95, 105))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Method : Symbol(Method, Decl(complexClassStructureNoCrash.ts, 142, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+>this.members.filter : Symbol(ReadonlyArray.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>this.members : Symbol(Describe.members, Decl(complexClassStructureNoCrash.ts, 92, 28))
+>this : Symbol(Describe, Decl(complexClassStructureNoCrash.ts, 89, 1))
+>members : Symbol(Describe.members, Decl(complexClassStructureNoCrash.ts, 92, 28))
+>filter : Symbol(ReadonlyArray.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 96, 59))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 96, 59))
+>Method : Symbol(Method, Decl(complexClassStructureNoCrash.ts, 142, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+>member.is : Symbol(is, Decl(complexClassStructureNoCrash.ts, 103, 45), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 96, 59))
+>is : Symbol(is, Decl(complexClassStructureNoCrash.ts, 103, 45), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3))
+
+  variables(): List<Variable<S>> { return this.members.filter((member): member is Variable<S> => member.is('Variable')) }
+>variables : Symbol(Describe.variables, Decl(complexClassStructureNoCrash.ts, 96, 113))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Variable : Symbol(Variable, Decl(complexClassStructureNoCrash.ts, 99, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+>this.members.filter : Symbol(ReadonlyArray.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>this.members : Symbol(Describe.members, Decl(complexClassStructureNoCrash.ts, 92, 28))
+>this : Symbol(Describe, Decl(complexClassStructureNoCrash.ts, 89, 1))
+>members : Symbol(Describe.members, Decl(complexClassStructureNoCrash.ts, 92, 28))
+>filter : Symbol(ReadonlyArray.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 97, 63))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 97, 63))
+>Variable : Symbol(Variable, Decl(complexClassStructureNoCrash.ts, 99, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+>member.is : Symbol(is, Decl(complexClassStructureNoCrash.ts, 103, 45), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 97, 63))
+>is : Symbol(is, Decl(complexClassStructureNoCrash.ts, 103, 45), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3))
+
+  fixtures(): List<Fixture<S>> { return this.members.filter((member): member is Fixture<S> => member.is('Fixture')) }
+>fixtures : Symbol(Describe.fixtures, Decl(complexClassStructureNoCrash.ts, 97, 121))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Fixture : Symbol(Fixture, Decl(complexClassStructureNoCrash.ts, 155, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+>this.members.filter : Symbol(ReadonlyArray.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>this.members : Symbol(Describe.members, Decl(complexClassStructureNoCrash.ts, 92, 28))
+>this : Symbol(Describe, Decl(complexClassStructureNoCrash.ts, 89, 1))
+>members : Symbol(Describe.members, Decl(complexClassStructureNoCrash.ts, 92, 28))
+>filter : Symbol(ReadonlyArray.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 98, 61))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 98, 61))
+>Fixture : Symbol(Fixture, Decl(complexClassStructureNoCrash.ts, 155, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 91, 22))
+>member.is : Symbol(is, Decl(complexClassStructureNoCrash.ts, 103, 45), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3))
+>member : Symbol(member, Decl(complexClassStructureNoCrash.ts, 98, 61))
+>is : Symbol(is, Decl(complexClassStructureNoCrash.ts, 103, 45), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3), Decl(complexClassStructureNoCrash.ts, 40, 3))
+}
+
+export class Variable<S extends Stage = Final> extends $Node<S> {
+>Variable : Symbol(Variable, Decl(complexClassStructureNoCrash.ts, 99, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 101, 22))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 101, 22))
+
+  readonly kind = 'Variable'
+>kind : Symbol(Variable.kind, Decl(complexClassStructureNoCrash.ts, 101, 65))
+
+  readonly value!: Fillable<S, Expression<S>>
+>value : Symbol(Variable.value, Decl(complexClassStructureNoCrash.ts, 102, 28))
+>Fillable : Symbol(Fillable, Decl(complexClassStructureNoCrash.ts, 12, 85))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 101, 22))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 101, 22))
+
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+>is : Symbol(Variable.is, Decl(complexClassStructureNoCrash.ts, 103, 45))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 105, 5))
+>Kind : Symbol(Kind, Decl(complexClassStructureNoCrash.ts, 14, 66))
+>Category : Symbol(Category, Decl(complexClassStructureNoCrash.ts, 16, 31))
+>kindOrCategory : Symbol(kindOrCategory, Decl(complexClassStructureNoCrash.ts, 105, 32))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 105, 5))
+>NodeOfKindOrCategory : Symbol(NodeOfKindOrCategory, Decl(complexClassStructureNoCrash.ts, 18, 87))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 105, 5))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 101, 22))
+
+    return [this.kind, 'Sentence', 'Entity'].includes(kindOrCategory)
+>[this.kind, 'Sentence', 'Entity'].includes : Symbol(Array.includes, Decl(lib.es2016.array.include.d.ts, --, --))
+>this.kind : Symbol(Variable.kind, Decl(complexClassStructureNoCrash.ts, 101, 65))
+>this : Symbol(Variable, Decl(complexClassStructureNoCrash.ts, 99, 1))
+>kind : Symbol(Variable.kind, Decl(complexClassStructureNoCrash.ts, 101, 65))
+>includes : Symbol(Array.includes, Decl(lib.es2016.array.include.d.ts, --, --))
+>kindOrCategory : Symbol(kindOrCategory, Decl(complexClassStructureNoCrash.ts, 105, 32))
+  }
+}
+
+export type Module<S extends Stage = Final> = Class<S> | Singleton<S> | Mixin<S>
+>Module : Symbol(Module, Decl(complexClassStructureNoCrash.ts, 108, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 110, 19))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>Class : Symbol(Class, Decl(complexClassStructureNoCrash.ts, 110, 80))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 110, 19))
+>Singleton : Symbol(Singleton, Decl(complexClassStructureNoCrash.ts, 117, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 110, 19))
+>Mixin : Symbol(Mixin, Decl(complexClassStructureNoCrash.ts, 127, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 110, 19))
+
+export class Class<S extends Stage = Final> extends $Node<S> {
+>Class : Symbol(Class, Decl(complexClassStructureNoCrash.ts, 110, 80))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 112, 19))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 112, 19))
+
+  readonly kind = 'Class'
+>kind : Symbol(Class.kind, Decl(complexClassStructureNoCrash.ts, 112, 62))
+
+  readonly mixins!: List<Reference<S>>
+>mixins : Symbol(Class.mixins, Decl(complexClassStructureNoCrash.ts, 113, 25))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Reference : Symbol(Reference, Decl(complexClassStructureNoCrash.ts, 189, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 112, 19))
+
+  readonly members!: List<ClassMember<S>>
+>members : Symbol(Class.members, Decl(complexClassStructureNoCrash.ts, 114, 38))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>ClassMember : Symbol(ClassMember, Decl(complexClassStructureNoCrash.ts, 135, 72))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 112, 19))
+
+  readonly superclass!: Fillable<S, Reference<S> | null>
+>superclass : Symbol(Class.superclass, Decl(complexClassStructureNoCrash.ts, 115, 41))
+>Fillable : Symbol(Fillable, Decl(complexClassStructureNoCrash.ts, 12, 85))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 112, 19))
+>Reference : Symbol(Reference, Decl(complexClassStructureNoCrash.ts, 189, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 112, 19))
+}
+
+export class Singleton<S extends Stage = Final> extends $Node<S> {
+>Singleton : Symbol(Singleton, Decl(complexClassStructureNoCrash.ts, 117, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 119, 23))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 119, 23))
+
+  readonly kind = 'Singleton'
+>kind : Symbol(Singleton.kind, Decl(complexClassStructureNoCrash.ts, 119, 66))
+
+  readonly mixins!: List<Reference<S>>
+>mixins : Symbol(Singleton.mixins, Decl(complexClassStructureNoCrash.ts, 120, 29))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Reference : Symbol(Reference, Decl(complexClassStructureNoCrash.ts, 189, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 119, 23))
+
+  readonly members!: List<ObjectMember<S>>
+>members : Symbol(Singleton.members, Decl(complexClassStructureNoCrash.ts, 121, 38))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>ObjectMember : Symbol(ObjectMember, Decl(complexClassStructureNoCrash.ts, 133, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 119, 23))
+
+  readonly superCall!: Fillable<S, {
+>superCall : Symbol(Singleton.superCall, Decl(complexClassStructureNoCrash.ts, 122, 42))
+>Fillable : Symbol(Fillable, Decl(complexClassStructureNoCrash.ts, 12, 85))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 119, 23))
+
+    superclass: Reference<S>,
+>superclass : Symbol(superclass, Decl(complexClassStructureNoCrash.ts, 123, 36))
+>Reference : Symbol(Reference, Decl(complexClassStructureNoCrash.ts, 189, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 119, 23))
+
+    args: List<Expression<S>> | List<NamedArgument<S>>
+>args : Symbol(args, Decl(complexClassStructureNoCrash.ts, 124, 29))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 119, 23))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>NamedArgument : Symbol(NamedArgument, Decl(complexClassStructureNoCrash.ts, 49, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 119, 23))
+
+  }>
+}
+
+export class Mixin<S extends Stage = Final> extends $Node<S> {
+>Mixin : Symbol(Mixin, Decl(complexClassStructureNoCrash.ts, 127, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 129, 19))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 129, 19))
+
+  readonly kind = 'Mixin'
+>kind : Symbol(Mixin.kind, Decl(complexClassStructureNoCrash.ts, 129, 62))
+
+  readonly mixins!: List<Reference<S>>
+>mixins : Symbol(Mixin.mixins, Decl(complexClassStructureNoCrash.ts, 130, 25))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Reference : Symbol(Reference, Decl(complexClassStructureNoCrash.ts, 189, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 129, 19))
+
+  readonly members!: List<ObjectMember<S>>
+>members : Symbol(Mixin.members, Decl(complexClassStructureNoCrash.ts, 131, 38))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>ObjectMember : Symbol(ObjectMember, Decl(complexClassStructureNoCrash.ts, 133, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 129, 19))
+}
+
+export type ObjectMember<S extends Stage = Final> = Field<S> | Method<S>
+>ObjectMember : Symbol(ObjectMember, Decl(complexClassStructureNoCrash.ts, 133, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 135, 25))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>Field : Symbol(Field, Decl(complexClassStructureNoCrash.ts, 137, 100))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 135, 25))
+>Method : Symbol(Method, Decl(complexClassStructureNoCrash.ts, 142, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 135, 25))
+
+export type ClassMember<S extends Stage = Final> = Constructor<S> | ObjectMember<S>
+>ClassMember : Symbol(ClassMember, Decl(complexClassStructureNoCrash.ts, 135, 72))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 136, 24))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>Constructor : Symbol(Constructor, Decl(complexClassStructureNoCrash.ts, 148, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 136, 24))
+>ObjectMember : Symbol(ObjectMember, Decl(complexClassStructureNoCrash.ts, 133, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 136, 24))
+
+export type DescribeMember<S extends Stage = Final> = Variable<S> | Fixture<S> | Test<S> | Method<S>
+>DescribeMember : Symbol(DescribeMember, Decl(complexClassStructureNoCrash.ts, 136, 83))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 137, 27))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>Variable : Symbol(Variable, Decl(complexClassStructureNoCrash.ts, 99, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 137, 27))
+>Fixture : Symbol(Fixture, Decl(complexClassStructureNoCrash.ts, 155, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 137, 27))
+>Test : Symbol(Test, Decl(complexClassStructureNoCrash.ts, 84, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 137, 27))
+>Method : Symbol(Method, Decl(complexClassStructureNoCrash.ts, 142, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 137, 27))
+
+export class Field<S extends Stage = Final> extends $Node<S> {
+>Field : Symbol(Field, Decl(complexClassStructureNoCrash.ts, 137, 100))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 139, 19))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 139, 19))
+
+  readonly kind = 'Field'
+>kind : Symbol(Field.kind, Decl(complexClassStructureNoCrash.ts, 139, 62))
+
+  readonly value!: Fillable<S, Expression<S>>
+>value : Symbol(Field.value, Decl(complexClassStructureNoCrash.ts, 140, 25))
+>Fillable : Symbol(Fillable, Decl(complexClassStructureNoCrash.ts, 12, 85))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 139, 19))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 139, 19))
+}
+
+export class Method<S extends Stage = Final> extends $Node<S> {
+>Method : Symbol(Method, Decl(complexClassStructureNoCrash.ts, 142, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 144, 20))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 144, 20))
+
+  readonly kind = 'Method'
+>kind : Symbol(Method.kind, Decl(complexClassStructureNoCrash.ts, 144, 63))
+
+  readonly parameters!: List<Parameter<S>>
+>parameters : Symbol(Method.parameters, Decl(complexClassStructureNoCrash.ts, 145, 26))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Parameter : Symbol(Parameter, Decl(complexClassStructureNoCrash.ts, 45, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 144, 20))
+
+  readonly body?: Body<S>
+>body : Symbol(Method.body, Decl(complexClassStructureNoCrash.ts, 146, 42))
+>Body : Symbol(Body, Decl(complexClassStructureNoCrash.ts, 59, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 144, 20))
+}
+
+export class Constructor<S extends Stage = Final> extends $Node<S> {
+>Constructor : Symbol(Constructor, Decl(complexClassStructureNoCrash.ts, 148, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 150, 25))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 150, 25))
+
+  readonly kind = 'Constructor'
+>kind : Symbol(Constructor.kind, Decl(complexClassStructureNoCrash.ts, 150, 68))
+
+  readonly parameters!: List<Parameter<S>>
+>parameters : Symbol(Constructor.parameters, Decl(complexClassStructureNoCrash.ts, 151, 31))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Parameter : Symbol(Parameter, Decl(complexClassStructureNoCrash.ts, 45, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 150, 25))
+
+  readonly body!: Body<S>
+>body : Symbol(Constructor.body, Decl(complexClassStructureNoCrash.ts, 152, 42))
+>Body : Symbol(Body, Decl(complexClassStructureNoCrash.ts, 59, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 150, 25))
+
+  readonly baseCall?: { callsSuper: boolean, args: List<Expression<S>> }
+>baseCall : Symbol(Constructor.baseCall, Decl(complexClassStructureNoCrash.ts, 153, 25))
+>callsSuper : Symbol(callsSuper, Decl(complexClassStructureNoCrash.ts, 154, 23))
+>args : Symbol(args, Decl(complexClassStructureNoCrash.ts, 154, 44))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 150, 25))
+}
+
+export class Fixture<S extends Stage = Final> extends $Node<S> {
+>Fixture : Symbol(Fixture, Decl(complexClassStructureNoCrash.ts, 155, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 157, 21))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 157, 21))
+
+  readonly kind = 'Fixture'
+>kind : Symbol(Fixture.kind, Decl(complexClassStructureNoCrash.ts, 157, 64))
+
+  readonly body!: Body<S>
+>body : Symbol(Fixture.body, Decl(complexClassStructureNoCrash.ts, 158, 27))
+>Body : Symbol(Body, Decl(complexClassStructureNoCrash.ts, 59, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 157, 21))
+}
+
+export type Sentence<S extends Stage = Final> = Variable<S> | Return<S> | Assignment<S> | Expression<S>
+>Sentence : Symbol(Sentence, Decl(complexClassStructureNoCrash.ts, 160, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 162, 21))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>Variable : Symbol(Variable, Decl(complexClassStructureNoCrash.ts, 99, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 162, 21))
+>Return : Symbol(Return, Decl(complexClassStructureNoCrash.ts, 162, 103))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 162, 21))
+>Assignment : Symbol(Assignment, Decl(complexClassStructureNoCrash.ts, 167, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 162, 21))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 162, 21))
+
+export class Return<S extends Stage = Final> extends $Node<S> {
+>Return : Symbol(Return, Decl(complexClassStructureNoCrash.ts, 162, 103))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 164, 20))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 164, 20))
+
+  readonly kind = 'Return'
+>kind : Symbol(Return.kind, Decl(complexClassStructureNoCrash.ts, 164, 63))
+
+  readonly value?: Expression<S>
+>value : Symbol(Return.value, Decl(complexClassStructureNoCrash.ts, 165, 26))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 164, 20))
+}
+
+export class Assignment<S extends Stage = Final> extends $Node<S> {
+>Assignment : Symbol(Assignment, Decl(complexClassStructureNoCrash.ts, 167, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 169, 24))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 169, 24))
+
+  readonly kind = 'Assignment'
+>kind : Symbol(Assignment.kind, Decl(complexClassStructureNoCrash.ts, 169, 67))
+
+  readonly variable!: Reference<S>
+>variable : Symbol(Assignment.variable, Decl(complexClassStructureNoCrash.ts, 170, 30))
+>Reference : Symbol(Reference, Decl(complexClassStructureNoCrash.ts, 189, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 169, 24))
+
+  readonly value!: Expression<S>
+>value : Symbol(Assignment.value, Decl(complexClassStructureNoCrash.ts, 171, 34))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 169, 24))
+}
+
+export type Expression<S extends Stage = Final>
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 175, 23))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+
+  = Reference<S>
+>Reference : Symbol(Reference, Decl(complexClassStructureNoCrash.ts, 189, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 175, 23))
+
+  | Self<S>
+>Self : Symbol(Self, Decl(complexClassStructureNoCrash.ts, 194, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 175, 23))
+
+  | Send<S>
+>Send : Symbol(Send, Decl(complexClassStructureNoCrash.ts, 198, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 175, 23))
+
+  | Super<S>
+>Super : Symbol(Super, Decl(complexClassStructureNoCrash.ts, 205, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 175, 23))
+
+  | New<S>
+>New : Symbol(New, Decl(complexClassStructureNoCrash.ts, 210, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 175, 23))
+
+  | If<S>
+>If : Symbol(If, Decl(complexClassStructureNoCrash.ts, 216, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 175, 23))
+
+  | Throw<S>
+>Throw : Symbol(Throw, Decl(complexClassStructureNoCrash.ts, 222, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 175, 23))
+
+  | Try<S>
+>Try : Symbol(Try, Decl(complexClassStructureNoCrash.ts, 226, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 175, 23))
+
+abstract class $Expression<S extends Stage> extends $Node<S> {
+>$Expression : Symbol($Expression, Decl(complexClassStructureNoCrash.ts, 183, 10))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 185, 27))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>$Node : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 185, 27))
+
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+>is : Symbol($Expression.is, Decl(complexClassStructureNoCrash.ts, 185, 62))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 186, 5))
+>Kind : Symbol(Kind, Decl(complexClassStructureNoCrash.ts, 14, 66))
+>Category : Symbol(Category, Decl(complexClassStructureNoCrash.ts, 16, 31))
+>kindOrCategory : Symbol(kindOrCategory, Decl(complexClassStructureNoCrash.ts, 186, 32))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 186, 5))
+>NodeOfKindOrCategory : Symbol(NodeOfKindOrCategory, Decl(complexClassStructureNoCrash.ts, 18, 87))
+>Q : Symbol(Q, Decl(complexClassStructureNoCrash.ts, 186, 5))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 185, 27))
+
+    return kindOrCategory === 'Expression' || super.is(kindOrCategory)
+>kindOrCategory : Symbol(kindOrCategory, Decl(complexClassStructureNoCrash.ts, 186, 32))
+>super.is : Symbol($Node.is, Decl(complexClassStructureNoCrash.ts, 40, 3))
+>super : Symbol($Node, Decl(complexClassStructureNoCrash.ts, 32, 15))
+>is : Symbol($Node.is, Decl(complexClassStructureNoCrash.ts, 40, 3))
+>kindOrCategory : Symbol(kindOrCategory, Decl(complexClassStructureNoCrash.ts, 186, 32))
+  }
+}
+
+export class Reference<S extends Stage = Final> extends $Expression<S> {
+>Reference : Symbol(Reference, Decl(complexClassStructureNoCrash.ts, 189, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 191, 23))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Expression : Symbol($Expression, Decl(complexClassStructureNoCrash.ts, 183, 10))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 191, 23))
+
+  readonly kind = 'Reference'
+>kind : Symbol(Reference.kind, Decl(complexClassStructureNoCrash.ts, 191, 72))
+
+  readonly name!: Name
+>name : Symbol(Reference.name, Decl(complexClassStructureNoCrash.ts, 192, 29))
+>Name : Symbol(Name, Decl(complexClassStructureNoCrash.ts, 0, 25))
+}
+
+export class Self<S extends Stage = Final> extends $Expression<S> {
+>Self : Symbol(Self, Decl(complexClassStructureNoCrash.ts, 194, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 196, 18))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Expression : Symbol($Expression, Decl(complexClassStructureNoCrash.ts, 183, 10))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 196, 18))
+
+  readonly kind = 'Self'
+>kind : Symbol(Self.kind, Decl(complexClassStructureNoCrash.ts, 196, 67))
+}
+
+export class Send<S extends Stage = Final> extends $Expression<S> {
+>Send : Symbol(Send, Decl(complexClassStructureNoCrash.ts, 198, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 200, 18))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Expression : Symbol($Expression, Decl(complexClassStructureNoCrash.ts, 183, 10))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 200, 18))
+
+  readonly kind = 'Send'
+>kind : Symbol(Send.kind, Decl(complexClassStructureNoCrash.ts, 200, 67))
+
+  readonly receiver!: Expression<S>
+>receiver : Symbol(Send.receiver, Decl(complexClassStructureNoCrash.ts, 201, 24))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 200, 18))
+
+  readonly message!: Name
+>message : Symbol(Send.message, Decl(complexClassStructureNoCrash.ts, 202, 35))
+>Name : Symbol(Name, Decl(complexClassStructureNoCrash.ts, 0, 25))
+
+  readonly args!: List<Expression<S>>
+>args : Symbol(Send.args, Decl(complexClassStructureNoCrash.ts, 203, 25))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 200, 18))
+}
+
+export class Super<S extends Stage = Final> extends $Expression<S> {
+>Super : Symbol(Super, Decl(complexClassStructureNoCrash.ts, 205, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 207, 19))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Expression : Symbol($Expression, Decl(complexClassStructureNoCrash.ts, 183, 10))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 207, 19))
+
+  readonly kind = 'Super'
+>kind : Symbol(Super.kind, Decl(complexClassStructureNoCrash.ts, 207, 68))
+
+  readonly args!: List<Expression<S>>
+>args : Symbol(Super.args, Decl(complexClassStructureNoCrash.ts, 208, 25))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 207, 19))
+}
+
+export class New<S extends Stage = Final> extends $Expression<S> {
+>New : Symbol(New, Decl(complexClassStructureNoCrash.ts, 210, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 212, 17))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Expression : Symbol($Expression, Decl(complexClassStructureNoCrash.ts, 183, 10))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 212, 17))
+
+  readonly kind = 'New'
+>kind : Symbol(New.kind, Decl(complexClassStructureNoCrash.ts, 212, 66))
+
+  readonly instantiated!: Reference<S>
+>instantiated : Symbol(New.instantiated, Decl(complexClassStructureNoCrash.ts, 213, 23))
+>Reference : Symbol(Reference, Decl(complexClassStructureNoCrash.ts, 189, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 212, 17))
+
+  readonly args!: List<Expression<S>> | List<NamedArgument<S>>
+>args : Symbol(New.args, Decl(complexClassStructureNoCrash.ts, 214, 38))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>Expression : Symbol(Expression, Decl(complexClassStructureNoCrash.ts, 173, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 212, 17))
+>List : Symbol(List, Decl(complexClassStructureNoCrash.ts, 2, 25))
+>NamedArgument : Symbol(NamedArgument, Decl(complexClassStructureNoCrash.ts, 49, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 212, 17))
+}
+
+export class If<S extends Stage = Final> extends $Expression<S> {
+>If : Symbol(If, Decl(complexClassStructureNoCrash.ts, 216, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 218, 16))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Expression : Symbol($Expression, Decl(complexClassStructureNoCrash.ts, 183, 10))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 218, 16))
+
+  readonly kind = 'If'
+>kind : Symbol(If.kind, Decl(complexClassStructureNoCrash.ts, 218, 65))
+
+  readonly thenBody!: Body<S>
+>thenBody : Symbol(If.thenBody, Decl(complexClassStructureNoCrash.ts, 219, 22))
+>Body : Symbol(Body, Decl(complexClassStructureNoCrash.ts, 59, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 218, 16))
+
+  readonly elseBody!: Fillable<S, Body<S>>
+>elseBody : Symbol(If.elseBody, Decl(complexClassStructureNoCrash.ts, 220, 29))
+>Fillable : Symbol(Fillable, Decl(complexClassStructureNoCrash.ts, 12, 85))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 218, 16))
+>Body : Symbol(Body, Decl(complexClassStructureNoCrash.ts, 59, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 218, 16))
+}
+
+export class Throw<S extends Stage = Final> extends $Expression<S> {
+>Throw : Symbol(Throw, Decl(complexClassStructureNoCrash.ts, 222, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 224, 19))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Expression : Symbol($Expression, Decl(complexClassStructureNoCrash.ts, 183, 10))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 224, 19))
+
+  readonly kind = 'Throw'
+>kind : Symbol(Throw.kind, Decl(complexClassStructureNoCrash.ts, 224, 68))
+}
+
+export class Try<S extends Stage = Final> extends $Expression<S> {
+>Try : Symbol(Try, Decl(complexClassStructureNoCrash.ts, 226, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 228, 17))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Expression : Symbol($Expression, Decl(complexClassStructureNoCrash.ts, 183, 10))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 228, 17))
+
+  readonly kind = 'Try'
+>kind : Symbol(Try.kind, Decl(complexClassStructureNoCrash.ts, 228, 66))
+}
+
+export class Catch<S extends Stage = Final> extends $Expression<S> {
+>Catch : Symbol(Catch, Decl(complexClassStructureNoCrash.ts, 230, 1))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 232, 19))
+>Stage : Symbol(Stage, Decl(complexClassStructureNoCrash.ts, 4, 48))
+>Final : Symbol(Final, Decl(complexClassStructureNoCrash.ts, 9, 87))
+>$Expression : Symbol($Expression, Decl(complexClassStructureNoCrash.ts, 183, 10))
+>S : Symbol(S, Decl(complexClassStructureNoCrash.ts, 232, 19))
+
+  readonly kind = 'Catch'
+>kind : Symbol(Catch.kind, Decl(complexClassStructureNoCrash.ts, 232, 68))
+}
diff --git a/tests/baselines/reference/complexClassStructureNoCrash.types b/tests/baselines/reference/complexClassStructureNoCrash.types
new file mode 100644
index 0000000000000..cd59e524e1d70
--- /dev/null
+++ b/tests/baselines/reference/complexClassStructureNoCrash.types
@@ -0,0 +1,608 @@
+=== tests/cases/compiler/complexClassStructureNoCrash.ts ===
+const { assign } = Object
+>assign : { <T, U>(target: T, source: U): T & U; <T, U, V>(target: T, source1: U, source2: V): T & U & V; <T, U, V, W>(target: T, source1: U, source2: V, source3: W): T & U & V & W; (target: object, ...sources: any[]): any; }
+>Object : ObjectConstructor
+
+export type Name = string
+>Name : string
+
+export type List<T> = ReadonlyArray<T>
+>List : List<T>
+
+export type Payload<T> = Record<string, unknown>
+>Payload : Record<string, unknown>
+
+export type Stage = Raw | Filled | Linked
+>Stage : Stage
+
+export abstract class Raw { protected readonly rawTag = 'Raw' }
+>Raw : Raw
+>rawTag : "Raw"
+>'Raw' : "Raw"
+
+export abstract class Filled extends Raw { protected readonly filledTag = 'Filled' }
+>Filled : Filled
+>Raw : Raw
+>filledTag : "Filled"
+>'Filled' : "Filled"
+
+export abstract class Linked extends Filled { protected readonly linkedTag = 'Linked' }
+>Linked : Linked
+>Filled : Filled
+>linkedTag : "Linked"
+>'Linked' : "Linked"
+
+export type Final = Linked
+>Final : Linked
+
+type Stageable<S extends Stage, C extends Stage, T> = S extends C ? T : T | undefined
+>Stageable : Stageable<S, C, T>
+
+export type Fillable<S extends Stage, T> = Stageable<S, Filled, T>
+>Fillable : Stageable<S, Filled, T>
+
+export type Linkable<S extends Stage, T> = Stageable<S, Linked, T>
+>Linkable : Stageable<S, Linked, T>
+
+export type Kind = Node['kind']
+>Kind : "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try"
+
+export type Category = 'Entity' | 'Module' | 'Sentence' | 'Expression'
+>Category : Category
+
+export type NodeOfKind<K extends Kind, S extends Stage> = Extract<Node<S>, { kind: K }>
+>NodeOfKind : Extract<Parameter<S>, { kind: K; }> | Extract<NamedArgument<S>, { kind: K; }> | Extract<Import<S>, { kind: K; }> | Extract<Body<S>, { kind: K; }> | Extract<Catch<S>, { kind: K; }> | Extract<Package<S>, { kind: K; }> | Extract<Program<S>, { kind: K; }> | Extract<Test<S>, { kind: K; }> | Extract<Describe<S>, { kind: K; }> | Extract<Class<S>, { kind: K; }> | Extract<Singleton<S>, { kind: K; }> | Extract<Mixin<S>, { kind: K; }> | Extract<Variable<S>, { kind: K; }> | Extract<Fixture<S>, { kind: K; }> | Extract<Method<S>, { kind: K; }> | Extract<Constructor<S>, { kind: K; }> | Extract<Field<S>, { kind: K; }> | Extract<Return<S>, { kind: K; }> | Extract<Assignment<S>, { kind: K; }> | Extract<Reference<S>, { kind: K; }> | Extract<Self<S>, { kind: K; }> | Extract<Send<S>, { kind: K; }> | Extract<Super<S>, { kind: K; }> | Extract<New<S>, { kind: K; }> | Extract<If<S>, { kind: K; }> | Extract<Throw<S>, { kind: K; }> | Extract<Try<S>, { kind: K; }>
+>kind : K
+
+export type NodeOfKindOrCategory<Q extends Kind | Category, S extends Stage> =
+>NodeOfKindOrCategory : NodeOfKindOrCategory<Q, S>
+
+  Q extends Kind ? NodeOfKind<Q, S> :
+  never
+
+export type Node<S extends Stage = Final>
+>Node : Node<S>
+
+  = Parameter<S>
+  | NamedArgument<S>
+  | Import<S>
+  | Body<S>
+  | Catch<S>
+  | Entity<S>
+  | DescribeMember<S>
+  | ClassMember<S>
+  | Sentence<S>
+
+abstract class $Node<S extends Stage> {
+>$Node : $Node<S>
+
+  readonly stage?: S
+>stage : S
+
+  abstract readonly kind: Kind
+>kind : "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try"
+
+  constructor(payload: Record<string, unknown>) {
+>payload : Record<string, unknown>
+
+    assign(this, payload)
+>assign(this, payload) : this & Record<string, unknown>
+>assign : { <T, U>(target: T, source: U): T & U; <T, U, V>(target: T, source1: U, source2: V): T & U & V; <T, U, V, W>(target: T, source1: U, source2: V, source3: W): T & U & V & W; (target: object, ...sources: any[]): any; }
+>this : this
+>payload : Record<string, unknown>
+  }
+ 
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+>is : <Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>
+>kindOrCategory : Q
+
+    return this.kind === kindOrCategory
+>this.kind === kindOrCategory : boolean
+>this.kind : "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try"
+>this : this
+>kind : "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try"
+>kindOrCategory : Q
+  }
+}
+
+export class Parameter<S extends Stage = Final> extends $Node<S> {
+>Parameter : Parameter<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Parameter'
+>kind : "Parameter"
+>'Parameter' : "Parameter"
+}
+
+export class NamedArgument<S extends Stage = Final> extends $Node<S> {
+>NamedArgument : NamedArgument<S>
+>$Node : $Node<S>
+
+  readonly kind = 'NamedArgument'
+>kind : "NamedArgument"
+>'NamedArgument' : "NamedArgument"
+
+  readonly value!: Expression<S>
+>value : Expression<S>
+}
+
+export class Import<S extends Stage = Final> extends $Node<S> {
+>Import : Import<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Import'
+>kind : "Import"
+>'Import' : "Import"
+
+  readonly entity!: Reference<S>
+>entity : Reference<S>
+}
+
+export class Body<S extends Stage = Final> extends $Node<S> {
+>Body : Body<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Body'
+>kind : "Body"
+>'Body' : "Body"
+
+  readonly sentences!: List<Sentence<S>>
+>sentences : List<Sentence<S>>
+}
+
+export type Entity<S extends Stage = Final>
+>Entity : Entity<S>
+
+  = Package<S>
+  | Program<S>
+  | Test<S>
+  | Describe<S>
+  | Module<S>
+  | Variable<S>
+
+
+export class Package<S extends Stage = Final> extends $Node<S> {
+>Package : Package<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Package'
+>kind : "Package"
+>'Package' : "Package"
+
+  readonly imports!: List<Import<S>>
+>imports : List<Import<S>>
+
+  readonly members!: List<Entity<S>>
+>members : List<Entity<S>>
+}
+
+export class Program<S extends Stage = Final> extends $Node<S> {
+>Program : Program<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Program'
+>kind : "Program"
+>'Program' : "Program"
+
+  readonly body!: Body<S>
+>body : Body<S>
+}
+
+export class Test<S extends Stage = Final> extends $Node<S> {
+>Test : Test<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Test'
+>kind : "Test"
+>'Test' : "Test"
+
+  readonly body!: Body<S>
+>body : Body<S>
+}
+
+export class Describe<S extends Stage = Final> extends $Node<S> {
+>Describe : Describe<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Describe'
+>kind : "Describe"
+>'Describe' : "Describe"
+
+  readonly members!: List<DescribeMember<S>>
+>members : List<DescribeMember<S>>
+
+  tests(): List<Test<S>> { return this.members.filter((member): member is Test<S> => member.is('Test')) }
+>tests : () => List<Test<S>>
+>this.members.filter((member): member is Test<S> => member.is('Test')) : Test<S>[]
+>this.members.filter : { <S extends DescribeMember<S>>(predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => value is S, thisArg?: any): S[]; (predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => unknown, thisArg?: any): DescribeMember<S>[]; }
+>this.members : List<DescribeMember<S>>
+>this : this
+>members : List<DescribeMember<S>>
+>filter : { <S extends DescribeMember<S>>(predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => value is S, thisArg?: any): S[]; (predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => unknown, thisArg?: any): DescribeMember<S>[]; }
+>(member): member is Test<S> => member.is('Test') : (member: DescribeMember<S>) => member is Test<S>
+>member : DescribeMember<S>
+>member.is('Test') : boolean
+>member.is : (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>)
+>member : DescribeMember<S>
+>is : (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>)
+>'Test' : "Test"
+
+  methods(): List<Method<S>> { return this.members.filter((member): member is Method<S> => member.is('Method')) }
+>methods : () => List<Method<S>>
+>this.members.filter((member): member is Method<S> => member.is('Method')) : Method<S>[]
+>this.members.filter : { <S extends DescribeMember<S>>(predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => value is S, thisArg?: any): S[]; (predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => unknown, thisArg?: any): DescribeMember<S>[]; }
+>this.members : List<DescribeMember<S>>
+>this : this
+>members : List<DescribeMember<S>>
+>filter : { <S extends DescribeMember<S>>(predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => value is S, thisArg?: any): S[]; (predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => unknown, thisArg?: any): DescribeMember<S>[]; }
+>(member): member is Method<S> => member.is('Method') : (member: DescribeMember<S>) => member is Method<S>
+>member : DescribeMember<S>
+>member.is('Method') : boolean
+>member.is : (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>)
+>member : DescribeMember<S>
+>is : (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>)
+>'Method' : "Method"
+
+  variables(): List<Variable<S>> { return this.members.filter((member): member is Variable<S> => member.is('Variable')) }
+>variables : () => List<Variable<S>>
+>this.members.filter((member): member is Variable<S> => member.is('Variable')) : Variable<S>[]
+>this.members.filter : { <S extends DescribeMember<S>>(predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => value is S, thisArg?: any): S[]; (predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => unknown, thisArg?: any): DescribeMember<S>[]; }
+>this.members : List<DescribeMember<S>>
+>this : this
+>members : List<DescribeMember<S>>
+>filter : { <S extends DescribeMember<S>>(predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => value is S, thisArg?: any): S[]; (predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => unknown, thisArg?: any): DescribeMember<S>[]; }
+>(member): member is Variable<S> => member.is('Variable') : (member: DescribeMember<S>) => member is Variable<S>
+>member : DescribeMember<S>
+>member.is('Variable') : boolean
+>member.is : (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>)
+>member : DescribeMember<S>
+>is : (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>)
+>'Variable' : "Variable"
+
+  fixtures(): List<Fixture<S>> { return this.members.filter((member): member is Fixture<S> => member.is('Fixture')) }
+>fixtures : () => List<Fixture<S>>
+>this.members.filter((member): member is Fixture<S> => member.is('Fixture')) : Fixture<S>[]
+>this.members.filter : { <S extends DescribeMember<S>>(predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => value is S, thisArg?: any): S[]; (predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => unknown, thisArg?: any): DescribeMember<S>[]; }
+>this.members : List<DescribeMember<S>>
+>this : this
+>members : List<DescribeMember<S>>
+>filter : { <S extends DescribeMember<S>>(predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => value is S, thisArg?: any): S[]; (predicate: (value: DescribeMember<S>, index: number, array: readonly DescribeMember<S>[]) => unknown, thisArg?: any): DescribeMember<S>[]; }
+>(member): member is Fixture<S> => member.is('Fixture') : (member: DescribeMember<S>) => member is Fixture<S>
+>member : DescribeMember<S>
+>member.is('Fixture') : boolean
+>member.is : (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>)
+>member : DescribeMember<S>
+>is : (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>) | (<Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>)
+>'Fixture' : "Fixture"
+}
+
+export class Variable<S extends Stage = Final> extends $Node<S> {
+>Variable : Variable<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Variable'
+>kind : "Variable"
+>'Variable' : "Variable"
+
+  readonly value!: Fillable<S, Expression<S>>
+>value : Stageable<S, Filled, Expression<S>>
+
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+>is : <Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>
+>kindOrCategory : Q
+
+    return [this.kind, 'Sentence', 'Entity'].includes(kindOrCategory)
+>[this.kind, 'Sentence', 'Entity'].includes(kindOrCategory) : boolean
+>[this.kind, 'Sentence', 'Entity'].includes : (searchElement: string, fromIndex?: number) => boolean
+>[this.kind, 'Sentence', 'Entity'] : string[]
+>this.kind : "Variable"
+>this : this
+>kind : "Variable"
+>'Sentence' : "Sentence"
+>'Entity' : "Entity"
+>includes : (searchElement: string, fromIndex?: number) => boolean
+>kindOrCategory : Q
+  }
+}
+
+export type Module<S extends Stage = Final> = Class<S> | Singleton<S> | Mixin<S>
+>Module : Module<S>
+
+export class Class<S extends Stage = Final> extends $Node<S> {
+>Class : Class<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Class'
+>kind : "Class"
+>'Class' : "Class"
+
+  readonly mixins!: List<Reference<S>>
+>mixins : List<Reference<S>>
+
+  readonly members!: List<ClassMember<S>>
+>members : List<ClassMember<S>>
+
+  readonly superclass!: Fillable<S, Reference<S> | null>
+>superclass : Stageable<S, Filled, Reference<S>>
+>null : null
+}
+
+export class Singleton<S extends Stage = Final> extends $Node<S> {
+>Singleton : Singleton<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Singleton'
+>kind : "Singleton"
+>'Singleton' : "Singleton"
+
+  readonly mixins!: List<Reference<S>>
+>mixins : List<Reference<S>>
+
+  readonly members!: List<ObjectMember<S>>
+>members : List<ObjectMember<S>>
+
+  readonly superCall!: Fillable<S, {
+>superCall : Stageable<S, Filled, { superclass: Reference<S>; args: List<Expression<S>> | List<NamedArgument<S>>; }>
+
+    superclass: Reference<S>,
+>superclass : Reference<S>
+
+    args: List<Expression<S>> | List<NamedArgument<S>>
+>args : List<Expression<S>> | List<NamedArgument<S>>
+
+  }>
+}
+
+export class Mixin<S extends Stage = Final> extends $Node<S> {
+>Mixin : Mixin<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Mixin'
+>kind : "Mixin"
+>'Mixin' : "Mixin"
+
+  readonly mixins!: List<Reference<S>>
+>mixins : List<Reference<S>>
+
+  readonly members!: List<ObjectMember<S>>
+>members : List<ObjectMember<S>>
+}
+
+export type ObjectMember<S extends Stage = Final> = Field<S> | Method<S>
+>ObjectMember : ObjectMember<S>
+
+export type ClassMember<S extends Stage = Final> = Constructor<S> | ObjectMember<S>
+>ClassMember : ClassMember<S>
+
+export type DescribeMember<S extends Stage = Final> = Variable<S> | Fixture<S> | Test<S> | Method<S>
+>DescribeMember : DescribeMember<S>
+
+export class Field<S extends Stage = Final> extends $Node<S> {
+>Field : Field<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Field'
+>kind : "Field"
+>'Field' : "Field"
+
+  readonly value!: Fillable<S, Expression<S>>
+>value : Stageable<S, Filled, Expression<S>>
+}
+
+export class Method<S extends Stage = Final> extends $Node<S> {
+>Method : Method<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Method'
+>kind : "Method"
+>'Method' : "Method"
+
+  readonly parameters!: List<Parameter<S>>
+>parameters : List<Parameter<S>>
+
+  readonly body?: Body<S>
+>body : Body<S>
+}
+
+export class Constructor<S extends Stage = Final> extends $Node<S> {
+>Constructor : Constructor<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Constructor'
+>kind : "Constructor"
+>'Constructor' : "Constructor"
+
+  readonly parameters!: List<Parameter<S>>
+>parameters : List<Parameter<S>>
+
+  readonly body!: Body<S>
+>body : Body<S>
+
+  readonly baseCall?: { callsSuper: boolean, args: List<Expression<S>> }
+>baseCall : { callsSuper: boolean; args: List<Expression<S>>; }
+>callsSuper : boolean
+>args : List<Expression<S>>
+}
+
+export class Fixture<S extends Stage = Final> extends $Node<S> {
+>Fixture : Fixture<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Fixture'
+>kind : "Fixture"
+>'Fixture' : "Fixture"
+
+  readonly body!: Body<S>
+>body : Body<S>
+}
+
+export type Sentence<S extends Stage = Final> = Variable<S> | Return<S> | Assignment<S> | Expression<S>
+>Sentence : Sentence<S>
+
+export class Return<S extends Stage = Final> extends $Node<S> {
+>Return : Return<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Return'
+>kind : "Return"
+>'Return' : "Return"
+
+  readonly value?: Expression<S>
+>value : Expression<S>
+}
+
+export class Assignment<S extends Stage = Final> extends $Node<S> {
+>Assignment : Assignment<S>
+>$Node : $Node<S>
+
+  readonly kind = 'Assignment'
+>kind : "Assignment"
+>'Assignment' : "Assignment"
+
+  readonly variable!: Reference<S>
+>variable : Reference<S>
+
+  readonly value!: Expression<S>
+>value : Expression<S>
+}
+
+export type Expression<S extends Stage = Final>
+>Expression : Expression<S>
+
+  = Reference<S>
+  | Self<S>
+  | Send<S>
+  | Super<S>
+  | New<S>
+  | If<S>
+  | Throw<S>
+  | Try<S>
+
+abstract class $Expression<S extends Stage> extends $Node<S> {
+>$Expression : $Expression<S>
+>$Node : $Node<S>
+
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+>is : <Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>
+>kindOrCategory : Q
+
+    return kindOrCategory === 'Expression' || super.is(kindOrCategory)
+>kindOrCategory === 'Expression' || super.is(kindOrCategory) : boolean
+>kindOrCategory === 'Expression' : boolean
+>kindOrCategory : Q
+>'Expression' : "Expression"
+>super.is(kindOrCategory) : boolean
+>super.is : <Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>
+>super : $Node<S>
+>is : <Q extends "Parameter" | "NamedArgument" | "Import" | "Body" | "Catch" | "Package" | "Program" | "Test" | "Describe" | "Class" | "Singleton" | "Mixin" | "Variable" | "Fixture" | "Method" | "Constructor" | "Field" | "Return" | "Assignment" | "Reference" | "Self" | "Send" | "Super" | "New" | "If" | "Throw" | "Try" | "Entity" | "Module" | "Sentence" | "Expression">(kindOrCategory: Q) => this is NodeOfKindOrCategory<Q, S>
+>kindOrCategory : Q
+  }
+}
+
+export class Reference<S extends Stage = Final> extends $Expression<S> {
+>Reference : Reference<S>
+>$Expression : $Expression<S>
+
+  readonly kind = 'Reference'
+>kind : "Reference"
+>'Reference' : "Reference"
+
+  readonly name!: Name
+>name : string
+}
+
+export class Self<S extends Stage = Final> extends $Expression<S> {
+>Self : Self<S>
+>$Expression : $Expression<S>
+
+  readonly kind = 'Self'
+>kind : "Self"
+>'Self' : "Self"
+}
+
+export class Send<S extends Stage = Final> extends $Expression<S> {
+>Send : Send<S>
+>$Expression : $Expression<S>
+
+  readonly kind = 'Send'
+>kind : "Send"
+>'Send' : "Send"
+
+  readonly receiver!: Expression<S>
+>receiver : Expression<S>
+
+  readonly message!: Name
+>message : string
+
+  readonly args!: List<Expression<S>>
+>args : List<Expression<S>>
+}
+
+export class Super<S extends Stage = Final> extends $Expression<S> {
+>Super : Super<S>
+>$Expression : $Expression<S>
+
+  readonly kind = 'Super'
+>kind : "Super"
+>'Super' : "Super"
+
+  readonly args!: List<Expression<S>>
+>args : List<Expression<S>>
+}
+
+export class New<S extends Stage = Final> extends $Expression<S> {
+>New : New<S>
+>$Expression : $Expression<S>
+
+  readonly kind = 'New'
+>kind : "New"
+>'New' : "New"
+
+  readonly instantiated!: Reference<S>
+>instantiated : Reference<S>
+
+  readonly args!: List<Expression<S>> | List<NamedArgument<S>>
+>args : List<Expression<S>> | List<NamedArgument<S>>
+}
+
+export class If<S extends Stage = Final> extends $Expression<S> {
+>If : If<S>
+>$Expression : $Expression<S>
+
+  readonly kind = 'If'
+>kind : "If"
+>'If' : "If"
+
+  readonly thenBody!: Body<S>
+>thenBody : Body<S>
+
+  readonly elseBody!: Fillable<S, Body<S>>
+>elseBody : Stageable<S, Filled, Body<S>>
+}
+
+export class Throw<S extends Stage = Final> extends $Expression<S> {
+>Throw : Throw<S>
+>$Expression : $Expression<S>
+
+  readonly kind = 'Throw'
+>kind : "Throw"
+>'Throw' : "Throw"
+}
+
+export class Try<S extends Stage = Final> extends $Expression<S> {
+>Try : Try<S>
+>$Expression : $Expression<S>
+
+  readonly kind = 'Try'
+>kind : "Try"
+>'Try' : "Try"
+}
+
+export class Catch<S extends Stage = Final> extends $Expression<S> {
+>Catch : Catch<S>
+>$Expression : $Expression<S>
+
+  readonly kind = 'Catch'
+>kind : "Catch"
+>'Catch' : "Catch"
+}
diff --git a/tests/baselines/reference/errorElaboration.errors.txt b/tests/baselines/reference/errorElaboration.errors.txt
index 30c4fe8efd64b..b33f7d59ad17a 100644
--- a/tests/baselines/reference/errorElaboration.errors.txt
+++ b/tests/baselines/reference/errorElaboration.errors.txt
@@ -1,8 +1,12 @@
 tests/cases/compiler/errorElaboration.ts(10,18): error TS2300: Duplicate identifier 'foo'.
 tests/cases/compiler/errorElaboration.ts(12,5): error TS2345: Argument of type '() => Container<Ref<string>>' is not assignable to parameter of type '() => Container<Ref<number>>'.
-  Type 'Container<Ref<string>>' is not assignable to type 'Container<Ref<number>>'.
-    Type 'Ref<string>' is not assignable to type 'Ref<number>'.
-      Type 'string' is not assignable to type 'number'.
+  Call signature return types 'Container<Ref<string>>' and 'Container<Ref<number>>' are incompatible.
+    The types of 'm1.m1.m1.m2' are incompatible between these types.
+      Type 'Ref<Ref<Ref<Ref<string>>>>' is not assignable to type 'Ref<Ref<Ref<Ref<number>>>>'.
+        Type 'Ref<Ref<Ref<string>>>' is not assignable to type 'Ref<Ref<Ref<number>>>'.
+          Type 'Ref<Ref<string>>' is not assignable to type 'Ref<Ref<number>>'.
+            Type 'Ref<string>' is not assignable to type 'Ref<number>'.
+              Type 'string' is not assignable to type 'number'.
 tests/cases/compiler/errorElaboration.ts(17,11): error TS2322: Type '"bar"' is not assignable to type '"foo"'.
 tests/cases/compiler/errorElaboration.ts(22,7): error TS2300: Duplicate identifier 'foo'.
 tests/cases/compiler/errorElaboration.ts(23,15): error TS2538: Type 'any' cannot be used as an index type.
@@ -26,9 +30,13 @@ tests/cases/compiler/errorElaboration.ts(23,19): error TS2339: Property 'bar' do
     foo(a);
         ~
 !!! error TS2345: Argument of type '() => Container<Ref<string>>' is not assignable to parameter of type '() => Container<Ref<number>>'.
-!!! error TS2345:   Type 'Container<Ref<string>>' is not assignable to type 'Container<Ref<number>>'.
-!!! error TS2345:     Type 'Ref<string>' is not assignable to type 'Ref<number>'.
-!!! error TS2345:       Type 'string' is not assignable to type 'number'.
+!!! error TS2345:   Call signature return types 'Container<Ref<string>>' and 'Container<Ref<number>>' are incompatible.
+!!! error TS2345:     The types of 'm1.m1.m1.m2' are incompatible between these types.
+!!! error TS2345:       Type 'Ref<Ref<Ref<Ref<string>>>>' is not assignable to type 'Ref<Ref<Ref<Ref<number>>>>'.
+!!! error TS2345:         Type 'Ref<Ref<Ref<string>>>' is not assignable to type 'Ref<Ref<Ref<number>>>'.
+!!! error TS2345:           Type 'Ref<Ref<string>>' is not assignable to type 'Ref<Ref<number>>'.
+!!! error TS2345:             Type 'Ref<string>' is not assignable to type 'Ref<number>'.
+!!! error TS2345:               Type 'string' is not assignable to type 'number'.
     
     // Repro for #25498
     
diff --git a/tests/baselines/reference/genericCloneReturnTypes.errors.txt b/tests/baselines/reference/genericCloneReturnTypes.errors.txt
index 0e54ebc02cff2..ecbf301429589 100644
--- a/tests/baselines/reference/genericCloneReturnTypes.errors.txt
+++ b/tests/baselines/reference/genericCloneReturnTypes.errors.txt
@@ -1,5 +1,6 @@
 tests/cases/compiler/genericCloneReturnTypes.ts(25,1): error TS2322: Type 'Bar<string>' is not assignable to type 'Bar<number>'.
-  Type 'string' is not assignable to type 'number'.
+  Types of property 't' are incompatible.
+    Type 'string' is not assignable to type 'number'.
 
 
 ==== tests/cases/compiler/genericCloneReturnTypes.ts (1 errors) ====
@@ -30,4 +31,5 @@ tests/cases/compiler/genericCloneReturnTypes.ts(25,1): error TS2322: Type 'Bar<s
     b = b3;
     ~
 !!! error TS2322: Type 'Bar<string>' is not assignable to type 'Bar<number>'.
-!!! error TS2322:   Type 'string' is not assignable to type 'number'.
\ No newline at end of file
+!!! error TS2322:   Types of property 't' are incompatible.
+!!! error TS2322:     Type 'string' is not assignable to type 'number'.
\ No newline at end of file
diff --git a/tests/baselines/reference/objectTypeWithRecursiveWrappedProperty.errors.txt b/tests/baselines/reference/objectTypeWithRecursiveWrappedProperty.errors.txt
index 582d7719a8976..e70e142573428 100644
--- a/tests/baselines/reference/objectTypeWithRecursiveWrappedProperty.errors.txt
+++ b/tests/baselines/reference/objectTypeWithRecursiveWrappedProperty.errors.txt
@@ -1,5 +1,6 @@
 tests/cases/conformance/types/typeRelationships/recursiveTypes/objectTypeWithRecursiveWrappedProperty.ts(13,1): error TS2322: Type 'List<string>' is not assignable to type 'List<number>'.
-  Type 'string' is not assignable to type 'number'.
+  Types of property 'data' are incompatible.
+    Type 'string' is not assignable to type 'number'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/recursiveTypes/objectTypeWithRecursiveWrappedProperty.ts (1 errors) ====
@@ -18,4 +19,5 @@ tests/cases/conformance/types/typeRelationships/recursiveTypes/objectTypeWithRec
     list1 = list3; // error
     ~~~~~
 !!! error TS2322: Type 'List<string>' is not assignable to type 'List<number>'.
-!!! error TS2322:   Type 'string' is not assignable to type 'number'.
\ No newline at end of file
+!!! error TS2322:   Types of property 'data' are incompatible.
+!!! error TS2322:     Type 'string' is not assignable to type 'number'.
\ No newline at end of file
diff --git a/tests/baselines/reference/objectTypeWithRecursiveWrappedProperty2.errors.txt b/tests/baselines/reference/objectTypeWithRecursiveWrappedProperty2.errors.txt
index 6349a4528213a..a3905028d0dff 100644
--- a/tests/baselines/reference/objectTypeWithRecursiveWrappedProperty2.errors.txt
+++ b/tests/baselines/reference/objectTypeWithRecursiveWrappedProperty2.errors.txt
@@ -1,5 +1,6 @@
 tests/cases/conformance/types/typeRelationships/recursiveTypes/objectTypeWithRecursiveWrappedProperty2.ts(13,1): error TS2322: Type 'List<string>' is not assignable to type 'List<number>'.
-  Type 'string' is not assignable to type 'number'.
+  Types of property 'data' are incompatible.
+    Type 'string' is not assignable to type 'number'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/recursiveTypes/objectTypeWithRecursiveWrappedProperty2.ts (1 errors) ====
@@ -18,4 +19,5 @@ tests/cases/conformance/types/typeRelationships/recursiveTypes/objectTypeWithRec
     list1 = list3; // error
     ~~~~~
 !!! error TS2322: Type 'List<string>' is not assignable to type 'List<number>'.
-!!! error TS2322:   Type 'string' is not assignable to type 'number'.
\ No newline at end of file
+!!! error TS2322:   Types of property 'data' are incompatible.
+!!! error TS2322:     Type 'string' is not assignable to type 'number'.
\ No newline at end of file
diff --git a/tests/baselines/reference/objectTypeWithRecursiveWrappedPropertyCheckedNominally.errors.txt b/tests/baselines/reference/objectTypeWithRecursiveWrappedPropertyCheckedNominally.errors.txt
index 8f2ebf0131a84..72093dab99e9a 100644
--- a/tests/baselines/reference/objectTypeWithRecursiveWrappedPropertyCheckedNominally.errors.txt
+++ b/tests/baselines/reference/objectTypeWithRecursiveWrappedPropertyCheckedNominally.errors.txt
@@ -15,7 +15,7 @@ tests/cases/conformance/types/typeRelationships/recursiveTypes/objectTypeWithRec
 tests/cases/conformance/types/typeRelationships/recursiveTypes/objectTypeWithRecursiveWrappedPropertyCheckedNominally.ts(42,5): error TS2322: Type 'U' is not assignable to type 'T'.
   'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint 'MyList<number>'.
     Type 'MyList<number>' is not assignable to type 'T'.
-      'T' could be instantiated with an arbitrary type which could be unrelated to 'MyList<number>'.
+      'MyList<number>' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint 'MyList<number>'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/recursiveTypes/objectTypeWithRecursiveWrappedPropertyCheckedNominally.ts (5 errors) ====
@@ -83,7 +83,7 @@ tests/cases/conformance/types/typeRelationships/recursiveTypes/objectTypeWithRec
 !!! error TS2322: Type 'U' is not assignable to type 'T'.
 !!! error TS2322:   'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint 'MyList<number>'.
 !!! error TS2322:     Type 'MyList<number>' is not assignable to type 'T'.
-!!! error TS2322:       'T' could be instantiated with an arbitrary type which could be unrelated to 'MyList<number>'.
+!!! error TS2322:       'MyList<number>' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint 'MyList<number>'.
         u = t; // was error, ok after constraint made illegal, doesn't matter
     
         var a: List<number>;
diff --git a/tests/baselines/reference/privateNamesInGenericClasses.errors.txt b/tests/baselines/reference/privateNamesInGenericClasses.errors.txt
index d617432535020..31bdf0eeea51e 100644
--- a/tests/baselines/reference/privateNamesInGenericClasses.errors.txt
+++ b/tests/baselines/reference/privateNamesInGenericClasses.errors.txt
@@ -1,8 +1,10 @@
 tests/cases/conformance/classes/members/privateNames/privateNamesInGenericClasses.ts(10,3): error TS18013: Property '#foo' is not accessible outside class 'C' because it has a private identifier.
 tests/cases/conformance/classes/members/privateNames/privateNamesInGenericClasses.ts(11,1): error TS2322: Type 'C<string>' is not assignable to type 'C<number>'.
-  Type 'string' is not assignable to type 'number'.
+  Types of property '#foo' are incompatible.
+    Type 'string' is not assignable to type 'number'.
 tests/cases/conformance/classes/members/privateNames/privateNamesInGenericClasses.ts(12,1): error TS2322: Type 'C<number>' is not assignable to type 'C<string>'.
-  Type 'number' is not assignable to type 'string'.
+  Types of property '#foo' are incompatible.
+    Type 'number' is not assignable to type 'string'.
 
 
 ==== tests/cases/conformance/classes/members/privateNames/privateNamesInGenericClasses.ts (3 errors) ====
@@ -21,9 +23,11 @@ tests/cases/conformance/classes/members/privateNames/privateNamesInGenericClasse
     a = b;                                    // Error
     ~
 !!! error TS2322: Type 'C<string>' is not assignable to type 'C<number>'.
-!!! error TS2322:   Type 'string' is not assignable to type 'number'.
+!!! error TS2322:   Types of property '#foo' are incompatible.
+!!! error TS2322:     Type 'string' is not assignable to type 'number'.
     b = a;                                    // Error
     ~
 !!! error TS2322: Type 'C<number>' is not assignable to type 'C<string>'.
-!!! error TS2322:   Type 'number' is not assignable to type 'string'.
+!!! error TS2322:   Types of property '#foo' are incompatible.
+!!! error TS2322:     Type 'number' is not assignable to type 'string'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/types.asyncGenerators.es2018.2.errors.txt b/tests/baselines/reference/types.asyncGenerators.es2018.2.errors.txt
index 6c76d41809a98..7ccc1d2790686 100644
--- a/tests/baselines/reference/types.asyncGenerators.es2018.2.errors.txt
+++ b/tests/baselines/reference/types.asyncGenerators.es2018.2.errors.txt
@@ -2,12 +2,14 @@ tests/cases/conformance/types/asyncGenerators/types.asyncGenerators.es2018.2.ts(
 tests/cases/conformance/types/asyncGenerators/types.asyncGenerators.es2018.2.ts(8,12): error TS2504: Type 'Promise<number[]>' must have a '[Symbol.asyncIterator]()' method that returns an async iterator.
 tests/cases/conformance/types/asyncGenerators/types.asyncGenerators.es2018.2.ts(10,7): error TS2322: Type '() => AsyncGenerator<string, void, undefined>' is not assignable to type '() => AsyncIterableIterator<number>'.
   Call signature return types 'AsyncGenerator<string, void, undefined>' and 'AsyncIterableIterator<number>' are incompatible.
-    The types returned by 'next(...)' are incompatible between these types.
-      Type 'Promise<IteratorResult<string, void>>' is not assignable to type 'Promise<IteratorResult<number, any>>'.
-        Type 'IteratorResult<string, void>' is not assignable to type 'IteratorResult<number, any>'.
-          Type 'IteratorYieldResult<string>' is not assignable to type 'IteratorResult<number, any>'.
-            Type 'IteratorYieldResult<string>' is not assignable to type 'IteratorYieldResult<number>'.
-              Type 'string' is not assignable to type 'number'.
+    The types of 'next(...).then' are incompatible between these types.
+      Type '<TResult1 = IteratorResult<string, void>, TResult2 = never>(onfulfilled?: (value: IteratorResult<string, void>) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = IteratorResult<number, any>, TResult2 = never>(onfulfilled?: (value: IteratorResult<number, any>) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>'.
+        Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+          Types of parameters 'value' and 'value' are incompatible.
+            Type 'IteratorResult<string, void>' is not assignable to type 'IteratorResult<number, any>'.
+              Type 'IteratorYieldResult<string>' is not assignable to type 'IteratorResult<number, any>'.
+                Type 'IteratorYieldResult<string>' is not assignable to type 'IteratorYieldResult<number>'.
+                  Type 'string' is not assignable to type 'number'.
 tests/cases/conformance/types/asyncGenerators/types.asyncGenerators.es2018.2.ts(13,7): error TS2322: Type '() => AsyncGenerator<string, void, undefined>' is not assignable to type '() => AsyncIterableIterator<number>'.
   Type 'AsyncGenerator<string, void, undefined>' is not assignable to type 'AsyncIterableIterator<number>'.
 tests/cases/conformance/types/asyncGenerators/types.asyncGenerators.es2018.2.ts(16,7): error TS2322: Type '() => AsyncGenerator<string, void, unknown>' is not assignable to type '() => AsyncIterableIterator<number>'.
@@ -67,12 +69,14 @@ tests/cases/conformance/types/asyncGenerators/types.asyncGenerators.es2018.2.ts(
           ~~~~~~~~~~~~~~
 !!! error TS2322: Type '() => AsyncGenerator<string, void, undefined>' is not assignable to type '() => AsyncIterableIterator<number>'.
 !!! error TS2322:   Call signature return types 'AsyncGenerator<string, void, undefined>' and 'AsyncIterableIterator<number>' are incompatible.
-!!! error TS2322:     The types returned by 'next(...)' are incompatible between these types.
-!!! error TS2322:       Type 'Promise<IteratorResult<string, void>>' is not assignable to type 'Promise<IteratorResult<number, any>>'.
-!!! error TS2322:         Type 'IteratorResult<string, void>' is not assignable to type 'IteratorResult<number, any>'.
-!!! error TS2322:           Type 'IteratorYieldResult<string>' is not assignable to type 'IteratorResult<number, any>'.
-!!! error TS2322:             Type 'IteratorYieldResult<string>' is not assignable to type 'IteratorYieldResult<number>'.
-!!! error TS2322:               Type 'string' is not assignable to type 'number'.
+!!! error TS2322:     The types of 'next(...).then' are incompatible between these types.
+!!! error TS2322:       Type '<TResult1 = IteratorResult<string, void>, TResult2 = never>(onfulfilled?: (value: IteratorResult<string, void>) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>' is not assignable to type '<TResult1 = IteratorResult<number, any>, TResult2 = never>(onfulfilled?: (value: IteratorResult<number, any>) => TResult1 | PromiseLike<TResult1>, onrejected?: (reason: any) => TResult2 | PromiseLike<TResult2>) => Promise<TResult1 | TResult2>'.
+!!! error TS2322:         Types of parameters 'onfulfilled' and 'onfulfilled' are incompatible.
+!!! error TS2322:           Types of parameters 'value' and 'value' are incompatible.
+!!! error TS2322:             Type 'IteratorResult<string, void>' is not assignable to type 'IteratorResult<number, any>'.
+!!! error TS2322:               Type 'IteratorYieldResult<string>' is not assignable to type 'IteratorResult<number, any>'.
+!!! error TS2322:                 Type 'IteratorYieldResult<string>' is not assignable to type 'IteratorYieldResult<number>'.
+!!! error TS2322:                   Type 'string' is not assignable to type 'number'.
         yield "a";
     };
     const assignability2: () => AsyncIterableIterator<number> = async function * () {
diff --git a/tests/baselines/reference/varianceMeasurement.errors.txt b/tests/baselines/reference/varianceMeasurement.errors.txt
index eb77b28564669..523a0d9457a27 100644
--- a/tests/baselines/reference/varianceMeasurement.errors.txt
+++ b/tests/baselines/reference/varianceMeasurement.errors.txt
@@ -1,5 +1,11 @@
 tests/cases/compiler/varianceMeasurement.ts(10,7): error TS2322: Type 'Foo1<string>' is not assignable to type 'Foo1<"a">'.
-  Type 'string' is not assignable to type '"a"'.
+  Types of property 'x' are incompatible.
+    Type 'string' is not assignable to type '"a"'.
+tests/cases/compiler/varianceMeasurement.ts(11,7): error TS2322: Type 'Foo1<string>' is not assignable to type 'Foo1<unknown>'.
+  The types of 'y.x' are incompatible between these types.
+    Type '(arg: string) => void' is not assignable to type '(arg: unknown) => void'.
+      Types of parameters 'arg' and 'arg' are incompatible.
+        Type 'unknown' is not assignable to type 'string'.
 tests/cases/compiler/varianceMeasurement.ts(21,7): error TS2322: Type 'Foo2<string>' is not assignable to type 'Foo2<"a">'.
   Types of property 'x' are incompatible.
     Type 'string' is not assignable to type '"a"'.
@@ -9,7 +15,13 @@ tests/cases/compiler/varianceMeasurement.ts(22,7): error TS2322: Type 'Foo2<stri
       Types of parameters 'arg' and 'arg' are incompatible.
         Type 'unknown' is not assignable to type 'string'.
 tests/cases/compiler/varianceMeasurement.ts(33,7): error TS2322: Type 'Foo3<string>' is not assignable to type 'Foo3<"a">'.
-  Type 'string' is not assignable to type '"a"'.
+  Types of property 'x' are incompatible.
+    Type 'string' is not assignable to type '"a"'.
+tests/cases/compiler/varianceMeasurement.ts(34,7): error TS2322: Type 'Foo3<string>' is not assignable to type 'Foo3<unknown>'.
+  The types of 'y.x' are incompatible between these types.
+    Type '(arg: string) => void' is not assignable to type '(arg: unknown) => void'.
+      Types of parameters 'arg' and 'arg' are incompatible.
+        Type 'unknown' is not assignable to type 'string'.
 tests/cases/compiler/varianceMeasurement.ts(44,7): error TS2322: Type 'Foo4<string>' is not assignable to type 'Foo4<"a">'.
   Types of property 'x' are incompatible.
     Type 'string' is not assignable to type '"a"'.
@@ -19,12 +31,15 @@ tests/cases/compiler/varianceMeasurement.ts(45,7): error TS2322: Type 'Foo4<stri
       Types of parameters 'arg' and 'arg' are incompatible.
         Type 'unknown' is not assignable to type 'string'.
 tests/cases/compiler/varianceMeasurement.ts(57,7): error TS2322: Type 'Fn<string, number>' is not assignable to type 'Fn<unknown, number>'.
-  Type 'unknown' is not assignable to type 'string'.
+  The types returned by 'then(...)' are incompatible between these types.
+    Type 'Fn<string, any>' is not assignable to type 'Fn<unknown, any>'.
+      Types of parameters 'a' and 'a' are incompatible.
+        Type 'unknown' is not assignable to type 'string'.
 tests/cases/compiler/varianceMeasurement.ts(62,7): error TS2322: Type 'Fn<string, number>' is not assignable to type 'Fn<string, 0>'.
   Type 'number' is not assignable to type '0'.
 
 
-==== tests/cases/compiler/varianceMeasurement.ts (8 errors) ====
+==== tests/cases/compiler/varianceMeasurement.ts (10 errors) ====
     // The type below should be invariant in T but is measured as covariant because
     // we don't analyze recursive references.
     
@@ -37,8 +52,15 @@ tests/cases/compiler/varianceMeasurement.ts(62,7): error TS2322: Type 'Fn<string
     const f11: Foo1<'a'> = f10;
           ~~~
 !!! error TS2322: Type 'Foo1<string>' is not assignable to type 'Foo1<"a">'.
-!!! error TS2322:   Type 'string' is not assignable to type '"a"'.
+!!! error TS2322:   Types of property 'x' are incompatible.
+!!! error TS2322:     Type 'string' is not assignable to type '"a"'.
     const f12: Foo1<unknown> = f10;
+          ~~~
+!!! error TS2322: Type 'Foo1<string>' is not assignable to type 'Foo1<unknown>'.
+!!! error TS2322:   The types of 'y.x' are incompatible between these types.
+!!! error TS2322:     Type '(arg: string) => void' is not assignable to type '(arg: unknown) => void'.
+!!! error TS2322:       Types of parameters 'arg' and 'arg' are incompatible.
+!!! error TS2322:         Type 'unknown' is not assignable to type 'string'.
     
     // The type below is invariant in T and is measured as such.
     
@@ -73,8 +95,15 @@ tests/cases/compiler/varianceMeasurement.ts(62,7): error TS2322: Type 'Fn<string
     const f31: Foo3<'a'> = f30;
           ~~~
 !!! error TS2322: Type 'Foo3<string>' is not assignable to type 'Foo3<"a">'.
-!!! error TS2322:   Type 'string' is not assignable to type '"a"'.
+!!! error TS2322:   Types of property 'x' are incompatible.
+!!! error TS2322:     Type 'string' is not assignable to type '"a"'.
     const f32: Foo3<unknown> = f30;
+          ~~~
+!!! error TS2322: Type 'Foo3<string>' is not assignable to type 'Foo3<unknown>'.
+!!! error TS2322:   The types of 'y.x' are incompatible between these types.
+!!! error TS2322:     Type '(arg: string) => void' is not assignable to type '(arg: unknown) => void'.
+!!! error TS2322:       Types of parameters 'arg' and 'arg' are incompatible.
+!!! error TS2322:         Type 'unknown' is not assignable to type 'string'.
     
     // The type below is invariant in T and is measured as such.
     
@@ -110,7 +139,10 @@ tests/cases/compiler/varianceMeasurement.ts(62,7): error TS2322: Type 'Fn<string
     const fn1: Fn<unknown, number> = fn;  // Error
           ~~~
 !!! error TS2322: Type 'Fn<string, number>' is not assignable to type 'Fn<unknown, number>'.
-!!! error TS2322:   Type 'unknown' is not assignable to type 'string'.
+!!! error TS2322:   The types returned by 'then(...)' are incompatible between these types.
+!!! error TS2322:     Type 'Fn<string, any>' is not assignable to type 'Fn<unknown, any>'.
+!!! error TS2322:       Types of parameters 'a' and 'a' are incompatible.
+!!! error TS2322:         Type 'unknown' is not assignable to type 'string'.
     const fn2: Fn<'a', number> = fn;
     
     // Covariant in B
diff --git a/tests/cases/compiler/complexClassStructureNoCrash.ts b/tests/cases/compiler/complexClassStructureNoCrash.ts
new file mode 100644
index 0000000000000..58f3fd1ef8656
--- /dev/null
+++ b/tests/cases/compiler/complexClassStructureNoCrash.ts
@@ -0,0 +1,236 @@
+// @target: esnext
+const { assign } = Object
+
+export type Name = string
+export type List<T> = ReadonlyArray<T>
+export type Payload<T> = Record<string, unknown>
+
+export type Stage = Raw | Filled | Linked
+export abstract class Raw { protected readonly rawTag = 'Raw' }
+export abstract class Filled extends Raw { protected readonly filledTag = 'Filled' }
+export abstract class Linked extends Filled { protected readonly linkedTag = 'Linked' }
+export type Final = Linked
+
+type Stageable<S extends Stage, C extends Stage, T> = S extends C ? T : T | undefined
+export type Fillable<S extends Stage, T> = Stageable<S, Filled, T>
+export type Linkable<S extends Stage, T> = Stageable<S, Linked, T>
+
+export type Kind = Node['kind']
+export type Category = 'Entity' | 'Module' | 'Sentence' | 'Expression'
+export type NodeOfKind<K extends Kind, S extends Stage> = Extract<Node<S>, { kind: K }>
+export type NodeOfKindOrCategory<Q extends Kind | Category, S extends Stage> =
+  Q extends Kind ? NodeOfKind<Q, S> :
+  never
+
+export type Node<S extends Stage = Final>
+  = Parameter<S>
+  | NamedArgument<S>
+  | Import<S>
+  | Body<S>
+  | Catch<S>
+  | Entity<S>
+  | DescribeMember<S>
+  | ClassMember<S>
+  | Sentence<S>
+
+abstract class $Node<S extends Stage> {
+  readonly stage?: S
+  abstract readonly kind: Kind
+
+  constructor(payload: Record<string, unknown>) {
+    assign(this, payload)
+  }
+ 
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+    return this.kind === kindOrCategory
+  }
+}
+
+export class Parameter<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Parameter'
+}
+
+export class NamedArgument<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'NamedArgument'
+  readonly value!: Expression<S>
+}
+
+export class Import<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Import'
+  readonly entity!: Reference<S>
+}
+
+export class Body<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Body'
+  readonly sentences!: List<Sentence<S>>
+}
+
+export type Entity<S extends Stage = Final>
+  = Package<S>
+  | Program<S>
+  | Test<S>
+  | Describe<S>
+  | Module<S>
+  | Variable<S>
+
+
+export class Package<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Package'
+  readonly imports!: List<Import<S>>
+  readonly members!: List<Entity<S>>
+}
+
+export class Program<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Program'
+  readonly body!: Body<S>
+}
+
+export class Test<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Test'
+  readonly body!: Body<S>
+}
+
+export class Describe<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Describe'
+  readonly members!: List<DescribeMember<S>>
+
+  tests(): List<Test<S>> { return this.members.filter((member): member is Test<S> => member.is('Test')) }
+  methods(): List<Method<S>> { return this.members.filter((member): member is Method<S> => member.is('Method')) }
+  variables(): List<Variable<S>> { return this.members.filter((member): member is Variable<S> => member.is('Variable')) }
+  fixtures(): List<Fixture<S>> { return this.members.filter((member): member is Fixture<S> => member.is('Fixture')) }
+}
+
+export class Variable<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Variable'
+  readonly value!: Fillable<S, Expression<S>>
+
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+    return [this.kind, 'Sentence', 'Entity'].includes(kindOrCategory)
+  }
+}
+
+export type Module<S extends Stage = Final> = Class<S> | Singleton<S> | Mixin<S>
+
+export class Class<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Class'
+  readonly mixins!: List<Reference<S>>
+  readonly members!: List<ClassMember<S>>
+  readonly superclass!: Fillable<S, Reference<S> | null>
+}
+
+export class Singleton<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Singleton'
+  readonly mixins!: List<Reference<S>>
+  readonly members!: List<ObjectMember<S>>
+  readonly superCall!: Fillable<S, {
+    superclass: Reference<S>,
+    args: List<Expression<S>> | List<NamedArgument<S>>
+  }>
+}
+
+export class Mixin<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Mixin'
+  readonly mixins!: List<Reference<S>>
+  readonly members!: List<ObjectMember<S>>
+}
+
+export type ObjectMember<S extends Stage = Final> = Field<S> | Method<S>
+export type ClassMember<S extends Stage = Final> = Constructor<S> | ObjectMember<S>
+export type DescribeMember<S extends Stage = Final> = Variable<S> | Fixture<S> | Test<S> | Method<S>
+
+export class Field<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Field'
+  readonly value!: Fillable<S, Expression<S>>
+}
+
+export class Method<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Method'
+  readonly parameters!: List<Parameter<S>>
+  readonly body?: Body<S>
+}
+
+export class Constructor<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Constructor'
+  readonly parameters!: List<Parameter<S>>
+  readonly body!: Body<S>
+  readonly baseCall?: { callsSuper: boolean, args: List<Expression<S>> }
+}
+
+export class Fixture<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Fixture'
+  readonly body!: Body<S>
+}
+
+export type Sentence<S extends Stage = Final> = Variable<S> | Return<S> | Assignment<S> | Expression<S>
+
+export class Return<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Return'
+  readonly value?: Expression<S>
+}
+
+export class Assignment<S extends Stage = Final> extends $Node<S> {
+  readonly kind = 'Assignment'
+  readonly variable!: Reference<S>
+  readonly value!: Expression<S>
+}
+
+export type Expression<S extends Stage = Final>
+  = Reference<S>
+  | Self<S>
+  | Send<S>
+  | Super<S>
+  | New<S>
+  | If<S>
+  | Throw<S>
+  | Try<S>
+
+abstract class $Expression<S extends Stage> extends $Node<S> {
+  is<Q extends Kind | Category>(kindOrCategory: Q): this is NodeOfKindOrCategory<Q, S> {
+    return kindOrCategory === 'Expression' || super.is(kindOrCategory)
+  }
+}
+
+export class Reference<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Reference'
+  readonly name!: Name
+}
+
+export class Self<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Self'
+}
+
+export class Send<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Send'
+  readonly receiver!: Expression<S>
+  readonly message!: Name
+  readonly args!: List<Expression<S>>
+}
+
+export class Super<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Super'
+  readonly args!: List<Expression<S>>
+}
+
+export class New<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'New'
+  readonly instantiated!: Reference<S>
+  readonly args!: List<Expression<S>> | List<NamedArgument<S>>
+}
+
+export class If<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'If'
+  readonly thenBody!: Body<S>
+  readonly elseBody!: Fillable<S, Body<S>>
+}
+
+export class Throw<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Throw'
+}
+
+export class Try<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Try'
+}
+
+export class Catch<S extends Stage = Final> extends $Expression<S> {
+  readonly kind = 'Catch'
+}
\ No newline at end of file