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Merge pull request #30877 from Microsoft/fixConditionalTypeSimplification
Fix conditional type simplification
2 parents 6282645 + 06d07b0 commit 4574c7a

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5 files changed

+99
-2
lines changed

5 files changed

+99
-2
lines changed

‎src/compiler/checker.ts

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -10250,15 +10250,15 @@ namespace ts {
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function getConditionalTypeWorker(root: ConditionalRoot, mapper: TypeMapper | undefined, checkType: Type, extendsType: Type, trueType: Type, falseType: Type) {
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// Simplifications for types of the form `T extends U ? T : never` and `T extends U ? never : T`.
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if (falseType.flags & TypeFlags.Never && isTypeIdenticalTo(getActualTypeVariable(trueType), getActualTypeVariable(checkType))) {
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if (falseType.flags & TypeFlags.Never && getActualTypeVariable(trueType) === getActualTypeVariable(checkType)) {
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if (checkType.flags & TypeFlags.Any || isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
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return trueType;
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}
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else if (isIntersectionEmpty(checkType, extendsType)) { // Always false
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return neverType;
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}
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}
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else if (trueType.flags & TypeFlags.Never && isTypeIdenticalTo(getActualTypeVariable(falseType), getActualTypeVariable(checkType))) {
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else if (trueType.flags & TypeFlags.Never && getActualTypeVariable(falseType) === getActualTypeVariable(checkType)) {
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if (!(checkType.flags & TypeFlags.Any) && isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
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return neverType;
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}

‎tests/baselines/reference/conditionalTypeSimplification.js

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//// [conditionalTypeSimplification.ts]
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// Repro from #30794
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interface AbstractSchema<S, V> {
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m1<T> (v: T): SchemaType<S, Exclude<V, T>>;
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m2<T> (v: T): SchemaType<S, T>;
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}
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type SchemaType<S, V> = S extends object ? AnySchema<V> : never;
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interface AnySchema<V> extends AnySchemaType<AnySchema<undefined>, V> { }
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interface AnySchemaType<S extends AbstractSchema<any, any>, V> extends AbstractSchema<S, V> { }
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//// [conditionalTypeSimplification.js]
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// Repro from #30794

‎tests/baselines/reference/conditionalTypeSimplification.symbols

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=== tests/cases/compiler/conditionalTypeSimplification.ts ===
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// Repro from #30794
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interface AbstractSchema<S, V> {
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>AbstractSchema : Symbol(AbstractSchema, Decl(conditionalTypeSimplification.ts, 0, 0))
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>S : Symbol(S, Decl(conditionalTypeSimplification.ts, 2, 25))
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>V : Symbol(V, Decl(conditionalTypeSimplification.ts, 2, 27))
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m1<T> (v: T): SchemaType<S, Exclude<V, T>>;
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>m1 : Symbol(AbstractSchema.m1, Decl(conditionalTypeSimplification.ts, 2, 32))
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>T : Symbol(T, Decl(conditionalTypeSimplification.ts, 3, 5))
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>v : Symbol(v, Decl(conditionalTypeSimplification.ts, 3, 9))
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>T : Symbol(T, Decl(conditionalTypeSimplification.ts, 3, 5))
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>SchemaType : Symbol(SchemaType, Decl(conditionalTypeSimplification.ts, 5, 1))
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>S : Symbol(S, Decl(conditionalTypeSimplification.ts, 2, 25))
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>Exclude : Symbol(Exclude, Decl(lib.es5.d.ts, --, --))
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>V : Symbol(V, Decl(conditionalTypeSimplification.ts, 2, 27))
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>T : Symbol(T, Decl(conditionalTypeSimplification.ts, 3, 5))
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m2<T> (v: T): SchemaType<S, T>;
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>m2 : Symbol(AbstractSchema.m2, Decl(conditionalTypeSimplification.ts, 3, 45))
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>T : Symbol(T, Decl(conditionalTypeSimplification.ts, 4, 5))
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>v : Symbol(v, Decl(conditionalTypeSimplification.ts, 4, 9))
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>T : Symbol(T, Decl(conditionalTypeSimplification.ts, 4, 5))
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>SchemaType : Symbol(SchemaType, Decl(conditionalTypeSimplification.ts, 5, 1))
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>S : Symbol(S, Decl(conditionalTypeSimplification.ts, 2, 25))
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>T : Symbol(T, Decl(conditionalTypeSimplification.ts, 4, 5))
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}
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type SchemaType<S, V> = S extends object ? AnySchema<V> : never;
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>SchemaType : Symbol(SchemaType, Decl(conditionalTypeSimplification.ts, 5, 1))
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>S : Symbol(S, Decl(conditionalTypeSimplification.ts, 7, 16))
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>V : Symbol(V, Decl(conditionalTypeSimplification.ts, 7, 18))
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>S : Symbol(S, Decl(conditionalTypeSimplification.ts, 7, 16))
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>AnySchema : Symbol(AnySchema, Decl(conditionalTypeSimplification.ts, 7, 64))
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>V : Symbol(V, Decl(conditionalTypeSimplification.ts, 7, 18))
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interface AnySchema<V> extends AnySchemaType<AnySchema<undefined>, V> { }
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>AnySchema : Symbol(AnySchema, Decl(conditionalTypeSimplification.ts, 7, 64))
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>V : Symbol(V, Decl(conditionalTypeSimplification.ts, 8, 20))
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>AnySchemaType : Symbol(AnySchemaType, Decl(conditionalTypeSimplification.ts, 8, 73))
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>AnySchema : Symbol(AnySchema, Decl(conditionalTypeSimplification.ts, 7, 64))
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>V : Symbol(V, Decl(conditionalTypeSimplification.ts, 8, 20))
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interface AnySchemaType<S extends AbstractSchema<any, any>, V> extends AbstractSchema<S, V> { }
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>AnySchemaType : Symbol(AnySchemaType, Decl(conditionalTypeSimplification.ts, 8, 73))
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>S : Symbol(S, Decl(conditionalTypeSimplification.ts, 9, 24))
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>AbstractSchema : Symbol(AbstractSchema, Decl(conditionalTypeSimplification.ts, 0, 0))
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>V : Symbol(V, Decl(conditionalTypeSimplification.ts, 9, 59))
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>AbstractSchema : Symbol(AbstractSchema, Decl(conditionalTypeSimplification.ts, 0, 0))
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>S : Symbol(S, Decl(conditionalTypeSimplification.ts, 9, 24))
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>V : Symbol(V, Decl(conditionalTypeSimplification.ts, 9, 59))
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‎tests/baselines/reference/conditionalTypeSimplification.types

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=== tests/cases/compiler/conditionalTypeSimplification.ts ===
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// Repro from #30794
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interface AbstractSchema<S, V> {
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m1<T> (v: T): SchemaType<S, Exclude<V, T>>;
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>m1 : <T>(v: T) => SchemaType<S, Exclude<V, T>>
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>v : T
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m2<T> (v: T): SchemaType<S, T>;
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>m2 : <T>(v: T) => SchemaType<S, T>
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>v : T
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}
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type SchemaType<S, V> = S extends object ? AnySchema<V> : never;
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>SchemaType : SchemaType<S, V>
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interface AnySchema<V> extends AnySchemaType<AnySchema<undefined>, V> { }
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interface AnySchemaType<S extends AbstractSchema<any, any>, V> extends AbstractSchema<S, V> { }
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‎tests/cases/compiler/conditionalTypeSimplification.ts

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// Repro from #30794
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interface AbstractSchema<S, V> {
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m1<T> (v: T): SchemaType<S, Exclude<V, T>>;
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m2<T> (v: T): SchemaType<S, T>;
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}
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type SchemaType<S, V> = S extends object ? AnySchema<V> : never;
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interface AnySchema<V> extends AnySchemaType<AnySchema<undefined>, V> { }
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interface AnySchemaType<S extends AbstractSchema<any, any>, V> extends AbstractSchema<S, V> { }

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