Merge pull request #13234 from Microsoft/fixMappedTypeInstantiation

Fix mapped type instantiation

Author: ahejlsberg

src/compiler/checker.ts

@@ -6652,17 +6652,19 @@ namespace ts {
             const constraintType = getConstraintTypeFromMappedType(type);
             if (constraintType.flags & TypeFlags.Index) {
                 const typeVariable = (<IndexType>constraintType).type;
-                const mappedTypeVariable = instantiateType(typeVariable, mapper);
-                if (typeVariable !== mappedTypeVariable) {
-                    return mapType(mappedTypeVariable, t => {
-                        if (isMappableType(t)) {
-                            const replacementMapper = createUnaryTypeMapper(typeVariable, t);
-                            const combinedMapper = mapper.mappedTypes && mapper.mappedTypes.length === 1 ? replacementMapper : combineTypeMappers(replacementMapper, mapper);
-                            combinedMapper.mappedTypes = mapper.mappedTypes;
-                            return instantiateMappedObjectType(type, combinedMapper);
-                        }
-                        return t;
-                    });
+                if (typeVariable.flags & TypeFlags.TypeParameter) {
+                    const mappedTypeVariable = instantiateType(typeVariable, mapper);
+                    if (typeVariable !== mappedTypeVariable) {
+                        return mapType(mappedTypeVariable, t => {
+                            if (isMappableType(t)) {
+                                const replacementMapper = createUnaryTypeMapper(typeVariable, t);
+                                const combinedMapper = mapper.mappedTypes && mapper.mappedTypes.length === 1 ? replacementMapper : combineTypeMappers(replacementMapper, mapper);
+                                combinedMapper.mappedTypes = mapper.mappedTypes;
+                                return instantiateMappedObjectType(type, combinedMapper);
+                            }
+                            return t;
+                        });
+                    }
                 }
             }
             return instantiateMappedObjectType(type, mapper);

tests/baselines/reference/mappedTypes4.js

@@ -58,7 +58,19 @@ type DeepReadonlyFoo = {
 };
 
 var x1: DeepReadonly<Foo>;
-var x1: DeepReadonlyFoo;
+var x1: DeepReadonlyFoo;
+
+// Repro from #13232
+
+type Z = { a: number };
+type Clone<T> = {
+  [P in keyof (T & {})]: T[P];
+};
+type M = Clone<Z>; // M should be { a: number }
+
+var z1: Z;
+var z1: Clone<Z>;
+
 
 //// [mappedTypes4.js]
 function boxify(obj) {
@@ -76,6 +88,8 @@ function f1(x) {
 }
 var x1;
 var x1;
+var z1;
+var z1;
 
 
 //// [mappedTypes4.d.ts]
@@ -127,3 +141,12 @@ declare type DeepReadonlyFoo = {
 };
 declare var x1: DeepReadonly<Foo>;
 declare var x1: DeepReadonlyFoo;
+declare type Z = {
+    a: number;
+};
+declare type Clone<T> = {
+    [P in keyof (T & {})]: T[P];
+};
+declare type M = Clone<Z>;
+declare var z1: Z;
+declare var z1: Clone<Z>;

tests/baselines/reference/mappedTypes4.symbols

@@ -196,3 +196,34 @@ var x1: DeepReadonlyFoo;
 >x1 : Symbol(x1, Decl(mappedTypes4.ts, 58, 3), Decl(mappedTypes4.ts, 59, 3))
 >DeepReadonlyFoo : Symbol(DeepReadonlyFoo, Decl(mappedTypes4.ts, 50, 2))
 
+// Repro from #13232
+
+type Z = { a: number };
+>Z : Symbol(Z, Decl(mappedTypes4.ts, 59, 24))
+>a : Symbol(a, Decl(mappedTypes4.ts, 63, 10))
+
+type Clone<T> = {
+>Clone : Symbol(Clone, Decl(mappedTypes4.ts, 63, 23))
+>T : Symbol(T, Decl(mappedTypes4.ts, 64, 11))
+
+  [P in keyof (T & {})]: T[P];
+>P : Symbol(P, Decl(mappedTypes4.ts, 65, 3))
+>T : Symbol(T, Decl(mappedTypes4.ts, 64, 11))
+>T : Symbol(T, Decl(mappedTypes4.ts, 64, 11))
+>P : Symbol(P, Decl(mappedTypes4.ts, 65, 3))
+
+};
+type M = Clone<Z>; // M should be { a: number }
+>M : Symbol(M, Decl(mappedTypes4.ts, 66, 2))
+>Clone : Symbol(Clone, Decl(mappedTypes4.ts, 63, 23))
+>Z : Symbol(Z, Decl(mappedTypes4.ts, 59, 24))
+
+var z1: Z;
+>z1 : Symbol(z1, Decl(mappedTypes4.ts, 69, 3), Decl(mappedTypes4.ts, 70, 3))
+>Z : Symbol(Z, Decl(mappedTypes4.ts, 59, 24))
+
+var z1: Clone<Z>;
+>z1 : Symbol(z1, Decl(mappedTypes4.ts, 69, 3), Decl(mappedTypes4.ts, 70, 3))
+>Clone : Symbol(Clone, Decl(mappedTypes4.ts, 63, 23))
+>Z : Symbol(Z, Decl(mappedTypes4.ts, 59, 24))
+

tests/baselines/reference/mappedTypes4.types

@@ -211,3 +211,34 @@ var x1: DeepReadonlyFoo;
 >x1 : DeepReadonly<Foo>
 >DeepReadonlyFoo : DeepReadonlyFoo
 
+// Repro from #13232
+
+type Z = { a: number };
+>Z : Z
+>a : number
+
+type Clone<T> = {
+>Clone : Clone<T>
+>T : T
+
+  [P in keyof (T & {})]: T[P];
+>P : P
+>T : T
+>T : T
+>P : P
+
+};
+type M = Clone<Z>; // M should be { a: number }
+>M : Clone<Z>
+>Clone : Clone<T>
+>Z : Z
+
+var z1: Z;
+>z1 : Z
+>Z : Z
+
+var z1: Clone<Z>;
+>z1 : Z
+>Clone : Clone<T>
+>Z : Z
+

tests/cases/conformance/types/mapped/mappedTypes4.ts

@@ -59,4 +59,15 @@ type DeepReadonlyFoo = {
 };
 
 var x1: DeepReadonly<Foo>;
-var x1: DeepReadonlyFoo;
+var x1: DeepReadonlyFoo;
+
+// Repro from #13232
+
+type Z = { a: number };
+type Clone<T> = {
+  [P in keyof (T & {})]: T[P];
+};
+type M = Clone<Z>; // M should be { a: number }
+
+var z1: Z;
+var z1: Clone<Z>;