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Fixed mapped types not being considered as homomorphic with substitution constraints #63133

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Fixed mapped types not being considered as homomorphic with substitution constraints #63133

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2 changes: 1 addition & 1 deletion src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -20860,7 +20860,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}

function getHomomorphicTypeVariable(type: MappedType) {
const constraintType = getConstraintTypeFromMappedType(type);
const constraintType = getActualTypeVariable(getConstraintTypeFromMappedType(type));
if (constraintType.flags & TypeFlags.Index) {
const typeVariable = getActualTypeVariable((constraintType as IndexType).type);
if (typeVariable.flags & TypeFlags.TypeParameter) {
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39 changes: 39 additions & 0 deletions tests/baselines/reference/mappedTypeNotMistakenlyHomomorphic2.symbols
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@@ -0,0 +1,39 @@
//// [tests/cases/compiler/mappedTypeNotMistakenlyHomomorphic2.ts] ////

=== mappedTypeNotMistakenlyHomomorphic2.ts ===
// https://github.com/microsoft/TypeScript/issues/63132

type KeyMap<T> = keyof T extends PropertyKey ? { [K in keyof T]: K } : never;
>KeyMap : Symbol(KeyMap, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 0, 0))
>T : Symbol(T, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 2, 12))
>T : Symbol(T, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 2, 12))
>PropertyKey : Symbol(PropertyKey, Decl(lib.es5.d.ts, --, --))
>K : Symbol(K, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 2, 50))
>T : Symbol(T, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 2, 12))
>K : Symbol(K, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 2, 50))

type X = KeyMap<number>;
>X : Symbol(X, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 2, 77))
>KeyMap : Symbol(KeyMap, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 0, 0))

type U = { a?: number; b: string } | { b: string; readonly c: boolean };
>U : Symbol(U, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 3, 24))
>a : Symbol(a, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 5, 10))
>b : Symbol(b, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 5, 22))
>b : Symbol(b, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 5, 38))
>c : Symbol(c, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 5, 49))

type MapStringOnly<T> = keyof T extends string ? { [K in keyof T]: [T[K]] } : never;
>MapStringOnly : Symbol(MapStringOnly, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 5, 72))
>T : Symbol(T, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 6, 19))
>T : Symbol(T, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 6, 19))
>K : Symbol(K, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 6, 52))
>T : Symbol(T, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 6, 19))
>T : Symbol(T, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 6, 19))
>K : Symbol(K, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 6, 52))

type Y = MapStringOnly<U>;
>Y : Symbol(Y, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 6, 84))
>MapStringOnly : Symbol(MapStringOnly, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 5, 72))
>U : Symbol(U, Decl(mappedTypeNotMistakenlyHomomorphic2.ts, 3, 24))

33 changes: 33 additions & 0 deletions tests/baselines/reference/mappedTypeNotMistakenlyHomomorphic2.types
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//// [tests/cases/compiler/mappedTypeNotMistakenlyHomomorphic2.ts] ////

=== mappedTypeNotMistakenlyHomomorphic2.ts ===
// https://github.com/microsoft/TypeScript/issues/63132

type KeyMap<T> = keyof T extends PropertyKey ? { [K in keyof T]: K } : never;
>KeyMap : KeyMap<T>
> : ^^^^^^^^^

type X = KeyMap<number>;
>X : number
> : ^^^^^^

type U = { a?: number; b: string } | { b: string; readonly c: boolean };
>U : U
> : ^
>a : number | undefined
> : ^^^^^^^^^^^^^^^^^^
>b : string
> : ^^^^^^
>b : string
> : ^^^^^^
>c : boolean
> : ^^^^^^^

type MapStringOnly<T> = keyof T extends string ? { [K in keyof T]: [T[K]] } : never;
>MapStringOnly : MapStringOnly<T>
> : ^^^^^^^^^^^^^^^^

type Y = MapStringOnly<U>;
>Y : { a?: [number | undefined] | undefined; b: [string]; } | { b: [string]; readonly c: [boolean]; }
> : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

11 changes: 11 additions & 0 deletions tests/cases/compiler/mappedTypeNotMistakenlyHomomorphic2.ts
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@@ -0,0 +1,11 @@
// @strict: true
// @noEmit: true

// https://github.com/microsoft/TypeScript/issues/63132

type KeyMap<T> = keyof T extends PropertyKey ? { [K in keyof T]: K } : never;
type X = KeyMap<number>;

type U = { a?: number; b: string } | { b: string; readonly c: boolean };
type MapStringOnly<T> = keyof T extends string ? { [K in keyof T]: [T[K]] } : never;
type Y = MapStringOnly<U>;