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Reverse mapped types should have inferable indexes if their source had an inferable index (#33450)
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5 files changed

+140
-3
lines changed

5 files changed

+140
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lines changed

‎src/compiler/checker.ts‎

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@@ -15004,9 +15004,9 @@ namespace ts {
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* Return true if type was inferred from an object literal, written as an object type literal, or is the shape of a module
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* with no call or construct signatures.
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*/
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function isObjectTypeWithInferableIndex(type: Type) {
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return type.symbol && (type.symbol.flags & (SymbolFlags.ObjectLiteral | SymbolFlags.TypeLiteral | SymbolFlags.Enum | SymbolFlags.ValueModule)) !== 0 &&
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!typeHasCallOrConstructSignatures(type);
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function isObjectTypeWithInferableIndex(type: Type): boolean {
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return !!(type.symbol && (type.symbol.flags & (SymbolFlags.ObjectLiteral | SymbolFlags.TypeLiteral | SymbolFlags.Enum | SymbolFlags.ValueModule)) !== 0 &&
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!typeHasCallOrConstructSignatures(type)) || !!(getObjectFlags(type) & ObjectFlags.ReverseMapped && isObjectTypeWithInferableIndex((type as ReverseMappedType).source));
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}
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function createSymbolWithType(source: Symbol, type: Type | undefined) {

‎tests/baselines/reference/reverseMappedTypeAssignableToIndex.js‎

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//// [reverseMappedTypeAssignableToIndex.ts]
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// Simple mapped type and inferrence
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type Mapped<T> = { [K in keyof T]: { name: T[K] } };
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type InferFromMapped<T> = T extends Mapped<infer R> ? R : never;
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// Object literal type and associated mapped type
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// Note that in the real code we don't have a direct reference to LiteralType
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type LiteralType = {
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first: "first";
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second: "second";
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}
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type MappedLiteralType = {
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first: { name: "first" },
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second: { name: "second" },
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};
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type Inferred = InferFromMapped<MappedLiteralType>;
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// UNEXPECTED resolves to false
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type Test1 = Inferred extends Record<any, string> ? true : false;
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//// [reverseMappedTypeAssignableToIndex.js]

‎tests/baselines/reference/reverseMappedTypeAssignableToIndex.symbols‎

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=== tests/cases/compiler/reverseMappedTypeAssignableToIndex.ts ===
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// Simple mapped type and inferrence
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type Mapped<T> = { [K in keyof T]: { name: T[K] } };
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>Mapped : Symbol(Mapped, Decl(reverseMappedTypeAssignableToIndex.ts, 0, 0))
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>T : Symbol(T, Decl(reverseMappedTypeAssignableToIndex.ts, 1, 12))
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>K : Symbol(K, Decl(reverseMappedTypeAssignableToIndex.ts, 1, 20))
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>T : Symbol(T, Decl(reverseMappedTypeAssignableToIndex.ts, 1, 12))
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>name : Symbol(name, Decl(reverseMappedTypeAssignableToIndex.ts, 1, 36))
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>T : Symbol(T, Decl(reverseMappedTypeAssignableToIndex.ts, 1, 12))
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>K : Symbol(K, Decl(reverseMappedTypeAssignableToIndex.ts, 1, 20))
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type InferFromMapped<T> = T extends Mapped<infer R> ? R : never;
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>InferFromMapped : Symbol(InferFromMapped, Decl(reverseMappedTypeAssignableToIndex.ts, 1, 52))
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>T : Symbol(T, Decl(reverseMappedTypeAssignableToIndex.ts, 2, 21))
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>T : Symbol(T, Decl(reverseMappedTypeAssignableToIndex.ts, 2, 21))
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>Mapped : Symbol(Mapped, Decl(reverseMappedTypeAssignableToIndex.ts, 0, 0))
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>R : Symbol(R, Decl(reverseMappedTypeAssignableToIndex.ts, 2, 48))
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>R : Symbol(R, Decl(reverseMappedTypeAssignableToIndex.ts, 2, 48))
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// Object literal type and associated mapped type
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// Note that in the real code we don't have a direct reference to LiteralType
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type LiteralType = {
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>LiteralType : Symbol(LiteralType, Decl(reverseMappedTypeAssignableToIndex.ts, 2, 64))
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first: "first";
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>first : Symbol(first, Decl(reverseMappedTypeAssignableToIndex.ts, 6, 20))
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second: "second";
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>second : Symbol(second, Decl(reverseMappedTypeAssignableToIndex.ts, 7, 16))
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}
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type MappedLiteralType = {
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>MappedLiteralType : Symbol(MappedLiteralType, Decl(reverseMappedTypeAssignableToIndex.ts, 9, 1))
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first: { name: "first" },
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>first : Symbol(first, Decl(reverseMappedTypeAssignableToIndex.ts, 10, 26))
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>name : Symbol(name, Decl(reverseMappedTypeAssignableToIndex.ts, 11, 9))
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second: { name: "second" },
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>second : Symbol(second, Decl(reverseMappedTypeAssignableToIndex.ts, 11, 26))
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>name : Symbol(name, Decl(reverseMappedTypeAssignableToIndex.ts, 12, 10))
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};
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type Inferred = InferFromMapped<MappedLiteralType>;
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>Inferred : Symbol(Inferred, Decl(reverseMappedTypeAssignableToIndex.ts, 13, 2))
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>InferFromMapped : Symbol(InferFromMapped, Decl(reverseMappedTypeAssignableToIndex.ts, 1, 52))
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>MappedLiteralType : Symbol(MappedLiteralType, Decl(reverseMappedTypeAssignableToIndex.ts, 9, 1))
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// UNEXPECTED resolves to false
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type Test1 = Inferred extends Record<any, string> ? true : false;
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>Test1 : Symbol(Test1, Decl(reverseMappedTypeAssignableToIndex.ts, 15, 51))
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>Inferred : Symbol(Inferred, Decl(reverseMappedTypeAssignableToIndex.ts, 13, 2))
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>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
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‎tests/baselines/reference/reverseMappedTypeAssignableToIndex.types‎

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=== tests/cases/compiler/reverseMappedTypeAssignableToIndex.ts ===
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// Simple mapped type and inferrence
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type Mapped<T> = { [K in keyof T]: { name: T[K] } };
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>Mapped : Mapped<T>
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>name : T[K]
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type InferFromMapped<T> = T extends Mapped<infer R> ? R : never;
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>InferFromMapped : InferFromMapped<T>
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// Object literal type and associated mapped type
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// Note that in the real code we don't have a direct reference to LiteralType
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type LiteralType = {
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>LiteralType : LiteralType
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first: "first";
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>first : "first"
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second: "second";
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>second : "second"
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}
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type MappedLiteralType = {
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>MappedLiteralType : MappedLiteralType
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first: { name: "first" },
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>first : { name: "first"; }
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>name : "first"
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second: { name: "second" },
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>second : { name: "second"; }
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>name : "second"
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};
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type Inferred = InferFromMapped<MappedLiteralType>;
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>Inferred : { first: "first"; second: "second"; }
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// UNEXPECTED resolves to false
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type Test1 = Inferred extends Record<any, string> ? true : false;
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>Test1 : true
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>true : true
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>false : false
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‎tests/cases/compiler/reverseMappedTypeAssignableToIndex.ts‎

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// Simple mapped type and inferrence
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type Mapped<T> = { [K in keyof T]: { name: T[K] } };
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type InferFromMapped<T> = T extends Mapped<infer R> ? R : never;
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// Object literal type and associated mapped type
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// Note that in the real code we don't have a direct reference to LiteralType
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type LiteralType = {
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first: "first";
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second: "second";
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}
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type MappedLiteralType = {
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first: { name: "first" },
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second: { name: "second" },
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};
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type Inferred = InferFromMapped<MappedLiteralType>;
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// UNEXPECTED resolves to false
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type Test1 = Inferred extends Record<any, string> ? true : false;

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