diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts index 981380c70de8e..4d309681bb31f 100644 --- a/src/compiler/checker.ts +++ b/src/compiler/checker.ts @@ -10783,10 +10783,32 @@ namespace ts { return type === typeParameter || type.flags & TypeFlags.UnionOrIntersection && forEach((type).types, t => isTypeParameterAtTopLevel(t, typeParameter)); } - // Infer a suitable input type for a homomorphic mapped type { [P in keyof T]: X }. We construct - // an object type with the same set of properties as the source type, where the type of each - // property is computed by inferring from the source property type to X for the type - // variable T[P] (i.e. we treat the type T[P] as the type variable we're inferring for). + /** Create an object with properties named in the string literal type. Every property has type `{}` */ + function createEmptyObjectTypeFromStringLiteral(type: Type) { + const members = createSymbolTable(); + forEachType(type, t => { + if (!(t.flags & TypeFlags.StringLiteral)) { + return; + } + const name = escapeLeadingUnderscores((t as StringLiteralType).value); + const literalProp = createSymbol(SymbolFlags.Property, name); + literalProp.type = emptyObjectType; + if (t.symbol) { + literalProp.declarations = t.symbol.declarations; + literalProp.valueDeclaration = t.symbol.valueDeclaration; + } + members.set(name, literalProp); + }); + const indexInfo = type.flags & TypeFlags.String ? createIndexInfo(emptyObjectType, /*isReadonly*/ false) : undefined; + return createAnonymousType(undefined, members, emptyArray, emptyArray, indexInfo, undefined); + } + + /** + * Infer a suitable input type for a homomorphic mapped type { [P in keyof T]: X }. We construct + * an object type with the same set of properties as the source type, where the type of each + * property is computed by inferring from the source property type to X for the type + * variable T[P] (i.e. we treat the type T[P] as the type variable we're inferring for). + */ function inferTypeForHomomorphicMappedType(source: Type, target: MappedType): Type { const properties = getPropertiesOfType(source); let indexInfo = getIndexInfoOfType(source, IndexKind.String); @@ -10942,7 +10964,15 @@ namespace ts { } } else if (source.flags & TypeFlags.Index && target.flags & TypeFlags.Index) { + priority ^= InferencePriority.Contravariant; inferFromTypes((source).type, (target).type); + priority ^= InferencePriority.Contravariant; + } + else if ((isLiteralType(source) || source.flags & TypeFlags.String) && target.flags & TypeFlags.Index) { + const empty = createEmptyObjectTypeFromStringLiteral(source); + priority ^= InferencePriority.Contravariant; + inferFromTypes(empty, (target as IndexType).type); + priority ^= InferencePriority.Contravariant; } else if (source.flags & TypeFlags.IndexedAccess && target.flags & TypeFlags.IndexedAccess) { inferFromTypes((source).objectType, (target).objectType); diff --git a/tests/baselines/reference/inferObjectTypeFromStringLiteralToKeyof.js b/tests/baselines/reference/inferObjectTypeFromStringLiteralToKeyof.js new file mode 100644 index 0000000000000..6a9a081ae6056 --- /dev/null +++ b/tests/baselines/reference/inferObjectTypeFromStringLiteralToKeyof.js @@ -0,0 +1,8 @@ +//// [inferObjectTypeFromStringLiteralToKeyof.ts] +declare function inference(target: T, name: keyof T): void; +declare var two: "a" | "d"; +inference({ a: 1, b: 2, c: 3, d(n) { return n } }, two); + + +//// [inferObjectTypeFromStringLiteralToKeyof.js] +inference({ a: 1, b: 2, c: 3, d: function (n) { return n; } }, two); diff --git a/tests/baselines/reference/inferObjectTypeFromStringLiteralToKeyof.symbols b/tests/baselines/reference/inferObjectTypeFromStringLiteralToKeyof.symbols new file mode 100644 index 0000000000000..aa3c9e89f9a42 --- /dev/null +++ b/tests/baselines/reference/inferObjectTypeFromStringLiteralToKeyof.symbols @@ -0,0 +1,22 @@ +=== tests/cases/compiler/inferObjectTypeFromStringLiteralToKeyof.ts === +declare function inference(target: T, name: keyof T): void; +>inference : Symbol(inference, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 0, 0)) +>T : Symbol(T, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 0, 27)) +>target : Symbol(target, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 0, 30)) +>T : Symbol(T, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 0, 27)) +>name : Symbol(name, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 0, 40)) +>T : Symbol(T, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 0, 27)) + +declare var two: "a" | "d"; +>two : Symbol(two, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 1, 11)) + +inference({ a: 1, b: 2, c: 3, d(n) { return n } }, two); +>inference : Symbol(inference, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 0, 0)) +>a : Symbol(a, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 2, 11)) +>b : Symbol(b, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 2, 17)) +>c : Symbol(c, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 2, 23)) +>d : Symbol(d, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 2, 29)) +>n : Symbol(n, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 2, 32)) +>n : Symbol(n, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 2, 32)) +>two : Symbol(two, Decl(inferObjectTypeFromStringLiteralToKeyof.ts, 1, 11)) + diff --git a/tests/baselines/reference/inferObjectTypeFromStringLiteralToKeyof.types b/tests/baselines/reference/inferObjectTypeFromStringLiteralToKeyof.types new file mode 100644 index 0000000000000..39c4bb84196b8 --- /dev/null +++ b/tests/baselines/reference/inferObjectTypeFromStringLiteralToKeyof.types @@ -0,0 +1,27 @@ +=== tests/cases/compiler/inferObjectTypeFromStringLiteralToKeyof.ts === +declare function inference(target: T, name: keyof T): void; +>inference : (target: T, name: keyof T) => void +>T : T +>target : T +>T : T +>name : keyof T +>T : T + +declare var two: "a" | "d"; +>two : "a" | "d" + +inference({ a: 1, b: 2, c: 3, d(n) { return n } }, two); +>inference({ a: 1, b: 2, c: 3, d(n) { return n } }, two) : void +>inference : (target: T, name: keyof T) => void +>{ a: 1, b: 2, c: 3, d(n) { return n } } : { a: number; b: number; c: number; d(n: any): any; } +>a : number +>1 : 1 +>b : number +>2 : 2 +>c : number +>3 : 3 +>d : (n: any) => any +>n : any +>n : any +>two : "a" | "d" + diff --git a/tests/cases/compiler/inferObjectTypeFromStringLiteralToKeyof.ts b/tests/cases/compiler/inferObjectTypeFromStringLiteralToKeyof.ts new file mode 100644 index 0000000000000..86acbf93a70e8 --- /dev/null +++ b/tests/cases/compiler/inferObjectTypeFromStringLiteralToKeyof.ts @@ -0,0 +1,3 @@ +declare function inference(target: T, name: keyof T): void; +declare var two: "a" | "d"; +inference({ a: 1, b: 2, c: 3, d(n) { return n } }, two);