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Merge pull request microsoft#22323 from Microsoft/checkInferredConstraints
Check inferred constraints for 'infer X' type variables
2 parents 70818ae + 07ed899 commit 1192a18

7 files changed

Lines changed: 376 additions & 195 deletions

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‎src/compiler/checker.ts‎

Lines changed: 73 additions & 70 deletions
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‎src/compiler/types.ts‎

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@@ -3966,7 +3966,8 @@ namespace ts {
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/* @internal */
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export interface InferenceContext extends TypeMapper {
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signature: Signature; // Generic signature for which inferences are made
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typeParameters: TypeParameter[]; // Type parameters for which inferences are made
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signature: Signature; // Generic signature for which inferences are made (if any)
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inferences: InferenceInfo[]; // Inferences made for each type parameter
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flags: InferenceFlags; // Inference flags
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compareTypes: TypeComparer; // Type comparer function

‎tests/baselines/reference/inferTypes1.errors.txt‎

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@@ -17,7 +17,7 @@ tests/cases/conformance/types/conditional/inferTypes1.ts(75,43): error TS2304: C
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tests/cases/conformance/types/conditional/inferTypes1.ts(75,43): error TS4081: Exported type alias 'T62' has or is using private name 'U'.
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tests/cases/conformance/types/conditional/inferTypes1.ts(81,44): error TS2344: Type 'U' does not satisfy the constraint 'string'.
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Type 'number' is not assignable to type 'string'.
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tests/cases/conformance/types/conditional/inferTypes1.ts(134,40): error TS2322: Type 'T' is not assignable to type 'string'.
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tests/cases/conformance/types/conditional/inferTypes1.ts(143,40): error TS2322: Type 'T' is not assignable to type 'string'.
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==== tests/cases/conformance/types/conditional/inferTypes1.ts (16 errors) ====
@@ -144,6 +144,15 @@ tests/cases/conformance/types/conditional/inferTypes1.ts(134,40): error TS2322:
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type T77<T> = T extends T76<infer X, infer Y> ? T76<X, Y> : never;
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type T78<T> = T extends T76<infer X, infer X> ? T76<X, X> : never;
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type Foo<T extends string, U extends T> = [T, U];
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type Bar<T> = T extends Foo<infer X, infer Y> ? Foo<X, Y> : never;
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type T90 = Bar<[string, string]>; // [string, string]
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type T91 = Bar<[string, "a"]>; // [string, "a"]
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type T92 = Bar<[string, "a"] & { x: string }>; // [string, "a"]
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type T93 = Bar<["a", string]>; // never
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type T94 = Bar<[number, number]>; // never
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// Example from #21496
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type JsonifiedObject<T extends object> = { [K in keyof T]: Jsonified<T[K]> };
@@ -206,4 +215,12 @@ tests/cases/conformance/types/conditional/inferTypes1.ts(134,40): error TS2322:
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type T80 = MatchingKeys<test, void>;
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type T81 = VoidKeys<test>;
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// Repro from #22221
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type MustBeString<T extends string> = T;
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type EnsureIsString<T> = T extends MustBeString<infer U> ? U : never;
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type Test1 = EnsureIsString<"hello">; // "hello"
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type Test2 = EnsureIsString<42>; // never
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‎tests/baselines/reference/inferTypes1.js‎

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@@ -88,6 +88,15 @@ type T76<T extends T[], U extends T> = { x: T };
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type T77<T> = T extends T76<infer X, infer Y> ? T76<X, Y> : never;
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type T78<T> = T extends T76<infer X, infer X> ? T76<X, X> : never;
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type Foo<T extends string, U extends T> = [T, U];
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type Bar<T> = T extends Foo<infer X, infer Y> ? Foo<X, Y> : never;
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type T90 = Bar<[string, string]>; // [string, string]
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type T91 = Bar<[string, "a"]>; // [string, "a"]
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type T92 = Bar<[string, "a"] & { x: string }>; // [string, "a"]
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type T93 = Bar<["a", string]>; // never
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type T94 = Bar<[number, number]>; // never
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// Example from #21496
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type JsonifiedObject<T extends object> = { [K in keyof T]: Jsonified<T[K]> };
@@ -148,6 +157,14 @@ interface test {
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type T80 = MatchingKeys<test, void>;
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type T81 = VoidKeys<test>;
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// Repro from #22221
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type MustBeString<T extends string> = T;
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type EnsureIsString<T> = T extends MustBeString<infer U> ? U : never;
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type Test1 = EnsureIsString<"hello">; // "hello"
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type Test2 = EnsureIsString<42>; // never
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//// [inferTypes1.js]

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