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Make 'keyof T' a literal contextual type #12480

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Nov 25, 2016
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2 changes: 1 addition & 1 deletion src/compiler/checker.ts
Original file line number Diff line number Diff line change
Expand Up @@ -14870,7 +14870,7 @@ namespace ts {
}
contextualType = apparentType;
}
return maybeTypeOfKind(contextualType, TypeFlags.Literal);
return maybeTypeOfKind(contextualType, (TypeFlags.Literal | TypeFlags.Index));
}
return false;
}
Expand Down
32 changes: 32 additions & 0 deletions tests/baselines/reference/keyofIsLiteralContexualType.errors.txt
Original file line number Diff line number Diff line change
@@ -0,0 +1,32 @@
tests/cases/compiler/keyofIsLiteralContexualType.ts(5,9): error TS2322: Type '("a" | "b" | "c")[]' is not assignable to type 'keyof T[]'.
Type '"a" | "b" | "c"' is not assignable to type 'keyof T'.
Type '"a" | "b" | "c"' is not assignable to type '"a" | "b"'.
Type '"c"' is not assignable to type '"a" | "b"'.
Type '"c"' is not assignable to type 'keyof T'.
Type '"c"' is not assignable to type '"a" | "b"'.
tests/cases/compiler/keyofIsLiteralContexualType.ts(13,11): error TS2339: Property 'b' does not exist on type 'Pick<{ a: number; b: number; c: number; }, "a" | "c">'.


==== tests/cases/compiler/keyofIsLiteralContexualType.ts (2 errors) ====
// keyof T is a literal contextual type

function foo<T extends { a: string, b: string }>() {
let a: (keyof T)[] = ["a", "b"];
let b: (keyof T)[] = ["a", "b", "c"];
~
!!! error TS2322: Type '("a" | "b" | "c")[]' is not assignable to type 'keyof T[]'.
!!! error TS2322: Type '"a" | "b" | "c"' is not assignable to type 'keyof T'.
!!! error TS2322: Type '"a" | "b" | "c"' is not assignable to type '"a" | "b"'.
!!! error TS2322: Type '"c"' is not assignable to type '"a" | "b"'.
!!! error TS2322: Type '"c"' is not assignable to type 'keyof T'.
!!! error TS2322: Type '"c"' is not assignable to type '"a" | "b"'.
}

// Repro from #12455

declare function pick<T, K extends keyof T>(obj: T, propNames: K[]): Pick<T, K>;

let x = pick({ a: 10, b: 20, c: 30 }, ["a", "c"]);
let b = x.b; // Error
~
!!! error TS2339: Property 'b' does not exist on type 'Pick<{ a: number; b: number; c: number; }, "a" | "c">'.
23 changes: 23 additions & 0 deletions tests/baselines/reference/keyofIsLiteralContexualType.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
//// [keyofIsLiteralContexualType.ts]
// keyof T is a literal contextual type

function foo<T extends { a: string, b: string }>() {
let a: (keyof T)[] = ["a", "b"];
let b: (keyof T)[] = ["a", "b", "c"];
}

// Repro from #12455

declare function pick<T, K extends keyof T>(obj: T, propNames: K[]): Pick<T, K>;

let x = pick({ a: 10, b: 20, c: 30 }, ["a", "c"]);
let b = x.b; // Error

//// [keyofIsLiteralContexualType.js]
// keyof T is a literal contextual type
function foo() {
var a = ["a", "b"];
var b = ["a", "b", "c"];
}
var x = pick({ a: 10, b: 20, c: 30 }, ["a", "c"]);
var b = x.b; // Error
13 changes: 13 additions & 0 deletions tests/cases/compiler/keyofIsLiteralContexualType.ts
Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
// keyof T is a literal contextual type

function foo<T extends { a: string, b: string }>() {
let a: (keyof T)[] = ["a", "b"];
let b: (keyof T)[] = ["a", "b", "c"];
}

// Repro from #12455

declare function pick<T, K extends keyof T>(obj: T, propNames: K[]): Pick<T, K>;

let x = pick({ a: 10, b: 20, c: 30 }, ["a", "c"]);
let b = x.b; // Error