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Merge pull request #30779 from Microsoft/relateDiscriminants
Relate source types covered by a target discriminated union
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‎src/compiler/checker.ts

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‎src/compiler/core.ts

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@@ -2284,4 +2284,29 @@ namespace ts {
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}
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return result;
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}
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export function cartesianProduct<T>(arrays: readonly T[][]) {
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const result: T[][] = [];
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cartesianProductWorker(arrays, result, /*outer*/ undefined, 0);
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return result;
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}
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function cartesianProductWorker<T>(arrays: readonly (readonly T[])[], result: (readonly T[])[], outer: readonly T[] | undefined, index: number) {
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for (const element of arrays[index]) {
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let inner: T[];
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if (outer) {
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inner = outer.slice();
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inner.push(element);
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}
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else {
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inner = [element];
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}
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if (index === arrays.length - 1) {
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result.push(inner);
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}
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else {
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cartesianProductWorker(arrays, result, inner, index + 1);
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}
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}
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}
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}

‎tests/baselines/reference/assignmentCompatWithDiscriminatedUnion.errors.txt

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tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts(44,5): error TS2322: Type 'S' is not assignable to type 'T'.
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Type 'S' is not assignable to type '{ a: 2; b: 3; }'.
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Types of property 'a' are incompatible.
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Type '0 | 2' is not assignable to type '2'.
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Type '0' is not assignable to type '2'.
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tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts(58,5): error TS2322: Type 'S' is not assignable to type 'T'.
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Property 'c' is missing in type 'S' but required in type '{ a: 2; b: 4 | 3; c: string; }'.
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tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts(82,5): error TS2322: Type 'S' is not assignable to type 'T'.
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Type 'S' is not assignable to type '{ a: 0 | 2 | 1; b: 0 | 2 | 1; c: 2; }'.
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Types of property 'c' are incompatible.
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Type '0 | 2 | 1' is not assignable to type '2'.
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Type '0' is not assignable to type '2'.
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==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts (3 errors) ====
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// see 'typeRelatedToDiscriminatedType' in checker.ts:
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// IteratorResult
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namespace Example1 {
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type S = { done: boolean, value: number };
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type T =
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| { done: true, value: number } // T0
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| { done: false, value: number }; // T1
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declare let s: S;
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declare let t: T;
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// S is assignable to T0 when S["done"] is true
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// S is assignable to T1 when S["done"] is false
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t = s;
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}
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// Dropping constituents of T
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namespace Example2 {
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type S = { a: 0 | 2, b: 4 };
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type T = { a: 0, b: 1 | 4 } // T0
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| { a: 1, b: 2 } // T1
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| { a: 2, b: 3 | 4 }; // T2
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declare let s: S;
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declare let t: T;
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// S is assignable to T0 when S["a"] is 0
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// S is assignable to T2 when S["a"] is 2
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t = s;
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}
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// Unmatched discriminants
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namespace Example3 {
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type S = { a: 0 | 2, b: 4 };
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type T = { a: 0, b: 1 | 4 } // T0
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| { a: 1, b: 2 | 4 } // T1
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| { a: 2, b: 3 }; // T2
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declare let s: S;
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declare let t: T;
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// S is assignable to T0 when S["a"] is 0
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// S is *not* assignable to T1 when S["b"] is 4
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// S is *not* assignable to T2 when S["a"] is 2
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t = s;
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~
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!!! error TS2322: Type 'S' is not assignable to type 'T'.
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!!! error TS2322: Type 'S' is not assignable to type '{ a: 2; b: 3; }'.
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!!! error TS2322: Types of property 'a' are incompatible.
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!!! error TS2322: Type '0 | 2' is not assignable to type '2'.
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!!! error TS2322: Type '0' is not assignable to type '2'.
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}
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// Unmatched non-discriminants
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namespace Example4 {
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type S = { a: 0 | 2, b: 4 };
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type T = { a: 0, b: 1 | 4 } // T0
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| { a: 1, b: 2 } // T1
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| { a: 2, b: 3 | 4, c: string }; // T2
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declare let s: S;
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declare let t: T;
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// S is assignable to T0 when S["a"] is 0
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// S is *not* assignable to T2 when S["a"] is 2 as S is missing "c"
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t = s;
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~
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!!! error TS2322: Type 'S' is not assignable to type 'T'.
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!!! error TS2322: Property 'c' is missing in type 'S' but required in type '{ a: 2; b: 4 | 3; c: string; }'.
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!!! related TS2728 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts:52:36: 'c' is declared here.
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}
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// Maximum discriminant combinations
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namespace Example5 {
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// NOTE: The maximum number of discriminant type combinations is currently 25.
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// 3 discriminant properties with 3 types a piece
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// is 27 possible combinations.
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type N = 0 | 1 | 2;
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type S = { a: N, b: N, c: N };
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type T = { a: 0, b: N, c: N }
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| { a: 1, b: N, c: N }
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| { a: 2, b: N, c: N }
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| { a: N, b: 0, c: N }
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| { a: N, b: 1, c: N }
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| { a: N, b: 2, c: N }
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| { a: N, b: N, c: 0 }
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| { a: N, b: N, c: 1 }
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| { a: N, b: N, c: 2 };
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declare let s: S;
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declare let t: T;
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// S *should* be assignable but the number of
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// combinations is too complex.
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t = s;
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~
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!!! error TS2322: Type 'S' is not assignable to type 'T'.
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!!! error TS2322: Type 'S' is not assignable to type '{ a: 0 | 2 | 1; b: 0 | 2 | 1; c: 2; }'.
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!!! error TS2322: Types of property 'c' are incompatible.
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!!! error TS2322: Type '0 | 2 | 1' is not assignable to type '2'.
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!!! error TS2322: Type '0' is not assignable to type '2'.
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}
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// https://github.com./Microsoft/TypeScript/issues/14865
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namespace GH14865 {
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type Style1 = {
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type: "A";
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data: string;
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} | {
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type: "B";
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data: string;
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};
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type Style2 = {
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type: "A" | "B";
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data: string;
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}
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const a: Style2 = { type: "A", data: "whatevs" };
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let b: Style1;
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a.type; // "A" | "B"
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b.type; // "A" | "B"
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b = a; // should be assignable
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}
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// https://github.com./Microsoft/TypeScript/issues/30170
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namespace GH30170 {
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interface Blue {
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color: 'blue'
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}
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interface Yellow {
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color?: 'yellow',
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}
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function draw(val: Blue | Yellow) { }
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function drawWithColor(currentColor: 'blue' | 'yellow' | undefined) {
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return draw({ color: currentColor });
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}
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}
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// https://github.com./Microsoft/TypeScript/issues/12052
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namespace GH12052 {
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interface ILinearAxis { type: "linear"; }
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interface ICategoricalAxis { type: "categorical"; }
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type IAxis = ILinearAxis | ICategoricalAxis;
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type IAxisType = "linear" | "categorical";
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function getAxisType(): IAxisType {
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if (1 == 1) {
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return "categorical";
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} else {
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return "linear";
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}
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}
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const bad: IAxis = { type: getAxisType() };
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const good: IAxis = { type: undefined };
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good.type = getAxisType();
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}
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// https://github.com./Microsoft/TypeScript/issues/18421
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namespace GH18421 {
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interface ThingTypeOne {
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type: 'one';
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}
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interface ThingTypeTwo {
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type: 'two';
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}
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type ThingType = 'one' | 'two';
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type Thing = ThingTypeOne | ThingTypeTwo;
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function makeNewThing(thingType: ThingType): Thing {
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return {
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type: thingType
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};
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}
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}
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// https://github.com./Microsoft/TypeScript/issues/15907
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namespace GH15907 {
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type Action = { type: 'activate' } | { type: 'disactivate' };
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function dispatchAction(action: Action): void {
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}
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const active = true;
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dispatchAction({ type : (active? 'disactivate' : 'activate') });
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}
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// https://github.com./Microsoft/TypeScript/issues/20889
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namespace GH20889 {
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interface A1 {
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type: "A1";
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}
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interface A2 {
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type: "A2";
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}
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type AU = A1 | A2;
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function foo(obj1: AU) {
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const obj2: AU = {
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type: obj1.type
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};
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}
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}

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