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Map over unions when getting iterated element type from contextual type #40592

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Merged
merged 1 commit into from
Sep 17, 2020
Merged

Map over unions when getting iterated element type from contextual type #40592

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5 changes: 4 additions & 1 deletion src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -23651,7 +23651,10 @@ namespace ts {
function getContextualTypeForElementExpression(arrayContextualType: Type | undefined, index: number): Type | undefined {
return arrayContextualType && (
getTypeOfPropertyOfContextualType(arrayContextualType, "" + index as __String)
|| getIteratedTypeOrElementType(IterationUse.Element, arrayContextualType, undefinedType, /*errorNode*/ undefined, /*checkAssignability*/ false));
|| mapType(
arrayContextualType,
t => getIteratedTypeOrElementType(IterationUse.Element, t, undefinedType, /*errorNode*/ undefined, /*checkAssignability*/ false),
/*noReductions*/ true));
}

// In a contextually typed conditional expression, the true/false expressions are contextually typed by the same type.
Expand Down
17 changes: 17 additions & 0 deletions tests/baselines/reference/contextualTypeIterableUnions.js
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@@ -0,0 +1,17 @@
//// [contextualTypeIterableUnions.ts]
declare class DMap<K, V> {
constructor(iterable: Iterable<[K, V]> | undefined);
}
new DMap([["1", 2]]);

const i1: Iterable<{ a: true }> | undefined = [{ a: true }];
const i2: Iterable<{ a: true }> | Iterable<{ b: false }> = [{ b: false }];
const i3: Iterable<number> | 1[] = [2];


//// [contextualTypeIterableUnions.js]
"use strict";
new DMap([["1", 2]]);
const i1 = [{ a: true }];
const i2 = [{ b: false }];
const i3 = [2];
33 changes: 33 additions & 0 deletions tests/baselines/reference/contextualTypeIterableUnions.symbols
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@@ -0,0 +1,33 @@
=== tests/cases/compiler/contextualTypeIterableUnions.ts ===
declare class DMap<K, V> {
>DMap : Symbol(DMap, Decl(contextualTypeIterableUnions.ts, 0, 0))
>K : Symbol(K, Decl(contextualTypeIterableUnions.ts, 0, 19))
>V : Symbol(V, Decl(contextualTypeIterableUnions.ts, 0, 21))

constructor(iterable: Iterable<[K, V]> | undefined);
>iterable : Symbol(iterable, Decl(contextualTypeIterableUnions.ts, 1, 14))
>Iterable : Symbol(Iterable, Decl(lib.es2015.iterable.d.ts, --, --))
>K : Symbol(K, Decl(contextualTypeIterableUnions.ts, 0, 19))
>V : Symbol(V, Decl(contextualTypeIterableUnions.ts, 0, 21))
}
new DMap([["1", 2]]);
>DMap : Symbol(DMap, Decl(contextualTypeIterableUnions.ts, 0, 0))

const i1: Iterable<{ a: true }> | undefined = [{ a: true }];
>i1 : Symbol(i1, Decl(contextualTypeIterableUnions.ts, 5, 5))
>Iterable : Symbol(Iterable, Decl(lib.es2015.iterable.d.ts, --, --))
>a : Symbol(a, Decl(contextualTypeIterableUnions.ts, 5, 20))
>a : Symbol(a, Decl(contextualTypeIterableUnions.ts, 5, 48))

const i2: Iterable<{ a: true }> | Iterable<{ b: false }> = [{ b: false }];
>i2 : Symbol(i2, Decl(contextualTypeIterableUnions.ts, 6, 5))
>Iterable : Symbol(Iterable, Decl(lib.es2015.iterable.d.ts, --, --))
>a : Symbol(a, Decl(contextualTypeIterableUnions.ts, 6, 20))
>Iterable : Symbol(Iterable, Decl(lib.es2015.iterable.d.ts, --, --))
>b : Symbol(b, Decl(contextualTypeIterableUnions.ts, 6, 44))
>b : Symbol(b, Decl(contextualTypeIterableUnions.ts, 6, 61))

const i3: Iterable<number> | 1[] = [2];
>i3 : Symbol(i3, Decl(contextualTypeIterableUnions.ts, 7, 5))
>Iterable : Symbol(Iterable, Decl(lib.es2015.iterable.d.ts, --, --))

40 changes: 40 additions & 0 deletions tests/baselines/reference/contextualTypeIterableUnions.types
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=== tests/cases/compiler/contextualTypeIterableUnions.ts ===
declare class DMap<K, V> {
>DMap : DMap<K, V>

constructor(iterable: Iterable<[K, V]> | undefined);
>iterable : Iterable<[K, V]> | undefined
}
new DMap([["1", 2]]);
>new DMap([["1", 2]]) : DMap<string, number>
>DMap : typeof DMap
>[["1", 2]] : [string, number][]
>["1", 2] : [string, number]
>"1" : "1"
>2 : 2

const i1: Iterable<{ a: true }> | undefined = [{ a: true }];
>i1 : Iterable<{ a: true; }> | undefined
>a : true
>true : true
>[{ a: true }] : { a: true; }[]
>{ a: true } : { a: true; }
>a : true
>true : true

const i2: Iterable<{ a: true }> | Iterable<{ b: false }> = [{ b: false }];
>i2 : Iterable<{ a: true; }> | Iterable<{ b: false; }>
>a : true
>true : true
>b : false
>false : false
>[{ b: false }] : { b: false; }[]
>{ b: false } : { b: false; }
>b : false
>false : false

const i3: Iterable<number> | 1[] = [2];
>i3 : Iterable<number> | 1[]
>[2] : 2[]
>2 : 2

11 changes: 11 additions & 0 deletions tests/cases/compiler/contextualTypeIterableUnions.ts
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// @strict: true
// @target: esnext

declare class DMap<K, V> {
constructor(iterable: Iterable<[K, V]> | undefined);
}
new DMap([["1", 2]]);

const i1: Iterable<{ a: true }> | undefined = [{ a: true }];
const i2: Iterable<{ a: true }> | Iterable<{ b: false }> = [{ b: false }];
const i3: Iterable<number> | 1[] = [2];