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Destructuring assignment removes undefined from type when default value is given #9422

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Merged
mhegazy merged 2 commits into from
Jun 30, 2016
Merged

Destructuring assignment removes undefined from type when default value is given #9422

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c5e680c
Destructuring assignment removes undefined from type when default val…
sandersn Jun 29, 2016
5f6e25c
Use checkExpression, not checkExpressionCached
sandersn Jun 30, 2016
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Destructuring assignment removes undefined from type when default val… 
…ue is given
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@sandersn
sandersn committed Jun 29, 2016
commit c5e680c8be31b0b7651e3ccb078d421e34a76e57
6 changes: 6 additions & 0 deletions src/compiler/checker.ts
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Expand Up @@ -12544,6 +12544,12 @@ namespace ts {
if (exprOrAssignment.kind === SyntaxKind.ShorthandPropertyAssignment) {
const prop = <ShorthandPropertyAssignment>exprOrAssignment;
if (prop.objectAssignmentInitializer) {
// In strict null checking mode, if a default value of a non-undefined type is specified, remove
// undefined from the final type.
if (strictNullChecks &&
!(getCombinedTypeFlags(checkExpressionCached(prop.objectAssignmentInitializer)) & TypeFlags.Undefined)) {
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@ahejlsberg ahejlsberg Jun 30, 2016

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Use checkExpression here, not checkExpressionCached. The latter should only be used (a) when you know that contextual types will never have an effect on the expression and (b) when other checks of the same expression also use the caching version. Neither are true here.

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@sandersn sandersn Jun 30, 2016

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done

sourceType = getTypeWithFacts(sourceType, TypeFacts.NEUndefined);
}
checkBinaryLikeExpression(prop.name, prop.equalsToken, prop.objectAssignmentInitializer, contextualMapper);
}
target = (<ShorthandPropertyAssignment>exprOrAssignment).name;
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11 changes: 11 additions & 0 deletions tests/baselines/reference/destructuringAssignmentWithDefault.js
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@@ -0,0 +1,11 @@
//// [destructuringAssignmentWithDefault.ts]
const a: { x?: number } = { };
let x = 0;
({x = 1} = a);


//// [destructuringAssignmentWithDefault.js]
var a = {};
var x = 0;
(_a = a.x, x = _a === void 0 ? 1 : _a, a);
var _a;
12 changes: 12 additions & 0 deletions tests/baselines/reference/destructuringAssignmentWithDefault.symbols
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@@ -0,0 +1,12 @@
=== tests/cases/compiler/destructuringAssignmentWithDefault.ts ===
const a: { x?: number } = { };
>a : Symbol(a, Decl(destructuringAssignmentWithDefault.ts, 0, 5))
>x : Symbol(x, Decl(destructuringAssignmentWithDefault.ts, 0, 10))

let x = 0;
>x : Symbol(x, Decl(destructuringAssignmentWithDefault.ts, 1, 3))

({x = 1} = a);
>x : Symbol(x, Decl(destructuringAssignmentWithDefault.ts, 2, 2))
>a : Symbol(a, Decl(destructuringAssignmentWithDefault.ts, 0, 5))

17 changes: 17 additions & 0 deletions tests/baselines/reference/destructuringAssignmentWithDefault.types
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@@ -0,0 +1,17 @@
=== tests/cases/compiler/destructuringAssignmentWithDefault.ts ===
const a: { x?: number } = { };
>a : { x?: number | undefined; }
>x : number | undefined
>{ } : {}

let x = 0;
>x : number
>0 : number

({x = 1} = a);
>({x = 1} = a) : { x?: number | undefined; }
>{x = 1} = a : { x?: number | undefined; }
>{x = 1} : { x?: number; }
>x : number
>a : { x?: number | undefined; }

4 changes: 4 additions & 0 deletions tests/cases/compiler/destructuringAssignmentWithDefault.ts
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@@ -0,0 +1,4 @@
// @strictNullChecks: true
const a: { x?: number } = { };
let x = 0;
({x = 1} = a);