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Propagate nonInferrableType in &&, || and ?? operators #38035

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Apr 20, 2020
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9 changes: 6 additions & 3 deletions src/compiler/checker.ts
Original file line number Diff line number Diff line change
Expand Up @@ -28332,15 +28332,18 @@ namespace ts {
case SyntaxKind.InKeyword:
return checkInExpression(left, right, leftType, rightType);
case SyntaxKind.AmpersandAmpersandToken:
return getTypeFacts(leftType) & TypeFacts.Truthy ?
return leftType === nonInferrableType || rightType === nonInferrableType ? nonInferrableType :
getTypeFacts(leftType) & TypeFacts.Truthy ?
getUnionType([extractDefinitelyFalsyTypes(strictNullChecks ? leftType : getBaseTypeOfLiteralType(rightType)), rightType]) :
leftType;
case SyntaxKind.BarBarToken:
return getTypeFacts(leftType) & TypeFacts.Falsy ?
return leftType === nonInferrableType || rightType === nonInferrableType ? nonInferrableType :
getTypeFacts(leftType) & TypeFacts.Falsy && leftType !== nonInferrableType ?
getUnionType([removeDefinitelyFalsyTypes(leftType), rightType], UnionReduction.Subtype) :
leftType;
case SyntaxKind.QuestionQuestionToken:
return getTypeFacts(leftType) & TypeFacts.EQUndefinedOrNull ?
return leftType === nonInferrableType || rightType === nonInferrableType ? nonInferrableType :
getTypeFacts(leftType) & TypeFacts.EQUndefinedOrNull && leftType !== nonInferrableType ?
getUnionType([getNonNullableType(leftType), rightType], UnionReduction.Subtype) :
leftType;
case SyntaxKind.EqualsToken:
Expand Down
10 changes: 10 additions & 0 deletions tests/baselines/reference/propagateNonInferrableType.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
//// [propagateNonInferrableType.ts]
declare function resolver<T>(): () => void;
declare function wrapResolver<T>(resolverFunction: () => void): void;

wrapResolver(resolver() || []);


//// [propagateNonInferrableType.js]
"use strict";
wrapResolver(resolver() || []);
14 changes: 14 additions & 0 deletions tests/baselines/reference/propagateNonInferrableType.symbols
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
=== tests/cases/compiler/propagateNonInferrableType.ts ===
declare function resolver<T>(): () => void;
>resolver : Symbol(resolver, Decl(propagateNonInferrableType.ts, 0, 0))
>T : Symbol(T, Decl(propagateNonInferrableType.ts, 0, 26))

declare function wrapResolver<T>(resolverFunction: () => void): void;
>wrapResolver : Symbol(wrapResolver, Decl(propagateNonInferrableType.ts, 0, 43))
>T : Symbol(T, Decl(propagateNonInferrableType.ts, 1, 30))
>resolverFunction : Symbol(resolverFunction, Decl(propagateNonInferrableType.ts, 1, 33))

wrapResolver(resolver() || []);
>wrapResolver : Symbol(wrapResolver, Decl(propagateNonInferrableType.ts, 0, 43))
>resolver : Symbol(resolver, Decl(propagateNonInferrableType.ts, 0, 0))

16 changes: 16 additions & 0 deletions tests/baselines/reference/propagateNonInferrableType.types
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
=== tests/cases/compiler/propagateNonInferrableType.ts ===
declare function resolver<T>(): () => void;
>resolver : <T>() => () => void

declare function wrapResolver<T>(resolverFunction: () => void): void;
>wrapResolver : <T>(resolverFunction: () => void) => void
>resolverFunction : () => void

wrapResolver(resolver() || []);
>wrapResolver(resolver() || []) : void
>wrapResolver : <T>(resolverFunction: () => void) => void
>resolver() || [] : () => void
>resolver() : () => void
>resolver : <T>() => () => void
>[] : never[]

6 changes: 6 additions & 0 deletions tests/cases/compiler/propagateNonInferrableType.ts
Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
// @strict: true

declare function resolver<T>(): () => void;
declare function wrapResolver<T>(resolverFunction: () => void): void;

wrapResolver(resolver() || []);