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Infer non-widening literal types when type parameter constraint includes primitive types

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This commit is contained in:
Anders Hejlsberg
2018-05-21 15:28:51 -07:00
parent 153c1806d3
commit c8ac085498
1 changed files with 3 additions and 1 deletions
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src/compiler/checker.ts
+3 -1
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@@ -12777,7 +12777,9 @@ namespace ts {
const widenLiteralTypes = inference.topLevel &&
!hasPrimitiveConstraint(inference.typeParameter) &&
(inference.isFixed || !isTypeParameterAtTopLevel(getReturnTypeOfSignature(signature), inference.typeParameter));
const baseCandidates = widenLiteralTypes ? sameMap(candidates, getWidenedLiteralType) : candidates;
const baseCandidates = widenLiteralTypes ? sameMap(candidates, getWidenedLiteralType) :
hasPrimitiveConstraint(inference.typeParameter) ? sameMap(candidates, getRegularTypeOfLiteralType) :
candidates;
// If all inferences were made from contravariant positions, infer a common subtype. Otherwise, if
// union types were requested or if all inferences were made from the return type position, infer a
// union type. Otherwise, infer a common supertype.