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No union type reductions in contextual types

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This commit is contained in:
Anders Hejlsberg 2019-01-20 08:20:40 -08:00
parent 0b1da02a62
commit 60e7528ee6
1 changed files with 3 additions and 3 deletions
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6
src/compiler/checker.ts
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@ -17696,7 +17696,7 @@ namespace ts {
function getApparentTypeOfContextualType(node: Expression): Type | undefined {
const contextualType = instantiateContextualType(getContextualType(node), node);
if (contextualType) {
const apparentType = mapType(contextualType, getApparentType);
const apparentType = mapType(contextualType, getApparentType, /*noReductions*/ true);
if (apparentType.flags & TypeFlags.Union) {
if (isObjectLiteralExpression(node)) {
return discriminateContextualTypeByObjectMembers(node, apparentType as UnionType);
@ -17709,7 +17709,7 @@ namespace ts {
}
}
// If the given contextual type constains instantiable types and if a mapper representing
// If the given contextual type contains instantiable types and if a mapper representing
// return type inferences is available, instantiate those types using that mapper.
function instantiateContextualType(contextualType: Type | undefined, node: Expression): Type | undefined {
if (contextualType && maybeTypeOfKind(contextualType, TypeFlags.Instantiable)) {
@ -17721,7 +17721,7 @@ namespace ts {
return contextualType;
}
// This function is similar to instantiateType, except (a) that it only instantiates types that
// This function is similar to instantiateType, except that (a) it only instantiates types that
// are classified as instantiable (i.e. it doesn't instantiate object types), and (b) it performs
// no reductions on instantiated union types.
function instantiateInstantiableTypes(type: Type, mapper: TypeMapper): Type {