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Reorder type inference cases

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This commit is contained in:
Anders Hejlsberg
2016-11-27 12:48:59 -08:00
parent 0a1a3eced4
commit ecd10be177
1 changed files with 13 additions and 13 deletions
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26
src/compiler/checker.ts
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@@ -8668,11 +8668,14 @@ namespace ts {
function inferFromObjectTypes(source: Type, target: Type) {
if (getObjectFlags(target) & ObjectFlags.Mapped) {
const constraintType = getConstraintTypeFromMappedType(<MappedType>target);
if (getObjectFlags(source) & ObjectFlags.Mapped) {
// We're inferring from a mapped type to a mapped type, so simply infer from constraint type to
// constraint type and from template type to template type.
inferFromTypes(getConstraintTypeFromMappedType(<MappedType>source), constraintType);
inferFromTypes(getTemplateTypeFromMappedType(<MappedType>source), getTemplateTypeFromMappedType(<MappedType>target));
if (constraintType.flags & TypeFlags.Index) {
// We're inferring from some source type S to an isomorphic mapped type { [P in keyof T]: X },
// where T is a type parameter. Use inferTypeForIsomorphicMappedType to infer a suitable source
// type and then infer from that type to T.
const index = indexOf(typeParameters, (<IndexType>constraintType).type);
if (index >= 0 && !typeInferences[index].isFixed) {
inferFromTypes(inferTypeForIsomorphicMappedType(source, <MappedType>target), typeParameters[index]);
}
return;
}
if (constraintType.flags & TypeFlags.TypeParameter) {
@@ -8682,14 +8685,11 @@ namespace ts {
inferFromTypes(getUnionType(map(getPropertiesOfType(source), getTypeOfSymbol)), getTemplateTypeFromMappedType(<MappedType>target));
return;
}
if (constraintType.flags & TypeFlags.Index) {
// We're inferring from some source type S to an isomorphic mapped type { [P in keyof T]: X },
// where T is a type parameter. Use inferTypeForIsomorphicMappedType to infer a suitable source
// type and then infer from that type to T.
const index = indexOf(typeParameters, (<IndexType>constraintType).type);
if (index >= 0 && !typeInferences[index].isFixed) {
inferFromTypes(inferTypeForIsomorphicMappedType(source, <MappedType>target), typeParameters[index]);
}
if (getObjectFlags(source) & ObjectFlags.Mapped) {
// We're inferring from a mapped type to a mapped type, so simply infer from constraint type to
// constraint type and from template type to template type.
inferFromTypes(getConstraintTypeFromMappedType(<MappedType>source), constraintType);
inferFromTypes(getTemplateTypeFromMappedType(<MappedType>source), getTemplateTypeFromMappedType(<MappedType>target));
return;
}
}