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Support apparent types for T[K] indexed access types

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This commit is contained in:
Anders Hejlsberg
2016-11-18 13:30:56 -08:00
parent 075a3eb98f
commit 2376e30410
1 changed files with 10 additions and 1 deletions
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11
src/compiler/checker.ts
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@@ -4666,13 +4666,22 @@ namespace ts {
return type.resolvedApparentType;
}
/**
* The apparent type of an indexed access T[K] is the type of T's string index signature, if any.
*/
function getApparentTypeOfIndexedAccess(type: IndexedAccessType) {
return getIndexTypeOfType(getApparentType(type.objectType), IndexKind.String) || type;
}
/**
* For a type parameter, return the base constraint of the type parameter. For the string, number,
* boolean, and symbol primitive types, return the corresponding object types. Otherwise return the
* type itself. Note that the apparent type of a union type is the union type itself.
*/
function getApparentType(type: Type): Type {
const t = type.flags & TypeFlags.TypeParameter ? getApparentTypeOfTypeParameter(<TypeParameter>type) : type;
const t = type.flags & TypeFlags.TypeParameter ? getApparentTypeOfTypeParameter(<TypeParameter>type) :
type.flags & TypeFlags.IndexedAccess ? getApparentTypeOfIndexedAccess(<IndexedAccessType>type) :
type;
return t.flags & TypeFlags.StringLike ? globalStringType :
t.flags & TypeFlags.NumberLike ? globalNumberType :
t.flags & TypeFlags.BooleanLike ? globalBooleanType :