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Perform intersection reduction before and after getApparentType (#38565)

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* Perform intersection reduction before and after getApparentType

* Add regression tests
This commit is contained in:
Anders Hejlsberg
2020-05-13 20:57:17 -07:00
committed by GitHub
parent 71711257ea
commit c1f676dd3f
6 changed files with 265 additions and 6 deletions
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20
src/compiler/checker.ts
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@@ -10202,7 +10202,7 @@ namespace ts {
}
function getPropertiesOfType(type: Type): Symbol[] {
type = getApparentType(getReducedType(type));
type = getReducedApparentType(type);
return type.flags & TypeFlags.UnionOrIntersection ?
getPropertiesOfUnionOrIntersectionType(<UnionType>type) :
getPropertiesOfObjectType(type);
@@ -10558,6 +10558,14 @@ namespace ts {
t;
}
function getReducedApparentType(type: Type): Type {
// Since getApparentType may return a non-reduced union or intersection type, we need to perform
// type reduction both before and after obtaining the apparent type. For example, given a type parameter
// 'T extends A | B', the type 'T & X' becomes 'A & X | B & X' after obtaining the apparent type, and
// that type may need futher reduction to remove empty intersections.
return getReducedType(getApparentType(getReducedType(type)));
}
function createUnionOrIntersectionProperty(containingType: UnionOrIntersectionType, name: __String): Symbol | undefined {
let singleProp: Symbol | undefined;
let propSet: Map<Symbol> | undefined;
@@ -10779,7 +10787,7 @@ namespace ts {
* @param name a name of property to look up in a given type
*/
function getPropertyOfType(type: Type, name: __String): Symbol | undefined {
type = getApparentType(getReducedType(type));
type = getReducedApparentType(type);
if (type.flags & TypeFlags.Object) {
const resolved = resolveStructuredTypeMembers(<ObjectType>type);
const symbol = resolved.members.get(name);
@@ -10817,7 +10825,7 @@ namespace ts {
* maps primitive types and type parameters are to their apparent types.
*/
function getSignaturesOfType(type: Type, kind: SignatureKind): readonly Signature[] {
return getSignaturesOfStructuredType(getApparentType(getReducedType(type)), kind);
return getSignaturesOfStructuredType(getReducedApparentType(type), kind);
}
function getIndexInfoOfStructuredType(type: Type, kind: IndexKind): IndexInfo | undefined {
@@ -10835,13 +10843,13 @@ namespace ts {
// Return the indexing info of the given kind in the given type. Creates synthetic union index types when necessary and
// maps primitive types and type parameters are to their apparent types.
function getIndexInfoOfType(type: Type, kind: IndexKind): IndexInfo | undefined {
return getIndexInfoOfStructuredType(getApparentType(getReducedType(type)), kind);
return getIndexInfoOfStructuredType(getReducedApparentType(type), kind);
}
// Return the index type of the given kind in the given type. Creates synthetic union index types when necessary and
// maps primitive types and type parameters are to their apparent types.
function getIndexTypeOfType(type: Type, kind: IndexKind): Type | undefined {
return getIndexTypeOfStructuredType(getApparentType(getReducedType(type)), kind);
return getIndexTypeOfStructuredType(getReducedApparentType(type), kind);
}
function getImplicitIndexTypeOfType(type: Type, kind: IndexKind): Type | undefined {
@@ -13215,7 +13223,7 @@ namespace ts {
// In the following we resolve T[K] to the type of the property in T selected by K.
// We treat boolean as different from other unions to improve errors;
// skipping straight to getPropertyTypeForIndexType gives errors with 'boolean' instead of 'true'.
const apparentObjectType = getApparentType(getReducedType(objectType));
const apparentObjectType = getReducedApparentType(objectType);
if (indexType.flags & TypeFlags.Union && !(indexType.flags & TypeFlags.Boolean)) {
const propTypes: Type[] = [];
let wasMissingProp = false;