Instantiate original target type in substituteIndexedMappedType (#49205)

ahejlsberg · web-flow · commit c592ee781db6 · 2022-05-23T11:07:33.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -15798,7 +15798,7 @@ namespace ts {
         function substituteIndexedMappedType(objectType: MappedType, index: Type) {
             const mapper = createTypeMapper([getTypeParameterFromMappedType(objectType)], [index]);
             const templateMapper = combineTypeMappers(objectType.mapper, mapper);
-            return instantiateType(getTemplateTypeFromMappedType(objectType), templateMapper);
+            return instantiateType(getTemplateTypeFromMappedType(objectType.target as MappedType || objectType), templateMapper);
         }
 
         function getIndexedAccessType(objectType: Type, indexType: Type, accessFlags = AccessFlags.None, accessNode?: ElementAccessExpression | IndexedAccessTypeNode | PropertyName | BindingName | SyntheticExpression, aliasSymbol?: Symbol, aliasTypeArguments?: readonly Type[]): Type {

Original file line number	Diff line number	Diff line change
`@@ -15798,7 +15798,7 @@ namespace ts {`
`15798`	`15798`	`function substituteIndexedMappedType(objectType: MappedType, index: Type) {`
`15799`	`15799`	`const mapper = createTypeMapper([getTypeParameterFromMappedType(objectType)], [index]);`
`15800`	`15800`	`const templateMapper = combineTypeMappers(objectType.mapper, mapper);`
`15801`		`- return instantiateType(getTemplateTypeFromMappedType(objectType), templateMapper);`
	`15801`	`+ return instantiateType(getTemplateTypeFromMappedType(objectType.target as MappedType \|\| objectType), templateMapper);`
`15802`	`15802`	`}`
`15803`	`15803`
`15804`	`15804`	`function getIndexedAccessType(objectType: Type, indexType: Type, accessFlags = AccessFlags.None, accessNode?: ElementAccessExpression \| IndexedAccessTypeNode \| PropertyName \| BindingName \| SyntheticExpression, aliasSymbol?: Symbol, aliasTypeArguments?: readonly Type[]): Type {`