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Higher order inference for mapped, index and lookup types

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This commit is contained in:
Anders Hejlsberg 2017-09-11 10:24:27 -07:00
parent eb80799ef0
commit 63d746bc4c
1 changed files with 14 additions and 1 deletions
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15
src/compiler/checker.ts
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@ -10386,7 +10386,7 @@ namespace ts {
// results for union and intersection types for performance reasons.
function couldContainTypeVariables(type: Type): boolean {
const objectFlags = getObjectFlags(type);
return !!(type.flags & TypeFlags.TypeVariable ||
return !!(type.flags & (TypeFlags.TypeVariable | TypeFlags.Index) ||
objectFlags & ObjectFlags.Reference && forEach((<TypeReference>type).typeArguments, couldContainTypeVariables) ||
objectFlags & ObjectFlags.Anonymous && type.symbol && type.symbol.flags & (SymbolFlags.Function | SymbolFlags.Method | SymbolFlags.TypeLiteral | SymbolFlags.Class) ||
objectFlags & ObjectFlags.Mapped ||
@ -10554,6 +10554,13 @@ namespace ts {
inferFromTypes(sourceTypes[i], targetTypes[i]);
}
}
else if (source.flags & TypeFlags.Index && target.flags & TypeFlags.Index) {
inferFromTypes((<IndexType>source).type, (<IndexType>target).type);
}
else if (source.flags & TypeFlags.IndexedAccess && target.flags & TypeFlags.IndexedAccess) {
inferFromTypes((<IndexedAccessType>source).objectType, (<IndexedAccessType>target).objectType);
inferFromTypes((<IndexedAccessType>source).indexType, (<IndexedAccessType>target).indexType);
}
else if (target.flags & TypeFlags.UnionOrIntersection) {
const targetTypes = (<UnionOrIntersectionType>target).types;
let typeVariableCount = 0;
@ -10627,6 +10634,12 @@ namespace ts {
}
function inferFromObjectTypes(source: Type, target: Type) {
if (isGenericMappedType(source) && isGenericMappedType(target)) {
// The source and target types are generic types { [P in S]: X } and { [P in T]: Y }, so we infer
// from S to T and from X to Y.
inferFromTypes(getConstraintTypeFromMappedType(<MappedType>source), getConstraintTypeFromMappedType(<MappedType>target));
inferFromTypes(getTemplateTypeFromMappedType(<MappedType>source), getTemplateTypeFromMappedType(<MappedType>target));
}
if (getObjectFlags(target) & ObjectFlags.Mapped) {
const constraintType = getConstraintTypeFromMappedType(<MappedType>target);
if (constraintType.flags & TypeFlags.Index) {