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Only infer from members of object types if the types are possibly related

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This commit is contained in:
Anders Hejlsberg 2017-08-03 08:07:07 -07:00
parent c06a30ae68
commit 13750d2d65
1 changed files with 21 additions and 4 deletions
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25
src/compiler/checker.ts
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@ -10325,6 +10325,19 @@ namespace ts {
}
}
function isPossiblyAssignableTo(source: Type, target: Type) {
const properties = getPropertiesOfObjectType(target);
for (const targetProp of properties) {
if (!(targetProp.flags & (SymbolFlags.Optional | SymbolFlags.Prototype))) {
const sourceProp = getPropertyOfObjectType(source, targetProp.escapedName);
if (!sourceProp) {
return false;
}
}
}
return true;
}
function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority: InferencePriority = 0) {
let symbolStack: Symbol[];
let visited: Map<boolean>;
@ -10518,10 +10531,14 @@ namespace ts {
return;
}
}
inferFromProperties(source, target);
inferFromSignatures(source, target, SignatureKind.Call);
inferFromSignatures(source, target, SignatureKind.Construct);
inferFromIndexTypes(source, target);
// Infer from the members of source and target only if the two types are possibly related. We check
// in both directions because we may be inferring for a co-variant or a contra-variant position.
if (isPossiblyAssignableTo(source, target) || isPossiblyAssignableTo(target, source)) {
inferFromProperties(source, target);
inferFromSignatures(source, target, SignatureKind.Call);
inferFromSignatures(source, target, SignatureKind.Construct);
inferFromIndexTypes(source, target);
}
}
function inferFromProperties(source: Type, target: Type) {