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Avoid this-instantiation if not necessary for relationship (#28263)

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This commit is contained in:
Wesley Wigham
2018-10-31 13:21:35 -07:00
committed by GitHub
parent 8e4b90da00
commit 0ef844ff2b
1 changed files with 7 additions and 4 deletions
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11
src/compiler/checker.ts
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@@ -12065,12 +12065,15 @@ namespace ts {
return result;
}
}
else {
const instantiated = getTypeWithThisArgument(constraint, source);
if (result = isRelatedTo(instantiated, target, reportErrors, /*headMessage*/ undefined, isIntersectionConstituent)) {
// hi-speed no-this-instantiation check (less accurate, but avoids costly `this`-instantiation when the constraint will suffice), see #28231 for report on why this is needed
else if (result = isRelatedTo(constraint, target, /*reportErrors*/ false, /*headMessage*/ undefined, isIntersectionConstituent)) {
errorInfo = saveErrorInfo;
return result;
}
}
// slower, fuller, this-instantiated check (necessary when comparing raw `this` types from base classes), see `subclassWithPolymorphicThisIsAssignable.ts` test for example
else if (result = isRelatedTo(getTypeWithThisArgument(constraint, source), target, reportErrors, /*headMessage*/ undefined, isIntersectionConstituent)) {
errorInfo = saveErrorInfo;
return result;
}
}
else if (source.flags & TypeFlags.Index) {