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[CSBindings] Open collection before binding parameter only if original argument type failed

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Instead of always opening argument type represented by a collection
without type variables (to support subtyping when element is a labeled tuple),
let's try original type first and if that fails use a slower path with
indirection which attempts `array upcast`. Doing it this way helps to
propagate contextual information faster which fixes a performance regression.

Resolves: rdar://problem/54580247
This commit is contained in:
Pavel Yaskevich
2020-02-27 15:04:43 -08:00
parent 0fb4ea1ec3
commit 20fc51d4f4
4 changed files with 25 additions and 21 deletions
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33
lib/Sema/CSBindings.cpp
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@@ -1043,6 +1043,25 @@ bool TypeVarBindingProducer::computeNext() {
if (auto simplifiedSuper = CS.checkTypeOfBinding(TypeVar, supertype))
addNewBinding(binding.withType(*simplifiedSuper));
}
auto srcLocator = binding.getLocator();
if (srcLocator &&
srcLocator->isLastElement<LocatorPathElt::ApplyArgToParam>() &&
!type->hasTypeVariable() && CS.isCollectionType(type)) {
// If the type binding comes from the argument conversion, let's
// instead of binding collection types directly, try to bind
// using temporary type variables substituted for element
// types, that's going to ensure that subtype relationship is
// always preserved.
auto *BGT = type->castTo<BoundGenericType>();
auto UGT = UnboundGenericType::get(BGT->getDecl(), BGT->getParent(),
BGT->getASTContext());
auto dstLocator = TypeVar->getImpl().getLocator();
auto newType = CS.openUnboundGenericType(UGT, dstLocator)
->reconstituteSugar(/*recursive=*/false);
addNewBinding(binding.withType(newType));
}
}
if (newBindings.empty())
@@ -1062,20 +1081,6 @@ bool TypeVariableBinding::attempt(ConstraintSystem &cs) const {
if (Binding.hasDefaultedLiteralProtocol()) {
type = cs.openUnboundGenericType(type, dstLocator);
type = type->reconstituteSugar(/*recursive=*/false);
} else if (srcLocator &&
srcLocator->isLastElement<LocatorPathElt::ApplyArgToParam>() &&
!type->hasTypeVariable() && cs.isCollectionType(type)) {
// If the type binding comes from the argument conversion, let's
// instead of binding collection types directly, try to bind
// using temporary type variables substituted for element
// types, that's going to ensure that subtype relationship is
// always preserved.
auto *BGT = type->castTo<BoundGenericType>();
auto UGT = UnboundGenericType::get(BGT->getDecl(), BGT->getParent(),
BGT->getASTContext());
type = cs.openUnboundGenericType(UGT, dstLocator);
type = type->reconstituteSugar(/*recursive=*/false);
}
cs.addConstraint(ConstraintKind::Bind, TypeVar, type, srcLocator);