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[ConstraintSystem] Temporary revert 84a3db45db96 as a workaround for rdar://problem/62842651 #31569

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Merged
merged 2 commits into from
May 6, 2020
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[ConstraintSystem] Temporary revert 84a3db45db96 as a workaround for rdar://problem/62842651 #31569

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191fcc4
Revert "[CS] Account for type variables when matching metatypes"
xedin May 5, 2020
29ae605
[TypeChecker] NFC: Add a test-case for rdar://problem/62842651
xedin May 5, 2020
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36 changes: 12 additions & 24 deletions lib/Sema/CSSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4392,34 +4392,22 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
auto meta1 = cast<AnyMetatypeType>(desugar1);
auto meta2 = cast<AnyMetatypeType>(desugar2);

auto instanceType1 = meta1->getInstanceType();
auto instanceType2 = meta2->getInstanceType();

// A.Type < B.Type if A < B and both A and B are classes.
// P.Type < Q.Type if P < Q, both P and Q are protocols, and P.Type
// and Q.Type are both existential metatypes.
auto getSubKind = [&]() -> ConstraintKind {
auto subKind = std::min(kind, ConstraintKind::Subtype);

// If we have existential metatypes, we need to perform subtyping.
if (!isa<MetatypeType>(meta1))
return subKind;

// If the LHS cannot be a type with a superclass, we can perform a bind.
if (!instanceType1->isTypeVariableOrMember() &&
!instanceType1->mayHaveSuperclass())
return ConstraintKind::Bind;

// If the RHS cannot be a class type, we can perform a bind.
if (!instanceType2->isTypeVariableOrMember() &&
!instanceType2->getClassOrBoundGenericClass())
return ConstraintKind::Bind;

return subKind;
};
// and Q.Type are both existential metatypes
auto subKind = std::min(kind, ConstraintKind::Subtype);
// If instance types can't have a subtype relationship
// it means that such types can be simply equated.
auto instanceType1 = meta1->getInstanceType();
auto instanceType2 = meta2->getInstanceType();
if (isa<MetatypeType>(meta1) &&
!(instanceType1->mayHaveSuperclass() &&
instanceType2->getClassOrBoundGenericClass())) {
subKind = ConstraintKind::Bind;
}

auto result =
matchTypes(instanceType1, instanceType2, getSubKind(), subflags,
matchTypes(instanceType1, instanceType2, subKind, subflags,
locator.withPathElement(ConstraintLocator::InstanceType));

// If matching of the instance types resulted in the failure make sure
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12 changes: 12 additions & 0 deletions test/Constraints/rdar62842651.swift
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@@ -0,0 +1,12 @@
// RUN: %target-swift-frontend -emit-sil -verify %s | %FileCheck %s
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Shouldn't this test be in test/SILGen then? (And it can use -emit-silgen instead of -emit-sil, which also runs mandatory passes)

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This is a problem where type-checker infers types incorrectly I just could think of an easier and more robust way to verify it in test-case then check emitted SIL.

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@xedin xedin May 5, 2020 •
edited
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I didn't want to match against constraint system output because that would just become a constant pain to maintain if anything changes with locators and/or type variables.


class A {}
class B: A {}

func test<T>(_ type: T.Type) -> T? {
fatalError()
}

// CHECK: [[RESULT:%.*]] = function_ref @$s12rdar628426514testyxSgxmlF
// CHECK-NEXT: apply [[RESULT]]<B>({{.*}})
let _: A? = test(B.self)