Merge pull request #16921 from DougGregor/gsb-canononicalze-concrete-superclass-4.2

Author: swift-ci

lib/AST/GenericSignatureBuilder.cpp

@@ -6981,17 +6981,24 @@ void GenericSignatureBuilder::checkSameTypeConstraints(
 void GenericSignatureBuilder::checkConcreteTypeConstraints(
                               TypeArrayView<GenericTypeParamType> genericParams,
                               EquivalenceClass *equivClass) {
+  // Resolve any thus-far-unresolved dependent types.
+  Type resolvedConcreteType =
+    resolveDependentMemberTypes(*this, equivClass->concreteType);
+
   checkConstraintList<Type>(
     genericParams, equivClass->concreteTypeConstraints,
     [&](const ConcreteConstraint &constraint) {
-      return constraint.value->isEqual(equivClass->concreteType);
+      if (constraint.value->isEqual(resolvedConcreteType))
+        return true;
+
+      auto resolvedType =
+        resolveDependentMemberTypes(*this, constraint.value);
+      return resolvedType->isEqual(resolvedConcreteType);
     },
     [&](const Constraint<Type> &constraint) {
       Type concreteType = constraint.value;
 
       // If the concrete type is equivalent, the constraint is redundant.
-      // FIXME: Should check this constraint after substituting in the
-      // archetype anchors for each dependent type.
       if (concreteType->isEqual(equivClass->concreteType))
         return ConstraintRelation::Redundant;
 
@@ -7006,33 +7013,28 @@ void GenericSignatureBuilder::checkConcreteTypeConstraints(
     diag::redundant_same_type_to_concrete,
     diag::same_type_redundancy_here);
 
-  // Resolve any thus-far-unresolved dependent types.
-  equivClass->concreteType =
-    resolveDependentMemberTypes(*this, equivClass->concreteType);
+  equivClass->concreteType = resolvedConcreteType;
 }
 
 void GenericSignatureBuilder::checkSuperclassConstraints(
                               TypeArrayView<GenericTypeParamType> genericParams,
                               EquivalenceClass *equivClass) {
   assert(equivClass->superclass && "No superclass constraint?");
 
-  // FIXME: We should be substituting in the canonical type in context so
-  // we can resolve superclass requirements, e.g., if you had:
-  //
-  //   class Foo<T>
-  //   class Bar: Foo<Int>
-  //
-  //   func foo<T, U where U: Bar, U: Foo<T>>(...) { ... }
-  //
-  // then the second `U: Foo<T>` constraint introduces a `T == Int`
-  // constraint, and we will need to perform that substitution for this final
-  // check.
+  // Resolve any this-far-unresolved dependent types.
+  Type resolvedSuperclass =
+    resolveDependentMemberTypes(*this, equivClass->superclass);
 
   auto representativeConstraint =
     checkConstraintList<Type>(
       genericParams, equivClass->superclassConstraints,
       [&](const ConcreteConstraint &constraint) {
-        return constraint.value->isEqual(equivClass->superclass);
+        if (constraint.value->isEqual(resolvedSuperclass))
+          return true;
+
+        Type resolvedType =
+          resolveDependentMemberTypes(*this, constraint.value);
+        return resolvedType->isEqual(equivClass->superclass);
       },
       [&](const Constraint<Type> &constraint) {
         Type superclass = constraint.value;
@@ -7049,15 +7051,16 @@ void GenericSignatureBuilder::checkSuperclassConstraints(
       diag::superclass_redundancy_here);
 
   // Resolve any this-far-unresolved dependent types.
-  equivClass->superclass =
-    resolveDependentMemberTypes(*this, equivClass->superclass);
+  equivClass->superclass = resolvedSuperclass;
 
   // If we have a concrete type, check it.
   // FIXME: Substitute into the concrete type.
   if (equivClass->concreteType) {
+    Type resolvedConcreteType =
+      resolveDependentMemberTypes(*this, equivClass->concreteType);
     auto existing = equivClass->findAnyConcreteConstraintAsWritten();
     // Make sure the concrete type fulfills the superclass requirement.
-    if (!equivClass->superclass->isExactSuperclassOf(equivClass->concreteType)){
+    if (!equivClass->superclass->isExactSuperclassOf(resolvedConcreteType)){
       Impl->HadAnyError = true;
       if (existing) {
         Diags.diagnose(existing->source->getLoc(), diag::type_does_not_inherit,
@@ -7077,7 +7080,7 @@ void GenericSignatureBuilder::checkSuperclassConstraints(
                        diag::type_does_not_inherit,
                        representativeConstraint.getSubjectDependentType(
                                                               genericParams),
-                       equivClass->concreteType, equivClass->superclass);
+                       resolvedConcreteType, equivClass->superclass);
       }
     } else if (representativeConstraint.source->shouldDiagnoseRedundancy(true)
                && existing &&

test/Generics/same_type_constraints.swift

@@ -378,3 +378,19 @@ typealias NotAnInt = Double
 extension X11 where NotAnInt == Int { }
 // expected-warning@-1{{neither type in same-type constraint ('NotAnInt' (aka 'Double') or 'Int') refers to a generic parameter or associated type}}
 // expected-error@-2{{generic signature requires types 'NotAnInt' (aka 'Double') and 'Int' to be the same}}
+
+
+struct X12<T> { }
+
+protocol P12 {
+  associatedtype A
+  associatedtype B
+}
+
+func testP12a<T: P12>(_: T) where T.A == X12<Int>, T.A == X12<T.B>, T.B == Int { }
+// expected-warning@-1{{redundant same-type constraint 'T.B' == 'Int'}}
+// expected-note@-2{{same-type constraint 'T.B' == 'Int' written here}}
+
+func testP12b<T: P12>(_: T) where T.B == Int, T.A == X12<T.B>, X12<T.B> == T.A { }
+// expected-warning@-1{{redundant same-type constraint 'T.A' == 'X12<Int>'}}
+// expected-note@-2{{same-type constraint 'T.A' == 'X12<Int>' written here}}