[GSB] Diagnose all same-type-to-concrete conflicts consistently.

include/swift/AST/DiagnosticsSema.def

@@ -1690,6 +1690,9 @@ NOTE(redundant_conformance_here,none,
      "inferred from type here}0",
      (unsigned, Type, ProtocolDecl *))
 
+ERROR(same_type_conflict,none,
+      "%select{generic parameter |protocol |}0%1 cannot be equal to both "
+      "%2 and %3", (unsigned, Type, Type, Type))
 WARNING(redundant_same_type_to_concrete,none,
         "redundant same-type constraint %0 == %1", (Type, Type))
 NOTE(same_type_redundancy_here,none,

lib/AST/GenericSignatureBuilder.cpp

@@ -1728,6 +1728,7 @@ namespace {
     PotentialArchetype *pa;
 
     void operator()(Type type1, Type type2) const {
+      // FIXME: Shouldn't need this!
       if (pa->getParent() && pa->getConcreteTypeDecl() &&
           source->getLoc().isInvalid()) {
         diags.diagnose(pa->getConcreteTypeDecl()->getLoc(),
@@ -1736,14 +1737,6 @@ namespace {
                        type1, type2);
         return;
       }
-
-      if (source->getLoc().isValid()) {
-        diags.diagnose(source->getLoc(),
-                       diag::requires_same_type_conflict,
-                       pa->isGenericParam(),
-                       pa->getDependentType(/*FIXME: */{ }, true),
-                       type1, type2);
-      }
     }
   };
 } // end anonymous namespace
@@ -5010,8 +5003,8 @@ void GenericSignatureBuilder::checkConcreteTypeConstraints(
 
   checkConstraintList<Type>(
     genericParams, equivClass->concreteTypeConstraints,
-    [](const ConcreteConstraint &constraint) {
-      return true;
+    [&](const ConcreteConstraint &constraint) {
+      return constraint.value->isEqual(equivClass->concreteType);
     },
     [&](Type concreteType) {
       // If the concrete type is equivalent, the constraint is redundant.
@@ -5020,10 +5013,14 @@ void GenericSignatureBuilder::checkConcreteTypeConstraints(
       if (concreteType->isEqual(equivClass->concreteType))
         return ConstraintRelation::Redundant;
 
-      // Call this unrelated.
-      return ConstraintRelation::Unrelated;
+      // If either has a type parameter, call them unrelated.
+      if (concreteType->hasTypeParameter() ||
+          equivClass->concreteType->hasTypeParameter())
+        return ConstraintRelation::Unrelated;
+
+      return ConstraintRelation::Conflicting;
     },
-    None,
+    diag::same_type_conflict,
     diag::redundant_same_type_to_concrete,
     diag::same_type_redundancy_here);
 

test/Constraints/same_types.swift

@@ -58,14 +58,16 @@ func test3<T: Fooable, U: Fooable>(_ t: T, u: U) -> (X, X)
 func fail1<
   T: Fooable, U: Fooable
 >(_ t: T, u: U) -> (X, Y)
-  where T.Foo == X, U.Foo == Y, T.Foo == U.Foo { // expected-error{{associated type 'T.Foo' cannot be equal to both 'X' and 'Y'}}
+  where T.Foo == X, U.Foo == Y, T.Foo == U.Foo { // expected-error{{'U.Foo' cannot be equal to both 'Y' and 'X'}}
+  // expected-note@-1{{same-type constraint 'T.Foo' == 'X' written here}}
   return (t.foo, u.foo) // expected-error{{cannot convert return expression of type 'X' to return type 'Y'}}
 }
 
 func fail2<
   T: Fooable, U: Fooable
 >(_ t: T, u: U) -> (X, Y)
-  where T.Foo == U.Foo, T.Foo == X, U.Foo == Y { // expected-error{{associated type 'U.Foo' cannot be equal to both 'X' and 'Y'}}
+  where T.Foo == U.Foo, T.Foo == X, U.Foo == Y { // expected-error{{'U.Foo' cannot be equal to both 'Y' and 'X'}}
+  // expected-note@-1{{same-type constraint 'T.Foo' == 'X' written here}}
   return (t.foo, u.foo) // expected-error{{cannot convert return expression of type 'X' to return type 'Y'}}
 }
 
@@ -94,20 +96,22 @@ func test7<T: Barrable>(_ t: T) -> (Y, X) where T.Bar == Y, T.Bar.Foo == X {
 
 func fail4<T: Barrable>(_ t: T) -> (Y, Z)
   where
-  T.Bar == Y,
-  T.Bar.Foo == Z { // expected-error{{associated type 'T.Bar.Foo' cannot be equal to both 'Y.Foo' (aka 'X') and 'Z'}}
+  T.Bar == Y, // expected-note{{same-type constraint 'T.Bar.Foo' == 'Y.Foo' (aka 'X') implied here}}
+  T.Bar.Foo == Z { // expected-error{{'T.Bar.Foo' cannot be equal to both 'Z' and 'Y.Foo' (aka 'X')}}
   return (t.bar, t.bar.foo) // expected-error{{cannot convert return expression of type 'X' to return type 'Z'}}
 }
 
 func fail5<T: Barrable>(_ t: T) -> (Y, Z)
   where
-  T.Bar.Foo == Z, // expected-warning{{redundant same-type constraint 'T.Bar.Foo' == 'Z'}}
-  T.Bar == Y { // expected-error{{associated type 'T.Bar.Foo' cannot be equal to both 'Z' and 'X'}}
-	// expected-note@-1{{same-type constraint 'T.Bar.Foo' == 'Y.Foo' (aka 'X') implied here}}
+  T.Bar.Foo == Z, // expected-note{{same-type constraint 'T.Bar.Foo' == 'Z' written here}}
+  T.Bar == Y { // expected-error{{'T.Bar.Foo' cannot be equal to both 'Y.Foo' (aka 'X') and 'Z'}}
   return (t.bar, t.bar.foo) // expected-error{{cannot convert return expression of type 'X' to return type 'Z'}}
 }
 
-func test8<T: Fooable>(_ t: T) where T.Foo == X, T.Foo == Y {} // expected-error{{associated type 'T.Foo' cannot be equal to both 'X' and 'Y'}}
+func test8<T: Fooable>(_ t: T)
+  where T.Foo == X, // expected-note{{same-type constraint 'T.Foo' == 'X' written here}}
+  T.Foo == Y {} // expected-error{{'T.Foo' cannot be equal to both 'Y' and 'X'}}
+
 
 func testAssocTypeEquivalence<T: Fooable>(_ fooable: T) -> X.Type
   where T.Foo == X {
@@ -246,7 +250,6 @@ func structuralSameTypeRecursive1<T: P2, U>(_: T, _: U)
   where T.Assoc1 == Tuple2<T.Assoc1, U> // expected-error{{same-type constraint 'T.Assoc1' == '(T.Assoc1, U)' is recursive}}
 { }
 
-
 protocol P3 {
 }
 
@@ -256,5 +259,25 @@ protocol P4 {
 
 func test9<T>(_: T) where T.A == X, T: P4, T.A: P3 { } // expected-error{{same-type constraint type 'X' does not conform to required protocol 'P3'}}
 
+// Same-type constraint conflict through protocol where clauses.
+protocol P5 where Foo1 == Foo2 {
+  associatedtype Foo1
+  associatedtype Foo2
+}
+
+protocol P6 {
+  associatedtype Bar: P5
+}
+
+struct X5a {}
+
+struct X5b { }
+
+func test9<T: P6, U: P6>(_ t: T, u: U)
+  where T.Bar.Foo1 == X5a, // expected-note{{same-type constraint 'T.Bar.Foo1' == 'X5a' written here}}
+        U.Bar.Foo2 == X5b, // expected-error{{'U.Bar.Foo2' cannot be equal to both 'X5b' and 'X5a'}}
+        T.Bar == U.Bar {
+}
+
 // FIXME: Remove -verify-ignore-unknown.
 // <unknown>:0: error: unexpected error produced: generic parameter τ_0_0.Bar.Foo cannot be equal to both 'Y.Foo' (aka 'X') and 'Z'