Sema: reword inverse-on-extension message

We should be saying "can't suppress Copyable" instead, since you can't
"suppress" ~Copyable.

Author: kavon

include/swift/AST/DiagnosticsSema.def

@@ -7728,8 +7728,8 @@ ERROR(inverse_conflicts_explicit_composition, none,
       "composition cannot contain '~%0' when another member requires '%0'",
       (StringRef))
 ERROR(inverse_extension, none,
-      "cannot suppress %0 in extension",
-      (Type))
+      "cannot suppress '%0' in extension",
+      (StringRef))
 ERROR(copyable_illegal_deinit, none,
       "deinitializer cannot be declared in %kind0 that conforms to 'Copyable'",
       (const ValueDecl *))

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -295,10 +295,15 @@ static void checkInheritanceClause(
       auto layout = inheritedTy->getExistentialLayout();
 
       // An inverse on an extension is an error.
-      if (isa<ExtensionDecl>(decl))
-        if (auto pct = inheritedTy->getAs<ProtocolCompositionType>())
-          if (!pct->getInverses().empty())
-            decl->diagnose(diag::inverse_extension, inheritedTy);
+      if (isa<ExtensionDecl>(decl)) {
+        auto canInheritedTy = inheritedTy->getCanonicalType();
+        if (auto pct = canInheritedTy->getAs<ProtocolCompositionType>()) {
+          for (auto inverse : pct->getInverses()) {
+            decl->diagnose(diag::inverse_extension,
+                           getProtocolName(getKnownProtocolKind(inverse)));
+          }
+        }
+      }
 
       // Subclass existentials are not allowed except on classes and
       // non-@objc protocols.

test/Generics/inverse_generics.swift

@@ -188,11 +188,11 @@ class NiceTry: ~Copyable, Copyable {} // expected-error {{classes cannot be '~Co
 
 
 struct Extendo: ~Copyable {}
-extension Extendo: Copyable, ~Copyable {} // expected-error {{cannot suppress '~Copyable' in extension}}
+extension Extendo: Copyable, ~Copyable {} // expected-error {{cannot suppress 'Copyable' in extension}}
 // expected-error@-1 {{struct 'Extendo' required to be 'Copyable' but is marked with '~Copyable'}}
 
 enum EnumExtendo {}
-extension EnumExtendo: ~Copyable {} // expected-error {{cannot suppress '~Copyable' in extension}}
+extension EnumExtendo: ~Copyable {} // expected-error {{cannot suppress 'Copyable' in extension}}
 
 extension NeedsCopyable where Self: ~Copyable {}
 // expected-error@-1 {{'Self' required to be 'Copyable' but is marked with '~Copyable'}}

test/Parse/inverses.swift

@@ -52,7 +52,7 @@ protocol Rope<Element>: Hashable, ~Copyable {  // expected-error {{'Self' requir
   associatedtype Element: ~Copyable
 }
 
-extension S: ~Copyable {} // expected-error {{cannot suppress '~Copyable' in extension}}
+extension S: ~Copyable {} // expected-error {{cannot suppress 'Copyable' in extension}}
 
 struct S: ~U, // expected-error {{type 'U' cannot be suppressed}}
           ~Copyable {}
@@ -123,3 +123,9 @@ func typeInExpression() {
 
 func param3(_ t: borrowing any ~Copyable) {}
 func param4(_ t: any ~Copyable.Type) {}
+
+protocol P: ~Copyable {}
+protocol Q: ~Copyable {}
+protocol R: ~Copyable {}
+struct Blooper<T: ~Copyable>: ~Copyable {}
+extension Blooper: (Q & (R & (~Copyable & P))) {} // expected-error {{cannot suppress 'Copyable' in extension}}