[Sema] lay groundwork for noncopyable existentials

Author: kavon

include/swift/AST/ExistentialLayout.h

@@ -31,6 +31,7 @@ struct ExistentialLayout {
 
   ExistentialLayout() {
     hasExplicitAnyObject = false;
+    hasInverseCopyable = false;
     containsNonObjCProtocol = false;
     containsParameterized = false;
   }
@@ -46,6 +47,9 @@ struct ExistentialLayout {
   /// Whether the existential contains an explicit '& AnyObject' constraint.
   bool hasExplicitAnyObject : 1;
 
+  /// Whether the existential contains an explicit '& ~Copyable' constraint.
+  bool hasInverseCopyable : 1;
+
   /// Whether any protocol members are non-@objc.
   bool containsNonObjCProtocol : 1;
 

lib/AST/Type.cpp

@@ -341,25 +341,40 @@ ExistentialLayout::ExistentialLayout(CanProtocolType type) {
   auto *protoDecl = type->getDecl();
 
   hasExplicitAnyObject = false;
+  hasInverseCopyable = false;
   containsNonObjCProtocol = !protoDecl->isObjC();
   containsParameterized = false;
 
   protocols.push_back(protoDecl);
 }
 
 ExistentialLayout::ExistentialLayout(CanInverseType type) {
-  //  TODO: implement this correctly!!!!!!!!!
   hasExplicitAnyObject = false;
+  hasInverseCopyable = false;
   containsNonObjCProtocol = false;
   containsParameterized = false;
-  llvm_unreachable("FIXME");
+
+  // Handle inverse.
+  switch (type->getInverseKind()) {
+  case InvertibleProtocolKind::Copyable:
+    hasInverseCopyable = true;
+  }
 }
 
 ExistentialLayout::ExistentialLayout(CanProtocolCompositionType type) {
   hasExplicitAnyObject = type->hasExplicitAnyObject();
+  hasInverseCopyable = false;
   containsNonObjCProtocol = false;
   containsParameterized = false;
 
+  // Handle inverses.
+  for (auto ip : type->getInverses()) {
+    switch (ip) {
+    case InvertibleProtocolKind::Copyable:
+      hasInverseCopyable = true;
+    }
+  }
+
   auto members = type.getMembers();
   if (!members.empty() &&
       (members[0].getClassOrBoundGenericClass() ||

lib/Sema/TypeCheckDecl.cpp

@@ -961,13 +961,6 @@ bool HasNoncopyableAnnotationRequest::evaluate(Evaluator &evaluator, TypeDecl *d
     if (defaults.contains(kind)) {
       defaults.remove(kind);
       lastInverse.insert({kind, loc});
-
-      // Classes are always copyable.
-      if (isa<ClassDecl>(decl) && kind == InvertibleProtocolKind::Copyable) {
-        ctx.Diags.diagnose(loc, diag::noncopyable_class);
-        return;
-      }
-
       return;
     }
 

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -227,6 +227,12 @@ static void checkInheritanceClause(
         continue;
       }
 
+      // Classes are always copyable.
+      if (layout.hasInverseCopyable && isa<ClassDecl>(decl)) {
+        decl->diagnose(diag::noncopyable_class);
+        continue;
+      }
+
       // If the existential did not have a class constraint, we're done.
       if (!layout.explicitSuperclass)
         continue;