ManualOwnership: disallow @_noImplicitCopy

ManualOwnership effectively subsumes @_noImplicitCopy,
by diagnosing all implicit copies in a function.

Author: kavon

include/swift/AST/DiagnosticsSema.def

@@ -2148,6 +2148,8 @@ ERROR(attr_static_exclusive_no_setters,none,
 // @_manualOwnership
 ERROR(attr_manual_ownership_experimental,none,
       "'@_manualOwnership' requires '-enable-experimental-feature ManualOwnership'", ())
+ERROR(attr_manual_ownership_noimplicitcopy,none,
+      "'@_noImplicitCopy' cannot be used with ManualOwnership", ())
 
 // @extractConstantsFromMembers
 ERROR(attr_extractConstantsFromMembers_experimental,none,

lib/Sema/TypeCheckAttr.cpp

@@ -491,6 +491,11 @@ void AttributeChecker::visitNoImplicitCopyAttr(NoImplicitCopyAttr *attr) {
     return;
   }
 
+  // Don't allow it to be combined with ManualOwnership.
+  if (D->getASTContext().LangOpts.hasFeature(Feature::ManualOwnership)) {
+    diagnoseAndRemoveAttr(attr, diag::attr_manual_ownership_noimplicitcopy);
+  }
+
   if (auto *funcDecl = dyn_cast<FuncDecl>(D)) {
     if (visitOwnershipAttr(attr))
       return;

test/Sema/manualownership_attr.swift

@@ -0,0 +1,14 @@
+// RUN: %target-typecheck-verify-swift \
+// RUN:    -enable-experimental-feature NoImplicitCopy \
+// RUN:    -enable-experimental-feature ManualOwnership
+
+// REQUIRES: swift_feature_ManualOwnership
+// REQUIRES: swift_feature_NoImplicitCopy
+
+class C {}
+
+@_manualOwnership
+func hello() -> (C, C) {
+  @_noImplicitCopy let x = C() // expected-error {{'@_noImplicitCopy' cannot be used with ManualOwnership}}
+  return (x, x)
+}