Sema: Reject enums marked with both @cdecl and @objc

Author: xymus

include/swift/AST/DiagnosticsSema.def

@@ -2056,6 +2056,9 @@ ERROR(cdecl_empty_name,none,
       "%0 symbol name cannot be empty", (DeclAttribute))
 ERROR(cdecl_throws,none,
       "raising errors from %0 functions is not supported", (DeclAttribute))
+ERROR(cdecl_incompatible_with_objc,none,
+      "cannot apply both '@cdecl' and '@objc' to %kindonly0",
+      (const Decl *))
 ERROR(cdecl_feature_required,none,
       "@cdecl requires '-enable-experimental-feature CDecl'",
       ())

lib/Sema/TypeCheckAttr.cpp

@@ -2384,9 +2384,15 @@ void AttributeChecker::visitCDeclAttr(CDeclAttr *attr) {
              attr, "func");
   }
 
+  // Reject using both @cdecl and @objc on the same decl.
+  if (D->getAttrs().getAttribute<ObjCAttr>()) {
+    diagnose(attr->getLocation(), diag::cdecl_incompatible_with_objc, D);
+  }
+
+  // @cdecl needs to be enabled via a feature flag.
   if (!attr->Underscored &&
       !Ctx.LangOpts.hasFeature(Feature::CDecl)) {
-    Ctx.Diags.diagnose(attr->getLocation(), diag::cdecl_feature_required);
+    diagnose(attr->getLocation(), diag::cdecl_feature_required);
   }
 }
 

test/attr/attr_cdecl_official.swift

@@ -59,6 +59,14 @@ func swiftEnum(x: SwiftEnum) {} // expected-error{{cannot be represented}} expec
 @cdecl("cEnum")
 func cEnum(x: CEnum) {}
 
+@cdecl("CDeclAndObjC") // expected-error {{cannot apply both '@cdecl' and '@objc' to enum}}
+@objc
+enum CDeclAndObjC: Int { case A, B }
+
+@cdecl("TwoCDecls") // expected-note {{attribute already specified here}}
+@_cdecl("TwoCDecls") // expected-error {{duplicate attribute}}
+func TwoCDecls() {}
+
 class Foo {
   @cdecl("Foo_foo") // expected-error{{@cdecl can only be applied to global functions}}
   func foo(x: Int) -> Int { return x }