[Sema] Avoid "case value not in enumerated type" warning for C++11 opaque enums

This commit ensures that the switch warning "case value not in enumerated type"
isn't shown for opaque enums. We don't know the actual list of values in opaque
enums, so that warning is incorrect.

rdar://29230764

Differential Revision: https://reviews.llvm.org/D27299

llvm-svn: 289055

2 files changed, 32 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 89c82c9805a..50f0a22ff02 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -1070,7 +1070,8 @@ Sema::ActOnFinishSwitchStmt(SourceLocation SwitchLoc, Stmt *Switch,
     const EnumType *ET = CondTypeBeforePromotion->getAs<EnumType>();
 
     // If switch has default case, then ignore it.
-    if (!CaseListIsErroneous  && !HasConstantCond && ET) {
+    if (!CaseListIsErroneous && !HasConstantCond && ET &&
+        ET->getDecl()->isCompleteDefinition()) {
       const EnumDecl *ED = ET->getDecl();
       EnumValsTy EnumVals;
 
diff --git a/clang/test/SemaCXX/switch.cpp b/clang/test/SemaCXX/switch.cpp
index 392dcd86980..0c60ce02097 100644
--- a/clang/test/SemaCXX/switch.cpp
+++ b/clang/test/SemaCXX/switch.cpp
@@ -100,3 +100,33 @@ namespace Conversion {
   }
   template void f(S); // expected-note {{instantiation of}}
 }
+
+// rdar://29230764
+namespace OpaqueEnumWarnings {
+
+enum Opaque : int;
+enum class OpaqueClass : int;
+
+enum class Defined : int;
+enum class Defined : int { a };
+
+void test(Opaque o, OpaqueClass oc, Defined d) {
+  // Don't warn that case value is not present in opaque enums.
+  switch (o) {
+  case (Opaque)1:
+    break;
+  }
+  switch (oc) {
+  case (OpaqueClass)1:
+    break;
+  }
+
+  switch (d) {
+  case Defined::a:
+    break;
+  case (Defined)2: // expected-warning {{case value not in enumerated type 'OpaqueEnumWarnings::Defined'}}
+    break;
+  }
+}
+
+}