Fix regression from r190382.

Make sure we perform the correct "referenced-but-not-used" check for
static member constants.

Fixes bug reported on cfe-commits by Alexey Samsonov.

llvm-svn: 190437

clang/lib/Sema/Sema.cpp

@@ -358,6 +358,15 @@ static bool ShouldRemoveFromUnused(Sema *SemaRef, const DeclaratorDecl *D) {
   }
 
   if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
+    // If a variable usable in constant expressions is referenced,
+    // don't warn if it isn't used: if the value of a variable is required
+    // for the computation of a constant expression, it doesn't make sense to
+    // warn even if the variable isn't odr-used.  (isReferenced doesn't
+    // precisely reflect that, but it's a decent approximation.)
+    if (VD->isReferenced() &&
+        VD->isUsableInConstantExpressions(SemaRef->Context))
+      return true;
+
     // UnusedFileScopedDecls stores the first declaration.
     // The declaration may have become definition so check again.
     const VarDecl *DeclToCheck = VD->getDefinition();

clang/lib/Sema/SemaDecl.cpp

@@ -1220,14 +1220,6 @@ bool Sema::ShouldWarnIfUnusedFileScopedDecl(const DeclaratorDecl *D) const {
     if (!isMainFileLoc(*this, VD->getLocation()))
       return false;
 
-    // If a variable usable in constant expressions is referenced,
-    // don't warn if it isn't used: if the value of a variable is required
-    // for the computation of a constant expression, it doesn't make sense to
-    // warn even if the variable isn't odr-used.  (isReferenced doesn't
-    // precisely reflect that, but it's a decent approximation.)
-    if (VD->isReferenced() && VD->isUsableInConstantExpressions(Context))
-      return false;
-
     if (Context.DeclMustBeEmitted(VD))
       return false;
 

clang/test/SemaCXX/warn-unused-filescoped.cpp

@@ -178,4 +178,13 @@ namespace pr14776 {
   auto b = X(); // expected-warning {{unused variable 'b'}}
 }
 
+namespace UndefinedInternalStaticMember {
+  namespace {
+    struct X {
+      static const unsigned x = 3;
+      int y[x];
+    };
+  }
+}
+
 #endif