Add -Wswitch-enum-redundant-default.

This warning acts as the complement to the main -Wswitch-enum warning (which
warns whenever a switch over enum without a default doesn't cover all values of
 the enum) & has been an an-doc coding convention in LLVM and Clang in my
experience. The purpose is to ensure there's never a "dead" default in a
switch-over-enum because this would hide future -Wswitch-enum errors.

The name warning has a separate flag name so it can be disabled but it's grouped
under -Wswitch-enum & is on-by-default because of this.

The existing violations of this rule in test cases have had the warning disabled
& I've added a specific test for the new behavior (many negative cases already
exist in the same test file - and none regressed - so I didn't add more).

Reviewed by Ted Kremenek ( http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20120116/051690.html )

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@148640 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 2 deletions

diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index a53e397243..0be3e43b5a 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -924,11 +924,17 @@ Sema::ActOnFinishSwitchStmt(SourceLocation SwitchLoc, Stmt *Switch,
 
         if (RI == CaseRanges.end() || EI->first < RI->first) {
           hasCasesNotInSwitch = true;
-          if (!TheDefaultStmt)
-            UnhandledNames.push_back(EI->second->getDeclName());
+          UnhandledNames.push_back(EI->second->getDeclName());
         }
       }
 
+      if (TheDefaultStmt) {
+        if (UnhandledNames.size() == 0)
+          Diag(TheDefaultStmt->getDefaultLoc(), diag::warn_unreachable_default);
+        else
+          UnhandledNames.clear();
+      }
+
       // Produce a nice diagnostic if multiple values aren't handled.
       switch (UnhandledNames.size()) {
       case 0: break;