[Sema] Warn about omitting deprecated enumerator in switch

clang/lib/Sema/SemaStmt.cpp

@@ -1667,8 +1667,12 @@ Sema::ActOnFinishSwitchStmt(SourceLocation SwitchLoc, Stmt *Switch,
         // Don't warn about omitted unavailable EnumConstantDecls.
         switch (EI->second->getAvailability()) {
         case AR_Deprecated:
-          // Omitting a deprecated constant is ok; it should never materialize.
+          // Deprecated enumerators still need to be handled: they may be
+          // deprecated, but can still occur.
+          break;
+
         case AR_Unavailable:
+          // Omitting an unavailable enumerator is ok; it should never occur.
           continue;
 
         case AR_NotYetIntroduced:

clang/test/Sema/switch-availability.c

@@ -15,7 +15,7 @@ enum SwitchTwo {
 };
 
 void testSwitchTwo(enum SwitchTwo st) {
-  switch (st) {} // expected-warning{{enumeration values 'Vim' and 'Emacs' not handled in switch}}
+  switch (st) {} // expected-warning{{enumeration values 'Ed', 'Vim' and 'Emacs' not handled in switch}}
 }
 
 enum SwitchThree {