[Sema] Warn about omitting deprecated enumerator in switch

clang/include/clang/Sema/Sema.h

@@ -6747,6 +6747,9 @@ class Sema final : public SemaBase {
     /// example, in a for-range initializer).
     bool InLifetimeExtendingContext = false;
 
+    /// Whether evaluating an expression for a switch case label.
+    bool IsCaseExpr = false;
+
     /// Whether we should rebuild CXXDefaultArgExpr and CXXDefaultInitExpr.
     bool RebuildDefaultArgOrDefaultInit = false;
 

clang/lib/Parse/ParseExpr.cpp

@@ -275,6 +275,8 @@ ExprResult Parser::ParseArrayBoundExpression() {
 ExprResult Parser::ParseCaseExpression(SourceLocation CaseLoc) {
   EnterExpressionEvaluationContext ConstantEvaluated(
       Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+  Actions.currentEvaluationContext().IsCaseExpr = true;
+
   ExprResult LHS(ParseCastExpression(CastParseKind::AnyCastExpr, false,
                                      TypeCastState::NotTypeCast));
   ExprResult Res(ParseRHSOfBinaryExpression(LHS, prec::Conditional));

clang/lib/Sema/SemaAvailability.cpp

@@ -549,6 +549,11 @@ static void DoEmitAvailabilityWarning(Sema &S, AvailabilityResult K,
     return;
   }
   case AR_Deprecated:
+    // Don't diagnose deprecated values in case expressions: they still need to
+    // be handled for the switch to be considered covered.
+    if (S.currentEvaluationContext().IsCaseExpr)
+      return;
+
     diag = !ObjCPropertyAccess ? diag::warn_deprecated
                                : diag::warn_property_method_deprecated;
     diag_message = diag::warn_deprecated_message;

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 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

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -verify -Wswitch -triple x86_64-apple-macosx10.12 %s
+// RUN: %clang_cc1 -verify -Wswitch -Wreturn-type -triple x86_64-apple-macosx10.12 %s
 
 enum SwitchOne {
   Unavail __attribute__((availability(macos, unavailable))),
@@ -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 {
@@ -25,3 +25,24 @@ enum SwitchThree {
 void testSwitchThree(enum SwitchThree st) {
   switch (st) {} // expected-warning{{enumeration value 'New' not handled in switch}}
 }
+
+enum SwitchFour {
+  Red,
+  Green,
+  Blue [[deprecated]]
+};
+
+int testSwitchFour(enum SwitchFour e) {
+  switch (e) { // expected-warning{{enumeration value 'Blue' not handled in switch}}
+  case Red:   return 1;
+  case Green: return 2;
+  }
+} // expected-warning{{non-void function does not return a value in all control paths}}
+
+int testSwitchFourCovered(enum SwitchFour e) {
+  switch (e) {
+  case Red:   return 1;
+  case Green: return 2;
+  case Blue:  return 3; // no warning
+  }
+}

clang/test/SemaObjC/unguarded-availability.m

@@ -343,21 +343,21 @@ @interface BaseClass (CategoryWithNewProtocolRequirement) <NewProtocol>
 @end
 
 typedef enum {
-  AK_Dodo __attribute__((availability(macos, deprecated=10.3))), // expected-note 3 {{marked deprecated here}}
+  AK_Dodo __attribute__((availability(macos, deprecated=10.3))), // expected-note 1 {{marked deprecated here}}
   AK_Cat __attribute__((availability(macos, introduced=10.4))),
   AK_CyborgCat __attribute__((availability(macos, introduced=10.12))), // expected-note {{'AK_CyborgCat' has been marked as being introduced in macOS 10.12 here, but the deployment target is macOS 10.9}}
 } Animals;
 
 void switchAnimals(Animals a) {
   switch (a) {
-  case AK_Dodo: break; // expected-warning{{'AK_Dodo' is deprecated}}
+  case AK_Dodo: break; // no warn
   case AK_Cat: break;
   case AK_Cat|AK_CyborgCat: break; // expected-warning{{case value not in enum}}
   case AK_CyborgCat: break; // no warn
   }
 
   switch (a) {
-  case AK_Dodo...AK_CyborgCat: // expected-warning {{'AK_Dodo' is depr}}
+  case AK_Dodo...AK_CyborgCat: // no warn
     break;
   }