PR43674: fix incorrect constant evaluation of 'switch' where no case

label corresponds to the condition.

llvm-svn: 374954

Author: zygoloid

clang/lib/AST/ExprConstant.cpp

@@ -4435,7 +4435,7 @@ static EvalStmtResult EvaluateSwitch(StmtResult &Result, EvalInfo &Info,
   }
 
   if (!Found)
-    return Scope.destroy() ? ESR_Failed : ESR_Succeeded;
+    return Scope.destroy() ? ESR_Succeeded : ESR_Failed;
 
   // Search the switch body for the switch case and evaluate it from there.
   EvalStmtResult ESR = EvaluateStmt(Result, Info, SS->getBody(), Found);

clang/test/SemaCXX/constant-expression-cxx1y.cpp

@@ -627,6 +627,12 @@ namespace assignment_op {
 }
 
 namespace switch_stmt {
+  constexpr bool no_such_case(int n) {
+    switch (n) { case 1: return false; }
+    return true;
+  }
+  static_assert(no_such_case(0), "");
+
   constexpr int f(char k) {
     bool b = false;
     int z = 6;