1 files changed, 43 insertions, 9 deletions

diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index e8cd6b081de16..1453424385033 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -368,6 +368,21 @@ static bool CmpCaseVals(const std::pair<llvm::APSInt, CaseStmt*>& lhs,
   return false;
 }
 
+/// GetTypeBeforeIntegralPromotion - Returns the pre-promotion type of
+/// potentially integral-promoted expression @p expr.
+static QualType GetTypeBeforeIntegralPromotion(const Expr* expr) {
+  const ImplicitCastExpr *ImplicitCast =
+      dyn_cast_or_null<ImplicitCastExpr>(expr);
+  if (ImplicitCast != NULL) {
+    const Expr *ExprBeforePromotion = ImplicitCast->getSubExpr();
+    QualType TypeBeforePromotion = ExprBeforePromotion->getType();
+    if (TypeBeforePromotion->isIntegralType()) {
+      return TypeBeforePromotion;
+    }
+  }
+  return expr->getType();
+}
+
 Action::OwningStmtResult
 Sema::ActOnFinishSwitchStmt(SourceLocation SwitchLoc, StmtArg Switch,
                             StmtArg Body) {
@@ -382,11 +397,30 @@ Sema::ActOnFinishSwitchStmt(SourceLocation SwitchLoc, StmtArg Switch,
   Expr *CondExpr = SS->getCond();
   QualType CondType = CondExpr->getType();
 
-  if (!CondExpr->isTypeDependent() &&
-      !CondType->isIntegerType()) { // C99 6.8.4.2p1
-    Diag(SwitchLoc, diag::err_typecheck_statement_requires_integer)
-      << CondType << CondExpr->getSourceRange();
-    return StmtError();
+  // C++ 6.4.2.p2:
+  // Integral promotions are performed (on the switch condition).
+  //
+  // A case value unrepresentable by the original switch condition
+  // type (before the promotion) doesn't make sense, even when it can
+  // be represented by the promoted type.  Therefore we need to find
+  // the pre-promotion type of the switch condition.
+  QualType CondTypeBeforePromotion =
+      GetTypeBeforeIntegralPromotion(CondExpr);
+
+  if (!CondExpr->isTypeDependent()) {
+    if (!CondType->isIntegerType()) { // C99 6.8.4.2p1
+      Diag(SwitchLoc, diag::err_typecheck_statement_requires_integer)
+          << CondType << CondExpr->getSourceRange();
+      return StmtError();
+    }
+
+    if (CondTypeBeforePromotion->isBooleanType()) {
+      // switch(bool_expr) {...} is often a programmer error, e.g.
+      //   switch(n && mask) { ... }  // Doh - should be "n & mask".
+      // One can always use an if statement instead of switch(bool_expr).
+      Diag(SwitchLoc, diag::warn_bool_switch_condition)
+          << CondExpr->getSourceRange();
+    }
   }
 
   // Get the bitwidth of the switched-on value before promotions.  We must
@@ -395,8 +429,8 @@ Sema::ActOnFinishSwitchStmt(SourceLocation SwitchLoc, StmtArg Switch,
     = CondExpr->isTypeDependent() || CondExpr->isValueDependent();
   unsigned CondWidth
     = HasDependentValue? 0
-                       : static_cast<unsigned>(Context.getTypeSize(CondType));
-  bool CondIsSigned = CondType->isSignedIntegerType();
+      : static_cast<unsigned>(Context.getTypeSize(CondTypeBeforePromotion));
+  bool CondIsSigned = CondTypeBeforePromotion->isSignedIntegerType();
 
   // Accumulate all of the case values in a vector so that we can sort them
   // and detect duplicates.  This vector contains the APInt for the case after
@@ -448,7 +482,7 @@ Sema::ActOnFinishSwitchStmt(SourceLocation SwitchLoc, StmtArg Switch,
 
       // If the LHS is not the same type as the condition, insert an implicit
       // cast.
-      ImpCastExprToType(Lo, CondType);
+      ImpCastExprToType(Lo, CondType, CastExpr::CK_IntegralCast);
       CS->setLHS(Lo);
 
       // If this is a case range, remember it in CaseRanges, otherwise CaseVals.
@@ -504,7 +538,7 @@ Sema::ActOnFinishSwitchStmt(SourceLocation SwitchLoc, StmtArg Switch,
 
         // If the LHS is not the same type as the condition, insert an implicit
         // cast.
-        ImpCastExprToType(Hi, CondType);
+        ImpCastExprToType(Hi, CondType, CastExpr::CK_IntegralCast);
         CR->setRHS(Hi);
 
         // If the low value is bigger than the high value, the case is empty.