Don't build expressions for invalid casts.

This matches how we normally perform semantic analysis for other sorts
of invalid expressions: it means we don't have to reason about invalid
sub-expressions.

Fixes PR16680.

llvm-svn: 187276

clang/lib/Sema/SemaCast.cpp

@@ -554,6 +554,7 @@ void CastOperation::CheckDynamicCast() {
   } else {
     Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ref_or_ptr)
       << this->DestType << DestRange;
+    SrcExpr = ExprError();
     return;
   }
 
@@ -563,11 +564,14 @@ void CastOperation::CheckDynamicCast() {
   } else if (DestRecord) {
     if (Self.RequireCompleteType(OpRange.getBegin(), DestPointee,
                                  diag::err_bad_dynamic_cast_incomplete,
-                                 DestRange))
+                                 DestRange)) {
+      SrcExpr = ExprError();
       return;
+    }
   } else {
     Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class)
       << DestPointee.getUnqualifiedType() << DestRange;
+    SrcExpr = ExprError();
     return;
   }
 
@@ -583,6 +587,7 @@ void CastOperation::CheckDynamicCast() {
     } else {
       Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ptr)
         << OrigSrcType << SrcExpr.get()->getSourceRange();
+      SrcExpr = ExprError();
       return;
     }
   } else if (DestReference->isLValueReferenceType()) {
@@ -599,11 +604,14 @@ void CastOperation::CheckDynamicCast() {
   if (SrcRecord) {
     if (Self.RequireCompleteType(OpRange.getBegin(), SrcPointee,
                                  diag::err_bad_dynamic_cast_incomplete,
-                                 SrcExpr.get()))
+                                 SrcExpr.get())) {
+      SrcExpr = ExprError();
       return;
+    }
   } else {
     Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_class)
       << SrcPointee.getUnqualifiedType() << SrcExpr.get()->getSourceRange();
+    SrcExpr = ExprError();
     return;
   }
 
@@ -617,6 +625,7 @@ void CastOperation::CheckDynamicCast() {
   if (!DestPointee.isAtLeastAsQualifiedAs(SrcPointee)) {
     Self.Diag(OpRange.getBegin(), diag::err_bad_cxx_cast_qualifiers_away)
       << CT_Dynamic << OrigSrcType << this->DestType << OpRange;
+    SrcExpr = ExprError();
     return;
   }
 
@@ -632,8 +641,10 @@ void CastOperation::CheckDynamicCast() {
   if (DestRecord && Self.IsDerivedFrom(SrcPointee, DestPointee)) {
     if (Self.CheckDerivedToBaseConversion(SrcPointee, DestPointee,
                                            OpRange.getBegin(), OpRange, 
-                                           &BasePath))
-        return;
+                                           &BasePath)) {
+      SrcExpr = ExprError();
+      return;
+    }
         
     Kind = CK_DerivedToBase;
 
@@ -651,6 +662,7 @@ void CastOperation::CheckDynamicCast() {
   if (!cast<CXXRecordDecl>(SrcDecl)->isPolymorphic()) {
     Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_polymorphic)
       << SrcPointee.getUnqualifiedType() << SrcExpr.get()->getSourceRange();
+    SrcExpr = ExprError();
   }
   Self.MarkVTableUsed(OpRange.getBegin(), 
                       cast<CXXRecordDecl>(SrcRecord->getDecl()));
@@ -674,9 +686,11 @@ void CastOperation::CheckConstCast() {
 
   unsigned msg = diag::err_bad_cxx_cast_generic;
   if (TryConstCast(Self, SrcExpr, DestType, /*CStyle*/false, msg) != TC_Success
-      && msg != 0)
+      && msg != 0) {
     Self.Diag(OpRange.getBegin(), msg) << CT_Const
       << SrcExpr.get()->getType() << DestType << OpRange;
+    SrcExpr = ExprError();
+  }
 }
 
 /// Check that a reinterpret_cast\<DestType\>(SrcExpr) is not used as upcast
@@ -804,6 +818,7 @@ void CastOperation::CheckReinterpretCast() {
       diagnoseBadCast(Self, msg, CT_Reinterpret, OpRange, SrcExpr.get(),
                       DestType, /*listInitialization=*/false);
     }
+    SrcExpr = ExprError();
   } else if (tcr == TC_Success) {
     if (Self.getLangOpts().ObjCAutoRefCount)
       checkObjCARCConversion(Sema::CCK_OtherCast);
@@ -865,6 +880,7 @@ void CastOperation::CheckStaticCast() {
       diagnoseBadCast(Self, msg, CT_Static, OpRange, SrcExpr.get(), DestType,
                       /*listInitialization=*/false);
     }
+    SrcExpr = ExprError();
   } else if (tcr == TC_Success) {
     if (Kind == CK_BitCast)
       checkCastAlign();
@@ -1981,9 +1997,6 @@ void CastOperation::CheckCXXCStyleCast(bool FunctionalStyle,
     }
 
     SrcExpr = Self.IgnoredValueConversions(SrcExpr.take());
-    if (SrcExpr.isInvalid())
-      return;
-
     return;
   }
 

clang/test/SemaCXX/cast-conversion.cpp

@@ -16,8 +16,7 @@ struct B { // expected-note 3 {{candidate constructor (the implicit copy constru
 int main () {
   B(10);	// expected-error {{no matching conversion for functional-style cast from 'int' to 'B'}}
   (B)10;	// expected-error {{no matching conversion for C-style cast from 'int' to 'B'}}
-  static_cast<B>(10);	// expected-error {{no matching conversion for static_cast from 'int' to 'B'}} \\
-			// expected-warning {{expression result unused}}
+  static_cast<B>(10);	// expected-error {{no matching conversion for static_cast from 'int' to 'B'}}
 }
 
 template<class T>
@@ -73,3 +72,10 @@ struct AmbiguousCast {
 long long AmbiguousCastFunc(AmbiguousCast& a) {
   return static_cast<long long>(a); // expected-error {{ambiguous conversion for static_cast from 'AmbiguousCast' to 'long long'}}
 }
+
+namespace PR16680 {
+  void f(int (*__pf)());
+  int g() {
+    f(reinterpret_cast<int>(0.0f)); // expected-error {{reinterpret_cast from 'float' to 'int' is not allowed}}
+  }
+}