objc-arc: desugar certain type and improve on diagnostic for

ownership qualifier cast which won't work.
// rdar://10244607

llvm-svn: 143258

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -3043,8 +3043,7 @@ def err_arc_mismatched_cast : Error<
   "an Objective-C pointer|an indirect pointer to an Objective-C pointer}1"
   " to %3 is disallowed with ARC">;
 def err_arc_nolifetime_behavior : Error<
-  "casting expression of type %1 to type %0 with qualified lifetime"
-  "will not change object lifetime">;
+  "explicit ownership qualifier on cast result would have no effect">;
 def err_arc_objc_object_in_struct : Error<
   "ARC forbids Objective-C objects in structs or unions">;
 def err_arc_objc_property_default_assign_on_object : Error<

clang/lib/Sema/SemaExprObjC.cpp

@@ -1937,17 +1937,27 @@ Sema::CheckObjCARCConversion(SourceRange castRange, QualType castType,
   if (exprACTC == castACTC) {
     // check for viablity and report error if casting an rvalue to a
     // life-time qualifier.
-    if ((castACTC == ACTC_retainable) && 
-        isa<AttributedType>(castType) &&
-        (castType.getObjCLifetime() !=  Qualifiers::OCL_None) &&
+    if ((castACTC == ACTC_retainable) &&
         (CCK == CCK_CStyleCast || CCK == CCK_OtherCast) &&
-        castType != castExprType) {
-      SourceLocation loc =
-        (castRange.isValid() ? castRange.getBegin() 
-                             : castExpr->getExprLoc());
-      Diag(loc, diag::err_arc_nolifetime_behavior)
-        << effCastType << castExprType 
-        << castRange << castExpr->getSourceRange();
+        (castType != castExprType)) {
+      const Type *DT = castType.getTypePtr();
+      QualType QDT = castType;
+      // We desugar some types but not others. We ignore those
+      // that cannot happen in a cast; i.e. auto, and those which
+      // should not be de-sugared; i.e typedef.
+      if (const ParenType *PT = dyn_cast<ParenType>(DT))
+        QDT = PT->desugar();
+      else if (const TypeOfType *TP = dyn_cast<TypeOfType>(DT))
+        QDT = TP->desugar();
+      else if (const AttributedType *AT = dyn_cast<AttributedType>(DT))
+        QDT = AT->desugar();
+      if (QDT != castType &&
+          QDT.getObjCLifetime() !=  Qualifiers::OCL_None) {
+        SourceLocation loc =
+          (castRange.isValid() ? castRange.getBegin() 
+                              : castExpr->getExprLoc());
+        Diag(loc, diag::err_arc_nolifetime_behavior);
+      }
     }
     return ACR_okay;
   }

clang/test/SemaObjC/arc-objc-lifetime.m

@@ -17,12 +17,14 @@ typedef __autoreleasing NSString * AUTORELEASEPNSString;
 - (CFStringRef)myString
 {
     CFStringRef myString =
-      (__bridge CFStringRef) (__strong NSString *)CFBridgingRelease(); // expected-error {{casting expression of type 'NSString *' to type 'NSString *__strong' with qualified lifetimewill not change object lifetime}}
+      (__bridge CFStringRef) (__strong NSString *)CFBridgingRelease(); // expected-error {{explicit ownership qualifier on cast result would have no effect}}
 
     myString =
-      (__bridge CFStringRef) (__autoreleasing PNSString) CFBridgingRelease(); // expected-error {{casting expression of type 'NSString *' to type '__autoreleasing PNSString' (aka 'NSString *__autoreleasing') with qualified lifetimewill not change object}}
+      (__bridge CFStringRef) (__autoreleasing PNSString) CFBridgingRelease(); // expected-error {{explicit ownership qualifier on cast result would have no effect}}
     myString =
       (__bridge CFStringRef) (AUTORELEASEPNSString) CFBridgingRelease(); // OK
+    myString =
+      (__bridge CFStringRef) (typeof(__strong NSString *)) CFBridgingRelease(); // expected-error {{explicit ownership qualifier on cast result would have no effect}}
     return myString;
 }
 

clang/test/SemaObjC/arc-unavailable-for-weakref.m

@@ -16,7 +16,7 @@ int main() {
 
   ns1 = (__weak sub *)obj; // expected-error {{assignment of a weak-unavailable object to a __weak object}} \
                            // expected-error {{class is incompatible with __weak references}} \
-                           // expected-error {{casting expression of type 'id' to type 'sub *__weak' with qualified lifetimewill not change object lifetime}}
+                           // expected-error {{explicit ownership qualifier on cast result would have no effect}}
 }
 
 // rdar://9732636
@@ -32,7 +32,7 @@ NOWEAK * Test1() {
 
   __weak id weak2 = strong1; // expected-error {{assignment of a weak-unavailable object to a __weak object}}
   return (__weak id)strong1; // expected-error {{cast of weak-unavailable object of type 'NOWEAK *' to a __weak object of type '__weak id'}} \
-                             // expected-error {{casting expression of type 'NOWEAK *' to type '__weak id' with qualified lifetimewill not change object lifetime}}
+                             // expected-error {{explicit ownership qualifier on cast result would have no effect}}
 }
 
 @protocol P @end
@@ -45,6 +45,6 @@ NOWEAK<P, P1> * Test2() {
 
   __weak id<P> weak2 = strong1; // expected-error {{assignment of a weak-unavailable object to a __weak object}}
   return (__weak id<P>)strong1; // expected-error {{cast of weak-unavailable object of type 'NOWEAK<P,P1> *' to a __weak object of type '__weak id<P>'}} \
-                                // expected-error {{casting expression of type 'NOWEAK<P,P1> *' to type '__weak id<P>' with qualified lifetimewill not change object lifetime}}
+                                // expected-error {{explicit ownership qualifier on cast result would have no effect}}
 }
 

clang/test/SemaObjCXX/arc-unavailable-for-weakref.mm

@@ -16,7 +16,7 @@ int main() {
 
   ns1 = (__weak sub *)obj; // expected-error {{assignment of a weak-unavailable object to a __weak object}} \
                            // expected-error {{class is incompatible with __weak references}} \
-                           // expected-error {{casting expression of type 'id' to type 'sub *__weak' with qualified lifetimewill not change object lifetime}}
+                           // expected-error {{explicit ownership qualifier on cast result would have no effect}}
 }
 
 // rdar://9732636
@@ -32,7 +32,7 @@ NOWEAK * Test1() {
 
   __weak id weak2 = strong1; // expected-error {{assignment of a weak-unavailable object to a __weak object}}
   return (__weak id)strong1; // expected-error {{cast of weak-unavailable object of type 'NOWEAK *' to a __weak object of type '__weak id'}} \
-                             // expected-error {{casting expression of type 'NOWEAK *' to type '__weak id' with qualified lifetimewill not change object lifetime}}
+                             // expected-error {{explicit ownership qualifier on cast result would have no effect}}
 }
 
 @protocol P @end
@@ -45,6 +45,6 @@ NOWEAK<P, P1> * Test2() {
 
   __weak id<P> weak2 = strong1; // expected-error {{assignment of a weak-unavailable object to a __weak object}}
   return (__weak id<P, P1>)strong1; // expected-error {{cast of weak-unavailable object of type 'NOWEAK<P,P1> *' to a __weak object of type '__weak id<P,P1>'}} \
-                                    // expected-error {{casting expression of type 'NOWEAK<P,P1> *' to type '__weak id<P,P1>' with qualified lifetimewill not change object lifetime}}
+                                    // expected-error {{explicit ownership qualifier on cast result would have no effect}}
 }