Rewrite type compatibility testing to do type merging rather than just

testing compatibility.  This is necessary for some constructs, like merging
redeclarations.

Also, there are some ObjC changes to make sure that 
typesAreCompatible(a,b) == typesAreCompatible(b,a).  I don't have any 
ObjC code beyond the testsuite, so please tell me if there are any cases 
where this doesn't behave as expected.

llvm-svn: 55158

Author: eefriedman

clang/include/clang/AST/ASTContext.h

@@ -397,9 +397,6 @@ class ASTContext {
 
   /// Compatibility predicates used to check assignment expressions.
   bool typesAreCompatible(QualType, QualType); // C99 6.2.7p1
-  bool pointerTypesAreCompatible(QualType, QualType);  // C99 6.7.5.1p2
-  bool referenceTypesAreCompatible(QualType, QualType); // C++ 5.17p6
-  bool functionTypesAreCompatible(QualType, QualType); // C99 6.7.5.3p15
 
   bool isObjCIdType(QualType T) const {
     if (!IdStructType) // ObjC isn't enabled
@@ -416,6 +413,14 @@ class ASTContext {
     return T->getAsStructureType() == SelStructType;
   }
 
+  // Check the safety of assignment from LHS to RHS
+  bool canAssignObjCInterfaces(const ObjCInterfaceType *LHS, 
+                               const ObjCInterfaceType *RHS);
+
+  // Functions for calculating composite types
+  QualType mergeTypes(QualType, QualType);
+  QualType mergeFunctionTypes(QualType, QualType);
+
   //===--------------------------------------------------------------------===//
   //                    Integer Predicates
   //===--------------------------------------------------------------------===//