Allow equality with NullToPointer casts and add type compatibility check to GetOriginalValue

Author: kakje

clang/lib/Sema/SemaBounds.cpp

@@ -3672,20 +3672,6 @@ namespace {
     // State.G is assumed to contain expressions that produce the same value
     // as the source of the assignment.
     void RecordEqualityWithTarget(Expr *Target, CheckingState &State) {
-      // Do not record equality between the target and source if the source
-      // produces the same value as a NullToPointer cast.  This avoids
-      // recording equality between non-assignment-compatible variables
-      // with pointer types.  For example, for the assignments int *p = 0;
-      // array_ptr<int> a = 0; UEQ should not contain { 0, p, a }.  UEQ
-      // also should not contain { 0, p } and { 0, a } so that UEQ does not
-      // grow too large.
-      for (auto I = State.G.begin(); I != State.G.end(); ++I) {
-        if (CastExpr *CE = dyn_cast<CastExpr>(*I)) {
-          if (CE->getCastKind() == CastKind::CK_NullToPointer)
-            return;
-        }
-      }
-
       // If UEQ contains a set F of expressions that produce the same value
       // as the source, add the target to F.  This prevents UEQ from growing
       // too large and containing redundant equality information.  For example,
@@ -3821,8 +3807,17 @@ namespace {
         Lexicographic Lex(S.Context, nullptr);
         Expr *E = Lex.IgnoreValuePreservingOperations(S.Context, *I);
         DeclRefExpr *W = GetRValueVariable(E);
-        if (W != nullptr && !EqualValue(S.Context, V, W, nullptr))
-          return *I;
+        if (W != nullptr && !EqualValue(S.Context, V, W, nullptr)) {
+          // Any variable used as the orginal value of v must have a type that
+          // is compatible with the type of v.  Expression equality recorded in
+          // UEQ does not take types into account, so expressions in the same
+          // set in UEQ may have incompatible types.
+          Sema::AssignConvertType Conv =
+            S.CheckAssignmentConstraints(SourceLocation(), V->getType(), W->getType());
+          if (Conv == Sema::AssignConvertType::Compatible ||
+              Conv == Sema::AssignConvertType::CompatiblePointerDiscardsQualifiers)
+            return *I;
+        }
       }
 
       return nullptr;