Ignore type change in DerivedToBase cast

Summary:
public
Backend needs to know whether parameter has Derived* type - otherwise subtyping in backend doesn't work. Skipping `DerivedToBase` does that

Reviewed By: dulmarod

Differential Revision: D2890673

fb-gh-sync-id: a79abbc

infer/src/clang/cTrans_utils.ml

@@ -398,7 +398,7 @@ let dereference_value_from_result sil_loc trans_result ~strip_pointer =
 let cast_operation context cast_kind exps cast_typ sil_loc is_objc_bridged =
   let (exp, typ) = extract_exp_from_list exps "" in
   let exp_typ = match cast_kind with
-    | `UncheckedDerivedToBase -> typ  (* This cast ignores change of type *)
+    | `UncheckedDerivedToBase | `DerivedToBase -> typ  (* These casts ignore change of type *)
     | _ -> cast_typ (* by default use the return type of cast expr *) in 
   if is_objc_bridged then
     let id, instr, exp = create_cast_instrs context exp typ cast_typ sil_loc in

infer/tests/codetoanalyze/cpp/frontend/types/inheritance.cpp.dot

@@ -3,7 +3,7 @@ digraph iCFG {
 	
 
 	 24 -> 23 ;
-23 [label="23:  DeclStmt \n   n$13=_fun___new(sizeof(class Sub ):unsigned long ) [line 23]\n  *&s1:class Base *=n$13 [line 23]\n  REMOVE_TEMPS(n$13); [line 23]\n " shape="box"]
+23 [label="23:  DeclStmt \n   n$13=_fun___new(sizeof(class Sub ):unsigned long ) [line 23]\n  *&s1:class Sub *=n$13 [line 23]\n  REMOVE_TEMPS(n$13); [line 23]\n " shape="box"]
 	
 
 	 23 -> 22 ;

infer/tests/codetoanalyze/cpp/frontend/types/inheritance_field.cpp.dot

@@ -3,7 +3,7 @@ digraph iCFG {
 	
 
 	 41 -> 40 ;
-40 [label="40:  DeclStmt \n   n$2=*&s:class Sub * [line 68]\n  *&b:struct Base1 *=n$2 [line 68]\n  REMOVE_TEMPS(n$2); [line 68]\n  NULLIFY(&s,false); [line 68]\n " shape="box"]
+40 [label="40:  DeclStmt \n   n$2=*&s:class Sub * [line 68]\n  *&b:class Sub *=n$2 [line 68]\n  REMOVE_TEMPS(n$2); [line 68]\n  NULLIFY(&s,false); [line 68]\n " shape="box"]
 	
 
 	 40 -> 39 ;
@@ -75,7 +75,7 @@ digraph iCFG {
 	
 
 	 22 -> 21 ;
-21 [label="21:  DeclStmt \n   *&b:struct Base1 &=&s [line 45]\n " shape="box"]
+21 [label="21:  DeclStmt \n   *&b:class Sub &=&s [line 45]\n " shape="box"]
 	
 
 	 21 -> 20 ;
@@ -94,7 +94,7 @@ digraph iCFG {
 	
 
 	 17 -> 16 ;
-16 [label="16:  DeclStmt \n   n$2=*&s:class Sub * [line 39]\n  *&b:struct Base1 *=n$2 [line 39]\n  REMOVE_TEMPS(n$2); [line 39]\n  NULLIFY(&s,false); [line 39]\n " shape="box"]
+16 [label="16:  DeclStmt \n   n$2=*&s:class Sub * [line 39]\n  *&b:class Sub *=n$2 [line 39]\n  REMOVE_TEMPS(n$2); [line 39]\n  NULLIFY(&s,false); [line 39]\n " shape="box"]
 	
 
 	 16 -> 15 ;