Assignment instruction: require base-type match, not an exact match

In Java it is common to find an assignment with types that match, but use different levels of symbol
indirection: for example, a struct initialiser might refer to the object being initialised using a symbol
type on the LHS, but using the full struct type for the constant initialiser. In general this level-of-
indirection mismatch is acceptable, including in C programs.

Author: smowton

src/util/std_code.h

@@ -17,6 +17,7 @@ Author: Daniel Kroening, [email protected]
 #include "expr_cast.h"
 #include "invariant.h"
 #include "std_expr.h"
+#include "base_type.h"
 #include "validate.h"
 #include "validate_code.h"
 
@@ -296,14 +297,14 @@ class code_assignt:public codet
 
   static void validate(
     const codet &code,
-    const namespacet &,
+    const namespacet &ns,
     const validation_modet vm = validation_modet::INVARIANT)
   {
     check(code, vm);
 
     DATA_CHECK(
       vm,
-      code.op0().type() == code.op1().type(),
+      base_type_eq(code.op0().type(), code.op1().type(), ns),
       "lhs and rhs of assignment must have same type");
   }