Simplifies alias expression for dereferences

Signed-off-by: Felipe R. Monteiro <felisous@amazon.com>

Author: feliperodri

src/goto-instrument/contracts/assigns.cpp

@@ -26,7 +26,8 @@ assigns_clause_targett::assigns_clause_targett(
     contract(contract),
     init_block(),
     log(log_parameter),
-    local_target(typet())
+    local_target(typet()),
+    target_id(object_ptr.id())
 {
   INVARIANT(
     pointer_object.type().id() == ID_pointer,
@@ -74,6 +75,11 @@ exprt assigns_clause_targett::alias_expression(const exprt &lhs)
     return conjunction(condition);
   }
 
+  if(target_id == ID_dereference)
+  {
+    return conjunction(condition);
+  }
+
   const exprt lhs_offset = pointer_offset(lhs_ptr);
   const exprt target_offset = pointer_offset(target);
 

src/goto-instrument/contracts/assigns.h

@@ -16,7 +16,6 @@ Date: July 2021
 
 #include "contracts.h"
 
-#include <ansi-c/expr2c.h>
 #include <util/pointer_offset_size.h>
 
 /// \brief A base class for assigns clause targets
@@ -48,6 +47,7 @@ class assigns_clause_targett
   goto_programt init_block;
   messaget &log;
   symbol_exprt local_target;
+  const irep_idt &target_id;
 };
 
 class assigns_clauset