c++, contracts: omit unnecessary const-wrappers

We need to view class pointers as const, which we do by wrapping
them in a view convert expression.  However, we do not need to do
this if the original is already const-qualified.

gcc/cp/ChangeLog:

	* contracts.cc (view_as_const): Check for const-qualified
	class pointer before wrapping it.
	* parser.cc (cp_parser_late_contract_condition): Use revised
	handling of const-ification of class pointers.
	(cp_parser_contract_assert): Likewise.
	(cp_parser_function_contract_specifier): Likewise.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
Co-authored-by: Jason Merrill <jason@redhat.com>

Author: iains

gcc/cp/contracts.cc

@@ -482,8 +482,10 @@ finish_contract_condition (cp_expr condition)
 tree
 view_as_const (tree decl)
 {
-  if (!contract_const_wrapper_p (decl))
+  if (decl
+      && !CP_TYPE_CONST_P (TREE_TYPE (decl)))
     {
+      gcc_checking_assert (!contract_const_wrapper_p (decl));
       tree ctype = TREE_TYPE (decl);
       location_t loc =
 	  EXPR_P (decl) ? EXPR_LOCATION (decl) : DECL_SOURCE_LOCATION (decl);

gcc/cp/parser.cc

@@ -33582,9 +33582,7 @@ cp_parser_late_contract_condition (cp_parser *parser, tree fn, tree contract)
 
   /* If we have a current class object, we need to consider
      it const when processing the contract condition.  */
-  tree current_class_ref_copy = current_class_ref;
-  if (flag_contracts && current_class_ref_copy)
-    current_class_ref = view_as_const (current_class_ref_copy);
+  current_class_ref = view_as_const (current_class_ref);
 
   /* Parse the condition, ensuring that parameters or the return variable
      aren't flagged for use outside the body of a function.  */
@@ -33691,8 +33689,7 @@ cp_parser_contract_assert (cp_parser *parser, cp_token *token)
   /* If we have a current class object, see if we need to consider
      it const when processing the contract condition.  */
   tree current_class_ref_copy = current_class_ref;
-  if (current_class_ref_copy)
-    current_class_ref = view_as_const (current_class_ref_copy);
+  current_class_ref = view_as_const (current_class_ref);
 
   /* Parse the condition.  */
   begin_scope (sk_contract, current_function_decl);
@@ -33857,8 +33854,7 @@ cp_parser_function_contract_specifier (cp_parser *parser)
       /* If we have a current class object, see if we need to consider
        it const when processing the contract condition.  */
       tree current_class_ref_copy = current_class_ref;
-      if (current_class_ref_copy)
-      current_class_ref = view_as_const (current_class_ref_copy);
+      current_class_ref = view_as_const (current_class_ref);
 
       /* Parse the condition, ensuring that parameters or the return variable
        aren't flagged for use outside the body of a function.  */