c++, contracts: Move result decls into contract scope.

iains · iains · commit 63117eae08e1 · 2025-01-25T20:43:40.000Z
Signed-off-by: Iain Sandoe &lt;iain@sandoe.co.uk&gt;
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
@@ -31376,15 +31376,6 @@ cp_parser_contract_attribute_spec (cp_parser *parser, tree attribute,
       /* Enable location wrappers when parsing contracts.  */
       auto suppression = make_temp_override (suppress_location_wrappers, 0);
 
-      /* Build a fake variable for the result identifier.  */
-      tree result = NULL_TREE;
-      if (identifier)
-	{
-	  begin_scope (sk_block, NULL_TREE);
-	  result = make_postcondition_variable (identifier);
-	  ++processing_template_decl;
-	}
-
       bool old_flag_contracts_nonattr_noconst = flag_contracts_nonattr_noconst;
       /* The should_constify value should account for all the mixed flags.  */
       flag_contracts_nonattr_noconst = !should_constify;
@@ -31401,13 +31392,25 @@ cp_parser_contract_attribute_spec (cp_parser *parser, tree attribute,
       ++processing_contract_condition;
       if (postcondition_p)
 	++processing_contract_postcondition;
+      tree result = NULL_TREE;
+      if (identifier)
+	{
+	  /* Build a fake variable for the result identifier.  */
+	  result = make_postcondition_variable (identifier);
+	  ++processing_template_decl;
+	}
       processing_postcondition = postcondition_p;
       should_constify_contract = should_constify;
       cp_expr condition = cp_parser_conditional_expression (parser);
+      /* Build the contract.  */
+      contract = grok_contract (attribute, mode, result, condition, loc);
+      if (identifier)
+	--processing_template_decl;
       if (postcondition_p)
 	--processing_contract_postcondition;
       --processing_contract_condition;
       pop_bindings_and_leave_scope ();
+
       /* Revert (any) constification of the current class object.  */
       current_class_ref = current_class_ref_copy;
       flag_contracts_nonattr_noconst = old_flag_contracts_nonattr_noconst;
@@ -31421,15 +31424,6 @@ cp_parser_contract_attribute_spec (cp_parser *parser, tree attribute,
 	 we need to search the condition for errors.  */
       else if (contains_error_p (condition))
 	cp_parser_skip_up_to_closing_square_bracket (parser);
-
-      /* Build the contract.  */
-      contract = grok_contract (attribute, mode, result, condition, loc);
-      /* Leave our temporary scope for the postcondition result.  */
-      if (result)
-	{
-	  --processing_template_decl;
-	  pop_bindings_and_leave_scope ();
-	}
     }
 
   if (!flag_contracts)
@@ -31463,22 +31457,16 @@ void cp_parser_late_contract_condition (cp_parser *parser,
   if (TREE_CODE (contract) == POSTCONDITION_STMT)
     identifier = POSTCONDITION_IDENTIFIER (contract);
 
-  /* Build a fake variable for the result identifier.  */
-  tree result = NULL_TREE;
+  tree type = TREE_TYPE (TREE_TYPE (fn));
   if (identifier)
     {
       /* TODO: Can we guarantee that the identifier has a location? */
       location_t loc = cp_expr_location (contract);
-      tree type = TREE_TYPE (TREE_TYPE (fn));
       if (!check_postcondition_result (fn, type, loc))
 	{
 	  invalidate_contract (contract);
 	  return;
 	}
-
-      begin_scope (sk_block, NULL_TREE);
-      result = make_postcondition_variable (identifier, type);
-      ++processing_template_decl;
     }
 
   /* In C++20 contracts, 'this' is not allowed in preconditions of
@@ -31524,15 +31512,28 @@ void cp_parser_late_contract_condition (cp_parser *parser,
   ++processing_contract_condition;
   if (POSTCONDITION_P (contract))
     ++processing_contract_postcondition;
+  /* Build a fake variable for the result identifier.  */
+  tree result = NULL_TREE;
+  if (identifier)
+    {
+      result = make_postcondition_variable (identifier, type);
+      ++processing_template_decl;
+    }
   condition = cp_parser_conditional_expression (parser);
+  /* Commit to changes.  */
+  update_late_contract (contract, result, condition);
+  /* Leave our temporary scope for the postcondition result.  */
+  if (result)
+    --processing_template_decl;
   if (POSTCONDITION_P (contract))
     --processing_contract_postcondition;
   --processing_contract_condition;
   pop_bindings_and_leave_scope ();
 
+  flag_contracts_nonattr_noconst = old_flag_contracts_nonattr_noconst;
+
   if (cp_lexer_next_token_is_not (parser->lexer, CPP_EOF))
-      error_at (input_location,
-		"expected conditional-expression");
+    error_at (input_location, "expected conditional-expression");
 
   /* Revert to the main lexer.  */
   cp_parser_pop_lexer (parser);
@@ -31543,17 +31544,6 @@ void cp_parser_late_contract_condition (cp_parser *parser,
   current_class_ref = saved_ccr;
   current_class_ptr = saved_ccp;
   contract_class_ptr = saved_contract_ccp;
-
-  /* Commit to changes.  */
-  update_late_contract (contract, result, condition);
-  flag_contracts_nonattr_noconst = old_flag_contracts_nonattr_noconst;
-
-  /* Leave our temporary scope for the postcondition result.  */
-  if (result)
-    {
-      --processing_template_decl;
-      pop_bindings_and_leave_scope ();
-    }
 }
 
 static contract_modifier
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
@@ -12025,12 +12025,13 @@ tsubst_contract (tree decl, tree t, tree args, tsubst_flags_t complain,
 
   tree r = copy_node (t);
 
-  /* Rebuild the result variable.  */
+  /* Rebuild the result variable, if present.  */
+  tree oldvar = NULL_TREE;
+  tree newvar = NULL_TREE;
   if (type && POSTCONDITION_P (t) && POSTCONDITION_IDENTIFIER (t))
     {
-      tree oldvar = POSTCONDITION_IDENTIFIER (t);
-
-      tree newvar = copy_node (oldvar);
+      oldvar = POSTCONDITION_IDENTIFIER (t);
+      newvar = copy_node (oldvar);
       TREE_TYPE (newvar) = type;
       DECL_CONTEXT (newvar) = decl;
       POSTCONDITION_IDENTIFIER (r) = newvar;
@@ -12040,34 +12041,38 @@ tsubst_contract (tree decl, tree t, tree args, tsubst_flags_t complain,
       if (!auto_p)
 	if (!check_postcondition_result (decl, type, loc))
 	  return invalidate_contract (r);
-
-      /* Make the variable available for lookup.  */
-      register_local_specialization (newvar, oldvar);
     }
 
-  /* Instantiate the condition.  If the return type is undeduced, process
-     the expression as if inside a template to avoid spurious type errors.  */
-  bool const_p = get_contract_const (t);
+  /* Should we const-ify this condition?  */
   bool old_flag_contracts_nonattr_noconst = flag_contracts_nonattr_noconst;
+  bool const_p = get_contract_const (t);
   flag_contracts_nonattr_noconst = !const_p;
 
+  /* Instantiate the condition.  If the return type is undeduced, process
+     the expression as if inside a template to avoid spurious type errors.  */
+  begin_scope (sk_contract, decl);
+  ++processing_contract_condition;
   if (auto_p)
     ++processing_template_decl;
-  ++processing_contract_condition;
   if (POSTCONDITION_P (t))
     ++processing_contract_postcondition;
+  if (newvar)
+    /* Make the variable available for lookup.  */
+    register_local_specialization (newvar, oldvar);
 
   CONTRACT_CONDITION (r)
       = tsubst_expr (CONTRACT_CONDITION (t), args, complain, in_decl);
-  if (POSTCONDITION_P (t))
-    --processing_contract_postcondition;
-  --processing_contract_condition;
-  if (auto_p)
-    --processing_template_decl;
 
   /* And the comment.  */
   CONTRACT_COMMENT (r)
       = tsubst_expr (CONTRACT_COMMENT (r), args, complain, in_decl);
+
+  if (POSTCONDITION_P (t))
+    --processing_contract_postcondition;
+  if (auto_p)
+    --processing_template_decl;
+  --processing_contract_condition;
+  pop_bindings_and_leave_scope ();
   flag_contracts_nonattr_noconst = old_flag_contracts_nonattr_noconst;
 
   return r;
@@ -12120,14 +12125,12 @@ tsubst_contract_attribute (tree decl, tree t, tree args,
    as needed.  */
 
 void
-tsubst_contract_attributes (tree decl, tree args, tsubst_flags_t complain, tree in_decl)
+tsubst_contract_attributes (tree decl, tree args, tsubst_flags_t complain,
+			    tree in_decl)
 {
   tree list = copy_list (DECL_ATTRIBUTES (decl));
-  for (tree attr = list; attr; attr = CONTRACT_CHAIN (attr))
-    {
-      if (cxx_contract_attribute_p (attr))
-	tsubst_contract_attribute (decl, attr, args, complain, in_decl);
-    }
+  for (tree attr = find_contract (list); attr; attr = CONTRACT_CHAIN (attr))
+    tsubst_contract_attribute (decl, attr, args, complain, in_decl);
   DECL_ATTRIBUTES (decl) = list;
 }
 
diff --git a/gcc/testsuite/g++.dg/contracts/cpp26/p2900-3-4-3-part2.C b/gcc/testsuite/g++.dg/contracts/cpp26/p2900-3-4-3-part2.C
@@ -0,0 +1,38 @@
+// { dg-options "-std=c++23 -fcontracts -fcontracts-nonattr" }
+
+// Check that result vars are not visible in function bodies.
+
+int free_fn (int x)
+  post (r: r > 5);
+
+int free_fn (int x)
+  post (r: r > 5)
+{ r += 1; return r;} // { dg-error {'r' was not declared in this scope} }
+
+struct X {
+  int fn0 (int x)
+    post (res: res > 5)
+    { res = 15; return res; } // { dg-error {'res' was not declared in this scope} }
+
+  int fn1 (int x)
+    post (res: res > 5);
+};
+
+int
+X::fn1 (int y)
+    post (ans: ans > 5)
+    { ans = 15; return 1; } // { dg-error {'ans' was not declared in this scope} }
+
+template <class T>
+int
+postcond (T x) post (res: res > 3); 
+
+template <class T>
+int
+postcond (T x) post (out: out > 3)
+{ out = 5;  return x; } // { dg-error {'out' was not declared in this scope} }
+
+int foo (int x)
+{
+  return postcond (4);
+}
