From 04d518c6f15a1147bc205f1b5abbbaf023a10b9e Mon Sep 17 00:00:00 2001
From: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
Date: Wed, 22 Nov 2023 13:08:13 +0100
Subject: [PATCH] Add AST validation check for const in trait

Add a new check in AST validation pass that checks that no function
declaration in traits are declared const.

gcc/rust/ChangeLog:

	* checks/errors/rust-ast-validation.cc (ASTValidation::visit): Add
	const check.
	* checks/errors/rust-ast-validation.h: Add visit function prototype.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
---
 gcc/rust/ast/rust-ast-visitor.cc              |  1 -
 gcc/rust/checks/errors/rust-ast-validation.cc | 11 +++++++++++
 gcc/rust/checks/errors/rust-ast-validation.h  |  1 +
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/gcc/rust/ast/rust-ast-visitor.cc b/gcc/rust/ast/rust-ast-visitor.cc
index 4ec5c7cf1d0a..c1d6ec339231 100644
--- a/gcc/rust/ast/rust-ast-visitor.cc
+++ b/gcc/rust/ast/rust-ast-visitor.cc
@@ -17,7 +17,6 @@
 // <http://www.gnu.org/licenses/>.
 
 #include "rust-ast-visitor.h"
-#include "rust-ast-full-decls.h"
 #include "rust-ast.h"
 #include "rust-path.h"
 #include "rust-token.h"
diff --git a/gcc/rust/checks/errors/rust-ast-validation.cc b/gcc/rust/checks/errors/rust-ast-validation.cc
index 477e889c5129..8eac7b494025 100644
--- a/gcc/rust/checks/errors/rust-ast-validation.cc
+++ b/gcc/rust/checks/errors/rust-ast-validation.cc
@@ -17,6 +17,7 @@
 // <http://www.gnu.org/licenses/>.
 
 #include "rust-ast-validation.h"
+#include "rust-ast-full-decls.h"
 #include "rust-diagnostics.h"
 #include "rust-item.h"
 #include "rust-keyword-values.h"
@@ -116,6 +117,16 @@ ASTValidation::visit (AST::Function &function)
   AST::ContextualASTVisitor::visit (function);
 }
 
+void
+ASTValidation::visit (AST::TraitFunctionDecl &decl)
+{
+  const auto &qualifiers = decl.get_qualifiers ();
+
+  if (context.back () == Context::TRAIT && qualifiers.is_const ())
+    rust_error_at (decl.get_identifier ().get_locus (), ErrorCode::E0379,
+		   "functions in traits cannot be declared const");
+}
+
 void
 ASTValidation::visit (AST::Trait &trait)
 {
diff --git a/gcc/rust/checks/errors/rust-ast-validation.h b/gcc/rust/checks/errors/rust-ast-validation.h
index 1052168ea728..f1c3018d142d 100644
--- a/gcc/rust/checks/errors/rust-ast-validation.h
+++ b/gcc/rust/checks/errors/rust-ast-validation.h
@@ -41,6 +41,7 @@ class ASTValidation : public AST::ContextualASTVisitor
   virtual void visit (AST::Union &item);
   virtual void visit (AST::Function &function);
   virtual void visit (AST::Trait &trait);
+  virtual void visit (AST::TraitFunctionDecl &decl);
 };
 
 } // namespace Rust