gccrs: refactor unused var lint

gcc/rust/ChangeLog:

	* checks/lints/unused-var/rust-unused-var-collector.cc (UnusedVarCollector::visit):
	Remove useless methods.
	* checks/lints/unused-var/rust-unused-var-collector.h: Same here.
	* checks/lints/unused-var/rust-unused-var-context.cc (UnusedVarContext::add_variable):
	Add used variables to set.
	(UnusedVarContext::mark_used): Remove method.
	(UnusedVarContext::is_variable_used):
	Check if the set contains the hir id linked to a variable.
	(UnusedVarContext::as_string): Refactor method for new set.
	* checks/lints/unused-var/rust-unused-var-context.h: Refactor methods.
	* lang.opt: Change description for unused check flag.

Signed-off-by: Lucas Ly Ba <[email protected]>

Author: lucasly-ba

gcc/rust/checks/lints/unused/rust-unused-collector.cc

@@ -28,7 +28,7 @@ namespace Rust {
 namespace Analysis {
 UnusedCollector::UnusedCollector (UnusedContext &context)
   : nr_context (
-    Resolver2_0::ImmutableNameResolutionContext::get ().resolver ()),
+      Resolver2_0::ImmutableNameResolutionContext::get ().resolver ()),
     mappings (Analysis::Mappings::get ()), unused_context (context)
 {}
 void

gcc/rust/checks/lints/unused/rust-unused-context.cc

@@ -1,4 +1,4 @@
-// Copyright (C) 2025 Free Software Foundation, Inc.
+// Copyright (C) 2025 Free Software Foundation, Inc.D
 
 // This file is part of GCC.