gccrs: refactor unused var lint

gcc/rust/ChangeLog:

	* checks/lints/unused-var/rust-unused-var-checker.cc (UnusedVarChecker::visit):
	Change unused name warning to unused variable warning.
	* 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.

gcc/testsuite/ChangeLog:

	* rust/compile/static_item_0.rs: Modify warning output.
	* rust/compile/template_function_0.rs: Modify warning output.

Signed-off-by: Lucas Ly Ba <lucas.ly-ba@outlook.com>

Author: lucasly-ba

gcc/rust/checks/lints/unused-var/rust-unused-var-checker.cc

@@ -21,6 +21,7 @@
 #include "rust-hir-item.h"
 
 #include "options.h"
+#include "rust-keyword-values.h"
 
 namespace Rust {
 namespace Analysis {
@@ -38,25 +39,26 @@ UnusedVarChecker::go (HIR::Crate &crate)
   for (auto &item : crate.get_items ())
     item->accept_vis (*this);
 }
+
 void
 UnusedVarChecker::visit (HIR::ConstantItem &item)
 {
   std::string var_name = item.get_identifier ().as_string ();
-  bool starts_with_under_score = var_name.compare (0, 1, "_") == 0;
   auto id = item.get_mappings ().get_hirid ();
-  if (!unused_var_context.is_variable_used (id) && !starts_with_under_score)
-    rust_warning_at (item.get_locus (), OPT_Wunused_variable, "unused name %qs",
+  if (!unused_context.is_variable_used (id) && var_name[0] != '_')
+    rust_warning_at (item.get_locus (), OPT_Wunused_variable,
+		     "unused variable %qs",
 		     item.get_identifier ().as_string ().c_str ());
 }
 
 void
 UnusedVarChecker::visit (HIR::StaticItem &item)
 {
   std::string var_name = item.get_identifier ().as_string ();
-  bool starts_with_under_score = var_name.compare (0, 1, "_") == 0;
   auto id = item.get_mappings ().get_hirid ();
-  if (!unused_var_context.is_variable_used (id) && !starts_with_under_score)
-    rust_warning_at (item.get_locus (), OPT_Wunused_variable, "unused name %qs",
+  if (!unused_context.is_variable_used (id) && var_name[0] != '_')
+    rust_warning_at (item.get_locus (), OPT_Wunused_variable,
+		     "unused variable %qs",
 		     item.get_identifier ().as_string ().c_str ());
 }
 
@@ -69,12 +71,11 @@ void
 UnusedVarChecker::visit (HIR::IdentifierPattern &pattern)
 {
   std::string var_name = pattern.get_identifier ().as_string ();
-  bool starts_with_under_score = var_name.compare (0, 1, "_") == 0;
   auto id = pattern.get_mappings ().get_hirid ();
-  if (!unused_var_context.is_variable_used (id) && var_name != "self"
-      && !starts_with_under_score)
+  if (!unused_context.is_variable_used (id)
+      && var_name != Values::Keywords::SELF && var_name[0] != '_')
     rust_warning_at (pattern.get_locus (), OPT_Wunused_variable,
-		     "unused name %qs",
+		     "unused variable %qs",
 		     pattern.get_identifier ().as_string ().c_str ());
 }
 void
@@ -85,13 +86,11 @@ UnusedVarChecker::visit (HIR::AssignmentExpr &expr)
   const auto &lhs = expr.get_lhs ();
   auto s = lhs.as_string ();
   std::string var_name = s.substr (0, s.find (':'));
-  bool starts_with_under_score = var_name.compare (0, 1, "_") == 0;
   NodeId ast_node_id = lhs.get_mappings ().get_nodeid ();
   NodeId def_id = nr_context.lookup (ast_node_id).value ();
   HirId id = mappings.lookup_node_to_hir (def_id).value ();
-  if (unused_var_context.is_variable_assigned (id,
-					       lhs.get_mappings ().get_hirid ())
-      && !starts_with_under_score)
+  if (unused_context.is_variable_assigned (id, lhs.get_mappings ().get_hirid ())
+      && var_name[0] != '_')
     rust_warning_at (lhs.get_locus (), OPT_Wunused_variable,
 		     "unused assignment %qs", var_name.c_str ());
 }

gcc/rust/checks/lints/unused-var/rust-unused-var-checker.h

@@ -37,6 +37,7 @@ class UnusedVarChecker : public HIR::DefaultHIRVisitor
   UnusedVarContext unused_var_context;
 
   using HIR::DefaultHIRVisitor::visit;
+
   virtual void visit (HIR::TraitItemFunc &decl) override;
   virtual void visit (HIR::ConstantItem &item) override;
   virtual void visit (HIR::StaticItem &item) override;

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

@@ -39,42 +39,25 @@ UnusedVarCollector::go (HIR::Crate &crate)
     item->accept_vis (*this);
 }
 
-void
-UnusedVarCollector::visit (HIR::ConstantItem &item)
-{
-  unused_var_context.add_variable (item.get_mappings ().get_hirid ());
-  walk (item);
-}
-
-void
-UnusedVarCollector::visit (HIR::StaticItem &item)
-{
-  unused_var_context.add_variable (item.get_mappings ().get_hirid ());
-  walk (item);
-}
-
-void
-UnusedVarCollector::visit (HIR::IdentifierPattern &pattern)
-{
-  unused_var_context.add_variable (pattern.get_mappings ().get_hirid ());
-}
-
 void
 UnusedVarCollector::visit (HIR::PathInExpression &expr)
 {
   mark_path_used (expr);
+  walk (expr);
 }
 
 void
 UnusedVarCollector::visit (HIR::QualifiedPathInExpression &expr)
 {
   mark_path_used (expr);
+  walk (expr);
 }
 
 void
 UnusedVarCollector::visit (HIR::StructExprFieldIdentifier &ident)
 {
   mark_path_used (ident);
+  walk (ident);
 }
 void
 UnusedVarCollector::visit (HIR::AssignmentExpr &expr)

gcc/rust/checks/lints/unused-var/rust-unused-var-collector.h

@@ -42,9 +42,6 @@ class UnusedVarCollector : public HIR::DefaultHIRVisitor
   using HIR::DefaultHIRVisitor::visit;
   virtual void visit (HIR::PathInExpression &expr) override;
   virtual void visit (HIR::StructExprFieldIdentifier &ident) override;
-  virtual void visit (HIR::ConstantItem &item) override;
-  virtual void visit (HIR::StaticItem &item) override;
-  virtual void visit (HIR::IdentifierPattern &pattern) override;
   virtual void visit (HIR::QualifiedPathInExpression &expr) override;
   virtual void visit (HIR::AssignmentExpr &expr) override;
 
@@ -59,7 +56,7 @@ class UnusedVarCollector : public HIR::DefaultHIRVisitor
   template <typename T> void mark_path_used (T &path_expr)
   {
     auto def_id = get_def_id (path_expr);
-    unused_var_context.mark_used (def_id);
+    unused_var_context.add_variable (def_id);
     unused_var_context.remove_assign (def_id);
   }
 };

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

@@ -23,22 +23,15 @@ namespace Analysis {
 
 void
 UnusedVarContext::add_variable (HirId id)
-{
-  if (is_used.find (id) == is_used.end ())
-    is_used.insert ({id, false});
-}
 
-void
-UnusedVarContext::mark_used (HirId id)
 {
-  is_used[id] = true;
+  used_vars.emplace (id);
 }
 
 bool
 UnusedVarContext::is_variable_used (HirId id) const
 {
-  auto it = is_used.find (id);
-  return it != is_used.end () && it->second;
+  return used_vars.find (id) != used_vars.end ();
 }
 
 void
@@ -66,10 +59,9 @@ UnusedVarContext::as_string () const
 {
   std::stringstream ss;
   ss << "UnusedVarContext: ";
-  for (const auto &pair : is_used)
+  for (const auto &v : used_vars)
     {
-      ss << "HirId: " << pair.first << " Used: " << (pair.second ? "Yes" : "No")
-	 << "\n";
+      ss << "HirId: " << v << "\n";
     }
   return ss.str ();
 }

gcc/rust/checks/lints/unused-var/rust-unused-var-context.h

@@ -25,17 +25,15 @@ class UnusedVarContext
 {
 public:
   void add_variable (HirId id);
-  void mark_used (HirId id);
   bool is_variable_used (HirId id) const;
-
   void add_assign (HirId id_def, HirId id);
   void remove_assign (HirId id_def);
   bool is_variable_assigned (HirId id_def, HirId id);
 
   std::string as_string () const;
 
 private:
-  std::map<HirId, bool> is_used;
+  std::unordered_set<HirId> used_vars;
   std::map<HirId, std::vector<HirId>> assigned_vars;
 };
 

gcc/rust/lang.opt

@@ -235,6 +235,6 @@ Define a built-in offset_of macro in the compiler and assume it is present
 
 frust-unused-check-2.0
 Rust Var(flag_unused_check_2_0)
-Use the new unused variable check instead of old one
+Use the new unused variable check implementation.
 
 ; This comment is to ensure we retain the blank line above.

gcc/testsuite/rust/compile/static_item_0.rs

@@ -1,3 +1,3 @@
 // { dg-additional-options "-frust-unused-check-2.0" }
 static TEST: usize = 1;
-// { dg-warning "unused name" "" { target *-*-* } .-1 }
+// { dg-warning "unused variable .TEST." "" { target *-*-* } .-1 }

gcc/testsuite/rust/compile/template_function_0.rs

@@ -1,7 +1,9 @@
 // { dg-additional-options "-frust-unused-check-2.0" }
+#![feature(lang_items)]
+
 #[lang = "sized"]
 pub trait Sized {}
 
 pub fn test<T> (a: usize) -> () {
-    // { dg-warning "unused name" "" { target *-*-* } .-1 }
-}
+    // { dg-warning "unused variable .a." "" { target *-*-* } .-1 }
+}