gccrs: add non upper case globals lint

gcc/rust/ChangeLog:

	* checks/lints/unused/rust-unused-checker.cc (UnusedChecker::visit):
	Add warning for static variables.

gcc/testsuite/ChangeLog:

	* rust/compile/non-upper-case-globals_0.rs: New test.

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

Author: lucasly-ba

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

@@ -59,6 +59,13 @@ UnusedChecker::visit (HIR::StaticItem &item)
     rust_warning_at (item.get_locus (), OPT_Wunused_variable,
 		     "unused variable %qs",
 		     item.get_identifier ().as_string ().c_str ());
+
+  if (!std::all_of (var_name.begin (), var_name.end (), [] (unsigned char c) {
+	return ISUPPER (c) || ISDIGIT (c) || c == '_';
+      }))
+    rust_warning_at (item.get_locus (), OPT_Wunused_variable,
+		     "static variable %qs should have an upper case name",
+		     var_name.c_str ());
 }
 
 void

gcc/testsuite/rust/compile/non-upper-case-globals_0.rs

@@ -0,0 +1,4 @@
+// { dg-additional-options "-frust-unused-check-2.0" }
+
+static _my_static : i32 = 0;
+// { dg-warning "static variable ._my_static. should have an upper case name" "" { target *-*-* } .-1 }