Lint against lowercase static mut

src/librustc_lint/bad_style.rs

@@ -355,10 +355,12 @@ impl LintPass for NonUpperCaseGlobals {
 impl LateLintPass for NonUpperCaseGlobals {
     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
         match it.node {
-            // only check static constants
             hir::ItemStatic(_, hir::MutImmutable, _) => {
                 NonUpperCaseGlobals::check_upper_case(cx, "static constant", it.name, it.span);
             }
+            hir::ItemStatic(_, hir::MutMutable, _) => {
+                NonUpperCaseGlobals::check_upper_case(cx, "static variable", it.name, it.span);
+            }
             hir::ItemConst(..) => {
                 NonUpperCaseGlobals::check_upper_case(cx, "constant", it.name, it.span);
             }

src/test/compile-fail/lint-non-uppercase-statics.rs

@@ -13,4 +13,7 @@
 
 static foo: isize = 1; //~ ERROR static constant `foo` should have an upper case name such as `FOO`
 
+static mut bar: isize = 1;
+        //~^ ERROR static variable `bar` should have an upper case name such as `BAR`
+
 fn main() { }