Use one message for uppercase global lint

Author: matklad

src/librustc_lint/bad_style.rs

@@ -355,10 +355,7 @@ impl LintPass for NonUpperCaseGlobals {
 impl LateLintPass for NonUpperCaseGlobals {
     fn check_item(&mut self, cx: &LateContext, it: &hir::Item) {
         match it.node {
-            hir::ItemStatic(_, hir::MutImmutable, _) => {
-                NonUpperCaseGlobals::check_upper_case(cx, "static constant", it.name, it.span);
-            }
-            hir::ItemStatic(_, hir::MutMutable, _) => {
+            hir::ItemStatic(..) => {
                 NonUpperCaseGlobals::check_upper_case(cx, "static variable", it.name, it.span);
             }
             hir::ItemConst(..) => {

src/test/compile-fail/lint-group-style.rs

@@ -24,7 +24,7 @@ mod test {
     mod bad {
         fn CamelCase() {} //~ ERROR function `CamelCase` should have a snake case name
 
-        static bad: isize = 1; //~ ERROR static constant `bad` should have an upper case name
+        static bad: isize = 1; //~ ERROR static variable `bad` should have an upper case name
     }
 
     mod warn {

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

@@ -11,7 +11,7 @@
 #![forbid(non_upper_case_globals)]
 #![allow(dead_code)]
 
-static foo: isize = 1; //~ ERROR static constant `foo` should have an upper case name such as `FOO`
+static foo: isize = 1; //~ ERROR static variable `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`