Make the naming lints only warn on names with upper/lowercase equivalents

Closes #21735.

src/test/compile-fail/issue-17718-const-naming.rs

@@ -11,7 +11,7 @@
 #[deny(warnings)]
 
 const foo: isize = 3;
-//~^ ERROR: should have an uppercase name such as
+//~^ ERROR: should have an upper case name such as
 //~^^ ERROR: constant item is never used
 
 fn main() {}

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 uppercase name
+        static bad: isize = 1; //~ ERROR static constant `bad` should have an upper case name
     }
 
     mod warn {

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

@@ -11,6 +11,6 @@
 #![forbid(non_upper_case_globals)]
 #![allow(dead_code)]
 
-static foo: isize = 1; //~ ERROR static constant `foo` should have an uppercase name such as `FOO`
+static foo: isize = 1; //~ ERROR static constant `foo` should have an upper case name such as `FOO`
 
 fn main() { }

src/test/compile-fail/match-static-const-lc.rs

@@ -19,7 +19,7 @@ pub const a : isize = 97;
 fn f() {
     let r = match (0,0) {
         (0, a) => 0,
-        //~^ ERROR static constant in pattern `a` should have an uppercase name such as `A`
+        //~^ ERROR constant in pattern `a` should have an upper case name such as `A`
         (x, y) => 1 + x + y,
     };
     assert!(r == 1);
@@ -34,7 +34,7 @@ fn g() {
     use self::m::aha;
     let r = match (0,0) {
         (0, aha) => 0,
-        //~^ ERROR static constant in pattern `aha` should have an uppercase name such as `AHA`
+        //~^ ERROR constant in pattern `aha` should have an upper case name such as `AHA`
         (x, y)   => 1 + x + y,
     };
     assert!(r == 1);
@@ -48,7 +48,7 @@ fn h() {
     use self::n::OKAY as not_okay;
     let r = match (0,0) {
         (0, not_okay) => 0,
-//~^ ERROR static constant in pattern `not_okay` should have an uppercase name such as `NOT_OKAY`
+//~^ ERROR constant in pattern `not_okay` should have an upper case name such as `NOT_OKAY`
         (x, y)   => 1 + x + y,
     };
     assert!(r == 1);

src/test/run-pass/snake-case-no-lowercase-equivalent.rs

@@ -0,0 +1,17 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(non_ascii_idents)]
+#![deny(non_snake_case)]
+
+// This name is neither upper nor lower case
+fn 你好() {}
+
+fn main() {}