Fix non_camel_case_types for screaming words

Author: sjwang05

compiler/rustc_lint/src/nonstandard_style.rs

@@ -93,6 +93,9 @@ fn is_camel_case(name: &str) -> bool {
             // contains a capitalisable character followed by, or preceded by, an underscore
             char_has_case(fst) && snd == '_' || char_has_case(snd) && fst == '_'
         })
+        && !name.chars().collect::<Vec<_>>().array_windows().any(|&[fst, snd, thr]| {
+            fst.is_uppercase() && snd.is_uppercase() && thr.is_uppercase()
+        })
 }
 
 fn to_camel_case(s: &str) -> String {

compiler/rustc_lint/src/nonstandard_style/tests.rs

@@ -18,4 +18,9 @@ fn camel_case() {
 
     assert!(!is_camel_case("ONE_TWO_THREE"));
     assert_eq!(to_camel_case("ONE_TWO_THREE"), "OneTwoThree");
+
+    assert!(!is_camel_case("ONE"));
+    assert_eq!(to_camel_case("ONE"), "One");
+
+    assert!(is_camel_case("AStr"));
 }