Simplify is_camel_case to use map_windows

Author: sjwang05

compiler/rustc_lint/src/lib.rs

@@ -34,6 +34,7 @@
 #![feature(control_flow_enum)]
 #![feature(if_let_guard)]
 #![feature(iter_intersperse)]
+#![feature(iter_map_windows)]
 #![feature(iter_order_by)]
 #![feature(let_chains)]
 #![feature(min_specialization)]

compiler/rustc_lint/src/nonstandard_style.rs

@@ -89,15 +89,21 @@ fn is_camel_case(name: &str) -> bool {
     // ones (some scripts don't have a concept of upper/lowercase)
     !name.chars().next().unwrap().is_lowercase()
         && !name.contains("__")
-        && !name.chars().collect::<Vec<_>>().array_windows().any(|&[fst, snd]| {
-            // 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())
+            .map_windows(|&[fst, snd]| (fst, snd))
+            .any(|(fst, snd)| {
+                // contains a capitalisable character followed by, or preceded by, an underscore
+                char_has_case(fst) && snd == '_' || char_has_case(snd) && fst == '_'
+            })
+        && !name
+            .chars()
+            .map_windows(|&[fst, snd, thd]| (fst, snd, thd))
+            .any(|(fst, snd, thd)| {
+                // three capitalized characters in a row
+                char_has_case(fst) && char_has_case(snd) && char_has_case(thd)
+                    && fst.is_uppercase() && snd.is_uppercase() && thd.is_uppercase()
+            })
 }
 
 fn to_camel_case(s: &str) -> String {

compiler/rustc_lint/src/nonstandard_style/tests.rs

@@ -23,4 +23,6 @@ fn camel_case() {
     assert_eq!(to_camel_case("ONE"), "One");
 
     assert!(is_camel_case("AStr"));
+
+    assert!(is_camel_case("Foo"));
 }