simplify similar_tokens from Vec<_> to &[_]

Author: hkBst

Diff for: compiler/rustc_ast/src/token.rs

@@ -527,13 +527,13 @@ impl TokenKind {
 
     /// Returns tokens that are likely to be typed accidentally instead of the current token.
     /// Enables better error recovery when the wrong token is found.
-    pub fn similar_tokens(&self) -> Vec<TokenKind> {
+    pub fn similar_tokens(&self) -> &[TokenKind] {
         match self {
-            Comma => vec![Dot, Lt, Semi],
-            Semi => vec![Colon, Comma],
-            Colon => vec![Semi],
-            FatArrow => vec![Eq, RArrow, Ge, Gt],
-            _ => vec![],
+            Comma => &[Dot, Lt, Semi],
+            Semi => &[Colon, Comma],
+            Colon => &[Semi],
+            FatArrow => &[Eq, RArrow, Ge, Gt],
+            _ => &[],
         }
     }
 

Diff for: compiler/rustc_parse/src/parser/expr.rs

@@ -3114,8 +3114,8 @@ impl<'a> Parser<'a> {
             let span_before_body = this.prev_token.span;
             let arm_body;
             let is_fat_arrow = this.check(exp!(FatArrow));
-            let is_almost_fat_arrow = TokenKind::FatArrow
-                .similar_tokens().contains(&this.token.kind);
+            let is_almost_fat_arrow =
+                TokenKind::FatArrow.similar_tokens().contains(&this.token.kind);
 
             // this avoids the compiler saying that a `,` or `}` was expected even though
             // the pattern isn't a never pattern (and thus an arm body is required)