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

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) -> Option<Vec<TokenKind>> {
-        match *self {
-            Comma => Some(vec![Dot, Lt, Semi]),
-            Semi => Some(vec![Colon, Comma]),
-            Colon => Some(vec![Semi]),
-            FatArrow => Some(vec![Eq, RArrow, Ge, Gt]),
-            _ => None,
+    pub fn similar_tokens(&self) -> &[TokenKind] {
+        match self {
+            Comma => &[Dot, Lt, Semi],
+            Semi => &[Colon, Comma],
+            Colon => &[Semi],
+            FatArrow => &[Eq, RArrow, Ge, Gt],
+            _ => &[],
         }
     }
 

compiler/rustc_builtin_macros/src/format.rs

@@ -101,15 +101,14 @@ fn parse_args<'a>(ecx: &ExtCtxt<'a>, sp: Span, tts: TokenStream) -> PResult<'a,
 
             match p.expect(exp!(Comma)) {
                 Err(err) => {
-                    match token::TokenKind::Comma.similar_tokens() {
-                        Some(tks) if tks.contains(&p.token.kind) => {
-                            // If a similar token is found, then it may be a typo. We
-                            // consider it as a comma, and continue parsing.
-                            err.emit();
-                            p.bump();
-                        }
+                    if token::TokenKind::Comma.similar_tokens().contains(&p.token.kind) {
+                        // If a similar token is found, then it may be a typo. We
+                        // consider it as a comma, and continue parsing.
+                        err.emit();
+                        p.bump();
+                    } else {
                         // Otherwise stop the parsing and return the error.
-                        _ => return Err(err),
+                        return Err(err);
                     }
                 }
                 Ok(Recovered::Yes(_)) => (),

compiler/rustc_parse/src/parser/expr.rs

@@ -3114,9 +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()
-                .is_some_and(|similar_tokens| 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)

compiler/rustc_parse/src/parser/mod.rs

@@ -923,10 +923,8 @@ impl<'a> Parser<'a> {
 
                                 _ => {
                                     // Attempt to keep parsing if it was a similar separator.
-                                    if let Some(tokens) = exp.tok.similar_tokens() {
-                                        if tokens.contains(&self.token.kind) {
-                                            self.bump();
-                                        }
+                                    if exp.tok.similar_tokens().contains(&self.token.kind) {
+                                        self.bump();
                                     }
                                 }
                             }