introduce bump as a better-checked alternative to bump_any

crates/ra_parser/src/grammar.rs

@@ -126,7 +126,7 @@ pub(crate) mod fragments {
 
         while !p.at(EOF) {
             if p.at(T![;]) {
-                p.bump_any();
+                p.bump(T![;]);
                 continue;
             }
 
@@ -179,7 +179,7 @@ fn opt_visibility(p: &mut Parser) -> bool {
     match p.current() {
         T![pub] => {
             let m = p.start();
-            p.bump_any();
+            p.bump(T![pub]);
             if p.at(T!['(']) {
                 match p.nth(1) {
                     // test crate_visibility

crates/ra_parser/src/parser.rs

@@ -170,6 +170,12 @@ impl<'t> Parser<'t> {
         }
     }
 
+    /// Advances the parser by one token, asserting that it is exactly the expected token
+    pub(crate) fn bump(&mut self, expected: SyntaxKind) {
+        debug_assert!(self.nth(0) == expected);
+        self.bump_any()
+    }
+
     /// Advances the parser by one token, remapping its kind.
     /// This is useful to create contextual keywords from
     /// identifiers. For example, the lexer creates an `union`