Update compiler/rustc_lexer/src/lib.rs

Co-authored-by: Vadim Petrochenkov <[email protected]>

Author: richard-uk1

compiler/rustc_lexer/src/lib.rs

@@ -695,7 +695,7 @@ impl Cursor<'_> {
                             }
                         }
                         ('e' | 'E', '0'..='9' | '+' | '-') => {
-                            // definitely an exponent
+                            // Definitely an exponent (which still can be empty).
                             self.bump();
                             empty_exponent = !self.eat_float_exponent();
                             suffix_start = self.pos_within_token();