perf(library/init/lean/parser): minor performance tweaks

library/init/lean/parser/basic.lean

@@ -60,6 +60,7 @@ state_t parser_state $ parsec_t syntax $ state_t parser_cache $ m
 
 @[derive monad alternative monad_reader monad_state monad_parsec monad_except]
 def parser_t (ρ : Type) (m : Type → Type) [monad m] := reader_t ρ $ parser_core_t m
+@[derive monad alternative monad_reader monad_state monad_parsec monad_except]
 abbreviation basic_parser_m := parser_t parser_config id
 abbreviation basic_parser := basic_parser_m syntax
 abbreviation monad_basic_parser := has_monad_lift_t basic_parser_m

library/init/lean/parser/token.lean

@@ -186,11 +186,11 @@ def symbol (sym : string) (lbp := 0) : parser :=
 let sym := sym.trim in
 lift $ try $ do {
   it ← left_over,
-  stx@(syntax.atom ⟨_, sym'⟩) ← token | error "" (dlist.singleton (repr sym)) it,
+  stx@(syntax.atom ⟨_, sym'⟩) ← token | error "" (dlist.singleton sym) it,
   when (sym ≠ sym') $
-    error ("token " ++ repr sym') (dlist.singleton (repr sym)) it,
+    error ("token " ++ sym') (dlist.singleton sym) it,
   pure stx
-} <?> repr sym
+} <?> sym
 
 instance symbol.tokens (sym lbp) : parser.has_tokens (symbol sym lbp : parser) :=
 ⟨[⟨sym.trim, lbp, none⟩]⟩