Specify literal tokens

Author: matklad

xtask/src/codegen/gen_syntax.rs

@@ -590,6 +590,7 @@ fn lower_rule(acc: &mut Vec<Field>, grammar: &Grammar, label: Option<&String>, r
                     | "op"
                     | "index"
                     | "base"
+                    | "value"
             );
             if manually_implemented {
                 return;

xtask/src/codegen/rust.ungram

@@ -239,7 +239,13 @@ Expr =
 | WhileExpr
 
 Literal =
-  Attr* 'int_number'
+  Attr* value:(
+    'int_number' | 'float_number'
+  | 'string' | 'raw_string'
+  | 'byte_string' | 'raw_byte_string'
+  | 'true' | 'false'
+  | 'char' | 'byte'
+  )
 
 PathExpr =
   Attr* Path