`_0` is not numbered parameter
#### Before this patch:
```console
$ bin/mruby rb -e '_0=:l; p ->{_0}.()'
-e:1:13: _0 is not available
-e:1:13: syntax error, unexpected $end, expecting '}'
```
#### After this patch (same as Ruby):
```console
$ bin/mruby rb -e '_0=:l; p ->{_0}.()'
:l
```
MODIFY
mrbgems/mruby-compiler/core/parse.y
mrbgems/mruby-compiler/core/parse.y
@@ -74,8 +74,6 @@ typedef unsigned int stack_type;
#define NUM_SUFFIX_R (1<<0)
#define NUM_SUFFIX_I (1<<1)
-#define NUMPARAM_MAX 9
-
static inline mrb_sym
intern_cstr_gen(parser_state *p, const char *s)
{
@@ -5954,6 +5952,8 @@ parser_yylex(parser_state *p)
case '_':
if (toklen(p) == 2 && ISDIGIT(tok(p)[1]) && p->nvars) {
int n = tok(p)[1] - '0';
+
+ if (n > 0) {
node *nvars = p->nvars->car;
while (nvars) {
@@ -5967,18 +5967,11 @@ parser_yylex(parser_state *p)
if (intn(p->nvars->cdr) < 0) {
yywarning(p, "numbered parameter in nested block");
}
- if (n == 0) {
- yyerror(p, "_0 is not available");
- return 0;
- }
- if (n > NUMPARAM_MAX) {
- yyerror(p, "too large numbered parameter");
- return 0;
- }
pylval.num = n;
p->lstate = EXPR_END;
return tNUMPARAM;
}
+ }
/* fall through */
default:
if (toklast(p) == '!' || toklast(p) == '?') {

MODIFY
test/t/syntax.rb
test/t/syntax.rb
@@ -672,7 +672,6 @@ assert 'keyword arguments' do
assert_equal([:a, nil, :c], m(a: :a, c: :c))
end
-
assert('numbered parameters') do
assert_equal(15, [1,2,3,4,5].reduce {_1+_2})
assert_equal(3, ->{_1+_2}.call(1,2))
@@ -680,3 +679,8 @@ assert('numbered parameters') do
assert_equal(5, -> a: ->{_1} {a}.call.call(5))
assert_equal(45, Proc.new do _1 + _2 + _3 + _4 + _5 + _6 + _7 + _8 + _9 end.call(*[1, 2, 3, 4, 5, 6, 7, 8, 9]))
end
+
+assert('_0 is not numbered parameter') do
+ _0 = :l
+ assert_equal(:l, ->{_0}.call)
+end

`_0` is not numbered parameter

#### Before this patch:

  ```console
  $ bin/mruby rb -e '_0=:l; p ->{_0}.()'
  -e:1:13: _0 is not available
  -e:1:13: syntax error, unexpected $end, expecting '}'
  ```

#### After this patch (same as Ruby):

  ```console
  $ bin/mruby rb -e '_0=:l; p ->{_0}.()'
  :l
  ```