Full Grammar specification lists invalid syntax

[encukou]

The Full Grammar specification lists these production rules:

 type_param:  
     | NAME [type_param_bound]
     | '*' NAME ':' expression
     | '*' NAME 
     | '**' NAME ':' expression 
     | '**' NAME 
 
 for_if_clause:
     | 'async' 'for' star_targets 'in' ~ disjunction ('if' disjunction )* 
     | 'for' star_targets 'in' ~ disjunction ('if' disjunction )* 
     | 'async'? 'for' (bitwise_or (',' bitwise_or)* [',']) !'in' 

 starred_expression:
     | '*' expression 
     | '*' 

However, some of the alternatives are actually invalid syntax: in the grammar file we can find that they're handled by raising a syntax error. For example:

for_if_clause[comprehension_ty]:
    [...]
    | 'async'? 'for' (bitwise_or (',' bitwise_or)* [',']) !'in' {
        RAISE_SYNTAX_ERROR("'in' expected after for-loop variables") }

These should be hidden in the same way as other invalid rules.

Linked PRs

• gh-118235: Skip RAISE_SYNTAX_ERROR rules in the grammar spec #118237
• [3.12] gh-118235: Skip RAISE_SYNTAX_ERROR rules in the grammar spec (GH-118237) #118309
• gh-118235: Move RAISE_SYNTAX_ERROR actions to invalid rules and make sure they stay there #119731

[encukou]

@pablogsal said on #118237 (comment):

Another alternative it's to move all these rules to be inside an invalid_ rule and in general prevent by review or automation rules that have RAISE_SYNTAX_ERROR in the actions.

I tried to do this, but I got stuck moving the type_param syntax errors to invalid rules.
The SyntaxError from the forced token &&'(' from function_def_raw is the one that gets reported.

Whenever you have time, could you look at main...encukou:cpython:invalid-grammar and give me a hint at what I'm doing wrong?

That PR fails with:

FAIL: test_typevartuple_01 (test.test_type_params.TypeParamsTypeVarTupleTest.test_typevartuple_01)
----------------------------------------------------------------------
  File "<test string>", line 1
    def func1[*A: str](): pass
             ^
SyntaxError: expected '('

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  ...
AssertionError: "cannot use bound with TypeVarTuple" does not match "expected '(' (<test string>, line 1)"

(No rush at all.)

[encukou]

I just found the discussion about that issue in #118091; I'll read it when I get back to grammar-in-docs.