Consider specialized syntax error for `&&` and `||`

[brianschubert]

Feature or enhancement

Proposal:

Coming from other languages, it’s easy to accidentally write && or || in place of and or or. I've even seen experienced people reach for them when doing boolean operations on Numpy arrays and the like.

It could be helpful to add a specialized syntax error. Something like:

  File "<python-input-1>", line 1
    a && b
      ^^
SyntaxError: invalid syntax. Maybe you meant 'and' or '&' instead of '&&'?

This might be a little tricky, since && and || are not their own tokens, so I don't think this can be done at the grammar level.

cc @pablogsal @lysnikolaou

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

[Aniketsy]

@brianschubert yes, i think we should improve error message, with your permission i can create PR for this , Thanks!

[picnixz]

@Aniketsy I would prefer that a parser expert takes care of that. This is likely a non-trivial change so to make it easier to review, it would be better if a core dev or someone familiar with the parser takes care of this.

[skirpichev]

How about following patch:

diff --git a/Parser/pegen_errors.c b/Parser/pegen_errors.c
index 312699415ef..beaf8463628 100644
--- a/Parser/pegen_errors.c
+++ b/Parser/pegen_errors.c
@@ -442,6 +442,11 @@ _Pypegen_set_syntax_error(Parser* p, Token* last_token) {
         RAISE_INDENTATION_ERROR(last_token->type == INDENT ? "unexpected indent" : "unexpected unindent");
         return;
     }
+    if (last_token->type == AMPER && p->tokens[p->fill - 2]->type == AMPER) {
+        RAISE_SYNTAX_ERROR_KNOWN_RANGE(p->tokens[p->fill - 2], last_token,
+                                       "invalid syntax.  Maybe you meant 'and' or '&' instead of '&&'");
+        return;
+    }
     // Unknown error (generic case)
 
     // Use the last token we found on the first pass to avoid reporting

?

>>> 1 && 2
  File "<python-input-0>", line 1
    1 && 2
      ^^
SyntaxError: invalid syntax.  Maybe you meant 'and' or '&' instead of '&&'