Raise syntax error for unparenthesized generator expr in multi-argument call #12445
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Summary
This PR fixes a bug to raise a syntax error when an unparenthesized generator expression is used as an argument to a call when there are more than one argument.
For reference, the grammar is:
The
genexp
requires the parenthesis as mentioned in the grammar. So, the grammar for a call expression is either a name followed by a generator expression or a name followed by a list of argument. In the former case, the parenthesis are excluded because the generator expression provides them while in the later case, the parenthesis are explicitly provided for a list of arguments which means that the generator expression requires it's own parenthesis.This was discovered in #12420.
Test Plan
Add test cases for valid and invalid syntax.
Make sure that the parser from CPython also raises this at the parsing step: