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bpo-45834: Move runtime 'except:' check to the parser #29625

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bpo-45834: Move runtime 'except:' check to the parser #29625

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13 changes: 11 additions & 2 deletions Grammar/python.gram
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Original file line number Diff line number Diff line change
Expand Up @@ -402,7 +402,12 @@ with_item[withitem_ty]:
try_stmt[stmt_ty]:
| invalid_try_stmt
| 'try' &&':' b=block f=finally_block { _PyAST_Try(b, NULL, NULL, f, EXTRA) }
| 'try' &&':' b=block ex[asdl_excepthandler_seq*]=except_block+ el=[else_block] f=[finally_block] { _PyAST_Try(b, ex, el, f, EXTRA) }
| 'try' &&':' b=block ex[asdl_excepthandler_seq*]=except_block+ d_ex[asdl_match_case_seq*]=[default_except_block] el=[else_block] f=[finally_block] {
_PyAST_Try(b, (d_ex) ? (asdl_excepthandler_seq*)_PyPegen_seq_append_to_end(p, (asdl_seq*)ex, d_ex) : ex, el, f, EXTRA)
}
| 'try' &&':' b=block d_ex[asdl_match_case_seq*]=default_except_block el=[else_block] f=[finally_block] {
_PyAST_Try(b, (asdl_excepthandler_seq*)_PyPegen_singleton_seq(p, d_ex), el, f, EXTRA)
}

# Except statement
# ----------------
Expand All @@ -411,8 +416,9 @@ except_block[excepthandler_ty]:
| invalid_except_stmt_indent
| 'except' e=expression t=['as' z=NAME { z }] ':' b=block {
_PyAST_ExceptHandler(e, (t) ? ((expr_ty) t)->v.Name.id : NULL, b, EXTRA) }
| 'except' ':' b=block { _PyAST_ExceptHandler(NULL, NULL, b, EXTRA) }
| invalid_except_stmt
default_except_block[excepthandler_ty]:
| 'except' ':' b=block { _PyAST_ExceptHandler(NULL, NULL, b, EXTRA) }
finally_block[asdl_stmt_seq*]:
| invalid_finally_stmt
| 'finally' &&':' a=block { a }
Expand Down Expand Up @@ -1187,6 +1193,9 @@ invalid_try_stmt:
| a='try' ':' NEWLINE !INDENT {
RAISE_INDENTATION_ERROR("expected an indented block after 'try' statement on line %d", a->lineno) }
| 'try' ':' block !('except' | 'finally') { RAISE_SYNTAX_ERROR("expected 'except' or 'finally' block") }
| 'try' ':' block except_block* a=default_except_block (except_block|default_except_block)+ {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "default 'except:' must be last") }

invalid_except_stmt:
| 'except' a=expression ',' expressions ['as' NAME ] ':' {
RAISE_SYNTAX_ERROR_STARTING_FROM(a, "multiple exception types must be parenthesized") }
Expand Down
43 changes: 43 additions & 0 deletions Lib/test/test_syntax.py
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Expand Up @@ -1039,6 +1039,49 @@
Traceback (most recent call last):
IndentationError: expected an indented block after 'finally' statement on line 5

>>> try:
... something()
... except:
... pass
... except A:
... pass
... else:
... pass
... finally:
... pass
Traceback (most recent call last):
SyntaxError: default 'except:' must be last

>>> try:
... something()
... except:
... pass
... except:
... pass
... else:
... pass
... finally:
... pass
Traceback (most recent call last):
SyntaxError: default 'except:' must be last

>>> try:
... something()
... except A:
... pass
... except B:
... pass
... except:
... pass
... except C:
... pass
... else:
... pass
... finally:
... pass
Traceback (most recent call last):
SyntaxError: default 'except:' must be last

>>> with A:
... pass
Traceback (most recent call last):
Expand Down
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