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gh-134036: Improve error messages for invalid raise statements #134077

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Merged
merged 1 commit into from
Jun 6, 2025
Merged

gh-134036: Improve error messages for invalid raise statements #134077

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6 changes: 6 additions & 0 deletions Grammar/python.gram
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Original file line number Diff line number Diff line change
Expand Up @@ -184,6 +184,7 @@ return_stmt[stmt_ty]:
| 'return' a=[star_expressions] { _PyAST_Return(a, EXTRA) }

raise_stmt[stmt_ty]:
| invalid_raise_stmt
| 'raise' a=expression b=['from' z=expression { z }] { _PyAST_Raise(a, b, EXTRA) }
| 'raise' { _PyAST_Raise(NULL, NULL, EXTRA) }

Expand Down Expand Up @@ -1287,6 +1288,11 @@ invalid_ann_assign_target[expr_ty]:
| list
| tuple
| '(' a=invalid_ann_assign_target ')' { a }
invalid_raise_stmt:
| a='raise' b='from' {
RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "did you forget an expression between 'raise' and 'from'?") }
| 'raise' expression a='from' {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "did you forget an expression after 'from'?") }
invalid_del_stmt:
| 'del' a=star_expressions {
RAISE_SYNTAX_ERROR_INVALID_TARGET(DEL_TARGETS, a) }
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22 changes: 22 additions & 0 deletions Lib/test/test_syntax.py
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Expand Up @@ -1678,6 +1678,28 @@
...
SyntaxError: invalid syntax

Better errors for `raise` statement:

>>> raise ValueError from
Traceback (most recent call last):
SyntaxError: did you forget an expression after 'from'?

>>> raise mod.ValueError() from
Traceback (most recent call last):
SyntaxError: did you forget an expression after 'from'?

>>> raise from exc
Traceback (most recent call last):
SyntaxError: did you forget an expression between 'raise' and 'from'?

>>> raise from None
Traceback (most recent call last):
SyntaxError: did you forget an expression between 'raise' and 'from'?

>>> raise from
Traceback (most recent call last):
SyntaxError: did you forget an expression between 'raise' and 'from'?

Check that an multiple exception types with missing parentheses
raise a custom exception only when using 'as'

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-05-16-09-06-38.gh-issue-134036.st2e-B.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Improve :exc:`SyntaxError` message when using invalid :keyword:`raise`
statements.
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