Merged revisions 72924 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk ........ r72924 | georg.brandl | 2009-05-25 23:02:56 +0200 (Mo, 25 Mai 2009) | 6 lines Allow multiple context managers in one with statement, as proposed in http://codereview.appspot.com/53094 and accepted by Guido. The construct is transformed into multiple With AST nodes so that there should be no problems with the semantics. ........
This commit is contained in:
Georg Brandl
parent
0c1829b919
commit
0c31562a91
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@ -347,9 +347,10 @@ This allows common :keyword:`try`...\ :keyword:`except`...\ :keyword:`finally`
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usage patterns to be encapsulated for convenient reuse.
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.. productionlist::
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with_stmt: "with" `expression` ["as" `target`] ":" `suite`
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with_stmt: "with" with_item ("," with_item)* ":" `suite`
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with_item: `expression` ["as" `target`]
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The execution of the :keyword:`with` statement proceeds as follows:
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The execution of the :keyword:`with` statement with one "item" proceeds as follows:
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#. The context expression is evaluated to obtain a context manager.
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@ -382,6 +383,21 @@ The execution of the :keyword:`with` statement proceeds as follows:
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value from :meth:`__exit__` is ignored, and execution proceeds at the normal
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location for the kind of exit that was taken.
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With more than one item, the context managers are processed as if multiple
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:keyword:`with` statements were nested::
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with A() as a, B() as b:
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suite
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is equivalent to ::
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with A() as a:
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with B() as b:
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suite
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.. versionchanged:: 3.1
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Support for multiple context expressions.
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.. seealso::
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:pep:`0343` - The "with" statement
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@ -73,8 +73,8 @@ try_stmt: ('try' ':' suite
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['else' ':' suite]
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['finally' ':' suite] |
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'finally' ':' suite))
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with_stmt: 'with' test [ with_var ] ':' suite
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with_var: 'as' expr
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with_stmt: 'with' with_item (',' with_item)* ':' suite
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with_item: test ['as' expr]
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# NB compile.c makes sure that the default except clause is last
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except_clause: 'except' [test ['as' NAME]]
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suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT
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@ -42,7 +42,7 @@
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#define for_stmt 295
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#define try_stmt 296
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#define with_stmt 297
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#define with_var 298
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#define with_item 298
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#define except_clause 299
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#define suite 300
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#define test 301
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@ -193,6 +193,7 @@ class RoundtripLegalSyntaxTestCase(unittest.TestCase):
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def test_with(self):
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self.check_suite("with open('x'): pass\n")
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self.check_suite("with open('x') as f: pass\n")
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self.check_suite("with open('x') as f, open('y') as g: pass\n")
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def test_try_stmt(self):
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self.check_suite("try: pass\nexcept: pass\n")
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@ -656,12 +656,88 @@ class ExitSwallowsExceptionTestCase(unittest.TestCase):
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self.fail("ZeroDivisionError should have been raised")
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class NestedWith(unittest.TestCase):
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class Dummy(object):
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def __init__(self, value=None, gobble=False):
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if value is None:
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value = self
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self.value = value
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self.gobble = gobble
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self.enter_called = False
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self.exit_called = False
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def __enter__(self):
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self.enter_called = True
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return self.value
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def __exit__(self, *exc_info):
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self.exit_called = True
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self.exc_info = exc_info
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if self.gobble:
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return True
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class CtorRaises(object):
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def __init__(self): raise RuntimeError()
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class EnterRaises(object):
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def __enter__(self): raise RuntimeError()
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def __exit__(self, *exc_info): pass
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class ExitRaises(object):
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def __enter__(self): pass
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def __exit__(self, *exc_info): raise RuntimeError()
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def testNoExceptions(self):
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with self.Dummy() as a, self.Dummy() as b:
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self.assertTrue(a.enter_called)
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self.assertTrue(b.enter_called)
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self.assertTrue(a.exit_called)
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self.assertTrue(b.exit_called)
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def testExceptionInExprList(self):
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try:
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with self.Dummy() as a, self.CtorRaises():
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pass
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except:
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pass
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self.assertTrue(a.enter_called)
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self.assertTrue(a.exit_called)
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def testExceptionInEnter(self):
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try:
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with self.Dummy() as a, self.EnterRaises():
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self.fail('body of bad with executed')
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except RuntimeError:
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pass
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else:
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self.fail('RuntimeError not reraised')
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self.assertTrue(a.enter_called)
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self.assertTrue(a.exit_called)
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def testExceptionInExit(self):
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body_executed = False
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with self.Dummy(gobble=True) as a, self.ExitRaises():
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body_executed = True
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self.assertTrue(a.enter_called)
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self.assertTrue(a.exit_called)
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self.assertNotEqual(a.exc_info[0], None)
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def testEnterReturnsTuple(self):
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with self.Dummy(value=(1,2)) as (a1, a2), \
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self.Dummy(value=(10, 20)) as (b1, b2):
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self.assertEquals(1, a1)
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self.assertEquals(2, a2)
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self.assertEquals(10, b1)
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self.assertEquals(20, b2)
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def test_main():
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run_unittest(FailureTestCase, NonexceptionalTestCase,
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NestedNonexceptionalTestCase, ExceptionalTestCase,
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NonLocalFlowControlTestCase,
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AssignmentTargetTestCase,
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ExitSwallowsExceptionTestCase)
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ExitSwallowsExceptionTestCase,
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NestedWith)
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if __name__ == '__main__':
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@ -15,6 +15,8 @@ Core and Builtins
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- Issue #6089: Fixed str.format with certain invalid field specifiers
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that would raise SystemError.
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- Added support for multiple context managers in the same with statement.
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- Issue #5829: complex("1e500") no longer raises OverflowError. This
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makes it consistent with float("1e500") and interpretation of real
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and imaginary literals.
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@ -2446,36 +2446,39 @@ validate_decorators(node *tree)
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return ok;
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}
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/* with_var
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with_var: 'as' expr
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/* with_item:
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* test ['as' expr]
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*/
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static int
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validate_with_var(node *tree)
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validate_with_item(node *tree)
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{
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int nch = NCH(tree);
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int ok = (validate_ntype(tree, with_var)
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&& (nch == 2)
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&& validate_name(CHILD(tree, 0), "as")
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&& validate_expr(CHILD(tree, 1)));
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return ok;
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int ok = (validate_ntype(tree, with_item)
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&& (nch == 1 || nch == 3)
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&& validate_test(CHILD(tree, 0)));
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if (ok && nch == 3)
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ok = (validate_name(CHILD(tree, 1), "as")
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&& validate_expr(CHILD(tree, 2)));
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return ok;
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}
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/* with_stmt
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* 0 1 2 -2 -1
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with_stmt: 'with' test [ with_var ] ':' suite
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/* with_stmt:
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* 0 1 ... -2 -1
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* 'with' with_item (',' with_item)* ':' suite
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*/
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static int
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validate_with_stmt(node *tree)
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{
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int i;
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int nch = NCH(tree);
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int ok = (validate_ntype(tree, with_stmt)
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&& ((nch == 4) || (nch == 5))
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&& (nch % 2 == 0)
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&& validate_name(CHILD(tree, 0), "with")
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&& validate_test(CHILD(tree, 1))
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&& (nch == 4 || validate_with_var(CHILD(tree, 2)))
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&& validate_colon(RCHILD(tree, -2))
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&& validate_suite(RCHILD(tree, -1)));
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return ok;
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for (i = 1; ok && i < nch - 2; i += 2)
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ok = validate_with_item(CHILD(tree, i));
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return ok;
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}
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/* funcdef:
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63
Python/ast.c
63
Python/ast.c
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@ -2959,25 +2959,16 @@ ast_for_try_stmt(struct compiling *c, const node *n)
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return TryFinally(body, finally, LINENO(n), n->n_col_offset, c->c_arena);
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}
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static expr_ty
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ast_for_with_var(struct compiling *c, const node *n)
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{
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REQ(n, with_var);
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return ast_for_expr(c, CHILD(n, 1));
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}
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/* with_stmt: 'with' test [ with_var ] ':' suite */
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/* with_item: test ['as' expr] */
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static stmt_ty
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ast_for_with_stmt(struct compiling *c, const node *n)
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ast_for_with_item(struct compiling *c, const node *n, asdl_seq *content)
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{
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expr_ty context_expr, optional_vars = NULL;
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int suite_index = 3; /* skip 'with', test, and ':' */
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asdl_seq *suite_seq;
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assert(TYPE(n) == with_stmt);
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context_expr = ast_for_expr(c, CHILD(n, 1));
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if (TYPE(CHILD(n, 2)) == with_var) {
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optional_vars = ast_for_with_var(c, CHILD(n, 2));
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REQ(n, with_item);
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context_expr = ast_for_expr(c, CHILD(n, 0));
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if (NCH(n) == 3) {
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optional_vars = ast_for_expr(c, CHILD(n, 2));
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if (!optional_vars) {
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return NULL;
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@ -2985,17 +2976,47 @@ ast_for_with_stmt(struct compiling *c, const node *n)
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if (!set_context(c, optional_vars, Store, n)) {
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return NULL;
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}
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suite_index = 4;
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}
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suite_seq = ast_for_suite(c, CHILD(n, suite_index));
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if (!suite_seq) {
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return NULL;
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}
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return With(context_expr, optional_vars, suite_seq, LINENO(n),
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return With(context_expr, optional_vars, content, LINENO(n),
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n->n_col_offset, c->c_arena);
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}
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/* with_stmt: 'with' with_item (',' with_item)* ':' suite */
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static stmt_ty
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ast_for_with_stmt(struct compiling *c, const node *n)
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{
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int i;
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stmt_ty ret;
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asdl_seq *inner;
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REQ(n, with_stmt);
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/* process the with items inside-out */
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i = NCH(n) - 1;
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/* the suite of the innermost with item is the suite of the with stmt */
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inner = ast_for_suite(c, CHILD(n, i));
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if (!inner)
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return NULL;
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for (;;) {
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i -= 2;
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ret = ast_for_with_item(c, CHILD(n, i), inner);
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if (!ret)
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return NULL;
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/* was this the last item? */
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if (i == 1)
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break;
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/* if not, wrap the result so far in a new sequence */
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inner = asdl_seq_new(1, c->c_arena);
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if (!inner)
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return NULL;
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asdl_seq_SET(inner, 0, ret);
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}
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return ret;
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}
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static stmt_ty
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ast_for_classdef(struct compiling *c, const node *n, asdl_seq *decorator_seq)
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{
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@ -911,42 +911,43 @@ static arc arcs_41_0[1] = {
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{99, 1},
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};
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static arc arcs_41_1[1] = {
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{24, 2},
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{100, 2},
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};
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static arc arcs_41_2[2] = {
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{100, 3},
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{25, 4},
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{30, 1},
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{25, 3},
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};
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static arc arcs_41_3[1] = {
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{25, 4},
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{26, 4},
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};
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static arc arcs_41_4[1] = {
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{26, 5},
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{0, 4},
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};
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static arc arcs_41_5[1] = {
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{0, 5},
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};
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static state states_41[6] = {
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static state states_41[5] = {
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{1, arcs_41_0},
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{1, arcs_41_1},
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{2, arcs_41_2},
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{1, arcs_41_3},
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{1, arcs_41_4},
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{1, arcs_41_5},
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};
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static arc arcs_42_0[1] = {
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{80, 1},
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{24, 1},
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};
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static arc arcs_42_1[1] = {
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{101, 2},
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static arc arcs_42_1[2] = {
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{80, 2},
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{0, 1},
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};
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static arc arcs_42_2[1] = {
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{0, 2},
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{101, 3},
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};
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static state states_42[3] = {
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static arc arcs_42_3[1] = {
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{0, 3},
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};
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static state states_42[4] = {
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{1, arcs_42_0},
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{1, arcs_42_1},
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{2, arcs_42_1},
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{1, arcs_42_2},
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{1, arcs_42_3},
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};
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static arc arcs_43_0[1] = {
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{102, 1},
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@ -1810,10 +1811,10 @@ static dfa dfas[81] = {
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"\000\000\000\000\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\000"},
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{296, "try_stmt", 0, 13, states_40,
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"\000\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000"},
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{297, "with_stmt", 0, 6, states_41,
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{297, "with_stmt", 0, 5, states_41,
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"\000\000\000\000\000\000\000\000\000\000\000\000\010\000\000\000\000\000\000\000\000"},
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{298, "with_var", 0, 3, states_42,
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"\000\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000\000\000"},
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{298, "with_item", 0, 4, states_42,
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"\000\040\040\200\000\000\000\000\000\040\000\000\000\040\004\000\000\103\050\037\000"},
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{299, "except_clause", 0, 5, states_43,
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"\000\000\000\000\000\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000"},
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{300, "suite", 0, 5, states_44,
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