8000 Don't crash on aliases like C = C (#5632) · python/mypy@5e97a68 · GitHub
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ilevkivskyiilevkivskyi
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Don't crash on aliases like C = C (#5632)
Fixes #5631 Unfortunately one still needs to use `# type: ignores`, mypy has troubles understanding complex conditional definitions like in the issue: ```python try: ConnectionError = ConnectionError except NameError: class ConnectionError(Exception): pass ``` But this is a separate problem, that is harder to solve.
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5 files changed

+162
-1
lines changed

5 files changed

+162
-1
lines changed

‎mypy/fixup.py

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -236,7 +236,10 @@ def lookup_qualified_typeinfo(modules: Dict[str, MypyFile], name: str,
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return node
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else:
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# Looks like a missing TypeInfo in quick mode, put something there
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assert quick_and_dirty, "Should never get here in normal mode"
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assert quick_and_dirty, "Should never get here in normal mode," \
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" got {}:{} instead of TypeInfo".format(type(node).__name__,
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node.fullname() if node
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else '')
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return stale_info(modules)
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‎mypy/semanal.py

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1931,6 +1931,10 @@ def check_and_set_up_type_alias(self, s: AssignmentStmt) -> None:
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res, alias_tvars, depends_on, qualified_tvars = self.analyze_alias(rvalue)
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if not res:
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return
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if (isinstance(res, Instance) and res.type.name() == lvalue.name and
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res.type.module_name == self.cur_mod_id):
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# Aliases like C = C is a no-op.
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return
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s.is_alias_def = True
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node = self.lookup(lvalue.name, lvalue)
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assert node is not None

‎test-data/unit/check-incremental.test

Lines changed: 114 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -5193,3 +5193,117 @@ def f(x: str) -> None: pass
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[out]
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[out2]
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tmp/main.py:2: error: Argument 1 to "f" has incompatible type "int"; expected "str"
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[case testOverrideByIdemAlias]
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import a
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[file a.py]
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import lib
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x = 1
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[file a.py.2]
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import lib
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x = 2
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[file lib.py]
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C = C
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class C: # type: ignore
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pass
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[out]
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[out2]
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[case testOverrideByIdemAliasReversed]
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import a
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[file a.py]
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import lib
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x = 1
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[file a.py.2]
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import lib
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x = 2
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[file lib.py]
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class C:
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pass
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C = C # type: ignore
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x: C
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[out]
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[out2]
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[case testOverrideByIdemAliasGeneric]
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import a
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[file a.py]
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import lib
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x = 1
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[file a.py.2]
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import lib
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x = 2
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[file lib.py]
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from typing import Generic, TypeVar
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T = TypeVar('T')
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class C(Generic[T]):
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pass
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C = C[int] # type: ignore
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x: C
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[out]
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[out2]
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[case testOverrideByIdemAliasImported]
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import a
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[file a.py]
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import lib
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x = 1
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[file a.py.2]
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import lib
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x = 2
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[file lib.py]
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from other import C
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C = C # type: ignore
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x: C
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[file other.py]
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class C:
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pass
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[out]
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[out2]
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[case testOverrideByIdemAliasImportedReversed]
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import a
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[file a.py]
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import lib
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x = 1
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[file a.py.2]
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import lib
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x = 2
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[file lib.py]
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C = C # type: ignore
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from other import C
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[file other.py]
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class C:
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pass
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[out]
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[out2]
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[case testConditionalExceptionAliasOverride]
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import a
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[file a.py]
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import lib
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try:
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x = 1
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except lib.Exception as e:
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pass
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[file a.py.2]
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import lib
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try:
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x = 2
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except lib.Exception as e:
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pass
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[file lib.py]
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try:
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Exception = Exception
5300+
except BaseException:
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class Exception(BaseException): pass # type: ignore
5302+
5303+
try:
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pass
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except Exception as e:
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pass
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[builtins fixtures/exception.pyi]
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[out]
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[out2]

‎test-data/unit/check-type-aliases.test

Lines changed: 39 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -518,3 +518,42 @@ def foo(x: Bogus[int]) -> None:
518518
reveal_type(x) # E: Revealed type is 'builtins.int'
519519

520520
[builtins fixtures/dict.pyi]
521+
522+
[case testOverrideByIdemAliasCorrectType]
523+
C = C
524+
class C: # type: ignore
525+
pass
526+
x: C
527+
reveal_type(x) # E: Revealed type is '__main__.C'
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[out]
529+
530+
[case testOverrideByIdemAliasCorrectTypeReversed]
531+
class C:
532+
pass
533+
C = C # type: ignore
534+
x: C
535+
reveal_type(x) # E: Revealed type is '__main__.C'
536+
[out]
537+
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[case testOverrideByIdemAliasCorrectTypeImported]
539+
from other import C as B
540+
C = B
541+
x: C
542+
reveal_type(x) # E: Revealed type is 'other.C'
543+
[file other.py]
544+
class C:
545+
pass
546+
[out]
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[case testConditionalExceptionAlias]
549+
try:
550+
E = E
551+
except BaseException:
552+
class E(BaseException): pass # type: ignore
553+
554+
try:
555+
pass
556+
except E as e:
557+
reveal_type(e) # E: Revealed type is '__main__.E'
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[builtins fixtures/exception.pyi]
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[out]

‎test-data/unit/fixtures/exception.pyi

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -14,3 +14,4 @@ class bool: pass
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class ellipsis: pass
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class BaseException: pass
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class Exception(BaseException): pass

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