Description
Bug Report
When assigning to variables within an if elif block, mypy appears to incorrectly carry the assigned type between blocks (where it can never have been assigned in the else part).
To Reproduce
Using a very contrived example, which causes a common variable name to be "reused" between types;
x = 1
if x == 1:
record = 1
elif x == 2:
record = ""
mypy reports an incompatible type
$ mypy --strict test.py
test.py:5: error: Incompatible types in assignment (expression has type "str", variable has type "int")
Found 1 error in 1 file (checked 1 source file)
Expected Behavior
Since the second record variable cannot have been assigned (otherwise we would have never got to this block), it cannot have the type of int.
mypy should treat it as an unassigned variable and associate the new str type at the point of assignment.
Effectively this should result in no errors and be the same logically as e.g.
x = 1
if x == 1:
record1 = 1
elif x == 2:
record2 = ""
Which passes cleanly;
$ mypy --strict test.py
Success: no issues found in 1 source file
Actual Behavior
mypy appears to be carrying the inferred type of the first assignment (in the if block) over into the second (elif block) assignment, even though the variable has not been assigned.
mypy view of the world;
test.py:8: note: Revealed type is "builtins.int"
python view of the world;
Traceback (most recent call last):
File "/divesoft-parser/test.py", line 8, in <module>
reveal_type(record)
NameError: name 'record' is not defined
Your Environment
- Mypy version used:
mypy 0.950 (compiled: yes) - Mypy command-line flags:
--strict - Mypy configuration options from
mypy.ini(and other config files): None - Python version used:
3.9.12 - Operating system and version:
OSX 11.6.5
x-ref https://gitter.im/python/typing?at=626ac42846495f47cfb712a3