Incorrect narrowing of class/global variables in nested scopes #916
Description
Summary
In the following code, g in the class scope D should be inferred as str | None, but is instead inferred as str.
g: str | None = None
def f(flag: bool):
class C:
if flag:
g = 1
if g is not None: # this `g` may refer to a class variable, or a global variable
class D:
# refers to the global `g`
reveal_type(g) # should be: str | NoneHere, it appears that we have mistakenly applied the narrowing constraint g is not None to the global variable g.
However, simply checking the symbol table and not recording an eager snapshot if the class variable C.g is bound is not sufficient. In the following example, we can safely narrow the global g because we can assume that C.g is undefined in class D.
g: str | None = None
def f(flag: bool):
class C:
if flag:
g = None
if g is not None: # if this evaluates to `True`, `g` must refer to a global variable
class D:
reveal_type(g) # revealed: strThis is already checked in mdtest/narrow/conditionals/nested.md.
Version
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