add test for 19918: our example code

Author: wyattscarpenter

test-data/unit/check-redefine.test

@@ -636,3 +636,11 @@ def _(arg: str) -> str: # E: Name "_" already defined (possibly by an import)
 [file a.py]
 def f(s: str) -> str:
     return s
+
+[case testRedefineListComprehension]
+# flags: --allow-redefinition
+def process(items: list[str]) -> None:
+    reveal_type(items) # N: Revealed type is "builtins.list[builtins.str]"
+    items = [item.split() for item in items]
+    reveal_type(items) # N: Revealed type is "builtins.list[builtins.list[builtins.str]]"
+[builtins fixtures/primitives.pyi]

test-data/unit/check-redefine2.test

@@ -1197,3 +1197,11 @@ x = 0
 if int():
     x = ""
 reveal_type(x) # N: Revealed type is "builtins.int | builtins.str"
+
+[case testNewRedefineListComprehension]
+# flags: --allow-redefinition-new --local-partial-types
+def process(items: list[str]) -> None:
+    reveal_type(items) # N: Revealed type is "builtins.list[builtins.str]"
+    items = [item.split() for item in items]
+    reveal_type(items) # N: Revealed type is "builtins.list[builtins.list[builtins.str]]"
+[builtins fixtures/primitives.pyi]

test-data/unit/fixtures/primitives.pyi

@@ -35,6 +35,8 @@ class str(Sequence[str]):
     def __contains__(self, other: object) -> bool: pass
     def __getitem__(self, item: int) -> str: pass
     def format(self, *args: object, **kwargs: object) -> str: pass
+    # Note: this is a simplification of the actual signature
+    def split(self, sep: str | None = None) -> list[str]: pass
 class bytes(Sequence[int]):
     def __iter__(self) -> Iterator[int]: pass
     def __contains__(self, other: object) -> bool: pass