Rename Red Knot (#17820)

crates/ty_python_semantic/resources/mdtest/narrow/while.md

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+# Narrowing in `while` loops
+
+We only make sure that narrowing works for `while` loops in general, we do not exhaustively test all
+narrowing forms here, as they are covered in other tests.
+
+Note how type narrowing works subtly different from `if` ... `else`, because the negated constraint
+is retained after the loop.
+
+## Basic `while` loop
+
+```py
+def next_item() -> int | None:
+    return 1
+
+x = next_item()
+
+while x is not None:
+    reveal_type(x)  # revealed: int
+    x = next_item()
+
+reveal_type(x)  # revealed: None
+```
+
+## `while` loop with `else`
+
+```py
+def next_item() -> int | None:
+    return 1
+
+x = next_item()
+
+while x is not None:
+    reveal_type(x)  # revealed: int
+    x = next_item()
+else:
+    reveal_type(x)  # revealed: None
+
+reveal_type(x)  # revealed: None
+```
+
+## Nested `while` loops
+
+```py
+from typing import Literal
+
+def next_item() -> Literal[1, 2, 3]:
+    raise NotImplementedError
+
+x = next_item()
+
+while x != 1:
+    reveal_type(x)  # revealed: Literal[2, 3]
+
+    while x != 2:
+        # TODO: this should be Literal[1, 3]; Literal[3] is only correct
+        # in the first loop iteration
+        reveal_type(x)  # revealed: Literal[3]
+        x = next_item()
+
+    x = next_item()
+```