Rename Red Knot (#17820)

crates/ty_python_semantic/resources/mdtest/expression/if.md

@@ -0,0 +1,41 @@
+# If expression
+
+## Union
+
+```py
+def _(flag: bool):
+    reveal_type(1 if flag else 2)  # revealed: Literal[1, 2]
+```
+
+## Statically known conditions in if-expressions
+
+```py
+reveal_type(1 if True else 2)  # revealed: Literal[1]
+reveal_type(1 if "not empty" else 2)  # revealed: Literal[1]
+reveal_type(1 if (1,) else 2)  # revealed: Literal[1]
+reveal_type(1 if 1 else 2)  # revealed: Literal[1]
+
+reveal_type(1 if False else 2)  # revealed: Literal[2]
+reveal_type(1 if None else 2)  # revealed: Literal[2]
+reveal_type(1 if "" else 2)  # revealed: Literal[2]
+reveal_type(1 if 0 else 2)  # revealed: Literal[2]
+```
+
+## Leaked Narrowing Constraint
+
+(issue #14588)
+
+The test inside an if expression should not affect code outside of the expression.
+
+```py
+from typing import Literal
+
+def _(flag: bool):
+    x: Literal[42, "hello"] = 42 if flag else "hello"
+
+    reveal_type(x)  # revealed: Literal[42, "hello"]
+
+    _ = ... if isinstance(x, str) else ...
+
+    reveal_type(x)  # revealed: Literal[42, "hello"]
+```