Avoid strange behavior regarding "narrowing" expressions for unreachability

Author: A5rocks

mypy/binder.py

@@ -153,8 +153,6 @@ def push_frame(self, conditional_frame: bool = False) -> Frame:
         return f
 
     def _put(self, key: Key, type: Type, from_assignment: bool, index: int = -1) -> None:
-        if isinstance(get_proper_type(type), UninhabitedType):
-            self.frames[index].unreachable = True
         self.frames[index].types[key] = CurrentType(type, from_assignment)
 
     def _get(self, key: Key, index: int = -1) -> CurrentType | None:
@@ -170,6 +168,9 @@ def put(self, expr: Expression, typ: Type, *, from_assignment: bool = True) -> N
 
         This is used for isinstance() etc. Assignments should go through assign_type().
         """
+        if isinstance(get_proper_type(typ), UninhabitedType):
+            self.frames[-1].unreachable = True
+
         if not isinstance(expr, (IndexExpr, MemberExpr, NameExpr)):
             return
         if not literal(expr):

test-data/unit/check-unreachable-code.test

@@ -1403,9 +1403,8 @@ from typing import Literal
 def nope() -> Literal[False]: ...
 
 def f() -> None:
-    # TODO: this should be unreachable
     if nope():
-        x = 1
+        x = 1  # E: Statement is unreachable
 [builtins fixtures/dict.pyi]
 
 [case testUnreachableLiteralFrom__bool__]
@@ -1428,7 +1427,7 @@ else:
     x = 2  # E: Statement is unreachable
 
 if Lie():
-    x = 3
+    x = 3  # E: Statement is unreachable
 
 if Maybe():
     x = 4