render "Never" instead of "<nothing>"

Author: KotlinIsland

mypy/messages.py

@@ -2300,6 +2300,8 @@ def format_literal_value(typ: LiteralType) -> str:
         if typ.is_noreturn:
             return "NoReturn"
         else:
+            if mypy.options._based:
+                return "Never"
             return "<nothing>"
     elif isinstance(typ, TypeType):
         if not mypy.options._based:

mypy/types.py

@@ -2893,6 +2893,8 @@ def visit_none_type(self, t: NoneType) -> str:
         return "None"
 
     def visit_uninhabited_type(self, t: UninhabitedType) -> str:
+        if mypy.options._based:
+            return "Never"
         return "<nothing>"
 
     def visit_erased_type(self, t: ErasedType) -> str:

test-data/unit/check-based-type-render.test

@@ -48,3 +48,13 @@ T = TypeVar("T", bound=int)
 
 def foo(t: T): ...
 reveal_type(foo)  # N: Revealed type is "def[T: int](t: T)"
+
+
+[case testInferredNever]
+a: bool
+if a: ...
+elif not a: ...
+else:
+    reveal_type(a)  # N: Revealed type is "Never"
+                    # E: Statement is unreachable  [unreachable]
+