Add tests for a trailing Never call and an annotation-only class-body definition

Summary:
- What: Add `cut_off_by_trailing_call` to `test_unset_path_from_earlier_if_needs_every_branch_on_it`, and add an annotation-only definition to `test_class_body_initialization_is_independent_of_methods`.
- Why: Cover two cases that the existing tests miss: a path that misses an assignment and then stops at its own trailing `NoReturn` call, and a conditional annotation-only class-body definition that a method also assigns. The earlier `bug` version of the first test is gone: master already handles the case correctly (fixed by "Propagate conditional termination through nested flow merges"), and the other cases of this diff duplicated `cut_off_earlier` and `not_cut_off`.

Reviewed By: connernilsen

Differential Revision: D129184208

fbshipit-source-id: b2f1e202ce72a19120844ff6f142a3783940969d

Author: kinto0

pyrefly/lib/test/attributes.rs

@@ -90,9 +90,11 @@ def cond() -> bool: ...
 class Constructor:
     if cond():
         x = 1  # E: Attribute `x` may be uninitialized
+        y: int  # E: Attribute `y` may be uninitialized
 
     def __init__(self) -> None:
         self.x = 2
+        self.y = 2
 
 class Helper:
     if cond():

pyrefly/lib/test/flow_branching.rs

@@ -4811,6 +4811,17 @@ def cut_off_later(c: bool, d: bool) -> None:
         stop()
     print(x)
 
+def cut_off_by_trailing_call(c: bool, d: bool) -> None:
+    if c:
+        if d:
+            x = 1
+        else:
+            pass
+        stop()
+    else:
+        x = 2
+    print(x)
+
 def cut_off_earlier(c: bool, d: bool) -> None:
     if c:
         x = 1