fix handling of asserts in postprocessing

crates/ruff_linter/resources/test/fixtures/control-flow-graph/for.py

@@ -60,3 +60,12 @@ def func():
         pass
     else:
         pass
+
+def func():
+        for i in range(3):
+            if i == 2:
+                assert i is not None
+                break
+        else:
+            raise Exception()
+        x = 0

crates/ruff_linter/src/rules/ruff/rules/snapshots/ruff_linter__rules__ruff__rules__unreachable__tests__for.py.md.snap

@@ -355,3 +355,51 @@ flowchart TD
   block1 --> block0
   block0 --> return
 ```
+
+## Function 11
+### Source
+```python
+def func():
+        for i in range(3):
+            if i == 2:
+                assert i is not None
+                break
+        else:
+            raise Exception()
+        x = 0
+```
+
+### Control Flow Graph
+```mermaid
+flowchart TD
+  start(("Start"))
+  return(("End"))
+  block0["x = 0\n"]
+  block1["raise Exception()\n"]
+  block2[["Loop continue"]]
+  block3["break\n"]
+  block4[["Exception raised"]]
+  block5["assert i is not None\n"]
+  block6["if i == 2:
+                assert i is not None
+                break\n"]
+  block7["for i in range(3):
+            if i == 2:
+                assert i is not None
+                break
+        else:
+            raise Exception()\n"]
+
+  start --> block7
+  block7 -- "range(3)" --> block6
+  block7 -- "else" --> block1
+  block6 -- "i == 2" --> block5
+  block6 -- "else" --> block2
+  block5 -- "i is not None" --> block3
+  block5 -- "else" --> block4
+  block4 --> return
+  block3 --> block0
+  block2 --> block7
+  block1 --> return
+  block0 --> return
+```

crates/ruff_linter/src/rules/ruff/rules/unreachable.rs

@@ -894,13 +894,17 @@ impl<'stmt> BasicBlocksBuilder<'stmt> {
                     match block.stmts.last() {
                         Some(Stmt::For(_) | Stmt::While(_)) => {
                             self.post_process(next, Some(idx), exit, exit);
+                            idx = orelse;
+                        }
+                        Some(Stmt::Assert(_)) => {
+                            self.post_process(orelse, loop_start, loop_exit, exit);
+                            idx = next;
                         }
                         _ => {
                             self.post_process(next, loop_start, loop_exit, exit);
+                            idx = orelse;
                         }
                     };
-
-                    idx = orelse;
                 }
                 NextBlock::Terminate => return,
             }