[pylint] Fix unreachable infinite loop (PLW0101) (#15278)

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## Summary

Fix infinite loop issue reported here #15248.
The issue was caused by the break inside the if block, which caused the
flow to exit in an unforeseen way. This caused other issues, eventually
leading to an infinite loop.

Resolves #15248. Resolves #15336.

## Test Plan

Added failing code to fixture.

---------

Co-authored-by: Micha Reiser <[email protected]>
Co-authored-by: dylwil3 <[email protected]>

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

@@ -116,3 +116,15 @@ def func():
 
     finally:
         raise Exception("other")
+
+# previously caused infinite loop
+# found by fuzzer
+def func():
+ for i in():
+    try:
+        try:
+         while r:
+          if t:break
+        finally:()
+        return
+    except:l

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

@@ -145,3 +145,12 @@ def bokeh2(self, host: str = DEFAULT_HOST, port: int = DEFAULT_PORT) -> None:
             port += 1
 
     self.thread = threading.Thread(target=self._run_web_server)
+
+def func():
+    while T:
+        try:
+            while():
+                if 3:
+                    break
+        finally:
+            return

crates/ruff_linter/src/rules/pylint/rules/snapshots/ruff_linter__rules__pylint__rules__unreachable__tests__try.py.md.snap

@@ -708,3 +708,76 @@ flowchart TD
   block1 --> return
   block0 --> return
 ```
+
+## Function 13
+### Source
+```python
+def func():
+ for i in():
+    try:
+        try:
+         while r:
+          if t:break
+        finally:()
+        return
+    except:l
+```
+
+### Control Flow Graph
+```mermaid
+flowchart TD
+  start(("Start"))
+  return(("End"))
+  block0[["`*(empty)*`"]]
+  block1[["Loop continue"]]
+  block2["return\n"]
+  block3["()\n"]
+  block4[["Loop continue"]]
+  block5["break\n"]
+  block6["if t:break\n"]
+  block7["while r:
+          if t:break\n"]
+  block8[["Exception raised"]]
+  block9["try:
+         while r:
+          if t:break
+        finally:()\n"]
+  block10[["Exception raised"]]
+  block11["l\n"]
+  block12["try:
+        try:
+         while r:
+          if t:break
+        finally:()
+        return
+    except:l\n"]
+  block13["for i in():
+    try:
+        try:
+         while r:
+          if t:break
+        finally:()
+        return
+    except:l\n"]
+
+  start --> block13
+  block13 -- "()" --> block12
+  block13 -- "else" --> block0
+  block12 -- "Exception raised" --> block11
+  block12 -- "else" --> block9
+  block11 --> block1
+  block10 --> return
+  block9 -- "Exception raised" --> block8
+  block9 -- "else" --> block7
+  block8 --> block3
+  block7 -- "r" --> block6
+  block7 -- "else" --> block3
+  block6 -- "t" --> block5
+  block6 -- "else" --> block4
+  block5 --> block3
+  block4 --> block7
+  block3 --> block2
+  block2 --> return
+  block1 --> block13
+  block0 --> return
+```

crates/ruff_linter/src/rules/pylint/rules/snapshots/ruff_linter__rules__pylint__rules__unreachable__tests__while.py.md.snap

@@ -777,3 +777,63 @@ flowchart TD
   block1 --> block7
   block0 --> return
 ```
+
+## Function 23
+### Source
+```python
+def func():
+    while T:
+        try:
+            while():
+                if 3:
+                    break
+        finally:
+            return
+```
+
+### Control Flow Graph
+```mermaid
+flowchart TD
+  start(("Start"))
+  return(("End"))
+  block0[["`*(empty)*`"]]
+  block1[["Loop continue"]]
+  block2["return\n"]
+  block3[["Loop continue"]]
+  block4["break\n"]
+  block5["if 3:
+                    break\n"]
+  block6["while():
+                if 3:
+                    break\n"]
+  block7[["Exception raised"]]
+  block8["try:
+            while():
+                if 3:
+                    break
+        finally:
+            return\n"]
+  block9["while T:
+        try:
+            while():
+                if 3:
+                    break
+        finally:
+            return\n"]
+
+  start --> block9
+  block9 -- "T" --> block8
+  block9 -- "else" --> block0
+  block8 -- "Exception raised" --> block7
+  block8 -- "else" --> block6
+  block7 --> block2
+  block6 -- "()" --> block5
+  block6 -- "else" --> block2
+  block5 -- "3" --> block4
+  block5 -- "else" --> block3
+  block4 --> block2
+  block3 --> block6
+  block2 --> return
+  block1 --> block9
+  block0 --> return
+```

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

@@ -462,6 +462,7 @@ fn post_process_loop(
                     Some(Stmt::Continue(_)) => {
                         block.next = NextBlock::Always(loop_start);
                     }
+                    Some(Stmt::Return(_)) => return,
                     _ => {}
                 };
                 idx = next;
@@ -603,6 +604,7 @@ fn post_process_try(
             NextBlock::Always(next) => {
                 next_index = *next;
                 match block.stmts.last() {
+                    Some(Stmt::Break(_)) => return,
                     Some(Stmt::Continue(_)) => return,
                     Some(Stmt::Raise(_)) => {
                         // re-route to except if not already re-routed