[dynamo] Add recompile reason for set_stance fail_on_recompile (#165445)

Fixes #163500

### Summary:
For `set_stance("fail_on_recompile")` failures will provide the reason why the recompilation occurred

### Impacts:
module: dynamo

Pull Request resolved: https://github.com/pytorch/pytorch/pull/165445
Approved by: https://github.com/williamwen42

test/dynamo/test_decorators.py

@@ -2,6 +2,7 @@
 import functools
 import operator
 import os
+import re
 import unittest.mock as mock
 from unittest.mock import patch
 
@@ -1472,6 +1473,30 @@ class DecoratorTests(torch._dynamo.test_case.TestCase):
         self.assertEqual(out1, inp + 2)
         self.assertEqual(out2, inp + 2)
 
+    def test_fail_on_recompile_shows_guard_details(self):
+        @torch.compile(backend="eager", dynamic=False)
+        def f(x):
+            return x + 1
+
+        f(torch.ones(4))
+        f(torch.ones(5))
+
+        def post_munge(s):
+            return re.sub(r"line number: \d+", "line number: N", s)
+
+        with torch.compiler.set_stance("fail_on_recompile"):
+            f(torch.ones(4))
+            self.assertExpectedInlineMunged(
+                RuntimeError,
+                lambda: f(torch.ones(7)),
+                """\
+Detected recompile when torch.compile stance is 'fail_on_recompile'. filename: 'test_decorators.py', function name: 'f', line number: N
+    triggered by the following guard failure(s):
+    - 0/0: tensor 'x' size mismatch at index 0. expected 4, actual 7
+    - 0/1: tensor 'x' size mismatch at index 0. expected 5, actual 7""",  # noqa: B950
+                post_munge=post_munge,
+            )
+
     def test_set_stance_fail_on_recompile_with_disable(self):
         @torch.compiler.disable
         def inner(x):