[3.12] gh-125832: Clarify comment for inlined comprehensions as per P… (gh-126345)

* [3.12] gh-125832: Clarify comment for inlined comprehensions as per PEP-709 (gh-126322)

* Fix comprehensions comment to inlined by pep 709

* Update spacing

Co-authored-by: RUANG (James Roy) <[email protected]>

* Add reference to PEP 709

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Co-authored-by: Carol Willing <[email protected]>
Co-authored-by: RUANG (James Roy) <[email protected]>

* Add space

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Co-authored-by: rimchoi <[email protected]>
Co-authored-by: Carol Willing <[email protected]>
Co-authored-by: RUANG (James Roy) <[email protected]>

Author: 4 people

Python/compile.c

@@ -5191,9 +5191,12 @@ compiler_call_helper(struct compiler *c, location loc,
 }
 
 
-/* List and set comprehensions and generator expressions work by creating a
-  nested function to perform the actual iteration. This means that the
-  iteration variables don't leak into the current scope.
+/* List and set comprehensions work by being inlined at the location where
+  they are defined. The isolation of iteration variables is provided by
+  pushing/popping clashing locals on the stack. Generator expressions work
+  by creating a nested function to perform the actual iteration.
+  This means that the iteration variables don't leak into the current scope.
+  See https://peps.python.org/pep-0709/ for additional information.
   The defined function is called immediately following its definition, with the
   result of that call being the result of the expression.
   The LC/SC version returns the populated container, while the GE version is