File 2362-Fix-an-unsafe-optimization-of-list-comprehensions.patch of Package erlang

From 397cf49e8786dd3657d9c432fb5ba1eec0059a06 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Thu, 5 Mar 2026 09:55:50 +0100
Subject: [PATCH] Fix an unsafe optimization of list comprehensions

An optimization that was introduced in 8f38c125c286919 is potentially
unsafe for zip generators.
---
 lib/compiler/src/sys_core_fold.erl     | 8 ++++----
 lib/compiler/test/bs_bincomp_SUITE.erl | 2 +-
 lib/compiler/test/zlc_SUITE.erl        | 1 +
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 4eb2331661..4e10bbcd62 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -2241,7 +2241,7 @@ opt_lc_body_1(Apply, #c_var{name=Name}, Fun0) ->
     maybe
         %% Look for a letrec body that constructs a list
         %% with a single element.
-        #c_apply{op=#c_var{name=Name},args=[Arg|_]} ?= Apply,
+        #c_apply{op=#c_var{name=Name},args=[Arg]} ?= Apply,
         true ?= cerl:is_c_list(Arg) andalso cerl:list_length(Arg) =:= 1,
 
         %% Now we know that the letrec body is suitable. Try to
@@ -2261,11 +2261,11 @@ opt_lc_definition(#c_fun{body=Case}=Fun, Name) ->
     maybe
         %% Match the case used in a list comprehension generator.
         #c_case{clauses=Cs0} ?= Case,
-        [#c_clause{pats=[#c_cons{tl=Tail}|_],body=C1Body0}=C1,
-         #c_clause{pats=[#c_cons{tl=Tail}|_],guard=#c_literal{val=true},
+        [#c_clause{pats=[#c_cons{tl=Tail}],body=C1Body0}=C1,
+         #c_clause{pats=[#c_cons{tl=Tail}],guard=#c_literal{val=true},
                    body=#c_apply{op=#c_var{name=Name},
                                  args=[Tail|_]}}=C2,
-         #c_clause{pats=[#c_literal{val=[]}|_],body=Iterate}|_] ?= Cs0,
+         #c_clause{pats=[#c_literal{val=[]}],body=Iterate}|_] ?= Cs0,
 
         %% Replace self-recursion with the body of the clause matching
         %% the empty list.
diff --git a/lib/compiler/test/bs_bincomp_SUITE.erl b/lib/compiler/test/bs_bincomp_SUITE.erl
index cdf2f6e50a..967ba0ba13 100644
--- a/lib/compiler/test/bs_bincomp_SUITE.erl
+++ b/lib/compiler/test/bs_bincomp_SUITE.erl
@@ -135,7 +135,7 @@ mixed(Config) when is_list(Config) ->
     %% OTP-16899: Nested binary comprehensions would fail to load.
     <<0,1,0,2,0,3,99>> = mixed_nested([1,2,3]),
 
-    <<1>> = cs(<< <<X>> || L <- [[1]], X <- L >>),
+    <<1>> = cs_default(<< <<X>> || L <- [[1]], X <- L >>),
     <<1,2>> = cs_default(<< <<X>> || L <- [[1,2]], X <- L >>),
 
     %% The compiler would crash in v3_kernel.
-- 
2.51.0