File 0116-Improve-error-messages-for-lists-seq-3.patch of Package erlang

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File 0116-Improve-error-messages-for-lists-seq-3.patch of Package erlang

From 4c213fe478dc41a146b804fd12258230d248a77a Mon Sep 17 00:00:00 2001
From: nixxquality <nixx@is-fantabulo.us>
Date: Tue, 7 Dec 2021 12:11:13 +0100
Subject: [PATCH] Improve error messages for lists:seq/3

---
 lib/stdlib/src/erl_stdlib_errors.erl | 15 ++++++++++++++-
 lib/stdlib/src/lists.erl             | 20 ++++++++++----------
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/lib/stdlib/src/erl_stdlib_errors.erl b/lib/stdlib/src/erl_stdlib_errors.erl
index 91d8cb9362..c2e41fd496 100644
--- a/lib/stdlib/src/erl_stdlib_errors.erl
+++ b/lib/stdlib/src/erl_stdlib_errors.erl
@@ -189,7 +189,20 @@ format_lists_error(keysearch, Args) ->
 format_lists_error(member, [_Key, List]) ->
     [[], must_be_list(List)];
 format_lists_error(reverse, [List, _Acc]) ->
-    [must_be_list(List)].
+    [must_be_list(List)];
+format_lists_error(seq, [First, Last, Inc]) ->
+    case [must_be_integer(First), must_be_integer(Last), must_be_integer(Inc)] of
+        [[], [], []] ->
+            IncError = if
+                (Inc =< 0 andalso First - Inc =< Last) ->
+                    <<"not a positive increment">>;
+                (Inc >= 0 andalso First - Inc >= Last) ->
+                    <<"not a negative increment">>
+            end,
+            [[], [], IncError];
+        Errors -> Errors
+    end.
+
 
 format_maps_error(filter, Args) ->
     format_maps_error(map, Args);
diff --git a/lib/stdlib/src/lists.erl b/lib/stdlib/src/lists.erl
index 63d55f5630..11c9e25711 100644
--- a/lib/stdlib/src/lists.erl
+++ b/lib/stdlib/src/lists.erl
@@ -259,16 +259,16 @@ seq_loop(0, _, L) ->
       Incr :: integer(),
       Seq :: [integer()].
 
-seq(First, Last, Inc) 
-    when is_integer(First), is_integer(Last), is_integer(Inc) -> 
-    if
-        Inc > 0, First - Inc =< Last;
-        Inc < 0, First - Inc >= Last ->
-            N = (Last - First + Inc) div Inc,
-            seq_loop(N, Inc*(N-1)+First, Inc, []);
-        Inc =:= 0, First =:= Last ->
-            seq_loop(1, First, Inc, [])
-    end.
+seq(First, Last, Inc)
+    when is_integer(First), is_integer(Last), is_integer(Inc),
+        (Inc > 0 andalso First - Inc =< Last) orelse
+        (Inc < 0 andalso First - Inc >= Last) ->
+    N = (Last - First + Inc) div Inc,
+    seq_loop(N, Inc * (N - 1) + First, Inc, []);
+seq(Same, Same, 0) when is_integer(Same) ->
+    [Same];
+seq(First, Last, Inc) ->
+    erlang:error(badarg, [First, Last, Inc], [{error_info, #{module => erl_stdlib_errors}}]).
 
 seq_loop(N, X, D, L) when N >= 4 ->
      Y = X-D, Z = Y-D, W = Z-D,
-- 
2.31.1

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File 0116-Improve-error-messages-for-lists-seq-3.patch of Package erlang

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