File 0550-dialyzer-Correct-interpretation-of-none.patch of Package erlang

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File 0550-dialyzer-Correct-interpretation-of-none.patch of Package erlang (Revision de30b468b03575187646e08759bd0cf9)

Currently displaying revision de30b468b03575187646e08759bd0cf9 , Show latest

From 982de2929cf347739917532c764d13e133736927 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Thu, 6 Oct 2022 07:10:55 +0200
Subject: [PATCH] dialyzer: Correct interpretation of [none()]

Given the following module:

-module(list_none).
    -export([new/0]).

-spec new() -> list(none()).
    new() -> [].

dialyzer emits the following warning:

list_none.erl:4:2: Invalid type specification for function list_none:new/0. The success typing is
              () -> []

No warning is expected, since `list(Type)` means a list containing zero
or more elements. Even if `Type` is impossible, the empty list is
still possible. Therefore, the success typing and the spec are
consistent with each other.

Closes #6333
---
 lib/dialyzer/src/erl_types.erl                    |  4 +---
 lib/dialyzer/test/small_SUITE_data/results/stack  |  0
 .../test/small_SUITE_data/src/list_none.erl       |  5 +++++
 lib/dialyzer/test/small_SUITE_data/src/stack.erl  | 15 +++++++++++++++
 4 files changed, 21 insertions(+), 3 deletions(-)
 create mode 100644 lib/dialyzer/test/small_SUITE_data/results/stack
 create mode 100644 lib/dialyzer/test/small_SUITE_data/src/list_none.erl
 create mode 100644 lib/dialyzer/test/small_SUITE_data/src/stack.erl

diff --git a/lib/dialyzer/src/erl_types.erl b/lib/dialyzer/src/erl_types.erl
index 9abd967cd1..83b12b3041 100644
--- a/lib/dialyzer/src/erl_types.erl
+++ b/lib/dialyzer/src/erl_types.erl
@@ -1468,10 +1468,8 @@ t_list() ->
 
 -spec t_list(erl_type()) -> erl_type().
 
-t_list(?none) -> ?none;
-t_list(?unit) -> ?none;
 t_list(Contents) ->
-  ?list(Contents, ?nil, ?unknown_qual).
+  t_sup(t_nonempty_list(Contents), t_nil()).
 
 -spec t_list_elements(erl_type()) -> erl_type().
 
diff --git a/lib/dialyzer/test/small_SUITE_data/results/stack b/lib/dialyzer/test/small_SUITE_data/results/stack
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/lib/dialyzer/test/small_SUITE_data/src/list_none.erl b/lib/dialyzer/test/small_SUITE_data/src/list_none.erl
new file mode 100644
index 0000000000..7fb40133e7
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/list_none.erl
@@ -0,0 +1,5 @@
+-module(list_none).
+-export([new/0]).
+
+-spec new() -> list(none()).
+new() -> [].
diff --git a/lib/dialyzer/test/small_SUITE_data/src/stack.erl b/lib/dialyzer/test/small_SUITE_data/src/stack.erl
new file mode 100644
index 0000000000..080ce7e3b9
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/stack.erl
@@ -0,0 +1,15 @@
+-module(stack).
+
+-export([new/0, push/2, pop/1]).
+-export_type([stack/1]).
+
+-opaque stack(A) :: [A].
+
+-spec new() -> stack(none()).
+new() -> [].
+
+-spec push(stack(A), A) -> stack(A).
+push(T, H) -> [H | T].
+
+-spec pop(stack(A)) -> {A, stack(A)}.
+pop([H | T]) -> {H, T}.
-- 
2.35.3

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File 0550-dialyzer-Correct-interpretation-of-none.patch of Package erlang (Revision de30b468b03575187646e08759bd0cf9)

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