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Always rewrite signed numbers during expansion #12955

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Merged
merged 1 commit into from
Sep 23, 2023
Merged

Always rewrite signed numbers during expansion #12955

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3 changes: 3 additions & 0 deletions lib/elixir/src/elixir_expand.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -894,6 +894,9 @@ attach_context_module(Receiver, Meta, #{context_modules := ContextModules}) ->
false -> Meta
end.

% Signed numbers can be rewritten no matter the context
rewrite(_, erlang, _, '+', _, [Arg], _S) when is_number(Arg) -> {ok, Arg};
rewrite(_, erlang, _, '-', _, [Arg], _S) when is_number(Arg) -> {ok, -Arg};
rewrite(match, Receiver, DotMeta, Right, Meta, EArgs, _S) ->
elixir_rewrite:match_rewrite(Receiver, DotMeta, Right, Meta, EArgs);
rewrite(guard, Receiver, DotMeta, Right, Meta, EArgs, S) ->
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2 changes: 0 additions & 2 deletions lib/elixir/src/elixir_rewrite.erl
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Expand Up @@ -302,8 +302,6 @@ increment(Meta, Other) ->
%% The allowed operations are very limited.
%% The Kernel operators are already inlined by now, we only need to
%% care about Erlang ones.
match_rewrite(erlang, _, '+', _, [Arg]) when is_number(Arg) -> {ok, Arg};
match_rewrite(erlang, _, '-', _, [Arg]) when is_number(Arg) -> {ok, -Arg};
match_rewrite(erlang, _, '++', Meta, [Left, Right]) ->
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@josevalim josevalim Sep 23, 2023

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Can you please do a check later that we still need this one? I think recent Erlang versions started inlining ++ as well. :) It may be we can get rid of match_rewrite altogether!

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@sabiwara sabiwara Sep 23, 2023

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Sounds good, will definitely check!

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@sabiwara sabiwara Sep 25, 2023

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OK, I tried for a while but I don't think we can reasonably remove it without introducing regressions.

Issue 1: Elixir's current inlining is more powerful

iex(5)> [a] ++ bc = 'abc'
~c"abc"
1> [A] ++ BC = "abc".
* 1:5: illegal pattern

2> "a" ++ BC = "abc".
"abc"

Issue 2: Rewrite currently serves as validation, will need to translate more erlang errors

Currently:

iex(1)> "a" ++ "b" = "ab"
error: invalid argument for ++ operator inside a match, expected a literal proper list, got: "a"

Relying on erlang's inlining:

iex(1)> "a" ++ "b" = "ab"
** (ErlangError) Erlang error: {:illegal_pattern, {:op, 1, :++, {:bin, 1, [{:bin_element, 1, {:string, 1, ~c"a"}, :default, :default}]}, {:bin, 1, [{:bin_element, 1, {:string, 1, ~c"b"}, :default, :default}]}}}

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@josevalim josevalim Sep 25, 2023

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Thank you for checking!

try {ok, static_append(Left, Right, Meta)}
catch impossible -> {error, {invalid_match_append, Left}}
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4 changes: 2 additions & 2 deletions lib/elixir/test/elixir/kernel/expansion_test.exs
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Expand Up @@ -725,10 +725,10 @@ defmodule Kernel.ExpansionTest do
expand(quote(do: [1] ++ 2 ++ [3] = [1, 2, 3]))
end)

assert {:=, _, [-1, {{:., _, [:erlang, :-]}, _, [1]}]} =
assert {:=, _, [-1, -1]} =
expand(quote(do: -1 = -1))

assert {:=, _, [1, {{:., _, [:erlang, :+]}, _, [1]}]} =
assert {:=, _, [1, 1]} =
expand(quote(do: +1 = +1))

assert {:=, _, [[{:|, _, [1, [{:|, _, [2, 3]}]]}], [1, 2, 3]]} =
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