:erlang.size/1 cannot be used in guard clauses in 1.10

[joseph-lozano]

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Environment

• Elixir & Erlang/OTP versions (elixir --version): 1.10
• Operating system: MacOS

Current behavior

:erlang.size/1 cannot be used in guard clauses. Instead, when trying to use the function, the below error gets emitted. While I understand that byte_size could be used instead. I have dependencies that use :erlang.size and so I am prevented from upgrading.

** (EXIT from #PID<0.92.0>) an exception was raised:
    ** (KeyError) key {:size, 1} not found in: %{{:ceil, 1} => {[:number], :integer}, {:<, 2} => {[:dynamic, :dynamic], :boolean}, {:floor, 1} => {[:number], :integer}, {:byte_size, 1} => {[:binary], :integer}, {:bxor, 2} => {[:integer, :integer], :integer}, {:is_tuple, 1} => {[:tuple], :boolean}, {:is_function, 1} => {[:fun], :boolean}, {:bit_size, 1} => {[:binary], :integer}, {:is_integer, 1} => {[:integer], :boolean}, {:bor, 2} => {[:integer, :integer], :integer}, {:+, 1} => {[:number], :number}, {:is_map_key, 2} => {[:dynamic, {:map, []}], :dynamic}, {:+, 2} => {[:number, :number], :number}, {:"=/=", 2} => {[:dynamic, :dynamic], :boolean}, {:hd, 1} => {[list: :dynamic], :dynamic}, {:xor, 2} => {[:boolean, :boolean], :boolean}, {:>, 2} => {[:dynamic, :dynamic], :boolean}, {:-, 2} => {[:number, :number], :number}, {:==, 2} => {[:dynamic, :dynamic], :boolean}, {:length, 1} => {[list: :dynamic], :integer}, {:is_reference, 1} => {[:reference], :boolean}, {:*, 2} => {[:number, :number], :number}, {:bnot, 1} => {[:integer], :integer}, {:node, 1} => {[union: [:pid, :reference, :port]], :atom}, {:band, 2} => {[:integer, :integer], :integer}, {:bsl, 2} => {[:integer, :integer], :integer}, {:is_float, 1} => {[:float], :boolean}, {:not, 1} => {[:boolean], :boolean}, {:is_pid, 1} => {[:pid], :boolean}, {:is_list, 1} => {[list: :dynamic], :boolean}, {:element, 2} => {[:integer, :tuple], :dynamic}, {:tl, 1} => {[list: :dynamic], :dynamic}, {:is_map, 1} => {[map: []], :boolean}, {:"=:=", 2} => {[:dynamic, :dynamic], :boolean}, {:"/=", 2} => {[:dynamic, :dynamic], :boolean}, {:-, 1} => {[:number], :number}, {:trunc, 1} => {[:number], :integer}, {:"=<", 2} => {[:dynamic, :dynamic], :boolean}, {:abs, 1} => {[:number], :number}, {:bsr, 2} => {[:integer, :integer], :integer}, {:map_size, 1} => {[map: []], :integer}, {:is_binary, 1} => {[:binary], :boolean}, {:div, 2} => {[:integer, :integer], :integer}, {:is_boolean, 1} => {[:boolean], :boolean}, {:is_function, 2} => {[:fun, :integer], :boolean}, {:is_bitstring, 1} => {[:binary], :boolean}, {:binary_part, 3} => {[:binary, :integer, ...], :binary}, {:round, 1} => {[:number], :integer}, {:rem, ...} => {[...], ...}, {...} => {...}, ...}

Expected behavior

In previous versions of elixir, (verified on 1.9.4), using :erlang.size could be used in guard clauses. I didn't see anything about this change in the changelog and believe it to be unintentional.

Code example

Run the below code as an exs script to produce the error in 1.10, or in 1.9.4 to see it working as intended.

defmodule Foo do
  def test(bar) when :erlang.size(bar) == 2 do
    :ok
  end

  def test(_) do
    :not_ok
  end
end

Foo.test("a") |> IO.inspect()
Foo.test("ab") |> IO.inspect()