Operator precedence in documentation wrong or misleading

[lukaszsamson]

Elixir and Erlang/OTP versions

Erlang/OTP 27 [erts-15.2.7.3] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]

Elixir 1.19.3 (compiled with Erlang/OTP 27)

Operating system

any

Current behavior

https://hexdocs.pm/elixir/1.19.3/operators.html lists :: as having lower precedence than =>, yet

Code.string_to_quoted!("%{a :: b => c}")
{:%{}, [line: 1],
 [
   {{:"::", [line: 1], [{:a, [line: 1], nil}, {:b, [line: 1], nil}]},
    {:c, [line: 1], nil}}
 ]}

Code.string_to_quoted!("%{a => b :: c}")
{:%{}, [line: 1],
 [
   {{:a, [line: 1], nil},
    {:"::", [line: 1], [{:b, [line: 1], nil}, {:c, [line: 1], nil}]}}
 ]}

proves that it has higher precedence

Similarly, other operators listed below => all have higher precedence

iex(16)> Code.string_to_quoted!("%{a | b => c}")
{:%{}, [line: 1],
 [
   {:|, [line: 1],
    [{:a, [line: 1], nil}, [{{:b, [line: 1], nil}, {:c, [line: 1], nil}}]]}
 ]}
iex(17)> Code.string_to_quoted!("%{a when b => c}")
{:%{}, [line: 1],
 [
   {{:when, [line: 1], [{:a, [line: 1], nil}, {:b, [line: 1], nil}]},
    {:c, [line: 1], nil}}
 ]}
iex(18)> Code.string_to_quoted!("%{a <- b => c}")
{:%{}, [line: 1],
 [
   {{:<-, [line: 1], [{:a, [line: 1], nil}, {:b, [line: 1], nil}]},
    {:c, [line: 1], nil}}
 ]}
iex(19)> Code.string_to_quoted!("%{a \\\\ b => c}")
{:%{}, [line: 1],
 [
   {{:\\, [line: 1], [{:a, [line: 1], nil}, {:b, [line: 1], nil}]},
    {:c, [line: 1], nil}}
 ]}

iex(23)> Code.string_to_quoted!("%{a => b | c}")
{:%{}, [line: 1],
 [
   {{:a, [line: 1], nil},
    {:|, [line: 1], [{:b, [line: 1], nil}, {:c, [line: 1], nil}]}}
 ]}
iex(24)> Code.string_to_quoted!("%{a => b when c}")
{:%{}, [line: 1],
 [
   {{:a, [line: 1], nil},
    {:when, [line: 1], [{:b, [line: 1], nil}, {:c, [line: 1], nil}]}}
 ]}
iex(25)> Code.string_to_quoted!("%{a => b <- c}")
{:%{}, [line: 1],
 [
   {{:a, [line: 1], nil},
    {:<-, [line: 1], [{:b, [line: 1], nil}, {:c, [line: 1], nil}]}}
 ]}
iex(26)> Code.string_to_quoted!("%{a => b \\\\ c}")
{:%{}, [line: 1],
 [
   {{:a, [line: 1], nil},
    {:\\, [line: 1], [{:b, [line: 1], nil}, {:c, [line: 1], nil}]}}
 ]}

with only exception being %{a | b => c} which is map update syntax

Expected behavior

Precedence table corrected

[josevalim]

with only exception being %{a | b => c} which is map update syntax

Yup, this is the root cause of the confusion (which is also very confusing when it comes to typespecs). I will likely need to add two entries to the table.

[josevalim]

Please check the PR for discussion!

[michallepicki]

@josevalim sorry if I'm missing something, where's the PR/discussion exactly?

[josevalim]

Thank you, i pushed but i forgot to open up a PR: #14964