I'm in support of this 👌
It's a reasonable trade off from other concerns and as someone who works with
people moving from other languages to Elixir often, they are *constantly*
looking for this syntax. Given that this exact syntax is used in other
languages also adds some regularity to it, despite my personal preference for
js style %{a, b}. The "accidentally being a tuple" issue with that syntax goes
away for 99% of cases conveniently with the type system FWIW :)
On Sun, Dec 21, 2025 at 10:58 AM, Danila Poyarkov < [email protected] > wrote:
>
> Hi everyone,
>
> José Valim suggested I move the discussion here from my PR:
> https://github.com/elixir-lang/elixir/pull/15023
>
> I've implemented shorthand syntax for atom-keyed maps and keywords:
>
> ```elixir
> %{user:, conn:} # => %{user: user, conn: conn}
> [foo:, bar:] # => [foo: foo, bar: bar]
> f(name:, age:) # => f(name: name, age: age)
> %{map | a:, b:} # => %{map | a: a, b: b}
> ```
>
> I know this topic has been discussed many times before:
>
> - Proposal: Short Hand Property Names (2017):
> https://groups.google.com/g/elixir-lang-core/c/XxnrGgZsyVc
> - Consider supporting a map shorthand syntax (2018):
> https://groups.google.com/g/elixir-lang-core/c/NoUo2gqQR3I
> - ES6-ish property value shorthands for maps? (2016):
> https://elixirforum.com/t/es6-ish-property-value-shorthands-for-maps/1524
> - Has Map shorthand syntax caused you any problems? (2018):
> https://elixirforum.com/t/has-map-shorthand-syntax-in-other-languages-caused-you-any-problems/15403
>
>
> Most of these discussed the ES6-style `%{a, b}` syntax, which José made
> clear had "zero chance" of being accepted — mainly because `%{a, b}` vs
> `{a, b}` differs by one character, making maps and tuples too easy to
> confuse.
>
> The colon-based syntax `%{a:, b:}` is different. The `:` that signals
> "this is a key-value pair" stays there. There's no visual confusion with
> tuples because `{a:, b:}` is not valid Elixir syntax anyway.
>
> José mentioned in the PR that he actually prefers this approach over bare
> variables, but it was "deemed not acceptable by most people" in a previous
> discussion. I'd like to understand what the objections were.
>
> Reading through the old threads, I found these concerns:
>
> - "Removing explicitness for the sake of brevity doesn't appeal to me."
> (Chris Keathley)
> - "Shorthand syntax makes that coupling even less obvious" — if you change
> a key, you need to find all functions that relied on that variable name.
> (Chris Keathley)
> - "This will just add complexity to the language to save a few keystrokes
> for advanced users." (Matt Widmann)
>
> These discussions happened in 2016-2018. Since then, Ruby 3.1 shipped this
> exact syntax in December 2021 — almost 4 years ago. The syntax is `{x:,
> y:}` for hashes and `foo(x:, y:)` for keyword arguments, exactly what I'm
> proposing for Elixir.
>
> The Ruby reception was mixed at first — Bozhidar Batsov (RuboCop
> maintainer) was critical
> (https://batsov.com/articles/2022/01/20/bad-ruby-hash-value-omission/) but
> still allowed it in RuboCop defaults. Four years later, the syntax is
> widely used.
>
> The same pattern (sometimes called "field punning") also exists in Rust
> and OCaml.
>
> `%{user: user, conn: conn}` is already common in Elixir — this just
> removes the repetition. The colon stays visible, so it's not as "magic" as
> the bare variable approach. And Ruby has been using it for 4 years now
> without issues.
>
> The implementation is ready and all tests pass. I'm curious whether
> opinions have changed since 2018.
>
>
>
>
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