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Raise clearer error when reserved word used at the top level of defmodule #15123

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Merged
sabiwara merged 2 commits into from
Mar 2, 2026
Merged

Raise clearer error when reserved word used at the top level of defmodule #15123

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Raise clearer error when reserved word used at the top level of defmo…
sabiwara Mar 2, 2026
3b2b2c7
Improve message: do-block
sabiwara Mar 2, 2026
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5 changes: 5 additions & 0 deletions lib/elixir/lib/kernel.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -5220,6 +5220,11 @@ defmodule Kernel do
end
end

defmacro defmodule(alias, [{:do, _block}, {atom, _} | _]) when is_atom(atom) do
raise ArgumentError,
"unexpected reserved word at the top-level of the \"defmodule #{Macro.to_string(alias)}\" do-block: #{atom}"
end
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@josevalim josevalim Mar 2, 2026

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Should we also have a catch-all? raise "expected do-block in defmodule, got: #{inspect(other)}" ?

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@sabiwara sabiwara Mar 2, 2026

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I wasn't so sure in the absence of a concrete example (maybe can happen with metaprogramming?), how much it would be more helpful since we'll end up emitting the AST anyway.
In the case of catch etc, we know exactly what the AST looks like, and the message is an improvement over the clause error.

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@josevalim josevalim Mar 2, 2026

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We can always add it later, so ship it!


defp module_meta({_, meta, _}), do: meta
defp module_meta(_), do: []

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12 changes: 12 additions & 0 deletions lib/elixir/test/elixir/kernel/errors_test.exs
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Expand Up @@ -1003,6 +1003,18 @@ defmodule Kernel.ErrorsTest do
)
end

test "reserved word used at module top-level" do
assert_eval_raise(
ArgumentError,
["unexpected reserved word at the top-level of the \"defmodule Foo\" do-block: catch"],
"""
defmodule Foo do
def foo, do: :foo catch :bar
end
"""
)
end

defp bad_remote_call(x), do: x.foo()

defmacro sample(0), do: 0
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