This warning can be removed by expanding all possible "foo" clause
combinations.
The nice thing would be the warning to make this clear, and preferably, by
listing which clauses cannot be called and suggesting the developer to
expand all possible clause combinations.
Cheers
sexta-feira, 12 de Abril de 2019 às 14:49:59 UTC+1, Mário Guimarães
escreveu:
>
> Hello
>
> given the following module
>
> defmodule X do
> def foo(a, c), do: foo(a, :b, c)
> def foo(a, b \\ "2", c \\ "3"), do: IO.inspect {a, b, c}
> end
>
> Elixir emits the following warning
>
> Interactive Elixir (1.8.1) - press Ctrl+C to exit (type h() ENTER for help
> )
> iex(1)> defmodule X do
> ...(1)> def foo(a, c), do: foo(a, :b, c)
> ...(1)> def foo(a, b \\ "2", c \\ "3"), do: IO.inspect {a, b, c}
> ...(1)> end
> warning: this clause cannot match because a previous clause at line 2
> always matches
> iex:3
>
> {:module, X,
> <<70, 79, 82, 49, 0, 0, 5, 104, 66, 69, 65, 77, 65, 116, 85, 56, 0, 0, 0,
> 139,
> 0, 0, 0, 16, 8, 69, 108, 105, 120, 105, 114, 46, 88, 8, 95, 95, 105,
> 110,
> 102, 111, 95, 95, 7, 99, 111, 109, 112, ...>>, {:foo, 3}}
>
>
> however it is possible to call both clauses:
>
> iex(2)> X.foo(:a, :c)
> {:a, :b, :c}
> {:a, :b, :c}
> iex(3)> X.foo(:a, :z, :c)
> {:a, :z, :c}
> {:a, :z, :c}
>
>
> It would be more clear if Elixir could report the actual clauses that
> cannot be called.
>
> Thanks
> Mário Guimarães
>
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