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lib/dialyxir/warnings/pattern_match_covered.ex
defmodule Dialyxir.Warnings.PatternMatchCovered do
@moduledoc """
The pattern match has a later clause that will never be executed,
because a more general clause is higher in the matching order.
## Example
defmodule Example do
def ok() do
unmatched(:error)
end
defp unmatched(_), do: :ok
defp unmatched(:error), do: :error
end
"""
@behaviour Dialyxir.Warning
@impl Dialyxir.Warning
@spec warning() :: :pattern_match_cov
def warning(), do: :pattern_match_cov
@impl Dialyxir.Warning
@spec format_short([String.t()]) :: String.t()
def format_short([pattern, _]) do
"The pattern #{pattern} can never match the type, " <>
"because it is covered by previous clauses."
end
@impl Dialyxir.Warning
@spec format_long([String.t()]) :: String.t()
def format_long([pattern, type]) do
pretty_pattern = Erlex.pretty_print_pattern(pattern)
pretty_type = Erlex.pretty_print_type(type)
"""
The pattern
#{pretty_pattern}
can never match, because previous clauses completely cover the type
#{pretty_type}.
"""
end
@impl Dialyxir.Warning
@spec explain() :: String.t()
def explain() do
@moduledoc
end
end