Represents a pattern match failure in a comp block.

When a <- binding in a comp block with an else clause fails to match, a %MatchFailed{} is thrown via Throw.throw/1. The else handler can then pattern match on the unmatched value to provide recovery.

Example

comp do
  {:ok, x} <- maybe_returns_error()
  return(x)
else
  {:error, reason} -> return({:failed, reason})
end

If maybe_returns_error() returns {:error, :not_found}, the pattern {:ok, x} fails to match, and %MatchFailed{value: {:error, :not_found}} is thrown. The else handler catches this and matches against the value.

Uncaught Match Failures

If a match failure is not handled by the else clause (no pattern matches), it propagates as %Comp.Throw{error: %MatchFailed{value: ...}}.