code: func (b *builtinDecimalAnyValueSig) evalDecimal(row chunk.Row) (*types.MyDecimal, bool, error) {
  	return b.args[0].EvalDecimal(b.ctx, row)
  }
docs: // evalDecimal evals a builtinDecimalAnyValueSig.
  // See https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_any-value