SparkSQL function require type Decimal

I designed the following function to work with arrays of any numeric type:

def array_sum[T](item:Traversable[T])(implicit n:Numeric[T]) = item.sum
// Registers a function as a UDF so it can be used in SQL statements.
sqlContext.udf.register("array_sumD", array_sum(_:Seq[Float]))

But wanting to pass an array of type float me the following error:

// Now we can use our function directly in SparkSQL.
sqlContext.sql("SELECT array_sumD(array(5.0,1.0,2.0)) as array_sum").show

Error:

 cannot resolve 'UDF(array(5.0,1.0,2.0))' due to data type mismatch: argument 1 requires array<double> type, however, 'array(5.0,1.0,2.0)' is of array<decimal(2,1)> type;