message: use indexable with length prop for Column.copyToArray
diff: @@ -151,15 +151,13 @@ namespace Column {
  return arrayColumn({ array: c.toArray({ array }), schema: c.schema, valueKind: c.valueKind });
  }
  - export function copyToArray<T>(c: Column<T>, array: ArrayLike<T>, offset = 0) {
  + export function copyToArray<T extends number>(c: Column<T>, array: { [k: number]: T, length: number }, offset = 0) {
  if (!c.isDefined) return;
  const cArray = c['@array']
  if (cArray) {
  - // TODO Index signature of 'ArrayLike<T>' only permits reading
  - for (let i = 0, _i = cArray.length; i < _i; i++) (array[offset + i] as any) = cArray[i];
  + for (let i = 0, _i = cArray.length; i < _i; i++) array[offset + i] = cArray[i];
  } else {
  - // TODO Index signature of 'ArrayLike<T>' only permits reading
  - for (let i = 0, _i = c.rowCount; i < _i; i++) (array[offset + i] as any) = c.value(i);
  + for (let i = 0, _i = c.rowCount; i < _i; i++) array[offset + i] = c.value(i);
  }
  }
  