Function match_struct_fields 

pub fn match_struct_fields(
    input_dtype: &DataType,
    output_dtype: &DataType,
) -> DataType

Return input_dtype with its struct fields reordered and completed as in output_dtype, matched by name.

Matched fields keep their input_dtype dtype and missing fields get their output_dtype dtype. A struct with fields that are not in output_dtype is left as is. A non-strict cast to the result, followed by a strict cast to output_dtype, aligns struct fields by name while value conversions stay strict.