Function patch_seq_variant_field_at 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn patch_seq_variant_field_at(
    stack: Stack,
) -> Stack

Get a field from a variant at the given index

Stack effect: ( Variant Int – Value )

Returns a clone of the field value at the specified index. Panics if index is out of bounds (this is a programming bug, not recoverable). Use variant.field-count to check bounds first if needed.

Safety

Stack must have a Variant and Int on top