coerce(p1)
Returns an array with both a numeric and a big represented as Bignum objects.
This is achieved by converting numeric to a Bignum.
A TypeError is raised if the numeric is not a Fixnum or Bignum type.
(0x3FFFFFFFFFFFFFFF+1).coerce(42) #=> [42, 4611686018427387904]
static VALUE rb_big_coerce(VALUE x, VALUE y) { if (FIXNUM_P(y)) { y = rb_int2big(FIX2LONG(y)); } else if (!RB_BIGNUM_TYPE_P(y)) { rb_raise(rb_eTypeError, "can't coerce %s to Bignum", rb_obj_classname(y)); } return rb_assoc_new(y, x); }