func NewBuilder(source string) *Builder {
	return &Builder{
		source:   source,
		jumpTo:   make(map[Label]int),
		jumpFrom: make(map[Label][]int),
	}
}
NewBuilder returns an empty Builder for the given source.
package code
type Label uint
type Builder struct {
	source    string           
	lines     []int32          
	code      []Opcode         
	jumpTo    map[Label]int    
	jumpFrom  map[Label][]int  
	constants []Constant       
}