feat: add support for builtin copy (#126)

_test/copy0.go

@@ -0,0 +1,14 @@
+package main
+
+import "fmt"
+
+func main() {
+	a := []int{10, 20, 30}
+	b := [4]int{}
+	c := b[:]
+	copy(c, a)
+	fmt.Println(c)
+}
+
+// Output:
+// [10 20 30 0]

interp/cfg.go

@@ -532,7 +532,7 @@ func (interp *Interpreter) Cfg(root *Node) ([]*Node, error) {
 					if n.typ = scope.getType(n.child[1].ident); n.typ == nil {
 						n.typ, err = nodeType(interp, scope, n.child[1])
 					}
-				case "cap", "len":
+				case "cap", "copy", "len":
 					n.typ = scope.getType("int")
 				case "make":
 					if n.typ = scope.getType(n.child[1].ident); n.typ == nil {
@@ -1088,7 +1088,20 @@ func (interp *Interpreter) Cfg(root *Node) ([]*Node, error) {
 				n.gen = nop
 			}
 
-		case SliceExpr, UnaryExpr:
+		case SliceExpr:
+			wireChild(n)
+			if ctyp := n.child[0].typ; ctyp.size != 0 {
+				// Create a slice type from an array type
+				n.typ = &Type{}
+				*n.typ = *ctyp
+				n.typ.size = 0
+				n.typ.rtype = nil
+			} else {
+				n.typ = ctyp
+			}
+			n.findex = scope.add(n.typ)
+
+		case UnaryExpr:
 			wireChild(n)
 			n.typ = n.child[0].typ
 			// TODO: Optimisation: avoid allocation if boolean branch op (i.e. '!' in an 'if' expr)

interp/interp.go

@@ -154,6 +154,7 @@ func initUniverse() *Scope {
 		"append":  &Symbol{kind: Bltn, builtin: _append},
 		"cap":     &Symbol{kind: Bltn, builtin: _cap},
 		"close":   &Symbol{kind: Bltn, builtin: _close},
+		"copy":    &Symbol{kind: Bltn, builtin: _copy},
 		"len":     &Symbol{kind: Bltn, builtin: _len},
 		"make":    &Symbol{kind: Bltn, builtin: _make},
 		"new":     &Symbol{kind: Bltn, builtin: _new},

interp/interp_test.go

@@ -1764,6 +1764,31 @@ func main() {
 	// world
 }
 
+func Example_copy0() {
+	src := `
+package main
+
+import "fmt"
+
+func main() {
+	a := []int{10, 20, 30}
+	b := [4]int{}
+	c := b[:]
+	copy(c, a)
+	fmt.Println(c)
+}
+`
+	i := interp.New(interp.Opt{Entry: "main"})
+	i.Use(stdlib.Value)
+	_, err := i.Eval(src)
+	if err != nil {
+		panic(err)
+	}
+
+	// Output:
+	// [10 20 30 0]
+}
+
 func Example_defer0() {
 	src := `
 package main

interp/run.go

@@ -1300,6 +1300,18 @@ func _cap(n *Node) {
 	}
 }
 
+func _copy(n *Node) {
+	i := n.findex
+	value0 := genValue(n.child[1])
+	value1 := genValue(n.child[2])
+	next := getExec(n.tnext)
+
+	n.exec = func(f *Frame) Builtin {
+		f.data[i].SetInt(int64(reflect.Copy(value0(f), value1(f))))
+		return next
+	}
+}
+
 func _close(n *Node) {
 	value := genValue(n.child[1])
 	next := getExec(n.tnext)