fix: correct convert nil to type pointer (#166)

_test/type8.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+func main() {
+	v := (*time.Time)(nil)
+	fmt.Println(v)
+}
+
+// Output:
+// <nil>

interp/cfg.go

@@ -1075,10 +1075,10 @@ func (interp *Interpreter) Cfg(root *Node) ([]*Node, error) {
 			case n.anc.kind == Field:
 				// pointer type expression in a field expression (arg or struct field)
 				n.gen = nop
-			case n.anc.kind == ParenExpr && n.child[0].sym != nil && n.child[0].sym.kind == Typ:
+			case n.child[0].isType(scope):
 				// pointer type expression
 				n.gen = nop
-				n.typ = &Type{cat: PtrT, val: n.child[0].sym.typ}
+				n.typ = &Type{cat: PtrT, val: n.child[0].typ}
 			default:
 				// dereference expression
 				wireChild(n)

interp/run.go

@@ -171,15 +171,25 @@ func typeAssert2(n *Node) {
 
 func convert(n *Node) {
 	i := n.findex
-	var value func(*Frame) reflect.Value
-	if n.child[1].typ.cat == FuncT {
-		value = genNodeWrapper(n.child[1])
-	} else {
-		value = genValue(n.child[1])
-	}
+	c := n.child[1]
 	typ := n.child[0].typ.TypeOf()
 	next := getExec(n.tnext)
 
+	if c.kind == BasicLit && c.val == nil { // convert nil to type
+		n.exec = func(f *Frame) Builtin {
+			f.data[i] = reflect.New(typ).Elem()
+			return next
+		}
+		return
+	}
+
+	var value func(*Frame) reflect.Value
+	if c.typ.cat == FuncT {
+		value = genNodeWrapper(c)
+	} else {
+		value = genValue(c)
+	}
+
 	n.exec = func(f *Frame) Builtin {
 		f.data[i] = value(f).Convert(typ)
 		return next