fix: correct struct field name definition from imported type (#156)

_test/struct11.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+)
+
+type Fromage struct {
+	http.ResponseWriter
+}
+
+func main() {
+	a := Fromage{}
+	if a.ResponseWriter == nil {
+		fmt.Println("nil")
+	} else {
+		fmt.Println("not nil")
+	}
+}
+
+// Output:
+// nil

interp/type.go

@@ -341,7 +341,14 @@ func nodeType(interp *Interpreter, scope *Scope, n *Node) (*Type, error) {
 				if err != nil {
 					return nil, err
 				}
-				t.field = append(t.field, StructField{name: c.child[0].ident, embed: true, typ: typ})
+				name := c.child[0].ident
+				if name == "" && c.child[0].kind == SelectorExpr {
+					name = c.child[0].child[1].ident
+				}
+				if name == "" {
+					return nil, n.cfgError("empty field name")
+				}
+				t.field = append(t.field, StructField{name: name, embed: true, typ: typ})
 				t.incomplete = t.incomplete || typ.incomplete
 			} else {
 				l := len(c.child)