fix: handle interface fields in literal composite structs

Struct fields of type interface must be converted in wrapper
values to be reachable by the runtime. Call genInterfaceWrapper
on such values.

Fixes #832.

_test/cli4.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/http/httptest"
+)
+
+type mw1 struct {
+	next http.Handler
+}
+
+func (m *mw1) ServeHTTP(rw http.ResponseWriter, rq *http.Request) {
+	m.next.ServeHTTP(rw, rq)
+}
+
+type mw0 struct{}
+
+func (m *mw0) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprint(w, "Welcome to my website!")
+}
+
+func main() {
+	m0 := &mw0{}
+	m1 := &mw1{m0}
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/", m1.ServeHTTP)
+
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	client(server.URL)
+}
+
+func client(uri string) {
+	resp, err := http.Get(uri)
+	if err != nil {
+		log.Fatal(err)
+	}
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println(string(body))
+}
+
+// Output:
+// Welcome to my website!

_test/cli5.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/http/httptest"
+)
+
+type mw1 struct {
+	next http.Handler
+}
+
+func (m *mw1) ServeHTTP(rw http.ResponseWriter, rq *http.Request) {
+	m.next.ServeHTTP(rw, rq)
+}
+
+type mw0 struct{}
+
+func (m *mw0) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprint(w, "Welcome to my website!")
+}
+
+func main() {
+	m0 := &mw0{}
+	m1 := &mw1{next: m0}
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/", m1.ServeHTTP)
+
+	server := httptest.NewServer(mux)
+	defer server.Close()
+
+	client(server.URL)
+}
+
+func client(uri string) {
+	resp, err := http.Get(uri)
+	if err != nil {
+		log.Fatal(err)
+	}
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println(string(body))
+}
+
+// Output:
+// Welcome to my website!

interp/run.go

@@ -2078,9 +2078,16 @@ func doCompositeLit(n *node, hasType bool) {
 	values := make([]func(*frame) reflect.Value, len(child))
 	for i, c := range child {
 		convertLiteralValue(c, typ.field[i].typ.TypeOf())
-		if c.typ.cat == funcT {
+		switch {
+		case c.typ.cat == funcT:
 			values[i] = genFunctionWrapper(c)
-		} else {
+		case isArray(c.typ) && c.typ.val != nil && c.typ.val.cat == interfaceT:
+			values[i] = genValueInterfaceArray(c)
+		case isRecursiveType(typ.field[i].typ, typ.field[i].typ.rtype):
+			values[i] = genValueRecursiveInterface(c, typ.field[i].typ.rtype)
+		case isInterface(typ.field[i].typ):
+			values[i] = genInterfaceWrapper(c, typ.field[i].typ.rtype)
+		default:
 			values[i] = genValue(c)
 		}
 	}
@@ -2134,6 +2141,8 @@ func doCompositeSparse(n *node, hasType bool) {
 			values[field] = genValueInterfaceArray(c1)
 		case isRecursiveType(typ.field[field].typ, typ.field[field].typ.rtype):
 			values[field] = genValueRecursiveInterface(c1, typ.field[field].typ.rtype)
+		case isInterface(typ.field[field].typ):
+			values[field] = genInterfaceWrapper(c1, typ.field[field].typ.rtype)
 		default:
 			values[field] = genValue(c1)
 		}