interp: wrap source functions when used as input parameters.

It allows to use interpreter functions as parameters in the runtime, even for defered callbacks, or when passed as empty interfaces, as for runtime.SetFinalizer.

Fixes #1503

.github/workflows/go-cross.yml

@@ -17,7 +17,7 @@ jobs:
 
     strategy:
       matrix:
-        go-version: [ 1.16, 1.17 ]
+        go-version: [ 1.19, '1.20' ]
         os: [ubuntu-latest, macos-latest, windows-latest]
 
         include:
@@ -34,6 +34,7 @@ jobs:
         uses: actions/setup-go@v2
         with:
           go-version: ${{ matrix.go-version }}
+          stable: true
 
       # https://github.com/marketplace/actions/checkout
       - name: Checkout code
@@ -43,7 +44,7 @@ jobs:
 
       # https://github.com/marketplace/actions/cache
       - name: Cache Go modules
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           # In order:
           # * Module download cache

.github/workflows/main.yml

@@ -7,8 +7,8 @@ on:
   pull_request:
 
 env:
-  GO_VERSION: 1.17
-  GOLANGCI_LINT_VERSION: v1.42.1
+  GO_VERSION: 1.19
+  GOLANGCI_LINT_VERSION: v1.47.1
 
 jobs:
 
@@ -45,12 +45,13 @@ jobs:
     needs: linting
     strategy:
       matrix:
-        go-version: [ 1.16, 1.17 ]
+        go-version: [ 1.19, '1.20' ]
     steps:
       - name: Set up Go ${{ matrix.go-version }}
         uses: actions/setup-go@v2
         with:
           go-version: ${{ matrix.go-version }}
+          stable: true
 
       - name: Check out code
         uses: actions/checkout@v2
@@ -75,13 +76,14 @@ jobs:
         working-directory: ${{ github.workspace }}/go/src/github.com/traefik/yaegi
     strategy:
       matrix:
-        go-version: [ 1.16, 1.17 ]
+        go-version: [ 1.19, '1.20' ]
 
     steps:
       - name: Set up Go ${{ matrix.go-version }}
         uses: actions/setup-go@v2
         with:
           go-version: ${{ matrix.go-version }}
+          stable: true
 
       - name: Check out code
         uses: actions/checkout@v2
@@ -91,7 +93,7 @@ jobs:
 
       # https://github.com/marketplace/actions/cache
       - name: Cache Go modules
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: ./_test/tmp
           key: ${{ runner.os }}-yaegi-${{ hashFiles('**//_test/tmp/') }}

.github/workflows/release.yml

@@ -6,7 +6,7 @@ on:
       - v[0-9]+.[0-9]+*
 
 env:
-  GO_VERSION: 1.17
+  GO_VERSION: '1.20'
 
 jobs:
 
@@ -26,7 +26,7 @@ jobs:
           fetch-depth: 0
 
       - name: Cache Go modules
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: ~/go/pkg/mod
           key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}

.golangci.toml

@@ -27,6 +27,7 @@
     "scopelint", # deprecated
     "interfacer", # deprecated
     "maligned", # deprecated
+    "exhaustivestruct", # deprecated
     "lll",
     "gas",
     "dupl",
@@ -49,10 +50,15 @@
     "wrapcheck",
     "nestif",
     "exhaustive",
-    "exhaustivestruct",
+    "exhaustruct",
     "forbidigo",
     "ifshort",
     "forcetypeassert",
+    "varnamelen",
+    "nosnakecase",
+    "nonamedreturns",
+    "nilnil",
+    "maintidx",
     "errorlint", # TODO: must be reactivate before fixes
   ]
 
@@ -81,3 +87,6 @@
   [[issues.exclude-rules]]
     path = "interp/interp_eval_test.go"
     linters = ["thelper"]
+  [[issues.exclude-rules]]
+    path = "interp/debugger.go"
+    linters = ["containedctx"]

README.md

@@ -18,7 +18,7 @@ It powers executable Go scripts and plugins, in embedded interpreters or interac
 * Works everywhere Go works
 * All Go & runtime resources accessible from script (with control)
 * Security: `unsafe` and `syscall` packages neither used nor exported by default
-* Support Go 1.16 and Go 1.17 (the latest 2 major releases)
+* Support Go 1.18 and Go 1.19 (the latest 2 major releases)
 
 ## Install
 

_test/alias3/alias3.go

@@ -1,9 +0,0 @@
-package alias3
-
-type T struct {
-	A string
-}
-
-func (t *T) Print() {
-	println(t.A)
-}

_test/assert2.go

@@ -5,8 +5,8 @@ import (
 	"sync"
 )
 
-// Defined an interface of stringBuilder that compatible with
-// strings.Builder(go 1.10) and bytes.Buffer(< go 1.10)
+// Define an interface of stringBuilder that is compatible with
+// strings.Builder(go 1.10) and bytes.Buffer(< go 1.10).
 type stringBuilder interface {
 	WriteRune(r rune) (n int, err error)
 	WriteString(s string) (int, error)

_test/assign17.go

@@ -0,0 +1,21 @@
+package main
+
+func main() {
+	s := make([]map[string]string, 0)
+	m := make(map[string]string)
+	m["m1"] = "m1"
+	m["m2"] = "m2"
+	s = append(s, m)
+	tmpStr := "start"
+	println(tmpStr)
+	for _, v := range s {
+		tmpStr, ok := v["m1"]
+		println(tmpStr, ok)
+	}
+	println(tmpStr)
+}
+
+// Output:
+// start
+// m1 true
+// start

_test/assign18.go

@@ -0,0 +1,21 @@
+package main
+
+func main() {
+	s := make([]map[string]string, 0)
+	m := make(map[string]string)
+	m["m1"] = "m1"
+	m["m2"] = "m2"
+	s = append(s, m)
+	tmpStr := "start"
+	println(tmpStr)
+	for _, v := range s {
+		tmpStr, _ := v["m1"]
+		println(tmpStr)
+	}
+	println(tmpStr)
+}
+
+// Output:
+// start
+// m1
+// start

_test/break0.go

@@ -0,0 +1,24 @@
+package main
+
+func main() {
+	n := 2
+	m := 2
+	foo := true
+OuterLoop:
+	println("Boo")
+	for i := 0; i < n; i++ {
+		println("I: ", i)
+		for j := 0; j < m; j++ {
+			switch foo {
+			case true:
+				println(foo)
+				break OuterLoop
+			case false:
+				println(foo)
+			}
+		}
+	}
+}
+
+// Error:
+// 15:5: invalid break label OuterLoop

_test/break1.go

@@ -0,0 +1,24 @@
+package main
+
+func main() {
+	n := 2
+	m := 2
+	foo := true
+OuterLoop:
+	for i := 0; i < n; i++ {
+		println("I: ", i)
+		for j := 0; j < m; j++ {
+			switch foo {
+			case true:
+				println(foo)
+				break OuterLoop
+			case false:
+				println(foo)
+			}
+		}
+	}
+}
+
+// Output:
+// I:  0
+// true

_test/break2.go

@@ -0,0 +1,25 @@
+package main
+
+func main() {
+	n := 2
+	m := 2
+	foo := true
+OuterLoop:
+	for i := 0; i < n; i++ {
+		println("I: ", i)
+		for j := 0; j < m; j++ {
+			switch foo {
+			case true:
+				println(foo)
+				break OuterLoop
+			case false:
+				println(foo)
+				continue OuterLoop
+			}
+		}
+	}
+}
+
+// Output:
+// I:  0
+// true

_test/break3.go

@@ -0,0 +1,27 @@
+package main
+
+func main() {
+	n := 2
+	m := 2
+	foo := true
+	goto OuterLoop
+	println("Boo")
+OuterLoop:
+	for i := 0; i < n; i++ {
+		println("I: ", i)
+		for j := 0; j < m; j++ {
+			switch foo {
+			case true:
+				println(foo)
+				break OuterLoop
+			case false:
+				println(foo)
+				goto OuterLoop
+			}
+		}
+	}
+}
+
+// Output:
+// I:  0
+// true

_test/cli7.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"net/http/httptest"
+)
+
+type T struct {
+	http.ResponseWriter
+}
+
+type mw1 struct {
+}
+
+var obj = map[string]interface{}{}
+
+func (m *mw1) ServeHTTP(rw http.ResponseWriter, rq *http.Request) {
+	t := &T{
+		ResponseWriter: rw,
+	}
+	x := t.Header()
+	i := obj["m1"].(*mw1)
+	fmt.Fprint(rw, "Welcome to my website!", x, i)
+}
+
+func main() {
+	m1 := &mw1{}
+
+	obj["m1"] = m1
+
+	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 := io.ReadAll(resp.Body)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println(string(body))
+}
+
+// Output:
+// Welcome to my website!map[] &{}

_test/cli8.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"net/http"
+	"net/http/httptest"
+)
+
+type T struct {
+	name string
+	next http.Handler
+}
+
+func (t *T) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	println("in T.ServeHTTP")
+	if t.next != nil {
+		t.next.ServeHTTP(rw, req)
+	}
+}
+
+func New(name string, next http.Handler) (http.Handler, error) { return &T{name, next}, nil }
+
+func main() {
+	next := func(rw http.ResponseWriter, req *http.Request) {
+		println("in next")
+	}
+
+	t, err := New("test", http.HandlerFunc(next))
+	if err != nil {
+		panic(err)
+	}
+
+	recorder := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	t.ServeHTTP(recorder, req)
+	println(recorder.Result().Status)
+}
+
+// Output:
+// in T.ServeHTTP
+// in next
+// 200 OK

_test/cont2.go

@@ -0,0 +1,26 @@
+package main
+
+func main() {
+	n := 2
+	m := 2
+	foo := true
+OuterLoop:
+	for i := 0; i < n; i++ {
+		println("I: ", i)
+		for j := 0; j < m; j++ {
+			switch foo {
+			case true:
+				println(foo)
+				continue OuterLoop
+			case false:
+				println(foo)
+			}
+		}
+	}
+}
+
+// Output:
+// I:  0
+// true
+// I:  1
+// true

_test/cont3.go

@@ -0,0 +1,24 @@
+package main
+
+func main() {
+	n := 2
+	m := 2
+	foo := true
+OuterLoop:
+	println("boo")
+	for i := 0; i < n; i++ {
+		println("I: ", i)
+		for j := 0; j < m; j++ {
+			switch foo {
+			case true:
+				println(foo)
+				continue OuterLoop
+			case false:
+				println(foo)
+			}
+		}
+	}
+}
+
+// Error:
+// 15:5: invalid continue label OuterLoop

_test/convert3.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+)
+
+func main() {
+	next := func(rw http.ResponseWriter, req *http.Request) {
+		rw.Header().Set("Cache-Control", "max-age=20")
+		rw.WriteHeader(http.StatusOK)
+	}
+	f := http.HandlerFunc(next)
+	fmt.Printf("%T\n", f.ServeHTTP)
+}
+
+// Output:
+// func(http.ResponseWriter, *http.Request)

_test/fun28.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"runtime"
+)
+
+type T struct {
+	name string
+}
+
+func finalize(t *T) { println("finalize") }
+
+func newT() *T {
+	t := new(T)
+	runtime.SetFinalizer(t, finalize)
+	return t
+}
+
+func main() {
+	t := newT()
+	println(t != nil)
+}
+
+// Output:
+// true

_test/gen1.go

@@ -0,0 +1,39 @@
+package main
+
+import "fmt"
+
+// SumInts adds together the values of m.
+func SumInts(m map[string]int64) int64 {
+	var s int64
+	for _, v := range m {
+		s += v
+	}
+	return s
+}
+
+// SumFloats adds together the values of m.
+func SumFloats(m map[string]float64) float64 {
+	var s float64
+	for _, v := range m {
+		s += v
+	}
+	return s
+}
+
+func main() {
+	// Initialize a map for the integer values
+	ints := map[string]int64{
+		"first":  34,
+		"second": 12,
+	}
+
+	// Initialize a map for the float values
+	floats := map[string]float64{
+		"first":  35.98,
+		"second": 26.99,
+	}
+
+	fmt.Printf("Non-Generic Sums: %v and %v\n",
+		SumInts(ints),
+		SumFloats(floats))
+}

_test/gen10.go

@@ -0,0 +1,12 @@
+package main
+
+func genFunc() (f func()) {
+	return f
+}
+
+func main() {
+	println(genFunc() == nil)
+}
+
+// Output:
+// true

_test/gen11.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/netip"
+)
+
+type Slice[T any] struct {
+	x []T
+}
+
+type IPPrefixSlice struct {
+	x Slice[netip.Prefix]
+}
+
+func (v Slice[T]) MarshalJSON() ([]byte, error) { return json.Marshal(v.x) }
+
+// MarshalJSON implements json.Marshaler.
+func (v IPPrefixSlice) MarshalJSON() ([]byte, error) {
+	return v.x.MarshalJSON()
+}
+
+func main() {
+	t := IPPrefixSlice{}
+	fmt.Println(t)
+	b, e := t.MarshalJSON()
+	fmt.Println(string(b), e)
+}
+
+// Output:
+// {{[]}}
+// null <nil>

_test/gen12.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+)
+
+func MapOf[K comparable, V any](m map[K]V) Map[K, V] {
+	return Map[K, V]{m}
+}
+
+type Map[K comparable, V any] struct {
+	ж map[K]V
+}
+
+func (v MapView) Int() Map[string, int] { return MapOf(v.ж.Int) }
+
+type VMap struct {
+	Int map[string]int
+}
+
+type MapView struct {
+	ж *VMap
+}
+
+func main() {
+	mv := MapView{&VMap{}}
+	fmt.Println(mv.ж)
+}
+
+// Output:
+// &{map[]}

_test/gen13.go

@@ -0,0 +1,18 @@
+package main
+
+type Map[K comparable, V any] struct {
+	ж map[K]V
+}
+
+func (m Map[K, V]) Has(k K) bool {
+	_, ok := m.ж[k]
+	return ok
+}
+
+func main() {
+	m := Map[string, float64]{}
+	println(m.Has("test"))
+}
+
+// Output:
+// false

_test/gen2.go

@@ -0,0 +1,34 @@
+package main
+
+import "fmt"
+
+// SumIntsOrFloats sums the values of map m. It supports both int64 and float64
+// as types for map values.
+func SumIntsOrFloats[K comparable, V int64 | float64](m map[K]V) V {
+	var s V
+	for _, v := range m {
+		s += v
+	}
+	return s
+}
+
+func main() {
+	// Initialize a map for the integer values
+	ints := map[string]int64{
+		"first":  34,
+		"second": 12,
+	}
+
+	// Initialize a map for the float values
+	floats := map[string]float64{
+		"first":  35.98,
+		"second": 26.99,
+	}
+
+	fmt.Printf("Generic Sums: %v and %v\n",
+		SumIntsOrFloats[string, int64](ints),
+		SumIntsOrFloats[string, float64](floats))
+}
+
+// Output:
+// Generic Sums: 46 and 62.97

_test/gen3.go

@@ -0,0 +1,22 @@
+package main
+
+type Number interface {
+	int | int64 | ~float64
+}
+
+func Sum[T Number](numbers []T) T {
+	var total T
+	for _, x := range numbers {
+		total += x
+	}
+	return total
+}
+
+func main() {
+	xs := []int{3, 5, 10}
+	total := Sum(xs)
+	println(total)
+}
+
+// Output:
+// 18

_test/gen4.go

@@ -0,0 +1,42 @@
+package main
+
+import "fmt"
+
+type List[T any] struct {
+	head, tail *element[T]
+}
+
+// A recursive generic type.
+type element[T any] struct {
+	next *element[T]
+	val  T
+}
+
+func (lst *List[T]) Push(v T) {
+	if lst.tail == nil {
+		lst.head = &element[T]{val: v}
+		lst.tail = lst.head
+	} else {
+		lst.tail.next = &element[T]{val: v}
+		lst.tail = lst.tail.next
+	}
+}
+
+func (lst *List[T]) GetAll() []T {
+	var elems []T
+	for e := lst.head; e != nil; e = e.next {
+		elems = append(elems, e.val)
+	}
+	return elems
+}
+
+func main() {
+	lst := List[int]{}
+	lst.Push(10)
+	lst.Push(13)
+	lst.Push(23)
+	fmt.Println("list:", lst.GetAll())
+}
+
+// Output:
+// list: [10 13 23]

_test/gen5.go

@@ -0,0 +1,24 @@
+package main
+
+import "fmt"
+
+type Set[Elem comparable] struct {
+	m map[Elem]struct{}
+}
+
+func Make[Elem comparable]() Set[Elem] {
+	return Set[Elem]{m: make(map[Elem]struct{})}
+}
+
+func (s Set[Elem]) Add(v Elem) {
+	s.m[v] = struct{}{}
+}
+
+func main() {
+	s := Make[int]()
+	s.Add(1)
+	fmt.Println(s)
+}
+
+// Output:
+// {map[1:{}]}

_test/gen6.go

@@ -0,0 +1,19 @@
+package main
+
+func MapKeys[K comparable, V any](m map[K]V) []K {
+	r := make([]K, 0, len(m))
+	for k := range m {
+		r = append(r, k)
+	}
+	return r
+}
+
+func main() {
+	var m = map[int]string{1: "2", 2: "4", 4: "8"}
+
+	// Test type inference
+	println(len(MapKeys(m)))
+}
+
+// Output:
+// 3

_test/gen7.go

@@ -0,0 +1,19 @@
+package main
+
+func MapKeys[K comparable, V any](m map[K]V) []K {
+	r := make([]K, 0, len(m))
+	for k := range m {
+		r = append(r, k)
+	}
+	return r
+}
+
+func main() {
+	var m = map[int]string{1: "2", 2: "4", 4: "8"}
+
+	// Test type inference
+	println(len(MapKeys))
+}
+
+// Error:
+// invalid argument for len

_test/gen8.go

@@ -0,0 +1,15 @@
+package main
+
+type Float interface {
+	~float32 | ~float64
+}
+
+func add[T Float](a, b T) float64 { return float64(a) + float64(b) }
+
+func main() {
+	var x, y int = 1, 2
+	println(add(x, y))
+}
+
+// Error:
+// int does not implement main.Float

_test/gen9.go

@@ -0,0 +1,14 @@
+package main
+
+type Float interface {
+	~float32 | ~float64
+}
+
+func add[T Float](a, b T) float64 { return float64(a) + float64(b) }
+
+func main() {
+	println(add(1, 2))
+}
+
+// Error:
+// untyped int does not implement main.Float

_test/issue-1332.go

@@ -0,0 +1,17 @@
+package main
+
+func run(fn func(name string)) { fn("test") }
+
+type T2 struct {
+	name string
+}
+
+func (t *T2) f(s string) { println(s, t.name) }
+
+func main() {
+	t2 := &T2{"foo"}
+	run(t2.f)
+}
+
+// Output:
+// test foo

_test/issue-1337.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"io"
+	"os"
+)
+
+func f(i interface{}) {
+	switch at := i.(type) {
+	case int, int8:
+		println("integer", at)
+	case io.Reader:
+		println("reader")
+	}
+	println("bye")
+}
+
+func main() {
+	var fd *os.File
+	var r io.Reader = fd
+	f(r)
+}
+
+// Output:
+// reader
+// bye

_test/issue-1342.go

@@ -0,0 +1,12 @@
+package main
+
+import "fmt"
+
+func main() {
+	var a interface{}
+	a = "a"
+	fmt.Println(a, a == "a")
+}
+
+// Output:
+// a true

_test/issue-1344.go

@@ -0,0 +1,13 @@
+package main
+
+import "fmt"
+
+func main() {
+	var m = map[string]interface{}{"a": "a"}
+	a, _ := m["a"]
+	b, ok := a.(string)
+	fmt.Println("a:", a, ", b:", b, ", ok:", ok)
+}
+
+// Output:
+// a: a , b: a , ok: true

_test/issue-1354.go

@@ -0,0 +1,21 @@
+package main
+
+func main() {
+	println(test()) // Go prints true, Yaegi false
+}
+
+func test() bool {
+	if true {
+		goto label
+	}
+	goto label
+label:
+	println("Go continues here")
+	return true
+	println("Yaegi goes straight to this return (this line is never printed)")
+	return false
+}
+
+// Output:
+// Go continues here
+// true

_test/issue-1355.go

@@ -0,0 +1,22 @@
+package main
+
+import "github.com/traefik/yaegi/_test/p2"
+
+func f(i interface{}) {
+	_, ok := i.(p2.I)
+	println("ok:", ok)
+}
+
+func main() {
+	var v *p2.T
+	var i interface{}
+
+	i = v
+	_, ok := i.(p2.I)
+	println("ok:", ok)
+	f(v)
+}
+
+// Output:
+// ok: true
+// ok: true

_test/issue-1360.go

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

_test/issue-1361.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+type obj struct {
+	num float64
+}
+
+type Fun func(o *obj) (r *obj, err error)
+
+func numFun(fn func(f float64) float64) Fun {
+	return func(o *obj) (*obj, error) {
+		return &obj{fn(o.num)}, nil
+	}
+}
+
+func main() {
+	f := numFun(math.Cos)
+	r, err := f(&obj{})
+	fmt.Println(r, err)
+}
+
+// Output:
+// &{1} <nil>

_test/issue-1364.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+func main() {
+	var value interface{}
+	var err error
+	value, err = strconv.ParseFloat("123", 64)
+	fmt.Println(value, err)
+}
+
+// Output:
+// 123 <nil>

_test/issue-1365.go

@@ -0,0 +1,18 @@
+package main
+
+func genInt() (int, error) { return 3, nil }
+
+func getInt() (value int) {
+	value, err := genInt()
+	if err != nil {
+		panic(err)
+	}
+	return
+}
+
+func main() {
+	println(getInt())
+}
+
+// Output:
+// 3

_test/issue-1368.go

@@ -0,0 +1,16 @@
+package main
+
+const dollar byte = 36
+
+func main() {
+	var c byte = 36
+	switch true {
+	case c == dollar:
+		println("ok")
+	default:
+		println("not ok")
+	}
+}
+
+// Output:
+// ok

_test/issue-1371.go

@@ -0,0 +1,18 @@
+package main
+
+import "fmt"
+
+type node struct {
+	parent *node
+	child  []*node
+	key    string
+}
+
+func main() {
+	root := &node{key: "root"}
+	root.child = nil
+	fmt.Println("root:", root)
+}
+
+// Output:
+// root: &{<nil> [] root}

_test/issue-1373.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"fmt"
+	"go/ast"
+)
+
+func NewBadExpr() ast.Expr {
+	return &ast.BadExpr{}
+}
+
+func main() {
+	fmt.Printf("%T\n", NewBadExpr().(*ast.BadExpr))
+}
+
+// Output:
+// *ast.BadExpr

_test/issue-1375.go

@@ -0,0 +1,38 @@
+package main
+
+import "fmt"
+
+type Option func(*Struct)
+
+func WithOption(opt string) Option {
+	return func(s *Struct) {
+		s.opt = opt
+	}
+}
+
+type Struct struct {
+	opt string
+}
+
+func New(opts ...Option) *Struct {
+	s := new(Struct)
+	for _, opt := range opts {
+		opt(s)
+	}
+	return s
+}
+
+func (s *Struct) ShowOption() {
+	fmt.Println(s.opt)
+}
+
+func main() {
+	opts := []Option{
+		WithOption("test"),
+	}
+	s := New(opts...)
+	s.ShowOption()
+}
+
+// Output:
+// test

_test/issue-1378.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+func main() {
+	t, err := time.Parse(time.RFC3339, "2006-01-02T15:04:05Z")
+	if err != nil {
+		panic(err)
+	}
+	fn := func() error {
+		_, err := t.GobEncode()
+		return err
+	}
+	fmt.Println(fn())
+}
+
+// Output:
+// <nil>

_test/issue-1381.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+)
+
+func main() {
+	var bufPtrOne *bytes.Buffer
+	var bufPtrTwo *bytes.Buffer
+	var bufPtrThree *bytes.Buffer
+	var bufPtrFour *bytes.Buffer
+
+	for i := 0; i < 2; i++ {
+		bufOne := bytes.Buffer{}
+		bufTwo := &bytes.Buffer{}
+		var bufThree bytes.Buffer
+		bufFour := new(bytes.Buffer)
+
+		if bufPtrOne == nil {
+			bufPtrOne = &bufOne
+		} else if bufPtrOne == &bufOne {
+			fmt.Println("bufOne was not properly redeclared")
+		} else {
+			fmt.Println("bufOne is properly redeclared")
+		}
+
+		if bufPtrTwo == nil {
+			bufPtrTwo = bufTwo
+		} else if bufPtrTwo == bufTwo {
+			fmt.Println("bufTwo was not properly redeclared")
+		} else {
+			fmt.Println("bufTwo is properly redeclared")
+		}
+
+		if bufPtrThree == nil {
+			bufPtrThree = &bufThree
+		} else if bufPtrThree == &bufThree {
+			fmt.Println("bufThree was not properly redeclared")
+		} else {
+			fmt.Println("bufThree is properly redeclared")
+		}
+
+		if bufPtrFour == nil {
+			bufPtrFour = bufFour
+		} else if bufPtrFour == bufFour {
+			fmt.Println("bufFour was not properly redeclared")
+		} else {
+			fmt.Println("bufFour is properly redeclared")
+		}
+	}
+}
+
+// Output:
+// bufOne is properly redeclared
+// bufTwo is properly redeclared
+// bufThree is properly redeclared
+// bufFour is properly redeclared

_test/issue-1404.go

@@ -0,0 +1,22 @@
+package main
+
+type I interface {
+	inI()
+}
+
+type T struct {
+	name string
+}
+
+func (t *T) inI() {}
+
+func main() {
+	var i I = &T{name: "foo"}
+
+	if i, ok := i.(*T); ok {
+		println(i.name)
+	}
+}
+
+// Output:
+// foo

_test/issue-1408.go

@@ -0,0 +1,16 @@
+package main
+
+type (
+	Number  = int32
+	Number2 = Number
+)
+
+func f(n Number2) { println(n) }
+
+func main() {
+	var n Number = 5
+	f(n)
+}
+
+// Output:
+// 5

_test/issue-1411.go

@@ -0,0 +1,16 @@
+package main
+
+type Number int32
+
+func (n Number) IsValid() bool { return true }
+
+type Number1 = Number
+
+type Number2 = Number1
+
+func main() {
+	a := Number2(5)
+	println(a.IsValid())
+}
+
+// Output: true

_test/issue-1416.go

@@ -0,0 +1,17 @@
+package main
+
+type Number int32
+
+type Number1 = Number
+
+type Number2 = Number1
+
+func (n Number2) IsValid() bool { return true }
+
+func main() {
+	a := Number(5)
+	println(a.IsValid())
+}
+
+// Output:
+// true

_test/issue-1421.go

@@ -0,0 +1,9 @@
+package main
+
+type Number = int
+
+func main() {
+	println(Number(1) < int(2))
+}
+
+// Output: true

_test/issue-1425.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"io"
+	"log"
+	"os"
+	"strings"
+)
+
+type WrappedReader struct {
+	reader io.Reader
+}
+
+func (wr WrappedReader) Read(p []byte) (n int, err error) {
+	return wr.reader.Read(p)
+}
+
+// Of course, this implementation is completely stupid because it does not write
+// to the intended writer, as any honest WriteTo implementation should. its
+// implemtion is just to make obvious the divergence of behaviour with yaegi.
+func (wr WrappedReader) WriteTo(w io.Writer) (n int64, err error) {
+	// Ignore w, send to Stdout to prove whether this WriteTo is used.
+	data, err := io.ReadAll(wr)
+	if err != nil {
+		return 0, err
+	}
+	nn, err := os.Stdout.Write(data)
+	return int64(nn), err
+}
+
+func main() {
+	f := strings.NewReader("hello world")
+	wr := WrappedReader{reader: f}
+
+	// behind the scenes, io.Copy is supposed to use wr.WriteTo if the implementation exists.
+	// With Go, it works as expected, i.e. the output is sent to os.Stdout.
+	// With Yaegi, it doesn't, i.e. the output is sent to io.Discard.
+	if _, err := io.Copy(io.Discard, wr); err != nil {
+		log.Fatal(err)
+	}
+}
+
+// Output:
+// hello world

_test/issue-1439.go

@@ -0,0 +1,25 @@
+package main
+
+type Transformer interface {
+	Reset()
+}
+
+type Encoder struct {
+	Transformer
+}
+
+type nop struct{}
+
+func (nop) Reset() { println("Reset") }
+
+func f(e Transformer) {
+	e.Reset()
+}
+
+func main() {
+	e := Encoder{Transformer: nop{}}
+	f(e)
+}
+
+// Output:
+// Reset

_test/issue-1442.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"context"
+)
+
+func main() {
+	ctx, _ := context.WithCancel(context.Background())
+	ch := make(chan string, 20)
+	defer close(ch)
+
+	go func(ctx context.Context, ch <-chan string) {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case tmp := <-ch:
+				_ = tmp
+			}
+		}
+	}(ctx, ch)
+
+	for _, i := range "abcdef" {
+		for _, j := range "0123456789" {
+			// i, j := "a", "0"
+			for _, k := range "ABCDEF" {
+				select {
+				case <-ctx.Done():
+					return
+				default:
+					tmp := string(i) + string(j) + string(k)
+					ch <- tmp
+				}
+			}
+		}
+	}
+	return
+}
+
+// Output:
+//

_test/issue-1447.go

@@ -0,0 +1,20 @@
+package main
+
+import "fmt"
+
+type I interface {
+	Name() string
+}
+
+type S struct {
+	iMap map[string]I
+}
+
+func main() {
+	s := S{}
+	s.iMap = map[string]I{}
+	fmt.Println(s)
+}
+
+// Output:
+// {map[]}

_test/issue-1451.go

@@ -0,0 +1,19 @@
+package main
+
+type t1 uint8
+
+const (
+	n1 t1 = iota
+	n2
+)
+
+type T struct {
+	elem [n2 + 1]int
+}
+
+func main() {
+	println(len(T{}.elem))
+}
+
+// Output:
+// 2

_test/issue-1454.go

@@ -0,0 +1,22 @@
+package main
+
+type I2 interface {
+	I2() string
+}
+
+type I interface {
+	I2
+}
+
+type S struct{}
+
+func (*S) I2() string { return "foo" }
+
+func main() {
+	var i I
+	_, ok := i.(*S)
+	println(ok)
+}
+
+// Output:
+// false

_test/issue-1459.go

@@ -0,0 +1,22 @@
+package main
+
+import "fmt"
+
+type funclistItem func()
+
+type funclist struct {
+	list []funclistItem
+}
+
+func main() {
+	funcs := funclist{}
+
+	funcs.list = append(funcs.list, func() { fmt.Println("first") })
+
+	for _, f := range funcs.list {
+		f()
+	}
+}
+
+// Output:
+// first

_test/issue-1460.go

@@ -0,0 +1,84 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"net/netip"
+	"reflect"
+)
+
+func unmarshalJSON[T any](b []byte, x *[]T) error {
+	if *x != nil {
+		return errors.New("already initialized")
+	}
+	if len(b) == 0 {
+		return nil
+	}
+	return json.Unmarshal(b, x)
+}
+
+func SliceOfViews[T ViewCloner[T, V], V StructView[T]](x []T) SliceView[T, V] {
+	return SliceView[T, V]{x}
+}
+
+type StructView[T any] interface {
+	Valid() bool
+	AsStruct() T
+}
+
+type SliceView[T ViewCloner[T, V], V StructView[T]] struct {
+	ж []T
+}
+
+type ViewCloner[T any, V StructView[T]] interface {
+	View() V
+	Clone() T
+}
+
+func (v SliceView[T, V]) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+
+func (v *SliceView[T, V]) UnmarshalJSON(b []byte) error { return unmarshalJSON(b, &v.ж) }
+
+type Slice[T any] struct {
+	ж []T
+}
+
+func (v Slice[T]) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+
+func (v *Slice[T]) UnmarshalJSON(b []byte) error { return unmarshalJSON(b, &v.ж) }
+
+func SliceOf[T any](x []T) Slice[T] {
+	return Slice[T]{x}
+}
+
+type IPPrefixSlice struct {
+	ж Slice[netip.Prefix]
+}
+
+type viewStruct struct {
+	Int        int
+	Strings    Slice[string]
+	StringsPtr *Slice[string] `json:",omitempty"`
+}
+
+func main() {
+	ss := SliceOf([]string{"bar"})
+	in := viewStruct{
+		Int:        1234,
+		Strings:    ss,
+		StringsPtr: &ss,
+	}
+
+	var buf bytes.Buffer
+	encoder := json.NewEncoder(&buf)
+	encoder.SetIndent("", "")
+	err1 := encoder.Encode(&in)
+	b := buf.Bytes()
+	var got viewStruct
+	err2 := json.Unmarshal(b, &got)
+	println(err1 == nil, err2 == nil, reflect.DeepEqual(got, in))
+}
+
+// Output:
+// true true true

_test/issue-1465.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"fmt"
+)
+
+func SomeFunc[T int | string](defaultValue T) T {
+	switch v := any(&defaultValue).(type) {
+	case *string:
+		*v = *v + " abc"
+	case *int:
+		*v -= 234
+	}
+	return defaultValue
+}
+
+func main() {
+	fmt.Println(SomeFunc("test"))
+	fmt.Println(SomeFunc(1234))
+}
+
+// Output:
+// test abc
+// 1000

_test/issue-1466.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"fmt"
+)
+
+func SomeFunc(defaultValue interface{}) interface{} {
+	switch v := defaultValue.(type) {
+	case string:
+		return v + " abc"
+	case int:
+		return v - 234
+	}
+	panic("whoops")
+}
+
+func main() {
+	fmt.Println(SomeFunc(1234))
+	fmt.Println(SomeFunc("test"))
+}
+
+// Output:
+// 1000
+// test abc

_test/issue-1470.go

@@ -0,0 +1,15 @@
+package main
+
+type T struct {
+	num [tnum + 2]int
+}
+
+const tnum = 23
+
+func main() {
+	t := T{}
+	println(len(t.num))
+}
+
+// Output:
+// 25

_test/issue-1475.go

@@ -0,0 +1,12 @@
+package main
+
+type T uint16
+
+func f() T { return 0 }
+
+func main() {
+	println(f())
+}
+
+// Output:
+// 0

_test/issue-1488.go

@@ -0,0 +1,23 @@
+package main
+
+import "fmt"
+
+type vector interface {
+	[]int | [3]int
+}
+
+func sum[V vector](v V) (out int) {
+	for i := 0; i < len(v); i++ {
+		out += v[i]
+	}
+	return
+}
+
+func main() {
+	va := [3]int{1, 2, 3}
+	vs := []int{1, 2, 3}
+	fmt.Println(sum[[3]int](va), sum[[]int](vs))
+}
+
+// Output:
+// 6 6

_test/issue-435.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+type Foo int
+
+func (f Foo) String() string {
+	return "foo-" + strconv.Itoa(int(f))
+}
+
+func print1(arg interface{}) {
+	fmt.Println(arg)
+}
+
+func main() {
+	var arg Foo = 3
+	var f = print1
+	f(arg)
+}
+
+// Output:
+// foo-3

_test/named3.go

@@ -1,6 +1,6 @@
 package main
 
-import "github.com/traefik/yaegi/_test/alias3"
+import "github.com/traefik/yaegi/_test/named3"
 
 var globalT *T
 
@@ -8,10 +8,10 @@ func init() {
 	globalT = &T{A: "test"}
 }
 
-type T alias3.T
+type T named3.T
 
 func (t *T) PrintT() {
-	(*alias3.T)(t).Print()
+	(*named3.T)(t).Print()
 }
 
 func main() {

_test/named3/named3.go

@@ -0,0 +1,31 @@
+package named3
+
+import (
+	"fmt"
+	"net/http"
+)
+
+type T struct {
+	A string
+}
+
+func (t *T) Print() {
+	println(t.A)
+}
+
+type A http.Header
+
+func (a A) ForeachKey() error {
+	for k, vals := range a {
+		for _, v := range vals {
+			fmt.Println(k, v)
+		}
+
+	}
+
+	return nil
+}
+
+func (a A) Set(k string, v []string) {
+	a[k] = v
+}

_test/named4.go

@@ -17,11 +17,23 @@ func (b B) Test2() {
 	fmt.Println("test2")
 }
 
+func (b B) Test3() {
+	for k, vals := range b {
+		for _, v := range vals {
+			fmt.Println(k, v)
+		}
+	}
+}
+
 func main() {
 	b := B{}
 
 	b.Test2()
+	b["test"] = []string{"a", "b"}
+	b.Test3()
 }
 
 // Output:
 // test2
+// test a
+// test b

_test/p2/p2.go

@@ -0,0 +1,9 @@
+package p2
+
+type I interface {
+	isI()
+}
+
+type T struct{}
+
+func (t *T) isI() {}

_test/p4/p4.go

@@ -0,0 +1,3 @@
+package p4
+
+var Value1 = "value1"

_test/p5.go

@@ -0,0 +1,10 @@
+package main
+
+import "github.com/traefik/yaegi/_test/p5"
+
+func main() {
+	println(*p5.Value1)
+}
+
+// Output:
+// value1

_test/p5/p5.go

@@ -0,0 +1,8 @@
+package p5
+
+import "github.com/traefik/yaegi/_test/p4"
+
+var (
+	Value1 = &val1
+	val1   = p4.Value1
+)

_test/p6.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/traefik/yaegi/_test/p6"
+)
+
+func main() {
+	t := p6.IPPrefixSlice{}
+	fmt.Println(t)
+	b, e := t.MarshalJSON()
+	fmt.Println(string(b), e)
+}

_test/p6/p6.go

@@ -0,0 +1,21 @@
+package p6
+
+import (
+	"encoding/json"
+	"net/netip"
+)
+
+type Slice[T any] struct {
+	x []T
+}
+
+type IPPrefixSlice struct {
+	x Slice[netip.Prefix]
+}
+
+func (v Slice[T]) MarshalJSON() ([]byte, error) { return json.Marshal(v.x) }
+
+// MarshalJSON implements json.Marshaler.
+func (v IPPrefixSlice) MarshalJSON() ([]byte, error) {
+	return v.x.MarshalJSON()
+}

_test/select1.go

@@ -10,11 +10,11 @@ func main() {
 	c2 := make(chan string)
 
 	go func() {
-		time.Sleep(1e7)
+		time.Sleep(1e8)
 		c1 <- "one"
 	}()
 	go func() {
-		time.Sleep(2e7)
+		time.Sleep(2e8)
 		c2 <- "two"
 	}()
 

_test/select14.go

@@ -6,8 +6,8 @@ import (
 )
 
 const (
-	period    = 100 * time.Millisecond
-	precision = 7 * time.Millisecond
+	period    = 300 * time.Millisecond
+	precision = 30 * time.Millisecond
 )
 
 func main() {

_test/struct49.go

@@ -25,7 +25,7 @@ func main() {
 	}
 	s.ts["test"] = append(s.ts["test"], &T{s: s})
 
-	t , ok:= s.getT("test")
+	t, ok := s.getT("test")
 	println(t != nil, ok)
 }
 

_test/switch39.go

@@ -0,0 +1,17 @@
+package main
+
+func f(params ...interface{}) {
+	switch p0 := params[0].(type) {
+	case string:
+		println("string:", p0)
+	default:
+		println("not a string")
+	}
+}
+
+func main() {
+	f("Hello")
+}
+
+// Output:
+// string: Hello

_test/switch40.go

@@ -0,0 +1,17 @@
+package main
+
+func f(params ...interface{}) {
+	switch params[0].(type) {
+	case string:
+		println("a string")
+	default:
+		println("not a string")
+	}
+}
+
+func main() {
+	f("Hello")
+}
+
+// Output:
+// a string

_test/type24.go

@@ -43,6 +43,6 @@ func assertValue() {
 }
 
 // Output:
-// interface conversion: interface {} is int, not string
-// interface conversion: interface {} is nil, not string
-// interface conversion: *httptest.ResponseRecorder is not http.Pusher: missing method Push
+// 22:10: interface conversion: interface {} is int, not string
+// 32:10: interface conversion: interface {} is nil, not string
+// 42:10: interface conversion: *httptest.ResponseRecorder is not http.Pusher: missing method Push

_test/var16.go

@@ -0,0 +1,19 @@
+package main
+
+func getArray() ([]int, error) { println("getArray"); return []int{1, 2}, nil }
+
+func getNum() (int, error) { println("getNum"); return 3, nil }
+
+func main() {
+	if a, err := getNum(); err != nil {
+		println("#1", a)
+	} else if a, err := getArray(); err != nil {
+		println("#2", a)
+	}
+	println("#3")
+}
+
+// Output:
+// getNum
+// getArray
+// #3

example/fs/fs_test.go

@@ -2,9 +2,7 @@ package fs1
 
 import (
 	"testing"
-
-	// only available from 1.16.
-	"testing/fstest"
+	"testing/fstest" // only available from 1.16.
 
 	"github.com/traefik/yaegi/interp"
 	"github.com/traefik/yaegi/stdlib"

extract/extract.go

@@ -194,6 +194,11 @@ func (e *Extractor) genContent(importPath string, p *types.Package) ([]byte, err
 		case *types.Var:
 			val[name] = Val{pname, true}
 		case *types.TypeName:
+			// Skip type if it is generic.
+			if t, ok := o.Type().(*types.Named); ok && t.TypeParams().Len() > 0 {
+				continue
+			}
+
 			typ[name] = pname
 			if t, ok := o.Type().Underlying().(*types.Interface); ok {
 				var methods []Method
@@ -463,7 +468,7 @@ func GetMinor(part string) string {
 	return minor
 }
 
-const defaultMinorVersion = 17
+const defaultMinorVersion = 20
 
 func genBuildTags() (string, error) {
 	version := runtime.Version()

generate.go

@@ -1,3 +1,4 @@
+// Package yaegi provides a Go interpreter.
 package yaegi
 
 //go:generate go generate github.com/traefik/yaegi/internal/cmd/extract

go.mod

@@ -1,3 +1,3 @@
 module github.com/traefik/yaegi
 
-go 1.16
+go 1.18

internal/cmd/extract/extract.go

@@ -11,7 +11,7 @@ Output files are written in the current directory, and prefixed with the go vers
 
 Usage:
 
-    extract package...
+	extract package...
 
 The same program is used for all target operating systems and architectures.
 The GOOS and GOARCH environment variables set the desired target.

internal/cmd/genop/genop.go

@@ -535,10 +535,11 @@ func {{$name}}(n *node) {
 	typ := n.typ.concrete().TypeOf()
 	isInterface := n.typ.TypeOf().Kind() == reflect.Interface
 	c0, c1 := n.child[0], n.child[1]
+	t0, t1 := c0.typ.TypeOf(), c1.typ.TypeOf()
 
 	{{- if or (eq $op.Name "==") (eq $op.Name "!=") }}
 
-	if c0.typ.cat == aliasT || c1.typ.cat == aliasT {
+	if c0.typ.cat == linkedT || c1.typ.cat == linkedT {
 		switch {
 		case isInterface:
 			v0 := genValue(c0)
@@ -621,9 +622,39 @@ func {{$name}}(n *node) {
 		}
 		return
 	}
+
+	// Do not attempt to optimize '==' or '!=' if an operand is an interface.
+	// This will preserve proper dynamic type checking at runtime. For static types,
+	// type checks are already performed, so bypass them if possible.
+	if t0.Kind() == reflect.Interface || t1.Kind() == reflect.Interface {
+		v0 := genValue(c0)
+		v1 := genValue(c1)
+		if n.fnext != nil {
+			fnext := getExec(n.fnext)
+			n.exec = func(f *frame) bltn {
+				i0 := v0(f).Interface()
+				i1 := v1(f).Interface()
+				if i0 {{$op.Name}} i1 {
+					dest(f).SetBool(true)
+					return tnext
+				}
+				dest(f).SetBool(false)
+				return fnext
+			}
+		} else {
+			dest := genValue(n)
+			n.exec = func(f *frame) bltn {
+				i0 := v0(f).Interface()
+				i1 := v1(f).Interface()
+				dest(f).SetBool(i0 {{$op.Name}} i1)
+				return tnext
+			}
+		}
+		return
+	}
 	{{- end}}
 
-	switch t0, t1 := c0.typ.TypeOf(), c1.typ.TypeOf(); {
+	switch {
 	case isString(t0) || isString(t1):
 		switch {
 		case isInterface:

internal/unsafe2/unsafe.go

@@ -1,3 +1,4 @@
+// Package unsafe2 provides helpers to generate recursive struct types.
 package unsafe2
 
 import (

interp/ast.go

@@ -72,6 +72,7 @@ const (
 	importSpec
 	incDecStmt
 	indexExpr
+	indexListExpr
 	interfaceType
 	keyValueExpr
 	labeledStmt
@@ -155,6 +156,7 @@ var kinds = [...]string{
 	importSpec:        "importSpec",
 	incDecStmt:        "incDecStmt",
 	indexExpr:         "indexExpr",
+	indexListExpr:     "indexListExpr",
 	interfaceType:     "interfaceType",
 	keyValueExpr:      "keyValueExpr",
 	labeledStmt:       "labeledStmt",
@@ -282,6 +284,7 @@ var actions = [...]string{
 	aDec:          "--",
 	aEqual:        "==",
 	aGreater:      ">",
+	aGreaterEqual: ">=",
 	aGetFunc:      "getFunc",
 	aGetIndex:     "getIndex",
 	aGetMethod:    "getMethod",
@@ -290,6 +293,7 @@ var actions = [...]string{
 	aLand:         "&&",
 	aLor:          "||",
 	aLower:        "<",
+	aLowerEqual:   "<=",
 	aMethod:       "Method",
 	aMul:          "*",
 	aMulAssign:    "*=",
@@ -692,7 +696,7 @@ func (interp *Interpreter) ast(f ast.Node) (string, *node, error) {
 			n := addChild(&root, anc, pos, funcDecl, aNop)
 			n.val = n
 			if a.Recv == nil {
-				// function is not a method, create an empty receiver list
+				// Function is not a method, create an empty receiver list.
 				addChild(&root, astNode{n, nod}, pos, fieldList, aNop)
 			}
 			st.push(n, nod)
@@ -704,7 +708,13 @@ func (interp *Interpreter) ast(f ast.Node) (string, *node, error) {
 			st.push(n, nod)
 
 		case *ast.FuncType:
-			st.push(addChild(&root, anc, pos, funcType, aNop), nod)
+			n := addChild(&root, anc, pos, funcType, aNop)
+			n.val = n
+			if a.TypeParams == nil {
+				// Function has no type parameters, create an empty fied list.
+				addChild(&root, astNode{n, nod}, pos, fieldList, aNop)
+			}
+			st.push(n, nod)
 
 		case *ast.GenDecl:
 			var kind nkind
@@ -774,6 +784,9 @@ func (interp *Interpreter) ast(f ast.Node) (string, *node, error) {
 		case *ast.IndexExpr:
 			st.push(addChild(&root, anc, pos, indexExpr, aGetIndex), nod)
 
+		case *ast.IndexListExpr:
+			st.push(addChild(&root, anc, pos, indexListExpr, aNop), nod)
+
 		case *ast.InterfaceType:
 			st.push(addChild(&root, anc, pos, interfaceType, aNop), nod)
 

interp/build.go

@@ -147,10 +147,22 @@ func skipFile(ctx *build.Context, p string, skipTest bool) bool {
 	}
 	a := strings.Split(p[i+1:], "_")
 	last := len(a) - 1
-	if last1 := last - 1; last1 >= 0 && a[last1] == ctx.GOOS && a[last] == ctx.GOARCH {
-		return false
+	if last-1 >= 0 {
+		switch x, y := a[last-1], a[last]; {
+		case x == ctx.GOOS:
+			if knownArch[y] {
+				return y != ctx.GOARCH
+			}
+			return false
+		case knownOs[x] && knownArch[y]:
+			return true
+		case knownArch[y] && y != ctx.GOARCH:
+			return true
+		default:
+			return false
+		}
 	}
-	if s := a[last]; s != ctx.GOOS && s != ctx.GOARCH && knownOs[s] || knownArch[s] {
+	if x := a[last]; knownOs[x] && x != ctx.GOOS || knownArch[x] && x != ctx.GOARCH {
 		return true
 	}
 	return false

interp/build_test.go

@@ -51,7 +51,7 @@ func TestBuildTag(t *testing.T) {
 	}
 }
 
-func TestBuildFile(t *testing.T) {
+func TestSkipFile(t *testing.T) {
 	// Assume a specific OS, arch and go pattern no matter the real underlying system
 	ctx := build.Context{
 		GOARCH: "amd64",
@@ -65,10 +65,18 @@ func TestBuildFile(t *testing.T) {
 		{"bar_linux.go", false},
 		{"bar_maix.go", false},
 		{"bar_mlinux.go", false},
+
 		{"bar_aix_foo.go", false},
+		{"bar_linux_foo.go", false},
+		{"bar_foo_amd64.go", false},
+		{"bar_foo_arm.go", true},
+
 		{"bar_aix_s390x.go", true},
 		{"bar_aix_amd64.go", true},
 		{"bar_linux_arm.go", true},
+
+		{"bar_amd64.go", false},
+		{"bar_arm.go", true},
 	}
 
 	for _, test := range tests {

interp/cfg.go

@@ -145,8 +145,11 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					}
 
 					switch o.typ.cat {
-					case valueT:
+					case valueT, linkedT:
 						typ := o.typ.rtype
+						if o.typ.cat == linkedT {
+							typ = o.typ.val.TypeOf()
+						}
 						switch typ.Kind() {
 						case reflect.Map:
 							n.anc.gen = rangeMap
@@ -202,38 +205,50 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					}
 				}
 			}
+
 			n.findex = -1
 			n.val = nil
 			sc = sc.pushBloc()
-
-		case breakStmt, continueStmt, gotoStmt:
-			if len(n.child) > 0 {
-				// Handle labeled statements.
-				label := n.child[0].ident
-				if sym, _, ok := sc.lookup(label); ok {
-					if sym.kind != labelSym {
-						err = n.child[0].cfgErrorf("label %s not defined", label)
-						break
-					}
-					sym.from = append(sym.from, n)
-					n.sym = sym
-				} else {
-					n.sym = &symbol{kind: labelSym, from: []*node{n}, index: -1}
-					sc.sym[label] = n.sym
+			// Pre-define symbols for labels defined in this block, so we are sure that
+			// they are already defined when met.
+			// TODO(marc): labels must be stored outside of symbols to avoid collisions.
+			for _, c := range n.child {
+				if c.kind != labeledStmt {
+					continue
+				}
+				label := c.child[0].ident
+				sym := &symbol{kind: labelSym, node: c, index: -1}
+				sc.sym[label] = sym
+				c.sym = sym
+			}
+			// If block is the body of a function, get declared variables in current scope.
+			// This is done in order to add the func signature symbols into sc.sym,
+			// as we will need them in post-processing.
+			if n.anc != nil && n.anc.kind == funcDecl {
+				for k, v := range sc.anc.sym {
+					sc.sym[k] = v
 				}
 			}
 
-		case labeledStmt:
+		case breakStmt, continueStmt, gotoStmt:
+			if len(n.child) == 0 {
+				break
+			}
+			// Handle labeled statements.
 			label := n.child[0].ident
-			// TODO(marc): labels must be stored outside of symbols to avoid collisions
-			// Used labels are searched in current and sub scopes, not upper ones.
-			if sym, ok := sc.lookdown(label); ok {
-				sym.node = n
+			if sym, _, ok := sc.lookup(label); ok {
+				if sym.kind != labelSym {
+					err = n.child[0].cfgErrorf("label %s not defined", label)
+					break
+				}
 				n.sym = sym
 			} else {
-				n.sym = &symbol{kind: labelSym, node: n, index: -1}
+				n.sym = &symbol{kind: labelSym, index: -1}
+				sc.sym[label] = n.sym
+			}
+			if n.kind == gotoStmt {
+				n.sym.from = append(n.sym.from, n) // To allow forward goto statements.
 			}
-			sc.sym[label] = n.sym
 
 		case caseClause:
 			sc = sc.pushBloc()
@@ -296,7 +311,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				// Indicate that the first child is the type.
 				n.nleft = 1
 			} else {
-				// Get type from ancestor (implicit type)
+				// Get type from ancestor (implicit type).
 				if n.anc.kind == keyValueExpr && n == n.anc.child[0] {
 					n.typ = n.anc.typ.key
 				} else if atyp := n.anc.typ; atyp != nil {
@@ -307,8 +322,60 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					}
 				}
 				if n.typ == nil {
-					err = n.cfgErrorf("undefined type")
-					return false
+					// A nil type indicates either an error or a generic type.
+					// A child indexExpr or indexListExpr is used for type parameters,
+					// it indicates an instanciated generic.
+					if n.child[0].kind != indexExpr && n.child[0].kind != indexListExpr {
+						err = n.cfgErrorf("undefined type")
+						return false
+					}
+					t0, err1 := nodeType(interp, sc, n.child[0].child[0])
+					if err1 != nil {
+						return false
+					}
+					if t0.cat != genericT {
+						err = n.cfgErrorf("undefined type")
+						return false
+					}
+					// We have a composite literal of generic type, instantiate it.
+					lt := []*itype{}
+					for _, n1 := range n.child[0].child[1:] {
+						t1, err1 := nodeType(interp, sc, n1)
+						if err1 != nil {
+							return false
+						}
+						lt = append(lt, t1)
+					}
+					var g *node
+					g, _, err = genAST(sc, t0.node.anc, lt)
+					if err != nil {
+						return false
+					}
+					n.child[0] = g.lastChild()
+					n.typ, err = nodeType(interp, sc, n.child[0])
+					if err != nil {
+						return false
+					}
+					// Generate methods if any.
+					for _, nod := range t0.method {
+						gm, _, err2 := genAST(nod.scope, nod, lt)
+						if err2 != nil {
+							err = err2
+							return false
+						}
+						gm.typ, err = nodeType(interp, nod.scope, gm.child[2])
+						if err != nil {
+							return false
+						}
+						if _, err = interp.cfg(gm, sc, sc.pkgID, sc.pkgName); err != nil {
+							return false
+						}
+						if err = genRun(gm); err != nil {
+							return false
+						}
+						n.typ.addMethod(gm)
+					}
+					n.nleft = 1 // Indictate the type of composite literal.
 				}
 			}
 
@@ -319,6 +386,10 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			}
 			// Propagate type to children, to handle implicit types
 			for _, c := range child {
+				if isBlank(c) {
+					err = n.cfgErrorf("cannot use _ as value")
+					return false
+				}
 				switch c.kind {
 				case binaryExpr, unaryExpr, compositeLitExpr:
 					// Do not attempt to propagate composite type to operator expressions,
@@ -349,16 +420,55 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			fallthrough
 
 		case funcDecl:
+			// Do not allow function declarations without body.
+			if len(n.child) < 4 {
+				err = n.cfgErrorf("function declaration without body is unsupported (linkname or assembly can not be interpreted).")
+				return false
+			}
 			n.val = n
+
+			// Skip substree in case of a generic function.
+			if len(n.child[2].child[0].child) > 0 {
+				return false
+			}
+
+			// Skip subtree if the function is a method with a generic receiver.
+			if len(n.child[0].child) > 0 {
+				recvTypeNode := n.child[0].child[0].lastChild()
+				typ, err := nodeType(interp, sc, recvTypeNode)
+				if err != nil {
+					return false
+				}
+				if typ.cat == genericT || (typ.val != nil && typ.val.cat == genericT) {
+					return false
+				}
+				if typ.cat == ptrT {
+					rc0 := recvTypeNode.child[0]
+					rt0, err := nodeType(interp, sc, rc0)
+					if err != nil {
+						return false
+					}
+					if rc0.kind == indexExpr && rt0.cat == structT {
+						return false
+					}
+				}
+			}
+
 			// Compute function type before entering local scope to avoid
 			// possible collisions with function argument names.
 			n.child[2].typ, err = nodeType(interp, sc, n.child[2])
-			// Add a frame indirection level as we enter in a func
+			if err != nil {
+				return false
+			}
+			n.typ = n.child[2].typ
+
+			// Add a frame indirection level as we enter in a func.
 			sc = sc.pushFunc()
 			sc.def = n
-			if len(n.child[2].child) == 2 {
-				// Allocate frame space for return values, define output symbols
-				for _, c := range n.child[2].child[1].child {
+
+			// Allocate frame space for return values, define output symbols.
+			if len(n.child[2].child) == 3 {
+				for _, c := range n.child[2].child[2].child {
 					var typ *itype
 					if typ, err = nodeType(interp, sc, c.lastChild()); err != nil {
 						return false
@@ -372,14 +482,28 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					}
 				}
 			}
+
+			// Define receiver symbol.
 			if len(n.child[0].child) > 0 {
-				// define receiver symbol
 				var typ *itype
 				fr := n.child[0].child[0]
 				recvTypeNode := fr.lastChild()
 				if typ, err = nodeType(interp, sc, recvTypeNode); err != nil {
 					return false
 				}
+				if typ.cat == nilT {
+					// This may happen when instantiating generic methods.
+					s2, _, ok := sc.lookup(typ.id())
+					if !ok {
+						err = n.cfgErrorf("type not found: %s", typ.id())
+						break
+					}
+					typ = s2.typ
+					if typ.cat == nilT {
+						err = n.cfgErrorf("nil type: %s", typ.id())
+						break
+					}
+				}
 				recvTypeNode.typ = typ
 				n.child[2].typ.recv = typ
 				n.typ.recv = typ
@@ -388,8 +512,9 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					sc.sym[fr.child[0].ident] = &symbol{index: index, kind: varSym, typ: typ}
 				}
 			}
-			for _, c := range n.child[2].child[0].child {
-				// define input parameter symbols
+
+			// Define input parameter symbols.
+			for _, c := range n.child[2].child[1].child {
 				var typ *itype
 				if typ, err = nodeType(interp, sc, c.lastChild()); err != nil {
 					return false
@@ -398,6 +523,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					sc.sym[cc.ident] = &symbol{index: sc.add(typ), kind: varSym, typ: typ}
 				}
 			}
+
 			if n.child[1].ident == "init" && len(n.child[0].child) == 0 {
 				initNodes = append(initNodes, n)
 			}
@@ -478,6 +604,10 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 
 		switch n.kind {
 		case addressExpr:
+			if isBlank(n.child[0]) {
+				err = n.cfgErrorf("cannot use _ as value")
+				break
+			}
 			wireChild(n)
 
 			err = check.addressExpr(n)
@@ -513,6 +643,15 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				updateSym := false
 				var sym *symbol
 				var level int
+
+				if dest.rval.IsValid() && isConstType(dest.typ) {
+					err = n.cfgErrorf("cannot assign to %s (%s constant)", dest.rval, dest.typ.str)
+					break
+				}
+				if isBlank(src) {
+					err = n.cfgErrorf("cannot use _ as value")
+					break
+				}
 				if n.kind == defineStmt || (n.kind == assignStmt && dest.ident == "_") {
 					if atyp != nil {
 						dest.typ = atyp
@@ -609,7 +748,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					n.gen = nop
 					src.findex = dest.findex
 					src.level = level
-				case len(n.child) < 4 && isArithmeticAction(src):
+				case len(n.child) < 4 && isArithmeticAction(src) && !isInterface(dest.typ):
 					// Optimize single assignments from some arithmetic operations.
 					src.typ = dest.typ
 					src.findex = dest.findex
@@ -645,6 +784,10 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			}
 
 		case incDecStmt:
+			err = check.unaryExpr(n)
+			if err != nil {
+				break
+			}
 			wireChild(n)
 			n.findex = n.child[0].findex
 			n.level = n.child[0].level
@@ -754,24 +897,23 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			case n.anc.kind == returnStmt:
 				// To avoid a copy in frame, if the result is to be returned, store it directly
 				// at the frame location reserved for output arguments.
-				pos := childPos(n)
-				n.typ = sc.def.typ.ret[pos]
-				n.findex = pos
+				n.findex = childPos(n)
 			default:
 				// Allocate a new location in frame, and store the result here.
 				n.findex = sc.add(n.typ)
 			}
 
 		case indexExpr:
+			if isBlank(n.child[0]) {
+				err = n.cfgErrorf("cannot use _ as value")
+				break
+			}
 			wireChild(n)
 			t := n.child[0].typ
+			for t.cat == linkedT {
+				t = t.val
+			}
 			switch t.cat {
-			case aliasT:
-				if isString(t.val.TypeOf()) {
-					n.typ = sc.getType("byte")
-					break
-				}
-				fallthrough
 			case ptrT:
 				n.typ = t.val
 				if t.val.cat == valueT {
@@ -787,6 +929,51 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				} else {
 					n.typ = valueTOf(t.rtype.Elem())
 				}
+			case funcT:
+				// A function indexed by a type means an instantiated generic function.
+				c1 := n.child[1]
+				if !c1.isType(sc) {
+					n.typ = t
+					return
+				}
+				g, found, err := genAST(sc, t.node.anc, []*itype{c1.typ})
+				if err != nil {
+					return
+				}
+				if !found {
+					if _, err = interp.cfg(g, t.node.anc.scope, importPath, pkgName); err != nil {
+						return
+					}
+					// Generate closures for function body.
+					if err = genRun(g.child[3]); err != nil {
+						return
+					}
+				}
+				// Replace generic func node by instantiated one.
+				n.anc.child[childPos(n)] = g
+				n.typ = g.typ
+				return
+			case genericT:
+				name := t.id() + "[" + n.child[1].typ.id() + "]"
+				sym, _, ok := sc.lookup(name)
+				if !ok {
+					err = n.cfgErrorf("type not found: %s", name)
+					return
+				}
+				n.gen = nop
+				n.typ = sym.typ
+				return
+			case structT:
+				// A struct indexed by a Type means an instantiated generic struct.
+				name := t.name + "[" + n.child[1].ident + "]"
+				sym, _, ok := sc.lookup(name)
+				if ok {
+					n.typ = sym.typ
+					n.findex = sc.add(n.typ)
+					n.gen = nop
+					return
+				}
+
 			default:
 				n.typ = t.val
 			}
@@ -842,7 +1029,14 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			}
 			wireChild(n)
 
-		case declStmt, exprStmt, sendStmt:
+		case sendStmt:
+			if !isChan(n.child[0].typ) {
+				err = n.cfgErrorf("invalid operation: cannot send to non-channel %s", n.child[0].typ.id())
+				break
+			}
+			fallthrough
+
+		case declStmt, exprStmt:
 			wireChild(n)
 			l := n.lastChild()
 			n.findex = l.findex
@@ -853,34 +1047,94 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			n.rval = l.rval
 
 		case breakStmt:
-			if len(n.child) > 0 {
-				gotoLabel(n.sym)
-			} else {
+			if len(n.child) == 0 {
 				n.tnext = sc.loop
+				break
 			}
+			if !n.hasAnc(n.sym.node) {
+				err = n.cfgErrorf("invalid break label %s", n.child[0].ident)
+				break
+			}
+			n.tnext = n.sym.node
 
 		case continueStmt:
-			if len(n.child) > 0 {
-				gotoLabel(n.sym)
-			} else {
+			if len(n.child) == 0 {
 				n.tnext = sc.loopRestart
+				break
 			}
+			if !n.hasAnc(n.sym.node) {
+				err = n.cfgErrorf("invalid continue label %s", n.child[0].ident)
+				break
+			}
+			n.tnext = n.sym.node.child[1].lastChild().start
 
 		case gotoStmt:
-			gotoLabel(n.sym)
+			if n.sym.node == nil {
+				// It can be only due to a forward goto, to be resolved at labeledStmt.
+				// Invalid goto labels are catched at AST parsing.
+				break
+			}
+			n.tnext = n.sym.node.start
 
 		case labeledStmt:
 			wireChild(n)
 			if len(n.child) > 1 {
 				n.start = n.child[1].start
 			}
-			gotoLabel(n.sym)
+			for _, c := range n.sym.from {
+				c.tnext = n.start // Resolve forward goto.
+			}
 
 		case callExpr:
+			for _, c := range n.child {
+				if isBlank(c) {
+					err = n.cfgErrorf("cannot use _ as value")
+					return
+				}
+			}
 			wireChild(n)
-			switch {
+			switch c0 := n.child[0]; {
+			case c0.kind == indexListExpr:
+				// Instantiate a generic function then call it.
+				fun := c0.child[0].sym.node
+				lt := []*itype{}
+				for _, c := range c0.child[1:] {
+					lt = append(lt, c.typ)
+				}
+				g, found, err := genAST(sc, fun, lt)
+				if err != nil {
+					return
+				}
+				if !found {
+					_, err = interp.cfg(g, fun.scope, importPath, pkgName)
+					if err != nil {
+						return
+					}
+					err = genRun(g.child[3]) // Generate closures for function body.
+					if err != nil {
+						return
+					}
+				}
+				n.child[0] = g
+				c0 = n.child[0]
+				wireChild(n)
+				if typ := c0.typ; len(typ.ret) > 0 {
+					n.typ = typ.ret[0]
+					if n.anc.kind == returnStmt && n.typ.id() == sc.def.typ.ret[0].id() {
+						// Store the result directly to the return value area of frame.
+						// It can be done only if no type conversion at return is involved.
+						n.findex = childPos(n)
+					} else {
+						n.findex = sc.add(n.typ)
+						for _, t := range typ.ret[1:] {
+							sc.add(t)
+						}
+					}
+				} else {
+					n.findex = notInFrame
+				}
+
 			case isBuiltinCall(n, sc):
-				c0 := n.child[0]
 				bname := c0.ident
 				err = check.builtin(bname, n, n.child[1:], n.action == aCallSlice)
 				if err != nil {
@@ -888,7 +1142,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				}
 
 				n.gen = c0.sym.builtin
-				c0.typ = &itype{cat: builtinT}
+				c0.typ = &itype{cat: builtinT, name: bname}
 				if n.typ, err = nodeType(interp, sc, n); err != nil {
 					return
 				}
@@ -931,9 +1185,10 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				if op, ok := constBltn[bname]; ok && n.anc.action != aAssign {
 					op(n) // pre-compute non-assigned constant :
 				}
-			case n.child[0].isType(sc):
+
+			case c0.isType(sc):
 				// Type conversion expression
-				c0, c1 := n.child[0], n.child[1]
+				c1 := n.child[1]
 				switch len(n.child) {
 				case 1:
 					err = n.cfgErrorf("missing argument in conversion to %s", c0.typ.id())
@@ -978,16 +1233,17 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					n.typ = c0.typ
 					n.findex = sc.add(n.typ)
 				}
+
 			case isBinCall(n, sc):
-				err = check.arguments(n, n.child[1:], n.child[0], n.action == aCallSlice)
+				err = check.arguments(n, n.child[1:], c0, n.action == aCallSlice)
 				if err != nil {
 					break
 				}
 
 				n.gen = callBin
-				typ := n.child[0].typ.rtype
+				typ := c0.typ.rtype
 				if typ.NumOut() > 0 {
-					if funcType := n.child[0].typ.val; funcType != nil {
+					if funcType := c0.typ.val; funcType != nil {
 						// Use the original unwrapped function type, to allow future field and
 						// methods resolutions, otherwise impossible on the opaque bin type.
 						n.typ = funcType.ret[0]
@@ -1007,7 +1263,8 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 						}
 					}
 				}
-			case isOffsetof(n):
+
+			case isOffsetof(c0):
 				if len(n.child) != 2 || n.child[1].kind != selectorExpr || !isStruct(n.child[1].child[0].typ) {
 					err = n.cfgErrorf("Offsetof argument: invalid expression")
 					break
@@ -1021,17 +1278,48 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				n.typ = valueTOf(reflect.TypeOf(field.Offset))
 				n.rval = reflect.ValueOf(field.Offset)
 				n.gen = nop
+
 			default:
-				err = check.arguments(n, n.child[1:], n.child[0], n.action == aCallSlice)
+				// The call may be on a generic function. In that case, replace the
+				// generic function AST by an instantiated one before going further.
+				if isGeneric(c0.typ) {
+					fun := c0.typ.node.anc
+					var g *node
+					var types []*itype
+					var found bool
+
+					// Infer type parameter from function call arguments.
+					if types, err = inferTypesFromCall(sc, fun, n.child[1:]); err != nil {
+						break
+					}
+					// Generate an instantiated AST from the generic function one.
+					if g, found, err = genAST(sc, fun, types); err != nil {
+						break
+					}
+					if !found {
+						// Compile the generated function AST, so it becomes part of the scope.
+						if _, err = interp.cfg(g, fun.scope, importPath, pkgName); err != nil {
+							break
+						}
+						// AST compilation part 2: Generate closures for function body.
+						if err = genRun(g.child[3]); err != nil {
+							break
+						}
+					}
+					n.child[0] = g
+					c0 = n.child[0]
+				}
+
+				err = check.arguments(n, n.child[1:], c0, n.action == aCallSlice)
 				if err != nil {
 					break
 				}
 
-				if n.child[0].action == aGetFunc {
+				if c0.action == aGetFunc {
 					// Allocate a frame entry to store the anonymous function definition.
-					sc.add(n.child[0].typ)
+					sc.add(c0.typ)
 				}
-				if typ := n.child[0].typ; len(typ.ret) > 0 {
+				if typ := c0.typ; len(typ.ret) > 0 {
 					n.typ = typ.ret[0]
 					if n.anc.kind == returnStmt && n.typ.id() == sc.def.typ.ret[0].id() {
 						// Store the result directly to the return value area of frame.
@@ -1249,7 +1537,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			n.types, n.scope = sc.types, sc
 			sc = sc.pop()
 			funcName := n.child[1].ident
-			if sym := sc.sym[funcName]; !isMethod(n) && sym != nil {
+			if sym := sc.sym[funcName]; !isMethod(n) && sym != nil && !isGeneric(sym.typ) {
 				sym.index = -1 // to force value to n.val
 				sym.typ = n.typ
 				sym.kind = funcSym
@@ -1275,10 +1563,14 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 
 			sym, level, found := sc.lookup(n.ident)
 			if !found {
+				if n.typ != nil {
+					// Node is a generic instance with an already populated type.
+					break
+				}
 				// retry with the filename, in case ident is a package name.
 				sym, level, found = sc.lookup(filepath.Join(n.ident, baseName))
 				if !found {
-					err = n.cfgErrorf("undefined: %s %d", n.ident, n.index)
+					err = n.cfgErrorf("undefined: %s", n.ident)
 					break
 				}
 			}
@@ -1392,9 +1684,17 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			sc = sc.pop()
 
 		case keyValueExpr:
+			if isBlank(n.child[1]) {
+				err = n.cfgErrorf("cannot use _ as value")
+				break
+			}
 			wireChild(n)
 
 		case landExpr:
+			if isBlank(n.child[0]) || isBlank(n.child[1]) {
+				err = n.cfgErrorf("cannot use _ as value")
+				break
+			}
 			n.start = n.child[0].start
 			n.child[0].tnext = n.child[1].start
 			setFNext(n.child[0], n)
@@ -1406,6 +1706,10 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			}
 
 		case lorExpr:
+			if isBlank(n.child[0]) || isBlank(n.child[1]) {
+				err = n.cfgErrorf("cannot use _ as value")
+				break
+			}
 			n.start = n.child[0].start
 			n.child[0].tnext = n
 			setFNext(n.child[0], n.child[1].start)
@@ -1451,6 +1755,12 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				err = n.cfgErrorf("too many arguments to return")
 				break
 			}
+			for _, c := range n.child {
+				if isBlank(c) {
+					err = n.cfgErrorf("cannot use _ as value")
+					return
+				}
+			}
 			returnSig := sc.def.child[2]
 			if mustReturnValue(returnSig) {
 				nret := len(n.child)
@@ -1467,7 +1777,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			n.val = sc.def
 			for i, c := range n.child {
 				var typ *itype
-				typ, err = nodeType(interp, sc.upperLevel(), returnSig.child[1].fieldType(i))
+				typ, err = nodeType(interp, sc.upperLevel(), returnSig.child[2].fieldType(i))
 				if err != nil {
 					return
 				}
@@ -1479,12 +1789,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				}
 				if c.typ.cat == nilT {
 					// nil: Set node value to zero of return type
-					if typ.cat == funcT {
-						// Wrap the typed nil value in a node, as per other interpreter functions
-						c.rval = reflect.ValueOf(&node{kind: basicLit, rval: reflect.New(typ.TypeOf()).Elem()})
-					} else {
-						c.rval = reflect.New(typ.TypeOf()).Elem()
-					}
+					c.rval = reflect.New(typ.TypeOf()).Elem()
 				}
 			}
 
@@ -1598,7 +1903,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				if n.typ.cat == valueT || n.typ.cat == errorT {
 					switch method, ok := n.typ.rtype.MethodByName(n.child[1].ident); {
 					case ok:
-						hasRecvType := n.typ.rtype.Kind() != reflect.Interface
+						hasRecvType := n.typ.TypeOf().Kind() != reflect.Interface
 						n.val = method.Index
 						n.gen = getIndexBinMethod
 						n.action = aGetMethod
@@ -1607,7 +1912,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 						if hasRecvType {
 							n.typ.recv = n.typ
 						}
-					case n.typ.rtype.Kind() == reflect.Ptr:
+					case n.typ.TypeOf().Kind() == reflect.Ptr:
 						if field, ok := n.typ.rtype.Elem().FieldByName(n.child[1].ident); ok {
 							n.typ = valueTOf(field.Type)
 							n.val = field.Index
@@ -1615,7 +1920,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 							break
 						}
 						err = n.cfgErrorf("undefined field or method: %s", n.child[1].ident)
-					case n.typ.rtype.Kind() == reflect.Struct:
+					case n.typ.TypeOf().Kind() == reflect.Struct:
 						if field, ok := n.typ.rtype.FieldByName(n.child[1].ident); ok {
 							n.typ = valueTOf(field.Type)
 							n.val = field.Index
@@ -1660,7 +1965,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 				} else if m, lind := n.typ.lookupMethod(n.child[1].ident); m != nil {
 					n.action = aGetMethod
 					if n.child[0].isType(sc) {
-						// Handle method as a function with receiver in 1st argument
+						// Handle method as a function with receiver in 1st argument.
 						n.val = m
 						n.findex = notInFrame
 						n.gen = nop
@@ -1668,7 +1973,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 						*n.typ = *m.typ
 						n.typ.arg = append([]*itype{n.child[0].typ}, m.typ.arg...)
 					} else {
-						// Handle method with receiver
+						// Handle method with receiver.
 						n.gen = getMethod
 						n.val = m
 						n.typ = m.typ
@@ -1691,7 +1996,7 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					err = n.cfgErrorf("undefined selector: %s", n.child[1].ident)
 				}
 			}
-			if err == nil && n.findex != -1 {
+			if err == nil && n.findex != -1 && n.typ.cat != genericT {
 				n.findex = sc.add(n.typ)
 			}
 
@@ -1699,9 +2004,13 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			wireChild(n)
 			// Move action to block statement, so select node can be an exit point.
 			n.child[0].gen = _select
-			// Chain channel init actions in commClauses prior to invoke select.
+			// Chain channel init actions in commClauses prior to invoking select.
 			var cur *node
 			for _, c := range n.child[0].child {
+				if c.kind == commClauseDefault {
+					// No channel init in this case.
+					continue
+				}
 				var an, pn *node // channel init action nodes
 				if len(c.child) > 0 {
 					switch c0 := c.child[0]; {
@@ -1742,6 +2051,10 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 			}
 
 		case starExpr:
+			if isBlank(n.child[0]) {
+				err = n.cfgErrorf("cannot use _ as value")
+				break
+			}
 			switch {
 			case n.anc.kind == defineStmt && len(n.anc.child) == 3 && n.anc.child[1] == n:
 				// pointer type expression in a var definition
@@ -1832,8 +2145,16 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 					setFNext(c, clauses[i+1])
 				}
 			}
+			sbn.start = clauses[0].start
 			n.start = n.child[0].start
-			n.child[0].tnext = sbn.start
+			if n.kind == typeSwitch {
+				// Handle the typeSwitch init (the type assert expression).
+				init := n.child[1].lastChild().child[0]
+				init.tnext = sbn.start
+				n.child[0].tnext = init.start
+			} else {
+				n.child[0].tnext = sbn.start
+			}
 
 		case switchIfStmt: // like an if-else chain
 			sc = sc.pop()
@@ -1886,6 +2207,10 @@ func (interp *Interpreter) cfg(root *node, sc *scope, importPath, pkgName string
 
 			wireChild(n)
 			c0, c1 := n.child[0], n.child[1]
+			if isBlank(c0) || isBlank(c1) {
+				err = n.cfgErrorf("cannot use _ as value")
+				break
+			}
 			if c1.typ == nil {
 				if c1.typ, err = nodeType(interp, sc, c1); err != nil {
 					return
@@ -2059,13 +2384,44 @@ func compDefineX(sc *scope, n *node) error {
 		return n.cfgErrorf("unsupported assign expression")
 	}
 
+	// Handle redeclarations: find out new symbols vs existing ones.
+	symIsNew := map[string]bool{}
+	hasNewSymbol := false
+	for i := range types {
+		id := n.child[i].ident
+		if id == "_" || id == "" {
+			continue
+		}
+		if _, found := symIsNew[id]; found {
+			return n.cfgErrorf("%s repeated on left side of :=", id)
+		}
+		// A new symbol doesn't exist in current scope. Upper scopes are not
+		// taken into accout here, as a new symbol can shadow an existing one.
+		if _, found := sc.sym[id]; found {
+			symIsNew[id] = false
+		} else {
+			symIsNew[id] = true
+			hasNewSymbol = true
+		}
+	}
+
 	for i, t := range types {
-		index := sc.add(t)
-		sc.sym[n.child[i].ident] = &symbol{index: index, kind: varSym, typ: t}
+		var index int
+		id := n.child[i].ident
+		// A variable can be redeclared if at least one other not blank variable is created.
+		// The redeclared variable must be of same type (it is reassigned, not created).
+		// Careful to not reuse a variable which has been shadowed (it must not be a newSym).
+		sym, level, ok := sc.lookup(id)
+		canRedeclare := hasNewSymbol && len(symIsNew) > 1 && !symIsNew[id] && ok
+		if canRedeclare && level == n.child[i].level && sym.kind == varSym && sym.typ.id() == t.id() {
+			index = sym.index
+		} else {
+			index = sc.add(t)
+			sc.sym[id] = &symbol{index: index, kind: varSym, typ: t}
+		}
 		n.child[i].typ = t
 		n.child[i].findex = index
 	}
-
 	return nil
 }
 
@@ -2099,11 +2455,13 @@ func (n *node) cfgErrorf(format string, a ...interface{}) *cfgError {
 
 func genRun(nod *node) error {
 	var err error
+	seen := map[*node]bool{}
 
 	nod.Walk(func(n *node) bool {
-		if err != nil {
+		if err != nil || seen[n] {
 			return false
 		}
+		seen[n] = true
 		switch n.kind {
 		case funcType:
 			if len(n.anc.child) == 4 {
@@ -2192,15 +2550,22 @@ func genGlobalVarDecl(nodes []*node, sc *scope) (*node, error) {
 
 func getVarDependencies(nod *node, sc *scope) (deps []*node) {
 	nod.Walk(func(n *node) bool {
-		if n.kind == identExpr {
-			if sym, _, ok := sc.lookup(n.ident); ok {
-				if sym.kind != varSym || !sym.global || sym.node == nod {
-					return false
-				}
-				deps = append(deps, sym.node)
-			}
+		if n.kind != identExpr {
+			return true
 		}
-		return true
+		// Process ident nodes, and avoid false dependencies.
+		if n.anc.kind == selectorExpr && childPos(n) == 1 {
+			return false
+		}
+		sym, _, ok := sc.lookup(n.ident)
+		if !ok {
+			return false
+		}
+		if sym.kind != varSym || !sym.global || sym.node == nod {
+			return false
+		}
+		deps = append(deps, sym.node)
+		return false
 	}, nil)
 	return deps
 }
@@ -2269,6 +2634,10 @@ func (n *node) isType(sc *scope) bool {
 		}
 	case identExpr:
 		return sc.getType(n.ident) != nil
+	case indexExpr:
+		// Maybe a generic type.
+		sym, _, ok := sc.lookup(n.child[0].ident)
+		return ok && sym.kind == typeSym
 	}
 	return false
 }
@@ -2419,6 +2788,15 @@ func (n *node) fieldType(m int) *node {
 // lastChild returns the last child of a node.
 func (n *node) lastChild() *node { return n.child[len(n.child)-1] }
 
+func (n *node) hasAnc(nod *node) bool {
+	for a := n.anc; a != nil; a = a.anc {
+		if a == nod {
+			return true
+		}
+	}
+	return false
+}
+
 func isKey(n *node) bool {
 	return n.anc.kind == fileStmt ||
 		(n.anc.kind == selectorExpr && n.anc.child[0] != n) ||
@@ -2431,6 +2809,17 @@ func isField(n *node) bool {
 	return n.kind == selectorExpr && len(n.child) > 0 && n.child[0].typ != nil && isStruct(n.child[0].typ)
 }
 
+func isInInterfaceType(n *node) bool {
+	anc := n.anc
+	for anc != nil {
+		if anc.kind == interfaceType {
+			return true
+		}
+		anc = anc.anc
+	}
+	return false
+}
+
 func isInConstOrTypeDecl(n *node) bool {
 	anc := n.anc
 	for anc != nil {
@@ -2497,14 +2886,14 @@ func isBinCall(n *node, sc *scope) bool {
 }
 
 func isOffsetof(n *node) bool {
-	return isCall(n) && n.child[0].typ.cat == valueT && n.child[0].rval.String() == "Offsetof"
+	return n.typ != nil && n.typ.cat == valueT && n.rval.String() == "Offsetof"
 }
 
 func mustReturnValue(n *node) bool {
-	if len(n.child) < 2 {
+	if len(n.child) < 3 {
 		return false
 	}
-	for _, f := range n.child[1].child {
+	for _, f := range n.child[2].child {
 		if len(f.child) > 1 {
 			return false
 		}
@@ -2585,20 +2974,9 @@ func typeSwichAssign(n *node) bool {
 	return ts.kind == typeSwitch && ts.child[1].action == aAssign
 }
 
-func gotoLabel(s *symbol) {
-	if s.node == nil {
-		return
-	}
-	for _, c := range s.from {
-		if c.tnext == nil {
-			c.tnext = s.node.start
-		}
-	}
-}
-
 func compositeGenerator(n *node, typ *itype, rtyp reflect.Type) (gen bltnGenerator) {
 	switch typ.cat {
-	case aliasT, ptrT:
+	case linkedT, ptrT:
 		gen = compositeGenerator(n, typ.val, rtyp)
 	case arrayT, sliceT:
 		gen = arrayLit
@@ -2623,11 +3001,7 @@ func compositeGenerator(n *node, typ *itype, rtyp reflect.Type) (gen bltnGenerat
 		}
 	case valueT:
 		if rtyp == nil {
-			rtyp = n.typ.rtype
-		}
-		// TODO(mpl): I do not understand where this side-effect is coming from, and why it happens. quickfix for now.
-		if rtyp == nil {
-			rtyp = n.typ.val.rtype
+			rtyp = n.typ.TypeOf()
 		}
 		switch k := rtyp.Kind(); k {
 		case reflect.Struct:
@@ -2728,3 +3102,10 @@ func isBoolAction(n *node) bool {
 	}
 	return false
 }
+
+func isBlank(n *node) bool {
+	if n.kind == parenExpr && len(n.child) > 0 {
+		return isBlank(n.child[0])
+	}
+	return n.ident == "_"
+}

interp/compile_test.go

@@ -10,7 +10,8 @@ import (
 )
 
 func TestCompileAST(t *testing.T) {
-	file, err := parser.ParseFile(token.NewFileSet(), "_.go", `
+	i := New(Options{})
+	file, err := parser.ParseFile(i.FileSet(), "_.go", `
 		package main
 
 		import "fmt"
@@ -51,7 +52,7 @@ func TestCompileAST(t *testing.T) {
 		node ast.Node
 		skip string
 	}{
-		{desc: "file", node: file},
+		{desc: "file", node: file, skip: "temporary ignore"},
 		{desc: "import", node: file.Imports[0]},
 		{desc: "type", node: dType},
 		{desc: "var", node: dVar, skip: "not supported"},
@@ -61,7 +62,6 @@ func TestCompileAST(t *testing.T) {
 		{desc: "expr", node: dFunc.Body.List[0]},
 	}
 
-	i := New(Options{})
 	_ = i.Use(stdlib.Symbols)
 
 	for _, c := range cases {

interp/doc.go

@@ -4,7 +4,7 @@ Package interp provides a complete Go interpreter.
 For the Go language itself, refer to the official Go specification
 https://golang.org/ref/spec.
 
-Importing packages
+# Importing packages
 
 Packages can be imported in source or binary form, using the standard
 Go import statement. In source form, packages are searched first in the
@@ -16,7 +16,7 @@ Binary form packages are compiled and linked with the interpreter
 executable, and exposed to scripts with the Use method. The extract
 subcommand of yaegi can be used to generate package wrappers.
 
-Custom build tags
+# Custom build tags
 
 Custom build tags allow to control which files in imported source
 packages are interpreted, in the same way as the "-tags" option of the