interp: do not wrap empty interface

The empty interface (interface{}), and its variants (such as []interface{} and map[string]interface{}), are commonly used in Go to (json) Unmarshal arbitrary data. Within Yaegi, all interface types are wrapped in a valueInterface struct in order to retain all the information needed for a consistent internal state (as reflect is not enough to achieve that). However, this wrapping ends up being problematic when it comes to the type assertions related to the aforementioned Unmarshaling.

Therefore, this PR is an attempt to consider the empty interface (and its variants) as an exception within Yaegi, that should never be wrapped within a valueInterface, and to treat it similarly to the other basic Go types. The assumption is that the wrapping should not be needed, as there is no information about implemented methods to maintain.

Fixes #984 
Fixes #829 
Fixes #1015

.github/workflows/go-cross.yml

@@ -0,0 +1,67 @@
+name: Build Cross OS
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+
+  cross:
+    name: Go
+    runs-on: ${{ matrix.os }}
+    defaults:
+      run:
+        working-directory: ${{ github.workspace }}/go/src/github.com/traefik/yaegi
+
+    strategy:
+      matrix:
+        go-version: [ 1.14, 1.15 ]
+        os: [ubuntu-latest, macos-latest, windows-latest]
+
+        include:
+          - os: ubuntu-latest
+            go-path-suffix: /go
+          - os: macos-latest
+            go-path-suffix: /go
+          - os: windows-latest
+            go-path-suffix: \go
+
+    steps:
+      # https://github.com/marketplace/actions/setup-go-environment
+      - name: Set up Go ${{ matrix.go-version }}
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go-version }}
+
+      # https://github.com/marketplace/actions/checkout
+      - name: Checkout code
+        uses: actions/checkout@v2
+        with:
+          path: go/src/github.com/traefik/yaegi
+
+      # https://github.com/marketplace/actions/cache
+      - name: Cache Go modules
+        uses: actions/cache@v2
+        with:
+          path: |
+            ~/go/pkg/mod              # Module download cache
+            ~/.cache/go-build         # Build cache (Linux)
+            ~/Library/Caches/go-build # Build cache (Mac)
+            '%LocalAppData%\go-build' # Build cache (Windows)
+          key: ${{ runner.os }}-${{ matrix.go-version }}-go-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            ${{ runner.os }}-${{ matrix.go-version }}-go-
+
+      - name: Setup GOPATH
+        run: go env -w GOPATH=${{ github.workspace }}${{ matrix.go-path-suffix }}
+
+# TODO fail on windows
+#      - name: Tests
+#        run: go test -v -cover ./...
+#        env:
+#          GOPATH: ${{ github.workspace }}${{ matrix.go-path }}
+
+      - name: Build
+        run: go build -race -v -ldflags "-s -w" -trimpath

.github/workflows/main.yml

@@ -0,0 +1,110 @@
+name: Main
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+env:
+  GO_VERSION: 1.15
+  GOLANGCI_LINT_VERSION: v1.36.0
+
+jobs:
+
+  linting:
+    name: Linting
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set up Go ${{ env.GO_VERSION }}
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ env.GO_VERSION }}
+
+      - name: Check out code
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Check and get dependencies
+        run: |
+          go mod tidy
+          git diff --exit-code go.mod
+          # git diff --exit-code go.sum
+          go mod download
+
+      - name: Install golangci-lint ${{ env.GOLANGCI_LINT_VERSION }}
+        run: curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin ${GOLANGCI_LINT_VERSION}
+
+      - name: Run golangci-lint ${{ env.GOLANGCI_LINT_VERSION }}
+        run: make check
+
+  generate:
+    name: Checks code and generated code
+    runs-on: ubuntu-latest
+    needs: linting
+    strategy:
+      matrix:
+        go-version: [ 1.14, 1.15 ]
+    steps:
+      - name: Set up Go ${{ matrix.go-version }}
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go-version }}
+
+      - name: Check out code
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Check generated code
+        run: |
+          rm -f interp/op.go
+          make generate
+          git update-index -q --refresh
+          CHANGED=$(git diff-index --name-only HEAD --)
+          test -z "$CHANGED" || echo $CHANGED
+          test -z "$CHANGED"
+
+  main:
+    name: Build and Test
+    runs-on: ubuntu-latest
+    needs: linting
+    defaults:
+      run:
+        working-directory: ${{ github.workspace }}/go/src/github.com/traefik/yaegi
+    strategy:
+      matrix:
+        go-version: [ 1.14, 1.15 ]
+
+    steps:
+      - name: Set up Go ${{ matrix.go-version }}
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go-version }}
+
+      - name: Check out code
+        uses: actions/checkout@v2
+        with:
+          path: go/src/github.com/traefik/yaegi
+          fetch-depth: 0
+
+      # https://github.com/marketplace/actions/cache
+      - name: Cache Go modules
+        uses: actions/cache@v2
+        with:
+          path: ./_test/tmp
+          key: ${{ runner.os }}-yaegi-${{ hashFiles('**//_test/tmp/') }}
+          restore-keys: |
+            ${{ runner.os }}-yaegi-
+
+      - name: Setup GOPATH
+        run: go env -w GOPATH=${{ github.workspace }}/go
+
+      - name: Build
+        run: go build -v ./...
+
+      - name: Run tests
+        run: make tests
+        env:
+          GOPATH: ${{ github.workspace }}/go

.github/workflows/release.yml

@@ -0,0 +1,42 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - v[0-9]+.[0-9]+*
+
+env:
+  GO_VERSION: 1.15
+
+jobs:
+
+  release:
+    name: Create a release
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Set up Go ${{ env.GO_VERSION }}
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ env.GO_VERSION }}
+
+      - name: Check out code
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Cache Go modules
+        uses: actions/cache@v2
+        with:
+          path: ~/go/pkg/mod
+          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            ${{ runner.os }}-go-
+
+      - name: Run GoReleaser
+        uses: goreleaser/goreleaser-action@v2
+        with:
+          version: latest
+          args: release --rm-dist
+        env:
+          GITHUB_TOKEN: ${{ secrets.GH_TOKEN_REPO }}

.golangci.toml

@@ -33,16 +33,23 @@
     "gochecknoinits",
     "gochecknoglobals",
     "wsl",
+    "nlreturn",
     "godox",
     "funlen",
     "gocognit",
     "stylecheck",
     "gomnd",
     "testpackage",
+    "paralleltest",
+    "tparallel",
     "goerr113",
+    "wrapcheck",
     "nestif",
     "exhaustive",
-    "nlreturn",
+    "exhaustivestruct",
+    "forbidigo",
+    "ifshort",
+    "errorlint", # TODO: must be reactivate before fixes
   ]
 
 [issues]
@@ -61,3 +68,6 @@
   [[issues.exclude-rules]]
     path = "interp/interp.go"
     text = "`out` can be `io.Writer`"
+  [[issues.exclude-rules]]
+    path = "interp/interp_eval_test.go"
+    linters = ["thelper"]

.goreleaser.yml

@@ -47,7 +47,7 @@ archives:
       - LICENSE
 
 brews:
-  - github:
+  - tap:
       owner: traefik
       name: homebrew-tap
     commit_author:

.travis.yml

@@ -1,60 +0,0 @@
-language: go
-
-dist: xenial
-
-branches:
-  only:
-    - master
-    - /^v\d+\.\d+(\.\d+)?(-\S*)?$/
-
-notifications:
-  email:
-    on_success: never
-    on_failure: change
-
-cache:
-  directories:
-    - $GOPATH/pkg/mod
-
-matrix:
-  fast_finish: true
-  include:
-    - go: 1.14.x
-    - go: 1.15.x
-      env: STABLE=true
-
-env:
-  global:
-    - GO111MODULE=on
-
-go_import_path: github.com/traefik/yaegi
-
-before_install:
-  # Install linters and misspell
-  - curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | bash -s -- -b $GOPATH/bin ${GOLANGCI_LINT_VERSION}
-  - golangci-lint --version
-
-install:
-  - echo "TRAVIS_GO_VERSION=$TRAVIS_GO_VERSION"
-  - go mod download
-
-before_script:
-  - rm -f interp/op.go
-  - make generate
-  - git update-index -q --refresh
-  - CHANGED=$(git diff-index --name-only HEAD --)
-  - test -z "$CHANGED" || echo $CHANGED
-  - test -z "$CHANGED"
-
-script:
-  - make check
-  - go build -v ./...
-  - make tests
-
-deploy:
-  - provider: script
-    skip_cleanup: true
-    script: curl -sL https://git.io/goreleaser | bash
-    on:
-      tags: true
-      condition: $STABLE = true

_test/add1.go

@@ -1,10 +1,33 @@
 package main
 
 func main() {
-	b := 2
-	var a interface{} = 5 + b
+	b := 2 // int
+
+	var c int = 5 + b
+	println(c)
+
+	var d int32 = 6 + int32(b)
+	println(d)
+
+	var a interface{} = 7 + b
+	println(a.(int))
+
+	var e int32 = 2
+	var f interface{} = 8 + e
+	println(f.(int32))
+
+	a = 9 + e
+	println(a.(int32))
+
+	var g int = 2
+	a = 10 + g
 	println(a.(int))
 }
 
 // Output:
 // 7
+// 8
+// 9
+// 10
+// 11
+// 12

_test/addr2.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"encoding/xml"
+	"errors"
+	"fmt"
+)
+
+type Email struct {
+	Where string `xml:"where,attr"`
+	Addr  string
+}
+
+func f(r interface{}) error {
+	return withPointerAsInterface(&r)
+}
+
+func withPointerAsInterface(r interface{}) error {
+	_ = (r).(*interface{})
+	rp, ok := (r).(*interface{})
+	if !ok {
+		return errors.New("cannot assert to *interface{}")
+	}
+	em, ok := (*rp).(*Email)
+	if !ok {
+		return errors.New("cannot assert to *Email")
+	}
+	em.Where = "work"
+	em.Addr = "bob@work.com"
+	return nil
+}
+
+func ff(s string, r interface{}) error {
+	return xml.Unmarshal([]byte(s), r)
+}
+
+func fff(s string, r interface{}) error {
+	return xml.Unmarshal([]byte(s), &r)
+}
+
+func main() {
+	data := `
+		<Email where='work'>
+			<Addr>bob@work.com</Addr>
+		</Email>
+	`
+	v := Email{}
+	err := f(&v)
+	fmt.Println(err, v)
+
+	vv := Email{}
+	err = ff(data, &vv)
+	fmt.Println(err, vv)
+
+	vvv := Email{}
+	err = ff(data, &vvv)
+	fmt.Println(err, vvv)
+}
+
+// Ouput:
+// <nil> {work bob@work.com}
+// <nil> {work bob@work.com}
+// <nil> {work bob@work.com}

_test/addr3.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	var a interface{}
+	a = 2
+	fmt.Println(a)
+
+	var b *interface{}
+	b = &a
+	fmt.Println(*b)
+
+	var c **interface{}
+	c = &b
+	fmt.Println(**c)
+}
+
+// Output:
+// 2
+// 2
+// 2

_test/addr4.go

@@ -0,0 +1,114 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+)
+
+const jsonData = `[
+  "foo",
+  "bar"
+]`
+
+const jsonData2 = `[
+  {"foo": "foo"},
+  {"bar": "bar"}
+]`
+
+const jsonData3 = `{
+  "foo": "foo",
+  "bar": "bar"
+}`
+
+func fromSlice() {
+	var a []interface{}
+	var c, d interface{}
+	c = 2
+	d = 3
+	a = []interface{}{c, d}
+
+	if err := json.Unmarshal([]byte(jsonData), &a); err != nil {
+		log.Fatalln(err)
+	}
+
+	for k, v := range a {
+		fmt.Println(k, ":", v)
+	}
+}
+
+func fromEmpty() {
+	var a interface{}
+	var c, d interface{}
+	c = 2
+	d = 3
+	a = []interface{}{c, d}
+
+	if err := json.Unmarshal([]byte(jsonData), &a); err != nil {
+		log.Fatalln(err)
+	}
+
+	b := a.([]interface{})
+
+	for k, v := range b {
+		fmt.Println(k, ":", v)
+	}
+}
+
+func sliceOfObjects() {
+	var a interface{}
+
+	if err := json.Unmarshal([]byte(jsonData2), &a); err != nil {
+		log.Fatalln(err)
+	}
+
+	b := a.([]interface{})
+
+	for k, v := range b {
+		fmt.Println(k, ":", v)
+	}
+}
+
+func intoMap() {
+	var a interface{}
+
+	if err := json.Unmarshal([]byte(jsonData3), &a); err != nil {
+		log.Fatalln(err)
+	}
+
+	b := a.(map[string]interface{})
+
+	seenFoo := false
+	for k, v := range b {
+		vv := v.(string)
+		if vv != "foo" {
+			if seenFoo {
+				fmt.Println(k, ":", vv)
+				break
+			}
+			kk := k
+			vvv := vv
+			defer fmt.Println(kk, ":", vvv)
+			continue
+		}
+		seenFoo = true
+		fmt.Println(k, ":", vv)
+	}
+}
+
+func main() {
+	fromSlice()
+	fromEmpty()
+	sliceOfObjects()
+	intoMap()
+}
+
+// Ouput:
+// 0 : foo
+// 1 : bar
+// 0 : foo
+// 1 : bar
+// 0 : map[foo:foo]
+// 1 : map[bar:bar]
+// foo : foo
+// bar : bar

_test/addr5.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/url"
+)
+
+func main() {
+	body := []byte(`{
+		"BODY_1": "VALUE_1",
+		"BODY_2": "VALUE_2",
+		"BODY_3": null,
+		"BODY_4": {
+			"BODY_1": "VALUE_1",
+			"BODY_2": "VALUE_2",
+			"BODY_3": null
+		},
+		"BODY_5": [
+			"VALUE_1",
+			"VALUE_2",
+			"VALUE_3"
+		]
+	}`)
+
+	values := url.Values{}
+
+	var rawData map[string]interface{}
+	err := json.Unmarshal(body, &rawData)
+	if err != nil {
+		fmt.Println("can't parse body")
+		return
+	}
+
+	for key, val := range rawData {
+		switch val.(type) {
+		case string, bool, float64:
+			values.Add(key, fmt.Sprint(val))
+		case nil:
+			values.Add(key, "")
+		case map[string]interface{}, []interface{}:
+			jsonVal, err := json.Marshal(val)
+			if err != nil {
+				fmt.Println("can't encode json")
+				return
+			}
+			values.Add(key, string(jsonVal))
+		}
+	}
+	fmt.Println(values.Get("BODY_1"))
+	fmt.Println(values.Get("BODY_2"))
+	fmt.Println(values.Get("BODY_3"))
+	fmt.Println(values.Get("BODY_4"))
+	fmt.Println(values.Get("BODY_5"))
+}
+
+// Output:
+// VALUE_1
+// VALUE_2
+// 
+// {"BODY_1":"VALUE_1","BODY_2":"VALUE_2","BODY_3":null}
+// ["VALUE_1","VALUE_2","VALUE_3"]

_test/assert0.go

@@ -0,0 +1,128 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+type MyWriter interface {
+	Write(p []byte) (i int, err error)
+}
+
+type DummyWriter interface {
+	Write(p []byte) (i int, err error)
+}
+
+type TestStruct struct{}
+
+func (t TestStruct) Write(p []byte) (n int, err error) {
+	return len(p), nil
+}
+
+func usesWriter(w MyWriter) {
+	n, _ := w.Write([]byte("hello world"))
+	fmt.Println(n)
+}
+
+type MyStringer interface {
+	String() string
+}
+
+type DummyStringer interface {
+	String() string
+}
+
+func usesStringer(s MyStringer) {
+	fmt.Println(s.String())
+}
+
+func main() {
+	// TODO(mpl): restore when we can deal with empty interface.
+//	var t interface{}
+	var t DummyWriter
+	t = TestStruct{}
+	var tw MyWriter
+	var ok bool
+	tw, ok = t.(MyWriter)
+	if !ok {
+		fmt.Println("TestStruct does not implement MyWriter")
+	} else {
+		fmt.Println("TestStruct implements MyWriter")
+		usesWriter(tw)
+	}
+	n, _ := t.(MyWriter).Write([]byte("hello world"))
+	fmt.Println(n)
+
+	// not redundant with the above, because it goes through a slightly different code path.
+	if _, ok := t.(MyWriter); !ok {
+		fmt.Println("TestStruct does not implement MyWriter")
+		return
+	} else {
+		fmt.Println("TestStruct implements MyWriter")
+	}
+
+	// TODO(mpl): restore
+	/*
+	t = 42
+	foo, ok := t.(MyWriter)
+	if !ok {
+		fmt.Println("42 does not implement MyWriter")
+	} else {
+		fmt.Println("42 implements MyWriter")
+	}
+	_ = foo
+
+	if _, ok := t.(MyWriter); !ok {
+		fmt.Println("42 does not implement MyWriter")
+	} else {
+		fmt.Println("42 implements MyWriter")
+	}
+	*/
+
+	// var tt interface{}
+	var tt DummyStringer
+	tt = time.Nanosecond
+	var myD MyStringer
+	myD, ok = tt.(MyStringer)
+	if !ok {
+		fmt.Println("time.Nanosecond does not implement MyStringer")
+	} else {
+		fmt.Println("time.Nanosecond implements MyStringer")
+		usesStringer(myD)
+	}
+	fmt.Println(tt.(MyStringer).String())
+
+	if _, ok := tt.(MyStringer); !ok {
+		fmt.Println("time.Nanosecond does not implement MyStringer")
+	} else {
+		fmt.Println("time.Nanosecond implements MyStringer")
+	}
+
+	// TODO(mpl): restore
+	/*
+	tt = 42
+	bar, ok := tt.(MyStringer)
+	if !ok {
+		fmt.Println("42 does not implement MyStringer")
+	} else {
+		fmt.Println("42 implements MyStringer")
+	}
+	_ = bar
+
+	if _, ok := tt.(MyStringer); !ok {
+		fmt.Println("42 does not implement MyStringer")
+	} else {
+		fmt.Println("42 implements MyStringer")
+	}
+	*/
+}
+
+// Output:
+// TestStruct implements MyWriter
+// 11
+// 11
+// TestStruct implements MyWriter
+// time.Nanosecond implements MyStringer
+// 1ns
+// 1ns
+// time.Nanosecond implements MyStringer

_test/assert1.go

@@ -0,0 +1,88 @@
+package main
+
+import (
+	"fmt"
+	"reflect"
+	"time"
+)
+
+type TestStruct struct{}
+
+func (t TestStruct) String() string {
+	return "hello world"
+}
+
+type DummyStringer interface{
+	String() string
+}
+
+func main() {
+	aType := reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
+
+	var t interface{}
+	t = time.Nanosecond
+	s, ok := t.(fmt.Stringer)
+	if !ok {
+		fmt.Println("time.Nanosecond does not implement fmt.Stringer")
+		return
+	}
+	fmt.Println(s.String())
+	fmt.Println(t.(fmt.Stringer).String())
+	bType := reflect.TypeOf(time.Nanosecond)
+	fmt.Println(bType.Implements(aType))
+
+	// not redundant with the above, because it goes through a slightly different code path.
+	if _, ok := t.(fmt.Stringer); !ok {
+		fmt.Println("time.Nanosecond does not implement fmt.Stringer")
+		return
+	} else {
+		fmt.Println("time.Nanosecond implements fmt.Stringer")
+	}
+
+	t = 42
+	foo, ok := t.(fmt.Stringer)
+	if !ok {
+		fmt.Println("42 does not implement fmt.Stringer")
+	} else {
+		fmt.Println("42 implements fmt.Stringer")
+		return
+	}
+	_ = foo
+
+	if _, ok := t.(fmt.Stringer); !ok {
+		fmt.Println("42 does not implement fmt.Stringer")
+	} else {
+		fmt.Println("42 implements fmt.Stringer")
+		return
+	}
+
+	// TODO(mpl): restore when fixed
+	// var tt interface{}
+	var tt DummyStringer
+	tt = TestStruct{}
+	ss, ok := tt.(fmt.Stringer)
+	if !ok {
+		fmt.Println("TestStuct does not implement fmt.Stringer")
+		return
+	}
+	fmt.Println(ss.String())
+	fmt.Println(tt.(fmt.Stringer).String())
+
+	if _, ok := tt.(fmt.Stringer); !ok {
+		fmt.Println("TestStuct does not implement fmt.Stringer")
+		return
+	} else {
+		fmt.Println("TestStuct implements fmt.Stringer")
+	}
+}
+
+// Output:
+// 1ns
+// 1ns
+// true
+// time.Nanosecond implements fmt.Stringer
+// 42 does not implement fmt.Stringer
+// 42 does not implement fmt.Stringer
+// hello world
+// hello world
+// TestStuct implements fmt.Stringer

_test/cap0.go

@@ -4,10 +4,16 @@ func f(a []int) interface{} {
 	return cap(a)
 }
 
+func g(a []int) int {
+	return cap(a)
+}
+
 func main() {
 	a := []int{1, 2}
+	println(g(a))
 	println(f(a).(int))
 }
 
 // Output:
 // 2
+// 2

_test/composite15.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"fmt"
+)
+
+func interfaceAsInts() {
+	var a interface{}
+	b := 2
+	c := 3
+	a = []int{b, c}
+
+	d, ok := a.([]int)
+	if !ok {
+		println("nope")
+		return
+	}
+
+	for _, v := range d {
+		fmt.Println(v)
+	}
+}
+
+func interfaceAsInterfaces() {
+	var a, b, c interface{}
+	b = 2
+	c = 3
+	a = []interface{}{b, c}
+
+	d, ok := a.([]interface{})
+	if !ok {
+		println("nope")
+		return
+	}
+	fmt.Println(d)
+
+	for _, v := range d {
+		fmt.Println(v)
+	}
+}
+
+func main() {
+	interfaceAsInts()
+	interfaceAsInterfaces()
+}
+
+// Output:
+// 2
+// 3
+// [2 3]
+// 2
+// 3

_test/composite16.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"fmt"
+	"net/url"
+)
+
+func main() {
+	body := url.Values{
+		"Action": {"none"},
+	}
+	fmt.Println(body)
+}
+
+// Output:
+// map[Action:[none]]

_test/composite17.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"html/template"
+)
+
+var str = `{{ stringOr .Data "test" }}`
+
+func main() {
+	_, err := template.New("test").
+		Funcs(template.FuncMap{
+			"stringOr": stringOr,
+		}).
+		Parse(str)
+	if err != nil {
+		println(err.Error())
+		return
+	}
+	println("success")
+}
+
+func stringOr(v, def string) string {
+	if v == "" {
+		return def
+	}
+	return v
+}
+
+// Output:
+// success

_test/const22.go

@@ -0,0 +1,15 @@
+package main
+
+const (
+	numDec uint8 = (1 << iota) / 2
+	numHex
+	numOct
+	numFloat
+)
+
+func main() {
+	println(13 & (numHex | numOct))
+}
+
+// Output:
+// 1

_test/const23.go

@@ -0,0 +1,12 @@
+package main
+
+const maxlen = len("hello")
+
+var gfm = [maxlen]byte{}
+
+func main() {
+	println(len(gfm))
+}
+
+// Output:
+// 5

_test/const24.go

@@ -0,0 +1,14 @@
+package main
+
+var aa = [...]int{1, 2, 3}
+
+const maxlen = cap(aa)
+
+var gfm = [maxlen]byte{}
+
+func main() {
+	println(len(gfm))
+}
+
+// Output:
+// 3

_test/fun15.go

@@ -2,10 +2,15 @@ package main
 
 func f1(a int) interface{} { return a + 1 }
 
+func f2(a int64) interface{} { return a + 1 }
+
 func main() {
 	c := f1(3)
 	println(c.(int))
+	b := f2(3)
+	println(b.(int64))
 }
 
 // Output:
 // 4
+// 4

_test/fun16.go

@@ -2,7 +2,13 @@ package main
 
 func f1(a int) int { return a + 1 }
 
-func f2(a int) interface{} { return f1(a) }
+func f2(a int) interface{} {
+	// TODO: re-enable the optimized case below, once we've figured out why it
+	// interferes with the empty interface model.
+	// return f1(a)
+	var foo interface{} = f1(a)
+	return foo
+}
 
 func main() {
 	c := f2(3)

_test/interface47.go

@@ -0,0 +1,32 @@
+package main
+
+type Doer interface {
+	Do() error
+}
+
+type T struct {
+	Name string
+}
+
+func (t *T) Do() error { println("in do"); return nil }
+
+func f() (Doer, error) { return &T{"truc"}, nil }
+
+type Ev struct {
+	doer func() (Doer, error)
+}
+
+func (e *Ev) do() {
+	d, _ := e.doer()
+	d.Do()
+}
+
+func main() {
+	e := &Ev{f}
+	println(e != nil)
+	e.do()
+}
+
+// Output:
+// true
+// in do

_test/interface48.go

@@ -0,0 +1,17 @@
+package main
+
+import "fmt"
+
+type I1 interface{ A }
+
+type A = I2
+
+type I2 interface{ F() I1 }
+
+func main() {
+	var i I1
+	fmt.Println(i)
+}
+
+// Output:
+// <nil>

_test/interface49.go

@@ -0,0 +1,45 @@
+package main
+
+type Descriptor interface {
+	ParentFile() FileDescriptor
+}
+
+type FileDescriptor interface {
+	Enums() EnumDescriptors
+	Services() ServiceDescriptors
+}
+
+type EnumDescriptors interface {
+	Get(i int) EnumDescriptor
+}
+
+type EnumDescriptor interface {
+	Values() EnumValueDescriptors
+}
+
+type EnumValueDescriptors interface {
+	Get(i int) EnumValueDescriptor
+}
+
+type EnumValueDescriptor interface {
+	Descriptor
+}
+
+type ServiceDescriptors interface {
+	Get(i int) ServiceDescriptor
+}
+
+type ServiceDescriptor interface {
+	Descriptor
+	isServiceDescriptor
+}
+
+type isServiceDescriptor interface{ ProtoType(ServiceDescriptor) }
+
+func main() {
+	var d Descriptor
+	println(d == nil)
+}
+
+// Output:
+// true

_test/issue-1007.go

@@ -0,0 +1,40 @@
+package main
+
+type TypeA struct {
+	B TypeB
+}
+
+type TypeB struct {
+	C1 *TypeC
+	C2 *TypeC
+}
+
+type TypeC struct {
+	Val string
+	D   *TypeD
+	D2  *TypeD
+}
+
+type TypeD struct {
+	Name string
+}
+
+func build() *TypeA {
+	return &TypeA{
+		B: TypeB{
+			C2: &TypeC{Val: "22"},
+		},
+	}
+}
+
+func Bar(s string) string {
+	a := build()
+	return s + "-" + a.B.C2.Val
+}
+
+func main() {
+	println(Bar("test"))
+}
+
+// Output:
+// test-22

_test/issue-1010.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+type MyJsonMarshaler struct{ n int }
+
+func (m MyJsonMarshaler) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf(`{"num": %d}`, m.n)), nil
+}
+
+func main() {
+	ch := make(chan json.Marshaler, 1)
+	ch <- MyJsonMarshaler{2}
+	m, err := json.Marshal(<-ch)
+	fmt.Println(string(m), err)
+}
+
+// Output:
+// {"num":2} <nil>

_test/issue-1022.go

@@ -0,0 +1,17 @@
+package main
+
+import "fmt"
+
+func main() {
+	defer func() {
+		r := recover()
+		if r != nil {
+			fmt.Println(r)
+		}
+	}()
+
+	panic("Ho Ho Ho!")
+}
+
+// Output:
+// Ho Ho Ho!

_test/issue-981.go

@@ -0,0 +1,15 @@
+package main
+
+import "fmt"
+
+func main() {
+	dp := make(map[int]int)
+	dp[0] = 1
+	for i := 1; i < 10; i++ {
+		dp[i] = dp[i-1] + dp[i-2]
+	}
+	fmt.Printf("%v\n", dp)
+}
+
+// Output:
+// map[0:1 1:1 2:2 3:3 4:5 5:8 6:13 7:21 8:34 9:55]

_test/issue-993.go

@@ -0,0 +1,15 @@
+package main
+
+var m map[string]int64
+
+func initVar() {
+	m = make(map[string]int64)
+}
+
+func main() {
+	initVar()
+	println(len(m))
+}
+
+// Output:
+// 0

_test/method34.go

@@ -12,10 +12,16 @@ type Hi interface {
 	Hello() string
 }
 
+type Hey interface {
+	Hello() string
+}
+
 func (r *Root) Hello() string { return "Hello " + r.Name }
 
 func main() {
-	var one interface{} = &One{Root{Name: "test2"}}
+	// TODO(mpl): restore when type assertions work again.
+	// var one interface{} = &One{Root{Name: "test2"}}
+	var one Hey = &One{Root{Name: "test2"}}
 	println(one.(Hi).Hello())
 }
 

_test/struct59.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"fmt"
+)
+
+type A struct {
+	B map[string]*B
+	C map[string]*C
+}
+
+type C struct {
+	D *D
+	E *E
+}
+
+type D struct {
+	F *F
+	G []G
+}
+
+type E struct {
+	H []H
+	F *F
+}
+
+type B struct{}
+type F struct{}
+type G struct{}
+type H struct{}
+
+func main() {
+	conf := &A{
+		B: make(map[string]*B),
+		C: make(map[string]*C),
+	}
+	fmt.Println(conf)
+}
+
+// Output:
+// &{map[] map[]}

_test/switch34.go

@@ -2,12 +2,26 @@ package main
 
 func main() {
 	var a interface{}
+	a = []int{3}
 	switch a.(type) {
 	case []int:
+		println("a is []int")
 	case []string:
+		println("a is []string")
+	}
+
+	var b interface{}
+	b = []string{"hello"}
+	switch b.(type) {
+	case []int:
+		println("b is []int")
+	case []string:
+		println("b is []string")
 	}
 	println("bye")
 }
 
 // Output:
+// a is []int
+// b is []string
 // bye

_test/time15.go

@@ -0,0 +1,15 @@
+package main
+
+import "time"
+
+type TimeValue time.Time
+
+func (v *TimeValue) decode() { println("in decode") }
+
+func main() {
+	var tv TimeValue
+	tv.decode()
+}
+
+// Output:
+// in decode

_test/time16.go

@@ -0,0 +1,11 @@
+package main
+
+import "time"
+
+func main() {
+	localTime := time.ANSIC
+	println(localTime)
+}
+
+// Output:
+// Mon Jan _2 15:04:05 2006

_test/var15.go

@@ -0,0 +1,15 @@
+package main
+
+var a int = 2
+
+func inca() {
+	a = a + 1
+}
+
+func main() {
+	inca()
+	println(a)
+}
+
+// Output:
+// 3

cmd/yaegi/extract.go

@@ -102,7 +102,7 @@ func genLicense(fname string) (string, error) {
 
 	f, err := os.Open(fname)
 	if err != nil {
-		return "", fmt.Errorf("could not open LICENSE file: %v", err)
+		return "", fmt.Errorf("could not open LICENSE file: %w", err)
 	}
 	defer func() { _ = f.Close() }()
 
@@ -116,7 +116,7 @@ func genLicense(fname string) (string, error) {
 		license.WriteString("//" + txt + "\n")
 	}
 	if sc.Err() != nil {
-		return "", fmt.Errorf("could not scan LICENSE file: %v", err)
+		return "", fmt.Errorf("could not scan LICENSE file: %w", err)
 	}
 
 	return license.String(), nil

cmd/yaegi/test.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"go/build"
 	"os"
+	"path/filepath"
 	"regexp"
 	"strconv"
 	"strings"
@@ -102,6 +103,18 @@ func test(arg []string) (err error) {
 	testing.Init()
 	os.Args = tf
 	flag.Parse()
+	path += string(filepath.Separator)
+	var dir string
+
+	switch strings.Split(path, string(filepath.Separator))[0] {
+	case ".", "..", string(filepath.Separator):
+		dir = path
+	default:
+		dir = filepath.Join(build.Default.GOPATH, "src", path)
+	}
+	if err = os.Chdir(dir); err != nil {
+		return err
+	}
 
 	i := interp.New(interp.Options{GoPath: build.Default.GOPATH, BuildTags: strings.Split(tags, ",")})
 	i.Use(stdlib.Symbols)

cmd/yaegi/yaegi_test.go

@@ -50,9 +50,9 @@ func TestYaegiCmdCancel(t *testing.T) {
 
 	yaegi := filepath.Join(tmp, "yaegi")
 	build := exec.Command("go", "build", "-race", "-o", yaegi, ".")
-	err = build.Run()
+	out, err := build.CombinedOutput()
 	if err != nil {
-		t.Fatalf("failed to build yaegi command: %v", err)
+		t.Fatalf("failed to build yaegi command: %v: %s", err, out)
 	}
 
 	// Test src must be terminated by a single newline.

example/pkg/pkg_test.go

@@ -104,7 +104,7 @@ func TestPackages(t *testing.T) {
 	for _, test := range testCases {
 		test := test
 		t.Run(test.desc, func(t *testing.T) {
-			goPath, err := filepath.Abs(test.goPath)
+			goPath, err := filepath.Abs(filepath.FromSlash(test.goPath))
 			if err != nil {
 				t.Fatal(err)
 			}
@@ -115,7 +115,7 @@ func TestPackages(t *testing.T) {
 
 			var msg string
 			if test.evalFile != "" {
-				if _, err := i.EvalPath(test.evalFile); err != nil {
+				if _, err := i.EvalPath(filepath.FromSlash(test.evalFile)); err != nil {
 					fatalStderrf(t, "%v", err)
 				}
 				msg = stdout.String()
@@ -146,6 +146,8 @@ func TestPackages(t *testing.T) {
 }
 
 func fatalStderrf(t *testing.T, format string, args ...interface{}) {
+	t.Helper()
+
 	fmt.Fprintf(os.Stderr, format+"\n", args...)
 	t.FailNow()
 }
@@ -159,7 +161,7 @@ func TestPackagesError(t *testing.T) {
 		{
 			desc:     "different packages in the same directory",
 			goPath:   "./_pkg9/",
-			expected: "1:21: import \"github.com/foo/pkg\" error: found packages pkg and pkgfalse in _pkg9/src/github.com/foo/pkg",
+			expected: `1:21: import "github.com/foo/pkg" error: found packages pkg and pkgfalse in ` + filepath.FromSlash("_pkg9/src/github.com/foo/pkg"),
 		},
 	}
 

extract/extract.go

@@ -241,7 +241,7 @@ func (e *Extractor) genContent(importPath string, p *types.Package) ([]byte, err
 	base := template.New("extract")
 	parse, err := base.Parse(model)
 	if err != nil {
-		return nil, fmt.Errorf("template parsing error: %v", err)
+		return nil, fmt.Errorf("template parsing error: %w", err)
 	}
 
 	if importPath == "log/syslog" {
@@ -274,13 +274,13 @@ func (e *Extractor) genContent(importPath string, p *types.Package) ([]byte, err
 	}
 	err = parse.Execute(b, data)
 	if err != nil {
-		return nil, fmt.Errorf("template error: %v", err)
+		return nil, fmt.Errorf("template error: %w", err)
 	}
 
 	// gofmt
 	source, err := format.Source(b.Bytes())
 	if err != nil {
-		return nil, fmt.Errorf("failed to format source: %v: %s", err, b.Bytes())
+		return nil, fmt.Errorf("failed to format source: %w: %s", err, b.Bytes())
 	}
 	return source, nil
 }
@@ -451,7 +451,7 @@ func genBuildTags() (string, error) {
 
 	minor, err := strconv.Atoi(minorRaw)
 	if err != nil {
-		return "", fmt.Errorf("failed to parse version: %v", err)
+		return "", fmt.Errorf("failed to parse version: %w", err)
 	}
 
 	// Only append an upper bound if we are not on the latest go

internal/cmd/genop/genop.go

@@ -11,7 +11,7 @@ import (
 
 const model = `package interp
 
-// Code generated by 'go run ../internal/genop/genop.go'. DO NOT EDIT.
+// Code generated by 'go run ../internal/cmd/genop/genop.go'. DO NOT EDIT.
 
 import (
 	"go/constant"
@@ -63,11 +63,38 @@ func {{$name}}(n *node) {
 			{{else}}
 			v1 := genValueInt(c1)
 			{{end -}}
+			{{- if (eq $name "add")}}
+			if n.typ.cat != interfaceT || len(n.typ.field) > 0 {
+				n.exec = func(f *frame) bltn {
+					_, j := v1(f)
+					dest(f).SetInt(i + j)
+					return next
+				}
+				return
+			}
+			var valf func(sum int64) reflect.Value
+			// TODO: cover other int types, and actually other numbers, and even all
+			// relevant operations, not just add.
+			switch typ.Kind() {
+			case reflect.Int:
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(int(sum)) }
+			case reflect.Int32:
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(int32(sum)) }
+			default: // int64
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(sum) }
+			}
+			n.exec = func(f *frame) bltn {
+				_, j := v1(f)
+				dest(f).Set(valf(i + j))
+				return next
+			}
+			{{else -}}
 			n.exec = func(f *frame) bltn {
 				_, j := v1(f)
 				dest(f).SetInt(i {{$op.Name}} j)
 				return next
 			}
+			{{end -}}
 		case c1.rval.IsValid():
 			v0 := genValueInt(c0)
 			{{- if $op.Shift}}
@@ -75,11 +102,38 @@ func {{$name}}(n *node) {
 			{{else}}
 			j := vInt(c1.rval)
 			{{end -}}
+			{{- if (eq $name "add")}}
+			var valf func(sum int64) reflect.Value
+			// TODO: cover other int types, and actually other numbers, and even all
+			// relevant operations, not just add.
+			switch typ.Kind() {
+			case reflect.Int:
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(int(sum)) }
+			case reflect.Int32:
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(int32(sum)) }
+			default: // int64
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(sum) }
+			}
+			if wantEmptyInterface(n) {
+				n.exec = func(f *frame) bltn {
+					_, i := v0(f)
+					dest(f).Set(valf(i + j))
+					return next
+				}
+				return
+			}
+			n.exec = func(f *frame) bltn {
+				_, i := v0(f)
+				dest(f).SetInt(i + j)
+				return next
+			}
+			{{else -}}
 			n.exec = func(f *frame) bltn {
 				_, i := v0(f)
 				dest(f).SetInt(i {{$op.Name}} j)
 				return next
 			}
+			{{end -}}
 		default:
 			v0 := genValueInt(c0)
 			{{- if $op.Shift}}
@@ -209,7 +263,11 @@ func {{$name}}Const(n *node) {
 		v := constant.BinaryOp(vConstantValue(v0), operator, vConstantValue(v1))
 		n.rval.Set(reflect.ValueOf(v))
 		{{- else}}
+		{{- if $op.Int}}
+		v := constant.BinaryOp(constant.ToInt(vConstantValue(v0)), token.{{tokenFromName $name}}, constant.ToInt(vConstantValue(v1)))
+		{{- else}}
 		v := constant.BinaryOp(vConstantValue(v0), token.{{tokenFromName $name}}, vConstantValue(v1))
+		{{- end}}
 		n.rval.Set(reflect.ValueOf(v))
 		{{- end}}
 	{{- if $op.Str}}
@@ -940,6 +998,7 @@ type Op struct {
 	Complex bool   // true if operator applies to complex
 	Shift   bool   // true if operator is a shift operation
 	Bool    bool   // true if operator applies to bool
+	Int     bool   // true if operator applies to int only
 }
 
 func main() {
@@ -968,17 +1027,17 @@ func main() {
 	b := &bytes.Buffer{}
 	data := map[string]interface{}{
 		"Arithmetic": map[string]Op{
-			"add":    {"+", true, true, true, false, false},
-			"sub":    {"-", false, true, true, false, false},
-			"mul":    {"*", false, true, true, false, false},
-			"quo":    {"/", false, true, true, false, false},
-			"rem":    {"%", false, false, false, false, false},
-			"shl":    {"<<", false, false, false, true, false},
-			"shr":    {">>", false, false, false, true, false},
-			"and":    {"&", false, false, false, false, false},
-			"or":     {"|", false, false, false, false, false},
-			"xor":    {"^", false, false, false, false, false},
-			"andNot": {"&^", false, false, false, false, false},
+			"add":    {"+", true, true, true, false, false, false},
+			"sub":    {"-", false, true, true, false, false, false},
+			"mul":    {"*", false, true, true, false, false, false},
+			"quo":    {"/", false, true, true, false, false, false},
+			"rem":    {"%", false, false, false, false, false, true},
+			"shl":    {"<<", false, false, false, true, false, true},
+			"shr":    {">>", false, false, false, true, false, true},
+			"and":    {"&", false, false, false, false, false, true},
+			"or":     {"|", false, false, false, false, false, true},
+			"xor":    {"^", false, false, false, false, false, true},
+			"andNot": {"&^", false, false, false, false, false, true},
 		},
 		"IncDec": map[string]Op{
 			"inc": {Name: "+"},
@@ -996,7 +1055,7 @@ func main() {
 			"not":    {Name: "!", Float: false, Bool: true},
 			"neg":    {Name: "-", Float: true, Bool: false},
 			"pos":    {Name: "+", Float: true, Bool: false},
-			"bitNot": {Name: "^", Float: false, Bool: false},
+			"bitNot": {Name: "^", Float: false, Bool: false, Int: true},
 		},
 	}
 	if err = parse.Execute(b, data); err != nil {

interp/cfg.go

@@ -75,6 +75,9 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 			case assignStmt, defineStmt:
 				a := n.anc
 				i := childPos(n) - a.nright
+				if i < 0 {
+					break
+				}
 				if len(a.child) > a.nright+a.nleft {
 					i--
 				}
@@ -285,8 +288,12 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 				// Get type from ancestor (implicit type)
 				if n.anc.kind == keyValueExpr && n == n.anc.child[0] {
 					n.typ = n.anc.typ.key
-				} else if n.anc.typ != nil {
-					n.typ = n.anc.typ.val
+				} else if atyp := n.anc.typ; atyp != nil {
+					if atyp.cat == valueT {
+						n.typ = &itype{cat: valueT, rtype: atyp.rtype.Elem()}
+					} else {
+						n.typ = atyp.val
+					}
 				}
 				if n.typ == nil {
 					err = n.cfgErrorf("undefined type")
@@ -415,9 +422,10 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 				return false
 			}
 
-			if n.child[1].kind == identExpr {
+			switch n.child[1].kind {
+			case identExpr, selectorExpr:
 				n.typ = &itype{cat: aliasT, val: typ, name: typeName}
-			} else {
+			default:
 				n.typ = typ
 				n.typ.name = typeName
 			}
@@ -547,10 +555,23 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 				n.findex = dest.findex
 				n.level = dest.level
 
-				// Propagate type
-				// TODO: Check that existing destination type matches source type
+				// Propagate type.
+				// TODO: Check that existing destination type matches source type.
+
+				// In the following, we attempt to optimize by skipping the assign
+				// operation and setting the source location directly to the destination
+				// location in the frame.
+				//
 				switch {
-				case n.action == aAssign && isCall(src) && dest.typ.cat != interfaceT && !isMapEntry(dest) && !isRecursiveField(dest):
+				case n.action != aAssign:
+					// Do not skip assign operation if it is combined with another operator.
+				case src.rval.IsValid():
+					// Do not skip assign operation if setting from a constant value.
+				case isMapEntry(dest):
+					// Setting a map entry requires an additional step, do not optimize.
+					// As we only write, skip the default useless getIndexMap dest action.
+					dest.gen = nop
+				case isCall(src) && dest.typ.cat != interfaceT && !isRecursiveField(dest):
 					// Call action may perform the assignment directly.
 					n.gen = nop
 					src.level = level
@@ -558,52 +579,45 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 					if src.typ.untyped && !dest.typ.untyped {
 						src.typ = dest.typ
 					}
-				case n.action == aAssign && src.action == aRecv:
+				case src.action == aRecv:
 					// Assign by reading from a receiving channel.
 					n.gen = nop
-					src.findex = dest.findex // Set recv address to LHS
+					src.findex = dest.findex // Set recv address to LHS.
 					dest.typ = src.typ
-				case n.action == aAssign && src.action == aCompositeLit && !isMapEntry(dest):
+				case src.action == aCompositeLit:
 					if dest.typ.cat == valueT && dest.typ.rtype.Kind() == reflect.Interface {
-						// Skip optimisation for assigned binary interface or map entry
-						// which require and additional operation to set the value
+						// Skip optimisation for assigned interface.
 						break
 					}
 					if dest.action == aGetIndex {
-						// optimization does not work when assigning to a struct field. Maybe we're not
-						// setting the right frame index or something, and we would end up not writing at
-						// the right place. So disabling it for now.
+						// Skip optimization, as it does not work when assigning to a struct field.
 						break
 					}
-					// Skip the assign operation entirely, the source frame index is set
-					// to destination index, avoiding extra memory alloc and duplication.
 					n.gen = nop
 					src.findex = dest.findex
 					src.level = level
-				case n.action == aAssign && len(n.child) < 4 && !src.rval.IsValid() && isArithmeticAction(src):
+				case len(n.child) < 4 && isArithmeticAction(src):
 					// Optimize single assignments from some arithmetic operations.
-					// Skip the assign operation entirely, the source frame index is set
-					// to destination index, avoiding extra memory alloc and duplication.
 					src.typ = dest.typ
 					src.findex = dest.findex
 					src.level = level
 					n.gen = nop
-				case src.kind == basicLit && !src.rval.IsValid():
+				case src.kind == basicLit:
 					// Assign to nil.
 					src.rval = reflect.New(dest.typ.TypeOf()).Elem()
 				}
+
 				n.typ = dest.typ
 				if sym != nil {
 					sym.typ = n.typ
 					sym.recv = src.recv
 				}
+
 				n.level = level
-				if isMapEntry(dest) {
-					dest.gen = nop // skip getIndexMap
-				}
+
 				if n.anc.kind == constDecl {
 					n.gen = nop
-					n.findex = -1
+					n.findex = notInFrame
 					if sym, _, ok := sc.lookup(dest.ident); ok {
 						sym.kind = constSym
 					}
@@ -644,7 +658,7 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 				if n.child[0].ident == "_" {
 					lc.gen = typeAssertStatus
 				} else {
-					lc.gen = typeAssert2
+					lc.gen = typeAssertLong
 				}
 				n.gen = nop
 			case unaryExpr:
@@ -700,7 +714,7 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 					break
 				}
 			}
-			if c0.rval.IsValid() && c1.rval.IsValid() && !isInterface(n.typ) && constOp[n.action] != nil {
+			if c0.rval.IsValid() && c1.rval.IsValid() && (!isInterface(n.typ)) && constOp[n.action] != nil {
 				n.typ.TypeOf()       // Force compute of reflection type.
 				constOp[n.action](n) // Compute a constant result now rather than during exec.
 			}
@@ -709,7 +723,7 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 				// This operation involved constants, and the result is already computed
 				// by constOp and available in n.rval. Nothing else to do at execution.
 				n.gen = nop
-				n.findex = -1
+				n.findex = notInFrame
 			case n.anc.kind == assignStmt && n.anc.action == aAssign:
 				// To avoid a copy in frame, if the result is to be assigned, store it directly
 				// at the frame location of destination.
@@ -732,7 +746,13 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 			wireChild(n)
 			t := n.child[0].typ
 			switch t.cat {
-			case aliasT, ptrT:
+			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 {
 					n.typ = &itype{cat: valueT, rtype: t.val.rtype.Elem()}
@@ -838,27 +858,47 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 			wireChild(n)
 			switch {
 			case interp.isBuiltinCall(n):
-				err = check.builtin(n.child[0].ident, n, n.child[1:], n.action == aCallSlice)
+				c0 := n.child[0]
+				bname := c0.ident
+				err = check.builtin(bname, n, n.child[1:], n.action == aCallSlice)
 				if err != nil {
 					break
 				}
 
-				n.gen = n.child[0].sym.builtin
-				n.child[0].typ = &itype{cat: builtinT}
+				n.gen = c0.sym.builtin
+				c0.typ = &itype{cat: builtinT}
 				if n.typ, err = nodeType(interp, sc, n); err != nil {
 					return
 				}
 				switch {
 				case n.typ.cat == builtinT:
-					n.findex = -1
+					n.findex = notInFrame
 					n.val = nil
 				case n.anc.kind == returnStmt:
 					// Store result directly to frame output location, to avoid a frame copy.
 					n.findex = 0
+				case bname == "cap" && isInConstOrTypeDecl(n):
+					switch n.child[1].typ.TypeOf().Kind() {
+					case reflect.Array, reflect.Chan:
+						capConst(n)
+					default:
+						err = n.cfgErrorf("cap argument is not an array or channel")
+					}
+					n.findex = notInFrame
+					n.gen = nop
+				case bname == "len" && isInConstOrTypeDecl(n):
+					switch n.child[1].typ.TypeOf().Kind() {
+					case reflect.Array, reflect.Chan, reflect.String:
+						lenConst(n)
+					default:
+						err = n.cfgErrorf("len argument is not an array, channel or string")
+					}
+					n.findex = notInFrame
+					n.gen = nop
 				default:
 					n.findex = sc.add(n.typ)
 				}
-				if op, ok := constBltn[n.child[0].ident]; ok && n.anc.action != aAssign {
+				if op, ok := constBltn[bname]; ok && n.anc.action != aAssign {
 					op(n) // pre-compute non-assigned constant :
 				}
 			case n.child[0].isType(sc):
@@ -892,7 +932,7 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 					n.rval = c1.rval
 				case c1.rval.IsValid() && isConstType(c0.typ):
 					n.gen = nop
-					n.findex = -1
+					n.findex = notInFrame
 					n.typ = c0.typ
 					if c, ok := c1.rval.Interface().(constant.Value); ok {
 						i, _ := constant.Int64Val(constant.ToInt(c))
@@ -955,7 +995,7 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 						}
 					}
 				} else {
-					n.findex = -1
+					n.findex = notInFrame
 				}
 			}
 
@@ -1036,7 +1076,7 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 		case fileStmt:
 			wireChild(n, varDecl)
 			sc = sc.pop()
-			n.findex = -1
+			n.findex = notInFrame
 
 		case forStmt0: // for {}
 			body := n.child[0]
@@ -1494,6 +1534,9 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 				// Resolve source package symbol
 				if sym, ok := interp.srcPkg[pkg][name]; ok {
 					n.findex = sym.index
+					if sym.global {
+						n.level = globalFrame
+					}
 					n.val = sym.node
 					n.gen = nop
 					n.action = aGetSym
@@ -1508,7 +1551,7 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 				if n.child[0].isType(sc) {
 					// Handle method as a function with receiver in 1st argument
 					n.val = m
-					n.findex = -1
+					n.findex = notInFrame
 					n.gen = nop
 					n.typ = &itype{}
 					*n.typ = *m.typ
@@ -1821,7 +1864,7 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 			switch {
 			case n.rval.IsValid():
 				n.gen = nop
-				n.findex = -1
+				n.findex = notInFrame
 			case n.anc.kind == assignStmt && n.anc.action == aAssign:
 				dest := n.anc.child[childPos(n)-n.anc.nright]
 				n.typ = dest.typ
@@ -1843,11 +1886,13 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 					return
 				}
 			}
+
 			for _, c := range n.child[:l] {
 				var index int
 				if sc.global {
 					// Global object allocation is already performed in GTA.
 					index = sc.sym[c.ident].index
+					c.level = globalFrame
 				} else {
 					index = sc.add(n.typ)
 					sc.sym[c.ident] = &symbol{index: index, kind: varSym, typ: n.typ}
@@ -1874,8 +1919,15 @@ func compDefineX(sc *scope, n *node) error {
 		if err != nil {
 			return err
 		}
+		for funtype.cat == valueT && funtype.val != nil {
+			// Retrieve original interpreter type from a wrapped function.
+			// Struct fields of function types are always wrapped in valueT to ensure
+			// their possible use in runtime. In that case, the val field retains the
+			// original interpreter type, which is used now.
+			funtype = funtype.val
+		}
 		if funtype.cat == valueT {
-			// Handle functions imported from runtime
+			// Handle functions imported from runtime.
 			for i := 0; i < funtype.rtype.NumOut(); i++ {
 				types = append(types, &itype{cat: valueT, rtype: funtype.rtype.Out(i)})
 			}
@@ -1899,7 +1951,7 @@ func compDefineX(sc *scope, n *node) error {
 		if n.child[0].ident == "_" {
 			n.child[l].gen = typeAssertStatus
 		} else {
-			n.child[l].gen = typeAssert2
+			n.child[l].gen = typeAssertLong
 		}
 		types = append(types, n.child[l].child[1].typ, sc.getType("bool"))
 		n.gen = nop
@@ -2298,6 +2350,20 @@ func isRecursiveField(n *node) bool {
 	return false
 }
 
+func isInConstOrTypeDecl(n *node) bool {
+	anc := n.anc
+	for anc != nil {
+		switch anc.kind {
+		case constDecl, typeDecl:
+			return true
+		case varDecl, funcDecl:
+			return false
+		}
+		anc = anc.anc
+	}
+	return false
+}
+
 // isNewDefine returns true if node refers to a new definition.
 func isNewDefine(n *node, sc *scope) bool {
 	if n.ident == "_" {
@@ -2457,6 +2523,10 @@ func compositeGenerator(n *node, typ *itype, rtyp reflect.Type) (gen bltnGenerat
 		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
+		}
 		switch k := rtyp.Kind(); k {
 		case reflect.Struct:
 			if n.nleft == 1 {
@@ -2469,6 +2539,8 @@ func compositeGenerator(n *node, typ *itype, rtyp reflect.Type) (gen bltnGenerat
 			gen = compositeBinMap
 		case reflect.Ptr:
 			gen = compositeGenerator(n, typ, n.typ.val.rtype)
+		case reflect.Slice:
+			gen = compositeBinSlice
 		default:
 			log.Panic(n.cfgErrorf("compositeGenerator not implemented for type kind: %s", k))
 		}
@@ -2504,28 +2576,22 @@ func isValueUntyped(v reflect.Value) bool {
 	if v.CanSet() {
 		return false
 	}
-	t := v.Type()
-	if t.Implements(constVal) {
-		return true
-	}
-	return t.String() == t.Kind().String()
+	return v.Type().Implements(constVal)
 }
 
 // isArithmeticAction returns true if the node action is an arithmetic operator.
 func isArithmeticAction(n *node) bool {
 	switch n.action {
-	case aAdd, aAnd, aAndNot, aBitNot, aMul, aQuo, aRem, aShl, aShr, aSub, aXor:
+	case aAdd, aAnd, aAndNot, aBitNot, aMul, aNeg, aOr, aPos, aQuo, aRem, aShl, aShr, aSub, aXor:
 		return true
-	default:
-		return false
 	}
+	return false
 }
 
 func isBoolAction(n *node) bool {
 	switch n.action {
 	case aEqual, aGreater, aGreaterEqual, aLand, aLor, aLower, aLowerEqual, aNot, aNotEqual:
 		return true
-	default:
-		return false
 	}
+	return false
 }

interp/gta.go

@@ -27,6 +27,7 @@ func (interp *Interpreter) gta(root *node, rpath, importPath string) ([]*node, e
 			// values which may be used in further declarations.
 			if _, err = interp.cfg(n, importPath); err != nil {
 				// No error processing here, to allow recovery in subtree nodes.
+				// TODO(marc): check for a non recoverable error and return it for better diagnostic.
 				err = nil
 			}
 
@@ -115,6 +116,7 @@ func (interp *Interpreter) gta(root *node, rpath, importPath string) ([]*node, e
 					sc.sym[c.ident] = &symbol{index: sc.add(n.typ), kind: varSym, global: true, typ: n.typ, node: n}
 					continue
 				}
+				c.level = globalFrame
 
 				// redeclaration error
 				if sym.typ.node != nil && sym.typ.node.anc != nil {
@@ -253,10 +255,11 @@ func (interp *Interpreter) gta(root *node, rpath, importPath string) ([]*node, e
 				return false
 			}
 
-			if n.child[1].kind == identExpr {
+			switch n.child[1].kind {
+			case identExpr, selectorExpr:
 				n.typ = &itype{cat: aliasT, val: typ, name: typeName, path: importPath, field: typ.field, incomplete: typ.incomplete, scope: sc, node: n.child[0]}
 				copy(n.typ.method, typ.method)
-			} else {
+			default:
 				n.typ = typ
 				n.typ.name = typeName
 				n.typ.path = importPath
@@ -317,7 +320,50 @@ func (interp *Interpreter) gtaRetry(nodes []*node, importPath string) error {
 	}
 
 	if len(revisit) > 0 {
-		return revisit[0].cfgErrorf("constant definition loop")
+		n := revisit[0]
+		if n.kind == typeSpec {
+			if err := definedType(n.typ); err != nil {
+				return err
+			}
+		}
+		return n.cfgErrorf("constant definition loop")
+	}
+	return nil
+}
+
+func definedType(typ *itype) error {
+	if !typ.incomplete {
+		return nil
+	}
+	switch typ.cat {
+	case interfaceT, structT:
+		for _, f := range typ.field {
+			if err := definedType(f.typ); err != nil {
+				return err
+			}
+		}
+	case funcT:
+		for _, t := range typ.arg {
+			if err := definedType(t); err != nil {
+				return err
+			}
+		}
+		for _, t := range typ.ret {
+			if err := definedType(t); err != nil {
+				return err
+			}
+		}
+	case mapT:
+		if err := definedType(typ.key); err != nil {
+			return err
+		}
+		fallthrough
+	case aliasT, arrayT, chanT, chanSendT, chanRecvT, ptrT, variadicT:
+		if err := definedType(typ.val); err != nil {
+			return err
+		}
+	case nilT:
+		return typ.node.cfgErrorf("undefined: %s", typ.node.ident)
 	}
 	return nil
 }

interp/interp.go

@@ -65,7 +65,8 @@ type frame struct {
 	// Located at start of struct to ensure proper aligment.
 	id uint64
 
-	anc  *frame          // ancestor frame (global space)
+	root *frame          // global space
+	anc  *frame          // ancestor frame (caller space)
 	data []reflect.Value // values
 
 	mutex     sync.RWMutex
@@ -74,14 +75,17 @@ type frame struct {
 	done      reflect.SelectCase // for cancellation of channel operations
 }
 
-func newFrame(anc *frame, len int, id uint64) *frame {
+func newFrame(anc *frame, length int, id uint64) *frame {
 	f := &frame{
 		anc:  anc,
-		data: make([]reflect.Value, len),
+		data: make([]reflect.Value, length),
 		id:   id,
 	}
-	if anc != nil {
+	if anc == nil {
+		f.root = f
+	} else {
 		f.done = anc.done
+		f.root = anc.root
 	}
 	return f
 }
@@ -93,6 +97,7 @@ func (f *frame) clone() *frame {
 	defer f.mutex.RUnlock()
 	return &frame{
 		anc:       f.anc,
+		root:      f.root,
 		data:      f.data,
 		deferred:  f.deferred,
 		recovered: f.recovered,
@@ -239,7 +244,7 @@ type Options struct {
 func New(options Options) *Interpreter {
 	i := Interpreter{
 		opt:      opt{context: build.Default},
-		frame:    &frame{data: []reflect.Value{}},
+		frame:    newFrame(nil, 0, 0),
 		fset:     token.NewFileSet(),
 		universe: initUniverse(),
 		scopes:   map[string]*scope{},

interp/interp_eval_test.go

@@ -89,6 +89,7 @@ func TestOpVarConst(t *testing.T) {
 		{src: "b := uint(5); a+b", res: "15"},
 		{src: "b := uint(5); b+a", res: "15"},
 		{src: "b := uint(5); b>a", res: "false"},
+		{src: "const maxlen = cap(aa); var aa = []int{1,2}", err: "1:20: constant definition loop"},
 	})
 }
 
@@ -102,6 +103,16 @@ func TestEvalStar(t *testing.T) {
 
 func TestEvalAssign(t *testing.T) {
 	i := interp.New(interp.Options{})
+	i.Use(interp.Exports{
+		"testpkg": {
+			"val": reflect.ValueOf(int64(11)),
+		},
+	})
+	_, e := i.Eval(`import "testpkg"`)
+	if e != nil {
+		t.Fatal(e)
+	}
+
 	runTests(t, i, []testCase{
 		{src: `a := "Hello"; a += " world"`, res: "Hello world"},
 		{src: `b := "Hello"; b += 1`, err: "1:42: invalid operation: mismatched types string and int"},
@@ -110,6 +121,8 @@ func TestEvalAssign(t *testing.T) {
 		{src: "f := int64(3.2)", err: "1:39: cannot convert expression of type float64 to type int64"},
 		{src: "g := 1; g <<= 8", res: "256"},
 		{src: "h := 1; h >>= 8", res: "0"},
+		{src: "i := 1; j := &i; (*j) = 2", res: "2"},
+		{src: "i64 := testpkg.val; i64 == 11", res: "true"},
 	})
 }
 
@@ -444,22 +457,19 @@ func TestEvalSliceExpression(t *testing.T) {
 		{src: `a := []int{0,1,2}[:]`, res: "[0 1 2]"},
 		{src: `a := []int{0,1,2,3}[1:3:4]`, res: "[1 2]"},
 		{src: `a := []int{0,1,2,3}[:3:4]`, res: "[0 1 2]"},
-		{src: `ar := [3]int{0,1,2}
-			   a := ar[1:3]`, res: "[1 2]"},
+		{src: `ar := [3]int{0,1,2}; a := ar[1:3]`, res: "[1 2]"},
 		{src: `a := (&[3]int{0,1,2})[1:3]`, res: "[1 2]"},
 		{src: `a := (&[3]int{0,1,2})[1:3]`, res: "[1 2]"},
 		{src: `s := "hello"[1:3]`, res: "el"},
-		{src: `str := "hello"
-			   s := str[1:3]`, res: "el"},
+		{src: `str := "hello"; s := str[1:3]`, res: "el"},
 		{src: `a := int(1)[0:1]`, err: "1:33: cannot slice type int"},
-		{src: `a := ([3]int{0,1,2})[1:3]`, err: "1:33: cannot slice type [3]int"},
 		{src: `a := (&[]int{0,1,2,3})[1:3]`, err: "1:33: cannot slice type *[]int"},
 		{src: `a := "hello"[1:3:4]`, err: "1:45: invalid operation: 3-index slice of string"},
-		{src: `ar := [3]int{0,1,2}
-			   a := ar[:4]`, err: "2:16: index int is out of bounds"},
+		{src: `ar := [3]int{0,1,2}; a := ar[:4]`, err: "1:58: index int is out of bounds"},
 		{src: `a := []int{0,1,2,3}[1::4]`, err: "1:49: 2nd index required in 3-index slice"},
 		{src: `a := []int{0,1,2,3}[1:3:]`, err: "1:51: 3rd index required in 3-index slice"},
 		{src: `a := []int{0,1,2}[3:1]`, err: "invalid index values, must be low <= high <= max"},
+		{pre: func() { eval(t, i, `type Str = string; var r Str = "truc"`) }, src: `r[1]`, res: "114"},
 	})
 }
 
@@ -497,12 +507,19 @@ func TestEvalMethod(t *testing.T) {
 			Hello() string
 		}
 
+		type Hey interface {
+			Hello() string
+		}
+
 		func (r *Root) Hello() string { return "Hello " + r.Name }
 
 		var r = Root{"R"}
 		var o = One{r}
-		var root interface{} = &Root{Name: "test1"}
-		var one interface{} = &One{Root{Name: "test2"}}
+		// TODO(mpl): restore empty interfaces when type assertions work (again) on them.
+		// var root interface{} = &Root{Name: "test1"}
+		// var one interface{} = &One{Root{Name: "test2"}}
+		var root Hey = &Root{Name: "test1"}
+		var one Hey = &One{Root{Name: "test2"}}
 	`)
 	runTests(t, i, []testCase{
 		{src: "r.Hello()", res: "Hello R"},
@@ -743,6 +760,8 @@ func TestEvalWithContext(t *testing.T) {
 }
 
 func runTests(t *testing.T, i *interp.Interpreter, tests []testCase) {
+	t.Helper()
+
 	for _, test := range tests {
 		t.Run(test.desc, func(t *testing.T) {
 			if test.skip != "" {
@@ -772,6 +791,8 @@ func eval(t *testing.T, i *interp.Interpreter, src string) reflect.Value {
 }
 
 func assertEval(t *testing.T, i *interp.Interpreter, src, expectedError, expectedRes string) {
+	t.Helper()
+
 	res, err := i.Eval(src)
 
 	if expectedError != "" {
@@ -1150,6 +1171,8 @@ func TestConcurrentComposite2(t *testing.T) {
 }
 
 func testConcurrentComposite(t *testing.T, filePath string) {
+	t.Helper()
+
 	if testing.Short() {
 		return
 	}

interp/interp_export_test.go

@@ -32,7 +32,7 @@ func Hi(h Helloer) {
 // The method calls will be forwarded to the interpreter.
 //
 // Only the Wrap type definition needs to be exported to the interpreter (not
-// the interfaces and methods  definitions)
+// the interfaces and methods definitions).
 //
 type Wrap struct {
 	DoHello func() // related to the Hello() method.

interp/interp_file_test.go

@@ -37,6 +37,8 @@ func TestFile(t *testing.T) {
 }
 
 func runCheck(t *testing.T, p string) {
+	t.Helper()
+
 	wanted, goPath, errWanted := wantedFromComment(p)
 	if wanted == "" {
 		t.Skip(p, "has no comment 'Output:' or 'Error:'")

interp/op.go

@@ -1,6 +1,6 @@
 package interp
 
-// Code generated by 'go run ../internal/genop/genop.go'. DO NOT EDIT.
+// Code generated by 'go run ../internal/cmd/genop/genop.go'. DO NOT EDIT.
 
 import (
 	"go/constant"
@@ -46,14 +46,54 @@ func add(n *node) {
 		case c0.rval.IsValid():
 			i := vInt(c0.rval)
 			v1 := genValueInt(c1)
+
+			if n.typ.cat != interfaceT || len(n.typ.field) > 0 {
+				n.exec = func(f *frame) bltn {
+					_, j := v1(f)
+					dest(f).SetInt(i + j)
+					return next
+				}
+				return
+			}
+			var valf func(sum int64) reflect.Value
+			// TODO: cover other int types, and actually other numbers, and even all
+			// relevant operations, not just add.
+			switch typ.Kind() {
+			case reflect.Int:
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(int(sum)) }
+			case reflect.Int32:
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(int32(sum)) }
+			default: // int64
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(sum) }
+			}
 			n.exec = func(f *frame) bltn {
 				_, j := v1(f)
-				dest(f).SetInt(i + j)
+				dest(f).Set(valf(i + j))
 				return next
 			}
 		case c1.rval.IsValid():
 			v0 := genValueInt(c0)
 			j := vInt(c1.rval)
+
+			var valf func(sum int64) reflect.Value
+			// TODO: cover other int types, and actually other numbers, and even all
+			// relevant operations, not just add.
+			switch typ.Kind() {
+			case reflect.Int:
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(int(sum)) }
+			case reflect.Int32:
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(int32(sum)) }
+			default: // int64
+				valf = func(sum int64) reflect.Value { return reflect.ValueOf(sum) }
+			}
+			if wantEmptyInterface(n) {
+				n.exec = func(f *frame) bltn {
+					_, i := v0(f)
+					dest(f).Set(valf(i + j))
+					return next
+				}
+				return
+			}
 			n.exec = func(f *frame) bltn {
 				_, i := v0(f)
 				dest(f).SetInt(i + j)
@@ -253,7 +293,7 @@ func andConst(n *node) {
 	n.rval = reflect.New(t).Elem()
 	switch {
 	case isConst:
-		v := constant.BinaryOp(vConstantValue(v0), token.AND, vConstantValue(v1))
+		v := constant.BinaryOp(constant.ToInt(vConstantValue(v0)), token.AND, constant.ToInt(vConstantValue(v1)))
 		n.rval.Set(reflect.ValueOf(v))
 	case isUint(t):
 		n.rval.SetUint(vUint(v0) & vUint(v1))
@@ -338,7 +378,7 @@ func andNotConst(n *node) {
 	n.rval = reflect.New(t).Elem()
 	switch {
 	case isConst:
-		v := constant.BinaryOp(vConstantValue(v0), token.AND_NOT, vConstantValue(v1))
+		v := constant.BinaryOp(constant.ToInt(vConstantValue(v0)), token.AND_NOT, constant.ToInt(vConstantValue(v1)))
 		n.rval.Set(reflect.ValueOf(v))
 	case isUint(t):
 		n.rval.SetUint(vUint(v0) &^ vUint(v1))
@@ -564,7 +604,7 @@ func orConst(n *node) {
 	n.rval = reflect.New(t).Elem()
 	switch {
 	case isConst:
-		v := constant.BinaryOp(vConstantValue(v0), token.OR, vConstantValue(v1))
+		v := constant.BinaryOp(constant.ToInt(vConstantValue(v0)), token.OR, constant.ToInt(vConstantValue(v1)))
 		n.rval.Set(reflect.ValueOf(v))
 	case isUint(t):
 		n.rval.SetUint(vUint(v0) | vUint(v1))
@@ -799,7 +839,7 @@ func remConst(n *node) {
 	n.rval = reflect.New(t).Elem()
 	switch {
 	case isConst:
-		v := constant.BinaryOp(vConstantValue(v0), token.REM, vConstantValue(v1))
+		v := constant.BinaryOp(constant.ToInt(vConstantValue(v0)), token.REM, constant.ToInt(vConstantValue(v1)))
 		n.rval.Set(reflect.ValueOf(v))
 	case isUint(t):
 		n.rval.SetUint(vUint(v0) % vUint(v1))
@@ -1195,7 +1235,7 @@ func xorConst(n *node) {
 	n.rval = reflect.New(t).Elem()
 	switch {
 	case isConst:
-		v := constant.BinaryOp(vConstantValue(v0), token.XOR, vConstantValue(v1))
+		v := constant.BinaryOp(constant.ToInt(vConstantValue(v0)), token.XOR, constant.ToInt(vConstantValue(v1)))
 		n.rval.Set(reflect.ValueOf(v))
 	case isUint(t):
 		n.rval.SetUint(vUint(v0) ^ vUint(v1))

interp/scope.go

@@ -130,6 +130,9 @@ func (s *scope) lookup(ident string) (*symbol, int, bool) {
 	level := s.level
 	for {
 		if sym, ok := s.sym[ident]; ok {
+			if sym.global {
+				return sym, globalFrame, true
+			}
 			return sym, level - s.level, true
 		}
 		if s.anc == nil {

interp/src.go

@@ -33,12 +33,12 @@ func (interp *Interpreter) importSrc(rPath, importPath string, skipTest bool) (s
 			rPath = "."
 		}
 		dir = filepath.Join(filepath.Dir(interp.name), rPath, importPath)
-	} else if dir, rPath, err = pkgDir(interp.context.GOPATH, rPath, importPath); err != nil {
+	} else if dir, rPath, err = interp.pkgDir(interp.context.GOPATH, rPath, importPath); err != nil {
 		// Try again, assuming a root dir at the source location.
 		if rPath, err = interp.rootFromSourceLocation(); err != nil {
 			return "", err
 		}
-		if dir, rPath, err = pkgDir(interp.context.GOPATH, rPath, importPath); err != nil {
+		if dir, rPath, err = interp.pkgDir(interp.context.GOPATH, rPath, importPath); err != nil {
 			return "", err
 		}
 	}
@@ -181,7 +181,7 @@ func (interp *Interpreter) rootFromSourceLocation() (string, error) {
 
 // pkgDir returns the absolute path in filesystem for a package given its import path
 // and the root of the subtree dependencies.
-func pkgDir(goPath string, root, importPath string) (string, string, error) {
+func (interp *Interpreter) pkgDir(goPath string, root, importPath string) (string, string, error) {
 	rPath := filepath.Join(root, "vendor")
 	dir := filepath.Join(goPath, "src", rPath, importPath)
 
@@ -196,6 +196,9 @@ func pkgDir(goPath string, root, importPath string) (string, string, error) {
 	}
 
 	if len(root) == 0 {
+		if interp.context.GOPATH == "" {
+			return "", "", fmt.Errorf("unable to find source related to: %q. Either the GOPATH environment variable, or the Interpreter.Options.GoPath needs to be set", importPath)
+		}
 		return "", "", fmt.Errorf("unable to find source related to: %q", importPath)
 	}
 
@@ -205,7 +208,7 @@ func pkgDir(goPath string, root, importPath string) (string, string, error) {
 		return "", "", err
 	}
 
-	return pkgDir(goPath, prevRoot, importPath)
+	return interp.pkgDir(goPath, prevRoot, importPath)
 }
 
 const vendor = "vendor"

interp/src_test.go

@@ -161,6 +161,8 @@ func Test_pkgDir(t *testing.T) {
 		},
 	}
 
+	interp := &Interpreter{}
+
 	for _, test := range testCases {
 		test := test
 		t.Run(test.desc, func(t *testing.T) {
@@ -178,7 +180,7 @@ func Test_pkgDir(t *testing.T) {
 				}
 			}
 
-			dir, rPath, err := pkgDir(goPath, test.root, test.path)
+			dir, rPath, err := interp.pkgDir(goPath, test.root, test.path)
 			if err != nil {
 				t.Fatal(err)
 			}

interp/type.go

@@ -109,7 +109,7 @@ type itype struct {
 	cat         tcat          // Type category
 	field       []structField // Array of struct fields if structT or interfaceT
 	key         *itype        // Type of key element if MapT or nil
-	val         *itype        // Type of value element if chanT,chanSendT, chanRecvT, mapT, ptrT, aliasT, arrayT or variadicT
+	val         *itype        // Type of value element if chanT, chanSendT, chanRecvT, mapT, ptrT, aliasT, arrayT or variadicT
 	recv        *itype        // Receiver type for funcT or nil
 	arg         []*itype      // Argument types if funcT or nil
 	ret         []*itype      // Return types if funcT or nil
@@ -198,7 +198,7 @@ func nodeType(interp *Interpreter, sc *scope, n *node) (*itype, error) {
 			if sym.kind != constSym {
 				return nil, c0.cfgErrorf("non-constant array bound %q", c0.ident)
 			}
-			if sym.typ == nil || sym.typ.cat != intT {
+			if sym.typ == nil || sym.typ.cat != intT || !sym.rval.IsValid() {
 				t.incomplete = true
 				break
 			}
@@ -274,8 +274,33 @@ func nodeType(interp *Interpreter, sc *scope, n *node) (*itype, error) {
 				t = t1
 			}
 		}
+
+		// Because an empty interface concrete type "mutates" as different values are
+		// assigned to it, we need to make a new itype from scratch everytime a new
+		// assignment is made, and not let different nodes (of the same variable) share the
+		// same itype. Otherwise they would overwrite each other.
+		if n.anc.kind == assignStmt && isInterface(n.anc.child[0].typ) && len(n.anc.child[0].typ.field) == 0 {
+			// TODO(mpl): do the indexes properly for multiple assignments on the same line.
+			// Also, maybe we should use nodeType to figure out dt.cat? but isn't it always
+			// gonna be an interfaceT anyway?
+			dt := new(itype)
+			dt.cat = interfaceT
+			val := new(itype)
+			val.cat = t.cat
+			dt.val = val
+			// TODO(mpl): do the indexes properly for multiple assignments on the same line.
+			// Also, maybe we should use nodeType to figure out dt.cat? but isn't it always
+			// gonna be an interfaceT anyway?
+			n.anc.child[0].typ = dt
+			// TODO(mpl): not sure yet whether we should do that last step. It doesn't seem
+			// to change anything either way though.
+			// t = dt
+			break
+		}
+
 		// If the node is to be assigned or returned, the node type is the destination type.
 		dt := t
+
 		switch a := n.anc; {
 		case a.kind == defineStmt && len(a.child) > a.nleft+a.nright:
 			if dt, err = nodeType(interp, sc, a.child[a.nleft]); err != nil {
@@ -449,6 +474,9 @@ func nodeType(interp *Interpreter, sc *scope, n *node) (*itype, error) {
 			}
 		}
 		t = sym.typ
+		if t.incomplete && t.cat == aliasT && t.val != nil && t.val.cat != nilT {
+			t.incomplete = false
+		}
 		if t.incomplete && t.node != n {
 			m := t.method
 			if t, err = nodeType(interp, sc, t.node); err != nil {
@@ -557,7 +585,8 @@ func nodeType(interp *Interpreter, sc *scope, n *node) (*itype, error) {
 			if v, ok := pkg[name]; ok {
 				t.cat = valueT
 				t.rtype = v.Type()
-				if isBinType(v) { // a bin type is encoded as a pointer on nil value
+				if isBinType(v) {
+					// A bin type is encoded as a pointer on a typed nil value.
 					t.rtype = t.rtype.Elem()
 				}
 			} else {
@@ -736,7 +765,7 @@ func (t *itype) finalize() (*itype, error) {
 }
 
 // ReferTo returns true if the type contains a reference to a
-// full type name. It allows to asses a type recursive status.
+// full type name. It allows to assess a type recursive status.
 func (t *itype) referTo(name string, seen map[*itype]bool) bool {
 	if t.path+"/"+t.name == name {
 		return true
@@ -878,13 +907,19 @@ func isComplete(t *itype, visited map[string]bool) bool {
 	}
 	name := t.path + "/" + t.name
 	if visited[name] {
-		return !t.incomplete
+		return true
 	}
 	if t.name != "" {
 		visited[name] = true
 	}
 	switch t.cat {
-	case aliasT, arrayT, chanT, chanRecvT, chanSendT, ptrT:
+	case aliasT:
+		if t.val != nil && t.val.cat != nilT {
+			// A type aliased to a partially defined type is considered complete, to allow recursivity.
+			return true
+		}
+		fallthrough
+	case arrayT, chanT, chanRecvT, chanSendT, ptrT:
 		return isComplete(t.val, visited)
 	case funcT:
 		complete := true
@@ -898,6 +933,8 @@ func isComplete(t *itype, visited map[string]bool) bool {
 	case interfaceT, structT:
 		complete := true
 		for _, f := range t.field {
+			// Field implicit type names must be marked as visited, to break false circles.
+			visited[f.typ.path+"/"+f.typ.name] = true
 			complete = complete && isComplete(f.typ, visited)
 		}
 		return complete
@@ -1402,7 +1439,7 @@ func (t *itype) refType(defined map[string]*itype, wrapRecursive bool) reflect.T
 		t.rtype = reflect.TypeOf(new(error)).Elem()
 	case funcT:
 		if t.name != "" {
-			defined[name] = t
+			defined[name] = t // TODO(marc): make sure that key is name and not t.name.
 		}
 		variadic := false
 		in := make([]reflect.Type, len(t.arg))
@@ -1423,10 +1460,11 @@ func (t *itype) refType(defined map[string]*itype, wrapRecursive bool) reflect.T
 		t.rtype = reflect.PtrTo(t.val.refType(defined, wrapRecursive))
 	case structT:
 		if t.name != "" {
-			if defined[name] != nil {
+			// Check against local t.name and not name to catch recursive type definitions.
+			if defined[t.name] != nil {
 				recursive = true
 			}
-			defined[name] = t
+			defined[t.name] = t
 		}
 		var fields []reflect.StructField
 		// TODO(mpl): make Anonymous work for recursive types too. Maybe not worth the
@@ -1474,7 +1512,14 @@ func (t *itype) frameType() (r reflect.Type) {
 	case funcT:
 		r = reflect.TypeOf((*node)(nil))
 	case interfaceT:
+		if len(t.field) == 0 {
+			// empty interface, do not wrap it
+			r = reflect.TypeOf((*interface{})(nil)).Elem()
+			break
+		}
 		r = reflect.TypeOf((*valueInterface)(nil)).Elem()
+	case ptrT:
+		r = reflect.PtrTo(t.val.frameType())
 	default:
 		r = t.TypeOf()
 	}
@@ -1489,10 +1534,25 @@ func (t *itype) implements(it *itype) bool {
 }
 
 // defaultType returns the default type of an untyped type.
-func (t *itype) defaultType() *itype {
+func (t *itype) defaultType(v reflect.Value) *itype {
 	if !t.untyped {
 		return t
 	}
+	// The default type can also be derived from a constant value.
+	if v.IsValid() && t.TypeOf().Implements(constVal) {
+		switch v.Interface().(constant.Value).Kind() {
+		case constant.String:
+			t = untypedString()
+		case constant.Bool:
+			t = untypedBool()
+		case constant.Int:
+			t = untypedInt()
+		case constant.Float:
+			t = untypedFloat()
+		case constant.Complex:
+			t = untypedComplex()
+		}
+	}
 	typ := *t
 	typ.untyped = false
 	return &typ
@@ -1539,7 +1599,7 @@ func hasRecursiveStruct(t *itype, defined map[string]*itype) bool {
 		defined[typ.path+"/"+typ.name] = typ
 
 		for _, f := range typ.field {
-			if hasRecursiveStruct(f.typ, defined) {
+			if hasRecursiveStruct(f.typ, copyDefined(defined)) {
 				return true
 			}
 		}
@@ -1612,6 +1672,10 @@ func isInterfaceSrc(t *itype) bool {
 	return t.cat == interfaceT || (t.cat == aliasT && isInterfaceSrc(t.val))
 }
 
+func isInterfaceBin(t *itype) bool {
+	return t.cat == valueT && t.rtype.Kind() == reflect.Interface
+}
+
 func isInterface(t *itype) bool {
 	return isInterfaceSrc(t) || t.TypeOf() != nil && t.TypeOf().Kind() == reflect.Interface
 }

interp/typecheck.go

@@ -37,7 +37,7 @@ func (check typecheck) assignment(n *node, typ *itype, context string) error {
 			if typ == nil && n.typ.cat == nilT {
 				return n.cfgErrorf("use of untyped nil in %s", context)
 			}
-			typ = n.typ.defaultType()
+			typ = n.typ.defaultType(n.rval)
 		}
 		if err := check.convertUntyped(n, typ); err != nil {
 			return err
@@ -65,7 +65,7 @@ func (check typecheck) assignExpr(n, dest, src *node) error {
 		isConst := n.anc.kind == constDecl
 		if !isConst {
 			// var operations must be typed
-			dest.typ = dest.typ.defaultType()
+			dest.typ = dest.typ.defaultType(src.rval)
 		}
 
 		return check.assignment(src, dest.typ, "assignment")
@@ -499,9 +499,7 @@ func (check typecheck) sliceExpr(n *node) error {
 	case reflect.Array:
 		valid = true
 		l = t.Len()
-		if c.kind != indexExpr && c.kind != selectorExpr && (c.sym == nil || c.sym.kind != varSym) {
-			return c.cfgErrorf("cannot slice type %s", c.typ.id())
-		}
+		// TODO(marc): check addressable status of array object (i.e. composite arrays are not).
 	case reflect.Slice:
 		valid = true
 	case reflect.Ptr:
@@ -638,7 +636,7 @@ func (check typecheck) conversion(n *node, typ *itype) error {
 		return nil
 	}
 	if isInterface(typ) || !isConstType(typ) {
-		typ = n.typ.defaultType()
+		typ = n.typ.defaultType(n.rval)
 	}
 	return check.convertUntyped(n, typ)
 }
@@ -1039,9 +1037,8 @@ func (check typecheck) convertUntyped(n *node, typ *itype) error {
 		if len(n.typ.methods()) > 0 { // untyped cannot be set to iface
 			return convErr
 		}
-		ityp = n.typ.defaultType()
+		ityp = n.typ.defaultType(n.rval)
 		rtyp = ntyp
-
 	case isArray(typ) || isMap(typ) || isChan(typ) || isFunc(typ) || isPtr(typ):
 		// TODO(nick): above we are acting on itype, but really it is an rtype check. This is not clear which type
 		// 		 	   plain we are in. Fix this later.

interp/value.go

@@ -5,8 +5,15 @@ import (
 	"reflect"
 )
 
+const (
+	notInFrame  = -1 // value of node.findex for literal values (not in frame)
+	globalFrame = -1 // value of node.level for global symbols
+)
+
 func valueGenerator(n *node, i int) func(*frame) reflect.Value {
 	switch n.level {
+	case globalFrame:
+		return func(f *frame) reflect.Value { return valueOf(f.root.data, i) }
 	case 0:
 		return func(f *frame) reflect.Value { return valueOf(f.data, i) }
 	case 1:
@@ -33,6 +40,30 @@ func valueOf(data []reflect.Value, i int) reflect.Value {
 	return reflect.Value{}
 }
 
+func genValueBinMethodOnInterface(n *node, defaultGen func(*frame) reflect.Value) func(*frame) reflect.Value {
+	if n == nil || n.child == nil || n.child[0] == nil ||
+		n.child[0].child == nil || n.child[0].child[0] == nil {
+		return defaultGen
+	}
+	if n.child[0].child[1] == nil || n.child[0].child[1].ident == "" {
+		return defaultGen
+	}
+	value0 := genValue(n.child[0].child[0])
+
+	return func(f *frame) reflect.Value {
+		val, ok := value0(f).Interface().(valueInterface)
+		if !ok {
+			return defaultGen(f)
+		}
+		typ := val.node.typ
+		if typ.node != nil || typ.cat != valueT {
+			return defaultGen(f)
+		}
+		meth, _ := typ.rtype.MethodByName(n.child[0].child[1].ident)
+		return meth.Func
+	}
+}
+
 func genValueRecvIndirect(n *node) func(*frame) reflect.Value {
 	v := genValueRecv(n)
 	return func(f *frame) reflect.Value { return v(f).Elem() }
@@ -55,6 +86,35 @@ func genValueRecv(n *node) func(*frame) reflect.Value {
 	}
 }
 
+func genValueBinRecv(n *node, recv *receiver) func(*frame) reflect.Value {
+	value := genValue(n)
+	binValue := genValue(recv.node)
+
+	v := func(f *frame) reflect.Value {
+		if def, ok := value(f).Interface().(*node); ok {
+			if def != nil && def.recv != nil && def.recv.val.IsValid() {
+				return def.recv.val
+			}
+		}
+
+		ival, _ := binValue(f).Interface().(valueInterface)
+		return ival.value
+	}
+
+	fi := recv.index
+	if len(fi) == 0 {
+		return v
+	}
+
+	return func(f *frame) reflect.Value {
+		r := v(f)
+		if r.Kind() == reflect.Ptr {
+			r = r.Elem()
+		}
+		return r.FieldByIndex(fi)
+	}
+}
+
 func genValueRecvInterfacePtr(n *node) func(*frame) reflect.Value {
 	v := genValue(n.recv.node)
 	fi := n.recv.index
@@ -118,18 +178,16 @@ func genValue(n *node) func(*frame) reflect.Value {
 			return func(f *frame) reflect.Value { return v }
 		}
 		if n.sym != nil {
-			if n.sym.index < 0 {
+			i := n.sym.index
+			if i < 0 {
 				return genValue(n.sym.node)
 			}
-			i := n.sym.index
 			if n.sym.global {
-				return func(f *frame) reflect.Value {
-					return n.interp.frame.data[i]
-				}
+				return func(f *frame) reflect.Value { return f.root.data[i] }
 			}
 			return valueGenerator(n, i)
 		}
-		if n.findex < 0 {
+		if n.findex == notInFrame {
 			var v reflect.Value
 			if w, ok := n.val.(reflect.Value); ok {
 				v = w
@@ -163,21 +221,25 @@ func genValueRangeArray(n *node) func(*frame) reflect.Value {
 			return value(f).Elem()
 		}
 	case n.typ.val != nil && n.typ.val.cat == interfaceT:
-		return func(f *frame) reflect.Value {
-			val := value(f)
-			v := []valueInterface{}
-			for i := 0; i < val.Len(); i++ {
-				switch av := val.Index(i).Interface().(type) {
-				case []valueInterface:
-					v = append(v, av...)
-				case valueInterface:
-					v = append(v, av)
-				default:
-					panic(n.cfgErrorf("invalid type %v", val.Index(i).Type()))
+		if len(n.typ.val.field) > 0 {
+			return func(f *frame) reflect.Value {
+				val := value(f)
+				v := []valueInterface{}
+				for i := 0; i < val.Len(); i++ {
+					switch av := val.Index(i).Interface().(type) {
+					case []valueInterface:
+						v = append(v, av...)
+					case valueInterface:
+						v = append(v, av)
+					default:
+						panic(n.cfgErrorf("invalid type %v", val.Index(i).Type()))
+					}
 				}
+				return reflect.ValueOf(v)
 			}
-			return reflect.ValueOf(v)
 		}
+		// empty interface, do not wrap.
+		fallthrough
 	default:
 		return func(f *frame) reflect.Value {
 			// This is necessary to prevent changes in the returned
@@ -207,6 +269,7 @@ func genValueInterface(n *node) func(*frame) reflect.Value {
 	return func(f *frame) reflect.Value {
 		v := value(f)
 		nod := n
+
 		for v.IsValid() {
 			// traverse interface indirections to find out concrete type
 			vi, ok := v.Interface().(valueInterface)
@@ -216,6 +279,12 @@ func genValueInterface(n *node) func(*frame) reflect.Value {
 			v = vi.value
 			nod = vi.node
 		}
+
+		// empty interface, do not wrap.
+		if nod.typ.cat == interfaceT && len(nod.typ.field) == 0 {
+			return v
+		}
+
 		return reflect.ValueOf(valueInterface{nod, v})
 	}
 }
@@ -226,12 +295,26 @@ func zeroInterfaceValue() reflect.Value {
 	return reflect.ValueOf(valueInterface{n, v})
 }
 
+func wantEmptyInterface(n *node) bool {
+	return n.typ.cat == interfaceT && len(n.typ.field) == 0 ||
+		n.anc.action == aAssign && n.anc.typ.cat == interfaceT && len(n.anc.typ.field) == 0 ||
+		n.anc.kind == returnStmt && n.anc.val.(*node).typ.ret[0].cat == interfaceT && len(n.anc.val.(*node).typ.ret[0].field) == 0
+}
+
 func genValueOutput(n *node, t reflect.Type) func(*frame) reflect.Value {
 	value := genValue(n)
 	switch {
 	case n.anc.action == aAssign && n.anc.typ.cat == interfaceT:
+		if len(n.anc.typ.field) == 0 {
+			// empty interface, do not wrap
+			return value
+		}
 		fallthrough
 	case n.anc.kind == returnStmt && n.anc.val.(*node).typ.ret[0].cat == interfaceT:
+		if len(n.anc.val.(*node).typ.ret[0].field) == 0 {
+			// empty interface, do not wrap
+			return value
+		}
 		// The result of the builtin has to be returned as an interface type.
 		// Wrap it in a valueInterface and return the dereferenced value.
 		return func(f *frame) reflect.Value {
@@ -244,6 +327,17 @@ func genValueOutput(n *node, t reflect.Type) func(*frame) reflect.Value {
 	return value
 }
 
+func valueInterfaceValue(v reflect.Value) reflect.Value {
+	for {
+		vv, ok := v.Interface().(valueInterface)
+		if !ok {
+			break
+		}
+		v = vv.value
+	}
+	return v
+}
+
 func genValueInterfaceValue(n *node) func(*frame) reflect.Value {
 	value := genValue(n)
 
@@ -254,7 +348,7 @@ func genValueInterfaceValue(n *node) func(*frame) reflect.Value {
 			v.Set(zeroInterfaceValue())
 			v = value(f)
 		}
-		return v.Interface().(valueInterface).value
+		return valueInterfaceValue(v)
 	}
 }