internal/reflectlite: add type mirror with reflect test

Add test to check that struct type in reflectlite is mirror of reflect.
Note that the test does not check the field types, only check for number
of fields and field name are the same.

Updates #34486

Change-Id: Id5f9b26d35faec97863dd1fe7e5eab37d4913181
Reviewed-on: https://go-review.googlesource.com/c/go/+/199280
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/internal/reflectlite/reflect_mirror_test.go

+package reflectlite_test
+
+import (
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+)
+
+var typeNames = []string{
+	"rtype",
+	"uncommonType",
+	"arrayType",
+	"chanType",
+	"funcType",
+	"interfaceType",
+	"mapType",
+	"ptrType",
+	"sliceType",
+	"structType",
+}
+
+type visitor struct {
+	m map[string]map[string]bool
+}
+
+func newVisitor() visitor {
+	v := visitor{}
+	v.m = make(map[string]map[string]bool)
+
+	return v
+}
+func (v visitor) filter(name string) bool {
+	for _, typeName := range typeNames {
+		if typeName == name {
+			return true
+		}
+	}
+	return false
+}
+
+func (v visitor) Visit(n ast.Node) ast.Visitor {
+	switch x := n.(type) {
+	case *ast.TypeSpec:
+		if v.filter(x.Name.String()) {
+			if st, ok := x.Type.(*ast.StructType); ok {
+				v.m[x.Name.String()] = make(map[string]bool)
+				for _, field := range st.Fields.List {
+					k := fmt.Sprintf("%s", field.Type)
+					if len(field.Names) > 0 {
+						k = field.Names[0].Name
+					}
+					v.m[x.Name.String()][k] = true
+				}
+			}
+		}
+	}
+	return v
+}
+
+func loadTypes(path, pkgName string, v visitor) {
+	fset := token.NewFileSet()
+
+	filter := func(fi os.FileInfo) bool {
+		return strings.HasSuffix(fi.Name(), ".go")
+	}
+	pkgs, err := parser.ParseDir(fset, path, filter, 0)
+	if err != nil {
+		panic(err)
+	}
+
+	pkg := pkgs[pkgName]
+
+	for _, f := range pkg.Files {
+		ast.Walk(v, f)
+	}
+}
+
+func TestMirrorWithReflect(t *testing.T) {
+	var wg sync.WaitGroup
+	rl, r := newVisitor(), newVisitor()
+
+	for _, tc := range []struct {
+		path, pkg string
+		v         visitor
+	}{
+		{".", "reflectlite", rl},
+		{filepath.Join(runtime.GOROOT(), "src", "reflect"), "reflect", r},
+	} {
+		tc := tc
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			loadTypes(tc.path, tc.pkg, tc.v)
+		}()
+	}
+	wg.Wait()
+
+	if len(rl.m) != len(r.m) {
+		t.Fatalf("number of types mismatch, reflect: %d, reflectlite: %d", len(r.m), len(rl.m))
+	}
+
+	for typName := range r.m {
+		if len(r.m[typName]) != len(rl.m[typName]) {
+			t.Errorf("type %s number of fields mismatch, reflect: %d, reflectlite: %d", typName, len(r.m[typName]), len(rl.m[typName]))
+			continue
+		}
+		for field := range r.m[typName] {
+			if _, ok := rl.m[typName][field]; !ok {
+				t.Errorf(`Field mismatch, reflect have "%s", relectlite does not.`, field)
+			}
+		}
+	}
+}