"20: *ast.Field":      "complex value\n",
	"25: *ast.GenDecl":    "x\nx = 0\nalso associated with x\n",
	"29: *ast.FuncDecl":   "f1\nassociated with f1\nalso associated with f1\n",
	"31: *ast.ExprStmt":   " associated with s1\nalso associated with s1\n",
	"37: *ast.ExprStmt":   "associated with s2\nalso associated with s2\nline comment for s2\n",
	"45: *ast.FuncDecl":   "associated with f2\nf2\n",
	"49: *ast.AssignStmt": "addition\n",

	{"EmptyStmt", `@`},

	{"LabeledStmt", `L@:`},
	{"LabeledStmt", `L@: ;`},
	{"LabeledStmt", `L@: f()`},

	{"BlockStmt", `@{}`},

	// The position of an ExprStmt is the position of the expression.
	{"ExprStmt", `@<-ch`},
	{"ExprStmt", `f@()`},
	{"ExprStmt", `append@(s, 1, 2, 3)`},

	{"SendStmt", `ch @<- x`},

	{"DeclStmt", `@const x = 0`},
	{"DeclStmt", `@const (x = 0)`},
	{"DeclStmt", `@type T int`},

	case *syntax.DeclStmt, *syntax.EmptyStmt, *syntax.SendStmt,
		*syntax.AssignStmt, *syntax.CallStmt:
		// no chance

	case *syntax.LabeledStmt:
		return check.isTerminating(s.Stmt, s.Label.Value)

	case *syntax.ExprStmt:
		// calling the predeclared (possibly parenthesized) panic() function is terminating
		if call, ok := syntax.Unparen(s.X).(*syntax.CallExpr); ok && check.isPanic[call] {
			return true
		}

	case *syntax.ReturnStmt:

		if i := strings.LastIndexByte(s, '.'); i > 0 {
			pkgFuncs[[2]string{s[:i], s[i+1:]}] = true
		}
	}

	nodeFilter := []ast.Node{
		(*ast.ExprStmt)(nil),
	}
	inspect.Preorder(nodeFilter, func(n ast.Node) {
		call, ok := astutil.Unparen(n.(*ast.ExprStmt).X).(*ast.CallExpr)
		if !ok {
			return // not a call statement
		}

		// Call to function or method?

		*ast.IncDecStmt, *ast.AssignStmt, *ast.GoStmt, *ast.DeferStmt,
		*ast.RangeStmt:
		// no chance

	case *ast.LabeledStmt:
		return check.isTerminating(s.Stmt, s.Label.Name)

	case *ast.ExprStmt:
		// calling the predeclared (possibly parenthesized) panic() function is terminating
		if call, ok := ast.Unparen(s.X).(*ast.CallExpr); ok && check.isPanic[call] {
			return true
		}

	case *ast.ReturnStmt:

		// case *Field:
		// case *InterfaceType:
		// case *FuncType:
		// case *MapType:
		// case *ChanType:

		// statements
		// case *EmptyStmt:
		// case *LabeledStmt:
		// case *BlockStmt:
		// case *ExprStmt:
		case *SendStmt:
			m = n.Chan
		// case *DeclStmt:
		case *AssignStmt:
			m = n.Lhs
		// case *BranchStmt:
		// case *CallStmt:
		// case *ReturnStmt:
		// case *IfStmt:
		// case *ForStmt:

				return
			}
			assert = n
			targets = append(targets, n.Type)
		case *ast.TypeSwitchStmt:
			// retrieve type assertion from type switch's 'assign' field
			switch t := n.Assign.(type) {
			case *ast.ExprStmt:
				assert = t.X.(*ast.TypeAssertExpr)
			case *ast.AssignStmt:
				assert = t.Rhs[0].(*ast.TypeAssertExpr)
			}
			// gather target types from case clauses
			for _, c := range n.Body.List {

		log.Fatalf("%s: internal error in findLabels: unexpected statement %T", d.pass.Fset.Position(x.Pos()), x)

	case *ast.AssignStmt,
		*ast.BadStmt,
		*ast.DeclStmt,
		*ast.DeferStmt,
		*ast.EmptyStmt,
		*ast.ExprStmt,
		*ast.GoStmt,
		*ast.IncDecStmt,
		*ast.ReturnStmt,
		*ast.SendStmt:
		// no statements inside

	case *ast.BlockStmt:
		for _, stmt := range x.List {
			d.findLabels(stmt)
		}

		if start == nil || end == nil {
			start = n
			end = n
		} else {
			end.then = n
			end = n
		}
	}
	for _, stmt := range body {
		switch stmt := stmt.(type) {
		case *ast.ExprStmt:
			if x, _ := stmt.X.(*ast.CallExpr); x != nil {
				funstr := exprToString(x.Fun)
				if funstr == "putattr" {
					form, _ := x.Args[3].(*ast.Ident)
					if form == nil {

// It also determines the possible types of its Stmt field.
type BlockKind uint8

const (
	KindInvalid BlockKind = iota // Stmt=nil

	KindUnreachable     // unreachable block after {Branch,Return}Stmt / no-return call ExprStmt
	KindBody            // function body BlockStmt
	KindForBody         // body of ForStmt
	KindForDone         // block after ForStmt
	KindForLoop         // head of ForStmt
	KindForPost         // post condition of ForStmt