testPos(t, types, "package p; func f(", ")",
		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Type.ParamList[0].Type },
	)

	testPos(t, fields, "package p; func f(", ")",
		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Type.ParamList[0] },
	)

	testPos(t, stmts, "package p; func _() { ", "; }",
		func(f *File) Node { return f.DeclList[0].(*FuncDecl).Body.List[0] },
	)

				m = l
				continue
			}
			return n.Pos()
		case *FuncType:
			if l := lastField(n.ResultList); l != nil {
				m = l
				continue
			}
			if l := lastField(n.ParamList); l != nil {
				m = l
				continue
			}
			return n.Pos()
		case *MapType:
			m = n.Value
		case *ChanType:
			m = n.Elem

		// statements
		case *EmptyStmt:
			return n.Pos()

			}
		}

	case *Field:
		if n.Name != nil {
			w.node(n.Name)
		}
		w.node(n.Type)

	case *InterfaceType:
		w.fieldList(n.MethodList)

	case *FuncType:
		w.fieldList(n.ParamList)
		w.fieldList(n.ResultList)

	case *MapType:
		w.node(n.Key)
		w.node(n.Value)

	case *ChanType:
		w.node(n.Elem)

	// statements
	case *EmptyStmt: // nothing to do

		node
	}

	// interface { MethodList[0]; MethodList[1]; ... }
	InterfaceType struct {
		MethodList []*Field
		expr
	}

	FuncType struct {
		ParamList  []*Field
		ResultList []*Field
		expr
	}

	// map[Key]Value
	MapType struct {
		Key, Value Expr
		expr
	}

	//   chan Elem
	// <-chan Elem
	// chan<- Elem
	ChanType struct {