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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This file sets up the universe scope and the unsafe package.
package types
import (
// The Universe scope contains all predeclared objects of Go.
// It is the outermost scope of any chain of nested scopes.
var Universe *Scope
// The Unsafe package is the package returned by an importer
// for the import path "unsafe".
var Unsafe *Package
var (
universeIota *Const
universeByte *Basic // uint8 alias, but has name "byte"
universeRune *Basic // int32 alias, but has name "rune"
universeAny *Named
universeError *Named
// Typ contains the predeclared *Basic types indexed by their
// corresponding BasicKind.
// The *Basic type for Typ[Byte] will have the name "uint8".
// Use Universe.Lookup("byte").Type() to obtain the specific
// alias basic type named "byte" (and analogous for "rune").
var Typ = []*Basic{
Invalid: {Invalid, 0, "invalid type", aType{}},
Bool: {Bool, IsBoolean, "bool", aType{}},
Int: {Int, IsInteger, "int", aType{}},
Int8: {Int8, IsInteger, "int8", aType{}},
Int16: {Int16, IsInteger, "int16", aType{}},
Int32: {Int32, IsInteger, "int32", aType{}},
Int64: {Int64, IsInteger, "int64", aType{}},
Uint: {Uint, IsInteger | IsUnsigned, "uint", aType{}},
Uint8: {Uint8, IsInteger | IsUnsigned, "uint8", aType{}},
Uint16: {Uint16, IsInteger | IsUnsigned, "uint16", aType{}},
Uint32: {Uint32, IsInteger | IsUnsigned, "uint32", aType{}},
Uint64: {Uint64, IsInteger | IsUnsigned, "uint64", aType{}},
Uintptr: {Uintptr, IsInteger | IsUnsigned, "uintptr", aType{}},
Float32: {Float32, IsFloat, "float32", aType{}},
Float64: {Float64, IsFloat, "float64", aType{}},
Complex64: {Complex64, IsComplex, "complex64", aType{}},
Complex128: {Complex128, IsComplex, "complex128", aType{}},
String: {String, IsString, "string", aType{}},
UnsafePointer: {UnsafePointer, 0, "Pointer", aType{}},
UntypedBool: {UntypedBool, IsBoolean | IsUntyped, "untyped bool", aType{}},
UntypedInt: {UntypedInt, IsInteger | IsUntyped, "untyped int", aType{}},
UntypedRune: {UntypedRune, IsInteger | IsUntyped, "untyped rune", aType{}},
UntypedFloat: {UntypedFloat, IsFloat | IsUntyped, "untyped float", aType{}},
UntypedComplex: {UntypedComplex, IsComplex | IsUntyped, "untyped complex", aType{}},
UntypedString: {UntypedString, IsString | IsUntyped, "untyped string", aType{}},
UntypedNil: {UntypedNil, IsUntyped, "untyped nil", aType{}},
var aliases = [...]*Basic{
{Byte, IsInteger | IsUnsigned, "byte", aType{}},
{Rune, IsInteger, "rune", aType{}},
func defPredeclaredTypes() {
for _, t := range Typ {
def(NewTypeName(token.NoPos, nil,, t))
for _, t := range aliases {
def(NewTypeName(token.NoPos, nil,, t))
// any
// (Predeclared and entered into universe scope so we do all the
// usual checks; but removed again from scope later since it's
// only visible as constraint in a type parameter list.)
typ := &Named{underlying: &emptyInterface}
def(NewTypeName(token.NoPos, nil, "any", typ))
// Error has a nil package in its qualified name since it is in no package
res := NewVar(token.NoPos, nil, "", Typ[String])
sig := &Signature{results: NewTuple(res)}
err := NewFunc(token.NoPos, nil, "Error", sig)
typ := &Named{underlying: NewInterfaceType([]*Func{err}, nil).Complete()}
sig.recv = NewVar(token.NoPos, nil, "", typ)
def(NewTypeName(token.NoPos, nil, "error", typ))
var predeclaredConsts = [...]struct {
name string
kind BasicKind
val constant.Value
{"true", UntypedBool, constant.MakeBool(true)},
{"false", UntypedBool, constant.MakeBool(false)},
{"iota", UntypedInt, constant.MakeInt64(0)},
func defPredeclaredConsts() {
for _, c := range predeclaredConsts {
def(NewConst(token.NoPos, nil,, Typ[c.kind], c.val))
func defPredeclaredNil() {
def(&Nil{object{name: "nil", typ: Typ[UntypedNil], color_: black}})
// A builtinId is the id of a builtin function.
type builtinId int
const (
// universe scope
_Append builtinId = iota
// package unsafe
// testing support
var predeclaredFuncs = [...]struct {
name string
nargs int
variadic bool
kind exprKind
_Append: {"append", 1, true, expression},
_Cap: {"cap", 1, false, expression},
_Close: {"close", 1, false, statement},
_Complex: {"complex", 2, false, expression},
_Copy: {"copy", 2, false, statement},
_Delete: {"delete", 2, false, statement},
_Imag: {"imag", 1, false, expression},
_Len: {"len", 1, false, expression},
_Make: {"make", 1, true, expression},
_New: {"new", 1, false, expression},
_Panic: {"panic", 1, false, statement},
_Print: {"print", 0, true, statement},
_Println: {"println", 0, true, statement},
_Real: {"real", 1, false, expression},
_Recover: {"recover", 0, false, statement},
_Alignof: {"Alignof", 1, false, expression},
_Offsetof: {"Offsetof", 1, false, expression},
_Sizeof: {"Sizeof", 1, false, expression},
_Assert: {"assert", 1, false, statement},
_Trace: {"trace", 0, true, statement},
func defPredeclaredFuncs() {
for i := range predeclaredFuncs {
id := builtinId(i)
if id == _Assert || id == _Trace {
continue // only define these in testing environment
// DefPredeclaredTestFuncs defines the assert and trace built-ins.
// These built-ins are intended for debugging and testing of this
// package only.
func DefPredeclaredTestFuncs() {
if Universe.Lookup("assert") != nil {
return // already defined
func defPredeclaredComparable() {
// The "comparable" interface can be imagined as defined like
// type comparable interface {
// == () untyped bool
// != () untyped bool
// }
// == and != cannot be user-declared but we can declare
// a magic method == and check for its presence when needed.
// Define interface { == () }. We don't care about the signature
// for == so leave it empty except for the receiver, which is
// set up later to match the usual interface method assumptions.
sig := new(Signature)
eql := NewFunc(token.NoPos, nil, "==", sig)
iface := NewInterfaceType([]*Func{eql}, nil).Complete()
// set up the defined type for the interface
obj := NewTypeName(token.NoPos, nil, "comparable", nil)
named := NewNamed(obj, iface, nil)
obj.color_ = black
sig.recv = NewVar(token.NoPos, nil, "", named) // complete == signature
func init() {
Universe = NewScope(nil, token.NoPos, token.NoPos, "universe")
Unsafe = NewPackage("unsafe", "unsafe")
Unsafe.complete = true
universeIota = Universe.Lookup("iota").(*Const)
universeByte = Universe.Lookup("byte").(*TypeName).typ.(*Basic)
universeRune = Universe.Lookup("rune").(*TypeName).typ.(*Basic)
universeAny = Universe.Lookup("any").(*TypeName).typ.(*Named)
universeError = Universe.Lookup("error").(*TypeName).typ.(*Named)
// "any" is only visible as constraint in a type parameter list
delete(Universe.elems, "any")
// Objects with names containing blanks are internal and not entered into
// a scope. Objects with exported names are inserted in the unsafe package
// scope; other objects are inserted in the universe scope.
func def(obj Object) {
assert(obj.color() == black)
name := obj.Name()
if strings.Contains(name, " ") {
return // nothing to do
// fix Obj link for named types
if typ := obj.Type().Named(); typ != nil {
typ.obj = obj.(*TypeName)
// exported identifiers go into package unsafe
scope := Universe
if obj.Exported() {
scope = Unsafe.scope
// set Pkg field
switch obj := obj.(type) {
case *TypeName:
obj.pkg = Unsafe
case *Builtin:
obj.pkg = Unsafe
if scope.Insert(obj) != nil {
panic("internal error: double declaration")