go type 源码
golang type 代码
文件路径：/src/go/types/type.go
// 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.
package types
// A Type represents a type of Go.
// All types implement the Type interface.
type Type interface {
// Underlying returns the underlying type of a type.
Underlying() Type
// String returns a string representation of a type.
String() string
}
// under returns the true expanded underlying type.
// If it doesn't exist, the result is Typ[Invalid].
// under must only be called when a type is known
// to be fully set up.
func under(t Type) Type {
if t, _ := t.(*Named); t != nil {
return t.under()
}
return t.Underlying()
}
// If t is not a type parameter, coreType returns the underlying type.
// If t is a type parameter, coreType returns the single underlying
// type of all types in its type set if it exists, or nil otherwise. If the
// type set contains only unrestricted and restricted channel types (with
// identical element types), the single underlying type is the restricted
// channel type if the restrictions are always the same, or nil otherwise.
func coreType(t Type) Type {
tpar, _ := t.(*TypeParam)
if tpar == nil {
return under(t)
}
var su Type
if tpar.underIs(func(u Type) bool {
if u == nil {
return false
}
if su != nil {
u = match(su, u)
if u == nil {
return false
}
}
// su == nil || match(su, u) != nil
su = u
return true
}) {
return su
}
return nil
}
// coreString is like coreType but also considers []byte
// and strings as identical. In this case, if successful and we saw
// a string, the result is of type (possibly untyped) string.
func coreString(t Type) Type {
tpar, _ := t.(*TypeParam)
if tpar == nil {
return under(t) // string or untyped string
}
var su Type
hasString := false
if tpar.underIs(func(u Type) bool {
if u == nil {
return false
}
if isString(u) {
u = NewSlice(universeByte)
hasString = true
}
if su != nil {
u = match(su, u)
if u == nil {
return false
}
}
// su == nil || match(su, u) != nil
su = u
return true
}) {
if hasString {
return Typ[String]
}
return su
}
return nil
}
// If x and y are identical, match returns x.
// If x and y are identical channels but for their direction
// and one of them is unrestricted, match returns the channel
// with the restricted direction.
// In all other cases, match returns nil.
func match(x, y Type) Type {
// Common case: we don't have channels.
if Identical(x, y) {
return x
}
// We may have channels that differ in direction only.
if x, _ := x.(*Chan); x != nil {
if y, _ := y.(*Chan); y != nil && Identical(x.elem, y.elem) {
// We have channels that differ in direction only.
// If there's an unrestricted channel, select the restricted one.
switch {
case x.dir == SendRecv:
return y
case y.dir == SendRecv:
return x
}
}
}
// types are different
return nil
}
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