golang interface 代码
文件路径：/src/cmd/compile/internal/types2/interface.go
/ Copyright 2021 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 types2
import "cmd/compile/internal/syntax"
/ ----------------------------------------------------------------------------
/ API
/ An Interface represents an interface type.
type Interface struct {
check *Checker / for error reporting; nil once type set is computed
methods []*Func / ordered list of explicitly declared methods
embeddeds []Type / ordered list of explicitly embedded elements
embedPos *[]syntax.Pos / positions of embedded elements; or nil (for error messages) - use pointer to save space
implicit bool / interface is wrapper for type set literal (non-interface T, ~T, or A|B)
complete bool / indicates that all fields (except for tset) are set up
tset *_TypeSet / type set described by this interface, computed lazily
}
/ typeSet returns the type set for interface t.
func (t *Interface) typeSet() *_TypeSet { return computeInterfaceTypeSet(t.check, nopos, t) }
/ emptyInterface represents the empty interface
var emptyInterface = Interface{complete: true, tset: &topTypeSet}
/ NewInterfaceType returns a new interface for the given methods and embedded types.
/ NewInterfaceType takes ownership of the provided methods and may modify their types
/ by setting missing receivers.
func NewInterfaceType(methods []*Func, embeddeds []Type) *Interface {
if len(methods) == 0 && len(embeddeds) == 0 {
return &emptyInterface
}
/ set method receivers if necessary
typ := (*Checker)(nil).newInterface()
for _, m := range methods {
if sig := m.typ.(*Signature); sig.recv == nil {
sig.recv = NewVar(m.pos, m.pkg, "", typ)
}
}
/ sort for API stability
sortMethods(methods)
typ.methods = methods
typ.embeddeds = embeddeds
typ.complete = true
return typ
}
/ check may be nil
func (check *Checker) newInterface() *Interface {
typ := &Interface{check: check}
if check != nil {
check.needsCleanup(typ)
}
return typ
}
/ MarkImplicit marks the interface t as implicit, meaning this interface
/ corresponds to a constraint literal such as ~T or A|B without explicit
/ interface embedding. MarkImplicit should be called before any concurrent use
/ of implicit interfaces.
func (t *Interface) MarkImplicit() {
t.implicit = true
}
/ NumExplicitMethods returns the number of explicitly declared methods of interface t.
func (t *Interface) NumExplicitMethods() int { return len(t.methods) }
/ ExplicitMethod returns the i'th explicitly declared method of interface t for 0 <= i < t.NumExplicitMethods().
/ The methods are ordered by their unique Id.
func (t *Interface) ExplicitMethod(i int) *Func { return t.methods[i] }
/ NumEmbeddeds returns the number of embedded types in interface t.
func (t *Interface) NumEmbeddeds() int { return len(t.embeddeds) }
/ EmbeddedType returns the i'th embedded type of interface t for 0 <= i < t.NumEmbeddeds().
func (t *Interface) EmbeddedType(i int) Type { return t.embeddeds[i] }
/ NumMethods returns the total number of methods of interface t.
func (t *Interface) NumMethods() int { return t.typeSet().NumMethods() }
/ Method returns the i'th method of interface t for 0 <= i < t.NumMethods().
/ The methods are ordered by their unique Id.
func (t *Interface) Method(i int) *Func { return t.typeSet().Method(i) }
/ Empty reports whether t is the empty interface.
func (t *Interface) Empty() bool { return t.typeSet().IsAll() }
/ IsComparable reports whether each type in interface t's type set is comparable.
func (t *Interface) IsComparable() bool { return t.typeSet().IsComparable(nil) }
/ IsMethodSet reports whether the interface t is fully described by its method set.
func (t *Interface) IsMethodSet() bool { return t.typeSet().IsMethodSet() }
/ IsImplicit reports whether the interface t is a wrapper for a type set literal.
func (t *Interface) IsImplicit() bool { return t.implicit }
func (t *Interface) Underlying() Type { return t }
func (t *Interface) String() string { return TypeString(t, nil) }
/ ----------------------------------------------------------------------------
/ Implementation
func (t *Interface) cleanup() {
t.check = nil
t.embedPos = nil
}
func (check *Checker) interfaceType(ityp *Interface, iface *syntax.InterfaceType, def *Named) {
addEmbedded := func(pos syntax.Pos, typ Type) {
ityp.embeddeds = append(ityp.embeddeds, typ)
if ityp.embedPos == nil {
ityp.embedPos = new([]syntax.Pos)
}
*ityp.embedPos = append(*ityp.embedPos, pos)
}
for _, f := range iface.MethodList {
if f.Name == nil {
addEmbedded(posFor(f.Type), parseUnion(check, f.Type))
continue
}
/ f.Name != nil
/ We have a method with name f.Name.
name := f.Name.Value
if name == "_" {
check.error(f.Name, "methods must have a unique non-blank name")
continue / ignore
}
typ := check.typ(f.Type)
sig, _ := typ.(*Signature)
if sig == nil {
if typ != Typ[Invalid] {
check.errorf(f.Type, invalidAST+"%s is not a method signature", typ)
}
continue / ignore
}
/ use named receiver type if available (for better error messages)
var recvTyp Type = ityp
if def != nil {
recvTyp = def
}
sig.recv = NewVar(f.Name.Pos(), check.pkg, "", recvTyp)
m := NewFunc(f.Name.Pos(), check.pkg, name, sig)
check.recordDef(f.Name, m)
ityp.methods = append(ityp.methods, m)
}
/ All methods and embedded elements for this interface are collected;
/ i.e., this interface may be used in a type set computation.
ityp.complete = true
if len(ityp.methods) == 0 && len(ityp.embeddeds) == 0 {
/ empty interface
ityp.tset = &topTypeSet
return
}
/ sort for API stability
/ (don't sort embeddeds: they must correspond to *embedPos entries)
sortMethods(ityp.methods)
/ Compute type set as soon as possible to report any errors.
/ Subsequent uses of type sets will use this computed type
/ set and won't need to pass in a *Checker.
check.later(func() {
computeInterfaceTypeSet(check, iface.Pos(), ityp)
}).describef(iface, "compute type set for %s", ityp)
}