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// 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 (
"bytes"
"cmd/compile/internal/syntax"
"fmt"
"sort"
)
// ----------------------------------------------------------------------------
// API
// A _TypeSet represents the type set of an interface.
type _TypeSet struct {
comparable bool // if set, the interface is or embeds comparable
// TODO(gri) consider using a set for the methods for faster lookup
methods []*Func // all methods of the interface; sorted by unique ID
terms termlist // type terms of the type set
}
// IsEmpty reports whether type set s is the empty set.
func (s *_TypeSet) IsEmpty() bool { return s.terms.isEmpty() }
// IsAll reports whether type set s is the set of all types (corresponding to the empty interface).
func (s *_TypeSet) IsAll() bool {
return !s.comparable && len(s.methods) == 0 && s.terms.isAll()
}
// IsConstraint reports whether type set s is not just a set of methods.
func (s *_TypeSet) IsConstraint() bool { return s.comparable || !s.terms.isAll() }
// IsComparable reports whether each type in the set is comparable.
func (s *_TypeSet) IsComparable() bool {
if s.terms.isAll() {
return s.comparable
}
return s.is(func(t *term) bool {
return Comparable(t.typ)
})
}
// TODO(gri) IsTypeSet is not a great name for this predicate. Find a better one.
// IsTypeSet reports whether the type set s is represented by a finite set of underlying types.
func (s *_TypeSet) IsTypeSet() bool {
return !s.comparable && len(s.methods) == 0
}
// NumMethods returns the number of methods available.
func (s *_TypeSet) NumMethods() int { return len(s.methods) }
// Method returns the i'th method of type set s for 0 <= i < s.NumMethods().
// The methods are ordered by their unique ID.
func (s *_TypeSet) Method(i int) *Func { return s.methods[i] }
// LookupMethod returns the index of and method with matching package and name, or (-1, nil).
func (s *_TypeSet) LookupMethod(pkg *Package, name string) (int, *Func) {
// TODO(gri) s.methods is sorted - consider binary search
return lookupMethod(s.methods, pkg, name)
}
func (s *_TypeSet) String() string {
switch {
case s.IsEmpty():
return "∅"
case s.IsAll():
return "𝓤"
}
hasMethods := len(s.methods) > 0
hasTerms := s.hasTerms()
var buf bytes.Buffer
buf.WriteByte('{')
if s.comparable {
buf.WriteString("comparable")
if hasMethods || hasTerms {
buf.WriteString("; ")
}
}
for i, m := range s.methods {
if i > 0 {
buf.WriteString("; ")
}
buf.WriteString(m.String())
}
if hasMethods && hasTerms {
buf.WriteString("; ")
}
if hasTerms {
buf.WriteString(s.terms.String())
}
buf.WriteString("}")
return buf.String()
}
// ----------------------------------------------------------------------------
// Implementation
func (s *_TypeSet) hasTerms() bool { return !s.terms.isAll() }
func (s *_TypeSet) structuralType() Type { return s.terms.structuralType() }
func (s *_TypeSet) includes(t Type) bool { return s.terms.includes(t) }
func (s1 *_TypeSet) subsetOf(s2 *_TypeSet) bool { return s1.terms.subsetOf(s2.terms) }
// TODO(gri) TypeSet.is and TypeSet.underIs should probably also go into termlist.go
var topTerm = term{false, theTop}
func (s *_TypeSet) is(f func(*term) bool) bool {
if len(s.terms) == 0 {
return false
}
for _, t := range s.terms {
// Terms represent the top term with a nil type.
// The rest of the type checker uses the top type
// instead. Convert.
// TODO(gri) investigate if we can do without this
if t.typ == nil {
t = &topTerm
}
if !f(t) {
return false
}
}
return true
}
func (s *_TypeSet) underIs(f func(Type) bool) bool {
if len(s.terms) == 0 {
return false
}
for _, t := range s.terms {
// see corresponding comment in TypeSet.is
u := t.typ
if u == nil {
u = theTop
}
// t == under(t) for ~t terms
if !t.tilde {
u = under(u)
}
if debug {
assert(Identical(u, under(u)))
}
if !f(u) {
return false
}
}
return true
}
// topTypeSet may be used as type set for the empty interface.
var topTypeSet = _TypeSet{terms: allTermlist}
// computeInterfaceTypeSet may be called with check == nil.
func computeInterfaceTypeSet(check *Checker, pos syntax.Pos, ityp *Interface) *_TypeSet {
if ityp.tset != nil {
return ityp.tset
}
// If the interface is not fully set up yet, the type set will
// not be complete, which may lead to errors when using the the
// type set (e.g. missing method). Don't compute a partial type
// set (and don't store it!), so that we still compute the full
// type set eventually. Instead, return the top type set and
// let any follow-on errors play out.
if !ityp.complete {
return &topTypeSet
}
if check != nil && check.conf.Trace {
// Types don't generally have position information.
// If we don't have a valid pos provided, try to use
// one close enough.
if !pos.IsKnown() && len(ityp.methods) > 0 {
pos = ityp.methods[0].pos
}
check.trace(pos, "type set for %s", ityp)
check.indent++
defer func() {
check.indent--
check.trace(pos, "=> %s ", ityp.typeSet())
}()
}
// An infinitely expanding interface (due to a cycle) is detected
// elsewhere (Checker.validType), so here we simply assume we only
// have valid interfaces. Mark the interface as complete to avoid
// infinite recursion if the validType check occurs later for some
// reason.
ityp.tset = &_TypeSet{terms: allTermlist} // TODO(gri) is this sufficient?
// Methods of embedded interfaces are collected unchanged; i.e., the identity
// of a method I.m's Func Object of an interface I is the same as that of
// the method m in an interface that embeds interface I. On the other hand,
// if a method is embedded via multiple overlapping embedded interfaces, we
// don't provide a guarantee which "original m" got chosen for the embedding
// interface. See also issue #34421.
//
// If we don't care to provide this identity guarantee anymore, instead of
// reusing the original method in embeddings, we can clone the method's Func
// Object and give it the position of a corresponding embedded interface. Then
// we can get rid of the mpos map below and simply use the cloned method's
// position.
var todo []*Func
var seen objset
var methods []*Func
mpos := make(map[*Func]syntax.Pos) // method specification or method embedding position, for good error messages
addMethod := func(pos syntax.Pos, m *Func, explicit bool) {
switch other := seen.insert(m); {
case other == nil:
methods = append(methods, m)
mpos[m] = pos
case explicit:
if check == nil {
panic(fmt.Sprintf("%s: duplicate method %s", m.pos, m.name))
}
// check != nil
var err error_
err.errorf(pos, "duplicate method %s", m.name)
err.errorf(mpos[other.(*Func)], "other declaration of %s", m.name)
check.report(&err)
default:
// We have a duplicate method name in an embedded (not explicitly declared) method.
// Check method signatures after all types are computed (issue #33656).
// If we're pre-go1.14 (overlapping embeddings are not permitted), report that
// error here as well (even though we could do it eagerly) because it's the same
// error message.
if check == nil {
// check method signatures after all locally embedded interfaces are computed
todo = append(todo, m, other.(*Func))
break
}
// check != nil
check.later(func() {
if !check.allowVersion(m.pkg, 1, 14) || !Identical(m.typ, other.Type()) {
var err error_
err.errorf(pos, "duplicate method %s", m.name)
err.errorf(mpos[other.(*Func)], "other declaration of %s", m.name)
check.report(&err)
}
})
}
}
for _, m := range ityp.methods {
addMethod(m.pos, m, true)
}
// collect embedded elements
var allTerms = allTermlist
for i, typ := range ityp.embeddeds {
// The embedding position is nil for imported interfaces
// and also for interface copies after substitution (but
// in that case we don't need to report errors again).
var pos syntax.Pos // embedding position
if ityp.embedPos != nil {
pos = (*ityp.embedPos)[i]
}
var terms termlist
switch u := under(typ).(type) {
case *Interface:
tset := computeInterfaceTypeSet(check, pos, u)
// If typ is local, an error was already reported where typ is specified/defined.
if check != nil && check.isImportedConstraint(typ) && !check.allowVersion(check.pkg, 1, 18) {
check.errorf(pos, "embedding constraint interface %s requires go1.18 or later", typ)
continue
}
if tset.comparable {
ityp.tset.comparable = true
}
for _, m := range tset.methods {
addMethod(pos, m, false) // use embedding position pos rather than m.pos
}
terms = tset.terms
case *Union:
if check != nil && !check.allowVersion(check.pkg, 1, 18) {
check.errorf(pos, "embedding interface element %s requires go1.18 or later", u)
continue
}
tset := computeUnionTypeSet(check, pos, u)
if tset == &invalidTypeSet {
continue // ignore invalid unions
}
terms = tset.terms
case *TypeParam:
// Embedding stand-alone type parameters is not permitted.
// This case is handled during union parsing.
unreachable()
default:
if typ == Typ[Invalid] {
continue
}
if check != nil && !check.allowVersion(check.pkg, 1, 18) {
check.errorf(pos, "embedding non-interface type %s requires go1.18 or later", typ)
continue
}
terms = termlist{{false, typ}}
}
// The type set of an interface is the intersection
// of the type sets of all its elements.
// Intersection cannot produce longer termlists and
// thus cannot overflow.
allTerms = allTerms.intersect(terms)
}
ityp.embedPos = nil // not needed anymore (errors have been reported)
// process todo's (this only happens if check == nil)
for i := 0; i < len(todo); i += 2 {
m := todo[i]
other := todo[i+1]
if !Identical(m.typ, other.typ) {
panic(fmt.Sprintf("%s: duplicate method %s", m.pos, m.name))
}
}
if methods != nil {
sortMethods(methods)
ityp.tset.methods = methods
}
ityp.tset.terms = allTerms
return ityp.tset
}
func sortMethods(list []*Func) {
sort.Sort(byUniqueMethodName(list))
}
func assertSortedMethods(list []*Func) {
if !debug {
panic("assertSortedMethods called outside debug mode")
}
if !sort.IsSorted(byUniqueMethodName(list)) {
panic("methods not sorted")
}
}
// byUniqueMethodName method lists can be sorted by their unique method names.
type byUniqueMethodName []*Func
func (a byUniqueMethodName) Len() int { return len(a) }
func (a byUniqueMethodName) Less(i, j int) bool { return a[i].less(&a[j].object) }
func (a byUniqueMethodName) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
// invalidTypeSet is a singleton type set to signal an invalid type set
// due to an error. It's also a valid empty type set, so consumers of
// type sets may choose to ignore it.
var invalidTypeSet _TypeSet
// computeUnionTypeSet may be called with check == nil.
// The result is &invalidTypeSet if the union overflows.
func computeUnionTypeSet(check *Checker, pos syntax.Pos, utyp *Union) *_TypeSet {
if utyp.tset != nil {
return utyp.tset
}
// avoid infinite recursion (see also computeInterfaceTypeSet)
utyp.tset = new(_TypeSet)
var allTerms termlist
for _, t := range utyp.terms {
var terms termlist
switch u := under(t.typ).(type) {
case *Interface:
terms = computeInterfaceTypeSet(check, pos, u).terms
case *TypeParam:
// A stand-alone type parameters is not permitted as union term.
// This case is handled during union parsing.
unreachable()
default:
if t.typ == Typ[Invalid] {
continue
}
terms = termlist{(*term)(t)}
}
// The type set of a union expression is the union
// of the type sets of each term.
allTerms = allTerms.union(terms)
if len(allTerms) > maxTermCount {
if check != nil {
check.errorf(pos, "cannot handle more than %d union terms (implementation limitation)", maxTermCount)
}
utyp.tset = &invalidTypeSet
return utyp.tset
}
}
utyp.tset.terms = allTerms
return utyp.tset
}