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go/types: implement type sets with term lists

Browse Source 
This is a port of CL 338310 to go/types. It is superficially adjusted
for different error reporting and AST APIs. It also fixes a bug in CL
338310 that only manifests in go/types (TestFixedbugs/issue39755.go2)
due to go/types preserving untyped nil. In that CL, operand.go is
checking if optype is a TypeParam, which can never be the case. A fix
for types2 will be mailed in a separate CL.

Change-Id: Icf3394e74baec536842267d99f7511d25ab32a8a
Reviewed-on: https://go-review.googlesource.com/c/go/+/342331
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Robert Findley 2021-08-15 15:28:22 -04:00
parent 94002f6fca
commit d043c8ea89
23 changed files with 334 additions and 419 deletions
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16
src/go/types/builtins.go
View File

@ -145,7 +145,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
mode := invalid
var typ Type
var val constant.Value
switch typ = implicitArrayDeref(optype(x.typ)); t := typ.(type) {
switch typ = implicitArrayDeref(under(x.typ)); t := typ.(type) {
case *Basic:
if isString(t) && id == _Len {
if x.mode == constant_ {
@ -179,9 +179,9 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
mode = value
}
case *Union:
case *TypeParam:
if t.underIs(func(t Type) bool {
switch t := t.(type) {
switch t := implicitArrayDeref(t).(type) {
case *Basic:
if isString(t) && id == _Len {
return true
@ -826,10 +826,10 @@ func (check *Checker) applyTypeFunc(f func(Type) Type, x Type) Type {
// type and collect possible result types at the same time.
var rtypes []Type
var tildes []bool
if !tp.iface().is(func(typ Type, tilde bool) bool {
if r := f(typ); r != nil {
if !tp.iface().typeSet().is(func(t *term) bool {
if r := f(t.typ); r != nil {
rtypes = append(rtypes, r)
tildes = append(tildes, tilde)
tildes = append(tildes, t.tilde)
return true
}
return false
@ -841,10 +841,8 @@ func (check *Checker) applyTypeFunc(f func(Type) Type, x Type) Type {
// type param is placed in the current package so export/import
// works as expected.
tpar := NewTypeName(token.NoPos, check.pkg, "<type parameter>", nil)
ptyp := check.NewTypeParam(tpar, &emptyInterface) // assigns type to tpar as a side-effect
ptyp := check.NewTypeParam(tpar, NewInterfaceType(nil, []Type{newUnion(rtypes, tildes)})) // assigns type to tpar as a side-effect
ptyp.index = tp.index
tsum := newUnion(rtypes, tildes)
ptyp.bound = &Interface{complete: true, tset: &_TypeSet{types: tsum}}
return ptyp
}

37
src/go/types/infer.go
View File

@ -275,7 +275,7 @@ func (w *tpWalker) isParameterized(typ Type) (res bool) {
}()
switch t := typ.(type) {
case nil, *Basic: // TODO(gri) should nil be handled here?
case nil, *top, *Basic: // TODO(gri) should nil be handled here?
break
case *Array:
@ -302,9 +302,6 @@ func (w *tpWalker) isParameterized(typ Type) (res bool) {
}
}
case *Union:
return w.isParameterizedTermList(t.terms)
case *Signature:
// t.tparams may not be nil if we are looking at a signature
// of a generic function type (or an interface method) that is
@ -322,7 +319,9 @@ func (w *tpWalker) isParameterized(typ Type) (res bool) {
return true
}
}
return w.isParameterized(tset.types)
return tset.is(func(t *term) bool {
return w.isParameterized(t.typ)
})
case *Map:
return w.isParameterized(t.key) || w.isParameterized(t.elem)
@ -353,15 +352,6 @@ func (w *tpWalker) isParameterizedTypeList(list []Type) bool {
return false
}
func (w *tpWalker) isParameterizedTermList(list []*term) bool {
for _, t := range list {
if w.isParameterized(t.typ) {
return true
}
}
return false
}
// inferB returns the list of actual type arguments inferred from the type parameters'
// bounds and an initial set of type arguments. If type inference is impossible because
// unification fails, an error is reported if report is set to true, the resulting types
@ -389,7 +379,7 @@ func (check *Checker) inferB(tparams []*TypeName, targs []Type, report bool) (ty
// Unify type parameters with their structural constraints, if any.
for _, tpar := range tparams {
typ := tpar.typ.(*TypeParam)
sbound := check.structuralType(typ.bound)
sbound := typ.structuralType()
if sbound != nil {
if !u.unify(typ, sbound) {
if report {
@ -462,20 +452,3 @@ func (check *Checker) inferB(tparams []*TypeName, targs []Type, report bool) (ty
return
}
// structuralType returns the structural type of a constraint, if any.
func (check *Checker) structuralType(constraint Type) Type {
if iface, _ := under(constraint).(*Interface); iface != nil {
types := iface.typeSet().types
if u, _ := types.(*Union); u != nil {
if u.NumTerms() == 1 {
// TODO(gri) do we need to respect tilde?
t, _ := u.Term(0)
return t
}
return nil
}
return types
}
return nil
}

18
src/go/types/instantiate.go
View File

@ -215,7 +215,7 @@ func (check *Checker) satisfies(pos token.Pos, targ Type, tpar *TypeParam, smap
}
// targ's underlying type must also be one of the interface types listed, if any
if iface.typeSet().types == nil {
if !iface.typeSet().hasTerms() {
return true // nothing to do
}
@ -223,24 +223,22 @@ func (check *Checker) satisfies(pos token.Pos, targ Type, tpar *TypeParam, smap
// list of iface types (i.e., the targ type list must be a non-empty subset of the iface types).
if targ := asTypeParam(targ); targ != nil {
targBound := targ.iface()
if targBound.typeSet().types == nil {
if !targBound.typeSet().hasTerms() {
check.softErrorf(atPos(pos), _Todo, "%s does not satisfy %s (%s has no type constraints)", targ, tpar.bound, targ)
return false
}
return iface.is(func(typ Type, tilde bool) bool {
// TODO(gri) incorporate tilde information!
if !iface.isSatisfiedBy(typ) {
// TODO(gri) match this error message with the one below (or vice versa)
check.softErrorf(atPos(pos), 0, "%s does not satisfy %s (%s type constraint %s not found in %s)", targ, tpar.bound, targ, typ, iface.typeSet().types)
if !targBound.typeSet().subsetOf(iface.typeSet()) {
// TODO(gri) need better error message
check.softErrorf(atPos(pos), _Todo, "%s does not satisfy %s", targ, tpar.bound)
return false
}
return true
})
}
// Otherwise, targ's type or underlying type must also be one of the interface types listed, if any.
if !iface.isSatisfiedBy(targ) {
check.softErrorf(atPos(pos), _Todo, "%s does not satisfy %s (%s not found in %s)", targ, tpar.bound, targ, iface.typeSet().types)
if !iface.typeSet().includes(targ) {
// TODO(gri) better error message
check.softErrorf(atPos(pos), _Todo, "%s does not satisfy %s", targ, tpar.bound)
return false
}

34
src/go/types/interface.go
View File

@ -25,20 +25,7 @@ type Interface struct {
}
// typeSet returns the type set for interface t.
func (t *Interface) typeSet() *_TypeSet { return computeTypeSet(nil, token.NoPos, t) }
// is reports whether interface t represents types that all satisfy f.
func (t *Interface) is(f func(Type, bool) bool) bool {
switch t := t.typeSet().types.(type) {
case nil, *top:
// TODO(gri) should settle on top or nil to represent this case
return false // we must have at least one type! (was bug)
case *Union:
return t.is(func(t *term) bool { return f(t.typ, t.tilde) })
default:
return f(t, false)
}
}
func (t *Interface) typeSet() *_TypeSet { return computeInterfaceTypeSet(nil, token.NoPos, t) }
// emptyInterface represents the empty (completed) interface
var emptyInterface = Interface{complete: true, tset: &topTypeSet}
@ -117,23 +104,6 @@ func (t *Interface) IsComparable() bool { return t.typeSet().IsComparable() }
// IsConstraint reports whether interface t is not just a method set.
func (t *Interface) IsConstraint() bool { return !t.typeSet().IsMethodSet() }
// isSatisfiedBy reports whether interface t's type list is satisfied by the type typ.
// If the type list is empty (absent), typ trivially satisfies the interface.
// TODO(gri) This is not a great name. Eventually, we should have a more comprehensive
// "implements" predicate.
func (t *Interface) isSatisfiedBy(typ Type) bool {
t.Complete()
switch t := t.typeSet().types.(type) {
case nil:
return true // no type restrictions
case *Union:
r, _ := t.intersect(typ, false)
return r != nil
default:
return Identical(t, typ)
}
}
// Complete computes the interface's type set. It must be called by users of
// NewInterfaceType and NewInterface after the interface's embedded types are
// fully defined and before using the interface type in any way other than to
@ -268,7 +238,7 @@ func (check *Checker) interfaceType(ityp *Interface, iface *ast.InterfaceType, d
// Compute type set with a non-nil *Checker 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() { computeTypeSet(check, iface.Pos(), ityp) })
check.later(func() { computeInterfaceTypeSet(check, iface.Pos(), ityp) })
}
func flattenUnion(list []ast.Expr, x ast.Expr) []ast.Expr {

2
src/go/types/operand.go
View File

@ -258,7 +258,7 @@ func (x *operand) assignableTo(check *Checker, T Type, reason *string) (bool, er
// x is an untyped value representable by a value of type T.
if isUntyped(Vu) {
if t, ok := Tu.(*Union); ok {
if t, _ := under(T).(*TypeParam); t != nil {
return t.is(func(t *term) bool {
// TODO(gri) this could probably be more efficient
if t.tilde {

12
src/go/types/predicates.go
View File

@ -229,16 +229,6 @@ func identical(x, y Type, cmpTags bool, p *ifacePair) bool {
identical(x.results, y.results, cmpTags, p)
}
case *Union:
// Two union types are identical if they contain the same terms.
// The set (list) of types in a union type consists of unique
// types - each type appears exactly once. Thus, two union types
// must contain the same number of types to have chance of
// being equal.
if y, ok := y.(*Union); ok {
return identicalTerms(x.terms, y.terms)
}
case *Interface:
// Two interface types are identical if they describe the same type sets.
// With the existing implementation restriction, this simplifies to:
@ -250,7 +240,7 @@ func identical(x, y Type, cmpTags bool, p *ifacePair) bool {
if y, ok := y.(*Interface); ok {
xset := x.typeSet()
yset := y.typeSet()
if !Identical(xset.types, yset.types) {
if !xset.terms.equal(yset.terms) {
return false
}
a := xset.methods

4
src/go/types/sizeof_test.go
View File

@ -26,7 +26,7 @@ func TestSizeof(t *testing.T) {
{Pointer{}, 8, 16},
{Tuple{}, 12, 24},
{Signature{}, 28, 56},
{Union{}, 12, 24},
{Union{}, 16, 32},
{Interface{}, 40, 80},
{Map{}, 16, 32},
{Chan{}, 12, 24},
@ -48,7 +48,7 @@ func TestSizeof(t *testing.T) {
// Misc
{Scope{}, 44, 88},
{Package{}, 40, 80},
{_TypeSet{}, 24, 48},
{_TypeSet{}, 28, 56},
}
for _, test := range tests {
got := reflect.TypeOf(test.val).Size()

3
src/go/types/stmt.go
View File

@ -917,10 +917,11 @@ func rangeKeyVal(typ Type, wantKey, wantVal bool) (Type, Type, string) {
case *Chan:
var msg string
if typ.dir == SendOnly {
// TODO(rfindley): this error message differs from types2. Reconcile this.
msg = "send-only channel"
}
return typ.elem, Typ[Invalid], msg
case *Union:
case *TypeParam:
first := true
var key, val Type
var msg string

12
src/go/types/subst.go
View File

@ -148,12 +148,12 @@ func (subst *subster) typ(typ Type) Type {
}
case *Union:
terms, copied := subst.termList(t.terms)
terms, copied := subst.termlist(t.terms)
if copied {
// TODO(gri) Remove duplicates that may have crept in after substitution
// (unlikely but possible). This matters for the Identical
// predicate on unions.
return &Union{terms}
// term list substitution may introduce duplicate terms (unlikely but possible).
// This is ok; lazy type set computation will determine the actual type set
// in normal form.
return &Union{terms, nil}
}
case *Interface:
@ -394,7 +394,7 @@ func (subst *subster) typeList(in []Type) (out []Type, copied bool) {
return
}
func (subst *subster) termList(in []*term) (out []*term, copied bool) {
func (subst *subster) termlist(in []*term) (out []*term, copied bool) {
out = in
for i, t := range in {
if u := subst.typ(t.typ); u != t.typ {

2
src/go/types/termlist.go
View File

@ -13,7 +13,7 @@ import "bytes"
// normal form.
type termlist []*term
// topTermList represents the set of all types.
// topTermlist represents the set of all types.
// It is in normal form.
var topTermlist = termlist{new(term)}

2
src/go/types/testdata/check/tinference.go2 vendored
View File

@ -92,7 +92,7 @@ func FromStrings[T interface{}, PT Setter[T]](s []string) []T {
result := make([]T, len(s))
for i, v := range s {
// The type of &result[i] is *T which is in the type list
// of Setter2, so we can convert it to PT.
// of Setter, so we can convert it to PT.
p := PT(&result[i])
// PT has a Set method.
p.Set(v)

8
src/go/types/testdata/check/typeinst2.go2 vendored
View File

@ -164,13 +164,13 @@ type _ interface {
// for them to be all in a single list, and we report the error
// as well.)
type _ interface {
~int|~ /* ERROR duplicate term int */ int
~int|int /* ERROR duplicate term int */
int|int /* ERROR duplicate term int */
~int|~ /* ERROR overlapping terms ~int */ int
~int|int /* ERROR overlapping terms int */
int|int /* ERROR overlapping terms int */
}
type _ interface {
~struct{f int} | ~struct{g int} | ~ /* ERROR duplicate term */ struct{f int}
~struct{f int} | ~struct{g int} | ~ /* ERROR overlapping terms */ struct {f int}
}
// Interface type lists can contain any type, incl. *Named types.

65
src/go/types/testdata/check/typeparams.go2 vendored
View File

@ -149,37 +149,40 @@ func _[T interface{}](x T) {
for range x /* ERROR cannot range */ {}
}
func _[T interface{ ~string | ~[]string }](x T) {
for range x {}
for i := range x { _ = i }
for i, _ := range x { _ = i }
for i, e := range x /* ERROR must have the same element type */ { _ = i }
for _, e := range x /* ERROR must have the same element type */ {}
var e rune
_ = e
for _, (e) = range x /* ERROR must have the same element type */ {}
}
func _[T interface{ ~string | ~[]rune | ~map[int]rune }](x T) {
for _, e := range x { _ = e }
for i, e := range x { _ = i; _ = e }
}
func _[T interface{ ~string | ~[]rune | ~map[string]rune }](x T) {
for _, e := range x { _ = e }
for i, e := range x /* ERROR must have the same key type */ { _ = e }
}
func _[T interface{ ~string | ~chan int }](x T) {
for range x {}
for i := range x { _ = i }
for i, _ := range x { _ = i } // TODO(gri) should get an error here: channels only return one value
}
func _[T interface{ ~string | ~chan<-int }](x T) {
for i := range x /* ERROR send-only channel */ { _ = i }
}
// Disabled for now until we have clarified semantics of range.
// TODO(gri) fix this
//
// func _[T interface{ ~string | ~[]string }](x T) {
// for range x {}
// for i := range x { _ = i }
// for i, _ := range x { _ = i }
// for i, e := range x /* ERROR must have the same element type */ { _ = i }
// for _, e := range x /* ERROR must have the same element type */ {}
// var e rune
// _ = e
// for _, (e) = range x /* ERROR must have the same element type */ {}
// }
//
//
// func _[T interface{ ~string | ~[]rune | ~map[int]rune }](x T) {
// for _, e := range x { _ = e }
// for i, e := range x { _ = i; _ = e }
// }
//
// func _[T interface{ ~string | ~[]rune | ~map[string]rune }](x T) {
// for _, e := range x { _ = e }
// for i, e := range x /* ERROR must have the same key type */ { _ = e }
// }
//
// func _[T interface{ ~string | ~chan int }](x T) {
// for range x {}
// for i := range x { _ = i }
// for i, _ := range x { _ = i } // TODO(gri) should get an error here: channels only return one value
// }
//
// func _[T interface{ ~string | ~chan<-int }](x T) {
// for i := range x /* ERROR send-only channel */ { _ = i }
// }
// type inference checks

41
src/go/types/testdata/examples/constraints.go2 vendored
View File

@ -18,18 +18,25 @@ type (
}
)
type MyInt int
type (
// Arbitrary types may be embedded like interfaces.
_ interface{int}
_ interface{~int}
// Types may be combined into a union.
_ interface{int|~string}
union interface{int|~string}
// Union terms must be unique independent of whether they are ~ or not.
_ interface{int|int /* ERROR duplicate term int */ }
_ interface{int|~ /* ERROR duplicate term int */ int }
_ interface{~int|~ /* ERROR duplicate term int */ int }
// Union terms must describe disjoint (non-overlapping) type sets.
_ interface{int|int /* ERROR overlapping terms int */ }
_ interface{int|~ /* ERROR overlapping terms ~int */ int }
_ interface{~int|~ /* ERROR overlapping terms ~int */ int }
_ interface{~int|MyInt /* ERROR overlapping terms p.MyInt and ~int */ }
_ interface{int|interface{}}
_ interface{int|~string|union}
_ interface{int|~string|interface{int}}
_ interface{union|union /* ERROR overlapping terms p.union and p.union */ }
// For now we do not permit interfaces with methods in unions.
_ interface{~ /* ERROR invalid use of ~ */ interface{}}
@ -45,6 +52,15 @@ type (
_ interface{~ /* ERROR invalid use of ~ */ bar }
)
// Stand-alone type parameters are not permitted as elements or terms in unions.
type (
_[T interface{ *T } ] struct{} // ok
_[T interface{ int | *T } ] struct{} // ok
_[T interface{ T /* ERROR cannot embed a type parameter */ } ] struct{}
_[T interface{ ~T /* ERROR cannot embed a type parameter */ } ] struct{}
_[T interface{ int|T /* ERROR cannot embed a type parameter */ }] struct{}
)
// Multiple embedded union elements are intersected. The order in which they
// appear in the interface doesn't matter since intersection is a symmetric
// operation.
@ -58,3 +74,18 @@ func _[T interface{ ~int; myInt1|myInt2 }]() T { return T(0) }
// Here the intersections are empty - there's no type that's in the type set of T.
func _[T interface{ myInt1|myInt2; int }]() T { return T(0 /* ERROR cannot convert */ ) }
func _[T interface{ int; myInt1|myInt2 }]() T { return T(0 /* ERROR cannot convert */ ) }
// Union elements may be interfaces as long as they don't define
// any methods or embed comparable.
type (
Integer interface{ ~int|~int8|~int16|~int32|~int64 }
Unsigned interface{ ~uint|~uint8|~uint16|~uint32|~uint64 }
Floats interface{ ~float32|~float64 }
Complex interface{ ~complex64|~complex128 }
Number interface{ Integer|Unsigned|Floats|Complex }
Ordered interface{ Integer|Unsigned|Floats|~string }
_ interface{ Number | error /* ERROR cannot use error in union */ }
_ interface{ Ordered | comparable /* ERROR cannot use comparable in union */ }
)

10
src/go/types/testdata/fixedbugs/issue41124.go2 vendored
View File

@ -47,7 +47,7 @@ type _ struct{
}
type _ struct{
I3 // ERROR interface contains type constraints
I3 // ERROR interface is .* comparable
}
// General composite types.
@ -59,19 +59,19 @@ type (
_ []I1 // ERROR interface is .* comparable
_ []I2 // ERROR interface contains type constraints
_ *I3 // ERROR interface contains type constraints
_ *I3 // ERROR interface is .* comparable
_ map[I1 /* ERROR interface is .* comparable */ ]I2 // ERROR interface contains type constraints
_ chan I3 // ERROR interface contains type constraints
_ chan I3 // ERROR interface is .* comparable
_ func(I1 /* ERROR interface is .* comparable */ )
_ func() I2 // ERROR interface contains type constraints
)
// Other cases.
var _ = [...]I3 /* ERROR interface contains type constraints */ {}
var _ = [...]I3 /* ERROR interface is .* comparable */ {}
func _(x interface{}) {
_ = x.(I3 /* ERROR interface contains type constraints */ )
_ = x.(I3 /* ERROR interface is .* comparable */ )
}
type T1[_ any] struct{}

21
src/go/types/type.go
View File

@ -44,28 +44,21 @@ func under(t Type) Type {
// optype returns a type's operational type. Except for
// type parameters, the operational type is the same
// as the underlying type (as returned by under). For
// Type parameters, the operational type is determined
// by the corresponding type bound's type list. The
// result may be the bottom or top type, but it is never
// the incoming type parameter.
// Type parameters, the operational type is the structural
// type, if any; otherwise it's the top type.
// The result is never the incoming type parameter.
func optype(typ Type) Type {
if t := asTypeParam(typ); t != nil {
// TODO(gri) review accuracy of this comment
// If the optype is typ, return the top type as we have
// no information. It also prevents infinite recursion
// via the asTypeParam converter function. This can happen
// for a type parameter list of the form:
// (type T interface { type T }).
// See also issue #39680.
if a := t.iface().typeSet().types; a != nil && a != typ {
// If we have a union with a single entry, ignore
// any tilde because under(~t) == under(t).
if u, _ := a.(*Union); u != nil && u.NumTerms() == 1 {
a, _ = u.Term(0)
}
if a != typ {
// a != typ and a is a type parameter => under(a) != typ, so this is ok
return under(a)
}
if u := t.structuralType(); u != nil {
assert(u != typ) // "naked" type parameters cannot be embedded
return u
}
return theTop
}

27
src/go/types/typeparam.go
View File

@ -69,7 +69,7 @@ func (t *TypeParam) Constraint() Type {
if n, _ := t.bound.(*Named); n != nil {
pos = n.obj.pos
}
computeTypeSet(t.check, pos, iface)
computeInterfaceTypeSet(t.check, pos, iface)
}
return t.bound
}
@ -82,14 +82,6 @@ func (t *TypeParam) SetConstraint(bound Type) {
t.bound = bound
}
// iface returns the constraint interface of t.
func (t *TypeParam) iface() *Interface {
if iface, _ := under(t.Constraint()).(*Interface); iface != nil {
return iface
}
return &emptyInterface
}
func (t *TypeParam) Underlying() Type { return t }
func (t *TypeParam) String() string { return TypeString(t, nil) }
@ -131,6 +123,23 @@ func bindTParams(list []*TypeName) *TypeParams {
// ----------------------------------------------------------------------------
// Implementation
// iface returns the constraint interface of t.
func (t *TypeParam) iface() *Interface {
if iface, _ := under(t.Constraint()).(*Interface); iface != nil {
return iface
}
return &emptyInterface
}
// structuralType returns the structural type of the type parameter's constraint; or nil.
func (t *TypeParam) structuralType() Type {
return t.iface().typeSet().structuralType()
}
func (t *TypeParam) is(f func(*term) bool) bool {
return t.iface().typeSet().is(f)
}
func (t *TypeParam) underIs(f func(Type) bool) bool {
return t.iface().typeSet().underIs(f)
}

171
src/go/types/typeset.go
View File

@ -19,31 +19,31 @@ 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
types Type // typically a *Union; nil means no type restrictions
terms termlist // type terms of the type set
}
// IsTop reports whether type set s is the top type set (corresponding to the empty interface).
func (s *_TypeSet) IsTop() bool { return !s.comparable && len(s.methods) == 0 && s.types == nil }
// IsEmpty reports whether type set s is the empty set.
func (s *_TypeSet) IsEmpty() bool { return s.terms.isEmpty() }
// IsTop reports whether type set s is the set of all types (corresponding to the empty interface).
func (s *_TypeSet) IsTop() bool { return !s.comparable && len(s.methods) == 0 && s.terms.isTop() }
// TODO(gri) IsMethodSet is not a great name for this predicate. Find a better one.
// IsMethodSet reports whether the type set s is described by a single set of methods.
func (s *_TypeSet) IsMethodSet() bool { return !s.comparable && s.types == nil }
func (s *_TypeSet) IsMethodSet() bool { return !s.comparable && s.terms.isTop() }
// IsComparable reports whether each type in the set is comparable.
// TODO(gri) this is not correct - there may be s.types values containing non-comparable types
func (s *_TypeSet) IsComparable() bool {
if s.types == nil {
if s.terms.isTop() {
return s.comparable
}
tcomparable := s.underIs(func(u Type) bool {
return Comparable(u)
return s.is(func(t *term) bool {
return Comparable(t.typ)
})
if !s.comparable {
return tcomparable
}
return s.comparable && tcomparable
}
// TODO(gri) IsTypeSet is not a great name. Find a better one.
// 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 {
@ -64,15 +64,21 @@ func (s *_TypeSet) LookupMethod(pkg *Package, name string) (int, *Func) {
}
func (s *_TypeSet) String() string {
if s.IsTop() {
switch {
case s.IsEmpty():
return "∅"
case s.IsTop():
return "⊤"
}
hasMethods := len(s.methods) > 0
hasTerms := s.hasTerms()
var buf bytes.Buffer
buf.WriteByte('{')
if s.comparable {
buf.WriteString(" comparable")
if len(s.methods) > 0 || s.types != nil {
if hasMethods || hasTerms {
buf.WriteByte(';')
}
}
@ -83,41 +89,77 @@ func (s *_TypeSet) String() string {
buf.WriteByte(' ')
buf.WriteString(m.String())
}
if len(s.methods) > 0 && s.types != nil {
if hasMethods && hasTerms {
buf.WriteByte(';')
}
if s.types != nil {
buf.WriteByte(' ')
writeType(&buf, s.types, nil, nil)
if hasTerms {
buf.WriteString(s.terms.String())
}
buf.WriteString(" }") // there was at least one method or term
buf.WriteString(" }") // there was a least one method or type
return buf.String()
}
// ----------------------------------------------------------------------------
// Implementation
// underIs reports whether f returned true for the underlying types of the
// enumerable types in the type set s. If the type set comprises all types
// f is called once with the top type; if the type set is empty, the result
// is false.
func (s *_TypeSet) underIs(f func(Type) bool) bool {
switch t := s.types.(type) {
case nil:
return f(theTop)
default:
return f(t)
case *Union:
return t.underIs(f)
func (s *_TypeSet) hasTerms() bool { return !s.terms.isTop() }
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
var topTypeSet = _TypeSet{terms: topTermlist}
// computeTypeSet may be called with check == nil.
func computeTypeSet(check *Checker, pos token.Pos, ityp *Interface) *_TypeSet {
// computeInterfaceTypeSet may be called with check == nil.
func computeInterfaceTypeSet(check *Checker, pos token.Pos, ityp *Interface) *_TypeSet {
if ityp.tset != nil {
return ityp.tset
}
@ -157,7 +199,7 @@ func computeTypeSet(check *Checker, pos token.Pos, ityp *Interface) *_TypeSet {
// have valid interfaces. Mark the interface as complete to avoid
// infinite recursion if the validType check occurs later for some
// reason.
ityp.tset = new(_TypeSet) // TODO(gri) is this sufficient?
ityp.tset = &_TypeSet{terms: topTermlist} // 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
@ -214,7 +256,7 @@ func computeTypeSet(check *Checker, pos token.Pos, ityp *Interface) *_TypeSet {
}
// collect embedded elements
var allTypes Type
var allTerms = topTermlist
for i, typ := range ityp.embeddeds {
// The embedding position is nil for imported interfaces
// and also for interface copies after substitution (but
@ -223,26 +265,22 @@ func computeTypeSet(check *Checker, pos token.Pos, ityp *Interface) *_TypeSet {
if ityp.embedPos != nil {
pos = (*ityp.embedPos)[i]
}
var types Type
var terms termlist
switch t := under(typ).(type) {
case *Interface:
tset := computeTypeSet(check, pos, t)
tset := computeInterfaceTypeSet(check, pos, t)
if tset.comparable {
ityp.tset.comparable = true
}
for _, m := range tset.methods {
addMethod(pos, m, false) // use embedding position pos rather than m.pos
}
types = tset.types
terms = tset.terms
case *Union:
// TODO(gri) combine with default case once we have
// converted all tests to new notation and we
// can report an error when we don't have an
// interface before go1.18.
types = typ
tset := computeUnionTypeSet(check, pos, t)
terms = tset.terms
case *TypeParam:
// Embedding stand-alone type parameters is not permitted for now.
// Embedding stand-alone type parameters is not permitted.
// This case is handled during union parsing.
unreachable()
default:
@ -253,9 +291,11 @@ func computeTypeSet(check *Checker, pos token.Pos, ityp *Interface) *_TypeSet {
check.errorf(atPos(pos), _InvalidIfaceEmbed, "%s is not an interface", typ)
continue
}
types = typ
terms = termlist{{false, typ}}
}
allTypes = intersect(allTypes, types)
// The type set of an interface is the intersection
// of the type sets of all its elements.
allTerms = allTerms.intersect(terms)
}
ityp.embedPos = nil // not needed anymore (errors have been reported)
@ -272,7 +312,7 @@ func computeTypeSet(check *Checker, pos token.Pos, ityp *Interface) *_TypeSet {
sort.Sort(byUniqueMethodName(methods))
ityp.tset.methods = methods
}
ityp.tset.types = allTypes
ityp.tset.terms = allTerms
return ityp.tset
}
@ -296,3 +336,34 @@ type byUniqueMethodName []*Func
func (a byUniqueMethodName) Len() int { return len(a) }
func (a byUniqueMethodName) Less(i, j int) bool { return a[i].Id() < a[j].Id() }
func (a byUniqueMethodName) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
// computeUnionTypeSet may be called with check == nil.
func computeUnionTypeSet(check *Checker, pos token.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:
terms = termlist{t}
}
// The type set of a union expression is the union
// of the type sets of each term.
allTerms = allTerms.union(terms)
}
utyp.tset.terms = allTerms
return utyp.tset
}

23
src/go/types/typestring.go
View File

@ -159,9 +159,10 @@ func writeType(buf *bytes.Buffer, typ Type, qf Qualifier, visited []Type) {
writeSignature(buf, t, qf, visited)
case *Union:
if t.IsEmpty() {
buf.WriteString("⊥")
break
// Unions only appear as (syntactic) embedded elements
// in interfaces and syntactically cannot be empty.
if t.NumTerms() == 0 {
panic("internal error: empty union")
}
for i, t := range t.terms {
if i > 0 {
@ -199,13 +200,21 @@ func writeType(buf *bytes.Buffer, typ Type, qf Qualifier, visited []Type) {
writeSignature(buf, m.typ.(*Signature), qf, visited)
empty = false
}
if !empty && tset.types != nil {
if !empty && tset.hasTerms() {
buf.WriteString("; ")
}
if tset.types != nil {
buf.WriteString("type ")
writeType(buf, tset.types, qf, visited)
first := true
tset.is(func(t *term) bool {
if !first {
buf.WriteByte('|')
}
first = false
if t.tilde {
buf.WriteByte('~')
}
writeType(buf, t.typ, qf, visited)
return true
})
} else {
// print explicit interface methods and embedded types
for i, m := range t.methods {

19
src/go/types/typexpr.go
View File

@ -145,19 +145,18 @@ func (check *Checker) varType(e ast.Expr) Type {
// ordinaryType reports an error if typ is an interface type containing
// type lists or is (or embeds) the predeclared type comparable.
func (check *Checker) ordinaryType(pos positioner, typ Type) {
// We don't want to call under() (via asInterface) or complete interfaces
// while we are in the middle of type-checking parameter declarations that
// might belong to interface methods. Delay this check to the end of
// type-checking.
// We don't want to call under() (via asInterface) or complete interfaces while we
// are in the middle of type-checking parameter declarations that might belong to
// interface methods. Delay this check to the end of type-checking.
check.later(func() {
if t := asInterface(typ); t != nil {
tset := computeTypeSet(check, pos.Pos(), t) // TODO(gri) is this the correct position?
if tset.types != nil {
check.softErrorf(pos, _Todo, "interface contains type constraints (%s)", tset.types)
return
}
if tset.IsComparable() {
tset := computeInterfaceTypeSet(check, pos.Pos(), t) // TODO(gri) is this the correct position?
if !tset.IsMethodSet() {
if tset.comparable {
check.softErrorf(pos, _Todo, "interface is (or embeds) comparable")
} else {
check.softErrorf(pos, _Todo, "interface contains type constraints")
}
}
}
})

5
src/go/types/unify.go
View File

@ -358,9 +358,6 @@ func (u *unifier) nify(x, y Type, p *ifacePair) bool {
u.nify(x.results, y.results, p)
}
case *Union:
panic("unimplemented: unification with type sets described by types")
case *Interface:
// Two interface types are identical if they have the same set of methods with
// the same names and identical function types. Lower-case method names from
@ -368,7 +365,7 @@ func (u *unifier) nify(x, y Type, p *ifacePair) bool {
if y, ok := y.(*Interface); ok {
xset := x.typeSet()
yset := y.typeSet()
if !Identical(xset.types, yset.types) {
if !xset.terms.equal(yset.terms) {
return false
}
a := xset.methods

209
src/go/types/union.go
View File

@ -12,14 +12,15 @@ import (
// ----------------------------------------------------------------------------
// API
// A Union represents a union of terms.
// A Union represents a union of terms embedded in an interface.
type Union struct {
terms []*term
terms []*term // list of syntactical terms (not a canonicalized termlist)
tset *_TypeSet // type set described by this union, computed lazily
}
// NewUnion returns a new Union type with the given terms (types[i], tilde[i]).
// The lengths of both arguments must match. An empty union represents the set
// of no types.
// The lengths of both arguments must match. It is an error to create an empty
// union; they are syntactically not possible.
func NewUnion(types []Type, tilde []bool) *Union { return newUnion(types, tilde) }
func (u *Union) IsEmpty() bool { return len(u.terms) == 0 }
@ -32,12 +33,10 @@ func (u *Union) String() string { return TypeString(u, nil) }
// ----------------------------------------------------------------------------
// Implementation
var emptyUnion = new(Union)
func newUnion(types []Type, tilde []bool) *Union {
assert(len(types) == len(tilde))
if len(types) == 0 {
return emptyUnion
panic("empty union")
}
t := new(Union)
t.terms = make([]*term, len(types))
@ -47,52 +46,23 @@ func newUnion(types []Type, tilde []bool) *Union {
return t
}
// is reports whether f returns true for all terms of u.
func (u *Union) is(f func(*term) bool) bool {
if u.IsEmpty() {
return false
}
for _, t := range u.terms {
if !f(t) {
return false
}
}
return true
}
// underIs reports whether f returned true for the underlying types of all terms of u.
func (u *Union) underIs(f func(Type) bool) bool {
if u.IsEmpty() {
return false
}
for _, t := range u.terms {
if !f(under(t.typ)) {
return false
}
}
return true
}
func parseUnion(check *Checker, tlist []ast.Expr) Type {
var types []Type
var tilde []bool
var terms []*term
for _, x := range tlist {
t, d := parseTilde(check, x)
if len(tlist) == 1 && !d {
return t // single type
tilde, typ := parseTilde(check, x)
if len(tlist) == 1 && !tilde {
return typ // single type
}
types = append(types, t)
tilde = append(tilde, d)
terms = append(terms, &term{tilde, typ})
}
// Ensure that each type is only present once in the type list.
// It's ok to do this check later because it's not a requirement
// for correctness of the code.
// Check validity of terms.
// Do this check later because it requires types to be set up.
// Note: This is a quadratic algorithm, but unions tend to be short.
check.later(func() {
for i, t := range types {
t := expand(t)
if t == Typ[Invalid] {
for i, t := range terms {
typ := expand(t.typ)
if typ == Typ[Invalid] {
continue
}
@ -108,16 +78,16 @@ func parseUnion(check *Checker, tlist []ast.Expr) Type {
}
}
u := under(t)
u := under(typ)
f, _ := u.(*Interface)
if tilde[i] {
if t.tilde {
if f != nil {
check.errorf(x, _Todo, "invalid use of ~ (%s is an interface)", t)
check.errorf(x, _Todo, "invalid use of ~ (%s is an interface)", typ)
continue // don't report another error for t
}
if !Identical(u, t) {
check.errorf(x, _Todo, "invalid use of ~ (underlying type of %s is %s)", t, u)
if !Identical(u, typ) {
check.errorf(x, _Todo, "invalid use of ~ (underlying type of %s is %s)", typ, u)
continue // don't report another error for t
}
}
@ -130,19 +100,18 @@ func parseUnion(check *Checker, tlist []ast.Expr) Type {
continue // don't report another error for t
}
// Complain about duplicate entries a|a, but also a|~a, and ~a|~a.
// TODO(gri) We should also exclude myint|~int since myint is included in ~int.
if includes(types[:i], t) {
// TODO(rfindley) this currently doesn't print the ~ if present
check.softErrorf(atPos(pos), _Todo, "duplicate term %s in union element", t)
// Report overlapping (non-disjoint) terms such as
// a|a, a|~a, ~a|~a, and ~a|A (where under(A) == a).
if j := overlappingTerm(terms[:i], t); j >= 0 {
check.softErrorf(atPos(pos), _Todo, "overlapping terms %s and %s", t, terms[j])
}
}
})
return newUnion(types, tilde)
return &Union{terms, nil}
}
func parseTilde(check *Checker, x ast.Expr) (typ Type, tilde bool) {
func parseTilde(check *Checker, x ast.Expr) (tilde bool, typ Type) {
if op, _ := x.(*ast.UnaryExpr); op != nil && op.Op == token.TILDE {
x = op.X
tilde = true
@ -156,116 +125,20 @@ func parseTilde(check *Checker, x ast.Expr) (typ Type, tilde bool) {
return
}
// intersect computes the intersection of the types x and y,
// A nil type stands for the set of all types; an empty union
// stands for the set of no types.
func intersect(x, y Type) (r Type) {
// If one of the types is nil (no restrictions)
// the result is the other type.
switch {
case x == nil:
return y
case y == nil:
return x
}
// Compute the terms which are in both x and y.
// TODO(gri) This is not correct as it may not always compute
// the "largest" intersection. For instance, for
// x = myInt|~int, y = ~int
// we get the result myInt but we should get ~int.
xu, _ := x.(*Union)
yu, _ := y.(*Union)
switch {
case xu != nil && yu != nil:
return &Union{intersectTerms(xu.terms, yu.terms)}
case xu != nil:
if r, _ := xu.intersect(y, false); r != nil {
return y
}
case yu != nil:
if r, _ := yu.intersect(x, false); r != nil {
return x
}
default: // xu == nil && yu == nil
if Identical(x, y) {
return x
// overlappingTerm reports the index of the term x in terms which is
// overlapping (not disjoint) from y. The result is < 0 if there is no
// such term.
func overlappingTerm(terms []*term, y *term) int {
for i, x := range terms {
// disjoint requires non-nil, non-top arguments
if debug {
if x == nil || x.typ == nil || y == nil || y.typ == nil {
panic("internal error: empty or top union term")
}
}
return emptyUnion
}
// includes reports whether typ is in list.
func includes(list []Type, typ Type) bool {
for _, e := range list {
if Identical(typ, e) {
return true
}
}
return false
}
// intersect computes the intersection of the union u and term (y, yt)
// and returns the intersection term, if any. Otherwise the result is
// (nil, false).
// TODO(gri) this needs to cleaned up/removed once we switch to lazy
// union type set computation.
func (u *Union) intersect(y Type, yt bool) (Type, bool) {
under_y := under(y)
for _, x := range u.terms {
xt := x.tilde
// determine which types xx, yy to compare
xx := x.typ
if yt {
xx = under(xx)
}
yy := y
if xt {
yy = under_y
}
if Identical(xx, yy) {
// T ∩ T = T
// T ∩ ~t = T
// ~t ∩ T = T
// ~t ∩ ~t = ~t
return xx, xt && yt
}
}
return nil, false
}
func identicalTerms(list1, list2 []*term) bool {
if len(list1) != len(list2) {
return false
}
// Every term in list1 must be in list2.
// Quadratic algorithm, but probably good enough for now.
// TODO(gri) we need a fast quick type ID/hash for all types.
L:
for _, x := range list1 {
for _, y := range list2 {
if x.equal(y) {
continue L // x is in list2
}
}
return false
}
return true
}
func intersectTerms(list1, list2 []*term) (list []*term) {
// Quadratic algorithm, but good enough for now.
// TODO(gri) fix asymptotic performance
for _, x := range list1 {
for _, y := range list2 {
if r := x.intersect(y); r != nil {
list = append(list, r)
}
}
}
return
if !x.disjoint(y) {
return i
}
}
return -1
}

4
src/go/types/universe.go
View File

@ -90,7 +90,7 @@ func defPredeclaredTypes() {
sig := NewSignature(nil, nil, NewTuple(res), false)
err := NewFunc(token.NoPos, nil, "Error", sig)
ityp := &Interface{obj, []*Func{err}, nil, nil, true, nil}
computeTypeSet(nil, token.NoPos, ityp) // prevent races due to lazy computation of tset
computeInterfaceTypeSet(nil, token.NoPos, ityp) // prevent races due to lazy computation of tset
typ := NewNamed(obj, ityp, nil)
sig.recv = NewVar(token.NoPos, nil, "", typ)
def(obj)
@ -100,7 +100,7 @@ func defPredeclaredTypes() {
{
obj := NewTypeName(token.NoPos, nil, "comparable", nil)
obj.setColor(black)
ityp := &Interface{obj, nil, nil, nil, true, &_TypeSet{true, nil, nil}}
ityp := &Interface{obj, nil, nil, nil, true, &_TypeSet{true, nil, topTermlist}}
NewNamed(obj, ityp, nil)
def(obj)
}