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go/types: merge Named type loading and expansion

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Named type expansion and loading were conceptually similar: a mechanism
for lazily resolving type information in a concurrency-safe manner.
Unify them into a 'resolve' method, that delegates to a resolver func to
produce type parameters, underlying, and methods.

By leveraging the sync.Once field on Named for instance expansion, we
get closer to making instance expansion concurrency-safe, and remove the
requirement that instPos guard instantiation. This will be cleaned up
in a follow-up CL.

This also fixes #47887 by causing substituted type instances to be
expanded (in the old code, this could be fixed by setting instPos when
substituting).

For #47910
Fixes #47887

Change-Id: Ifc52a420dde76e3a46ce494fea9bd289bc8aca4c
Reviewed-on: https://go-review.googlesource.com/c/go/+/349410
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 2021-09-10 10:23:23 -04:00
parent 137543bb93
commit 2933c451a0
9 changed files with 114 additions and 96 deletions
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4
src/go/types/decl.go
View File

@ -316,7 +316,7 @@ func (check *Checker) validType(typ Type, path []Object) typeInfo {
}
case *Named:
t.expand(check.conf.Environment)
t.resolve(check.conf.Environment)
// don't touch the type if it is from a different package or the Universe scope
// (doing so would lead to a race condition - was issue #35049)
if t.obj.pkg != check.pkg {
@ -773,7 +773,7 @@ func (check *Checker) collectMethods(obj *TypeName) {
}
if base != nil {
base.load() // TODO(mdempsky): Probably unnecessary.
base.resolve(nil) // TODO(mdempsky): Probably unnecessary.
base.methods = append(base.methods, m)
}
}

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

@ -116,9 +116,10 @@ func (check *Checker) instance(pos token.Pos, typ Type, targs []Type, env *Envir
}
}
tname := NewTypeName(pos, t.obj.pkg, t.obj.name, nil)
named := check.newNamed(tname, t, nil, nil, nil) // methods and tparams are set when named is loaded
named := check.newNamed(tname, t, nil, nil, nil) // methods and tparams are set when named is resolved
named.targs = NewTypeList(targs)
named.instPos = &pos
named.resolver = expandNamed
if env != nil {
// It's possible that we've lost a race to add named to the environment.
// In this case, use whichever instance is recorded in the environment.

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

@ -124,7 +124,7 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
seen[named] = true
// look for a matching attached method
named.load()
named.resolve(nil)
if i, m := lookupMethod(named.methods, pkg, name); m != nil {
// potential match
// caution: method may not have a proper signature yet

114
src/go/types/named.go
View File

@ -22,8 +22,9 @@ type Named struct {
targs *TypeList // type arguments (after instantiation), or nil
methods []*Func // methods declared for this type (not the method set of this type); signatures are type-checked lazily
resolve func(*Named) ([]*TypeParam, Type, []*Func)
once sync.Once
// resolver may be provided to lazily resolve type parameters, underlying, and methods.
resolver func(*Environment, *Named) (tparams *TypeParamList, underlying Type, methods []*Func)
once sync.Once // ensures that tparams, underlying, and methods are resolved before accessing
}
// NewNamed returns a new named type for the given type name, underlying type, and associated methods.
@ -36,43 +37,22 @@ func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
return (*Checker)(nil).newNamed(obj, nil, underlying, nil, methods)
}
func (t *Named) load() *Named {
// If t is an instantiated type, it derives its methods and tparams from its
// base type. Since we expect type parameters and methods to be set after a
// call to load, we must load the base and copy here.
//
// underlying is set when t is expanded.
//
// By convention, a type instance is loaded iff its tparams are set.
if t.targs.Len() > 0 && t.tparams == nil {
t.orig.load()
t.tparams = t.orig.tparams
t.methods = t.orig.methods
}
if t.resolve == nil {
func (t *Named) resolve(env *Environment) *Named {
if t.resolver == nil {
return t
}
t.once.Do(func() {
// TODO(mdempsky): Since we're passing t to resolve anyway
// TODO(mdempsky): Since we're passing t to the resolver anyway
// (necessary because types2 expects the receiver type for methods
// on defined interface types to be the Named rather than the
// underlying Interface), maybe it should just handle calling
// SetTypeParams, SetUnderlying, and AddMethod instead? Those
// methods would need to support reentrant calls though. It would
// methods would need to support reentrant calls though. It would
// also make the API more future-proof towards further extensions
// (like SetTypeParams).
tparams, underlying, methods := t.resolve(t)
switch underlying.(type) {
case nil, *Named:
panic("invalid underlying type")
}
t.tparams = bindTParams(tparams)
t.underlying = underlying
t.methods = methods
t.tparams, t.underlying, t.methods = t.resolver(env, t)
t.fromRHS = t.underlying // for cycle detection
})
return t
}
@ -121,19 +101,19 @@ func (t *Named) _Orig() *Named { return t.orig }
// TypeParams returns the type parameters of the named type t, or nil.
// The result is non-nil for an (originally) parameterized type even if it is instantiated.
func (t *Named) TypeParams() *TypeParamList { return t.load().tparams }
func (t *Named) TypeParams() *TypeParamList { return t.resolve(nil).tparams }
// SetTypeParams sets the type parameters of the named type t.
func (t *Named) SetTypeParams(tparams []*TypeParam) { t.load().tparams = bindTParams(tparams) }
func (t *Named) SetTypeParams(tparams []*TypeParam) { t.resolve(nil).tparams = bindTParams(tparams) }
// TypeArgs returns the type arguments used to instantiate the named type t.
func (t *Named) TypeArgs() *TypeList { return t.targs }
// NumMethods returns the number of explicit methods whose receiver is named type t.
func (t *Named) NumMethods() int { return len(t.load().methods) }
func (t *Named) NumMethods() int { return len(t.resolve(nil).methods) }
// Method returns the i'th method of named type t for 0 <= i < t.NumMethods().
func (t *Named) Method(i int) *Func { return t.load().methods[i] }
func (t *Named) Method(i int) *Func { return t.resolve(nil).methods[i] }
// SetUnderlying sets the underlying type and marks t as complete.
func (t *Named) SetUnderlying(underlying Type) {
@ -143,18 +123,18 @@ func (t *Named) SetUnderlying(underlying Type) {
if _, ok := underlying.(*Named); ok {
panic("underlying type must not be *Named")
}
t.load().underlying = underlying
t.resolve(nil).underlying = underlying
}
// AddMethod adds method m unless it is already in the method list.
func (t *Named) AddMethod(m *Func) {
t.load()
t.resolve(nil)
if i, _ := lookupMethod(t.methods, m.pkg, m.name); i < 0 {
t.methods = append(t.methods, m)
}
}
func (t *Named) Underlying() Type { return t.load().expand(nil).underlying }
func (t *Named) Underlying() Type { return t.resolve(nil).underlying }
func (t *Named) String() string { return TypeString(t, nil) }
// ----------------------------------------------------------------------------
@ -240,43 +220,37 @@ func (n *Named) setUnderlying(typ Type) {
}
}
// expand ensures that the underlying type of n is instantiated.
// expandNamed ensures that the underlying type of n is instantiated.
// The underlying type will be Typ[Invalid] if there was an error.
func (n *Named) expand(env *Environment) *Named {
if n.instPos != nil {
// n must be loaded before instantiation, in order to have accurate
// tparams. This is done implicitly by the call to n.TypeParams, but making
// it explicit is harmless: load is idempotent.
n.load()
var u Type
if n.check.validateTArgLen(*n.instPos, n.tparams.Len(), n.targs.Len()) {
// TODO(rfindley): handling an optional Checker and Environment here (and
// in subst) feels overly complicated. Can we simplify?
if env == nil {
if n.check != nil {
env = n.check.conf.Environment
} else {
// If we're instantiating lazily, we might be outside the scope of a
// type-checking pass. In that case we won't have a pre-existing
// environment, but don't want to create a duplicate of the current
// instance in the process of expansion.
env = NewEnvironment()
}
h := env.typeHash(n.orig, n.targs.list())
// add the instance to the environment to avoid infinite recursion.
// addInstance may return a different, existing instance, but we
// shouldn't return that instance from expand.
env.typeForHash(h, n)
func expandNamed(env *Environment, n *Named) (*TypeParamList, Type, []*Func) {
n.orig.resolve(env)
var u Type
if n.check.validateTArgLen(*n.instPos, n.orig.tparams.Len(), n.targs.Len()) {
// TODO(rfindley): handling an optional Checker and Environment here (and
// in subst) feels overly complicated. Can we simplify?
if env == nil {
if n.check != nil {
env = n.check.conf.Environment
} else {
// If we're instantiating lazily, we might be outside the scope of a
// type-checking pass. In that case we won't have a pre-existing
// environment, but don't want to create a duplicate of the current
// instance in the process of expansion.
env = NewEnvironment()
}
u = n.check.subst(*n.instPos, n.orig.underlying, makeSubstMap(n.TypeParams().list(), n.targs.list()), env)
} else {
u = Typ[Invalid]
h := env.typeHash(n.orig, n.targs.list())
// add the instance to the environment to avoid infinite recursion.
// addInstance may return a different, existing instance, but we
// shouldn't return that instance from expand.
env.typeForHash(h, n)
}
n.underlying = u
n.fromRHS = u
n.instPos = nil
u = n.check.subst(*n.instPos, n.orig.underlying, makeSubstMap(n.orig.tparams.list(), n.targs.list()), env)
} else {
u = Typ[Invalid]
}
return n
n.instPos = nil
return n.orig.tparams, u, n.orig.methods
}
// safeUnderlying returns the underlying of typ without expanding instances, to
@ -285,7 +259,7 @@ func (n *Named) expand(env *Environment) *Named {
// TODO(rfindley): eliminate this function or give it a better name.
func safeUnderlying(typ Type) Type {
if t, _ := typ.(*Named); t != nil {
return t.load().underlying
return t.resolve(nil).underlying
}
return typ.Underlying()
}

16
src/go/types/object.go
View File

@ -232,9 +232,21 @@ func NewTypeName(pos token.Pos, pkg *Package, name string, typ Type) *TypeName {
// _NewTypeNameLazy returns a new defined type like NewTypeName, but it
// lazily calls resolve to finish constructing the Named object.
func _NewTypeNameLazy(pos token.Pos, pkg *Package, name string, resolve func(named *Named) (tparams []*TypeParam, underlying Type, methods []*Func)) *TypeName {
func _NewTypeNameLazy(pos token.Pos, pkg *Package, name string, load func(named *Named) (tparams []*TypeParam, underlying Type, methods []*Func)) *TypeName {
obj := NewTypeName(pos, pkg, name, nil)
NewNamed(obj, nil, nil).resolve = resolve
resolve := func(_ *Environment, t *Named) (*TypeParamList, Type, []*Func) {
tparams, underlying, methods := load(t)
switch underlying.(type) {
case nil, *Named:
panic(fmt.Sprintf("invalid underlying type %T", t.underlying))
}
return bindTParams(tparams), underlying, methods
}
NewNamed(obj, nil, nil).resolver = resolve
return obj
}

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

@ -200,7 +200,7 @@ func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast
var err string
switch T := rtyp.(type) {
case *Named:
T.expand(nil)
T.resolve(check.conf.Environment)
// The receiver type may be an instantiated type referred to
// by an alias (which cannot have receiver parameters for now).
if T.TypeArgs() != nil && sig.RecvTypeParams() == nil {

39
src/go/types/subst.go
View File

@ -182,13 +182,19 @@ func (subst *subster) typ(typ Type) Type {
}
}
if t.TypeParams().Len() == 0 {
// subst is called by expandNamed, so in this function we need to be
// careful not to call any methods that would cause t to be expanded: doing
// so would result in deadlock.
//
// So we call t.orig.TypeParams() rather than t.TypeParams() here and
// below.
if t.orig.TypeParams().Len() == 0 {
dump(">>> %s is not parameterized", t)
return t // type is not parameterized
}
var newTArgs []Type
assert(t.targs.Len() == t.TypeParams().Len())
assert(t.targs.Len() == t.orig.TypeParams().Len())
// already instantiated
dump(">>> %s already instantiated", t)
@ -201,7 +207,7 @@ func (subst *subster) typ(typ Type) Type {
if new_targ != targ {
dump(">>> substituted %d targ %s => %s", i, targ, new_targ)
if newTArgs == nil {
newTArgs = make([]Type, t.TypeParams().Len())
newTArgs = make([]Type, t.orig.TypeParams().Len())
copy(newTArgs, t.targs.list())
}
newTArgs[i] = new_targ
@ -221,25 +227,22 @@ func (subst *subster) typ(typ Type) Type {
return named
}
// Create a new named type and populate the environment to avoid endless
t.orig.resolve(subst.env)
// Create a new instance and populate the environment to avoid endless
// recursion. The position used here is irrelevant because validation only
// occurs on t (we don't call validType on named), but we use subst.pos to
// help with debugging.
tname := NewTypeName(subst.pos, t.obj.pkg, t.obj.name, nil)
t.load()
// It's ok to provide a nil *Checker because the newly created type
// doesn't need to be (lazily) expanded; it's expanded below.
named := (*Checker)(nil).newNamed(tname, t.orig, nil, t.tparams, t.methods) // t is loaded, so tparams and methods are available
named.targs = NewTypeList(newTArgs)
subst.env.typeForHash(h, named)
t.expand(subst.env) // must happen after env update to avoid infinite recursion
// do the substitution
dump(">>> subst %s with %s (new: %s)", t.underlying, subst.smap, newTArgs)
named.underlying = subst.typOrNil(t.underlying)
dump(">>> underlying: %v", named.underlying)
named := subst.check.instance(subst.pos, t.orig, newTArgs, subst.env).(*Named)
// TODO(rfindley): we probably don't need to resolve here. Investigate if
// this can be removed.
named.resolve(subst.env)
assert(named.underlying != nil)
named.fromRHS = named.underlying // for consistency, though no cycle detection is necessary
// Note that if we were to expose substitution more generally (not just in
// the context of a declaration), we'd have to substitute in
// named.underlying as well.
//
// But this is unnecessary for now.
return named

28
src/go/types/testdata/fixedbugs/issue47887.go2 vendored Normal file
View File

@ -0,0 +1,28 @@
// 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 p
type Fooer[t any] interface {
foo(Barer[t])
}
type Barer[t any] interface {
bar(Bazer[t])
}
type Bazer[t any] interface {
Fooer[t]
baz(t)
}
type Int int
func (n Int) baz(int) {}
func (n Int) foo(b Barer[int]) { b.bar(n) }
type F[t any] interface { f(G[t]) }
type G[t any] interface { g(H[t]) }
type H[t any] interface { F[t] }
type T struct{}
func (n T) f(b G[T]) { b.g(n) }

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

@ -114,7 +114,7 @@ func asInterface(t Type) *Interface {
func asNamed(t Type) *Named {
e, _ := t.(*Named)
if e != nil {
e.expand(nil)
e.resolve(nil)
}
return e
}