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[dev.typeparams] cmd/compile/internal/types2: merge instance and Named to eliminate sanitization

Browse source 
This is a port of CL 335929 to types2. It differs significantly from
that CL to handle lazy loading, which wasn't tested in go/types.
Additionally, the *Checker field was moved out of instance and back
onto Named. This way we can tell whether a Named type is uninstantiated
simply by checking whether Named.instance is non-nil, which simplified
the code considerably.

Fixes #46151

Change-Id: I617263bcfaa768ac5442213cecad8d567c2749fc
Reviewed-on: https://go-review.googlesource.com/c/go/+/336252
Trust: Robert Findley <rfindley@google.com>
Trust: Robert Griesemer <gri@golang.org>
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:
Rob Findley 2021-07-21 12:12:22 -04:00 committed by Robert Findley
parent e00a6ec084
commit 473e493d18
17 changed files with 127 additions and 329 deletions
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2
src/cmd/compile/internal/types2/builtins.go
View file

@ -798,7 +798,7 @@ func hasVarSize(t Type) bool {
}
case *TypeParam:
return true
case *Named, *Union, *instance, *top:
case *Named, *Union, *top:
unreachable()
}
return false

5
src/cmd/compile/internal/types2/check.go
View file

@ -282,11 +282,6 @@ func (check *Checker) checkFiles(files []*syntax.File) (err error) {
print("== recordUntyped ==")
check.recordUntyped()
if check.Info != nil {
print("== sanitizeInfo ==")
sanitizeInfo(check.Info)
}
check.pkg.complete = true
// no longer needed - release memory

12
src/cmd/compile/internal/types2/decl.go
View file

@ -317,6 +317,8 @@ func (check *Checker) validType(typ Type, path []Object) typeInfo {
}
case *Named:
t.expand()
// 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 {
@ -349,9 +351,6 @@ func (check *Checker) validType(typ Type, path []Object) typeInfo {
panic("internal error: cycle start not found")
}
return t.info
case *instance:
return check.validType(t.expand(), path)
}
return valid
@ -557,7 +556,7 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *Named
// determine underlying type of named
named.fromRHS = check.definedType(tdecl.Type, named)
assert(named.fromRHS != nil)
// The underlying type of named may be itself a named type that is
// incomplete:
//
@ -624,7 +623,8 @@ func (check *Checker) boundType(e syntax.Expr) Type {
bound := check.typ(e)
check.later(func() {
if _, ok := under(bound).(*Interface); !ok && bound != Typ[Invalid] {
u := under(bound)
if _, ok := u.(*Interface); !ok && u != Typ[Invalid] {
check.errorf(e, "%s is not an interface", bound)
}
})
@ -692,7 +692,7 @@ func (check *Checker) collectMethods(obj *TypeName) {
}
if base != nil {
base.expand() // TODO(mdempsky): Probably unnecessary.
base.load() // TODO(mdempsky): Probably unnecessary.
base.methods = append(base.methods, m)
}
}

3
src/cmd/compile/internal/types2/infer.go
View file

@ -342,9 +342,6 @@ func (w *tpWalker) isParameterized(typ Type) (res bool) {
// t must be one of w.tparams
return t.index < len(w.tparams) && w.tparams[t.index].typ == t
case *instance:
return w.isParameterizedList(t.targs)
default:
unreachable()
}

62
src/cmd/compile/internal/types2/instance.go
View file

@ -4,56 +4,40 @@
package types2
// TODO(rfindley): move this code to named.go.
import "cmd/compile/internal/syntax"
// An instance represents an instantiated generic type syntactically
// (without expanding the instantiation). Type instances appear only
// during type-checking and are replaced by their fully instantiated
// (expanded) types before the end of type-checking.
// instance holds position information for use in lazy instantiation.
//
// TODO(rfindley): come up with a better name for this type, now that its usage
// has changed.
type instance struct {
check *Checker // for lazy instantiation
pos syntax.Pos // position of type instantiation; for error reporting only
base *Named // parameterized type to be instantiated
targs []Type // type arguments
posList []syntax.Pos // position of each targ; for error reporting only
verify bool // if set, constraint satisfaction is verified
value Type // base[targs...] after instantiation or Typ[Invalid]; nil if not yet set
verify bool // if set, check constraint satisfaction upon instantiation
}
// expand returns the instantiated (= expanded) type of t.
// The result is either an instantiated *Named type, or
// Typ[Invalid] if there was an error.
func (t *instance) expand() Type {
v := t.value
if v == nil {
v = t.check.Instantiate(t.pos, t.base, t.targs, t.posList, t.verify)
if v == nil {
v = Typ[Invalid]
}
t.value = v
// expand 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() {
if n.instance != nil {
// n must be loaded before instantiation, in order to have accurate
// tparams. This is done implicitly by the call to n.TParams, but making it
// explicit is harmless: load is idempotent.
n.load()
inst := n.check.instantiate(n.instance.pos, n.orig.underlying, n.TParams(), n.targs, n.instance.posList, n.instance.verify)
n.underlying = inst
n.fromRHS = inst
n.instance = nil
}
// After instantiation we must have an invalid or a *Named type.
if debug && v != Typ[Invalid] {
_ = v.(*Named)
}
return v
}
// expand expands a type instance into its instantiated
// type and leaves all other types alone. expand does
// not recurse.
// expand expands uninstantiated named types and leaves all other types alone.
// expand does not recurse.
func expand(typ Type) Type {
if t, _ := typ.(*instance); t != nil {
return t.expand()
if t, _ := typ.(*Named); t != nil {
t.expand()
}
return typ
}
// expandf is set to expand.
// Call expandf when calling expand causes compile-time cycle error.
var expandf func(Type) Type
func init() { expandf = expand }
func (t *instance) Underlying() Type { return t }
func (t *instance) String() string { return TypeString(t, nil) }

72
src/cmd/compile/internal/types2/instantiate.go
View file

@ -25,28 +25,6 @@ import (
// Any methods attached to a *Named are simply copied; they are not
// instantiated.
func (check *Checker) Instantiate(pos syntax.Pos, typ Type, targs []Type, posList []syntax.Pos, verify bool) (res Type) {
if verify && check == nil {
panic("cannot have nil receiver if verify is set")
}
if check != nil && check.conf.Trace {
check.trace(pos, "-- instantiating %s with %s", typ, typeListString(targs))
check.indent++
defer func() {
check.indent--
var under Type
if res != nil {
// Calling under() here may lead to endless instantiations.
// Test case: type T[P any] T[P]
// TODO(gri) investigate if that's a bug or to be expected.
under = res.Underlying()
}
check.trace(pos, "=> %s (under = %s)", res, under)
}()
}
assert(len(posList) <= len(targs))
// TODO(gri) What is better here: work with TypeParams, or work with TypeNames?
var tparams []*TypeName
switch t := typ.(type) {
@ -76,7 +54,10 @@ func (check *Checker) Instantiate(pos syntax.Pos, typ Type, targs []Type, posLis
// only types and functions can be generic
panic(fmt.Sprintf("%v: cannot instantiate %v", pos, typ))
}
return check.instantiate(pos, typ, tparams, targs, posList, verify)
}
func (check *Checker) instantiate(pos syntax.Pos, typ Type, tparams []*TypeName, targs []Type, posList []syntax.Pos, verify bool) (res Type) {
// the number of supplied types must match the number of type parameters
if len(targs) != len(tparams) {
// TODO(gri) provide better error message
@ -86,6 +67,27 @@ func (check *Checker) Instantiate(pos syntax.Pos, typ Type, targs []Type, posLis
}
panic(fmt.Sprintf("%v: got %d arguments but %d type parameters", pos, len(targs), len(tparams)))
}
if verify && check == nil {
panic("cannot have nil receiver if verify is set")
}
if check != nil && check.conf.Trace {
check.trace(pos, "-- instantiating %s with %s", typ, typeListString(targs))
check.indent++
defer func() {
check.indent--
var under Type
if res != nil {
// Calling under() here may lead to endless instantiations.
// Test case: type T[P any] T[P]
// TODO(gri) investigate if that's a bug or to be expected.
under = res.Underlying()
}
check.trace(pos, "=> %s (under = %s)", res, under)
}()
}
assert(len(posList) <= len(targs))
if len(tparams) == 0 {
return typ // nothing to do (minor optimization)
@ -115,19 +117,35 @@ func (check *Checker) Instantiate(pos syntax.Pos, typ Type, targs []Type, posLis
// instantiating the type until needed. typ must be a *Named
// type.
func (check *Checker) InstantiateLazy(pos syntax.Pos, typ Type, targs []Type, posList []syntax.Pos, verify bool) Type {
base := asNamed(typ)
// Don't use asNamed here: we don't want to expand the base during lazy
// instantiation.
base := typ.(*Named)
if base == nil {
panic(fmt.Sprintf("%v: cannot instantiate %v", pos, typ))
}
h := instantiatedHash(base, targs)
if check != nil {
// typ may already have been instantiated with identical type arguments. In
// that case, re-use the existing instance.
if named := check.typMap[h]; named != nil {
return named
}
}
return &instance{
check: check,
tname := NewTypeName(pos, base.obj.pkg, base.obj.name, nil)
named := check.newNamed(tname, base, nil, nil, nil) // methods and tparams are set when named is loaded.
named.targs = targs
named.instance = &instance{
pos: pos,
base: base,
targs: targs,
posList: posList,
verify: verify,
}
if check != nil {
check.typMap[h] = named
}
return named
}
// satisfies reports whether the type argument targ satisfies the constraint of type parameter

2
src/cmd/compile/internal/types2/lookup.go
View file

@ -119,7 +119,7 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
seen[named] = true
// look for a matching attached method
named.expand()
named.load()
if i, m := lookupMethod(named.methods, pkg, name); m != nil {
// potential match
// caution: method may not have a proper signature yet

45
src/cmd/compile/internal/types2/named.go
View file

@ -10,12 +10,13 @@ import "sync"
// A Named represents a named (defined) type.
type Named struct {
check *Checker // for Named.under implementation; nilled once under has been called
check *Checker
info typeInfo // for cycle detection
obj *TypeName // corresponding declared object
orig *Named // original, uninstantiated type
fromRHS Type // type (on RHS of declaration) this *Named type is derived from (for cycle reporting)
underlying Type // possibly a *Named during setup; never a *Named once set up completely
instance *instance // position information for lazy instantiation, or nil
tparams []*TypeName // type parameters, or nil
targs []Type // 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
@ -34,7 +35,19 @@ func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
return (*Checker)(nil).newNamed(obj, nil, underlying, nil, methods)
}
func (t *Named) expand() *Named {
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 len(t.targs) > 0 && t.tparams == nil {
t.orig.load()
t.tparams = t.orig.tparams
t.methods = t.orig.methods
}
if t.resolve == nil {
return t
}
@ -83,7 +96,7 @@ func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, tpar
if check != nil {
check.later(func() {
switch typ.under().(type) {
case *Named, *instance:
case *Named:
panic("internal error: unexpanded underlying type")
}
typ.check = nil
@ -104,10 +117,12 @@ func (t *Named) Orig() *Named { return t.orig }
// TParams 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) TParams() []*TypeName { return t.expand().tparams }
func (t *Named) TParams() []*TypeName {
return t.load().tparams
}
// SetTParams sets the type parameters of the named type t.
func (t *Named) SetTParams(tparams []*TypeName) { t.expand().tparams = tparams }
func (t *Named) SetTParams(tparams []*TypeName) { t.load().tparams = tparams }
// TArgs returns the type arguments after instantiation of the named type t, or nil if not instantiated.
func (t *Named) TArgs() []Type { return t.targs }
@ -116,10 +131,10 @@ func (t *Named) TArgs() []Type { return t.targs }
func (t *Named) SetTArgs(args []Type) { t.targs = args }
// NumMethods returns the number of explicit methods whose receiver is named type t.
func (t *Named) NumMethods() int { return len(t.expand().methods) }
func (t *Named) NumMethods() int { return len(t.load().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.expand().methods[i] }
func (t *Named) Method(i int) *Func { return t.load().methods[i] }
// SetUnderlying sets the underlying type and marks t as complete.
func (t *Named) SetUnderlying(underlying Type) {
@ -129,18 +144,18 @@ func (t *Named) SetUnderlying(underlying Type) {
if _, ok := underlying.(*Named); ok {
panic("types2.Named.SetUnderlying: underlying type must not be *Named")
}
t.expand().underlying = underlying
t.load().underlying = underlying
}
// AddMethod adds method m unless it is already in the method list.
func (t *Named) AddMethod(m *Func) {
t.expand()
t.load()
if i, _ := lookupMethod(t.methods, m.pkg, m.name); i < 0 {
t.methods = append(t.methods, m)
}
}
func (t *Named) Underlying() Type { return t.expand().underlying }
func (t *Named) Underlying() Type { return t.load().underlying }
func (t *Named) String() string { return TypeString(t, nil) }
// ----------------------------------------------------------------------------
@ -153,6 +168,8 @@ func (t *Named) String() string { return TypeString(t, nil) }
// is detected, the result is Typ[Invalid]. If a cycle is detected and
// n0.check != nil, the cycle is reported.
func (n0 *Named) under() Type {
n0.expand()
u := n0.Underlying()
if u == Typ[Invalid] {
@ -168,7 +185,7 @@ func (n0 *Named) under() Type {
default:
// common case
return u
case *Named, *instance:
case *Named:
// handled below
}
@ -199,12 +216,8 @@ func (n0 *Named) under() Type {
var n1 *Named
switch u1 := u.(type) {
case *Named:
u1.expand()
n1 = u1
case *instance:
n1, _ = u1.expand().(*Named)
if n1 == nil {
u = Typ[Invalid]
}
}
if n1 == nil {
break // end of chain

3
src/cmd/compile/internal/types2/object.go
View file

@ -475,6 +475,9 @@ func writeObject(buf *bytes.Buffer, obj Object, qf Qualifier) {
if _, ok := typ.(*Basic); ok {
return
}
if named, _ := typ.(*Named); named != nil && len(named.tparams) > 0 {
writeTParamList(buf, named.tparams, qf, nil)
}
if tname.IsAlias() {
buf.WriteString(" =")
} else {

8
src/cmd/compile/internal/types2/predicates.go
View file

@ -10,7 +10,7 @@ package types2
// isNamed may be called with types that are not fully set up.
func isNamed(typ Type) bool {
switch typ.(type) {
case *Basic, *Named, *TypeParam, *instance:
case *Basic, *Named, *TypeParam:
return true
}
return false
@ -21,7 +21,7 @@ func isNamed(typ Type) bool {
func isGeneric(typ Type) bool {
// A parameterized type is only instantiated if it doesn't have an instantiation already.
named, _ := typ.(*Named)
return named != nil && named.obj != nil && named.TParams() != nil && named.targs == nil
return named != nil && named.obj != nil && named.targs == nil && named.TParams() != nil
}
func is(typ Type, what BasicInfo) bool {
@ -144,8 +144,8 @@ func (p *ifacePair) identical(q *ifacePair) bool {
// For changes to this code the corresponding changes should be made to unifier.nify.
func identical(x, y Type, cmpTags bool, p *ifacePair) bool {
// types must be expanded for comparison
x = expandf(x)
y = expandf(y)
x = expand(x)
y = expand(y)
if x == y {
return true

205
src/cmd/compile/internal/types2/sanitize.go
View file

@ -1,205 +0,0 @@
// Copyright 2020 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
// sanitizeInfo walks the types contained in info to ensure that all instances
// are expanded.
//
// This includes some objects that may be shared across concurrent
// type-checking passes (such as those in the universe scope), so we are
// careful here not to write types that are already sanitized. This avoids a
// data race as any shared types should already be sanitized.
func sanitizeInfo(info *Info) {
var s sanitizer = make(map[Type]Type)
// Note: Some map entries are not references.
// If modified, they must be assigned back.
for e, tv := range info.Types {
if typ := s.typ(tv.Type); typ != tv.Type {
tv.Type = typ
info.Types[e] = tv
}
}
for e, inf := range info.Inferred {
changed := false
for i, targ := range inf.TArgs {
if typ := s.typ(targ); typ != targ {
inf.TArgs[i] = typ
changed = true
}
}
if typ := s.typ(inf.Sig); typ != inf.Sig {
inf.Sig = typ.(*Signature)
changed = true
}
if changed {
info.Inferred[e] = inf
}
}
for _, obj := range info.Defs {
if obj != nil {
if typ := s.typ(obj.Type()); typ != obj.Type() {
obj.setType(typ)
}
}
}
for _, obj := range info.Uses {
if obj != nil {
if typ := s.typ(obj.Type()); typ != obj.Type() {
obj.setType(typ)
}
}
}
// TODO(gri) sanitize as needed
// - info.Implicits
// - info.Selections
// - info.Scopes
// - info.InitOrder
}
type sanitizer map[Type]Type
func (s sanitizer) typ(typ Type) Type {
if typ == nil {
return nil
}
if t, found := s[typ]; found {
return t
}
s[typ] = typ
switch t := typ.(type) {
case *Basic, *top:
// nothing to do
case *Array:
if elem := s.typ(t.elem); elem != t.elem {
t.elem = elem
}
case *Slice:
if elem := s.typ(t.elem); elem != t.elem {
t.elem = elem
}
case *Struct:
s.varList(t.fields)
case *Pointer:
if base := s.typ(t.base); base != t.base {
t.base = base
}
case *Tuple:
s.tuple(t)
case *Signature:
s.var_(t.recv)
s.tuple(t.params)
s.tuple(t.results)
case *Union:
s.typeList(t.types)
case *Interface:
s.funcList(t.methods)
s.typeList(t.embeddeds)
// TODO(gri) do we need to sanitize type sets?
tset := t.typeSet()
s.funcList(tset.methods)
if types := s.typ(tset.types); types != tset.types {
tset.types = types
}
case *Map:
if key := s.typ(t.key); key != t.key {
t.key = key
}
if elem := s.typ(t.elem); elem != t.elem {
t.elem = elem
}
case *Chan:
if elem := s.typ(t.elem); elem != t.elem {
t.elem = elem
}
case *Named:
if debug && t.check != nil {
panic("internal error: Named.check != nil")
}
t.expand()
if orig := s.typ(t.fromRHS); orig != t.fromRHS {
t.fromRHS = orig
}
if under := s.typ(t.underlying); under != t.underlying {
t.underlying = under
}
s.typeList(t.targs)
s.funcList(t.methods)
case *TypeParam:
if bound := s.typ(t.bound); bound != t.bound {
t.bound = bound
}
case *instance:
typ = t.expand()
s[t] = typ
default:
unimplemented()
}
return typ
}
func (s sanitizer) var_(v *Var) {
if v != nil {
if typ := s.typ(v.typ); typ != v.typ {
v.typ = typ
}
}
}
func (s sanitizer) varList(list []*Var) {
for _, v := range list {
s.var_(v)
}
}
func (s sanitizer) tuple(t *Tuple) {
if t != nil {
s.varList(t.vars)
}
}
func (s sanitizer) func_(f *Func) {
if f != nil {
if typ := s.typ(f.typ); typ != f.typ {
f.typ = typ
}
}
}
func (s sanitizer) funcList(list []*Func) {
for _, f := range list {
s.func_(f)
}
}
func (s sanitizer) typeList(list []Type) {
for i, t := range list {
if typ := s.typ(t); typ != t {
list[i] = typ
}
}
}

3
src/cmd/compile/internal/types2/sizeof_test.go
View file

@ -31,9 +31,8 @@ func TestSizeof(t *testing.T) {
{Interface{}, 40, 80},
{Map{}, 16, 32},
{Chan{}, 12, 24},
{Named{}, 84, 160},
{Named{}, 88, 168},
{TypeParam{}, 28, 48},
{instance{}, 56, 104},
{top{}, 0, 0},
// Objects

15
src/cmd/compile/internal/types2/subst.go
View file

@ -26,12 +26,7 @@ func makeSubstMap(tpars []*TypeName, targs []Type) *substMap {
assert(len(tpars) == len(targs))
proj := make(map[*TypeParam]Type, len(tpars))
for i, tpar := range tpars {
// We must expand type arguments otherwise *instance
// types end up as components in composite types.
// TODO(gri) explain why this causes problems, if it does
targ := expand(targs[i]) // possibly nil
targs[i] = targ
proj[tpar.typ.(*TypeParam)] = targ
proj[tpar.typ.(*TypeParam)] = targs[i]
}
return &substMap{targs, proj}
}
@ -83,6 +78,7 @@ func (check *Checker) subst(pos syntax.Pos, typ Type, smap *substMap) Type {
// for recursive types (example: type T[P any] *T[P]).
subst.typMap = make(map[string]*Named)
}
return subst.typ(typ)
}
@ -241,10 +237,13 @@ func (subst *subster) typ(typ Type) Type {
named := subst.check.newNamed(tname, t, t.Underlying(), t.TParams(), t.methods) // method signatures are updated lazily
named.targs = new_targs
subst.typMap[h] = named
t.expand() // must happen after typMap update to avoid infinite recursion
// do the substitution
dump(">>> subst %s with %s (new: %s)", t.underlying, subst.smap, new_targs)
named.underlying = subst.typOrNil(t.Underlying())
dump(">>> underlying: %v", named.underlying)
assert(named.underlying != nil)
named.fromRHS = named.underlying // for cycle detection (Checker.validType)
return named
@ -252,10 +251,6 @@ func (subst *subster) typ(typ Type) Type {
case *TypeParam:
return subst.smap.lookup(t)
case *instance:
// TODO(gri) can we avoid the expansion here and just substitute the type parameters?
return subst.typ(t.expand())
default:
unimplemented()
}

4
src/cmd/compile/internal/types2/testdata/check/issues.go2 vendored
View file

@ -74,8 +74,10 @@ func (u T2[U]) Add1() U {
return u.s + 1
}
// TODO(rfindley): we should probably report an error here as well, not
// just when the type is first instantiated.
func NewT2[U any]() T2[U /* ERROR U has no constraints */ ] {
return T2[U /* ERROR U has no constraints */ ]{}
return T2[U]{}
}
func _() {

3
src/cmd/compile/internal/types2/typeparam.go
View file

@ -21,7 +21,8 @@ type TypeParam struct {
id uint64 // unique id, for debugging only
obj *TypeName // corresponding type name
index int // type parameter index in source order, starting at 0
bound Type // *Named or *Interface; underlying type is always *Interface
// TODO(rfindley): this could also be Typ[Invalid]. Verify that this is handled correctly.
bound Type // *Named or *Interface; underlying type is always *Interface
}
// Obj returns the type name for the type parameter t.

10
src/cmd/compile/internal/types2/typestring.go
View file

@ -269,6 +269,9 @@ func writeType(buf *bytes.Buffer, typ Type, qf Qualifier, visited []Type) {
}
case *Named:
if t.instance != nil {
buf.WriteByte(instanceMarker)
}
writeTypeName(buf, t.obj, qf)
if t.targs != nil {
// instantiated type
@ -294,13 +297,6 @@ func writeType(buf *bytes.Buffer, typ Type, qf Qualifier, visited []Type) {
}
buf.WriteString(s + subscript(t.id))
case *instance:
buf.WriteByte(instanceMarker) // indicate "non-evaluated" syntactic instance
writeTypeName(buf, t.base.obj, qf)
buf.WriteByte('[')
writeTypeList(buf, t.targs, qf, visited)
buf.WriteByte(']')
case *top:
buf.WriteString("⊤")

2
src/cmd/compile/internal/types2/typexpr.go
View file

@ -446,7 +446,7 @@ func (check *Checker) instantiatedType(x syntax.Expr, targsx []syntax.Expr, def
// make sure we check instantiation works at least once
// and that the resulting type is valid
check.later(func() {
t := typ.(*instance).expand()
t := expand(typ)
check.validType(t, nil)
})