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[dev.typeparams] cmd/compile/internal/types2: "comparable" must not be visible before Go 1.18
While at it, clean up the setup of comparable in universe.go. Fixes #46090 Change-Id: I9655b3e137a03763d677d9a2a730c5570ccff6dc Reviewed-on: https://go-review.googlesource.com/c/go/+/331517 Trust: Robert Griesemer <gri@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>
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src/cmd/compile/internal/types2/testdata/fixedbugs/issue46090.go2
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src/cmd/compile/internal/types2/testdata/fixedbugs/issue46090.go2
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@ -0,0 +1,9 @@
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// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// The predeclared type comparable is not visible before Go 1.18.
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package go1_17
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type _ comparable // ERROR undeclared
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@ -25,7 +25,7 @@ func (check *Checker) ident(x *operand, e *syntax.Name, def *Named, wantType boo
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// Note that we cannot use check.lookup here because the returned scope
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// may be different from obj.Parent(). See also Scope.LookupParent doc.
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scope, obj := check.scope.LookupParent(e.Value, check.pos)
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if obj == nil {
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if obj == nil || obj == universeComparable && !check.allowVersion(check.pkg, 1, 18) {
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if e.Value == "_" {
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check.error(e, "cannot use _ as value or type")
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} else {
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@ -20,11 +20,12 @@ var Universe *Scope
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var Unsafe *Package
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var (
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universeIota *Const
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universeByte *Basic // uint8 alias, but has name "byte"
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universeRune *Basic // int32 alias, but has name "rune"
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universeAny *Interface
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universeError *Named
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universeIota *Const
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universeByte *Basic // uint8 alias, but has name "byte"
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universeRune *Basic // int32 alias, but has name "rune"
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universeAny *Interface
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universeError *Named
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universeComparable Object
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)
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// Typ contains the predeclared *Basic types indexed by their
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@ -77,21 +78,30 @@ func defPredeclaredTypes() {
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def(NewTypeName(nopos, nil, t.name, t))
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}
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// any
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// (Predeclared and entered into universe scope so we do all the
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// usual checks; but removed again from scope later since it's
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// only visible as constraint in a type parameter list.)
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// type any = interface{}
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// Entered into universe scope so we do all the usual checks;
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// but removed again from scope later since it's only visible
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// as constraint in a type parameter list.
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def(NewTypeName(nopos, nil, "any", &emptyInterface))
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// Error has a nil package in its qualified name since it is in no package
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// type error interface{ Error() string }
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{
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res := NewVar(nopos, nil, "", Typ[String])
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sig := &Signature{results: NewTuple(res)}
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sig := NewSignature(nil, nil, NewTuple(res), false)
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err := NewFunc(nopos, nil, "Error", sig)
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typ := &Named{underlying: NewInterfaceType([]*Func{err}, nil)}
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sig.recv = NewVar(nopos, nil, "", typ)
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def(NewTypeName(nopos, nil, "error", typ))
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}
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// type comparable interface{ ==() }
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{
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sig := NewSignature(nil, nil, nil, false)
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eql := NewFunc(nopos, nil, "==", sig)
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typ := &Named{underlying: NewInterfaceType([]*Func{eql}, nil)}
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sig.recv = NewVar(nopos, nil, "", typ)
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def(NewTypeName(nopos, nil, "comparable", typ))
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}
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}
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var predeclaredConsts = [...]struct {
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@ -200,33 +210,6 @@ func DefPredeclaredTestFuncs() {
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def(newBuiltin(_Trace))
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}
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func defPredeclaredComparable() {
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// The "comparable" interface can be imagined as defined like
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//
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// type comparable interface {
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// == () untyped bool
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// != () untyped bool
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// }
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//
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// == and != cannot be user-declared but we can declare
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// a magic method == and check for its presence when needed.
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// Define interface { == () }. We don't care about the signature
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// for == so leave it empty except for the receiver, which is
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// set up later to match the usual interface method assumptions.
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sig := new(Signature)
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eql := NewFunc(nopos, nil, "==", sig)
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iface := NewInterfaceType([]*Func{eql}, nil)
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// set up the defined type for the interface
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obj := NewTypeName(nopos, nil, "comparable", nil)
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named := NewNamed(obj, iface, nil)
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obj.color_ = black
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sig.recv = NewVar(nopos, nil, "", named) // complete == signature
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def(obj)
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}
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func init() {
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Universe = NewScope(nil, nopos, nopos, "universe")
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Unsafe = NewPackage("unsafe", "unsafe")
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@ -236,13 +219,13 @@ func init() {
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defPredeclaredConsts()
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defPredeclaredNil()
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defPredeclaredFuncs()
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defPredeclaredComparable()
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universeIota = Universe.Lookup("iota").(*Const)
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universeByte = Universe.Lookup("byte").(*TypeName).typ.(*Basic)
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universeRune = Universe.Lookup("rune").(*TypeName).typ.(*Basic)
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universeAny = Universe.Lookup("any").(*TypeName).typ.(*Interface)
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universeError = Universe.Lookup("error").(*TypeName).typ.(*Named)
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universeComparable = Universe.Lookup("comparable")
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// "any" is only visible as constraint in a type parameter list
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delete(Universe.elems, "any")
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