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[dev.typeparams] cmd/compile/internal/types2: more consistent handling of predeclared "any"
Rather than removing "any" from the universe scope, keep it predeclared but provide a better error message. While at it, remove some unnecessary type assertions. Change-Id: I10603274282ea6afc107f703ab194f32bd334dd1 Reviewed-on: https://go-review.googlesource.com/c/go/+/334911 Trust: Robert Griesemer <gri@golang.org> Run-TryBot: Robert Griesemer <gri@golang.org> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>
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@ -617,8 +617,9 @@ func (check *Checker) declareTypeParam(index int, name *syntax.Name) *TypeName {
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// The type must be an interface, including the predeclared type "any".
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func (check *Checker) boundType(e syntax.Expr) Type {
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// The predeclared identifier "any" is visible only as a type bound in a type parameter list.
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if name, _ := unparen(e).(*syntax.Name); name != nil && name.Value == "any" && check.lookup("any") == nil {
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return universeAny
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// If we allow "any" for general use, this if-statement can be removed (issue #33232).
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if name, _ := unparen(e).(*syntax.Name); name != nil && name.Value == "any" && check.lookup("any") == universeAny {
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return universeAny.Type()
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}
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bound := check.typ(e)
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@ -25,7 +25,7 @@ func TestIsAlias(t *testing.T) {
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check(Unsafe.Scope().Lookup("Pointer").(*TypeName), false)
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for _, name := range Universe.Names() {
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if obj, _ := Universe.Lookup(name).(*TypeName); obj != nil {
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check(obj, name == "byte" || name == "rune")
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check(obj, name == "any" || name == "byte" || name == "rune")
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}
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}
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@ -6,11 +6,11 @@ package p
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// import "io" // for type assertion tests
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// The predeclared identifier "any" is only visible as a constraint
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// The predeclared identifier "any" can only be used as a constraint
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// in a type parameter list.
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var _ any // ERROR undeclared
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func _[_ any /* ok here */ , _ interface{any /* ERROR undeclared */ }](any /* ERROR undeclared */ ) {
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var _ any /* ERROR undeclared */
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var _ any // ERROR cannot use any outside constraint position
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func _[_ any /* ok here */ , _ interface{any /* ERROR constraint */ }](any /* ERROR constraint */ ) {
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var _ any /* ERROR constraint */
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}
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func identity[T any](x T) T { return x }
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@ -25,7 +25,8 @@ 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 || obj == universeComparable && !check.allowVersion(check.pkg, 1, 18) {
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switch obj {
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case nil:
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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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@ -36,6 +37,16 @@ func (check *Checker) ident(x *operand, e *syntax.Name, def *Named, wantType boo
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}
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}
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return
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case universeAny, universeComparable:
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if !check.allowVersion(check.pkg, 1, 18) {
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check.errorf(e, "undeclared name: %s (requires version go1.18 or later)", e.Value)
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return
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}
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// If we allow "any" for general use, this if-statement can be removed (issue #33232).
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if obj == universeAny {
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check.error(e, "cannot use any outside constraint position")
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return
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}
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}
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check.recordUse(e, obj)
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@ -20,11 +20,11 @@ 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 Object
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universeByte Type // uint8 alias, but has name "byte"
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universeRune Type // int32 alias, but has name "rune"
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universeAny Object
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universeError Type
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universeComparable Object
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)
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@ -79,9 +79,6 @@ func defPredeclaredTypes() {
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}
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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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// type error interface{ Error() string }
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@ -224,15 +221,12 @@ func init() {
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defPredeclaredNil()
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defPredeclaredFuncs()
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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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universeIota = Universe.Lookup("iota")
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universeByte = Universe.Lookup("byte").Type()
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universeRune = Universe.Lookup("rune").Type()
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universeAny = Universe.Lookup("any")
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universeError = Universe.Lookup("error").Type()
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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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}
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// Objects with names containing blanks are internal and not entered into
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@ -6,4 +6,4 @@
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package p
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var x any // ERROR "undefined: any|undefined type .*any.*"
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var x any // ERROR "undefined: any|undefined type .*any.*|cannot use any outside constraint position"
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@ -10,8 +10,8 @@ package tparam1
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// The predeclared identifier "any" is only visible as a constraint
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// in a type parameter list.
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var _ any // ERROR "undefined"
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func _(_ any) // ERROR "undefined"
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var _ any // ERROR "cannot use any outside constraint position"
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func _(_ any) // ERROR "cannot use any outside constraint position"
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type _[_ any /* ok here */ ] struct{}
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const N = 10
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