[dev.typeparams] go/types: more consistent handling of predeclared "any"

This is a port of CL 334911 to go/types.

Change-Id: I2cafdc76cb4d06ba82188c530f35952c1f77d292
Reviewed-on: https://go-review.googlesource.com/c/go/+/335569
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>

diff --git a/src/go/types/decl.go b/src/go/types/decl.go
index 8fae59ffe81e3cf78d29921a34f48a3a8185001c..e38124f077abd0307718e48012bd2344007e2c60 100644 (file)
--- a/src/go/types/decl.go
+++ b/src/go/types/decl.go
@@ -678,8 +678,9 @@ func (check *Checker) declareTypeParams(tparams []*TypeName, names []*ast.Ident)
 // The type must be an interface, including the predeclared type "any".
 func (check *Checker) boundType(e ast.Expr) Type {
        // The predeclared identifier "any" is visible only as a type bound in a type parameter list.
-       if name, _ := unparen(e).(*ast.Ident); name != nil && name.Name == "any" && check.lookup("any") == nil {
-               return universeAny
+       // If we allow "any" for general use, this if-statement can be removed (issue #33232).
+       if name, _ := unparen(e).(*ast.Ident); name != nil && name.Name == "any" && check.lookup("any") == universeAny {
+               return universeAny.Type()
        }
 
        bound := check.typ(e)

diff --git a/src/go/types/object_test.go b/src/go/types/object_test.go
index 2b6057bd934bca19cfa0f40062d6b8bb63fdd744..0ff8fdd6fa69bad43ca3a603d6f3d7fe6770d89a 100644 (file)
--- a/src/go/types/object_test.go
+++ b/src/go/types/object_test.go
@@ -22,7 +22,7 @@ func TestIsAlias(t *testing.T) {
        check(Unsafe.Scope().Lookup("Pointer").(*TypeName), false)
        for _, name := range Universe.Names() {
                if obj, _ := Universe.Lookup(name).(*TypeName); obj != nil {
-                       check(obj, name == "byte" || name == "rune")
+                       check(obj, name == "any" || name == "byte" || name == "rune")
                }
        }
 

diff --git a/src/go/types/testdata/check/typeparams.go2 b/src/go/types/testdata/check/typeparams.go2
index 0e3795724b3a00f6aba5c2a33d1ffab17111b94b..b03725ff2aa0b2bcb0bf5e4d4f27443c359bc524 100644 (file)
--- a/src/go/types/testdata/check/typeparams.go2
+++ b/src/go/types/testdata/check/typeparams.go2
@@ -6,11 +6,11 @@ package p
 
 // import "io" // for type assertion tests
 
-// The predeclared identifier "any" is only visible as a constraint
+// The predeclared identifier "any" can only be used as a constraint
 // in a type parameter list.
-var _ any // ERROR undeclared
-func _[_ any /* ok here */ , _ interface{any /* ERROR undeclared */ }](any /* ERROR undeclared */ ) {
-        var _ any /* ERROR undeclared */
+var _ any // ERROR cannot use any outside constraint position
+func _[_ any /* ok here */ , _ interface{any /* ERROR constraint */ }](any /* ERROR constraint */ ) {
+        var _ any /* ERROR constraint */
 }
 
 func identity[T any](x T) T { return x }

diff --git a/src/go/types/typexpr.go b/src/go/types/typexpr.go
index 9a9fe32cb38d276ff769e130108ca2f1710d119c..f2c4762a6b30fc967b9235cc8259956a5b148a48 100644 (file)
--- a/src/go/types/typexpr.go
+++ b/src/go/types/typexpr.go
@@ -27,13 +27,24 @@ func (check *Checker) ident(x *operand, e *ast.Ident, def *Named, wantType bool)
        // Note that we cannot use check.lookup here because the returned scope
        // may be different from obj.Parent(). See also Scope.LookupParent doc.
        scope, obj := check.scope.LookupParent(e.Name, check.pos)
-       if obj == nil || obj == universeComparable && !check.allowVersion(check.pkg, 1, 18) {
+       switch obj {
+       case nil:
                if e.Name == "_" {
-                       check.errorf(e, _InvalidBlank, "cannot use _ as value or type")
+                       check.error(e, _InvalidBlank, "cannot use _ as value or type")
                } else {
                        check.errorf(e, _UndeclaredName, "undeclared name: %s", e.Name)
                }
                return
+       case universeAny, universeComparable:
+               if !check.allowVersion(check.pkg, 1, 18) {
+                       check.errorf(e, _UndeclaredName, "undeclared name: %s (requires version go1.18 or later)", e.Name)
+                       return
+               }
+               // If we allow "any" for general use, this if-statement can be removed (issue #33232).
+               if obj == universeAny {
+                       check.error(e, _Todo, "cannot use any outside constraint position")
+                       return
+               }
        }
        check.recordUse(e, obj)
 

diff --git a/src/go/types/universe.go b/src/go/types/universe.go
index 7c1e29b856cf5801a241caf5f3dcc36a3416f3b6..59952bc64270afc8c38855f7bf739def49a7b726 100644 (file)
--- a/src/go/types/universe.go
+++ b/src/go/types/universe.go
@@ -21,11 +21,11 @@ var Universe *Scope
 var Unsafe *Package
 
 var (
-       universeIota       *Const
-       universeByte       *Basic // uint8 alias, but has name "byte"
-       universeRune       *Basic // int32 alias, but has name "rune"
-       universeAny        *Interface
-       universeError      *Named
+       universeIota       Object
+       universeByte       Type // uint8 alias, but has name "byte"
+       universeRune       Type // int32 alias, but has name "rune"
+       universeAny        Object
+       universeError      Type
        universeComparable Object
 )
 
@@ -80,9 +80,6 @@ func defPredeclaredTypes() {
        }
 
        // type any = interface{}
-       // Entered into universe scope so we do all the usual checks;
-       // but removed again from scope later since it's only visible
-       // as constraint in a type parameter list.
        def(NewTypeName(token.NoPos, nil, "any", &emptyInterface))
 
        // type error interface{ Error() string }
@@ -225,15 +222,12 @@ func init() {
        defPredeclaredNil()
        defPredeclaredFuncs()
 
-       universeIota = Universe.Lookup("iota").(*Const)
-       universeByte = Universe.Lookup("byte").(*TypeName).typ.(*Basic)
-       universeRune = Universe.Lookup("rune").(*TypeName).typ.(*Basic)
-       universeAny = Universe.Lookup("any").(*TypeName).typ.(*Interface)
-       universeError = Universe.Lookup("error").(*TypeName).typ.(*Named)
+       universeIota = Universe.Lookup("iota")
+       universeByte = Universe.Lookup("byte").Type()
+       universeRune = Universe.Lookup("rune").Type()
+       universeAny = Universe.Lookup("any")
+       universeError = Universe.Lookup("error").Type()
        universeComparable = Universe.Lookup("comparable")
-
-       // "any" is only visible as constraint in a type parameter list
-       delete(Universe.elems, "any")
 }
 
 // Objects with names containing blanks are internal and not entered into