cmd/compile: remove support for old comparable semantics

Change-Id: I730da5082ea6de1510482aabaa2915e83d3819a5
Reviewed-on: https://go-review.googlesource.com/c/go/+/461607
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Griesemer <gri@google.com>

Author: griesemer

src/cmd/compile/internal/base/flag.go

@@ -122,8 +122,7 @@ type CmdFlags struct {
 	SymABIs            string       "help:\"read symbol ABIs from `file`\""
 	TraceProfile       string       "help:\"write an execution trace to `file`\""
 	TrimPath           string       "help:\"remove `prefix` from recorded source file paths\""
-	WB                 bool         "help:\"enable write barrier\""            // TODO: remove
-	OldComparable      bool         "help:\"enable old comparable semantics\"" // TODO: remove for Go 1.21
+	WB                 bool         "help:\"enable write barrier\"" // TODO: remove
 	PgoProfile         string       "help:\"read profile from `file`\""
 
 	// Configuration derived from flags; not a flag itself.

src/cmd/compile/internal/noder/irgen.go

@@ -55,9 +55,8 @@ func checkFiles(noders []*noder) (posMap, *types2.Package, *types2.Info) {
 			}
 			base.ErrorfAt(m.makeXPos(terr.Pos), "%s", msg)
 		},
-		Importer:               &importer,
-		Sizes:                  &gcSizes{},
-		OldComparableSemantics: base.Flag.OldComparable, // default is new comparable semantics
+		Importer: &importer,
+		Sizes:    &gcSizes{},
 	}
 	info := &types2.Info{
 		StoreTypesInSyntax: true,

src/cmd/compile/internal/types2/api.go

@@ -167,11 +167,6 @@ type Config struct {
 	// If DisableUnusedImportCheck is set, packages are not checked
 	// for unused imports.
 	DisableUnusedImportCheck bool
-
-	// If OldComparableSemantics is set, ordinary (non-type parameter)
-	// interfaces do not satisfy the comparable constraint.
-	// TODO(gri) remove this flag for Go 1.21
-	OldComparableSemantics bool
 }
 
 func srcimporter_setUsesCgo(conf *Config) {

src/cmd/compile/internal/types2/check_test.go

@@ -126,7 +126,6 @@ func testFiles(t *testing.T, filenames []string, colDelta uint, manual bool) {
 	flags := flag.NewFlagSet("", flag.PanicOnError)
 	flags.StringVar(&conf.GoVersion, "lang", "", "")
 	flags.BoolVar(&conf.FakeImportC, "fakeImportC", false, "")
-	flags.BoolVar(&conf.OldComparableSemantics, "oldComparableSemantics", false, "")
 	if err := parseFlags(filenames[0], nil, flags); err != nil {
 		t.Fatal(err)
 	}

src/cmd/compile/internal/types2/instantiate.go

@@ -258,15 +258,6 @@ func (check *Checker) implements(V, T Type, constraint bool, cause *string) bool
 		if comparable(V, false /* strict comparability */, nil, nil) {
 			return true
 		}
-		// If check.conf.OldComparableSemantics is set (by the compiler or
-		// a test), we only consider strict comparability and we're done.
-		// TODO(gri) remove this check for Go 1.21
-		if check != nil && check.conf.OldComparableSemantics {
-			if cause != nil {
-				*cause = check.sprintf("%s does not %s comparable", V, verb)
-			}
-			return false
-		}
 		// For constraint satisfaction, use dynamic (spec) comparability
 		// so that ordinary, non-type parameter interfaces implement comparable.
 		if constraint && comparable(V, true /* spec comparability */, nil, nil) {

src/go/types/api.go

@@ -170,11 +170,6 @@ type Config struct {
 	// If DisableUnusedImportCheck is set, packages are not checked
 	// for unused imports.
 	DisableUnusedImportCheck bool
-
-	// If oldComparableSemantics is set, ordinary (non-type parameter)
-	// interfaces do not satisfy the comparable constraint.
-	// TODO(gri) remove this flag for Go 1.21
-	oldComparableSemantics bool
 }
 
 func srcimporter_setUsesCgo(conf *Config) {

src/go/types/check_test.go

@@ -138,7 +138,6 @@ func testFiles(t *testing.T, sizes Sizes, filenames []string, srcs [][]byte, man
 	flags := flag.NewFlagSet("", flag.PanicOnError)
 	flags.StringVar(&conf.GoVersion, "lang", "", "")
 	flags.BoolVar(&conf.FakeImportC, "fakeImportC", false, "")
-	flags.BoolVar(boolFieldAddr(&conf, "oldComparableSemantics"), "oldComparableSemantics", false, "")
 	if err := parseFlags(filenames[0], srcs[0], flags); err != nil {
 		t.Fatal(err)
 	}

src/go/types/instantiate.go

@@ -258,15 +258,6 @@ func (check *Checker) implements(V, T Type, constraint bool, cause *string) bool
 		if comparable(V, false /* strict comparability */, nil, nil) {
 			return true
 		}
-		// If check.conf.OldComparableSemantics is set (by the compiler or
-		// a test), we only consider strict comparability and we're done.
-		// TODO(gri) remove this check for Go 1.21
-		if check != nil && check.conf.oldComparableSemantics {
-			if cause != nil {
-				*cause = check.sprintf("%s does not %s comparable", V, verb)
-			}
-			return false
-		}
 		// For constraint satisfaction, use dynamic (spec) comparability
 		// so that ordinary, non-type parameter interfaces implement comparable.
 		if constraint && comparable(V, true /* spec comparability */, nil, nil) {

src/internal/types/testdata/check/issues1.go

@@ -1,5 +1,3 @@
-// -oldComparableSemantics
-
 // 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.
@@ -22,7 +20,7 @@ func _[X comparable, Y interface{comparable; m()}]() {
 	eql(x, x)
 	eql(y, y)
 	eql(y, nil /* ERROR "cannot use nil as Y value in argument to eql" */ )
-	eql[io /* ERROR "does not satisfy comparable" */ .Reader](nil, nil)
+	eql[io.Reader](nil, nil)
 }
 
 // If we have a receiver of pointer to type parameter type (below: *T)

src/internal/types/testdata/fixedbugs/issue50646.go

@@ -1,5 +1,3 @@
-// -oldComparableSemantics
-
 // Copyright 2022 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.
@@ -13,15 +11,15 @@ type T interface{ m() }
 
 func _[P comparable, Q ~int, R any]() {
 	_ = f1[int]
-	_ = f1[T /* ERROR "T does not satisfy comparable" */ ]
-	_ = f1[any /* ERROR "any does not satisfy comparable" */ ]
+	_ = f1[T]
+	_ = f1[any]
 	_ = f1[P]
 	_ = f1[Q]
 	_ = f1[R /* ERROR "R does not satisfy comparable" */]
 
 	_ = f2[int]
-	_ = f2[T /* ERROR "T does not satisfy comparable" */ ]
-	_ = f2[any /* ERROR "any does not satisfy comparable" */ ]
+	_ = f2[T]
+	_ = f2[any]
 	_ = f2[P]
 	_ = f2[Q]
 	_ = f2[R /* ERROR "R does not satisfy comparable" */]

src/internal/types/testdata/fixedbugs/issue51257.go

@@ -1,5 +1,3 @@
-// -oldComparableSemantics
-
 // Copyright 2022 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.
@@ -14,8 +12,8 @@ type S3 struct{ x [10]interface{ m() } }
 
 func _[P1 comparable, P2 S2]() {
 	_ = f[S1]
-	_ = f[S2 /* ERROR "S2 does not satisfy comparable" */ ]
-	_ = f[S3 /* ERROR "S3 does not satisfy comparable" */ ]
+	_ = f[S2]
+	_ = f[S3]
 
 	type L1 struct { x P1 }
 	type L2 struct { x P2 }
@@ -41,7 +39,7 @@ func NewSetFromSlice[T comparable](items []T) *Set[T] {
 type T struct{ x any }
 
 func main() {
-	NewSetFromSlice /* ERROR "T does not satisfy comparable" */ ([]T{
+	NewSetFromSlice([]T{
 		{"foo"},
 		{5},
 	})