From: Robert Griesemer <gri@golang.org>
Date: Tue, 5 Oct 2021 21:03:47 +0000 (-0700)
Subject: cmd/compile/internal/syntax, types2: remove ability to handle type lists
X-Git-Tag: go1.18beta1~1016
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=f05c67f18259800e4847e44c9ca34de2bf5ed198;p=gostls13.git

cmd/compile/internal/syntax, types2: remove ability to handle type lists

The type set notation has been accepted a while ago.
We're not going back to supporting the original
type list notation. Remove support for it in the
parser and type checker.

Change-Id: I860651f80b89fa43a3a5a2a02cf823ec0dae583c
Reviewed-on: https://go-review.googlesource.com/c/go/+/354131
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
---

diff --git a/src/cmd/compile/internal/syntax/error_test.go b/src/cmd/compile/internal/syntax/error_test.go
index 966b36f6bc..0ab3c20ce5 100644
--- a/src/cmd/compile/internal/syntax/error_test.go
+++ b/src/cmd/compile/internal/syntax/error_test.go
@@ -130,7 +130,7 @@ func testSyntaxErrors(t *testing.T, filename string) {
 
 	var mode Mode
 	if strings.HasSuffix(filename, ".go2") {
-		mode = AllowGenerics | AllowTypeSets | AllowTypeLists
+		mode = AllowGenerics | AllowTypeSets
 	}
 	ParseFile(filename, func(err error) {
 		e, ok := err.(Error)
diff --git a/src/cmd/compile/internal/syntax/nodes.go b/src/cmd/compile/internal/syntax/nodes.go
index fb9786daa3..2f9b43edef 100644
--- a/src/cmd/compile/internal/syntax/nodes.go
+++ b/src/cmd/compile/internal/syntax/nodes.go
@@ -275,14 +275,14 @@ type (
 	// Name Type
 	//      Type
 	Field struct {
-		Name *Name // nil means anonymous field/parameter (structs/parameters), or embedded interface (interfaces)
+		Name *Name // nil means anonymous field/parameter (structs/parameters), or embedded element (interfaces)
 		Type Expr  // field names declared in a list share the same Type (identical pointers)
 		node
 	}
 
 	// interface { MethodList[0]; MethodList[1]; ... }
 	InterfaceType struct {
-		MethodList []*Field // a field named "type" means a type constraint
+		MethodList []*Field
 		expr
 	}
 
diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go
index 54e77b9958..a669c54712 100644
--- a/src/cmd/compile/internal/syntax/parser.go
+++ b/src/cmd/compile/internal/syntax/parser.go
@@ -1450,30 +1450,6 @@ func (p *parser) interfaceType() *InterfaceType {
 				return false
 			}
 
-		case _Type:
-			// TODO(gri) remove TypeList syntax if we accept #45346
-			if p.allowGenerics() && p.mode&AllowTypeLists != 0 {
-				type_ := NewName(p.pos(), "type") // cannot have a method named "type"
-				p.next()
-				if p.tok != _Semi && p.tok != _Rbrace {
-					f := new(Field)
-					f.pos = p.pos()
-					f.Name = type_
-					f.Type = p.type_()
-					typ.MethodList = append(typ.MethodList, f)
-					for p.got(_Comma) {
-						f := new(Field)
-						f.pos = p.pos()
-						f.Name = type_
-						f.Type = p.type_()
-						typ.MethodList = append(typ.MethodList, f)
-					}
-				} else {
-					p.syntaxError("expecting type")
-				}
-				return false
-			}
-
 		default:
 			if p.allowGenerics() {
 				pos := p.pos()
@@ -1488,13 +1464,8 @@ func (p *parser) interfaceType() *InterfaceType {
 		}
 
 		if p.allowGenerics() {
-			if p.mode&AllowTypeLists != 0 {
-				p.syntaxError("expecting method, type list, or embedded element")
-				p.advance(_Semi, _Rbrace, _Type)
-			} else {
-				p.syntaxError("expecting method or embedded element")
-				p.advance(_Semi, _Rbrace)
-			}
+			p.syntaxError("expecting method or embedded element")
+			p.advance(_Semi, _Rbrace)
 			return false
 		}
 
diff --git a/src/cmd/compile/internal/syntax/parser_test.go b/src/cmd/compile/internal/syntax/parser_test.go
index fb02c8b95f..29682012e5 100644
--- a/src/cmd/compile/internal/syntax/parser_test.go
+++ b/src/cmd/compile/internal/syntax/parser_test.go
@@ -46,7 +46,7 @@ func TestParseGo2(t *testing.T) {
 	for _, fi := range list {
 		name := fi.Name()
 		if !fi.IsDir() && !strings.HasPrefix(name, ".") {
-			ParseFile(filepath.Join(dir, name), func(err error) { t.Error(err) }, nil, AllowGenerics|AllowTypeSets|AllowTypeLists)
+			ParseFile(filepath.Join(dir, name), func(err error) { t.Error(err) }, nil, AllowGenerics|AllowTypeSets)
 		}
 	}
 }
diff --git a/src/cmd/compile/internal/syntax/printer.go b/src/cmd/compile/internal/syntax/printer.go
index e557f5d924..c8d31799af 100644
--- a/src/cmd/compile/internal/syntax/printer.go
+++ b/src/cmd/compile/internal/syntax/printer.go
@@ -494,39 +494,16 @@ func (p *printer) printRawNode(n Node) {
 		p.printSignature(n)
 
 	case *InterfaceType:
-		// separate type list and method list
-		var types []Expr
-		var methods []*Field
-		for _, f := range n.MethodList {
-			if f.Name != nil && f.Name.Value == "type" {
-				types = append(types, f.Type)
-			} else {
-				// method or embedded interface
-				methods = append(methods, f)
-			}
-		}
-
-		multiLine := len(n.MethodList) > 0 && p.linebreaks
 		p.print(_Interface)
-		if multiLine {
+		if p.linebreaks && len(n.MethodList) > 1 {
 			p.print(blank)
-		}
-		p.print(_Lbrace)
-		if multiLine {
+			p.print(_Lbrace)
 			p.print(newline, indent)
-		}
-		if len(types) > 0 {
-			p.print(_Type, blank)
-			p.printExprList(types)
-			if len(methods) > 0 {
-				p.print(_Semi, blank)
-			}
-		}
-		if len(methods) > 0 {
-			p.printMethodList(methods)
-		}
-		if multiLine {
+			p.printMethodList(n.MethodList)
 			p.print(outdent, newline)
+		} else {
+			p.print(_Lbrace)
+			p.printMethodList(n.MethodList)
 		}
 		p.print(_Rbrace)
 
diff --git a/src/cmd/compile/internal/syntax/printer_test.go b/src/cmd/compile/internal/syntax/printer_test.go
index ee083ad159..9b5331b148 100644
--- a/src/cmd/compile/internal/syntax/printer_test.go
+++ b/src/cmd/compile/internal/syntax/printer_test.go
@@ -60,12 +60,12 @@ var stringTests = []string{
 	// generic type declarations
 	"package p; type _[T any] struct{}",
 	"package p; type _[A, B, C interface{m()}] struct{}",
-	"package p; type _[T any, A, B, C interface{m()}, X, Y, Z interface{type int}] struct{}",
+	"package p; type _[T any, A, B, C interface{m()}, X, Y, Z interface{~int}] struct{}",
 
 	// generic function declarations
 	"package p; func _[T any]()",
 	"package p; func _[A, B, C interface{m()}]()",
-	"package p; func _[T any, A, B, C interface{m()}, X, Y, Z interface{type int}]()",
+	"package p; func _[T any, A, B, C interface{m()}, X, Y, Z interface{~int}]()",
 
 	// methods with generic receiver types
 	"package p; func (R[T]) _()",
@@ -94,7 +94,7 @@ var stringTests = []string{
 
 func TestPrintString(t *testing.T) {
 	for _, want := range stringTests {
-		ast, err := Parse(nil, strings.NewReader(want), nil, nil, AllowGenerics|AllowTypeSets|AllowTypeLists)
+		ast, err := Parse(nil, strings.NewReader(want), nil, nil, AllowGenerics|AllowTypeSets)
 		if err != nil {
 			t.Error(err)
 			continue
@@ -140,10 +140,10 @@ var exprTests = [][2]string{
 	dup("func(int, float32) string"),
 	dup("interface{m()}"),
 	dup("interface{m() string; n(x int)}"),
-	dup("interface{type int}"),
-	dup("interface{type int, float64, string}"),
-	dup("interface{type int; m()}"),
-	dup("interface{type int, float64, string; m() string; n(x int)}"),
+	dup("interface{~int}"),
+	dup("interface{~int | ~float64 | ~string}"),
+	dup("interface{~int; m()}"),
+	dup("interface{~int | ~float64 | ~string; m() string; n(x int)}"),
 	dup("map[string]int"),
 	dup("chan E"),
 	dup("<-chan E"),
@@ -155,7 +155,7 @@ var exprTests = [][2]string{
 	dup("interface{~int}"),
 	dup("interface{int | string}"),
 	dup("interface{~int | ~string; float64; m()}"),
-	dup("interface{type a, b, c; ~int | ~string; float64; m()}"),
+	dup("interface{~a | ~b | ~c; ~int | ~string; float64; m()}"),
 	dup("interface{~T[int, string] | string}"),
 
 	// non-type expressions
@@ -214,7 +214,7 @@ var exprTests = [][2]string{
 func TestShortString(t *testing.T) {
 	for _, test := range exprTests {
 		src := "package p; var _ = " + test[0]
-		ast, err := Parse(nil, strings.NewReader(src), nil, nil, AllowGenerics|AllowTypeLists)
+		ast, err := Parse(nil, strings.NewReader(src), nil, nil, AllowGenerics)
 		if err != nil {
 			t.Errorf("%s: %s", test[0], err)
 			continue
diff --git a/src/cmd/compile/internal/syntax/syntax.go b/src/cmd/compile/internal/syntax/syntax.go
index 8828c39ad5..49ba87786e 100644
--- a/src/cmd/compile/internal/syntax/syntax.go
+++ b/src/cmd/compile/internal/syntax/syntax.go
@@ -17,8 +17,7 @@ type Mode uint
 const (
 	CheckBranches Mode = 1 << iota // check correct use of labels, break, continue, and goto statements
 	AllowGenerics
-	AllowTypeSets  // requires AllowGenerics; remove once #48424 is decided
-	AllowTypeLists // requires AllowGenerics; remove once 1.18 is out
+	AllowTypeSets // requires AllowGenerics; remove once #48424 is decided
 )
 
 // Error describes a syntax error. Error implements the error interface.
diff --git a/src/cmd/compile/internal/syntax/testdata/go2/typeinst2.go2 b/src/cmd/compile/internal/syntax/testdata/go2/typeinst2.go2
index f3deb703b6..76b8d5591f 100644
--- a/src/cmd/compile/internal/syntax/testdata/go2/typeinst2.go2
+++ b/src/cmd/compile/internal/syntax/testdata/go2/typeinst2.go2
@@ -148,31 +148,7 @@ func _[T any](r R2[T, int], p *R2[string, T]) {
 	p.pm()
 }
 
-// An interface can (explicitly) declare at most one type list.
-type _ interface {
-	m0()
-	type int, string, bool
-	type /* ERROR multiple type lists */ float32, float64
-	m1()
-	m2()
-	type /* ERROR multiple type lists */ complex64, complex128
-	type /* ERROR multiple type lists */ rune
-}
-
-// Interface type lists may contain each type at most once.
-// (If there are multiple lists, we assume the author intended
-// for them to be all in a single list, and we report the error
-// as well.)
-type _ interface {
-	type int, int /* ERROR duplicate type int */
-	type /* ERROR multiple type lists */ int /* ERROR duplicate type int */
-}
-
-type _ interface {
-	type struct{f int}, struct{g int}, struct /* ERROR duplicate type */ {f int}
-}
-
-// Interface type lists can contain any type, incl. *Named types.
+// Interface type constraints can contain any type, incl. *Named types.
 // Verify that we use the underlying type to compute the operational type.
 type MyInt int
 func add1[T interface{ ~MyInt }](x T) T {
@@ -184,9 +160,9 @@ func double[T interface{ ~MyInt | ~MyString }](x T) T {
 	return x + x
 }
 
-// Embedding of interfaces with type lists leads to interfaces
-// with type lists that are the intersection of the embedded
-// type lists.
+// Embedding of interfaces with type constraints leads to interfaces
+// with type constraints that are the intersection of the embedded
+// type constraints.
 
 type E0 interface {
 	~int | ~bool | ~string
@@ -246,7 +222,7 @@ var _ = f12[float64]
 
 type I0_ interface {
 	E0
-	type int
+	~int
 }
 
 func f0_[T I0_]()
diff --git a/src/cmd/compile/internal/syntax/testdata/interface.go2 b/src/cmd/compile/internal/syntax/testdata/interface.go2
index b399d75148..dbc4187989 100644
--- a/src/cmd/compile/internal/syntax/testdata/interface.go2
+++ b/src/cmd/compile/internal/syntax/testdata/interface.go2
@@ -4,16 +4,11 @@
 
 // This file contains test cases for interfaces containing
 // constraint elements.
-//
-// For now, we accept both ordinary type lists and the
-// more complex constraint elements.
 
 package p
 
 type _ interface {
 	m()
-	type int
-	type int, string
 	E
 }
 
@@ -31,7 +26,6 @@ type _ interface {
 	T[int, string] | string
 	int | ~T[string, struct{}]
 	~int | ~string
-	type bool, int, float64
 }
 
 type _ interface {
diff --git a/src/cmd/compile/internal/types2/check_test.go b/src/cmd/compile/internal/types2/check_test.go
index 1ca2eea5c6..5b2f09425b 100644
--- a/src/cmd/compile/internal/types2/check_test.go
+++ b/src/cmd/compile/internal/types2/check_test.go
@@ -100,7 +100,7 @@ func testFiles(t *testing.T, filenames []string, colDelta uint, manual bool) {
 
 	var mode syntax.Mode
 	if strings.HasSuffix(filenames[0], ".go2") {
-		mode |= syntax.AllowGenerics | syntax.AllowTypeSets | syntax.AllowTypeLists
+		mode |= syntax.AllowGenerics | syntax.AllowTypeSets
 	}
 	// parse files and collect parser errors
 	files, errlist := parseFiles(t, filenames, mode)
diff --git a/src/cmd/compile/internal/types2/interface.go b/src/cmd/compile/internal/types2/interface.go
index 431ba93c17..0879d29d3d 100644
--- a/src/cmd/compile/internal/types2/interface.go
+++ b/src/cmd/compile/internal/types2/interface.go
@@ -93,9 +93,6 @@ func (t *Interface) String() string   { return TypeString(t, nil) }
 // Implementation
 
 func (check *Checker) interfaceType(ityp *Interface, iface *syntax.InterfaceType, def *Named) {
-	var tlist []syntax.Expr // types collected from all type lists
-	var tname *syntax.Name  // most recent "type" name
-
 	addEmbedded := func(pos syntax.Pos, typ Type) {
 		ityp.embeddeds = append(ityp.embeddeds, typ)
 		if ityp.embedPos == nil {
@@ -122,31 +119,6 @@ func (check *Checker) interfaceType(ityp *Interface, iface *syntax.InterfaceType
 			continue // ignore
 		}
 
-		// TODO(gri) Remove type list handling once the parser doesn't accept type lists anymore.
-		if name == "type" {
-			// Report an error for the first type list per interface
-			// if we don't allow type lists, but continue.
-			if !check.conf.AllowTypeLists && tlist == nil {
-				check.softErrorf(f.Name, "use generalized embedding syntax instead of a type list")
-			}
-			// For now, collect all type list entries as if it
-			// were a single union, where each union element is
-			// of the form ~T.
-			op := new(syntax.Operation)
-			// We should also set the position (but there is no setter);
-			// we don't care because this code will eventually go away.
-			op.Op = syntax.Tilde
-			op.X = f.Type
-			tlist = append(tlist, op)
-			// Report an error if we have multiple type lists in an
-			// interface, but only if they are permitted in the first place.
-			if check.conf.AllowTypeLists && tname != nil && tname != f.Name {
-				check.error(f.Name, "cannot have multiple type lists in an interface")
-			}
-			tname = f.Name
-			continue
-		}
-
 		typ := check.typ(f.Type)
 		sig, _ := typ.(*Signature)
 		if sig == nil {
@@ -175,13 +147,6 @@ func (check *Checker) interfaceType(ityp *Interface, iface *syntax.InterfaceType
 		ityp.methods = append(ityp.methods, m)
 	}
 
-	// If we saw a type list, add it like an embedded union.
-	if tlist != nil {
-		// Types T in a type list are added as ~T expressions but we don't
-		// have the position of the '~'. Use the first type position instead.
-		addEmbedded(tlist[0].(*syntax.Operation).X.Pos(), parseUnion(check, tlist))
-	}
-
 	// All methods and embedded elements for this interface are collected;
 	// i.e., this interface may be used in a type set computation.
 	ityp.complete = true
diff --git a/src/cmd/compile/internal/types2/testdata/check/typeinst2.go2 b/src/cmd/compile/internal/types2/testdata/check/typeinst2.go2
index d087c26a47..49f48c7283 100644
--- a/src/cmd/compile/internal/types2/testdata/check/typeinst2.go2
+++ b/src/cmd/compile/internal/types2/testdata/check/typeinst2.go2
@@ -159,10 +159,7 @@ type _ interface {
 	~rune
 }
 
-// Interface type lists may contain each type at most once.
-// (If there are multiple lists, we assume the author intended
-// for them to be all in a single list, and we report the error
-// as well.)
+// Type sets may contain each type at most once.
 type _ interface {
 	~int|~int /* ERROR overlapping terms ~int */
 	~int|int /* ERROR overlapping terms int */
diff --git a/src/cmd/compile/internal/types2/testdata/examples/constraints.go2 b/src/cmd/compile/internal/types2/testdata/examples/constraints.go2
index ecc75c1a46..4d7f70313a 100644
--- a/src/cmd/compile/internal/types2/testdata/examples/constraints.go2
+++ b/src/cmd/compile/internal/types2/testdata/examples/constraints.go2
@@ -6,18 +6,6 @@
 
 package p
 
-type (
-	// Type lists are processed as unions but an error is reported.
-	// TODO(gri) remove this once the parser doesn't accept type lists anymore.
-	_ interface{
-		type /* ERROR use generalized embedding syntax instead of a type list */ int
-	}
-	_ interface{
-		type /* ERROR use generalized embedding syntax instead of a type list */ int
-		type float32
-	}
-)
-
 type MyInt int
 
 type (