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cmd/compile/internal/syntax: allow eliding interface in constraint literals

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This CL permits an arbitrary type as well as the type sets  ~T and A|B
in constraint position, without the need of a surrrounding interface.
For instance, the type parameter list

	[P interface{ ~map[K]V }, K comparable, V interface{ ~string }]

may be written as

	[P ~map[K]V, K comparable, V ~string]

The feature must be enabled explicitly with the AllowTypeSets mode
and is only available if AllowGenerics is set as well.

For #48424.

Change-Id: Ic70bb97a49ff75e67e040853eac10e6aed0fef1a
Reviewed-on: https://go-review.googlesource.com/c/go/+/353133
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>
This commit is contained in:
Robert Griesemer 2021-09-29 11:14:05 -07:00
parent f19b2d50c6
commit 5279e534b5
6 changed files with 133 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/cmd/compile/internal/syntax/error_test.go
View File

@ -130,7 +130,7 @@ func testSyntaxErrors(t *testing.T, filename string) {
var mode Mode
if strings.HasSuffix(filename, ".go2") {
mode = AllowGenerics | AllowTypeLists
mode = AllowGenerics | AllowTypeSets | AllowTypeLists
}
ParseFile(filename, func(err error) {
e, ok := err.(Error)

68
src/cmd/compile/internal/syntax/parser.go
View File

@ -87,6 +87,8 @@ func (p *parser) init(file *PosBase, r io.Reader, errh ErrorHandler, pragh Pragm
p.indent = nil
}
func (p *parser) allowGenerics() bool { return p.mode&AllowGenerics != 0 }
// takePragma returns the current parsed pragmas
// and clears them from the parser state.
func (p *parser) takePragma() Pragma {
@ -597,7 +599,7 @@ func (p *parser) typeDecl(group *Group) Decl {
p.xnest++
x := p.expr()
p.xnest--
if name0, ok := x.(*Name); p.mode&AllowGenerics != 0 && ok && p.tok != _Rbrack {
if name0, ok := x.(*Name); p.allowGenerics() && ok && p.tok != _Rbrack {
// generic type
d.TParamList = p.paramList(name0, _Rbrack, true)
pos := p.pos()
@ -687,7 +689,7 @@ func (p *parser) funcDeclOrNil() *FuncDecl {
}
f.Name = p.name()
if p.mode&AllowGenerics != 0 && p.got(_Lbrack) {
if p.allowGenerics() && p.got(_Lbrack) {
if p.tok == _Rbrack {
p.syntaxError("empty type parameter list")
p.next()
@ -1425,7 +1427,7 @@ func (p *parser) interfaceType() *InterfaceType {
switch p.tok {
case _Name:
f := p.methodDecl()
if f.Name == nil && p.mode&AllowGenerics != 0 {
if f.Name == nil && p.allowGenerics() {
f = p.embeddedElem(f)
}
typ.MethodList = append(typ.MethodList, f)
@ -1443,14 +1445,14 @@ func (p *parser) interfaceType() *InterfaceType {
return false
case _Operator:
if p.op == Tilde && p.mode&AllowGenerics != 0 {
if p.op == Tilde && p.allowGenerics() {
typ.MethodList = append(typ.MethodList, p.embeddedElem(nil))
return false
}
case _Type:
// TODO(gri) remove TypeList syntax if we accept #45346
if p.mode&AllowGenerics != 0 && p.mode&AllowTypeLists != 0 {
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 {
@ -1473,7 +1475,7 @@ func (p *parser) interfaceType() *InterfaceType {
}
default:
if p.mode&AllowGenerics != 0 {
if p.allowGenerics() {
pos := p.pos()
if t := p.typeOrNil(); t != nil {
f := new(Field)
@ -1485,7 +1487,7 @@ func (p *parser) interfaceType() *InterfaceType {
}
}
if p.mode&AllowGenerics != 0 {
if p.allowGenerics() {
if p.mode&AllowTypeLists != 0 {
p.syntaxError("expecting method, type list, or embedded element")
p.advance(_Semi, _Rbrace, _Type)
@ -1570,7 +1572,7 @@ func (p *parser) fieldDecl(styp *StructType) {
// Careful dance: We don't know if we have an embedded instantiated
// type T[P1, P2, ...] or a field T of array/slice type [P]E or []E.
if p.mode&AllowGenerics != 0 && len(names) == 1 && p.tok == _Lbrack {
if p.allowGenerics() && len(names) == 1 && p.tok == _Lbrack {
typ = p.arrayOrTArgs()
if typ, ok := typ.(*IndexExpr); ok {
// embedded type T[P1, P2, ...]
@ -1708,7 +1710,7 @@ func (p *parser) methodDecl() *Field {
f.Type = p.funcType()
case _Lbrack:
if p.mode&AllowGenerics != 0 {
if p.allowGenerics() {
// Careful dance: We don't know if we have a generic method m[T C](x T)
// or an embedded instantiated type T[P1, P2] (we accept generic methods
// for generality and robustness of parsing).
@ -1846,38 +1848,60 @@ func (p *parser) paramDeclOrNil(name *Name, follow token) *Field {
defer p.trace("paramDecl")()
}
f := new(Field)
// type set notation is ok in type parameter lists
typeSetsOk := p.mode&AllowTypeSets != 0 && follow == _Rbrack
pos := p.pos()
if name != nil {
f.pos = name.pos
} else {
f.pos = p.pos()
pos = name.pos
} else if typeSetsOk && p.tok == _Operator && p.op == Tilde {
// "~" ...
return p.embeddedElem(nil)
}
f := new(Field)
f.pos = pos
if p.tok == _Name || name != nil {
// name
if name == nil {
name = p.name()
}
if p.mode&AllowGenerics != 0 && p.tok == _Lbrack {
if p.allowGenerics() && p.tok == _Lbrack {
// name "[" ...
f.Type = p.arrayOrTArgs()
if typ, ok := f.Type.(*IndexExpr); ok {
// name "[" ... "]"
typ.X = name
} else {
// name "[" n "]" E
f.Name = name
}
return f
}
if p.tok == _Dot {
// name_or_type
// name "." ...
f.Type = p.qualifiedName(name)
if typeSetsOk && p.tok == _Operator && p.op == Or {
// name "." name "|" ...
f = p.embeddedElem(f)
}
return f
}
if typeSetsOk && p.tok == _Operator && p.op == Or {
// name "|" ...
f.Type = name
return p.embeddedElem(f)
}
f.Name = name
}
if p.tok == _DotDotDot {
// [name] "..." ...
t := new(DotsType)
t.pos = p.pos()
p.next()
@ -1890,7 +1914,17 @@ func (p *parser) paramDeclOrNil(name *Name, follow token) *Field {
return f
}
if typeSetsOk && p.tok == _Operator && p.op == Tilde {
// [name] "~" ...
f.Type = p.embeddedElem(nil).Type
return f
}
f.Type = p.typeOrNil()
if typeSetsOk && p.tok == _Operator && p.op == Or && f.Type != nil {
// [name] type "|"
f = p.embeddedElem(f)
}
if f.Name != nil || f.Type != nil {
return f
}
@ -1952,7 +1986,7 @@ func (p *parser) paramList(name *Name, close token, requireNames bool) (list []*
if par.Type != nil {
typ = par.Type
if par.Name == nil {
pos = typ.Pos()
pos = StartPos(typ)
par.Name = NewName(pos, "_")
}
} else if typ != nil {
@ -2654,7 +2688,7 @@ func (p *parser) qualifiedName(name *Name) Expr {
x = s
}
if p.mode&AllowGenerics != 0 && p.tok == _Lbrack {
if p.allowGenerics() && p.tok == _Lbrack {
x = p.typeInstance(x)
}

6
src/cmd/compile/internal/syntax/parser_test.go
View File

@ -26,11 +26,11 @@ var (
)
func TestParse(t *testing.T) {
ParseFile(*src_, func(err error) { t.Error(err) }, nil, AllowGenerics)
ParseFile(*src_, func(err error) { t.Error(err) }, nil, AllowGenerics|AllowTypeSets)
}
func TestVerify(t *testing.T) {
ast, err := ParseFile(*src_, func(err error) { t.Error(err) }, nil, AllowGenerics)
ast, err := ParseFile(*src_, func(err error) { t.Error(err) }, nil, AllowGenerics|AllowTypeSets)
if err != nil {
return // error already reported
}
@ -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|AllowTypeLists)
ParseFile(filepath.Join(dir, name), func(err error) { t.Error(err) }, nil, AllowGenerics|AllowTypeSets|AllowTypeLists)
}
}
}

6
src/cmd/compile/internal/syntax/printer_test.go
View File

@ -72,6 +72,10 @@ var stringTests = []string{
"package p; func (*R[A, B, C]) _()",
"package p; func (_ *R[A, B, C]) _()",
// type constraint literals with elided interfaces (only if AllowTypeSets is set)
"package p; func _[P ~int, Q int | string]() {}",
"package p; func _[P struct{f int}, Q *P]() {}",
// channels
"package p; type _ chan chan int",
"package p; type _ chan (<-chan int)",
@ -90,7 +94,7 @@ var stringTests = []string{
func TestPrintString(t *testing.T) {
for _, want := range stringTests {
ast, err := Parse(nil, strings.NewReader(want), nil, nil, AllowGenerics|AllowTypeLists)
ast, err := Parse(nil, strings.NewReader(want), nil, nil, AllowGenerics|AllowTypeSets|AllowTypeLists)
if err != nil {
t.Error(err)
continue

1
src/cmd/compile/internal/syntax/syntax.go
View File

@ -17,6 +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
)

72
src/cmd/compile/internal/syntax/testdata/typeset.go2 vendored Normal file
View File

@ -0,0 +1,72 @@
// Copyright 2021 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.
// This file contains test cases for typeset-only constraint elements.
// TODO(gri) gofmt once/if gofmt supports this notation.
package p
type (
_[_ t] t
_[_ ~t] t
_[_ t|t] t
_[_ ~t|t] t
_[_ t|~t] t
_[_ ~t|~t] t
_[_ t, _, _ t|t] t
_[_ t, _, _ ~t|t] t
_[_ t, _, _ t|~t] t
_[_ t, _, _ ~t|~t] t
_[_ t.t] t
_[_ ~t.t] t
_[_ t.t|t.t] t
_[_ ~t.t|t.t] t
_[_ t.t|~t.t] t
_[_ ~t.t|~t.t] t
_[_ t, _, _ t.t|t.t] t
_[_ t, _, _ ~t.t|t.t] t
_[_ t, _, _ t.t|~t.t] t
_[_ t, _, _ ~t.t|~t.t] t
_[_ struct{}] t
_[_ ~struct{}] t
_[_ struct{}|t] t
_[_ ~struct{}|t] t
_[_ struct{}|~t] t
_[_ ~struct{}|~t] t
_[_ t|struct{}] t
_[_ ~t|struct{}] t
_[_ t|~struct{}] t
_[_ ~t|~struct{}] t
)
// Single-expression type parameter lists and those that don't start
// with a (type parameter) name are considered array sizes.
// The term must be a valid expression (it could be a type - and then
// a type-checker will complain - but we don't allow ~ in the expr).
type (
_[t] t
_[/* ERROR unexpected ~ */ ~t] t
_[t|t] t
_[/* ERROR unexpected ~ */ ~t|t] t
_[t| /* ERROR unexpected ~ */ ~t] t
_[/* ERROR unexpected ~ */ ~t|~t] t
)
type (
_[_ t, t /* ERROR missing type constraint */ ] t
_[_ ~t, t /* ERROR missing type constraint */ ] t
_[_ t, /* ERROR type parameters must be named */ ~t] t
_[_ ~t, /* ERROR type parameters must be named */ ~t] t
_[_ t|t, /* ERROR type parameters must be named */ t|t] t
_[_ ~t|t, /* ERROR type parameters must be named */ t|t] t
_[_ t|t, /* ERROR type parameters must be named */ ~t|t] t
_[_ ~t|t, /* ERROR type parameters must be named */ ~t|t] t
)