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go/*,cmd/gofmt: guard AST changes with the typeparams build tag

Browse source 
This CL changes our approach to guarding type parameter functionality
and API. Previously, we guarded type parameter functionality with the
parser.parseTypeParams parser mode, and were in the process of hiding
the type parameter API behind the go1.18 build constraint.

These mechanisms had several limitations:
 + Requiring the parser.parseTypeParams mode to be set meant that
   existing tooling would have to opt-in to type parameters in all
   places where it parses Go files.
 + The parseTypeParams mode value had to be copied in several places.
 + go1.18 is not specific to typeparams, making it difficult to set up
   the builders to run typeparams tests.

This CL addresses the above limitations, and completes the task of
hiding the AST API, by switching to a new 'typeparams' build constraint
and adding a new go/internal/typeparams helper package.

The typeparams build constraint is used to conditionally compile the new
AST changes. The typeparams package provides utilities for accessing and
writing the new AST data, so that we don't have to fragment our parser
or type checker logic across build constraints. The typeparams.Enabled
const is used to guard tests that require type parameter support.

The parseTypeParams parser mode is gone, replaced by a new
typeparams.DisableParsing mode with the opposite sense. Now, type
parameters are only parsed if go/parser is compiled with the typeparams
build constraint set AND typeparams.DisableParsing not set. This new
parser mode allows opting out of type parameter parsing for tests.

How exactly to run tests on builders is left to a follow-up CL.

Updates #44933

Change-Id: I3091e42a2e5e2f23e8b2ae584f415a784b9fbd65
Reviewed-on: https://go-review.googlesource.com/c/go/+/300649
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>
This commit is contained in:
Rob Findley 2021-03-05 10:57:48 -05:00 committed by Robert Findley
parent 693859542e
commit efaf75a216
35 changed files with 417 additions and 213 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

11
src/cmd/gofmt/gofmt.go
View file

@ -33,10 +33,6 @@ var (
doDiff = flag.Bool("d", false, "display diffs instead of rewriting files")
allErrors = flag.Bool("e", false, "report all errors (not just the first 10 on different lines)")
// allowTypeParams controls whether type parameters are allowed in the code
// being formatted. It is enabled for go1.18 in gofmt_go1.18.go.
allowTypeParams = false
// debugging
cpuprofile = flag.String("cpuprofile", "", "write cpu profile to this file")
)
@ -53,10 +49,6 @@ const (
printerNormalizeNumbers = 1 << 30
)
// parseTypeParams tells go/parser to parse type parameters. Must be kept in
// sync with go/parser/interface.go.
const parseTypeParams parser.Mode = 1 << 30
var (
fileSet = token.NewFileSet() // per process FileSet
exitCode = 0
@ -79,9 +71,6 @@ func initParserMode() {
if *allErrors {
parserMode |= parser.AllErrors
}
if allowTypeParams {
parserMode |= parseTypeParams
}
}
func isGoFile(f fs.DirEntry) bool {

9
src/cmd/gofmt/gofmt_test.go
View file

@ -49,12 +49,13 @@ func gofmtFlags(filename string, maxLines int) string {
case scanner.EOF:
return ""
}
}
return ""
}
var typeParamsEnabled = false
func runTest(t *testing.T, in, out string) {
// process flags
*simplifyAST = false
@ -78,8 +79,10 @@ func runTest(t *testing.T, in, out string) {
// fake flag - pretend input is from stdin
stdin = true
case "-G":
// fake flag - allow parsing type parameters
allowTypeParams = true
// fake flag - test is for generic code
if !typeParamsEnabled {
return
}
default:
t.Errorf("unrecognized flag name: %s", name)
}

6
src/cmd/gofmt/gofmt_go1.18.go → src/cmd/gofmt/gofmt_typeparams_test.go
View file

@ -2,11 +2,11 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build go1.18
// +build go1.18
//go:build typeparams
// +build typeparams
package main
func init() {
allowTypeParams = true
typeParamsEnabled = true
}

62
src/go/ast/ast.go
View file

@ -374,13 +374,6 @@ type (
Rparen token.Pos // position of ")"
}
// A ListExpr node represents a list of expressions separated by commas.
// ListExpr nodes are used as index in IndexExpr nodes representing type
// or function instantiations with more than one type argument.
ListExpr struct {
ElemList []Expr
}
// A StarExpr node represents an expression of the form "*" Expression.
// Semantically it could be a unary "*" expression, or a pointer type.
//
@ -447,14 +440,6 @@ type (
// Pointer types are represented via StarExpr nodes.
// A FuncType node represents a function type.
FuncType struct {
Func token.Pos // position of "func" keyword (token.NoPos if there is no "func")
TParams *FieldList // type parameters; or nil
Params *FieldList // (incoming) parameters; non-nil
Results *FieldList // (outgoing) results; or nil
}
// An InterfaceType node represents an interface type.
InterfaceType struct {
Interface token.Pos // position of "interface" keyword
@ -497,18 +482,12 @@ func (x *IndexExpr) Pos() token.Pos { return x.X.Pos() }
func (x *SliceExpr) Pos() token.Pos { return x.X.Pos() }
func (x *TypeAssertExpr) Pos() token.Pos { return x.X.Pos() }
func (x *CallExpr) Pos() token.Pos { return x.Fun.Pos() }
func (x *ListExpr) Pos() token.Pos {
if len(x.ElemList) > 0 {
return x.ElemList[0].Pos()
}
return token.NoPos
}
func (x *StarExpr) Pos() token.Pos { return x.Star }
func (x *UnaryExpr) Pos() token.Pos { return x.OpPos }
func (x *BinaryExpr) Pos() token.Pos { return x.X.Pos() }
func (x *KeyValueExpr) Pos() token.Pos { return x.Key.Pos() }
func (x *ArrayType) Pos() token.Pos { return x.Lbrack }
func (x *StructType) Pos() token.Pos { return x.Struct }
func (x *StarExpr) Pos() token.Pos { return x.Star }
func (x *UnaryExpr) Pos() token.Pos { return x.OpPos }
func (x *BinaryExpr) Pos() token.Pos { return x.X.Pos() }
func (x *KeyValueExpr) Pos() token.Pos { return x.Key.Pos() }
func (x *ArrayType) Pos() token.Pos { return x.Lbrack }
func (x *StructType) Pos() token.Pos { return x.Struct }
func (x *FuncType) Pos() token.Pos {
if x.Func.IsValid() || x.Params == nil { // see issue 3870
return x.Func
@ -536,18 +515,12 @@ func (x *IndexExpr) End() token.Pos { return x.Rbrack + 1 }
func (x *SliceExpr) End() token.Pos { return x.Rbrack + 1 }
func (x *TypeAssertExpr) End() token.Pos { return x.Rparen + 1 }
func (x *CallExpr) End() token.Pos { return x.Rparen + 1 }
func (x *ListExpr) End() token.Pos {
if len(x.ElemList) > 0 {
return x.ElemList[len(x.ElemList)-1].End()
}
return token.NoPos
}
func (x *StarExpr) End() token.Pos { return x.X.End() }
func (x *UnaryExpr) End() token.Pos { return x.X.End() }
func (x *BinaryExpr) End() token.Pos { return x.Y.End() }
func (x *KeyValueExpr) End() token.Pos { return x.Value.End() }
func (x *ArrayType) End() token.Pos { return x.Elt.End() }
func (x *StructType) End() token.Pos { return x.Fields.End() }
func (x *StarExpr) End() token.Pos { return x.X.End() }
func (x *UnaryExpr) End() token.Pos { return x.X.End() }
func (x *BinaryExpr) End() token.Pos { return x.Y.End() }
func (x *KeyValueExpr) End() token.Pos { return x.Value.End() }
func (x *ArrayType) End() token.Pos { return x.Elt.End() }
func (x *StructType) End() token.Pos { return x.Fields.End() }
func (x *FuncType) End() token.Pos {
if x.Results != nil {
return x.Results.End()
@ -573,7 +546,6 @@ func (*IndexExpr) exprNode() {}
func (*SliceExpr) exprNode() {}
func (*TypeAssertExpr) exprNode() {}
func (*CallExpr) exprNode() {}
func (*ListExpr) exprNode() {}
func (*StarExpr) exprNode() {}
func (*UnaryExpr) exprNode() {}
func (*BinaryExpr) exprNode() {}
@ -920,16 +892,6 @@ type (
Values []Expr // initial values; or nil
Comment *CommentGroup // line comments; or nil
}
// A TypeSpec node represents a type declaration (TypeSpec production).
TypeSpec struct {
Doc *CommentGroup // associated documentation; or nil
Name *Ident // type name
TParams *FieldList // type parameters; or nil
Assign token.Pos // position of '=', if any
Type Expr // *Ident, *ParenExpr, *SelectorExpr, *StarExpr, or any of the *XxxTypes
Comment *CommentGroup // line comments; or nil
}
)
// Pos and End implementations for spec nodes.

28
src/go/ast/ast_notypeparams.go Normal file
View file

@ -0,0 +1,28 @@
// 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.
//go:build !typeparams
// +build !typeparams
package ast
import "go/token"
type (
// A FuncType node represents a function type.
FuncType struct {
Func token.Pos // position of "func" keyword (token.NoPos if there is no "func")
Params *FieldList // (incoming) parameters; non-nil
Results *FieldList // (outgoing) results; or nil
}
// A TypeSpec node represents a type declaration (TypeSpec production).
TypeSpec struct {
Doc *CommentGroup // associated documentation; or nil
Name *Ident // type name
Assign token.Pos // position of '=', if any
Type Expr // *Ident, *ParenExpr, *SelectorExpr, *StarExpr, or any of the *XxxTypes
Comment *CommentGroup // line comments; or nil
}
)

51
src/go/ast/ast_typeparams.go Normal file
View file

@ -0,0 +1,51 @@
// 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.
//go:build typeparams
// +build typeparams
package ast
import "go/token"
type (
// A FuncType node represents a function type.
FuncType struct {
Func token.Pos // position of "func" keyword (token.NoPos if there is no "func")
TParams *FieldList // type parameters; or nil
Params *FieldList // (incoming) parameters; non-nil
Results *FieldList // (outgoing) results; or nil
}
// A TypeSpec node represents a type declaration (TypeSpec production).
TypeSpec struct {
Doc *CommentGroup // associated documentation; or nil
Name *Ident // type name
TParams *FieldList // type parameters; or nil
Assign token.Pos // position of '=', if any
Type Expr // *Ident, *ParenExpr, *SelectorExpr, *StarExpr, or any of the *XxxTypes
Comment *CommentGroup // line comments; or nil
}
// A ListExpr node represents a list of expressions separated by commas.
// ListExpr nodes are used as index in IndexExpr nodes representing type
// or function instantiations with more than one type argument.
ListExpr struct {
ElemList []Expr
}
)
func (*ListExpr) exprNode() {}
func (x *ListExpr) Pos() token.Pos {
if len(x.ElemList) > 0 {
return x.ElemList[0].Pos()
}
return token.NoPos
}
func (x *ListExpr) End() token.Pos {
if len(x.ElemList) > 0 {
return x.ElemList[len(x.ElemList)-1].End()
}
return token.NoPos
}

15
src/go/ast/walk.go
View file

@ -4,8 +4,6 @@
package ast
import "fmt"
// A Visitor's Visit method is invoked for each node encountered by Walk.
// If the result visitor w is not nil, Walk visits each of the children
// of node with the visitor w, followed by a call of w.Visit(nil).
@ -116,9 +114,6 @@ func Walk(v Visitor, node Node) {
Walk(v, n.X)
Walk(v, n.Index)
case *ListExpr:
walkExprList(v, n.ElemList)
case *SliceExpr:
Walk(v, n.X)
if n.Low != nil {
@ -166,9 +161,7 @@ func Walk(v Visitor, node Node) {
Walk(v, n.Fields)
case *FuncType:
if n.TParams != nil {
Walk(v, n.TParams)
}
walkFuncTypeParams(v, n)
if n.Params != nil {
Walk(v, n.Params)
}
@ -323,9 +316,7 @@ func Walk(v Visitor, node Node) {
Walk(v, n.Doc)
}
Walk(v, n.Name)
if n.TParams != nil {
Walk(v, n.TParams)
}
walkTypeSpecParams(v, n)
Walk(v, n.Type)
if n.Comment != nil {
Walk(v, n.Comment)
@ -372,7 +363,7 @@ func Walk(v Visitor, node Node) {
}
default:
panic(fmt.Sprintf("ast.Walk: unexpected node type %T", n))
walkOtherNodes(v, n)
}
v.Visit(nil)

17
src/go/ast/walk_notypeparams.go Normal file
View file

@ -0,0 +1,17 @@
// 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.
//go:build !typeparams
// +build !typeparams
package ast
import "fmt"
func walkFuncTypeParams(v Visitor, n *FuncType) {}
func walkTypeSpecParams(v Visitor, n *TypeSpec) {}
func walkOtherNodes(v Visitor, n Node) {
panic(fmt.Sprintf("ast.Walk: unexpected node type %T", n))
}

30
src/go/ast/walk_typeparams.go Normal file
View file

@ -0,0 +1,30 @@
// 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.
//go:build typeparams
// +build typeparams
package ast
func walkFuncTypeParams(v Visitor, n *FuncType) {
if n.TParams != nil {
Walk(v, n.TParams)
}
}
func walkTypeSpecParams(v Visitor, n *TypeSpec) {
if n.TParams != nil {
Walk(v, n.TParams)
}
}
func walkOtherNodes(v Visitor, n Node) {
if e, ok := n.(*ast.ListExpr); ok {
if e != nil {
Walk(v, e)
}
} else {
panic(fmt.Sprintf("ast.Walk: unexpected node type %T", n))
}
}

1
src/go/build/deps_test.go
View file

@ -278,6 +278,7 @@ var depsRules = `
< go/token
< go/scanner
< go/ast
< go/internal/typeparams
< go/parser;
FMT

13
src/go/internal/typeparams/common.go Normal file
View file

@ -0,0 +1,13 @@
// 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.
// Package typeparams provides functions to work with type parameter data
// stored in the AST, while these AST changes are guarded by a build
// constraint.
package typeparams
// DisallowParsing is the numeric value of a parsing mode that disallows type
// parameters. This only matters if the typeparams experiment is active, and
// may be used for running tests that disallow generics.
const DisallowParsing = 1 << 30

38
src/go/internal/typeparams/notypeparams.go Normal file
View file

@ -0,0 +1,38 @@
// 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.
//go:build !typeparams
// +build !typeparams
package typeparams
import (
"go/ast"
)
const Enabled = false
func PackExpr(list []ast.Expr) ast.Expr {
switch len(list) {
case 0:
return nil
case 1:
return list[0]
default:
// The parser should not attempt to pack multiple expressions into an
// IndexExpr if type params are disabled.
panic("multiple index expressions are unsupported without type params")
}
}
func UnpackExpr(expr ast.Expr) []ast.Expr {
return []ast.Expr{expr}
}
func Get(ast.Node) *ast.FieldList {
return nil
}
func Set(node ast.Node, params *ast.FieldList) {
}

61
src/go/internal/typeparams/typeparams.go Normal file
View file

@ -0,0 +1,61 @@
// 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.
//go:build typeparams
// +build typeparams
package typeparams
import (
"fmt"
"go/ast"
)
const Enabled = true
func PackExpr(list []ast.Expr) ast.Expr {
switch len(list) {
case 0:
return nil
case 1:
return list[0]
default:
return &ast.ListExpr{ElemList: list}
}
}
// TODO(gri) Should find a more efficient solution that doesn't
// require introduction of a new slice for simple
// expressions.
func UnpackExpr(x ast.Expr) []ast.Expr {
if x, _ := x.(*ast.ListExpr); x != nil {
return x.ElemList
}
if x != nil {
return []ast.Expr{x}
}
return nil
}
func Get(n ast.Node) *ast.FieldList {
switch n := n.(type) {
case *ast.TypeSpec:
return n.TParams
case *ast.FuncType:
return n.TParams
default:
panic(fmt.Sprintf("node type %T has no type parameters", n))
}
}
func Set(n ast.Node, params *ast.FieldList) {
switch n := n.(type) {
case *ast.TypeSpec:
n.TParams = params
case *ast.FuncType:
n.TParams = params
default:
panic(fmt.Sprintf("node type %T has no type parameters", n))
}
}

7
src/go/parser/error_test.go
View file

@ -23,6 +23,7 @@
package parser
import (
"go/internal/typeparams"
"go/scanner"
"go/token"
"os"
@ -188,7 +189,11 @@ func TestErrors(t *testing.T) {
if !d.IsDir() && !strings.HasPrefix(name, ".") && (strings.HasSuffix(name, ".src") || strings.HasSuffix(name, ".go2")) {
mode := DeclarationErrors | AllErrors
if strings.HasSuffix(name, ".go2") {
mode |= parseTypeParams
if !typeparams.Enabled {
continue
}
} else {
mode |= typeparams.DisallowParsing
}
checkErrors(t, filepath.Join(testdata, name), nil, mode, true)
}

7
src/go/parser/interface.go
View file

@ -56,13 +56,6 @@ const (
DeclarationErrors // report declaration errors
SpuriousErrors // same as AllErrors, for backward-compatibility
AllErrors = SpuriousErrors // report all errors (not just the first 10 on different lines)
// parseTypeParams controls the parsing of type parameters. Must be
// kept in sync with:
// go/printer/printer_test.go
// go/types/check_test.go
// cmd/gofmt/gofmt.go
parseTypeParams = 1 << 30
)
// ParseFile parses the source code of a single Go source file and returns

42
src/go/parser/parser.go
View file

@ -19,6 +19,7 @@ package parser
import (
"fmt"
"go/ast"
"go/internal/typeparams"
"go/scanner"
"go/token"
"strconv"
@ -75,6 +76,10 @@ func (p *parser) init(fset *token.FileSet, filename string, src []byte, mode Mod
p.next()
}
func (p *parser) parseTypeParams() bool {
return typeparams.Enabled && p.mode&typeparams.DisallowParsing == 0
}
// ----------------------------------------------------------------------------
// Parsing support
@ -494,7 +499,7 @@ func (p *parser) parseQualifiedIdent(ident *ast.Ident) ast.Expr {
}
typ := p.parseTypeName(ident)
if p.tok == token.LBRACK && p.mode&parseTypeParams != 0 {
if p.tok == token.LBRACK && p.parseTypeParams() {
typ = p.parseTypeInstance(typ)
}
@ -553,7 +558,7 @@ func (p *parser) parseArrayFieldOrTypeInstance(x *ast.Ident) (*ast.Ident, ast.Ex
// TODO(rfindley): consider changing parseRhsOrType so that this function variable
// is not needed.
argparser := p.parseRhsOrType
if p.mode&parseTypeParams == 0 {
if !p.parseTypeParams() {
argparser = p.parseRhs
}
if p.tok != token.RBRACK {
@ -583,19 +588,19 @@ func (p *parser) parseArrayFieldOrTypeInstance(x *ast.Ident) (*ast.Ident, ast.Ex
// x [P]E
return x, &ast.ArrayType{Lbrack: lbrack, Len: args[0], Elt: elt}
}
if p.mode&parseTypeParams == 0 {
if !p.parseTypeParams() {
p.error(rbrack, "missing element type in array type expression")
return nil, &ast.BadExpr{From: args[0].Pos(), To: args[0].End()}
}
}
if p.mode&parseTypeParams == 0 {
if !p.parseTypeParams() {
p.error(firstComma, "expected ']', found ','")
return x, &ast.BadExpr{From: args[0].Pos(), To: args[len(args)-1].End()}
}
// x[P], x[P1, P2], ...
return nil, &ast.IndexExpr{X: x, Lbrack: lbrack, Index: &ast.ListExpr{ElemList: args}, Rbrack: rbrack}
return nil, &ast.IndexExpr{X: x, Lbrack: lbrack, Index: typeparams.PackExpr(args), Rbrack: rbrack}
}
func (p *parser) parseFieldDecl() *ast.Field {
@ -878,7 +883,7 @@ func (p *parser) parseParameters(acceptTParams bool) (tparams, params *ast.Field
defer un(trace(p, "Parameters"))
}
if p.mode&parseTypeParams != 0 && acceptTParams && p.tok == token.LBRACK {
if p.parseTypeParams() && acceptTParams && p.tok == token.LBRACK {
opening := p.pos
p.next()
// [T any](params) syntax
@ -951,7 +956,7 @@ func (p *parser) parseMethodSpec() *ast.Field {
x := p.parseTypeName(nil)
if ident, _ := x.(*ast.Ident); ident != nil {
switch {
case p.tok == token.LBRACK && p.mode&parseTypeParams != 0:
case p.tok == token.LBRACK && p.parseTypeParams():
// generic method or embedded instantiated type
lbrack := p.pos
p.next()
@ -967,7 +972,8 @@ func (p *parser) parseMethodSpec() *ast.Field {
_, params := p.parseParameters(false)
results := p.parseResult()
idents = []*ast.Ident{ident}
typ = &ast.FuncType{Func: token.NoPos, TParams: tparams, Params: params, Results: results}
typ = &ast.FuncType{Func: token.NoPos, Params: params, Results: results}
typeparams.Set(typ, tparams)
} else {
// embedded instantiated type
// TODO(rfindley) should resolve all identifiers in x.
@ -984,7 +990,7 @@ func (p *parser) parseMethodSpec() *ast.Field {
p.exprLev--
}
rbrack := p.expectClosing(token.RBRACK, "type argument list")
typ = &ast.IndexExpr{X: ident, Lbrack: lbrack, Index: &ast.ListExpr{ElemList: list}, Rbrack: rbrack}
typ = &ast.IndexExpr{X: ident, Lbrack: lbrack, Index: typeparams.PackExpr(list), Rbrack: rbrack}
}
case p.tok == token.LPAREN:
// ordinary method
@ -1000,7 +1006,7 @@ func (p *parser) parseMethodSpec() *ast.Field {
} else {
// embedded, possibly instantiated type
typ = x
if p.tok == token.LBRACK && p.mode&parseTypeParams != 0 {
if p.tok == token.LBRACK && p.parseTypeParams() {
// embedded instantiated interface
typ = p.parseTypeInstance(typ)
}
@ -1020,7 +1026,7 @@ func (p *parser) parseInterfaceType() *ast.InterfaceType {
pos := p.expect(token.INTERFACE)
lbrace := p.expect(token.LBRACE)
var list []*ast.Field
for p.tok == token.IDENT || p.mode&parseTypeParams != 0 && p.tok == token.TYPE {
for p.tok == token.IDENT || p.parseTypeParams() && p.tok == token.TYPE {
if p.tok == token.IDENT {
list = append(list, p.parseMethodSpec())
} else {
@ -1108,14 +1114,14 @@ func (p *parser) parseTypeInstance(typ ast.Expr) ast.Expr {
closing := p.expectClosing(token.RBRACK, "type argument list")
return &ast.IndexExpr{X: typ, Lbrack: opening, Index: &ast.ListExpr{ElemList: list}, Rbrack: closing}
return &ast.IndexExpr{X: typ, Lbrack: opening, Index: typeparams.PackExpr(list), Rbrack: closing}
}
func (p *parser) tryIdentOrType() ast.Expr {
switch p.tok {
case token.IDENT:
typ := p.parseTypeName(nil)
if p.tok == token.LBRACK && p.mode&parseTypeParams != 0 {
if p.tok == token.LBRACK && p.parseTypeParams() {
typ = p.parseTypeInstance(typ)
}
return typ
@ -1360,13 +1366,13 @@ func (p *parser) parseIndexOrSliceOrInstance(x ast.Expr) ast.Expr {
return &ast.IndexExpr{X: x, Lbrack: lbrack, Index: index[0], Rbrack: rbrack}
}
if p.mode&parseTypeParams == 0 {
if !p.parseTypeParams() {
p.error(firstComma, "expected ']' or ':', found ','")
return &ast.BadExpr{From: args[0].Pos(), To: args[len(args)-1].End()}
}
// instance expression
return &ast.IndexExpr{X: x, Lbrack: lbrack, Index: &ast.ListExpr{ElemList: args}, Rbrack: rbrack}
return &ast.IndexExpr{X: x, Lbrack: lbrack, Index: typeparams.PackExpr(args), Rbrack: rbrack}
}
func (p *parser) parseCallOrConversion(fun ast.Expr) *ast.CallExpr {
@ -2406,7 +2412,7 @@ func (p *parser) parseValueSpec(doc *ast.CommentGroup, _ token.Pos, keyword toke
func (p *parser) parseGenericType(spec *ast.TypeSpec, openPos token.Pos, name0 *ast.Ident, closeTok token.Token) {
list := p.parseParameterList(name0, closeTok, p.parseParamDecl, true)
closePos := p.expect(closeTok)
spec.TParams = &ast.FieldList{Opening: openPos, List: list, Closing: closePos}
typeparams.Set(spec, &ast.FieldList{Opening: openPos, List: list, Closing: closePos})
// Type alias cannot have type parameters. Accept them for robustness but complain.
if p.tok == token.ASSIGN {
p.error(p.pos, "generic type cannot be alias")
@ -2432,7 +2438,7 @@ func (p *parser) parseTypeSpec(doc *ast.CommentGroup, _ token.Pos, _ token.Token
p.exprLev++
x := p.parseExpr()
p.exprLev--
if name0, _ := x.(*ast.Ident); p.mode&parseTypeParams != 0 && name0 != nil && p.tok != token.RBRACK {
if name0, _ := x.(*ast.Ident); p.parseTypeParams() && name0 != nil && p.tok != token.RBRACK {
// generic type [T any];
p.parseGenericType(spec, lbrack, name0, token.RBRACK)
} else {
@ -2537,12 +2543,12 @@ func (p *parser) parseFuncDecl() *ast.FuncDecl {
Name: ident,
Type: &ast.FuncType{
Func: pos,
TParams: tparams,
Params: params,
Results: results,
},
Body: body,
}
typeparams.Set(decl.Type, tparams)
return decl
}

6
src/go/parser/resolver.go
View file

@ -7,6 +7,7 @@ package parser
import (
"fmt"
"go/ast"
"go/internal/typeparams"
"go/token"
)
@ -450,10 +451,10 @@ func (r *resolver) Visit(node ast.Node) ast.Visitor {
// at the identifier in the TypeSpec and ends at the end of the innermost
// containing block.
r.declare(spec, nil, r.topScope, ast.Typ, spec.Name)
if spec.TParams != nil {
if tparams := typeparams.Get(spec); tparams != nil {
r.openScope(spec.Pos())
defer r.closeScope()
r.walkFieldList(r.topScope, spec.TParams, ast.Typ)
r.walkFieldList(r.topScope, tparams, ast.Typ)
}
ast.Walk(r, spec.Type)
}
@ -476,7 +477,6 @@ func (r *resolver) Visit(node ast.Node) ast.Visitor {
}
func (r *resolver) walkFuncType(scope *ast.Scope, typ *ast.FuncType) {
r.walkFieldList(scope, typ.TParams, ast.Typ)
r.walkFieldList(scope, typ.Params, ast.Var)
r.walkFieldList(scope, typ.Results, ast.Var)
}

7
src/go/parser/resolver_test.go
View file

@ -7,6 +7,7 @@ package parser
import (
"fmt"
"go/ast"
"go/internal/typeparams"
"go/scanner"
"go/token"
"os"
@ -41,7 +42,11 @@ func TestResolution(t *testing.T) {
src := readFile(path) // panics on failure
var mode Mode
if strings.HasSuffix(path, ".go2") {
mode = parseTypeParams
if !typeparams.Enabled {
t.Skip("type params are not enabled")
}
} else {
mode |= typeparams.DisallowParsing
}
file, err := ParseFile(fset, path, src, mode)
if err != nil {

29
src/go/parser/short_test.go
View file

@ -6,7 +6,10 @@
package parser
import "testing"
import (
"go/internal/typeparams"
"testing"
)
var valids = []string{
"package p\n",
@ -130,19 +133,22 @@ func TestValid(t *testing.T) {
}
})
t.Run("tparams", func(t *testing.T) {
if !typeparams.Enabled {
t.Skip("type params are not enabled")
}
for _, src := range valids {
checkErrors(t, src, src, DeclarationErrors|AllErrors|parseTypeParams, false)
checkErrors(t, src, src, DeclarationErrors|AllErrors, false)
}
for _, src := range validWithTParamsOnly {
checkErrors(t, src, src, DeclarationErrors|AllErrors|parseTypeParams, false)
checkErrors(t, src, src, DeclarationErrors|AllErrors, false)
}
})
}
// TestSingle is useful to track down a problem with a single short test program.
func TestSingle(t *testing.T) {
const src = `package p; var _ = T[P]{}`
checkErrors(t, src, src, DeclarationErrors|AllErrors|parseTypeParams, true)
const src = `package p; var _ = T{}`
checkErrors(t, src, src, DeclarationErrors|AllErrors, true)
}
var invalids = []string{
@ -250,21 +256,24 @@ var invalidTParamErrs = []string{
func TestInvalid(t *testing.T) {
t.Run("no tparams", func(t *testing.T) {
for _, src := range invalids {
checkErrors(t, src, src, DeclarationErrors|AllErrors, true)
checkErrors(t, src, src, DeclarationErrors|AllErrors|typeparams.DisallowParsing, true)
}
for _, src := range validWithTParamsOnly {
checkErrors(t, src, src, DeclarationErrors|AllErrors, true)
checkErrors(t, src, src, DeclarationErrors|AllErrors|typeparams.DisallowParsing, true)
}
for _, src := range invalidNoTParamErrs {
checkErrors(t, src, src, DeclarationErrors|AllErrors, true)
checkErrors(t, src, src, DeclarationErrors|AllErrors|typeparams.DisallowParsing, true)
}
})
t.Run("tparams", func(t *testing.T) {
if !typeparams.Enabled {
t.Skip("type params are not enabled")
}
for _, src := range invalids {
checkErrors(t, src, src, DeclarationErrors|AllErrors|parseTypeParams, true)
checkErrors(t, src, src, DeclarationErrors|AllErrors, true)
}
for _, src := range invalidTParamErrs {
checkErrors(t, src, src, DeclarationErrors|AllErrors|parseTypeParams, true)
checkErrors(t, src, src, DeclarationErrors|AllErrors, true)
}
})
}

19
src/go/printer/nodes.go
View file

@ -11,6 +11,7 @@ package printer
import (
"bytes"
"go/ast"
"go/internal/typeparams"
"go/token"
"math"
"strconv"
@ -382,8 +383,8 @@ func (p *printer) parameters(fields *ast.FieldList, isTypeParam bool) {
}
func (p *printer) signature(sig *ast.FuncType) {
if sig.TParams != nil {
p.parameters(sig.TParams, true)
if tparams := typeparams.Get(sig); tparams != nil {
p.parameters(tparams, true)
}
if sig.Params != nil {
p.parameters(sig.Params, false)
@ -870,8 +871,14 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int) {
// TODO(gri): should treat[] like parentheses and undo one level of depth
p.expr1(x.X, token.HighestPrec, 1)
p.print(x.Lbrack, token.LBRACK)
if e, _ := x.Index.(*ast.ListExpr); e != nil {
p.exprList(x.Lbrack, e.ElemList, depth+1, commaTerm, x.Rbrack, false)
// Note: we're a bit defensive here to handle the case of a ListExpr of
// length 1.
if list := typeparams.UnpackExpr(x.Index); len(list) > 0 {
if len(list) > 1 {
p.exprList(x.Lbrack, list, depth+1, commaTerm, x.Rbrack, false)
} else {
p.expr0(list[0], depth+1)
}
} else {
p.expr0(x.Index, depth+1)
}
@ -1628,8 +1635,8 @@ func (p *printer) spec(spec ast.Spec, n int, doIndent bool) {
case *ast.TypeSpec:
p.setComment(s.Doc)
p.expr(s.Name)
if s.TParams != nil {
p.parameters(s.TParams, true)
if tparams := typeparams.Get(s); tparams != nil {
p.parameters(tparams, true)
}
if n == 1 {
p.print(blank)

18
src/go/printer/printer_test.go
View file

@ -10,6 +10,7 @@ import (
"flag"
"fmt"
"go/ast"
"go/internal/typeparams"
"go/parser"
"go/token"
"io"
@ -19,10 +20,6 @@ import (
"time"
)
// parseTypeParams tells go/parser to parse type parameters. Must be kept in
// sync with go/parser/interface.go.
const parseTypeParams parser.Mode = 1 << 30
const (
dataDir = "testdata"
tabwidth = 8
@ -47,11 +44,7 @@ const (
// if any.
func format(src []byte, mode checkMode) ([]byte, error) {
// parse src
parseMode := parser.ParseComments
if mode&allowTypeParams != 0 {
parseMode |= parseTypeParams
}
f, err := parser.ParseFile(fset, "", src, parseMode)
f, err := parser.ParseFile(fset, "", src, parser.ParseComments)
if err != nil {
return nil, fmt.Errorf("parse: %s\n%s", err, src)
}
@ -79,7 +72,7 @@ func format(src []byte, mode checkMode) ([]byte, error) {
// make sure formatted output is syntactically correct
res := buf.Bytes()
if _, err := parser.ParseFile(fset, "", res, parseTypeParams); err != nil {
if _, err := parser.ParseFile(fset, "", res, parser.ParseComments); err != nil {
return nil, fmt.Errorf("re-parse: %s\n%s", err, buf.Bytes())
}
@ -210,7 +203,7 @@ var data = []entry{
{"linebreaks.input", "linebreaks.golden", idempotent},
{"expressions.input", "expressions.golden", idempotent},
{"expressions.input", "expressions.raw", rawFormat | idempotent},
{"declarations.input", "declarations.golden", allowTypeParams},
{"declarations.input", "declarations.golden", 0},
{"statements.input", "statements.golden", 0},
{"slow.input", "slow.golden", idempotent},
{"complit.input", "complit.x", export},
@ -229,6 +222,9 @@ var data = []entry{
func TestFiles(t *testing.T) {
t.Parallel()
for _, e := range data {
if !typeparams.Enabled && e.mode&allowTypeParams != 0 {
continue
}
source := filepath.Join(dataDir, e.source)
golden := filepath.Join(dataDir, e.golden)
mode := e.mode

11
src/go/printer/testdata/declarations.golden vendored
View file

@ -942,13 +942,6 @@ type _ interface {
x ...int)
}
// properly format one-line type lists
type _ interface{ type a }
type _ interface {
type a, b, c
}
// omit superfluous parentheses in parameter lists
func _(int)
func _(int)
@ -999,10 +992,6 @@ func _(struct {
y int
}) // no extra comma between } and )
// type parameters
func _[A, B any](a A, b B) int {}
func _[T any](x, y T) T
// alias declarations
type c0 struct{}

9
src/go/printer/testdata/declarations.input vendored
View file

@ -955,11 +955,6 @@ r string,
x ...int)
}
// properly format one-line type lists
type _ interface { type a }
type _ interface { type a,b,c }
// omit superfluous parentheses in parameter lists
func _((int))
func _((((((int))))))
@ -1010,10 +1005,6 @@ func _(struct {
y int
}) // no extra comma between } and )
// type parameters
func _[A, B any](a A, b B) int {}
func _[T any](x, y T) T
// alias declarations
type c0 struct{}

10
src/go/printer/testdata/generics.golden vendored
View file

@ -4,6 +4,9 @@
package generics
func _[A, B any](a A, b B) int {}
func _[T any](x, y T) T
type T[P any] struct{}
type T[P1, P2, P3 any] struct{}
@ -31,3 +34,10 @@ func _() {
var _ []T[P]
_ = []T[P]{}
}
// properly format one-line type lists
type _ interface{ type a }
type _ interface {
type a, b, c
}

8
src/go/printer/testdata/generics.input vendored
View file

@ -4,6 +4,9 @@
package generics
func _[A, B any](a A, b B) int {}
func _[T any](x, y T) T
type T[P any] struct{}
type T[P1, P2, P3 any] struct{}
@ -28,3 +31,8 @@ func _() {
var _ []T[P]
_ = []T[P]{}
}
// properly format one-line type lists
type _ interface { type a }
type _ interface { type a,b,c }

14
src/go/types/api_test.go
View file

@ -9,6 +9,7 @@ import (
"fmt"
"go/ast"
"go/importer"
"go/internal/typeparams"
"go/parser"
"go/token"
"internal/testenv"
@ -48,8 +49,8 @@ func mustTypecheck(t *testing.T, path, source string, info *Info) string {
const genericPkg = "package generic_"
func modeForSource(src string) parser.Mode {
if strings.HasPrefix(src, genericPkg) {
return parseTypeParams
if !strings.HasPrefix(src, genericPkg) {
return typeparams.DisallowParsing
}
return 0
}
@ -347,6 +348,9 @@ func TestTypesInfo(t *testing.T) {
}
for _, test := range tests {
if strings.HasPrefix(test.src, genericPkg) && !typeparams.Enabled {
continue
}
info := Info{Types: make(map[ast.Expr]TypeAndValue)}
var name string
if strings.HasPrefix(test.src, broken) {
@ -401,6 +405,9 @@ func TestDefsInfo(t *testing.T) {
}
for _, test := range tests {
if strings.HasPrefix(test.src, genericPkg) && !typeparams.Enabled {
continue
}
info := Info{
Defs: make(map[*ast.Ident]Object),
}
@ -446,6 +453,9 @@ func TestUsesInfo(t *testing.T) {
}
for _, test := range tests {
if strings.HasPrefix(test.src, genericPkg) && !typeparams.Enabled {
continue
}
info := Info{
Uses: make(map[*ast.Ident]Object),
}

4
src/go/types/api_go1.18.go → src/go/types/api_typeparams.go
View file

@ -2,8 +2,8 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build go1.18
// +build go1.18
//go:build typeparams
// +build typeparams
package types

4
src/go/types/api_go1.18_test.go → src/go/types/api_typeparams_test.go
View file

@ -2,8 +2,8 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build go1.18
// +build go1.18
//go:build typeparams
// +build typeparams
package types_test

14
src/go/types/assignments.go
View file

@ -303,20 +303,6 @@ func (check *Checker) assignVars(lhs, origRHS []ast.Expr) {
}
}
// unpack unpacks an *ast.ListExpr into a list of ast.Expr.
// TODO(gri) Should find a more efficient solution that doesn't
// require introduction of a new slice for simple
// expressions.
func unpackExpr(x ast.Expr) []ast.Expr {
if x, _ := x.(*ast.ListExpr); x != nil {
return x.ElemList
}
if x != nil {
return []ast.Expr{x}
}
return nil
}
func (check *Checker) shortVarDecl(pos positioner, lhs, rhs []ast.Expr) {
top := len(check.delayed)
scope := check.scope

4
src/go/types/call.go
View file

@ -8,6 +8,7 @@ package types
import (
"go/ast"
"go/internal/typeparams"
"go/token"
"strings"
"unicode"
@ -16,7 +17,8 @@ import (
// funcInst type-checks a function instantiaton inst and returns the result in x.
// The operand x must be the evaluation of inst.X and its type must be a signature.
func (check *Checker) funcInst(x *operand, inst *ast.IndexExpr) {
args, ok := check.exprOrTypeList(unpackExpr(inst.Index))
exprs := typeparams.UnpackExpr(inst.Index)
args, ok := check.exprOrTypeList(exprs)
if !ok {
x.mode = invalid
x.expr = inst

11
src/go/types/check_test.go
View file

@ -30,6 +30,7 @@ import (
"fmt"
"go/ast"
"go/importer"
"go/internal/typeparams"
"go/parser"
"go/scanner"
"go/token"
@ -43,10 +44,6 @@ import (
. "go/types"
)
// parseTypeParams tells go/parser to parse type parameters. Must be kept in
// sync with go/parser/interface.go.
const parseTypeParams parser.Mode = 1 << 30
var (
haltOnError = flag.Bool("halt", false, "halt on error")
listErrors = flag.Bool("errlist", false, "list errors")
@ -213,7 +210,11 @@ func checkFiles(t *testing.T, goVersion string, filenames []string, srcs [][]byt
mode := parser.AllErrors
if strings.HasSuffix(filenames[0], ".go2") {
mode |= parseTypeParams
if !typeparams.Enabled {
t.Skip("type params are not enabled")
}
} else {
mode |= typeparams.DisallowParsing
}
// parse files and collect parser errors

7
src/go/types/decl.go
View file

@ -8,6 +8,7 @@ import (
"fmt"
"go/ast"
"go/constant"
"go/internal/typeparams"
"go/token"
)
@ -645,7 +646,7 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *ast.TypeSpec, def *Named) {
})
alias := tdecl.Assign.IsValid()
if alias && tdecl.TParams != nil {
if alias && typeparams.Get(tdecl) != nil {
// The parser will ensure this but we may still get an invalid AST.
// Complain and continue as regular type definition.
check.error(atPos(tdecl.Assign), 0, "generic type cannot be alias")
@ -668,10 +669,10 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *ast.TypeSpec, def *Named) {
def.setUnderlying(named)
obj.typ = named // make sure recursive type declarations terminate
if tdecl.TParams != nil {
if tparams := typeparams.Get(tdecl); tparams != nil {
check.openScope(tdecl, "type parameters")
defer check.closeScope()
named.tparams = check.collectTypeParams(tdecl.TParams)
named.tparams = check.collectTypeParams(tparams)
}
// determine underlying type of named

9
src/go/types/exprstring.go
View file

@ -10,6 +10,7 @@ import (
"bytes"
"fmt"
"go/ast"
"go/internal/typeparams"
)
// ExprString returns the (possibly shortened) string representation for x.
@ -69,16 +70,14 @@ func WriteExpr(buf *bytes.Buffer, x ast.Expr) {
case *ast.IndexExpr:
WriteExpr(buf, x.X)
buf.WriteByte('[')
WriteExpr(buf, x.Index)
buf.WriteByte(']')
case *ast.ListExpr:
for i, e := range x.ElemList {
exprs := typeparams.UnpackExpr(x.Index)
for i, e := range exprs {
if i > 0 {
buf.WriteString(", ")
}
WriteExpr(buf, e)
}
buf.WriteByte(']')
case *ast.SliceExpr:
WriteExpr(buf, x.X)

7
src/go/types/resolver.go
View file

@ -8,6 +8,7 @@ import (
"fmt"
"go/ast"
"go/constant"
"go/internal/typeparams"
"go/token"
"sort"
"strconv"
@ -389,8 +390,8 @@ func (check *Checker) collectObjects() {
if name == "main" {
code = _InvalidMainDecl
}
if d.decl.Type.TParams != nil {
check.softErrorf(d.decl.Type.TParams, code, "func %s must have no type parameters", name)
if tparams := typeparams.Get(d.decl.Type); tparams != nil {
check.softErrorf(tparams, code, "func %s must have no type parameters", name)
}
if t := d.decl.Type; t.Params.NumFields() != 0 || t.Results != nil {
// TODO(rFindley) Should this be a hard error?
@ -497,7 +498,7 @@ L: // unpack receiver type
if ptyp, _ := rtyp.(*ast.IndexExpr); ptyp != nil {
rtyp = ptyp.X
if unpackParams {
for _, arg := range unpackExpr(ptyp.Index) {
for _, arg := range typeparams.UnpackExpr(ptyp.Index) {
var par *ast.Ident
switch arg := arg.(type) {
case *ast.Ident:

41
src/go/types/typexpr.go
View file

@ -10,6 +10,7 @@ import (
"fmt"
"go/ast"
"go/constant"
"go/internal/typeparams"
"go/token"
"sort"
"strconv"
@ -209,27 +210,22 @@ func isubst(x ast.Expr, smap map[*ast.Ident]*ast.Ident) ast.Expr {
return &new
}
case *ast.IndexExpr:
index := isubst(n.Index, smap)
if index != n.Index {
new := *n
new.Index = index
return &new
}
case *ast.ListExpr:
var elems []ast.Expr
for i, elem := range n.ElemList {
elems := typeparams.UnpackExpr(n.Index)
var newElems []ast.Expr
for i, elem := range elems {
new := isubst(elem, smap)
if new != elem {
if elems == nil {
elems = make([]ast.Expr, len(n.ElemList))
copy(elems, n.ElemList)
if newElems == nil {
newElems = make([]ast.Expr, len(elems))
copy(newElems, elems)
}
elems[i] = new
newElems[i] = new
}
}
if elems != nil {
if newElems != nil {
index := typeparams.PackExpr(newElems)
new := *n
new.ElemList = elems
new.Index = index
return &new
}
case *ast.ParenExpr:
@ -316,13 +312,13 @@ func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast
}
}
if ftyp.TParams != nil {
sig.tparams = check.collectTypeParams(ftyp.TParams)
if tparams := typeparams.Get(ftyp); tparams != nil {
sig.tparams = check.collectTypeParams(tparams)
// Always type-check method type parameters but complain that they are not allowed.
// (A separate check is needed when type-checking interface method signatures because
// they don't have a receiver specification.)
if recvPar != nil {
check.errorf(ftyp.TParams, _Todo, "methods cannot have type parameters")
check.errorf(tparams, _Todo, "methods cannot have type parameters")
}
}
@ -467,7 +463,8 @@ func (check *Checker) typInternal(e0 ast.Expr, def *Named) (T Type) {
}
case *ast.IndexExpr:
return check.instantiatedType(e.X, unpackExpr(e.Index), def)
exprs := typeparams.UnpackExpr(e.Index)
return check.instantiatedType(e.X, exprs, def)
case *ast.ParenExpr:
// Generic types must be instantiated before they can be used in any form.
@ -801,7 +798,11 @@ func (check *Checker) interfaceType(ityp *Interface, iface *ast.InterfaceType, d
// (This extra check is needed here because interface method signatures don't have
// a receiver specification.)
if sig.tparams != nil {
check.errorf(f.Type.(*ast.FuncType).TParams, _Todo, "methods cannot have type parameters")
var at positioner = f.Type
if tparams := typeparams.Get(f.Type); tparams != nil {
at = tparams
}
check.errorf(at, _Todo, "methods cannot have type parameters")
}
// use named receiver type if available (for better error messages)