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[dev.typeparams] cmd/compile/internal/syntax: type parameters must always be named

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Change-Id: Ia76ea03a3f26b13dd9bca49f7bd42101d1ff1f9e
Reviewed-on: https://go-review.googlesource.com/c/go/+/278475
Trust: Robert Griesemer <gri@golang.org>
Trust: Robert Findley <rfindley@google.com>
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 2020-12-15 21:07:47 -08:00
parent 3b5918c757
commit 7909d6ec28
3 changed files with 51 additions and 11 deletions
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6
src/cmd/compile/internal/syntax/error_test.go
View File

@ -128,6 +128,10 @@ func testSyntaxErrors(t *testing.T, filename string) {
}
defer f.Close()
var mode Mode
if strings.HasSuffix(filename, ".go2") {
mode = AllowGenerics
}
ParseFile(filename, func(err error) {
e, ok := err.(Error)
if !ok {
@ -162,7 +166,7 @@ func testSyntaxErrors(t *testing.T, filename string) {
} else {
t.Errorf("%s: unexpected error: %s", orig, e.Msg)
}
}, nil, 0)
}, nil, mode)
if *print {
fmt.Println()

34
src/cmd/compile/internal/syntax/parser.go
View File

@ -595,7 +595,7 @@ func (p *parser) typeDecl(group *Group) Decl {
p.xnest--
if name0, ok := x.(*Name); p.mode&AllowGenerics != 0 && ok && p.tok != _Rbrack {
// generic type
d.TParamList = p.paramList(name0, _Rbrack)
d.TParamList = p.paramList(name0, _Rbrack, true)
pos := p.pos()
if p.gotAssign() {
p.syntaxErrorAt(pos, "generic type cannot be alias")
@ -664,7 +664,7 @@ func (p *parser) funcDeclOrNil() *FuncDecl {
f.Pragma = p.takePragma()
if p.got(_Lparen) {
rcvr := p.paramList(nil, _Rparen)
rcvr := p.paramList(nil, _Rparen, false)
switch len(rcvr) {
case 0:
p.error("method has no receiver")
@ -688,7 +688,7 @@ func (p *parser) funcDeclOrNil() *FuncDecl {
p.syntaxError("empty type parameter list")
p.next()
} else {
f.TParamList = p.paramList(nil, _Rbrack)
f.TParamList = p.paramList(nil, _Rbrack, true)
}
}
f.Type = p.funcType()
@ -1313,7 +1313,7 @@ func (p *parser) funcType() *FuncType {
typ := new(FuncType)
typ.pos = p.pos()
p.want(_Lparen)
typ.ParamList = p.paramList(nil, _Rparen)
typ.ParamList = p.paramList(nil, _Rparen, false)
typ.ResultList = p.funcResult()
return typ
@ -1453,7 +1453,7 @@ func (p *parser) funcResult() []*Field {
}
if p.got(_Lparen) {
return p.paramList(nil, _Rparen)
return p.paramList(nil, _Rparen, false)
}
pos := p.pos()
@ -1677,7 +1677,7 @@ func (p *parser) methodDecl() *Field {
// A type argument list looks like a parameter list with only
// types. Parse a parameter list and decide afterwards.
list := p.paramList(nil, _Rbrack)
list := p.paramList(nil, _Rbrack, false)
if len(list) == 0 {
// The type parameter list is not [] but we got nothing
// due to other errors (reported by paramList). Treat
@ -1792,7 +1792,8 @@ func (p *parser) paramDeclOrNil(name *Name) *Field {
// ParameterList = ParameterDecl { "," ParameterDecl } .
// "(" or "[" has already been consumed.
// If name != nil, it is the first name after "(" or "[".
func (p *parser) paramList(name *Name, close token) (list []*Field) {
// In the result list, either all fields have a name, or no field has a name.
func (p *parser) paramList(name *Name, close token, requireNames bool) (list []*Field) {
if trace {
defer p.trace("paramList")()
}
@ -1813,7 +1814,11 @@ func (p *parser) paramList(name *Name, close token) (list []*Field) {
return false
})
// distribute parameter types
if len(list) == 0 {
return
}
// distribute parameter types (len(list) > 0)
if named == 0 {
// all unnamed => found names are named types
for _, par := range list {
@ -1822,9 +1827,12 @@ func (p *parser) paramList(name *Name, close token) (list []*Field) {
par.Name = nil
}
}
if requireNames {
p.syntaxErrorAt(list[0].Type.Pos(), "type parameters must be named")
}
} else if named != len(list) {
// some named => all must have names and types
var pos Pos // error position (or unknown)
var pos Pos // left-most error position (or unknown)
var typ Expr
for i := len(list) - 1; i >= 0; i-- {
if par := list[i]; par.Type != nil {
@ -1844,7 +1852,13 @@ func (p *parser) paramList(name *Name, close token) (list []*Field) {
}
}
if pos.IsKnown() {
p.syntaxErrorAt(pos, "mixed named and unnamed parameters")
var msg string
if requireNames {
msg = "type parameters must be named"
} else {
msg = "mixed named and unnamed parameters"
}
p.syntaxErrorAt(pos, msg)
}
}

22
src/cmd/compile/internal/syntax/testdata/tparams.go2 vendored Normal file
View File

@ -0,0 +1,22 @@
// 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.
package p
type t[ /* ERROR type parameters must be named */ a, b] struct{}
type t[a t, b t, /* ERROR type parameters must be named */ c] struct{}
type t struct {
t [n]byte
t[a]
t[a, b]
}
type t interface {
t[a]
m /* ERROR method cannot have type parameters */ [_ _, /* ERROR mixed */ _]()
t[a, b]
}
func f[ /* ERROR empty type parameter list */ ]()
func f[ /* ERROR type parameters must be named */ a, b]()
func f[a t, b t, /* ERROR type parameters must be named */ c]()