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cmd/compile: revert user-visible changes related to aliases

Browse source 
Reason: Decision to back out current alias implementation.

Leaving import/export related code in place for now.

For #16339.

TBR=mdempsky

Change-Id: Ib0897cab2c1c3dc8a541f2efb9893271b0b0efe2
Reviewed-on: https://go-review.googlesource.com/32757
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Robert Griesemer 2016-11-04 15:48:39 -07:00
parent dd1e7b3be0
commit 8e970536df
7 changed files with 1 additions and 410 deletions
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97
src/cmd/compile/internal/gc/noder.go
View file

@ -61,9 +61,6 @@ func (p *noder) decls(decls []syntax.Decl) (l []*Node) {
case *syntax.ImportDecl:
p.importDecl(decl)
case *syntax.AliasDecl:
p.aliasDecl(decl)
case *syntax.VarDecl:
l = append(l, p.varDecl(decl)...)
@ -150,100 +147,6 @@ func (p *noder) importDecl(imp *syntax.ImportDecl) {
my.Block = 1 // at top level
}
func (p *noder) aliasDecl(decl *syntax.AliasDecl) {
// Because alias declarations must refer to imported entities
// which are already set up, we can do all checks right here.
// We won't know anything about entities that have not been
// declared yet, but since they cannot have been imported, we
// know there's an error and we don't care about the details.
// The original entity must be denoted by a qualified identifier.
// (The parser doesn't make this restriction to be more error-
// tolerant.)
qident, ok := decl.Orig.(*syntax.SelectorExpr)
if !ok {
// TODO(gri) This prints a dot-imported object with qualification
// (confusing error). Fix this.
yyerror("invalid alias: %v is not a package-qualified identifier", p.expr(decl.Orig))
return
}
pkg := p.expr(qident.X)
if pkg.Op != OPACK {
yyerror("invalid alias: %v is not a package", pkg)
return
}
pkg.Used = true
// Resolve original entity
orig := oldname(restrictlookup(qident.Sel.Value, pkg.Name.Pkg))
if orig.Sym.Flags&SymAlias != 0 {
Fatalf("original %v marked as alias", orig.Sym)
}
// An alias declaration must not refer to package unsafe.
if orig.Sym.Pkg == unsafepkg {
yyerror("invalid alias: %v refers to package unsafe (%v)", decl.Name.Value, orig)
return
}
// The aliased entity must be from a matching constant, type, variable,
// or function declaration, respectively.
var what string
switch decl.Tok {
case syntax.Const:
if orig.Op != OLITERAL {
what = "constant"
}
case syntax.Type:
if orig.Op != OTYPE {
what = "type"
}
case syntax.Var:
if orig.Op != ONAME || orig.Class != PEXTERN {
what = "variable"
}
case syntax.Func:
if orig.Op != ONAME || orig.Class != PFUNC {
what = "function"
}
default:
Fatalf("unexpected token: %s", decl.Tok)
}
if what != "" {
yyerror("invalid alias: %v is not a %s", orig, what)
return
}
// handle special cases
switch decl.Name.Value {
case "_":
return // don't declare blank aliases
case "init":
yyerror("cannot declare init - must be non-alias function declaration")
return
}
// declare alias
// (this is similar to handling dot imports)
asym := p.name(decl.Name)
if asym.Def != nil {
redeclare(asym, "in alias declaration")
return
}
asym.Flags |= SymAlias
asym.Def = orig
asym.Block = block
asym.Lastlineno = lineno
if exportname(asym.Name) {
// TODO(gri) newname(asym) is only needed to satisfy exportsym
// (and indirectly, exportlist). We should be able to just
// collect the Syms, eventually.
exportsym(newname(asym))
}
}
func (p *noder) varDecl(decl *syntax.VarDecl) []*Node {
names := p.declNames(decl.NameList)

23
src/go/internal/gcimporter/testdata/exports.go vendored
View file

@ -7,11 +7,7 @@
package exports
import (
"go/ast"
"go/build"
"math"
)
import "go/ast"
// Issue 3682: Correctly read dotted identifiers from export data.
const init1 = 0
@ -29,10 +25,6 @@ const (
C7 = `bar\n`
)
const (
C8 => math.Pi
)
type (
T1 int
T2 [10]int
@ -81,21 +73,12 @@ type (
T28 func(T28) T28
)
type (
T29 => ast.File
T30 => build.Context
)
var (
V0 int
V1 = -991.0
V2 float32 = 1.2
)
var (
V3 => build.Default
)
func F1() {}
func F2(x int) {}
func F3() int { return 0 }
@ -103,7 +86,3 @@ func F4() float32 { return 0 }
func F5(a, b, c int, u, v, w struct{ x, y T1 }, more ...interface{}) (p, q, r chan<- T10)
func (p *T1) M1()
func F6 => math.Sin
func F7 => ast.IsExported
func F8 => build.Import

103
test/alias2.go
View file

@ -1,103 +0,0 @@
// errorcheck
// Copyright 2016 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.
// Test basic restrictions on alias declarations.
package p
import (
"flag"
"fmt" // use at most once (to test "imported but not used" error)
"go/build"
. "go/build"
"io"
"math"
"unsafe"
)
// helper
var before struct {
f
}
// aliases must refer to package-qualified identifiers
// TODO(gri) should only see one error for declaration below - fix this
const _ => 0 // ERROR "unexpected literal 0|_ is not a package-qualified identifier"
type _ => _ // ERROR "_ is not a package-qualified identifier"
type t => _ // ERROR "_ is not a package-qualified identifier"
const _ => iota // ERROR "iota is not a package-qualified identifier"
type _ => int // ERROR "int is not a package-qualified identifier"
const c => iota // ERROR "iota is not a package-qualified identifier"
type t => int // ERROR "int is not a package-qualified identifier"
// dot-imported identifiers are not qualified identifiers
// TODO(gri) fix error printing - should not print a qualified identifier...
var _ => Default // ERROR "build\.Default is not a package-qualified identifier"
// qualified identifiers must start with a package
var _ => before.f // ERROR "before is not a package"
func _ => before.f // ERROR "before is not a package"
var _ => after.m // ERROR "after is not a package"
func _ => after.m // ERROR "after is not a package"
var v => before.f // ERROR "before is not a package"
func f => before.f // ERROR "before is not a package"
var v => after.m // ERROR "after is not a package"
func f => after.m // ERROR "after is not a package"
// TODO(gri) fix error printing - should print correct qualified identifier...
var _ => Default.ARCH // ERROR "build.Default is not a package"
// aliases may not refer to package unsafe
type ptr => unsafe.Pointer // ERROR "ptr refers to package unsafe"
func size => unsafe.Sizeof // ERROR "size refers to package unsafe"
// aliases must refer to entities of the same kind
const _ => math.Pi
const pi => math.Pi
const pi1 => math.Sin // ERROR "math.Sin is not a constant"
type _ => io.Writer
type writer => io.Writer
type writer1 => math.Sin // ERROR "math.Sin is not a type"
var _ => build.Default
var def => build.Default
var def1 => build.Import // ERROR "build.Import is not a variable"
func _ => math.Sin
func sin => math.Sin
func sin1 => math.Pi // ERROR "math.Pi is not a function"
// aliases may not be called init
func init => flag.Parse // ERROR "cannot declare init"
// alias reference to a package marks package as used
func _ => fmt.Println
// re-exported aliases
const Pi => math.Pi
type Writer => io.Writer
var Def => build.Default
func Sin => math.Sin
// type aliases denote identical types
type myPackage => build.Package
var pkg myPackage
var _ build.Package = pkg // valid assignment
var _ *build.Package = &pkg // valid assignment
// helper
type after struct{}
func (after) m() {}

54
test/alias3.dir/a.go
View file

@ -1,54 +0,0 @@
// Copyright 2016 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 a
import (
"bytes"
"go/build"
"io"
"math"
)
func F(c *build.Context, w io.Writer) {}
func Inlined() bool { var w Writer; return w == nil }
func Check() {
if Pi != math.Pi {
panic(0)
}
var w Writer
F(new(Context), w)
F(new(build.Context), bytes.NewBuffer(nil))
if &Default != &build.Default {
panic(1)
}
if Sin(1) != math.Sin(1) {
panic(2)
}
var _ *LimitedReader = new(LimitedReader2)
}
// export aliases
const Pi => math.Pi
type (
Context => build.Context // not an interface
Writer => io.Writer // interface
)
// different aliases may refer to the same original
type LimitedReader => io.LimitedReader
type LimitedReader2 => io.LimitedReader
var Default => build.Default
var Default2 => build.Default
func Sin => math.Sin
func Sin2 => math.Sin

61
test/alias3.dir/b.go
View file

@ -1,61 +0,0 @@
// Copyright 2016 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 b
import (
"./a"
"bytes"
"go/build"
"io"
"math"
)
func F => a.F
func Inlined => a.Inlined
var _ func(*Context, io.Writer) = a.F
// check aliases
func Check() {
if Pi != math.Pi {
panic(0)
}
var w Writer
a.F(new(Context), w)
F(new(build.Context), bytes.NewBuffer(nil))
if !Inlined() {
panic(1)
}
if &Default != &build.Default {
panic(2)
}
if Sin(1) != math.Sin(1) {
panic(3)
}
var _ *LimitedReader = new(LimitedReader2)
}
// re-export aliases
const Pi => a.Pi
type (
Context => a.Context // not an interface
Writer => a.Writer // interface
)
// different aliases may refer to the same original
type LimitedReader => a.LimitedReader
type LimitedReader2 => a.LimitedReader2
var Default => a.Default
var Default2 => a.Default2
func Sin => a.Sin
func Sin2 => a.Sin

66
test/alias3.dir/c.go
View file

@ -1,66 +0,0 @@
// Copyright 2016 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 main
import (
"./a"
"./b"
"bytes"
"go/build"
"math"
)
func f => b.F
func inlined => b.Inlined
var _ func(*context, a.Writer) = f
func Check() {
if pi != math.Pi {
panic(0)
}
var w writer
b.F(new(context), w)
f(new(build.Context), bytes.NewBuffer(nil))
if !inlined() {
panic(1)
}
if &default_ != &build.Default {
panic(2)
}
if sin(1) != math.Sin(1) {
panic(3)
}
var _ *limitedReader = new(limitedReader2)
}
// local aliases
const pi => b.Pi
type (
context => b.Context // not an interface
writer => b.Writer // interface
)
// different aliases may refer to the same original
type limitedReader => b.LimitedReader
type limitedReader2 => b.LimitedReader2
var default_ => b.Default
var default2 => b.Default2
func sin => b.Sin
func sin2 => b.Sin
func main() {
a.Check()
b.Check()
Check()
}

7
test/alias3.go
View file

@ -1,7 +0,0 @@
// rundir
// Copyright 2016 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 ignored