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go/gcimporter15: implement support for importing aliases 

- backport of changes made to std lib:
  https://go-review.googlesource.com/32350/
  https://go-review.googlesource.com/32538

- factored out newAlias for non-Go1.8 builds

- tested against 1.6, 1.7, 1.8

Change-Id: I538b2d4a0f0c93c517a7aaa3b1562aa3afd154dd
Reviewed-on: https://go-review.googlesource.com/32470
Reviewed-by: Alan Donovan <adonovan@google.com>
This commit is contained in:
Robert Griesemer 2016-10-31 14:54:29 -07:00
parent 4549178751
commit 5b3db00587
3 changed files with 100 additions and 27 deletions
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99
go/gcimporter15/bimport.go
View File

@ -27,7 +27,7 @@ type importer struct {
data []byte
path string
buf []byte // for reading strings
version int
version int // export format version
// object lists
strList []string // in order of appearance
@ -106,13 +106,6 @@ func BImportData(fset *token.FileSet, imports map[string]*types.Package, data []
// ...
// fallthrough
case 3, 2, 1:
// Support for Go 1.8 type aliases will be added very
// soon (Oct 2016). In the meantime, we make a
// best-effort attempt to read v3 export data, failing
// if we encounter a type alias. This allows the
// automated builders to make progress since
// type aliases are not yet used in practice.
// TODO(gri): add support for type aliases.
p.debugFormat = p.rawStringln(p.rawByte()) == "debug"
p.trackAllTypes = p.int() != 0
p.posInfoFormat = p.int() != 0
@ -193,7 +186,7 @@ func (p *importer) pkg() *types.Package {
// we should never see an empty package name
if name == "" {
panic("empty package name in import")
errorf("empty package name in import")
}
// an empty path denotes the package we are currently importing;
@ -218,37 +211,81 @@ func (p *importer) pkg() *types.Package {
return pkg
}
func (p *importer) declare(obj types.Object) {
// objTag returns the tag value for each object kind.
// obj must not be a *types.Alias.
func objTag(obj types.Object) int {
switch obj.(type) {
case *types.Const:
return constTag
case *types.TypeName:
return typeTag
case *types.Var:
return varTag
case *types.Func:
return funcTag
// Aliases are not exported multiple times, thus we should not see them here.
default:
errorf("unexpected object: %v (%T)", obj, obj)
panic("unreachable")
}
}
func sameObj(a, b types.Object) bool {
// Because unnamed types are not canonicalized, we cannot simply compare types for
// (pointer) identity.
// Ideally we'd check equality of constant values as well, but this is good enough.
return objTag(a) == objTag(b) && types.Identical(a.Type(), b.Type())
}
func (p *importer) declare(obj types.Object) types.Object {
pkg := obj.Pkg()
if alt := pkg.Scope().Insert(obj); alt != nil {
// This could only trigger if we import a (non-type) object a second time.
// This should never happen because 1) we only import a package once; and
// b) we ignore compiler-specific export data which may contain functions
// whose inlined function bodies refer to other functions that were already
// imported.
// (See also the comment in cmd/compile/internal/gc/bimport.go importer.obj,
// switch case importing functions).
errorf("inconsistent import:\n\t%v\npreviously imported as:\n\t%v\n", alt, obj)
// This can only trigger if we import a (non-type) object a second time.
// Excluding aliases, this cannot happen because 1) we only import a package
// once; and b) we ignore compiler-specific export data which may contain
// functions whose inlined function bodies refer to other functions that
// were already imported.
// However, if a package exports multiple aliases referring to the same
// original object, that object is currently exported multiple times.
// Check for that specific case and accept it if the aliases correspond
// (see also the comment in cmd/compile/internal/gc/bimport.go, method
// importer.obj, switch case importing functions).
// Note that the original itself cannot be an alias.
// TODO(gri) We can avoid doing this once objects are exported only once
// per package again (issue #17636).
if !sameObj(obj, alt) {
errorf("inconsistent import:\n\t%v\npreviously imported as:\n\t%v\n", alt, obj)
}
obj = alt // use object that was imported first
}
return obj
}
func (p *importer) obj(tag int) {
var aliasPos token.Pos
var aliasName string
if tag == aliasTag {
aliasPos = p.pos()
aliasName = p.string()
tag = p.tagOrIndex()
}
var obj types.Object
switch tag {
case constTag:
pos := p.pos()
pkg, name := p.qualifiedName()
typ := p.typ(nil)
val := p.value()
p.declare(types.NewConst(pos, pkg, name, typ, val))
obj = p.declare(types.NewConst(pos, pkg, name, typ, val))
case typeTag:
_ = p.typ(nil)
obj = p.typ(nil).(*types.Named).Obj()
case varTag:
pos := p.pos()
pkg, name := p.qualifiedName()
typ := p.typ(nil)
p.declare(types.NewVar(pos, pkg, name, typ))
obj = p.declare(types.NewVar(pos, pkg, name, typ))
case funcTag:
pos := p.pos()
@ -256,11 +293,15 @@ func (p *importer) obj(tag int) {
params, isddd := p.paramList()
result, _ := p.paramList()
sig := types.NewSignature(nil, params, result, isddd)
p.declare(types.NewFunc(pos, pkg, name, sig))
obj = p.declare(types.NewFunc(pos, pkg, name, sig))
default:
errorf("unexpected object tag %d", tag)
}
if aliasName != "" {
p.declare(newAlias(aliasPos, p.pkgList[0], aliasName, obj))
}
}
func (p *importer) pos() token.Pos {
@ -469,7 +510,7 @@ func (p *importer) typ(parent *types.Package) types.Type {
// no embedded interfaces with gc compiler
if p.int() != 0 {
panic("unexpected embedded interface")
errorf("unexpected embedded interface")
}
t := types.NewInterface(p.methodList(parent), nil)
@ -544,7 +585,7 @@ func (p *importer) field(parent *types.Package) *types.Var {
case *types.Named:
name = typ.Obj().Name()
default:
panic("anonymous field expected")
errorf("anonymous field expected")
}
anonymous = true
}
@ -623,7 +664,7 @@ func (p *importer) param(named bool) (*types.Var, bool) {
if named {
name = p.string()
if name == "" {
panic("expected named parameter")
errorf("expected named parameter")
}
if name != "_" {
pkg = p.pkg()
@ -727,7 +768,7 @@ func (p *importer) tagOrIndex() int {
func (p *importer) int() int {
x := p.int64()
if int64(int(x)) != x {
panic("exported integer too large")
errorf("exported integer too large")
}
return int(x)
}
@ -814,7 +855,7 @@ func (p *importer) rawByte() byte {
case '|':
// nothing to do
default:
panic("unexpected escape sequence in export data")
errorf("unexpected escape sequence in export data")
}
}
p.data = p.data[r:]
@ -856,7 +897,11 @@ const (
fractionTag // not used by gc
complexTag
stringTag
nilTag // only used by gc (appears in exported inlined function bodies)
unknownTag // not used by gc (only appears in packages with errors)
// Aliases
aliasTag
)
var predeclared = []types.Type{

17
go/gcimporter15/newalias16.go Normal file
View File

@ -0,0 +1,17 @@
// 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.
// +build go1.6,!go1.8
package gcimporter
import (
"go/token"
"go/types"
)
func newAlias(pos token.Pos, pkg *types.Package, name string, orig types.Object) types.Object {
errorf("unexpected alias in non-Go1.8 export data: %s.%s => %v", pkg.Name(), name, orig)
panic("unreachable")
}

11
go/gcimporter15/newalias18.go Normal file
View File

@ -0,0 +1,11 @@
// 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.
// +build go1.8
package gcimporter
import "go/types"
func newAlias => types.NewAlias