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// Copyright 2011 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 implements NewPackage.
package ast
import (
"fmt"
"go/scanner"
"go/token"
"strconv"
)
type pkgBuilder struct {
fset *token.FileSet
errors scanner.ErrorList
}
func (p *pkgBuilder) error(pos token.Pos, msg string) {
p.errors.Add(p.fset.Position(pos), msg)
}
func (p *pkgBuilder) errorf(pos token.Pos, format string, args ...interface{}) {
p.error(pos, fmt.Sprintf(format, args...))
}
func (p *pkgBuilder) declare(scope, altScope *Scope, obj *Object) {
alt := scope.Insert(obj)
if alt == nil && altScope != nil {
// see if there is a conflicting declaration in altScope
alt = altScope.Lookup(obj.Name)
}
if alt != nil {
prevDecl := ""
if pos := alt.Pos(); pos.IsValid() {
prevDecl = fmt.Sprintf("\n\tprevious declaration at %s", p.fset.Position(pos))
}
p.error(obj.Pos(), fmt.Sprintf("%s redeclared in this block%s", obj.Name, prevDecl))
}
}
func resolve(scope *Scope, ident *Ident) bool {
for ; scope != nil; scope = scope.Outer {
if obj := scope.Lookup(ident.Name); obj != nil {
ident.Obj = obj
return true
}
}
return false
}
// An Importer resolves import paths to package Objects.
// The imports map records the packages already imported,
// indexed by package id (canonical import path).
// An Importer must determine the canonical import path and
// check the map to see if it is already present in the imports map.
// If so, the Importer can return the map entry. Otherwise, the
// Importer should load the package data for the given path into
// a new *Object (pkg), record pkg in the imports map, and then
// return pkg.
type Importer func(imports map[string]*Object, path string) (pkg *Object, err error)
// NewPackage creates a new Package node from a set of File nodes. It resolves
// unresolved identifiers across files and updates each file's Unresolved list
// accordingly. If a non-nil importer and universe scope are provided, they are
// used to resolve identifiers not declared in any of the package files. Any
// remaining unresolved identifiers are reported as undeclared. If the files
// belong to different packages, one package name is selected and files with
// different package names are reported and then ignored.
// The result is a package node and a scanner.ErrorList if there were errors.
//
func NewPackage(fset *token.FileSet, files map[string]*File, importer Importer, universe *Scope) (*Package, error) {
var p pkgBuilder
p.fset = fset
// complete package scope
pkgName := ""
pkgScope := NewScope(universe)
for _, file := range files {
// package names must match
switch name := file.Name.Name; {
case pkgName == "":
pkgName = name
case name != pkgName:
p.errorf(file.Package, "package %s; expected %s", name, pkgName)
continue // ignore this file
}
// collect top-level file objects in package scope
for _, obj := range file.Scope.Objects {
p.declare(pkgScope, nil, obj)
}
}
// package global mapping of imported package ids to package objects
imports := make(map[string]*Object)
// complete file scopes with imports and resolve identifiers
for _, file := range files {
// ignore file if it belongs to a different package
// (error has already been reported)
if file.Name.Name != pkgName {
continue
}
// build file scope by processing all imports
importErrors := false
fileScope := NewScope(pkgScope)
for _, spec := range file.Imports {
if importer == nil {
importErrors = true
continue
}
path, _ := strconv.Unquote(spec.Path.Value)
pkg, err := importer(imports, path)
if err != nil {
p.errorf(spec.Path.Pos(), "could not import %s (%s)", path, err)
importErrors = true
continue
}
// TODO(gri) If a local package name != "." is provided,
// global identifier resolution could proceed even if the
// import failed. Consider adjusting the logic here a bit.
// local name overrides imported package name
name := pkg.Name
if spec.Name != nil {
name = spec.Name.Name
}
// add import to file scope
if name == "." {
// merge imported scope with file scope
for _, obj := range pkg.Data.(*Scope).Objects {
p.declare(fileScope, pkgScope, obj)
}
} else if name != "_" {
// declare imported package object in file scope
// (do not re-use pkg in the file scope but create
// a new object instead; the Decl field is different
// for different files)
obj := NewObj(Pkg, name)
obj.Decl = spec
obj.Data = pkg.Data
p.declare(fileScope, pkgScope, obj)
}
}
// resolve identifiers
if importErrors {
// don't use the universe scope without correct imports
// (objects in the universe may be shadowed by imports;
// with missing imports, identifiers might get resolved
// incorrectly to universe objects)
pkgScope.Outer = nil
}
i := 0
for _, ident := range file.Unresolved {
if !resolve(fileScope, ident) {
p.errorf(ident.Pos(), "undeclared name: %s", ident.Name)
file.Unresolved[i] = ident
i++
}
}
file.Unresolved = file.Unresolved[0:i]
pkgScope.Outer = universe // reset universe scope
}
p.errors.Sort()
return &Package{pkgName, pkgScope, imports, files}, p.errors.Err()
}
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