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Diffstat (limited to '')
| -rw-r--r-- | src/go/ast/resolve.go | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/src/go/ast/resolve.go b/src/go/ast/resolve.go new file mode 100644 index 0000000..c1830b5 --- /dev/null +++ b/src/go/ast/resolve.go @@ -0,0 +1,174 @@ +// 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() +} |