if bp.PkgObj == "" {
			if bp.Goroot && bp.Dir != "" {
				filename, err = lookupGorootExport(bp.Dir)
				if err == nil {
					_, err = os.Stat(filename)
				}
				if err == nil {
					return filename, bp.ImportPath, nil
				}
			}
			goto notfound
		} else {
			noext = strings.TrimSuffix(bp.PkgObj, ".a")
		}
		id = bp.ImportPath

		return nil, fmt.Errorf("empty path")
	}

	var pkgobj, suffix string
	if dot := strings.IndexByte(pathstr, opType); dot < 0 {
		pkgobj = pathstr
	} else {
		pkgobj = pathstr[:dot]
		suffix = pathstr[dot:] // suffix starts with "."
	}

	obj := pkg.Scope().Lookup(pkgobj)
	if obj == nil {
		return nil, fmt.Errorf("package %s does not contain %q", pkg.Path(), pkgobj)
	}

				p.ImportPath = filepath.Join(modprefix, p.ImportPath)
			}

			// Set GOROOT-specific fields (sometimes for modules in a GOPATH directory).
			// The fields set below (SrcRoot, PkgRoot, BinDir, PkgTargetRoot, and PkgObj)
			// are only set in build.Import if p.Root != "".
			var pkgtargetroot string
			suffix := ""
			if ctxt.InstallSuffix != "" {
				suffix = "_" + ctxt.InstallSuffix
			}
			switch ctxt.Compiler {

	if pp.PkgTargetRoot != "" && cfg.BuildPkgdir != "" {
		old := pp.PkgTargetRoot
		pp.PkgRoot = cfg.BuildPkgdir
		pp.PkgTargetRoot = cfg.BuildPkgdir
		if pp.PkgObj != "" {
			pp.PkgObj = filepath.Join(cfg.BuildPkgdir, strings.TrimPrefix(pp.PkgObj, old))
		}
	}

	p.Dir = pp.Dir
	p.ImportPath = pp.ImportPath
	p.ImportComment = pp.ImportComment
	p.Name = pp.Name
	p.Doc = pp.Doc
	p.Root = pp.Root

	PkgTargetRoot string   // architecture dependent install root directory ("" if unknown)
	BinDir        string   // command install directory ("" if unknown)
	Goroot        bool     // package found in Go root
	PkgObj        string   // installed .a file
	AllTags       []string // tags that can influence file selection in this directory
	ConflictDir   string   // this directory shadows Dir in $GOPATH

			case p.Name != "main" && p.Module != nil:
				// Non-executables have no target (except the cache) when building with modules.
			case p.Name != "main" && p.Standard && p.Internal.Build.PkgObj == "":
				// Most packages in std do not need an installed .a, because they can be
				// rebuilt and used directly from the build cache.
				// A few targets (notably those using cgo) still do need to be installed

		{"Package.ImportPos", Field, 0},
		{"Package.Imports", Field, 0},
		{"Package.InvalidGoFiles", Field, 6},
		{"Package.MFiles", Field, 3},
		{"Package.Name", Field, 0},
		{"Package.PkgObj", Field, 0},
		{"Package.PkgRoot", Field, 0},
		{"Package.PkgTargetRoot", Field, 5},
		{"Package.Root", Field, 0},
		{"Package.SFiles", Field, 0},
		{"Package.SrcRoot", Field, 0},

pkg go/build, type Package struct, ImportPos map[string][]token.Position
pkg go/build, type Package struct, Imports []string
pkg go/build, type Package struct, Name string
pkg go/build, type Package struct, PkgObj string
pkg go/build, type Package struct, PkgRoot string
pkg go/build, type Package struct, Root string
pkg go/build, type Package struct, SFiles []string
pkg go/build, type Package struct, SrcRoot string