}
	if updated {
		fmt.Fprintf(os.Stderr, "go test -generate: writing new doc.go\n")
		var buf bytes.Buffer
		buf.Write(src[:fdoc.Pos()-f.FileStart])
		buf.WriteString("/*\n")
		buf.Write(new(comment.Printer).Comment(doc))
		buf.WriteString("*/")
		buf.Write(src[fdoc.End()-f.FileStart:])
		src, err := format.Source(buf.Bytes())
		if err != nil {
			t.Fatal(err)
		}

	assert(pos.IsValid())
	// Eval and CheckExpr tests may not have any source files.
	if len(check.files) == 0 {
		return nil
	}
	for _, file := range check.files {
		if file.FileStart <= pos && pos < file.FileEnd {
			return file
		}
	}
	panic(check.sprintf("file not found for pos = %d (%s)", int(pos), check.fset.Position(pos)))

	//     43  .  .  .  .  .  .  }
	//     44  .  .  .  .  .  }
	//     45  .  .  .  .  }
	//     46  .  .  .  .  Rbrace: 5:1
	//     47  .  .  .  }
	//     48  .  .  }
	//     49  .  }
	//     50  .  FileStart: 1:1
	//     51  .  FileEnd: 5:3
	//     52  .  Scope: *ast.Scope {
	//     53  .  .  Objects: map[string]*ast.Object (len = 1) {
	//     54  .  .  .  "main": *(obj @ 11)
	//     55  .  .  }
	//     56  .  }

		filenames[i] = filename
		i++
		if f.Doc != nil {
			ndocs += len(f.Doc.List) + 1 // +1 for separator
		}
		ncomments += len(f.Comments)
		ndecls += len(f.Decls)
		if i == 0 || f.FileStart < minPos {
			minPos = f.FileStart
		}
		if i == 0 || f.FileEnd > maxPos {
			maxPos = f.FileEnd
		}
	}
	slices.Sort(filenames)

	// Collect package comments from all package files into a single

	ResultOf map[*Analyzer]interface{}

	// ReadFile returns the contents of the named file.
	//
	// The only valid file names are the elements of OtherFiles
	// and IgnoredFiles, and names returned by
	// Fset.File(f.FileStart).Name() for each f in Files.
	//
	// Analyzers must use this function (if provided) instead of
	// accessing the file system directly. This allows a driver to
	// provide a virtualized file tree (including, for example,

	if err != nil {
		t.Fatal(err)
	}

	// File{Start,End} spans the entire file, not just the declarations.
	if got, want := fset.Position(f.FileStart).String(), "file.go:1:1"; got != want {
		t.Errorf("for File.FileStart, got %s, want %s", got, want)
	}
	// The end position is the newline at the end of the /* end of file */ line.

	if slicesContains(pass.OtherFiles, filename) ||
		slicesContains(pass.IgnoredFiles, filename) {
		return nil
	}
	for _, f := range pass.Files {
		// TODO(adonovan): use go1.20 f.FileStart
		if pass.Fset.File(f.Pos()).Name() == filename {
			return nil
		}
	}
	return fmt.Errorf("Pass.ReadFile: %s is not among OtherFiles, IgnoredFiles, or names of Files", filename)
}

	Doc     *CommentGroup // associated documentation; or nil
	Package token.Pos     // position of "package" keyword
	Name    *Ident        // package name
	Decls   []Decl        // top-level declarations; or nil

	FileStart, FileEnd token.Pos       // start and end of entire file
	Scope              *Scope          // package scope (this file only). Deprecated: see Object
	Imports            []*ImportSpec   // imports in this file

				decls = append(decls, p.parseDecl(declStart))
			}
		}
	}

	f := &ast.File{
		Doc:       doc,
		Package:   pos,
		Name:      ident,
		Decls:     decls,
		FileStart: token.Pos(p.file.Base()),
		FileEnd:   token.Pos(p.file.Base() + p.file.Size()),
		Imports:   p.imports,
		Comments:  p.comments,
		GoVersion: p.goVersion,
	}
	var declErr func(token.Pos, string)

		{"FieldList.Opening", Field, 0},
		{"File", Type, 0},
		{"File.Comments", Field, 0},
		{"File.Decls", Field, 0},
		{"File.Doc", Field, 0},
		{"File.FileEnd", Field, 20},
		{"File.FileStart", Field, 20},
		{"File.GoVersion", Field, 21},
		{"File.Imports", Field, 0},
		{"File.Name", Field, 0},
		{"File.Package", Field, 0},
		{"File.Scope", Field, 0},
		{"File.Unresolved", Field, 0},