}
	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  .  }

	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,