@FormatFor annotation

This is a feature request to create a @FormatFor annotation to complement @FormatMethod

Here is code in Daikon that could use it:

  private static void decl_error(
      ParseState state, Throwable cause, String format, @Nullable Object... args) {
    @SuppressWarnings(
        "formatter:format.string.invalid") // need a @FormatFor annotation
    String msg = String.format(format, args) + state.line_file_message();
    throw new Daikon.UserError(cause, msg);
  }

The @FormatFor annotation also enables the body of methods annotated as @FormatMethod to be type-checked.

Quoting from #1507:

Note a difference in the design of the Formatter and I18nFormatter type systems.

• Formatter has @FormatMethod, which is more concise and easier to read and write.
• I18nFormatter has @I18nFormatFor.

At one point, the Formatter type system had @FormatFor, but I recall that it was removed in favor of @FormatMethod. It seems that @FormatFor is needed as well; the type-checker could add it in the appropriate place whenever the user has written @FormatMethod. An alternative would be to check, within method m, whether the arguments to a format method are formal parameters of m and m is annotated as @FormatMethod. This would not take advantage of the dataflow framework, however.

Start with the @FormatMethod and proposed @FormatFor designs in this issue, then read the referenced discussion in #1507. Determine how the Formatter type system should represent the relationship and how the type-checker should apply it; the work is done when the annotation and its intended checking behavior are supported.