Improving usability of having many nearly-identical methods

[Vorpal]

@kornel

rustc could be taught that methods are related, and that some errors can be fixed by using a more appropriate method (e.g. instead of complaining about passing a closure where a primitive type was expected, say it should be calling a _by/_with method instead).

This seems like a worthwhile diagnostics attribute. Perhaps you could list related methods, and rustc would check if any of them would type check and if so suggest switching to it? (I don't know nearly enough about the internals to determine if that I'd even feasible.)