Multiple params in the same param list with the same name are accepted

[ben0x539]

Both type and value parameters. This compiles just fine, short of the unused-variable warnings:

fn f<T, T>(t: T, t: T) {}

That seems like a fairly useless feature, I imagine people would only ever do this by accident and then get fairly confused about why the "wrong" parameter is being used, if they somehow don't run into type errors. So I am posting this here in the hope it is a bug and not something that needs an RFC to be fixed.

This is half a duplicate of #15969 but not a duplicate of the issue that is a duplicate of, imo.

[huonw]

Nominating; looks like a back-compat issue.

[pnkfelix]

P-backcompat-lang, 1.0.