Always encode RPITITs

[spastorino]

This fixes tests/ui/impl-trait/in-trait/foreign.rs because RPITIT's def_id on the trait side were not being encoded in some cases.

The only meaningful commit is d948d77
This is placed on top of #109277 but I'm not sure if that's needed, anyway #109277 is next in the queue.

r? @compiler-errors

[spastorino]

I've also blessed a test that was a known bug and it's now working with the refactor.

[compiler-errors]

I am skeptical that this PR passes... I'll look into it though.

[compiler-errors]

Sorry, skeptical why this PR passes.

[compiler-errors]

Oh... this fails because we have no predicates_of for RPITITs. That doesn't seem right 🤔

Let's leave this as not updated currently?

[compiler-errors]

I don't think this needs to be on top of #109277

[compiler-errors]

Sorry, skeptical why this PR passes.

[compiler-errors]

ok I looked into it -- we don't need revisions here. We "inherit" the revisions from the parent. But it does inherit the revisions from the parent, so no extra file needed like in my other PR. Let me fix that.

Suggested change

// revisions: current next

[spastorino]

we probably want the compile-flags anyway, I'd say.

[spastorino]

In any case, feel free to close this PR and leave yours open that aggregates this stuff.

[compiler-errors]

Yes, the compile-flags is necessary to enable the -Z flag when [next], but re-declaring "// revisions" here does nothing, because the revisions is coming from the actual UI test (foreign.rs)

[rust-log-analyzer]

The job mingw-check failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

    Checking rustc_query_impl v0.0.0 (/checkout/compiler/rustc_query_impl)
    Checking rustc_ast_lowering v0.0.0 (/checkout/compiler/rustc_ast_lowering)
    Checking rustc_monomorphize v0.0.0 (/checkout/compiler/rustc_monomorphize)
    Checking rustc_smir v0.0.0 (/checkout/compiler/rustc_smir)
error[E0317]: `if` may be missing an `else` clause
    --> compiler/rustc_metadata/src/rmeta/encoder.rs:1049:21
     |
1049 | /                     if tcx.opt_rpitit_info(def_id.to_def_id()).is_some() {
     | |                         ---- found here
1051 | |                     }
     | |_____________________^ expected `bool`, found `()`
     |
     |
     = note: `if` expressions without `else` evaluate to `()`
     = help: consider adding an `else` block that evaluates to the expected type
For more information about this error, try `rustc --explain E0317`.
error: could not compile `rustc_metadata` due to previous error
warning: build failed, waiting for other jobs to finish...
error: could not compile `rustc_metadata` due to previous error