Remove old #[allow(trivial_casts)] annotations

[alexcrichton]

These were added a long time ago but we long since switched the lint back to
allow-by-default, so these annotations shouldn't be necessary.

[rust-highfive]

r? @brson

(rust_highfive has picked a reviewer for you, use r? to override)

[alexcrichton]

r? @nrc

[nrc]

Can you leave the FIXMEs in please? I believe they are still valid. r+ with that.

[alexcrichton]

Hm, would the FIXME still make sense without a #![allow] there? It seems odd to be annotating as casts with FIXMEs when it's the only way to do so no?

[nrc]

The point is once we support coercion in type ascription, then we replace the as with type ascription, i.e., it is the only way now, but in the future it won't be.

[alexcrichton]

Right but this means the code looks like:

     fn fmt(&self, f: &mut Formatter) -> Result {
        // FIXME(#23542) Replace with type ascription.
        Pointer::fmt(&(*self as *const T), f)
    } 

which seems odd because we're not necessarily stylistically attempting to annotate all as casts with a FIXME (there are likely quite a few throughout core/std). Once type ascription is landed we can in theory turn back on the lint to catch cases like this, right?

[nrc]

Yeah, I guess so.

[nrc]

@bors: r+

[bors]

📌 Commit 696a1da has been approved by nrc

[bors]

⌛ Testing commit 696a1da with merge 0d410b8...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-mac-ios-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-opt