Auto merge of #74330 - Manishearth:rollup-mrc09pb, r=Manishearth

Rollup of 15 pull requests

Successful merges:

 - #71237 (Add Ayu theme to rustdoc)
 - #73720 (Clean up E0704 error explanation)
 - #73866 (Obviate #[allow(improper_ctypes_definitions)])
 - #73965 (typeck: check for infer before type impls trait)
 - #73986 (add (unchecked) indexing methods to raw (and NonNull) slices)
 - #74173 (Detect tuple struct incorrectly used as struct pat)
 - #74220 (Refactor Windows `parse_prefix`)
 - #74227 (Remove an unwrap in layout computation)
 - #74239 (Update llvm-project to latest origin/rustc/10.0-2020-05-05 commit )
 - #74257 (don't mark linux kernel module targets as a unix environment)
 - #74270 (typeck: report placeholder type error w/out span)
 - #74296 (Clarify the description for rfind)
 - #74310 (Use `ArrayVec` in `SparseBitSet`.)
 - #74316 (Remove unnecessary type hints from Wake internals)
 - #74324 (Update Clippy)

Failed merges:

r? @ghost