`simplify_type` was bogus, as there was no way for it to handle enums
properly. It was also slow, because it created many Rust types at runtime. In
general creating Rust types during trans is a source of slowness, and I'd like
to avoid doing it as much as possible. (It is probably not possible to
eliminate it entirely, due to `subst`, but we should get rid of as much of it
as we can.) So this patch replaces `simplify_type` with `sizing_type_of`,
which creates a size-equivalent LLVM type directly without going through a
Rust type first.
Because this is causing an ICE in Servo, I'm rubber stamping it.
"Dual impls" are impls that are both type implementations and trait
implementations. They can lead to ambiguity and so this patch removes them
from the language.
This also enforces coherence rules. Without this patch, records can implement
traits not defined in the current crate. This patch fixes this, and updates
all of rustc to adhere to the new enforcement. Most of this patch is fixing
rustc to obey the coherence rules, which involves converting a bunch of records
to structs.
and rename "class" to "struct" everywhere possible (except local
vars, I was too lazy for that) -- that is why this commit is so
big.
No review, just dead code removal and renaming.
Closes#3515
