Forbid recursive impl trait
There is no type T, such that `T = [T; 2]`, but impl Trait could sometimes
be to circumvented this.
This patch makes it a hard error for an opaque type to resolve to such a
"type". Before this can be merged it needs
- [x] A better error message - it's good enough for now.
- [x] A crater run (?) to see if this any real-world code
closes#47659
Allow to dispatch fn traits depending on number of parameters
Hello,
By following @eddyb's advise on issue #45510, I managed to have the snippets of code in #45510 and #18952 passing without breaking older diagnostics.
EDIT: the codegen tests breakage I experienced is due to the poor quality of my laptop.
If any kind reviewer has any advice, you are very welcome.
In #56986 the linkage of jemalloc to the compiler was switched from the
driver library to the rustc binary to ensure that only rustc itself uses
jemalloc. In doing so, however, it turns out jemalloc wasn't actually
linked in at all! None of the symbols were referenced so the static
library wasn't used. This means that jemalloc wasn't pulled in at all.
This commit performs a bit of a dance to reference jemalloc symbols,
attempting to pull it in despite LLVM's optimizations.
Closes#57115
Universes
This PR transitions the compiler to use **universes** instead of the **leak-check**. It is marked as [WIP] for a few reasons:
- The diagnostics at present are terrible =)
- This changes the behavior of coherence, regressing some things that used to compile
The goals of this PR at present are:
- To start getting some eyes on the code
- To do a crater run
- To see the full travis results (due to https://github.com/rust-lang/rust/issues/52452, I am not able to run the full test suite locally anymore at present)
The first few commits in the PR are changing how `evaluate` treats regions. We now track whether region comparisons occurred, reverting the "staticized" query approach that @arielb1 put in. The problem with "staticized" queries is that it relied on the leak-check to get higher-ranked things correct, and we are removing the leak-check in this PR series, so that caused problems.
You can see at the end a collection of test updates. Mostly we behave the same but with atrocious diagnostics, but there are a number of cases where we used to error and now no longer do, as well as single case where we used to **not** error but we now do (the coherence-subtyping change).
(Note: it would be possible to do a version of leak-check that propagates universe information and recover the old behavior. I am reluctant to do so because I'd like to leave us room to get more precise -- e.g., I want to eventually handle things like `exists<'a> { for<'b> { if ('a: 'b) { 'a: 'b } } }` which presently the leak-check cannot cope with etc. Also because it seems more consistent to me: most folks I've talked to expect the new behavior and are surprised to learn that binding sites were so significant before when it comes to coherence. One question is, though, to what extent are people relying on this in the wild?)
I noticed a duplicated "be" somewhere in the code. A search for it
manifested a couple more locations with the same problem. This change
removes one of the "be"s.
