Previously, if you tried to write this (using the specialization
feature flag):
default impl PartialEq<MyType> {
...
}
The compiler would give you the mysterious warning "inherent impls
cannot be default". What it really means is that you're trying to
write an impl for a Structure or *Trait Object*, and that cannot
be "default". However, one of the ways to encounter this error
(as shown by the above example) is when you forget to write "for
MyType".
This PR adds a help message that reads "maybe missing a `for`
keyword?" This is useful, actionable advice that will help any user
identify their mistake, and doesn't get in the way or mislead any
user that really meant to use the "default" keyword for this weird
purpose. In particular, this help message will be useful for any
users who don't know the "inherent impl" terminology, and/or users
who forget that inherent impls CAN be written for traits (they apply
to the trait objects). Both of these are somewhat confusing, seldom-
used concepts; a one-line error message without any error number for
longer explanation is NOT the place to introduce these ideas.
- `ParamEnv::empty()` -- does not reveal all, good for typeck
- `ParamEnv::reveal_all()` -- does, good for trans
- `param_env.with_reveal_all()` -- converts an existing parameter environment
Warn about ignored generic bounds in `for`
This adds a new lint to fix#42181. For consistency and to avoid code duplication, I also moved the existing "bounds in type aliases are ignored" here.
Questions to the reviewer:
* Is it okay to just remove a diagnostic error code like this? Should I instead keep the warning about type aliases where it is? The old code provided a detailed explanation of what's going on when asked, that information is now lost. On the other hand, `span_warn!` seems deprecated (after this patch, it has exactly one user left!).
* Did I miss any syntactic construct that can appear as `for` in the surface syntax? I covered function types (`for<'a> fn(...)`), generic traits (`for <'a> Fn(...)`, can appear both as bounds as as trait objects) and bounds (`for<'a> F: ...`).
* For the sake of backwards compatibility, this adds a warning, not an error. @nikomatsakis suggested an error in https://github.com/rust-lang/rust/issues/42181#issuecomment-306924389, but I feel that can only happen in a new epoch -- right?
Cc @eddyb
Also move the check for not having type parameters into ast_validation.
I was not sure what to do with compile-fail/issue-23046.rs: The issue looks like
maybe the bounds actually played a role in triggering the ICE, but that seems
unlikely given that the compiler seems to entirely ignore them. However, I
couldn't find a testcase without the bounds, so I figured the best I could do is
to just remove the bounds and make sure at least that keeps working.
Remove "static item recursion checking" in favor of relying on cycle checks in the query engine
Tests are changed to use the cycle check error message instead. Some duplicate tests are removed.
r? @eddyb
Fix span of visibility
This PR
1. adds a closing parenthesis to the span of `Visibility::Crate` (e.g. `pub(crate)`). The current span only covers `pub(crate`.
2. adds a `span` field to `Visibility::Restricted`. This span covers the entire visibility expression (e.g. `pub (in self)`). Currently all we can have is a span for `Path`.
This PR is motivated by the bug found in rustfmt (https://github.com/rust-lang-nursery/rustfmt/issues/2398).
The first change is a strict improvement IMHO. The second change may not be desirable, as it adds a field which is currently not used by the compiler.
Don't promote to 'static the result of dereferences.
This is a **breaking change**, removing copies out of dereferences from rvalue-to-`'static` promotion.
With miri we won't easily know whether the dereference itself would see the same value at runtime as miri (e.g. after mutating a `static`) or even if it can be interpreted (e.g. integer pointers).
One alternative to this ban is defining at least *some* of those situations as UB, i.e. you shouldn't have a reference in the first place, and you should work through raw pointers instead, to avoid promotion.
**EDIT**: The other *may seem* to be to add some analysis which whitelists references-to-constant-values and assume any values produced by arbitrary computation to not be safe to promote dereferences thereof - but that means producing a reference from an associated constant or `const fn` would necessarily obscure it, and in the former case, this could still impact code that runs on stable today. What we do today to track "references to statics" only works because we restrict taking a reference to a `static` at all to other `static`s (which, again, are currently limited in that they can't be read at compile-time) and to runtime-only `fn`s (*not* `const fn`s).
I'm primarily opening this PR with a conservative first approximation (e.g. `&(*r).a` is not allowed, only reborrows are, and in the old borrow only implicit ones from adjustments, at that) for cratering.
r? @nikomatsakis
Sometimes a simple goto misses the cleanup/unwind edges. Specifically, in the
case of infinite loops such as those introduced by a loop statement without any
other out edges. Analogous to TerminatorKind::FalseEdges; this new terminator
kind is used when we want borrowck to consider an unwind path, but real control
flow should never actually take it.
Properly parse impls for the never type `!`
Recover from missing `for` in `impl Trait for Type`
Prohibit inherent default impls and default impls of auto traits
Change wording in more diagnostics to use "auto traits"
Some minor code cleanups in the parser
No longer parse it.
Remove AutoTrait variant from AST and HIR.
Remove backwards compatibility lint.
Remove coherence checks, they make no sense for the new syntax.
Remove from rustdoc.
Prevent unwinding past FFI boundaries
Second attempt to write a patch to solve this.
r? @nikomatsakis
~~So, my biggest issue with this patch is the way the patch determines *what* functions should have an abort landing pad (in `construct_fn`). I would ideally have this code match [src/librustc_trans/callee.rs::get_fn](https://github.com/rust-lang/rust/blob/master/src/librustc_trans/callee.rs#L107-L115) but couldn't find an id that returns true for `is_foreign_item`. Also tried `tcx.has_attr("unwind")` with no luck.~~ FIXED
Other issues:
* llvm.trap is an SIGILL on amd64. Ideally we could use panic-abort's version of aborting which is nicer but we don't want to depend on that library...
* ~~Mir inlining is a stub currently.~~ FIXED (no-op)
Also, when reviewing please take into account that I'm new to the code and only partially know what I'm doing... and that I've mostly made made matches on `TerminatorKind::Abort` match either `TerminatorKind::Resume` or `TerminatorKind::Unreachable` based on what looked best.
The Generics now contain one Vec of an enum for the generic parameters,
rather than two separate Vec's for lifetime and type parameters.
Additionally, places that previously used Vec<LifetimeDef> now use
Vec<GenericParam> instead.
