Avoid overflow in `std::iter::Skip::count`
The call to `count` on the inner iterator can overflow even if `Skip` itself would return less that `usize::max_value()` items.
Fixes#68139
Account for non-types in substs for opaque type error messages
Fixes#68368
Previously, I assumed that the substs contained only types, which caused
the computed index number to be wrong.
Previously, rustc mandated that cdylibs could only link against rlibs as
dependencies (not dylibs).
This commit disables that restriction and tests that it works in a
simple case.
Avoid declaring a fake dependency edge
When we're producing an rlib, we do not need anything more than an rmeta file
for each of our dependencies (this is indeed utilized by Cargo for pipelining).
Previously, we were still storing the paths of possible rlib/dylib crates, which
meant that they could still plausibly be accessed. With -Zbinary-dep-depinfo,
that meant that Cargo thought that rustc was using both the rlib and an (earlier
emitted) rmeta, and so needed a recompile, as the rlib may have finished writing
*after* compilation started (for more detail, see issue 68149).
This commit changes metadata loading to not store the filepaths of dylib/rlib if
we're going to end up creating an rlib only.
Fixes#68149.
Fix try-op diagnostic in E0277 for methods
For methods the try-op diagnostic displays the empty string where
it has more descriptive strings like “a function” otherwise:
error[E0277]: the `?` operator can only be used in that returns `Result` or `Option` (or another type that implements `std::ops::Try`)
^^
| | ^^ cannot use the `?` operator in that returns `()`
^^
I’m seeing this on nightly (rustc 1.42.0-nightly (b5a3341f1
2020-01-20)) and [on the playpen](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=0e7ce7792c2aceb8056941710d539124).
The changeset add strings for impl methods and trait provided
methods and test cases for the option type.
Make `TooGeneric` error in WF checking a proper error
`TooGeneric` is encountered during WF checking when we cannot determine that a constant involving a generic parameter will always be evaluated successfully (rather than resulting in an error). In these cases, the burden of proof should be with the caller, so that we can avoid post-monomorphisation tim errors (which was the previous previous behaviour). This commit ensures that this situation produces a proper compiler error, rather than silently ignoring it or ICEing.
Fixes https://github.com/rust-lang/rust/issues/66962.
r? @eddyb
Implement `?const` opt-out for trait bounds
For now, such bounds are treated exactly the same as unprefixed ones in all contexts. [RFC 2632](https://github.com/rust-lang/rfcs/pull/2632) does not specify whether such bounds are forbidden outside of `const` contexts, so they are allowed at the moment.
Prior to this PR, the constness of a trait bound/impl was stored in `TraitRef`. Now, the constness of an `impl` is stored in `ast::ItemKind::Impl` and the constness of a bound in `ast::TraitBoundModifer`. Additionally, constness of trait bounds is now stored in an additional field of `ty::Predicate::Trait`, and the combination of the constness of the item along with any `TraitBoundModifier` determines the constness of the bound in accordance with the RFC. Encoding the constness of impls at the `ty` level is left for a later PR.
After a discussion in \#wg-grammar on Discord, it was decided that the grammar should not encode the mutual exclusivity of trait bound modifiers. The grammar for trait bound modifiers remains `[?const] [?]`. To encode this, I add a dummy variant to `ast::TraitBoundModifier` that is used when the syntax `?const ?` appears. This variant causes an error in AST validation and disappears during HIR lowering.
cc #67794
r? @oli-obk
`TooGeneric` is encountered during WF checking when we cannot determine that a constant involving a generic parameter will always be evaluated successfully (rather than resulting in an error). In these cases, the burden of proof should be with the caller, so that we can avoid post-monomorphisation tim errors (which was the previous previous behaviour). This commit ensures that this situation produces a proper compiler error, rather than silently ignoring it or ICEing.
Filter and test predicates using `normalize_and_test_predicates` for const-prop
Fixes#68264
Previously, I attempted to use
`substitute_normalize_and_test_predicates` to detect unsatisfiable
bounds. Unfortunately, since const-prop runs in a generic environment
(we don't have any of the function's generic parameters substituted),
this could lead to cycle errors when attempting to normalize predicates.
This check is replaced with a more precise check. We now only call
`normalize_and_test_predicates` on predicates that have the possibility
of being proved unsatisfiable - that is, predicates that don't depend
on anything local to the function (e.g. generic parameters). This
ensures that we don't hit cycle errors when we normalize said
predicates, while still ensuring that we detect unsatisfiable
predicates.
I haven't been able to come up with a minimization of the Diesel issue - however, I've verified that it compiles successfully.
Fix some tests failing in `--pass check` mode
Warnings reported at codegen or linking time either have to be converted to errors (preferable), or the tests for them need to be marked with `// ignore-pass` (as a last resort).
ecd5852194 turned them from errors to warnings, but that shouldn't be necessary because it's still clear from the `.stderr` output that the errors are lints and not hard-coded.
fmt::Formatter is still not Send/Sync, but the UI test emitted two errors, for
the dyn Write and the Void inside Formatter. As of this PR, the Void is now
gone, but the dyn Write remains.
Remove real_drop_in_place
In af9b057156, I added `real_drop_in_place` because Stacked Borrows at the time couldn't handle transmuting of mutable references to raw pointers and back. Stacked Borrows 2, however, doesn't have any issue with these transmutes, so it is time to remove this hack again.
This doesn't mention that using an existing lifetime is possible, but
that would hopefully be clear as always being an option. The intention
of this is to teach newcomers what the lifetime syntax is.
Don't discard marker trait impls when inference variables are present
Fixes#61651
Previously, we would unconditionally discard impl candidates for marker
traits during trait selection. However, if the predicate had inference
variables, this could have the effect of constrainting inference
variables (due to a successful trait selection) when we would have
otherwise failed due to mutliple applicable impls,
This commit prevents marker trait impls from being discarded while the
obligation predicate has any inference variables, ensuring that
discarding impls will never cause us to incorrectly constraint inference
variables.
Make iter::Empty<T> Send and Sync for any T
Continuing from #57682
It's quite funny, when I initially submitted this pull request, I said "Likely nobody will be using that property of `iter::empty`", but then a year later I got a compilation error because it wasn't `Send` and `Sync`.
Unfortunately, `PhantomData<fn() -> T>` still errors out. Oh well. I proposed `
struct PhantomFnWorkaround<T>(fn() -> T);`, but dtolnay did not like it, so using explicit implementations.
