Once this anonymization has performed, we have no
way of recovering the original names during NLL
borrow checking. Keeping the original names allows
error messages in full NLL mode to contain the original
bound region names.
As a result, the typeck results may contain types that
differ only in the names used for their bound regions. However,
anonimization of bound regions does not guarantee that
all distinct types are unqual (e.g. not subtypes of each other).
For example, `for<'a> fn(&'a u32, &'a u32)` and
`for<'b, 'c> fn(&'b u32, &'c u32)` are subtypes of each other,
as explained here:
63cc2bb3d0/compiler/rustc_infer/src/infer/nll_relate/mod.rs (L682-L690)
Therefore, any code handling types with higher-ranked regions already
needs to handle the case where two distinct `Ty`s are 'actually'
equal.
Currently, we use a relatively 'small' span for THIR
expressions generated by an 'adjustment' (e.g. an autoderef,
autoborrow, unsizing). As a result, if a borrow generated
by an adustment ends up causing a borrowcheck error, for example:
```rust
let mut my_var = String::new();
let my_ref = &my_var
my_var.push('a');
my_ref;
```
then the span for the mutable borrow may end up referring
to only the base expression (e.g. `my_var`), rather than
the method call which triggered the mutable borrow
(e.g. `my_var.push('a')`)
Due to a quirk of the MIR borrowck implementation,
this doesn't always get exposed in migration mode,
but it does in many cases.
This commit makes THIR building consistently use 'larger'
spans for adjustment expressions
The intent of this change it make it clearer to users
when it's the specific way in which a variable is
used (for example, in a method call) that produdes
a borrowcheck error. For example, an error message
claiming that a 'mutable borrow occurs here' might
be confusing if it just points at a usage of a variable
(e.g. `my_var`), when no `&mut` is in sight. Pointing
at the entire expression should help to emphasize
that the method call itself is responsible for
the mutable borrow.
In several cases, this makes the `#![feature(nll)]` diagnostic
output match up exactly with the default (migration mode) output.
As a result, several `.nll.stderr` files end up getting removed
entirely.
Enable new pass manager with LLVM 13
The new pass manager is enabled by default in clang since Clang/LLVM 13. Per the recent discussion on llvm-dev (https://lists.llvm.org/pipermail/llvm-dev/2021-August/152305.html) the legacy pass manager will be unmaintained in LLVM 14 and removed entirely in LLVM 15.
This switches us to use the new pass manager if LLVM >= 13 is used. It's possible to still use the old pass manager using `-Z new-llvm-pass-manager=no`.
Introduce `Rvalue::ShallowInitBox`
Polished version of #88700.
Implements MCP rust-lang/compiler-team#460, and should allow #43596 to go forward.
In short, creating an empty box is split from a nullary-op `NullOp::Box` into two steps, first a call to `exchange_malloc`, then a `Rvalue::ShallowInitBox` which transmutes `*mut u8` to a shallow-initialized `Box<T>`. This allows the `exchange_malloc` call to unwind. Details can be found in the MCP.
`NullOp::Box` is not yet removed, purely to make reverting easier in case anything goes wrong as the result of this PR. If revert is needed a reversion of "Use Rvalue::ShallowInitBox for box expression" commit followed by a test bless should be sufficient.
Experiments in #88700 showed a very slight compile-time perf regression due to (supposedly) slightly more time spent in LLVM. We could omit unwind edge generation (in non-`oom=panic` case) in box expression MIR construction to restore perf; but I don't think it's necessary since runtime perf isn't affected and perf difference is rather small.
The new pass manager is enabled by default in clang since
Clang/LLVM 13. While the discussion about this is still ongoing
(https://lists.llvm.org/pipermail/llvm-dev/2021-August/152305.html)
it's expected that support for the legacy pass manager will be
dropped either in LLVM 14 or 15.
This switches us to use the new pass manager if LLVM >= 13 is used.
make `#[track_caller]` actually do stuff in `Steal::borrow`
makes this ICE message useful:
``thread 'rustc' panicked at 'attempted to read from stolen value', /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c\compiler\rustc_data_structures\src\steal.rs:37:21``
Rollup of 8 pull requests
Successful merges:
- #88893 (Add 1.56.0 release notes)
- #89001 (Be explicit about using Binder::dummy)
- #89072 (Avoid a couple of Symbol::as_str calls in cg_llvm )
- #89104 (Simplify scoped_thread)
- #89208 ([rfc 2229] Drop fully captured upvars in the same order as the regular drop code)
- #89210 (Add missing time complexities to linked_list.rs)
- #89217 (Enable "generate-link-to-definition" option on rust tools docs as well)
- #89221 (Give better error for `macro_rules! name!`)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Add basic checks for well-formedness of `fn`/`fn_mut` lang items
This pull request fixes#83471. Lang items are never actually checked for well-formedness (#9307). This means that one can get an ICE quite easily, e.g. as follows:
```rust
#![feature(lang_items)]
#[lang = "fn"]
trait MyFn {
const call: i32 = 42;
}
fn main() {
(|| 42)();
}
```
or this:
```rust
#![feature(lang_items)]
#[lang = "fn"]
trait MyFn {
fn call(i: i32, j: i32);
}
fn main() {
(|| 42)();
}
```
Ideally, there should probably be a more comprehensive strategy for checking lang items for well-formedness, but for the time being, I have added some rudimentary well-formedness checks that prevent #83471 and similar issues.
[rfc 2229] Drop fully captured upvars in the same order as the regular drop code
Currently, with the new 2021 edition, if a closure captures all of the
fields of an upvar, we'll drop those fields in the order they are used
within the closure instead of the normal drop order (the definition
order of the fields in the type).
This changes that so we sort the captured fields by the definition order
which causes them to drop in that same order as well.
Fixesrust-lang/project-rfc-2229#42
r? `@nikomatsakis`
Avoid a couple of Symbol::as_str calls in cg_llvm
This should improve performance a tiny bit. Also remove `Symbol::len` and make `SymbolIndex` private.
Be explicit about using Binder::dummy
This is somewhat of a late followup to the binder refactor PR. It removes `ToPredicate` and `ToPolyTraitImpls` that hide the use of `Binder::dummy`. While this does make code a bit more verbose, it allows us be more careful about where we create binders.
Another alternative here might be to add a new trait `ToBinder` or something with a `dummy()` fn. Which could still allow grepping but allows doing something like `trait_ref.dummy()` (but I also wonder if longer-term, it would be better to be even more explicit with a `bind_with_vars(ty::List::empty())` *but* that's not clear yet.
r? ``@nikomatsakis``
The `Option<Module>` version is supported for the case where we don't know whether the `DefId` refers to a module or not.
Non-local traits and enums are also correctly found now.
