feat(rustc_lint): add `dyn_drop`
Based on the conversation in #86747.
Explanation
-----------
A trait object bound of the form `dyn Drop` is most likely misleading and not what the programmer intended.
`Drop` bounds do not actually indicate whether a type can be trivially dropped or not, because a composite type containing `Drop` types does not necessarily implement `Drop` itself. Naïvely, one might be tempted to write a deferred drop system, to pull cleaning up memory out of a latency-sensitive code path, using `dyn Drop` trait objects. However, this breaks down e.g. when `T` is `String`, which does not implement `Drop`, but should probably be accepted.
To write a trait object bound that accepts anything, use a placeholder trait with a blanket implementation.
```rust
trait Placeholder {}
impl<T> Placeholder for T {}
fn foo(_x: Box<dyn Placeholder>) {}
```
Make expansions stable for incr. comp.
This PR aims to make expansions stable for incr. comp. by using the same architecture as definitions:
- the interned identifier `ExpnId` contains a `CrateNum` and a crate-local id;
- bidirectional maps `ExpnHash <-> ExpnId` are setup;
- incr. comp. on-disk cache saves and reconstructs expansions using their `ExpnHash`.
I tried to use as many `LocalExpnId` as I could in the resolver code, but I may have missed a few opportunities.
All this will allow to use an `ExpnId` as a query key, and to force this query without recomputing caller queries. For instance, this will be used to implement #85999.
r? `@petrochenkov`
Remove refs from Pat slices
Changes `PatKind::Or(&'hir [&'hir Pat<'hir>])` to `PatKind::Or(&'hir [Pat<'hir>])` and others. This is more consistent with `ExprKind`, saves a little memory, and is a little easier to use.
Update cargo
13 commits in 3ebb5f15a940810f250b68821149387af583a79e..66a6737a0c9f3a974af2dd032a65d3e409c77aac
2021-07-02 20:35:38 +0000 to 2021-07-14 20:54:28 +0000
- Add format option to `cargo tree` to print the lib_name (rust-lang/cargo#9663)
- Prefer patched versions of dependencies (rust-lang/cargo#9639)
- When a dependency does not have a version, git or path, fails directly (rust-lang/cargo#9686)
- Spot the crate typo easily (rust-lang/cargo#9665)
- remove unnecessary 'collect' (rust-lang/cargo#9616)
- Make it easier to run testsuite with a custom toolchain. (rust-lang/cargo#9679)
- Serialize `cargo fix` (rust-lang/cargo#9677)
- Don't recommend filing issues on rust-lang/cargo for Cargo.toml errors. (rust-lang/cargo#9658)
- Update nightly failure notification. (rust-lang/cargo#9657)
- Update Windows env uppercase key check. (rust-lang/cargo#9654)
- Unignore fix_edition_2021. (rust-lang/cargo#9662)
- Warning when using features in patch (rust-lang/cargo#9666)
- Unify cargo and rustc's error reporting (rust-lang/cargo#9655)
Fix internal `default_hash_types` lint to use resolved path
I run into false positives now and then (mostly in Clippy) when I want to name some util after HashMap.
target abi
Implement cfg(target_abi) (RFC 2992)
Add an `abi` field to `TargetOptions`, defaulting to "". Support using
`cfg(target_abi = "...")` for conditional compilation on that field.
Gated by `feature(cfg_target_abi)`.
Add a test for `target_abi`, and a test for the feature gate.
Add `target_abi` to tidy as a platform-specific cfg.
Update targets to use `target_abi`
All eabi targets have `target_abi = "eabi".`
All eabihf targets have `target_abi = "eabihf"`.
`armv6_unknown_freebsd` and `armv7_unknown_freebsd` have `target_abi = "eabihf"`.
All abi64 targets have `target_abi = "abi64"`.
All ilp32 targets have `target_abi = "ilp32"`.
All softfloat targets have `target_abi = "softfloat"`.
All *-uwp-windows-* targets have `target_abi = "uwp"`.
All spe targets have `target_abi = "spe"`.
All macabi targets have `target_abi = "macabi"`.
aarch64-apple-ios-sim has `target_abi = "sim"`.
`x86_64-fortanix-unknown-sgx` has `target_abi = "fortanix"`.
`x86_64-unknown-linux-gnux32` has `target_abi = "x32"`.
Add FIXME entries for targets for which existing values need to change
once `cfg_target_abi` becomes stable. (All of them are tier 3 targets.)
Add a test for `target_abi` in `--print cfg`.
Support pretty printing slices using GDB
Support pretty printing `&[T]`, `&mut [T]` and `&mut str` types using GDB.
Support pretty printing `&mut [T]` and `&mut str` types using LLDB.
Fixes#85219.
Add an `abi` field to `TargetOptions`, defaulting to "". Support using
`cfg(target_abi = "...")` for conditional compilation on that field.
Gated by `feature(cfg_target_abi)`.
Add a test for `target_abi`, and a test for the feature gate.
Add `target_abi` to tidy as a platform-specific cfg.
This does not add an abi to any existing target.
Replace per-target ABI denylist with an allowlist
It makes very little sense to maintain denylists of ABIs when, as far as
non-generic ABIs are concerned, targets usually only support a small
subset of the available ABIs.
This has historically been a cause of bugs such as us allowing use of
the platform-specific ABIs on x86 targets – these in turn would cause
LLVM errors or assertions to fire.
In this PR we got rid of the per-target ABI denylists, and instead compute
which ABIs are supported with a simple match based on, mostly, the
`Target::arch` field. Among other things, this makes it impossible to
forget to consider this problem (in either direction) and forces one to
consider what the ABI support looks like when adding an ABI (rarely)
rather than target (often), which should hopefully also reduce the
cognitive load on both contributors as well as reviewers.
Fixes#57182
Sponsored by: standard.ai
---
## Summary for teams
One significant user-facing change after this PR is that there's now a future compat warning when building…
* `stdcall`, `fastcall`, `thiscall` using code with targets other than 32-bit x86 (i386...i686) or *-windows-*;
* `vectorcall` using code when building for targets other than x86 (either 32 or 64 bit) or *-windows-*.
Previously these ABIs have been accepted much more broadly, even for architectures and targets where this made no sense (e.g. on wasm32) and would fall back to the C ABI. In practice this doesn't seem to be used too widely and the [breakages in crater](https://github.com/rust-lang/rust/pull/86231#issuecomment-866300943) that we see are mostly about Windows-specific code that was missing relevant `cfg`s and just happened to successfully `check` on Linux for one reason or another.
The intention is that this warning becomes a hard error after some time.
It makes very little sense to maintain denylists of ABIs when, as far as
non-generic ABIs are concerned, targets usually only support a small
subset of the available ABIs.
This has historically been a cause of bugs such as us allowing use of
the platform-specific ABIs on x86 targets – these in turn would cause
LLVM errors or assertions to fire.
Fixes#57182
Sponsored by: standard.ai
Bump deps
tidy: updated cargo_metadata to 0.12 (rustfmt only one left, that depends on 0.8 version in tree, waiting when it merges into rustc repo)
miow v0.3.6 -> v0.3.7, drops socket2 v0.3.19
curl v0.4.36 -> v0.4.38
curl-sys v0.4.42+curl-7.76.0 -> v0.4.44+curl-7.77.0
fixes CVE's https://curl.se/docs/vuln-7.76.0.html
Hack: Ignore inference variables in certain queries
Fixes#84841Fixes#86753
Some queries are not built to accept types with inference variables, which can lead to ICEs. These queries probably ought to be converted to canonical form, but as a quick workaround, we can return conservative results in the case that inference variables are found.
We should file a follow-up issue (and update the FIXMEs...) to do the proper refactoring.
cc `@arora-aman`
r? `@oli-obk`
Eric Huss