Commit Graph

143154 Commits

Author SHA1 Message Date
Eric Huss b0e49c798b Update cargo 2021-05-07 16:51:52 -07:00
bors 770792ff8d Auto merge of #84980 - flip1995:clippyup, r=Manishearth
Update Clippy

Bi-weekly Clippy update.

r? `@Manishearth`
2021-05-07 19:28:03 +00:00
bors ca712bc425 Auto merge of #85036 - Dylan-DPC:rollup-4qfabo3, r=Dylan-DPC
Rollup of 9 pull requests

Successful merges:

 - #84254 (illumos should put libc last in library search order)
 - #84442 (Unify rustc and rustdoc parsing of `cfg()`)
 - #84655 (Cleanup of `wasm`)
 - #84866 (linker: Avoid library duplication with `/WHOLEARCHIVE`)
 - #84930 (rename LLVM target for RustyHermit)
 - #84991 (rustc: Support Rust-specific features in -Ctarget-feature)
 - #85029 (SGX mutex is movable)
 - #85030 (Rearrange SGX split module files)
 - #85033 (some further small cleanups)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
2021-05-07 16:24:46 +00:00
Dylan DPC 42848090b5
Rollup merge of #85033 - lcnr:nits2, r=jackh726
some further small cleanups
2021-05-07 16:19:25 +02:00
Dylan DPC 62b68f9688
Rollup merge of #85030 - jethrogb:jb/sgx-rearrange-files, r=nagisa
Rearrange SGX split module files

In #75979 several inlined modules were split out into multiple files.
This PR keeps the multiple files but moves a few things around to
organize things in a coherent way.
2021-05-07 16:19:24 +02:00
Dylan DPC 73d3544fb9
Rollup merge of #85029 - jethrogb:jb/sgx-movable-mutex, r=m-ou-se
SGX mutex is movable

r? ``@m-ou-se``
2021-05-07 16:19:23 +02:00
Dylan DPC a3fbde4240
Rollup merge of #84991 - alexcrichton:target-feature-remap, r=nagisa
rustc: Support Rust-specific features in -Ctarget-feature

Since the beginning of time the `-Ctarget-feature` flag on the command
line has largely been passed unmodified to LLVM. Afterwards, though, the
`#[target_feature]` attribute was stabilized and some of the names in
this attribute do not match the corresponding LLVM name. This is because
Rust doesn't always want to stabilize the exact feature name in LLVM for
the equivalent functionality in Rust. This creates a situation, however,
where in Rust you'd write:

    #[target_feature(enable = "pclmulqdq")]
    unsafe fn foo() {
        // ...
    }

but on the command line you would write:

    RUSTFLAGS="-Ctarget-feature=+pclmul" cargo build --release

This difference is somewhat odd to deal with if you're a newcomer and
the situation may be made worse with upcoming features like [WebAssembly
SIMD](https://github.com/rust-lang/rust/issues/74372) which may be more
prevalent.

This commit implements a mapping to translate requests via
`-Ctarget-feature` through the same name-mapping functionality that's
present for attributes in Rust going to LLVM. This means that
`+pclmulqdq` will work on x86 targets where as previously it did not.

I've attempted to keep this backwards-compatible where the compiler will
just opportunistically attempt to remap features found in
`-Ctarget-feature`, but if there's something it doesn't understand it
gets passed unmodified to LLVM just as it was before.
2021-05-07 16:19:22 +02:00
Dylan DPC cea6e4d6b9
Rollup merge of #84930 - hermitcore:target, r=nagisa
rename LLVM target for RustyHermit

- RustyHermit is a library operating system, where the user-
  and the kernel-space use the same target
- by a mistake a previous patch changes the target to an incorect value
- this merge request revert the previous changes
2021-05-07 16:19:21 +02:00
Dylan DPC 6e4c842305
Rollup merge of #84866 - petrochenkov:wholesome, r=Mark-Simulacrum
linker: Avoid library duplication with `/WHOLEARCHIVE`

Looks like in #72785 I misinterpreted how the `link.exe`'s `/WHOLEARCHIVE` flag works.

It's not necessary to write `mylib /WHOLEARCHIVE:mylib` to mark `mylib` as whole archive, `/WHOLEARCHIVE:mylib` alone is enough.

https://docs.microsoft.com/en-us/cpp/build/reference/wholearchive-include-all-library-object-files?view=msvc-160
2021-05-07 16:19:20 +02:00
Dylan DPC 8f0b1863d0
Rollup merge of #84655 - CDirkx:wasm, r=m-ou-se
Cleanup of `wasm`

Some more cleanup of `sys`, this time `wasm`

- Reuse `unsupported::args` (functionally equivalent implementation, just an empty iterator).
- Split out `atomics` implementation of `wasm::thread`, the non-`atomics` implementation is reused from `unsupported`.
- Move all of the `atomics` code to a separate directory `wasm/atomics`.

````@rustbot```` label: +T-libs-impl
r? ````@m-ou-se````
2021-05-07 16:19:20 +02:00
Dylan DPC 0c8c21d224
Rollup merge of #84442 - jyn514:doc-cfg, r=petrochenkov
Unify rustc and rustdoc parsing of `cfg()`

This extracts a new `parse_cfg` function that's used between both.

- Treat `#[doc(cfg(x), cfg(y))]` the same as `#[doc(cfg(x)]
  #[doc(cfg(y))]`. Previously it would be completely ignored.
- Treat `#[doc(inline, cfg(x))]` the same as `#[doc(inline)]
  #[doc(cfg(x))]`. Previously, the cfg would be ignored.
- Pass the cfg predicate through to rustc_expand to be validated

Technically this is a breaking change, but doc_cfg is still nightly so I don't think it matters.

Fixes https://github.com/rust-lang/rust/issues/84437.

r? `````````@petrochenkov`````````
2021-05-07 16:19:19 +02:00
Dylan DPC cd37b95058
Rollup merge of #84254 - jclulow:illumos-link-order, r=petrochenkov
illumos should put libc last in library search order

Under some conditions, the toolchain will produce a sequence of linker
arguments that result in a NEEDED list that puts libc before libgcc_s;
e.g.,

    [0]  NEEDED            0x2046ba            libc.so.1
    [1]  NEEDED            0x204723            libm.so.2
    [2]  NEEDED            0x204736            libsocket.so.1
    [3]  NEEDED            0x20478b            libumem.so.1
    [4]  NEEDED            0x204763            libgcc_s.so.1

Both libc and libgcc_s provide an unwinder implementation, but libgcc_s
provides some extra symbols upon which Rust directly depends.  If libc
is first in the NEEDED list we will find some of those symbols in libc
but others in libgcc_s, resulting in undefined behaviour as the two
implementations do not use compatible interior data structures.

This solution is not perfect, but is the simplest way to produce correct
binaries on illumos for now.
2021-05-07 16:19:18 +02:00
Jethro Beekman bfa84842e5 Rearrange SGX split module files
In #75979 several inlined modules were split out into multiple files.
This PR keeps the multiple files but moves a few things around to
organize things in a coherent way.
2021-05-07 13:55:03 +02:00
Jethro Beekman 30b82e0f96 SGX mutex is movable 2021-05-07 13:21:38 +02:00
lcnr e00146f504 fulfillment typo 2021-05-07 12:17:58 +02:00
lcnr 3c3cf08e39 wfcheck fcx <-> tcx cleanup 2021-05-07 12:15:38 +02:00
bors e5f83d24ae Auto merge of #84797 - richkadel:cover-unreachable-statements, r=tmandry
Report coverage `0` of dead blocks

Fixes: #84018

With `-Z instrument-coverage`, coverage reporting of dead blocks
(for example, blocks dropped because a conditional branch is dropped,
based on const evaluation) is now supported.

If `instrument-coverage` is enabled, `simplify::remove_dead_blocks()`
finds all dropped coverage `Statement`s and adds their `code_region`s as
`Unreachable` coverage `Statement`s to the `START_BLOCK`, so they are
still included in the coverage map.

Check out the resulting changes in the test coverage reports in this PR (in [commit 1](0b0d293c7c)).

r? `@tmandry`
cc: `@wesleywiser`
2021-05-07 10:06:40 +00:00
Stefan Lankes 76f884abb9 rename LLVM target for RustyHermit
RustyHermit ist is a library operating system. In this case, we link a static library as kernel to the application. The final result is a bootable application. The library and the application have to use the same target. Currently, the targets are different (see also https://github.com/rust-lang/rust/blob/master/compiler/rustc_target/src/spec/x86_64_unknown_hermit.rs). Consequently, this commit change the LLVM target to 'hermit'.

This kernel spec is needed to disable the usage of FPU registers, which are not allowed in kernel space. In contrast to Linux, everything is running in ring 0 and also in the same address space.

Signed-off-by: Stefan Lankes <slankes@eonerc.rwth-aachen.de>
2021-05-07 10:09:11 +02:00
bors ac888e8675 Auto merge of #85022 - JohnTitor:rollup-2q4706v, r=JohnTitor
Rollup of 9 pull requests

Successful merges:

 - #84779 (Add support for --test-args to cargotest)
 - #84781 (Don't check bootstrap artifacts by default)
 - #84787 (bump deps)
 - #84815 (Update coverage docs and command line help)
 - #84875 (Removes unneeded check of `#[no_coverage]` in mapgen)
 - #84897 (Coverage instruments closure bodies in macros (not the macro body))
 - #84911 (Retry clang+llvm download)
 - #84972 (CTFE inbounds-error-messages tweak)
 - #84990 (Sort rustdoc-gui tests)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
2021-05-07 07:44:53 +00:00
Yuki Okushi 87faf2e64f
Rollup merge of #84990 - GuillaumeGomez:sort-rustdoc-gui-tests, r=Mark-Simulacrum
Sort rustdoc-gui tests

The rustdoc-gui tests were randomly run. Not really a big issue but I prefer the tests to be sorted.
2021-05-07 15:20:30 +09:00
Yuki Okushi 47050275f4
Rollup merge of #84972 - RalfJung:null-ptr-msg, r=oli-obk
CTFE inbounds-error-messages tweak

* use CheckInAllocMsg::PointerArithmeticTest for ptr_offset error
* nicer errors for some null pointer cases

r? `@oli-obk`
2021-05-07 15:20:29 +09:00
Yuki Okushi 326fec27a6
Rollup merge of #84911 - Mark-Simulacrum:retry-clang, r=pietroalbini
Retry clang+llvm download

We've been seeing a pretty high rate of spurious network failures (e.g., openssl
connection reset by peer). Not clear why, but let's add a retry.

r? `@pietroalbini`
2021-05-07 15:20:28 +09:00
Yuki Okushi 343a094aa1
Rollup merge of #84897 - richkadel:cover-closure-macros, r=tmandry
Coverage instruments closure bodies in macros (not the macro body)

Fixes: #84884

This solution might be considered a compromise, but I think it is the
better choice.

The results in the `closure.rs` test correctly resolve all test cases
broken as described in #84884.

One test pattern (in both `closure_macro.rs` and
`closure_macro_async.rs`) was also affected, and removes coverage
statistics for the lines inside the closure, because the closure
includes a macro. (The coverage remains at the callsite of the macro, so
we lose some detail, but there isn't a perfect choice with macros.

Often macro implementations are split across the macro and the callsite,
and there doesn't appear to be a single "right choice" for which body
should be covered. For the current implementation, we can't do both.

The callsite is most likely to be the preferred site for coverage.

r? `@tmandry`
cc: `@wesleywiser`
2021-05-07 15:20:26 +09:00
Yuki Okushi b088318985
Rollup merge of #84875 - richkadel:no-coverage-dont-check-unused, r=tmandry
Removes unneeded check of `#[no_coverage]` in mapgen

There is an anticipated feature request to support a compiler flag that
only adds coverage for specific files (or perhaps mods). As I thought
about where that change would need to be supported, I realized that
checking the attribute in mapgen (for unused functions) was unnecessary.
The unused functions are only synthesized if they have MIR coverage, and
functions with the `no_coverage` attribute will not have been
instrumented with MIR coverage statements in the first place.

New tests confirm this.

Also, while adding tests, I updated resolved comments and FIXMEs in
other tests, and expanded comments and tests on one remaining issue that
is still not resolved.

r? `@tmandry`
cc: `@wesleywiser`
2021-05-07 15:20:25 +09:00
Yuki Okushi 283ef86784
Rollup merge of #84815 - richkadel:coverage-docs-update-2021-05, r=tmandry
Update coverage docs and command line help

r? `@tmandry`
cc: `@wesleywiser`
2021-05-07 15:20:24 +09:00
Yuki Okushi 246e8d17ff
Rollup merge of #84787 - klensy:deps-bump, r=Mark-Simulacrum
bump deps

openssl vulns:
https://rustsec.org/advisories/RUSTSEC-2021-0056.html
https://rustsec.org/advisories/RUSTSEC-2021-0055.html

openssl-src v111.12.0+1.1.1h -> v111.15.0+1.1.1k

not latest, but newer
openssl-sys v0.9.58 -> v0.9.61
openssl v0.10.30 -> v0.10.33

curl vulns: https://curl.se/docs/vuln-7.74.0.html

curl v0.4.34 -> v0.4.36
curl-sys v0.4.39+curl-7.74.0 -> v0.4.42+curl-7.76.0
2021-05-07 15:20:23 +09:00
Yuki Okushi 1224e1341a
Rollup merge of #84781 - jyn514:check-bootstrap, r=Mark-Simulacrum
Don't check bootstrap artifacts by default

Bootstrap has to build successfully or this won't run, so all it checks
are the tests, which are uncommon to change.

Fixes https://github.com/rust-lang/rust/issues/76624.
2021-05-07 15:20:22 +09:00
Yuki Okushi 2d496f46bf
Rollup merge of #84779 - jyn514:cargotest-args, r=Mark-Simulacrum
Add support for --test-args to cargotest

This allows running a single test without having to wait for all tests
to complete.

Closes https://github.com/rust-lang/rust/issues/77260.
2021-05-07 15:20:21 +09:00
bors 1773f14a24 Auto merge of #85014 - Dylan-DPC:rollup-jzpbkdu, r=Dylan-DPC
Rollup of 11 pull requests

Successful merges:

 - #84409 (Ensure TLS destructors run before thread joins in SGX)
 - #84500 (Add --run flag to compiletest)
 - #84728 (Add test for suggestion to borrow unsized function parameters)
 - #84734 (Add `needs-unwind` and beginning of support for testing `panic=abort` std to compiletest)
 - #84755 (Allow using `core::` in intra-doc links within core itself)
 - #84871 (Disallows `#![feature(no_coverage)]` on stable and beta (using standard crate-level gating))
 - #84872 (Wire up tidy dependency checks for cg_clif)
 - #84896 (Handle incorrect placement of parentheses in trait bounds more gracefully)
 - #84905 (CTFE engine: rename copy → copy_intrinsic, move to intrinsics.rs)
 - #84953 (Remove unneeded call to with_default_session_globals in rustdoc highlight)
 - #84987 (small nits)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
2021-05-07 01:16:08 +00:00
Joshua M. Clulow 31c2ad0d4c illumos should put libc last in library search order
Under some conditions, the toolchain will produce a sequence of linker
arguments that result in a NEEDED list that puts libc before libgcc_s;
e.g.,

    [0]  NEEDED            0x2046ba            libc.so.1
    [1]  NEEDED            0x204723            libm.so.2
    [2]  NEEDED            0x204736            libsocket.so.1
    [3]  NEEDED            0x20478b            libumem.so.1
    [4]  NEEDED            0x204763            libgcc_s.so.1

Both libc and libgcc_s provide an unwinder implementation, but libgcc_s
provides some extra symbols upon which Rust directly depends.  If libc
is first in the NEEDED list we will find some of those symbols in libc
but others in libgcc_s, resulting in undefined behaviour as the two
implementations do not use compatible interior data structures.

This solution is not perfect, but is the simplest way to produce correct
binaries on illumos for now.
2021-05-06 17:08:10 -07:00
Dylan DPC 01e9d09d3b
Rollup merge of #84987 - lcnr:nits, r=Mark-Simulacrum
small nits
2021-05-07 00:38:45 +02:00
Dylan DPC 3c5da6e6b9
Rollup merge of #84953 - GuillaumeGomez:remove-unneeded-with_default_session_globals, r=jyn514
Remove unneeded call to with_default_session_globals in rustdoc highlight

This was the origin of the `Span` bug in https://github.com/rust-lang/rust/pull/84176.

cc `````@Aaron1011`````
r? `````@jyn514`````
2021-05-07 00:38:44 +02:00
Dylan DPC eec3ae3feb
Rollup merge of #84905 - RalfJung:copy, r=oli-obk
CTFE engine: rename copy → copy_intrinsic, move to intrinsics.rs

The `copy` name is confusing for this function because we also have `copy_op` which is pretty different. I hope `copy_intrinsic` is clearer. Also `step.rs` should really just contain the main loop and opcode dispatch, so move this helper function to a more appropriate place.

r? ``````@oli-obk``````
2021-05-07 00:38:43 +02:00
Dylan DPC b44e56f968
Rollup merge of #84896 - estebank:issue-84772, r=jackh726
Handle incorrect placement of parentheses in trait bounds more gracefully

Fix #84772.

CC ``````@jonhoo``````
2021-05-07 00:38:42 +02:00
Dylan DPC 746f97e969
Rollup merge of #84872 - bjorn3:cg_clif_tidy, r=Mark-Simulacrum
Wire up tidy dependency checks for cg_clif

Also contains a fix and improvement to tidy.

Required for https://github.com/rust-lang/rust/pull/81746.
2021-05-07 00:38:41 +02:00
Dylan DPC aaf23892ab
Rollup merge of #84871 - richkadel:no-coverage-unstable-only, r=nagisa
Disallows `#![feature(no_coverage)]` on stable and beta (using standard crate-level gating)

Fixes: #84836

Removes the function-level feature gating solution originally implemented, and solves the same problem using `allow_internal_unstable`, so normal crate-level feature gating mechanism can still be used (which disallows the feature on stable and beta).

I tested this, building the compiler with and without `CFG_DISABLE_UNSTABLE_FEATURES=1`

With unstable features disabled, I get the expected result as shown here:

```shell
$ ./build/x86_64-unknown-linux-gnu/stage1/bin/rustc     src/test/run-make-fulldeps/coverage/no_cov_crate.rs
error[E0554]: `#![feature]` may not be used on the dev release channel
 --> src/test/run-make-fulldeps/coverage/no_cov_crate.rs:2:1
  |
2 | #![feature(no_coverage)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0554`.
```

r? ````@Mark-Simulacrum````
cc: ````@tmandry```` ````@wesleywiser````
2021-05-07 00:38:40 +02:00
Dylan DPC 7835c7802d
Rollup merge of #84755 - jyn514:core-links, r=kennytm
Allow using `core::` in intra-doc links within core itself

I came up with this idea ages ago, but rustdoc used to ICE on it. Now it doesn't.

Helps with https://github.com/rust-lang/rust/issues/73445. Doesn't fix it completely since `extern crate self as std;` in std still gives strange errors.
2021-05-07 00:38:38 +02:00
Dylan DPC 577f1d007d
Rollup merge of #84734 - tmandry:compiletest-needs-unwind, r=Mark-Simulacrum
Add `needs-unwind` and beginning of support for testing `panic=abort` std to compiletest

For the Fuchsia platform we build libstd with `panic=abort` and would like a way to run tests with that enabled. This adds low-level support for this directly to compiletest.

In the future I'd like to add high-level support in rustbuild, e.g. having target-specific flags that allow configuring a panic strategy. (Side note: It would be nice if we could also build multiple configurations for the same target, but I'm getting ahead of myself.)

This plus #84500 have everything that's needed to get ui tests passing on fuchsia targets.

Part of #84766. Note that this change only includes the header on tests which need an unwinder to _build_, not those which need it to _run_.

r? ````@Mark-Simulacrum````
2021-05-07 00:38:37 +02:00
Dylan DPC 3a0d6bec56
Rollup merge of #84728 - camelid:sized-param-sugg-test, r=Mark-Simulacrum
Add test for suggestion to borrow unsized function parameters

Closes #82820.

This is a regression test for #82820.

This test case is included in more general tests, but I think the error
regressed because there were a bunch of other diagnostic changes in the
test that obscured this regression.

Hopefully, having a test specific to the suggestion, and running rustfix
for the test, will prevent this error from regressing in the future.
2021-05-07 00:38:36 +02:00
Dylan DPC dd3747b4ad
Rollup merge of #84500 - tmandry:compiletest-run-flag, r=Mark-Simulacrum
Add --run flag to compiletest

This controls whether run-* tests actually get run.

r? ```@Mark-Simulacrum```
2021-05-07 00:38:35 +02:00
Dylan DPC b30e428689
Rollup merge of #84409 - mzohreva:mz/tls-dtors-before-join, r=jethrogb
Ensure TLS destructors run before thread joins in SGX

The excellent test is from ```@jethrogb```

For context see: https://github.com/rust-lang/rust/pull/83416#discussion_r617282907
2021-05-07 00:38:33 +02:00
bors 777bb2f612 Auto merge of #84806 - Mark-Simulacrum:try-start-entry, r=cjgillot
Streamline try_start code

This shifts some branches around and avoids interleaving parallel and
non-parallel versions of the function too much.
2021-05-06 22:35:06 +00:00
bors 676ee14729 Auto merge of #79930 - tgnottingham:bufwriter_performance, r=m-ou-se
Optimize BufWriter
2021-05-06 20:04:32 +00:00
Rich Kadel cd3a8c1b7f Removes unneeded check of `#[no_coverage]` in mapgen
And adds tests to validate it still works.

There is an anticipated feature request to support a compiler flag that
only adds coverage for specific files (or perhaps mods). As I thought
about where that change would need to be supported, I realized that
checking the attribute in mapgen (for unused functions) was unnecessary.
The unused functions are only synthesized if they have MIR coverage, and
functions with the `no_coverage` attribute will not have been
instrumented with MIR coverage statements in the first place.

New tests confirm this.

Also, while adding tests, I updated resolved comments and FIXMEs in
other tests.
2021-05-06 12:44:49 -07:00
Rich Kadel 8075b28df1 Renamed compiler-flags file to name of compiler-flag: instrument-coverage
And redirect users from the old file name.
2021-05-06 12:21:24 -07:00
Rich Kadel f58a362d18 Update coverage docs and command line help 2021-05-06 12:20:31 -07:00
Camelid a7500e52ef Add test for suggestion to borrow unsized function parameters
This is a regression test for #82820.

This test case is included in more general tests, but I think the error
regressed because there were a bunch of other diagnostic changes in the
test that obscured this regression.

Hopefully, having a test specific to the suggestion, and running rustfix
for the test, will prevent this error from regressing in the future.
2021-05-06 12:06:43 -07:00
Vadim Petrochenkov fb9feb35ed linker: Avoid library duplication with `/WHOLEARCHIVE` 2021-05-06 21:22:25 +03:00
Rich Kadel cb70221857 Coverage instruments closure bodies in macros (not the macro body)
Fixes: #84884

This solution might be considered a compromise, but I think it is the
better choice.

The results in the `closure.rs` test correctly resolve all test cases
broken as described in #84884.

One test pattern (in both `closure_macro.rs` and
`closure_macro_async.rs`) was also affected, and removes coverage
statistics for the lines inside the closure, because the closure
includes a macro. (The coverage remains at the callsite of the macro, so
we lose some detail, but there isn't a perfect choice with macros.

Often macro implementations are split across the macro and the callsite,
and there doesn't appear to be a single "right choice" for which body
should be covered. For the current implementation, we can't do both.

The callsite is most likely to be the preferred site for coverage.

I applied this fix to all `MacroKinds`, not just `Bang`.

I'm trying to resolve an issue of lost coverage in a
`MacroKind::Attr`-based, function-scoped macro. Instead of only
searching for a body_span that is "not a function-like macro" (that is,
MacroKind::Bang), I'm expanding this to all `MacroKind`s. Maybe I should
expand this to `ExpnKind::Desugaring` and `ExpnKind::AstPass` (or
subsets, depending on their sub-kinds) as well, but I'm not sure that's
a good idea.

I'd like to add a test of the `Attr` macro on functions, but I need time
to figure out how to constract a good, simple example without external
crate dependencies. For the moment, all tests still work as expected (no
change), this new commit shouldn't have a negative affect, and more
importantly, I believe it will have a positive effect. I will try to
confirm this.
2021-05-06 11:15:39 -07:00
bors 377d1a984c Auto merge of #84559 - jackh726:issue-84398, r=nikomatsakis
Deduplicate ParamCandidates with the same value except for bound vars

Fixes #84398

This is kind of a hack. I wonder if we can get other types of candidates that are the same except for bound vars. This won't be a problem with Chalk, since we don't really need to know that there are two different "candidates" if they both give the same final substitution.

r? `@nikomatsakis`
2021-05-06 17:42:32 +00:00