[12/12] On-demand type-checking, const-evaluation, MIR building & const-qualification.
_This is the last of a series ([prev](https://github.com/rust-lang/rust/pull/38813)) of patches designed to rework rustc into an out-of-order on-demand pipeline model for both better feature support (e.g. [MIR-based](https://github.com/solson/miri) early constant evaluation) and incremental execution of compiler passes (e.g. type-checking), with beneficial consequences to IDE support as well.
If any motivation is unclear, please ask for additional PR description clarifications or code comments._
<hr>
As this contains all of the changes that didn't fit neatly into other PRs, I'll be elaborating a bit:
### User-facing changes
* when determining whether an `impl Trait` type implements an auto-trait (e.g. `Send` or `Sync`), the function the `impl Trait` came from has to be inferred and type-checking, disallowing cycles
* this results from not having an obvious place to put the "deferred obligation" in on-demand atm
* while we could model side-effects like that and "post-processing passes" better, it's still more limiting than being able to know the result in the original function (e.g. specialization) *and* there are serious problems around region-checking (if a `Send` impl required `'static`, it wasn't enforced)
* early const-eval requires type-checking and const-qualification to be performed first, which means:
* you get the intended errors before (if any) constant evaluation error that is simply fallout
* associated consts should always work now, and `const fn` type parameters are properly tracked
* don't get too excited, array lengths still can't depend on type parameters
* #38864 works as intended now, with `Self` being allowed in `impl` bounds
* #32205 is largely improved, with associated types being limited to "exact match" `impl`s (as opposed to traversing the specialization graph to resolve unspecified type parameters to their defaults in another `impl` or in the `trait`) *while* checking for overlaps building the specialization graph for that trait - once all the trait impls' have been checked for coherence (including ahead-of-time/on-demand), it's uniform
* [crater report](https://gist.github.com/eddyb/bbb869072468c7e08d6d808e75938051) looks clean (aside from `clippy` which broke due to `rustc` internal changes)
### Compiler-internal changes
* `ty::Generics`
* no longer contains the actual type parameter defaults, instead they're associated with the type parameter's `DefId`, like associated types in a trait definition
* this allows computing `ty::Generics` as a leaf (reading only its own HIR)
* holds a mapping from `DefIndex` of type parameters to their indices
* `ty::AdtDef`
* only tracks `#[repr(simd)]` in its `ReprOptions` `repr` field
* doesn't contain `enum` discriminant values, but instead each variant either refers to either an explicit value for its discriminant, or the distance from the last explicit discriminant, if any
* the `.discriminants(tcx)` method produces an iterator of `ConstInt` values, looking up explicit discriminants in a separate map, if necessary
* this allows computing `ty::AdtDef` as a leaf (reading only its own HIR)
* Small note: the two above (`Generics`, `AdtDef`), `TraitDef` and `AssociatedItem` should probably end up as part of the HIR, eventually, as they're trivially constructed from it
* `ty::FnSig`
* now also holds ABI and unsafety, alongside argument types, return type and C variadicity
* `&ty::BareFnTy` and `ty::ClosureTy` have been replaced with `PolyFnSig = Binder<FnSig>`
* `BareFnTy` was interned and `ClosureTy` was treated as non-trivial to `Clone` because they had a `PolyFnSig` and so used to contain a `Vec<Ty>` (now `&[Ty]`)
* `ty::maps`
* all the `DepTrackingMap`s have been grouped in a structure available at `tcx.maps`
* when creating the `tcx`, a set of `Providers` (one `fn` pointer per map) is required for the local crate, and one for all other crates (i.e. metadata loading), `librustc_driver` plugging the various crates (e.g. `librustc_metadata`, `librustc_typeck`, `librustc_mir`) into it
* when a map is queried and the value is missing, the appropriate `fn` pointer from the `Providers` of that crate is called with the `TyCtxt` and the key being queried, to produce the value on-demand
* `rustc_const_eval`
* demands both `typeck_tables` and `mir_const_qualif` (in preparation for miri)
* tracks `Substs` in `ConstVal::Function` for `const fn` calls
* returns `TypeckError` if type-checking has failed (or cases that can only be reached if it had)
* this error kind is never reported, resulting in less noisy/redundant diagnostics
* fixes#39548 (testcase by @larsluthman, taken from #39812, which this supersedes)
* on-demand has so far been hooked up to:
* `rustc_metadata::cstore_impl`: `ty`, `generics`, `predicates`, `super_predicates`, `trait_def`, `adt_def`, `variances`, `associated_item_def_ids`, `associated_item`, `impl_trait_ref`, `custom_coerce_unsized_kind`, `mir`, `mir_const_qualif`, `typeck_tables`, `closure_kind`, `closure_type`
* `rustc_typeck::collect`: `ty`, `generics`, `predicates`, `super_predicates`, `type_param_predicates`, `trait_def`, `adt_def`, `impl_trait_ref`
* `rustc_typeck::coherence`: `coherent_trait`, `coherent_inherent_impls`
* `rustc_typeck::check`: `typeck_tables`, `closure_type`, `closure_kind`
* `rustc_mir::mir_map`: `mir`
* `rustc_mir::transform::qualify_consts`: `mir_const_qualif`
appveyor: Use sccache on pc-windows-gnu for caching
Now that mozilla/sccache#43 is fixed the caching works for MinGW on Windows. We
still can't use it for MSVC just yet, but I'll try to revive that branch at some
point.
Now that mozilla/sccache#43 is fixed the caching works for MinGW on Windows. We
still can't use it for MSVC just yet, but I'll try to revive that branch at some
point.
Improve backtrace formating while panicking.
Fixes#37783.
Done:
- Fix alignment of file paths for better readability
- `RUST_BACKTRACE=full` prints all the informations (current behaviour)
- `RUST_BACKTRACE=(short|yes)` is the default and does:
- Skip irrelevant frames at the beginning and the end
- Remove function address
- Remove the current directory from the absolute paths
- Remove `::hfabe6541873` at the end of the symbols
- `RUST_BACKTRACE=(0|no)` disables the backtrace.
- `RUST_BACKTRACE=<everything else>` is equivalent to `short` for
backward compatibility.
- doc
- More uniform printing across platforms.
Removed, TODO in a new PR:
- Remove path prefix for libraries and libstd
Example of short backtrace:
```rust
fn fail() {
panic!();
}
fn main() {
let closure = || fail();
closure();
}
```
Short:
```
thread 'main' panicked at 'explicit panic', t.rs:2
Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
0: t::fail
at ./t.rs:2
1: t::main::{{closure}}
at ./t.rs:6
2: t::main
at ./t.rs:7
```
Full:
```
thread 'main' panicked at 'This function never returns!', t.rs:2
stack backtrace:
0: 0x558ddf666478 - std::sys:👿:backtrace::tracing:👿:unwind_backtrace::hec84c9dd8389cc5d
at /home/yamakaky/dev/rust/rust/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
1: 0x558ddf65d90e - std::sys_common::backtrace::_print::hfa25f8b31f4b4353
at /home/yamakaky/dev/rust/rust/src/libstd/sys_common/backtrace.rs:71
2: 0x558ddf65cb5e - std::sys_common::backtrace::print::h9b711e11ac3ba805
at /home/yamakaky/dev/rust/rust/src/libstd/sys_common/backtrace.rs:60
3: 0x558ddf66796e - std::panicking::default_hook::{{closure}}::h736d216e74748044
at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:355
4: 0x558ddf66743c - std::panicking::default_hook::h16baff397e46ea10
at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:371
5: 0x558ddf6682bc - std::panicking::rust_panic_with_hook::h6d5a9bb4eca42c80
at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:559
6: 0x558ddf64ea93 - std::panicking::begin_panic::h17dc549df2f10b99
at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:521
7: 0x558ddf64ec42 - t::diverges::he6bc43fc925905f5
at /tmp/p/t.rs:2
8: 0x558ddf64ec5a - t::main::h0ffc20356b8a69c0
at /tmp/p/t.rs:6
9: 0x558ddf6687f5 - core::ops::FnOnce::call_once::hce41f19c0db56f93
10: 0x558ddf667cde - std::panicking::try::do_call::hd4c8c97efb4291df
at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:464
11: 0x558ddf698d77 - __rust_try
12: 0x558ddf698c57 - __rust_maybe_catch_panic
at /home/yamakaky/dev/rust/rust/src/libpanic_unwind/lib.rs:98
13: 0x558ddf667adb - std::panicking::try::h2c56ed2a59ec1d12
at /home/yamakaky/dev/rust/rust/src/libstd/panicking.rs:440
14: 0x558ddf66cc9a - std::panic::catch_unwind::h390834e0251cc9af
at /home/yamakaky/dev/rust/rust/src/libstd/panic.rs:361
15: 0x558ddf6809ee - std::rt::lang_start::hb73087428e233982
at /home/yamakaky/dev/rust/rust/src/libstd/rt.rs:57
16: 0x558ddf64ec92 - main
17: 0x7fecb869e290 - __libc_start_main
18: 0x558ddf64e8b9 - _start
19: 0x0 - <unknown>
```
Loop docs: Present perfect instead of simple past
Sounds better with present perfect because there's a link to the present.
I'm not a native speaker, though. So, plz check whether it really is better ;)
r? @steveklabnik
doc: Use "macOS" terminology consistently
One line in the documentation used the term macOS while the other six used OSX. Be consistent and use the current product brand of macOS.
travis: Make more network requests retryable
This commit attempts to move more network operations to being retryable through
various operations. For example git submodule updates, downloading snapshots,
etc, are now all in retryable steps.
Hopefully this commit can cut down on the number of network failures we've been
seeing!
This commit attempts to move more network operations to being retryable through
various operations. For example git submodule updates, downloading snapshots,
etc, are now all in retryable steps.
Hopefully this commit can cut down on the number of network failures we've been
seeing!
Add Gankro's table to nomicon/src/phantom-data.md
Original: https://github.com/rust-lang/rust/issues/30069#issuecomment-159928136
Testing confirms that:
- `PhantomData<fn() -> T>` does not actually enable drop checking.
- `PhantomData<fn(T) -> T>` is neither variant nor contravariant.
trans: don't ICE when trying to create ADT trans-items
ADTs are translated in-place from rustc_trans::callee, so no trans-items
are needed.
This fix will be superseded by the shimmir branch, but I prefer not to
backport that to beta.
Fixes#39823.
Beta-nominating because regression.
r? @michaelwoerister
