Commit Graph

530 Commits

Author SHA1 Message Date
bors
03a8cc7df1 Auto merge of #93505 - lcnr:substsref-vs-ty-list, r=michaelwoerister
safely `transmute<&List<Ty<'tcx>>, &List<GenericArg<'tcx>>>`

This PR has 3 relevant steps which are is split in distinct commits.

The first commit now interns `List<Ty<'tcx>>` and `List<GenericArg<'tcx>>` together, potentially reusing memory while allowing free conversions between these two using `List<Ty<'tcx>>::as_substs()` and `SubstsRef<'tcx>::try_as_type_list()`.

Using this, we then use `&'tcx List<Ty<'tcx>>` instead of a `SubstsRef<'tcx>` for tuple fields, simplifying a bunch of code.

Finally, as tuple fields and other generic arguments now use a different `TypeFoldable<'tcx>` impl, we optimize the impl for `List<Ty<'tcx>>` improving perf by slightly less than 1% in tuple heavy benchmarks.
2022-02-21 16:03:38 +00:00
lcnr
1245131a11 use List<Ty<'tcx>> for tuples 2022-02-21 07:09:11 +01:00
Mark Rousskov
9f76214854 Revert "Auto merge of #93800 - b-naber:static-initializers-mir-val, r=oli-obk"
This reverts commit a240ccd81c, reversing
changes made to 393fdc1048.

This PR was likely responsible for a relatively large regression in
dist-x86_64-msvc-alt builder times, from approximately 1.7 to 2.8 hours,
bringing that builder into the pool of the slowest builders we currently have.

This seems to be limited to the alt builder due to needing parallel-compiler
enabled, likely leading to slow LLVM compilation for some reason.
2022-02-20 21:56:20 -05:00
bors
45e2c2881d Auto merge of #93678 - steffahn:better_unsafe_diagnostics, r=nagisa
Improve `unused_unsafe` lint

I’m going to add some motivation and explanation below, particularly pointing the changes in behavior from this PR.

_Edit:_ Looking for existing issues, looks like this PR fixes #88260.

_Edit2:_ Now also contains code that closes #90776.
2022-02-20 21:15:11 +00:00
Frank Steffahn
8f8689fb31 Improve unused_unsafe lint
Main motivation: Fixes some issues with the current behavior. This PR is
more-or-less completely re-implementing the unused_unsafe lint; it’s also only
done in the MIR-version of the lint, the set of tests for the `-Zthir-unsafeck`
version no longer succeeds (and is thus disabled, see `lint-unused-unsafe.rs`).

On current nightly,
```rs
unsafe fn unsf() {}

fn inner_ignored() {
    unsafe {
        #[allow(unused_unsafe)]
        unsafe {
            unsf()
        }
    }
}
```

doesn’t create any warnings. This situation is not unrealistic to come by, the
inner `unsafe` block could e.g. come from a macro. Actually, this PR even
includes removal of one unused `unsafe` in the standard library that was missed
in a similar situation. (The inner `unsafe` coming from an external macro hides
    the warning, too.)

The reason behind this problem is how the check currently works:
* While generating MIR, it already skips nested unsafe blocks (i.e. unsafe
  nested in other unsafe) so that the inner one is always the one considered
  unused
* To differentiate the cases of no unsafe operations inside the `unsafe` vs.
  a surrounding `unsafe` block, there’s some ad-hoc magic walking up the HIR to
  look for surrounding used `unsafe` blocks.

There’s a lot of problems with this approach besides the one presented above.
E.g. the MIR-building uses checks for `unsafe_op_in_unsafe_fn` lint to decide
early whether or not `unsafe` blocks in an `unsafe fn` are redundant and ought
to be removed.
```rs
unsafe fn granular_disallow_op_in_unsafe_fn() {
    unsafe {
        #[deny(unsafe_op_in_unsafe_fn)]
        {
            unsf();
        }
    }
}
```
```
error: call to unsafe function is unsafe and requires unsafe block (error E0133)
  --> src/main.rs:13:13
   |
13 |             unsf();
   |             ^^^^^^ call to unsafe function
   |
note: the lint level is defined here
  --> src/main.rs:11:16
   |
11 |         #[deny(unsafe_op_in_unsafe_fn)]
   |                ^^^^^^^^^^^^^^^^^^^^^^
   = note: consult the function's documentation for information on how to avoid undefined behavior

warning: unnecessary `unsafe` block
  --> src/main.rs:10:5
   |
9  | unsafe fn granular_disallow_op_in_unsafe_fn() {
   | --------------------------------------------- because it's nested under this `unsafe` fn
10 |     unsafe {
   |     ^^^^^^ unnecessary `unsafe` block
   |
   = note: `#[warn(unused_unsafe)]` on by default

```
Here, the intermediate `unsafe` was ignored, even though it contains a unsafe
operation that is not allowed to happen in an `unsafe fn` without an additional `unsafe` block.

Also closures were problematic and the workaround/algorithms used on current
nightly didn’t work properly. (I skipped trying to fully understand what it was
supposed to do, because this PR uses a completely different approach.)
```rs
fn nested() {
    unsafe {
        unsafe { unsf() }
    }
}
```
```
warning: unnecessary `unsafe` block
  --> src/main.rs:10:9
   |
9  |     unsafe {
   |     ------ because it's nested under this `unsafe` block
10 |         unsafe { unsf() }
   |         ^^^^^^ unnecessary `unsafe` block
   |
   = note: `#[warn(unused_unsafe)]` on by default
```

vs

```rs
fn nested() {
    let _ = || unsafe {
        let _ = || unsafe { unsf() };
    };
}
```
```
warning: unnecessary `unsafe` block
 --> src/main.rs:9:16
  |
9 |     let _ = || unsafe {
  |                ^^^^^^ unnecessary `unsafe` block
  |
  = note: `#[warn(unused_unsafe)]` on by default

warning: unnecessary `unsafe` block
  --> src/main.rs:10:20
   |
10 |         let _ = || unsafe { unsf() };
   |                    ^^^^^^ unnecessary `unsafe` block
```

*note that this warning kind-of suggests that **both** unsafe blocks are redundant*

--------------------------------------------------------------------------------

I also dislike the fact that it always suggests keeping the outermost `unsafe`.
E.g. for
```rs
fn granularity() {
    unsafe {
        unsafe { unsf() }
        unsafe { unsf() }
        unsafe { unsf() }
    }
}
```
I prefer if `rustc` suggests removing the more-course outer-level `unsafe`
instead of the fine-grained inner `unsafe` blocks, which it currently does on nightly:
```
warning: unnecessary `unsafe` block
  --> src/main.rs:10:9
   |
9  |     unsafe {
   |     ------ because it's nested under this `unsafe` block
10 |         unsafe { unsf() }
   |         ^^^^^^ unnecessary `unsafe` block
   |
   = note: `#[warn(unused_unsafe)]` on by default

warning: unnecessary `unsafe` block
  --> src/main.rs:11:9
   |
9  |     unsafe {
   |     ------ because it's nested under this `unsafe` block
10 |         unsafe { unsf() }
11 |         unsafe { unsf() }
   |         ^^^^^^ unnecessary `unsafe` block

warning: unnecessary `unsafe` block
  --> src/main.rs:12:9
   |
9  |     unsafe {
   |     ------ because it's nested under this `unsafe` block
...
12 |         unsafe { unsf() }
   |         ^^^^^^ unnecessary `unsafe` block
```

--------------------------------------------------------------------------------

Needless to say, this PR addresses all these points. For context, as far as my
understanding goes, the main advantage of skipping inner unsafe blocks was that
a test case like
```rs
fn top_level_used() {
    unsafe {
        unsf();
        unsafe { unsf() }
        unsafe { unsf() }
        unsafe { unsf() }
    }
}
```
should generate some warning because there’s redundant nested `unsafe`, however
every single `unsafe` block _does_ contain some statement that uses it. Of course
this PR doesn’t aim change the warnings on this kind of code example, because
the current behavior, warning on all the inner `unsafe` blocks, makes sense in this case.

As mentioned, during MIR building all the unsafe blocks *are* kept now, and usage
is attributed to them. The way to still generate a warning like
```
warning: unnecessary `unsafe` block
  --> src/main.rs:11:9
   |
9  |     unsafe {
   |     ------ because it's nested under this `unsafe` block
10 |         unsf();
11 |         unsafe { unsf() }
   |         ^^^^^^ unnecessary `unsafe` block
   |
   = note: `#[warn(unused_unsafe)]` on by default

warning: unnecessary `unsafe` block
  --> src/main.rs:12:9
   |
9  |     unsafe {
   |     ------ because it's nested under this `unsafe` block
...
12 |         unsafe { unsf() }
   |         ^^^^^^ unnecessary `unsafe` block

warning: unnecessary `unsafe` block
  --> src/main.rs:13:9
   |
9  |     unsafe {
   |     ------ because it's nested under this `unsafe` block
...
13 |         unsafe { unsf() }
   |         ^^^^^^ unnecessary `unsafe` block
```

in this case is by emitting a `unused_unsafe` warning for all of the `unsafe`
blocks that are _within a **used** unsafe block_.

The previous code had a little HIR traversal already anyways to collect a set of
all the unsafe blocks (in order to afterwards determine which ones are unused
afterwards). This PR uses such a traversal to do additional things including logic
like _always_ warn for an `unsafe` block that’s inside of another **used**
unsafe block. The traversal is expanded to include nested closures in the same go,
this simplifies a lot of things.

The whole logic around `unsafe_op_in_unsafe_fn` is a little complicated, there’s
some test cases of corner-cases in this PR. (The implementation involves
differentiating between whether a used unsafe block was used exclusively by
operations where `allow(unsafe_op_in_unsafe_fn)` was active.) The main goal was
to make sure that code should compile successfully if all the `unused_unsafe`-warnings
are addressed _simultaneously_ (by removing the respective `unsafe` blocks)
no matter how complicated the patterns of `unsafe_op_in_unsafe_fn` being
disallowed and allowed throughout the function are.

--------------------------------------------------------------------------------

One noteworthy design decision I took here: An `unsafe` block
with `allow(unused_unsafe)` **is considered used** for the purposes of
linting about redundant contained unsafe blocks. So while
```rs

fn granularity() {
    unsafe { //~ ERROR: unnecessary `unsafe` block
        unsafe { unsf() }
        unsafe { unsf() }
        unsafe { unsf() }
    }
}
```
warns for the outer `unsafe` block,
```rs

fn top_level_ignored() {
    #[allow(unused_unsafe)]
    unsafe {
        #[deny(unused_unsafe)]
        {
            unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block
            unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block
            unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block
        }
    }
}
```
warns on the inner ones.
2022-02-20 21:00:12 +01:00
bors
523a1b1d38 Auto merge of #94062 - Mark-Simulacrum:drop-print-cfg, r=oli-obk
Move ty::print methods to Drop-based scope guards

Primary goal is reducing codegen of the TLS access for each closure, which shaves ~3 seconds of bootstrap time over rustc as a whole.
2022-02-20 18:12:59 +00:00
est31
2ef8af6619 Adopt let else in more places 2022-02-19 17:27:43 +01:00
Mark Rousskov
9763486034 Move ty::print methods to Drop-based scope guards 2022-02-16 17:24:23 -05:00
b-naber
fff06e5edc use AllocId and Ty in ExprKind::StaticRef and delay ConstValue construction 2022-02-15 21:18:33 +01:00
b-naber
5e0fab6da5 use ConstantKind::Val in StaticRef 2022-02-15 21:10:42 +01:00
Nicholas Nethercote
a95fb8b150 Overhaul Const.
Specifically, rename the `Const` struct as `ConstS` and re-introduce `Const` as
this:
```
pub struct Const<'tcx>(&'tcx Interned<ConstS>);
```
This now matches `Ty` and `Predicate` more closely, including using
pointer-based `eq` and `hash`.

Notable changes:
- `mk_const` now takes a `ConstS`.
- `Const` was copy, despite being 48 bytes. Now `ConstS` is not, so need a
  we need separate arena for it, because we can't use the `Dropless` one any
  more.
- Many `&'tcx Const<'tcx>`/`&Const<'tcx>` to `Const<'tcx>` changes
- Many `ct.ty` to `ct.ty()` and `ct.val` to `ct.val()` changes.
- Lots of tedious sigil fiddling.
2022-02-15 16:19:59 +11:00
Nicholas Nethercote
7024dc523a Overhaul RegionKind and Region.
Specifically, change `Region` from this:
```
pub type Region<'tcx> = &'tcx RegionKind;
```
to this:
```
pub struct Region<'tcx>(&'tcx Interned<RegionKind>);
```

This now matches `Ty` and `Predicate` more closely.

Things to note
- Regions have always been interned, but we haven't been using pointer-based
  `Eq` and `Hash`. This is now happening.
- I chose to impl `Deref` for `Region` because it makes pattern matching a lot
  nicer, and `Region` can be viewed as just a smart wrapper for `RegionKind`.
- Various methods are moved from `RegionKind` to `Region`.
- There is a lot of tedious sigil changes.
- A couple of types like `HighlightBuilder`, `RegionHighlightMode` now have a
  `'tcx` lifetime because they hold a `Ty<'tcx>`, so they can call `mk_region`.
- A couple of test outputs change slightly, I'm not sure why, but the new
  outputs are a little better.
2022-02-15 16:08:52 +11:00
Nicholas Nethercote
e9a0c429c5 Overhaul TyS and Ty.
Specifically, change `Ty` from this:
```
pub type Ty<'tcx> = &'tcx TyS<'tcx>;
```
to this
```
pub struct Ty<'tcx>(Interned<'tcx, TyS<'tcx>>);
```
There are two benefits to this.
- It's now a first class type, so we can define methods on it. This
  means we can move a lot of methods away from `TyS`, leaving `TyS` as a
  barely-used type, which is appropriate given that it's not meant to
  be used directly.
- The uniqueness requirement is now explicit, via the `Interned` type.
  E.g. the pointer-based `Eq` and `Hash` comes from `Interned`, rather
  than via `TyS`, which wasn't obvious at all.

Much of this commit is boring churn. The interesting changes are in
these files:
- compiler/rustc_middle/src/arena.rs
- compiler/rustc_middle/src/mir/visit.rs
- compiler/rustc_middle/src/ty/context.rs
- compiler/rustc_middle/src/ty/mod.rs

Specifically:
- Most mentions of `TyS` are removed. It's very much a dumb struct now;
  `Ty` has all the smarts.
- `TyS` now has `crate` visibility instead of `pub`.
- `TyS::make_for_test` is removed in favour of the static `BOOL_TY`,
  which just works better with the new structure.
- The `Eq`/`Ord`/`Hash` impls are removed from `TyS`. `Interned`s impls
  of `Eq`/`Hash` now suffice. `Ord` is now partly on `Interned`
  (pointer-based, for the `Equal` case) and partly on `TyS`
  (contents-based, for the other cases).
- There are many tedious sigil adjustments, i.e. adding or removing `*`
  or `&`. They seem to be unavoidable.
2022-02-15 16:03:24 +11:00
Ellen
e81e09a24e change to a struct variant 2022-02-12 11:23:53 +00:00
Michael Goulet
a431174c23 add tainted_by_errors to mir::Body 2022-02-11 12:45:51 -08:00
Oli Scherer
d54195db22 Revert "Auto merge of #92007 - oli-obk:lazy_tait2, r=nikomatsakis"
This reverts commit e7cc3bddbe, reversing
changes made to 734368a200.
2022-02-11 07:18:06 +00:00
Camille GILLOT
6c2ee885e6 Ensure that queries only return Copy types. 2022-02-09 20:07:38 +01:00
bors
e7cc3bddbe Auto merge of #92007 - oli-obk:lazy_tait2, r=nikomatsakis
Lazy type-alias-impl-trait

Previously opaque types were processed by

1. replacing all mentions of them with inference variables
2. memorizing these inference variables in a side-table
3. at the end of typeck, resolve the inference variables in the side table and use the resolved type as the hidden type of the opaque type

This worked okayish for `impl Trait` in return position, but required lots of roundabout type inference hacks and processing.

This PR instead stops this process of replacing opaque types with inference variables, and just keeps the opaque types around.
Whenever an opaque type `O` is compared with another type `T`, we make the comparison succeed and record `T` as the hidden type. If `O` is compared to `U` while there is a recorded hidden type for it, we grab the recorded type (`T`) and compare that against `U`. This makes implementing

* https://github.com/rust-lang/rfcs/pull/2515

much simpler (previous attempts on the inference based scheme were very prone to ICEs and general misbehaviour that was not explainable except by random implementation defined oddities).

r? `@nikomatsakis`

fixes #93411
fixes #88236
2022-02-07 23:40:26 +00:00
Yuki Okushi
7712dfd46e
Rollup merge of #93589 - est31:option_then, r=cjgillot
Use Option::then in two places
2022-02-03 22:20:27 +09:00
est31
670f5c6ef3 More let_else adoptions 2022-02-02 17:11:01 +01:00
Oli Scherer
0f6e06b7c0 Lazily resolve type-alias-impl-trait defining uses
by using an opaque type obligation to bubble up comparisons between opaque types and other types

Also uses proper obligation causes so that the body id works, because out of some reason nll uses body ids for logic instead of just diagnostics.
2022-02-02 15:40:11 +00:00
est31
08be313feb Use Option::then in two places 2022-02-02 16:10:16 +01:00
lcnr
a1a30f7548 add a rustc::query_stability lint 2022-02-01 10:15:59 +01:00
Tomasz Miąsko
35b5daaaf8 Check the number of arguments first in is_recursive_call 2022-01-29 23:00:54 +01:00
Tomasz Miąsko
10b722cc79 Ignore unwinding edges when checking for unconditional recursion
The unconditional recursion lint determines if all execution paths
eventually lead to a self-recursive call.

The implementation always follows unwinding edges which limits its
practical utility. For example, it would not lint function `f` because a
call to `g` might unwind. It also wouldn't lint function `h` because an
overflow check preceding the self-recursive call might unwind:

```rust
pub fn f() {
    g();
    f();
}

pub fn g() { /* ... */ }

pub fn h(a: usize) {
  h(a + 1);
}
```

To avoid the issue, assume that terminators that might continue
execution along non-unwinding edges do so.
2022-01-26 13:46:01 +01:00
Matthias Krüger
ab19d4a515
Rollup merge of #93046 - est31:let_else, r=davidtwco
Use let_else in even more places

Followup of #89933, #91018, #91481.
2022-01-21 22:03:17 +01:00
Cameron Steffen
b11733534d Remove a span from hir::ExprKind::MethodCall 2022-01-21 07:48:10 -06:00
Caio
5f74ef4fb1 Formally implement let chains 2022-01-18 19:38:17 -03:00
est31
b2dd1377c7 Use let_else in even more places 2022-01-18 21:37:57 +01:00
bors
ee5d8d37ba Auto merge of #90986 - camsteffen:nested-filter, r=cjgillot
Replace `NestedVisitorMap` with generic `NestedFilter`

This is an attempt to make the `intravisit::Visitor` API simpler and "more const" with regard to nested visiting.

With this change, `intravisit::Visitor` does not visit nested things by default, unless you specify `type NestedFilter = nested_filter::OnlyBodies` (or `All`). `nested_visit_map` returns `Self::Map` instead of `NestedVisitorMap<Self::Map>`. It panics by default (unreachable if `type NestedFilter` is omitted).

One somewhat trixty thing here is that `nested_filter::{OnlyBodies, All}` live in `rustc_middle` so that they may have `type Map = map::Map` and so that `impl Visitor`s never need to specify `type Map` - it has a default of `Self::NestedFilter::Map`.
2022-01-17 14:50:50 +00:00
bors
a34c079752 Auto merge of #92816 - tmiasko:rm-llvm-asm, r=Amanieu
Remove deprecated LLVM-style inline assembly

The `llvm_asm!` was deprecated back in #87590 1.56.0, with intention to remove
it once `asm!` was stabilized, which already happened in #91728 1.59.0. Now it
is time to remove `llvm_asm!` to avoid continued maintenance cost.

Closes #70173.
Closes #92794.
Closes #87612.
Closes #82065.

cc `@rust-lang/wg-inline-asm`

r? `@Amanieu`
2022-01-17 09:40:29 +00:00
Cameron Steffen
45db716902 Replace NestedVisitorMap with NestedFilter 2022-01-16 16:02:36 -06:00
bors
7be8693984 Auto merge of #92805 - BoxyUwU:revert-lazy-anon-const-substs, r=lcnr
partially revertish `lazily "compute" anon const default substs`

reverts #87280 except for some of the changes around `ty::Unevaluated` having a visitor and a generic for promoted
why revert: <https://github.com/rust-lang/rust/pull/92805#issuecomment-1010736049>

r? `@lcnr`
2022-01-16 11:19:21 +00:00
Camille GILLOT
67727aa7c3 Reduce use of local_def_id_to_hir_id. 2022-01-15 21:26:25 +01:00
Ellen
dec8ed438c attempt to re-add ty::Unevaluated visitor and friends 2022-01-15 01:16:55 +00:00
Ellen
71bbb603f4 initial revert 2022-01-15 01:16:55 +00:00
bors
22e491ac7e Auto merge of #89861 - nbdd0121:closure, r=wesleywiser
Closure capture cleanup & refactor

Follow up of #89648

Each commit is self-contained and the rationale/changes are documented in the commit message, so it's advisable to review commit by commit.

The code is significantly cleaner (at least IMO), but that could have some perf implication, so I'd suggest a perf run.

r? `@wesleywiser`
cc `@arora-aman`
2022-01-13 18:51:07 +00:00
Tomasz Miąsko
000b36c505 Remove deprecated LLVM-style inline assembly 2022-01-12 18:51:31 +01:00
Aaron Hill
450ef8613c
Store a Symbol instead of an Ident in VariantDef/FieldDef
The field is also renamed from `ident` to `name. In most cases,
we don't actually need the `Span`. A new `ident` method is added
to `VariantDef` and `FieldDef`, which constructs the full `Ident`
using `tcx.def_ident_span()`. This method is used in the cases
where we actually need an `Ident`.

This makes incremental compilation properly track changes
to the `Span`, without all of the invalidations caused by storing
a `Span` directly via an `Ident`.
2022-01-11 10:16:22 -05:00
Gary Guo
48258ffe5a Remove region from UpvarCapture and move it to CapturedPlace
Region info is completely unnecessary for upvar capture kind computation
and is only needed to create the final upvar tuple ty. Doing so makes
creation of UpvarCapture very cheap and expose further cleanup opportunity.
2022-01-07 22:55:34 +00:00
Gary Guo
3698e03fb6 Remove span from UpvarCapture::ByValue
This span is unused and is superseded by capture_kind_expr_id in CaptureInfo
2022-01-07 22:54:28 +00:00
Matthias Krüger
ac7a867715
Rollup merge of #91907 - lcnr:const-arg-infer, r=BoxyUwU
Allow `_` as the length of array types and repeat expressions

r? `@BoxyUwU` cc `@varkor`
2022-01-04 21:23:06 +01:00
lcnr
e3f5cc6c38 implement generic_arg_infer for array lengths 2021-12-23 10:09:35 +01:00
Aaron Hill
cac431ba75
Store a DefId instead of an AdtDef in AggregateKind::Adt
The `AggregateKind` enum ends up in the final mir `Body`. Currently,
any changes to `AdtDef` (regardless of how significant they are)
will legitimately cause the overall result of `optimized_mir` to change,
invalidating any codegen re-use involving that mir.

This will get worse once we start hashing the `Span` inside `FieldDef`
(which is itself contained in `AdtDef`).

To try to reduce these kinds of invalidations, this commit changes
`AggregateKind::Adt` to store just the `DefId`, instead of the full
`AdtDef`. This allows the result of `optimized_mir` to be unchanged
if the `AdtDef` changes in a way that doesn't actually affect any
of the MIR we build.
2021-12-22 14:36:34 -05:00
Matthias Krüger
c088e5092b
Rollup merge of #91791 - terrarier2111:fix-float-ice, r=nagisa
Fix an ICE when lowering a float with missing exponent magnitude

This fixes: https://github.com/rust-lang/rust/issues/91434
2021-12-19 17:38:33 +01:00
threadexception
0003280b9b Fix an ICE when lowering a float with missing exponent magnitude
Co-authored-by: Simonas Kazlauskas <github@kazlauskas.me>
2021-12-19 11:52:33 +01:00
bors
dde825db46 Auto merge of #89841 - cormacrelf:let-else-typed, r=nagisa
Implement let-else type annotations natively

Tracking issue: #87335

Fixes #89688, fixes #89807, edit: fixes  #89960 as well

As explained in https://github.com/rust-lang/rust/issues/89688#issuecomment-940405082, the previous desugaring moved the let-else scrutinee into a dummy variable, which meant if you wanted to refer to it again in the else block, it had moved.

This introduces a new hir type, ~~`hir::LetExpr`~~ `hir::Let`, which takes over all the fields of `hir::ExprKind::Let(...)` and adds an optional type annotation. The `hir::Let` is then treated like a `hir::Local` when type checking a function body, specifically:

* `GatherLocalsVisitor` overrides a new `Visitor::visit_let_expr` and does pretty much exactly what it does for `visit_local`, assigning a local type to the `hir::Let` ~~(they could be deduplicated but they are right next to each other, so at least we know they're the same)~~
* It reuses the code in `check_decl_local` to typecheck the `hir::Let`, simply returning 'bool' for the expression type after doing that.

* ~~`FnCtxt::check_expr_let` passes this local type in to `demand_scrutinee_type`, and then imitates check_decl_local's pattern checking~~
* ~~`demand_scrutinee_type` (the blindest change for me, please give this extra scrutiny) uses this local type instead of of creating a new one~~
    * ~~Just realised the `check_expr_with_needs` was passing NoExpectation further down, need to pass the type there too. And apparently this Expectation API already exists.~~

Some other misc notes:

* ~~Is the clippy code supposed to be autoformatted? I tried not to give huge diffs but maybe some rustfmt changes simply haven't hit it yet.~~
* in `rustc_ast_lowering/src/block.rs`, I noticed some existing `self.alias_attrs()` calls in `LoweringContext::lower_stmts` seem to be copying attributes from the lowered locals/etc to the statements. Is that right? I'm new at this, I don't know.
2021-12-17 22:12:34 +00:00
PFPoitras
304ede6bcc Stabilize iter::zip. 2021-12-14 18:50:31 -04:00
Cormac Relf
af2f0e6b7c let-else: add hir::Let and type check it like a hir::Local
unify typeck of hir::Local and hir::Let
remove extraneous pub(crate/super)
2021-12-13 14:02:19 +11:00
Gary Guo
2a95958248 Evaluate inline const pat early and report error if too generic 2021-12-05 21:38:37 +00:00