Optimize pattern matching
These commits speed up the `match-stress-enum` benchmark, which is very artificial, but the changes are simple enough that it's probably worth doing.
r? `@Nadrieril`
Add test cases for unstable variants
Add test cases for doc hidden variants
Move is_doc_hidden to method on TyCtxt
Add unstable variants test to reachable-patterns ui test
Rename reachable-patterns -> omitted-patterns
Normalize after substituting via `field.ty()`
Back in https://github.com/rust-lang/rust/issues/72476 I hadn't understood where the problem was coming from, and only worked around the issue. What happens is that calling `field.ty()` on a field of a generic struct substitutes the appropriate generics but doesn't normalize the resulting type.
As a consumer of types I'm surprised that one would substitute without normalizing, feels like a footgun, so I added a comment.
Fixes https://github.com/rust-lang/rust/issues/89393.
fix(lint): don't suggest refutable patterns to "fix" irrefutable bind
In function arguments and let bindings, do not suggest changing `C` to `Foo::C` unless `C` is the only variant of `Foo`, because it won't work.
The general warning is still kept, because code like this is confusing.
Fixes#88730
p.s. `src/test/ui/lint/lint-uppercase-variables.rs` already tests the one-variant case.
Use larger span for adjustment THIR expressions
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. These spans are recoded
when we first create the adjustment during typecheck. For
example, an autoref adjustment triggered by a method call
will record the span of the entire method call.
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.
In function arguments and let bindings, do not suggest changing `C` to `Foo::C`
unless `C` is the only variant of `Foo`, because it won't work.
The general warning is still kept, because code like this is confusing.
Fixes#88730
Add an intermediate representation to exhaustiveness checking
The exhaustiveness checking algorithm keeps deconstructing patterns into a `Constructor` and some `Fields`, but does so a bit all over the place. This PR introduces a new representation for patterns that already has that information, so we only compute it once at the start.
I find this makes code easier to follow. In particular `DeconstructedPat::specialize` is a lot simpler than what happened before, and more closely matches the description of the algorithm. I'm also hoping this could help for the project of librarifying exhaustiveness for rust_analyzer since it decouples the algorithm from `rustc_middle::Pat`.
Now `Fields` is just a `Vec` of patterns, with some extra info on the
side to reconstruct patterns when needed. This emphasizes that this
extra info is not central to the algorithm.
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.
Add linting on non_exhaustive structs and enum variants
Add ui tests for non_exhaustive reachable lint
Rename to non_exhaustive_omitted_patterns and avoid triggering on if let
MIR lowering for `if let` expressions is now more complicated now that
`if let` exists in HIR. This PR adds a scope for the variables bound in
an `if let` expression and then uses an approach similar to how we
handle loops to ensure that we reliably drop the correct variables.
Support -Z unpretty=thir-tree again
Currently `-Z unpretty=thir-tree` is broken after some THIR refactorings. This re-implements it, making it easier to debug THIR-related issues.
We have to do analyzes before getting the THIR, since trying to create THIR from invalid HIR can ICE. But doing those analyzes requires the THIR to be built and stolen. We work around this by creating a separate query to construct the THIR tree string representation.
Closes https://github.com/rust-lang/project-thir-unsafeck/issues/8, fixes#85552.
Combine two loops in `check_match`
Suggested by Nadrieril in
https://github.com/rust-lang/rust/pull/79051#discussion_r548778186.
Opening to get a perf run. Hopefully this code doesn't require everything in the
first loop to be done before running the second! (It shouldn't though.)
cc `@Nadrieril`
