check_match: don't treat privately uninhabited types as uninhabited #39980
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
arielb1
added
the
beta-nominated
arielb1
force-pushed
the
privately-uninhabited
branch
from
0de44df
to
a84eb95
Compare
|
|
||
| if missing_ctors.is_empty() { | ||
| // | ||
| // However, if our scrutinee is *privately* an empty enum, we |
There was a problem hiding this comment.
Might be worth defining what 'privately empty' means -- I presume it means that the uninhabited values are not visible from this module? I feel like there was logic to this effect before.
| @@ -754,7 +774,19 @@ fn constructor_sub_pattern_tys<'a, 'tcx: 'a>(cx: &MatchCheckCtxt<'a, 'tcx>, | |||
| ty::TyRef(_, ref ty_and_mut) => vec![ty_and_mut.ty], | |||
| ty::TyAdt(adt, substs) => { | |||
| adt.variants[ctor.variant_index_for_adt(adt)].fields.iter().map(|field| { | |||
| field.ty(cx.tcx, substs) | |||
| let is_visible = adt.is_enum() | |||
| || field.vis.is_accessible_from(cx.module, cx.tcx); | |||
There was a problem hiding this comment.
do enum fields not have appropriate visibility settings?
| let pat_ty = self.tables.node_id_to_type(scrut.id); | ||
| let module = self.tcx.hir.local_def_id(self.tcx.hir.get_module_parent(scrut.id)); | ||
| if inlined_arms.is_empty() { | ||
| if !pat_ty.is_uninhabited_from(module, self.tcx) { |
There was a problem hiding this comment.
I think eventually this wants to be a stricter definition of uninhabited (i.e., one that says "you could only write dead-code arms"), but I guess that can come later. Probably so long as never-type feature flag is not in use this one will match what we want.
There was a problem hiding this comment.
Isn't this what we agreed on at the sprint.
|
(The code seems good, in any case.) |
|
In beta. |
This is a [breaking-change] from 1.15, because this used to compile:
```Rust
enum Void {}
fn foo(x: &Void) {
match x {}
}
```
|
@bors r+ |
|
📌 Commit 87e544b has been approved by |
nikomatsakis
added
the
beta-accepted
eddyb
added a commit
to eddyb/rust
that referenced
this pull request
Feb 25, 2017
…komatsakis check_match: don't treat privately uninhabited types as uninhabited Fixes rust-lang#38972, which is a regression in 1.16 from @canndrew's patchset. r? @nikomatsakis beta-nominating because regression.
eddyb
added a commit
to eddyb/rust
that referenced
this pull request
Feb 25, 2017
…komatsakis check_match: don't treat privately uninhabited types as uninhabited Fixes rust-lang#38972, which is a regression in 1.16 from @canndrew's patchset. r? @nikomatsakis beta-nominating because regression.
bors
added a commit
that referenced
this pull request
Feb 25, 2017
Rollup of 28 pull requests - Successful merges: #39859, #39864, #39888, #39903, #39905, #39914, #39945, #39950, #39953, #39961, #39980, #39988, #39993, #39995, #40019, #40020, #40022, #40024, #40025, #40026, #40027, #40031, #40035, #40037, #40038, #40064, #40069, #40086 - Failed merges: #39927, #40008, #40047
Merged
alexcrichton
removed
the
beta-nominated
bors
added a commit
that referenced
this pull request
Mar 2, 2017
[beta] next - #39913 - #39730 - #39674 - #39602 - #39586 - #39471 - #39980 - #40020 - #40135 @nikomatsakis [this commit](3787d33) did not pick cleanly. You might peek at it. I took the liberty of accepting all the nominations myself, but the [packed struct alignment](#39586) PR is quite large. It did pick fine though and there's a comment there suggesting it works on beta cc @rust-lang/compiler. cc @alexcrichton
arielb1
added a commit
to arielb1/rust
that referenced
this pull request
Jan 13, 2018
the match-checking code used to use TyErr for signaling "unknown, inhabited" types for a long time. It had been switched to using the exact type in rust-lang#38069, to handle uninhabited types. However, in rust-lang#39980, we discovered that we still needed the "unknown inhabited" logic, but I used `()` instead of `TyErr` to handle that. Revert to using `TyErr` to fix that problem.
bors
added a commit
that referenced
this pull request
Jan 21, 2018
check_match: fix handling of privately uninhabited types the match-checking code used to use TyErr for signaling "unknown, inhabited" types for a long time. It had been switched to using the exact type in #38069, to handle uninhabited types. However, in #39980, we discovered that we still needed the "unknown inhabited" logic, but I used `()` instead of `TyErr` to handle that. Revert to using `TyErr` to fix that problem. Fixes #46964. r? @nikomatsakis
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fixes #38972, which is a regression in 1.16 from @canndrew's patchset.
r? @nikomatsakis
beta-nominating because regression.