Handle const-checks for &mut outside of HasMutInterior
#66654
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r? @eddyb (although I'd like to work on this a bit more, it's not quite ready) |
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&mut outside of HasMutInterior&mut outside of HasMutInterior
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☔ The latest upstream changes (presumably #66640) made this pull request unmergeable. Please resolve the merge conflicts. |
Centril
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Nov 23, 2019
| fn in_static(_cx: &ConstCx<'_, 'tcx>, _static: &Static<'tcx>) -> bool { | ||
| // FIXME(eddyb) should we do anything here for value properties? | ||
| false | ||
| fn in_static(cx: &ConstCx<'_, 'tcx>, statik: &Static<'tcx>) -> bool { |
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(btw, a doc comment on these methods would be great)
| .as_local() | ||
| .map_or(false, |local| self.derived_from_illegal_borrow.contains(local)); | ||
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| // Don't emit errors for borrows of values that are *themselves* the result of |
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Can we delay_span_bug just in case?
eddyb
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Nov 26, 2019
| // Don't emit errors for borrows of values that are *themselves* the result of | ||
| // an illegal borrow (e.g., the outermost `&` in `&&Cell::new(42)`). We want to | ||
| // point the user to the place where the original illegal borrow occurred, not | ||
| // to subsequent borrows of the resulting value. |
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I thought this was resolved by simply not having any qualifs on &Cell::new(42).
&T is always Freeze + Copy, regardless of T, so no qualif bits need to be set.
The only reason they were before was for promotion, which is why we split promotion into its own check.
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I think you're right. This means I can clean up a lot more!
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☔ The latest upstream changes (presumably #66677) made this pull request unmergeable. Please resolve the merge conflicts. |
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Now, `derived_from_illegal_borrow` is also applied to reborrows, so we don't show the user a useless error message.
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Now that #66640 has been merged, the const-checker treats borrows of a @matthewjasper I'm not quite sure why #66587 didn't cause this test to change. How do I check that |
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I believe it didn't change in that PR because we don't special case reborrows in |
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The |
This error code is never emitted, and the contents of this test are identical to that of `E0017.rs`.
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They now look the same in the MIR after rust-lang#66587.
This checks `static mut` as well for E0017, and blesses tests now that we emit an error for a mut deref.
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@eddyb I had to make a few changes in |
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Nov 28, 2019
| if let LocalInfo::StaticRef { .. } = decl.local_info { | ||
| return None; | ||
| } | ||
| } |
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@matthewjasper isn't this supposed to use a helper method?
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Yes, there's body.local_decls[local].is_ref_to_static
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@matthewjasper Resolved in ccb4eed.
eddyb
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Nov 28, 2019
| | Rvalue::Ref(_, BorrowKind::Shared, ref place) | ||
| | Rvalue::Ref(_, BorrowKind::Shallow, ref place) | ||
| if matches!(place.base, PlaceBase::Static(_)) | ||
| => {} |
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Does this make sense anymore, with the static changes?
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No, this shouldn't be reachable, since the only PlaceBase::Statics are promoted. This maybe should be bug!() for now.
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r? @matthewjasper for all the |
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📌 Commit ccb4eed has been approved by |
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…eddyb,matthewjasper Handle const-checks for `&mut` outside of `HasMutInterior` Addresses [this comment](rust-lang#64470 (comment)). Const-checking relied on `HasMutInterior` to forbid `&mut` in a const context. This was strange because all we needed to do was look for an `Rvalue::Ref` with a certain `BorrowKind`, whereas the `Qualif` traits are specifically meant to get the qualifs for a *value*. This PR removes that logic from `HasMutInterior` and moves it into `check_consts::Validator`. As a result, we can now properly handle qualifications for `static`s, which had to be ignored previously since you can e.g. borrow a static `Cell` from another `static`. We also remove the `derived_from_illegal_borrow` logic, since it is no longer necessary; we give good errors for subsequent reborrows/borrows of illegal borrows.
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Rollup of 5 pull requests Successful merges: - #66245 (Conditional compilation for sanitizers) - #66654 (Handle const-checks for `&mut` outside of `HasMutInterior`) - #66822 (libunwind_panic: adjust miri panic hack) - #66827 (handle diverging functions forwarding their return place) - #66834 (rustbuild fixes) Failed merges: r? @ghost
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Addresses this comment.
Const-checking relied on
HasMutInteriorto forbid&mutin a const context. This was strange because all we needed to do was look for anRvalue::Refwith a certainBorrowKind, whereas theQualiftraits are specifically meant to get the qualifs for a value. This PR removes that logic fromHasMutInteriorand moves it intocheck_consts::Validator.As a result, we can now properly handle qualifications for
statics, which had to be ignored previously since you can e.g. borrow a staticCellfrom anotherstatic. We also remove thederived_from_illegal_borrowlogic, since it is no longer necessary; we give good errors for subsequent reborrows/borrows of illegal borrows.