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| author | Michael Goulet <michael@errs.io> | 2024-09-23 13:52:02 -0400 |
|---|---|---|
| committer | Michael Goulet <michael@errs.io> | 2024-09-25 11:13:59 -0400 |
| commit | 3209943604a9b3565a3cef4c43b567f65cfdf192 (patch) | |
| tree | 5872a492b6fc7cd3cb477a6f34d41aea5e79e269 /compiler/rustc_mir_transform | |
| parent | 8fc8e03150ed69cc37a3e21b319a4d9bf247292f (diff) | |
| download | rust-3209943604a9b3565a3cef4c43b567f65cfdf192.tar.gz rust-3209943604a9b3565a3cef4c43b567f65cfdf192.zip | |
Add a debug assertion in codegen that unsize casts of the same principal trait def id are truly NOPs
Diffstat (limited to 'compiler/rustc_mir_transform')
| -rw-r--r-- | compiler/rustc_mir_transform/src/validate.rs | 15 |
1 files changed, 0 insertions, 15 deletions
diff --git a/compiler/rustc_mir_transform/src/validate.rs b/compiler/rustc_mir_transform/src/validate.rs index c9a844e4734..e353be6a105 100644 --- a/compiler/rustc_mir_transform/src/validate.rs +++ b/compiler/rustc_mir_transform/src/validate.rs @@ -1233,21 +1233,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> { )) { self.fail(location, format!("Unsize coercion, but `{op_ty}` isn't coercible to `{target_type}`")); } - - // FIXME: Codegen has an additional assumption, where if the - // principal trait def id of what's being casted doesn't change, - // then we don't need to adjust the vtable at all. This - // corresponds to the fact that `dyn Tr<A>: Unsize<dyn Tr<B>>` - // requires that `A = B`; we don't allow *upcasting* objects - // between the same trait with different args. Nothing actually - // validates this, though. While it's true right now, if we for - // some reason were to relax the `Unsize` trait, it could become - // unsound. We should eventually validate that, but it would - // require peeling `&Box<Struct<.., dyn Tr<A>, ..>>` down to - // the trait object that's being unsized, and that's rather - // annoying, and also it would need to be opportunistic since - // this MIR is not yet fully monomorphized, so we may bottom - // out in an alias or a projection or something. } CastKind::PointerCoercion(PointerCoercion::DynStar, _) => { // FIXME(dyn-star): make sure nothing needs to be done here. |