diff options
| -rw-r--r-- | src/librustc_mir/interpret/eval_context.rs | 37 | ||||
| -rw-r--r-- | src/librustc_mir/interpret/place.rs | 4 |
2 files changed, 23 insertions, 18 deletions
diff --git a/src/librustc_mir/interpret/eval_context.rs b/src/librustc_mir/interpret/eval_context.rs index ce098f583d0..10d3101ebb8 100644 --- a/src/librustc_mir/interpret/eval_context.rs +++ b/src/librustc_mir/interpret/eval_context.rs @@ -18,7 +18,7 @@ use rustc_middle::ty::query::TyCtxtAt; use rustc_middle::ty::subst::SubstsRef; use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable}; use rustc_span::source_map::DUMMY_SP; -use rustc_target::abi::{Align, HasDataLayout, LayoutOf, Size, TargetDataLayout}; +use rustc_target::abi::{Abi, Align, HasDataLayout, LayoutOf, Size, TargetDataLayout}; use super::{ Immediate, MPlaceTy, Machine, MemPlace, MemPlaceMeta, Memory, OpTy, Operand, Place, PlaceTy, @@ -212,20 +212,25 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> LayoutOf for InterpCx<'mir, 'tcx, M> { /// Test if it is valid for a MIR assignment to assign `src`-typed place to `dest`-typed value. /// This test should be symmetric, as it is primarily about layout compatibility. -pub(super) fn mir_assign_valid_types<'tcx>(src: Ty<'tcx>, dest: Ty<'tcx>) -> bool { - src == dest - || match (&src.kind, &dest.kind) { - (ty::Ref(_, src_pointee, _), ty::Ref(_, dest_pointee, _)) => { - // After optimizations, there can be assignments that change reference mutability. - // This does not affect reference layout, so that is fine. - src_pointee == dest_pointee - } - (ty::FnPtr(_), ty::FnPtr(_)) => { - // All function pointers have equal layout, and thus can be assigned. - true - } - _ => false, - } +pub(super) fn mir_assign_valid_types<'tcx>( + src: TyAndLayout<'tcx>, + dest: TyAndLayout<'tcx>, +) -> bool { + if src.ty == dest.ty { + // Equal types, all is good. + return true; + } + // Type-changing assignments can happen for (at least) two reasons: + // - `&mut T` -> `&T` gets optimized from a reborrow to a mere assignment. + // - Subtyping is used. While all normal lifetimes are erased, higher-ranked lifetime + // bounds are still around and can lead to type differences. + // There is no good way to check the latter, so we compare layouts instead -- but only + // for values with `Scalar`/`ScalarPair` abi. + // FIXME: Do something more accurate, type-based. + match &src.abi { + Abi::Scalar(..) | Abi::ScalarPair(..) => src.layout == dest.layout, + _ => false, + } } /// Use the already known layout if given (but sanity check in debug mode), @@ -241,7 +246,7 @@ pub(super) fn from_known_layout<'tcx>( if cfg!(debug_assertions) { let check_layout = compute()?; assert!( - mir_assign_valid_types(check_layout.ty, known_layout.ty), + mir_assign_valid_types(check_layout, known_layout), "expected type differs from actual type.\nexpected: {:?}\nactual: {:?}", known_layout.ty, check_layout.ty, diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs index c9999ef7c95..ec299cdd213 100644 --- a/src/librustc_mir/interpret/place.rs +++ b/src/librustc_mir/interpret/place.rs @@ -868,7 +868,7 @@ where // We do NOT compare the types for equality, because well-typed code can // actually "transmute" `&mut T` to `&T` in an assignment without a cast. assert!( - mir_assign_valid_types(src.layout.ty, dest.layout.ty), + mir_assign_valid_types(src.layout, dest.layout), "type mismatch when copying!\nsrc: {:?},\ndest: {:?}", src.layout.ty, dest.layout.ty, @@ -922,7 +922,7 @@ where src: OpTy<'tcx, M::PointerTag>, dest: PlaceTy<'tcx, M::PointerTag>, ) -> InterpResult<'tcx> { - if mir_assign_valid_types(src.layout.ty, dest.layout.ty) { + if mir_assign_valid_types(src.layout, dest.layout) { // Fast path: Just use normal `copy_op` return self.copy_op(src, dest); } |