diff options
4 files changed, 99 insertions, 20 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs index e9e65336299..d01c6bac296 100644 --- a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs +++ b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs @@ -25,15 +25,13 @@ use crate::traits::ObligationCtxt; #[instrument(skip(infcx), level = "debug")] pub fn is_const_evaluatable<'tcx>( infcx: &InferCtxt<'tcx>, - ct: ty::Const<'tcx>, + unexpanded_ct: ty::Const<'tcx>, param_env: ty::ParamEnv<'tcx>, span: Span, ) -> Result<(), NotConstEvaluatable> { let tcx = infcx.tcx; - let uv = match ct.kind() { - ty::ConstKind::Unevaluated(uv) => uv, - // FIXME(generic_const_exprs): this seems wrong but I couldn't find a way to get this to trigger - ty::ConstKind::Expr(_) => bug!("unexpected expr in `is_const_evaluatable: {ct:?}"), + match unexpanded_ct.kind() { + ty::ConstKind::Unevaluated(_) | ty::ConstKind::Expr(_) => (), ty::ConstKind::Param(_) | ty::ConstKind::Bound(_, _) | ty::ConstKind::Placeholder(_) @@ -43,7 +41,7 @@ pub fn is_const_evaluatable<'tcx>( }; if tcx.features().generic_const_exprs { - let ct = tcx.expand_abstract_consts(ct); + let ct = tcx.expand_abstract_consts(unexpanded_ct); let is_anon_ct = if let ty::ConstKind::Unevaluated(uv) = ct.kind() { tcx.def_kind(uv.def.did) == DefKind::AnonConst @@ -62,18 +60,40 @@ pub fn is_const_evaluatable<'tcx>( } } - let concrete = infcx.const_eval_resolve(param_env, uv, Some(span)); - match concrete { - Err(ErrorHandled::TooGeneric) => Err(NotConstEvaluatable::Error( - infcx - .tcx - .sess - .delay_span_bug(span, "Missing value for constant, but no error reported?"), - )), - Err(ErrorHandled::Reported(e)) => Err(NotConstEvaluatable::Error(e)), - Ok(_) => Ok(()), + match unexpanded_ct.kind() { + ty::ConstKind::Expr(_) => { + // FIXME(generic_const_exprs): we have a `ConstKind::Expr` which is fully concrete, but + // currently it is not possible to evaluate `ConstKind::Expr` so we are unable to tell if it + // is evaluatable or not. For now we just ICE until this is implemented this. + Err(NotConstEvaluatable::Error(tcx.sess.delay_span_bug( + span, + "evaluating `ConstKind::Expr` is not currently supported", + ))) + } + ty::ConstKind::Unevaluated(uv) => { + let concrete = infcx.const_eval_resolve(param_env, uv, Some(span)); + match concrete { + Err(ErrorHandled::TooGeneric) => { + Err(NotConstEvaluatable::Error(infcx.tcx.sess.delay_span_bug( + span, + "Missing value for constant, but no error reported?", + ))) + } + Err(ErrorHandled::Reported(e)) => Err(NotConstEvaluatable::Error(e)), + Ok(_) => Ok(()), + } + } + _ => bug!("unexpected constkind in `is_const_evalautable: {unexpanded_ct:?}`"), } } else { + let uv = match unexpanded_ct.kind() { + ty::ConstKind::Unevaluated(uv) => uv, + ty::ConstKind::Expr(_) => { + bug!("`ConstKind::Expr` without `feature(generic_const_exprs)` enabled") + } + _ => bug!("unexpected constkind in `is_const_evalautable: {unexpanded_ct:?}`"), + }; + // FIXME: We should only try to evaluate a given constant here if it is fully concrete // as we don't want to allow things like `[u8; std::mem::size_of::<*mut T>()]`. // @@ -92,7 +112,7 @@ pub fn is_const_evaluatable<'tcx>( && satisfied_from_param_env( tcx, infcx, - tcx.expand_abstract_consts(ct), + tcx.expand_abstract_consts(unexpanded_ct), param_env, ) => { @@ -152,6 +172,7 @@ fn satisfied_from_param_env<'tcx>( impl<'a, 'tcx> TypeVisitor<'tcx> for Visitor<'a, 'tcx> { type BreakTy = (); fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> { + debug!("is_const_evaluatable: candidate={:?}", c); if let Ok(()) = self.infcx.commit_if_ok(|_| { let ocx = ObligationCtxt::new_in_snapshot(self.infcx); if let Ok(()) = ocx.eq(&ObligationCause::dummy(), self.param_env, c.ty(), self.ct.ty()) @@ -187,7 +208,7 @@ fn satisfied_from_param_env<'tcx>( let result = b_ct.visit_with(&mut v); if let ControlFlow::Break(()) = result { - debug!("is_const_evaluatable: abstract_const ~~> ok"); + debug!("is_const_evaluatable: yes"); return true; } } @@ -195,5 +216,6 @@ fn satisfied_from_param_env<'tcx>( } } + debug!("is_const_evaluatable: no"); false } diff --git a/compiler/rustc_trait_selection/src/traits/wf.rs b/compiler/rustc_trait_selection/src/traits/wf.rs index 0855d6d1973..e47ba64245f 100644 --- a/compiler/rustc_trait_selection/src/traits/wf.rs +++ b/compiler/rustc_trait_selection/src/traits/wf.rs @@ -476,9 +476,24 @@ impl<'tcx> WfPredicates<'tcx> { ty::Binder::dummy(ty::PredicateKind::WellFormed(ct.into())), )); } - // FIXME(generic_const_exprs): This seems wrong but I could not find a way to get this to trigger ty::ConstKind::Expr(_) => { - bug!("checking wfness of `ConstKind::Expr` is unsupported") + // FIXME(generic_const_exprs): this doesnt verify that given `Expr(N + 1)` the + // trait bound `typeof(N): Add<typeof(1)>` holds. This is currently unnecessary + // as `ConstKind::Expr` is only produced via normalization of `ConstKind::Unevaluated` + // which means that the `DefId` would have been typeck'd elsewhere. However in + // the future we may allow directly lowering to `ConstKind::Expr` in which case + // we would not be proving bounds we should. + + let predicate = + ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(ct)); + let cause = self.cause(traits::WellFormed(None)); + self.out.push(traits::Obligation::with_depth( + self.tcx(), + cause, + self.recursion_depth, + self.param_env, + predicate, + )); } ty::ConstKind::Error(_) diff --git a/src/test/ui/const-generics/generic_const_exprs/const_kind_expr/wf_obligation.rs b/src/test/ui/const-generics/generic_const_exprs/const_kind_expr/wf_obligation.rs new file mode 100644 index 00000000000..6093fc70b16 --- /dev/null +++ b/src/test/ui/const-generics/generic_const_exprs/const_kind_expr/wf_obligation.rs @@ -0,0 +1,22 @@ +#![feature(generic_const_exprs, generic_arg_infer)] +#![allow(incomplete_features)] + +// minimized repro for #105205 +// +// the `foo::<_, L>` call results in a `WellFormed(_)` obligation and a +// `ConstEvaluatable(Unevaluated(_ + 1 + L))` obligation. Attempting to fulfill the latter +// unifies the `_` with `Expr(L - 1)` from the paramenv which turns the `WellFormed` +// obligation into `WellFormed(Expr(L - 1))` + +fn foo<const N: usize, const M: usize>(_: [(); N + 1 + M]) {} + +fn ice<const L: usize>() +where + [(); (L - 1) + 1 + L]:, +{ + foo::<_, L>([(); L + 1 + L]); + //~^ ERROR: mismatched types + //~^^ ERROR: unconstrained generic constant +} + +fn main() {} diff --git a/src/test/ui/const-generics/generic_const_exprs/const_kind_expr/wf_obligation.stderr b/src/test/ui/const-generics/generic_const_exprs/const_kind_expr/wf_obligation.stderr new file mode 100644 index 00000000000..da5194696e6 --- /dev/null +++ b/src/test/ui/const-generics/generic_const_exprs/const_kind_expr/wf_obligation.stderr @@ -0,0 +1,20 @@ +error[E0308]: mismatched types + --> $DIR/wf_obligation.rs:17:17 + | +LL | foo::<_, L>([(); L + 1 + L]); + | ^^^^^^^^^^^^^^^ expected `N + 1 + M`, found `L + 1 + L` + | + = note: expected constant `N + 1 + M` + found constant `L + 1 + L` + +error: unconstrained generic constant + --> $DIR/wf_obligation.rs:17:22 + | +LL | foo::<_, L>([(); L + 1 + L]); + | ^^^^^^^^^ + | + = help: try adding a `where` bound using this expression: `where [(); L + 1 + L]:` + +error: aborting due to 2 previous errors + +For more information about this error, try `rustc --explain E0308`. |