From 3b8089a32055fe9b716db3fcd9d61ccc5bfed97b Mon Sep 17 00:00:00 2001 From: Michael Goulet Date: Sun, 22 Sep 2024 13:10:12 -0400 Subject: [PATCH] Introduce structurally_normalize_const, use it in hir_typeck --- compiler/rustc_hir/src/hir.rs | 13 +++- compiler/rustc_hir_typeck/src/expr.rs | 66 ++++++++++--------- .../rustc_hir_typeck/src/fn_ctxt/_impl.rs | 27 ++++++++ .../src/fn_ctxt/suggestions.rs | 5 +- compiler/rustc_hir_typeck/src/intrinsicck.rs | 4 +- compiler/rustc_hir_typeck/src/pat.rs | 2 +- .../src/traits/structural_normalize.rs | 40 +++++++++++ .../generic_const_exprs/different-fn.stderr | 4 +- 8 files changed, 122 insertions(+), 39 deletions(-) diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs index f92c6650355..00a6c3a0291 100644 --- a/compiler/rustc_hir/src/hir.rs +++ b/compiler/rustc_hir/src/hir.rs @@ -1668,10 +1668,17 @@ pub enum ArrayLen<'hir> { } impl ArrayLen<'_> { - pub fn hir_id(&self) -> HirId { + pub fn span(self) -> Span { match self { - ArrayLen::Infer(InferArg { hir_id, .. }) | ArrayLen::Body(ConstArg { hir_id, .. }) => { - *hir_id + ArrayLen::Infer(arg) => arg.span, + ArrayLen::Body(body) => body.span(), + } + } + + pub fn hir_id(self) -> HirId { + match self { + ArrayLen::Infer(InferArg { hir_id, .. }) | ArrayLen::Body(&ConstArg { hir_id, .. }) => { + hir_id } } } diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs index 821a90d7a8c..9341a449732 100644 --- a/compiler/rustc_hir_typeck/src/expr.rs +++ b/compiler/rustc_hir_typeck/src/expr.rs @@ -1491,8 +1491,10 @@ fn check_expr_repeat( expr: &'tcx hir::Expr<'tcx>, ) -> Ty<'tcx> { let tcx = self.tcx; - let count = self.lower_array_length(count); - if let Some(count) = count.try_eval_target_usize(tcx, self.param_env) { + let count_span = count.span(); + let count = self.try_structurally_resolve_const(count_span, self.lower_array_length(count)); + + if let Some(count) = count.try_to_target_usize(tcx) { self.suggest_array_len(expr, count); } @@ -1520,19 +1522,24 @@ fn check_expr_repeat( return Ty::new_error(tcx, guar); } - self.check_repeat_element_needs_copy_bound(element, count, element_ty); + // If the length is 0, we don't create any elements, so we don't copy any. + // If the length is 1, we don't copy that one element, we move it. Only check + // for `Copy` if the length is larger, or unevaluated. + // FIXME(min_const_generic_exprs): We could perhaps defer this check so that + // we don't require `::CONST` doesn't unnecessarily require `Copy`. + if count.try_to_target_usize(tcx).is_none_or(|x| x > 1) { + self.enforce_repeat_element_needs_copy_bound(element, element_ty); + } let ty = Ty::new_array_with_const_len(tcx, t, count); - self.register_wf_obligation(ty.into(), expr.span, ObligationCauseCode::WellFormed(None)); - ty } - fn check_repeat_element_needs_copy_bound( + /// Requires that `element_ty` is `Copy` (unless it's a const expression itself). + fn enforce_repeat_element_needs_copy_bound( &self, element: &hir::Expr<'_>, - count: ty::Const<'tcx>, element_ty: Ty<'tcx>, ) { let tcx = self.tcx; @@ -1565,27 +1572,23 @@ fn check_repeat_element_needs_copy_bound( _ => traits::IsConstable::No, }; - // If the length is 0, we don't create any elements, so we don't copy any. If the length is 1, we - // don't copy that one element, we move it. Only check for Copy if the length is larger. - if count.try_eval_target_usize(tcx, self.param_env).is_none_or(|len| len > 1) { - let lang_item = self.tcx.require_lang_item(LangItem::Copy, None); - let code = traits::ObligationCauseCode::RepeatElementCopy { - is_constable, - elt_type: element_ty, - elt_span: element.span, - elt_stmt_span: self - .tcx - .hir() - .parent_iter(element.hir_id) - .find_map(|(_, node)| match node { - hir::Node::Item(it) => Some(it.span), - hir::Node::Stmt(stmt) => Some(stmt.span), - _ => None, - }) - .expect("array repeat expressions must be inside an item or statement"), - }; - self.require_type_meets(element_ty, element.span, code, lang_item); - } + let lang_item = self.tcx.require_lang_item(LangItem::Copy, None); + let code = traits::ObligationCauseCode::RepeatElementCopy { + is_constable, + elt_type: element_ty, + elt_span: element.span, + elt_stmt_span: self + .tcx + .hir() + .parent_iter(element.hir_id) + .find_map(|(_, node)| match node { + hir::Node::Item(it) => Some(it.span), + hir::Node::Stmt(stmt) => Some(stmt.span), + _ => None, + }) + .expect("array repeat expressions must be inside an item or statement"), + }; + self.require_type_meets(element_ty, element.span, code, lang_item); } fn check_expr_tuple( @@ -2800,9 +2803,10 @@ fn maybe_suggest_array_indexing( len: ty::Const<'tcx>, ) { err.span_label(field.span, "unknown field"); - if let (Some(len), Ok(user_index)) = - (len.try_eval_target_usize(self.tcx, self.param_env), field.as_str().parse::()) - { + if let (Some(len), Ok(user_index)) = ( + self.try_structurally_resolve_const(base.span, len).try_to_target_usize(self.tcx), + field.as_str().parse::(), + ) { let help = "instead of using tuple indexing, use array indexing"; let applicability = if len < user_index { Applicability::MachineApplicable diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs index 61898b06476..b019c75cd2e 100644 --- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs +++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs @@ -1477,6 +1477,33 @@ pub fn try_structurally_resolve_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> } } + #[instrument(level = "debug", skip(self, sp), ret)] + pub fn try_structurally_resolve_const(&self, sp: Span, ct: ty::Const<'tcx>) -> ty::Const<'tcx> { + // FIXME(min_const_generic_exprs): We could process obligations here if `ct` is a var. + + if self.next_trait_solver() + && let ty::ConstKind::Unevaluated(..) = ct.kind() + { + // We need to use a separate variable here as otherwise the temporary for + // `self.fulfillment_cx.borrow_mut()` is alive in the `Err` branch, resulting + // in a reentrant borrow, causing an ICE. + let result = self + .at(&self.misc(sp), self.param_env) + .structurally_normalize_const(ct, &mut **self.fulfillment_cx.borrow_mut()); + match result { + Ok(normalized_ct) => normalized_ct, + Err(errors) => { + let guar = self.err_ctxt().report_fulfillment_errors(errors); + return ty::Const::new_error(self.tcx, guar); + } + } + } else if self.tcx.features().generic_const_exprs { + ct.normalize(self.tcx, self.param_env) + } else { + ct + } + } + /// Resolves `ty` by a single level if `ty` is a type variable. /// /// When the new solver is enabled, this will also attempt to normalize diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs index b71e34864fd..35ed63bf232 100644 --- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs +++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs @@ -1502,7 +1502,10 @@ pub(crate) fn suggest_deref_unwrap_or( // Create an dummy type `&[_]` so that both &[] and `&Vec` can coerce to it. let dummy_ty = if let ty::Array(elem_ty, size) = peeled.kind() && let ty::Infer(_) = elem_ty.kind() - && size.try_eval_target_usize(self.tcx, self.param_env) == Some(0) + && self + .try_structurally_resolve_const(provided_expr.span, *size) + .try_to_target_usize(self.tcx) + == Some(0) { let slice = Ty::new_slice(self.tcx, *elem_ty); Ty::new_imm_ref(self.tcx, self.tcx.lifetimes.re_static, slice) diff --git a/compiler/rustc_hir_typeck/src/intrinsicck.rs b/compiler/rustc_hir_typeck/src/intrinsicck.rs index 81d940a3f9b..a4121adf628 100644 --- a/compiler/rustc_hir_typeck/src/intrinsicck.rs +++ b/compiler/rustc_hir_typeck/src/intrinsicck.rs @@ -101,7 +101,9 @@ pub(crate) fn check_transmute(&self, from: Ty<'tcx>, to: Ty<'tcx>, hir_id: HirId } } Ok(SizeSkeleton::Generic(size)) => { - if let Some(size) = size.try_eval_target_usize(tcx, self.param_env) { + if let Some(size) = + self.try_structurally_resolve_const(span, size).try_to_target_usize(tcx) + { format!("{size} bytes") } else { format!("generic size {size}") diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs index 7dd6deb4fe6..f911137c940 100644 --- a/compiler/rustc_hir_typeck/src/pat.rs +++ b/compiler/rustc_hir_typeck/src/pat.rs @@ -2412,7 +2412,7 @@ fn check_array_pat_len( len: ty::Const<'tcx>, min_len: u64, ) -> (Option>, Ty<'tcx>) { - let len = len.try_eval_target_usize(self.tcx, self.param_env); + let len = self.try_structurally_resolve_const(span, len).try_to_target_usize(self.tcx); let guar = if let Some(len) = len { // Now we know the length... diff --git a/compiler/rustc_trait_selection/src/traits/structural_normalize.rs b/compiler/rustc_trait_selection/src/traits/structural_normalize.rs index 9d657ade86b..3814f8112e9 100644 --- a/compiler/rustc_trait_selection/src/traits/structural_normalize.rs +++ b/compiler/rustc_trait_selection/src/traits/structural_normalize.rs @@ -46,4 +46,44 @@ fn structurally_normalize( Ok(self.normalize(ty).into_value_registering_obligations(self.infcx, fulfill_cx)) } } + + fn structurally_normalize_const( + &self, + ct: ty::Const<'tcx>, + fulfill_cx: &mut dyn TraitEngine<'tcx, E>, + ) -> Result, Vec> { + assert!(!ct.is_ct_infer(), "should have resolved vars before calling"); + + if self.infcx.next_trait_solver() { + let ty::ConstKind::Unevaluated(..) = ct.kind() else { + return Ok(ct); + }; + + let new_infer_ct = self.infcx.next_const_var(self.cause.span); + + // We simply emit an `alias-eq` goal here, since that will take care of + // normalizing the LHS of the projection until it is a rigid projection + // (or a not-yet-defined opaque in scope). + let obligation = Obligation::new( + self.infcx.tcx, + self.cause.clone(), + self.param_env, + ty::PredicateKind::AliasRelate( + ct.into(), + new_infer_ct.into(), + ty::AliasRelationDirection::Equate, + ), + ); + + fulfill_cx.register_predicate_obligation(self.infcx, obligation); + let errors = fulfill_cx.select_where_possible(self.infcx); + if !errors.is_empty() { + return Err(errors); + } + + Ok(self.infcx.resolve_vars_if_possible(new_infer_ct)) + } else { + Ok(self.normalize(ct).into_value_registering_obligations(self.infcx, fulfill_cx)) + } + } } diff --git a/tests/ui/const-generics/generic_const_exprs/different-fn.stderr b/tests/ui/const-generics/generic_const_exprs/different-fn.stderr index 52917df0da1..ac80463480d 100644 --- a/tests/ui/const-generics/generic_const_exprs/different-fn.stderr +++ b/tests/ui/const-generics/generic_const_exprs/different-fn.stderr @@ -2,10 +2,10 @@ error[E0308]: mismatched types --> $DIR/different-fn.rs:10:5 | LL | [0; size_of::>()] - | ^^^^^^^^^^^^^^^^^^^^^^^^ expected `size_of::()`, found `size_of::>()` + | ^^^^^^^^^^^^^^^^^^^^^^^^ expected `size_of::()`, found `0` | = note: expected constant `size_of::()` - found constant `size_of::>()` + found constant `0` error: unconstrained generic constant --> $DIR/different-fn.rs:10:9