diff --git a/Cargo.lock b/Cargo.lock index 2bf07149cc8..147d4704407 100644 --- a/Cargo.lock +++ b/Cargo.lock @@ -4514,6 +4514,7 @@ dependencies = [ "rustc_data_structures", "rustc_errors", "rustc_hir", + "rustc_index", "rustc_infer", "rustc_middle", "rustc_session", diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs index f0ccf02c9fa..e5025121c4f 100644 --- a/compiler/rustc_metadata/src/rmeta/decoder.rs +++ b/compiler/rustc_metadata/src/rmeta/decoder.rs @@ -21,7 +21,6 @@ use rustc_index::vec::{Idx, IndexVec}; use rustc_middle::metadata::ModChild; use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo}; use rustc_middle::mir::interpret::{AllocDecodingSession, AllocDecodingState}; -use rustc_middle::thir; use rustc_middle::ty::codec::TyDecoder; use rustc_middle::ty::fast_reject::SimplifiedType; use rustc_middle::ty::GeneratorDiagnosticData; @@ -638,7 +637,7 @@ impl<'a, 'tcx> Decodable> for Span { } } -impl<'a, 'tcx> Decodable> for &'tcx [thir::abstract_const::Node<'tcx>] { +impl<'a, 'tcx> Decodable> for &'tcx [ty::abstract_const::Node<'tcx>] { fn decode(d: &mut DecodeContext<'a, 'tcx>) -> Self { ty::codec::RefDecodable::decode(d) } diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs index a50eb2a71cf..a5a9dbb8da2 100644 --- a/compiler/rustc_metadata/src/rmeta/mod.rs +++ b/compiler/rustc_metadata/src/rmeta/mod.rs @@ -17,7 +17,6 @@ use rustc_middle::metadata::ModChild; use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs; use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo}; use rustc_middle::mir; -use rustc_middle::thir; use rustc_middle::ty::fast_reject::SimplifiedType; use rustc_middle::ty::query::Providers; use rustc_middle::ty::{self, ReprOptions, Ty}; @@ -361,7 +360,7 @@ define_tables! { mir_for_ctfe: Table>>, promoted_mir: Table>>>, // FIXME(compiler-errors): Why isn't this a LazyArray? - thir_abstract_const: Table]>>, + thir_abstract_const: Table]>>, impl_parent: Table, impl_polarity: Table, constness: Table, diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs index cbc45526e89..bdae7e5fcd6 100644 --- a/compiler/rustc_middle/src/query/mod.rs +++ b/compiler/rustc_middle/src/query/mod.rs @@ -351,7 +351,7 @@ rustc_queries! { /// Try to build an abstract representation of the given constant. query thir_abstract_const( key: DefId - ) -> Result]>, ErrorGuaranteed> { + ) -> Result]>, ErrorGuaranteed> { desc { |tcx| "building an abstract representation for {}", tcx.def_path_str(key), } @@ -360,7 +360,7 @@ rustc_queries! { /// Try to build an abstract representation of the given constant. query thir_abstract_const_of_const_arg( key: (LocalDefId, DefId) - ) -> Result]>, ErrorGuaranteed> { + ) -> Result]>, ErrorGuaranteed> { desc { |tcx| "building an abstract representation for the const argument {}", diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs index 3fe6394ad7e..d5700692b9d 100644 --- a/compiler/rustc_middle/src/thir.rs +++ b/compiler/rustc_middle/src/thir.rs @@ -30,7 +30,6 @@ use rustc_target::asm::InlineAsmRegOrRegClass; use std::fmt; use std::ops::Index; -pub mod abstract_const; pub mod visit; newtype_index! { diff --git a/compiler/rustc_middle/src/thir/abstract_const.rs b/compiler/rustc_middle/src/thir/abstract_const.rs deleted file mode 100644 index 527dbd1cd09..00000000000 --- a/compiler/rustc_middle/src/thir/abstract_const.rs +++ /dev/null @@ -1,61 +0,0 @@ -//! A subset of a mir body used for const evaluatability checking. -use crate::mir; -use crate::ty::{self, Ty, TyCtxt}; -use rustc_errors::ErrorGuaranteed; - -rustc_index::newtype_index! { - /// An index into an `AbstractConst`. - pub struct NodeId { - derive [HashStable] - DEBUG_FORMAT = "n{}", - } -} - -#[derive(Debug, Clone, Copy, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)] -pub enum CastKind { - /// thir::ExprKind::As - As, - /// thir::ExprKind::Use - Use, -} - -/// A node of an `AbstractConst`. -#[derive(Debug, Clone, Copy, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)] -pub enum Node<'tcx> { - Leaf(ty::Const<'tcx>), - Binop(mir::BinOp, NodeId, NodeId), - UnaryOp(mir::UnOp, NodeId), - FunctionCall(NodeId, &'tcx [NodeId]), - Cast(CastKind, NodeId, Ty<'tcx>), -} - -#[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)] -pub enum NotConstEvaluatable { - Error(ErrorGuaranteed), - MentionsInfer, - MentionsParam, -} - -impl From for NotConstEvaluatable { - fn from(e: ErrorGuaranteed) -> NotConstEvaluatable { - NotConstEvaluatable::Error(e) - } -} - -TrivialTypeTraversalAndLiftImpls! { - NotConstEvaluatable, -} - -impl<'tcx> TyCtxt<'tcx> { - #[inline] - pub fn thir_abstract_const_opt_const_arg( - self, - def: ty::WithOptConstParam, - ) -> Result]>, ErrorGuaranteed> { - if let Some((did, param_did)) = def.as_const_arg() { - self.thir_abstract_const_of_const_arg((did, param_did)) - } else { - self.thir_abstract_const(def.did) - } - } -} diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs index fe7f72024d3..955f2bdfa1d 100644 --- a/compiler/rustc_middle/src/traits/mod.rs +++ b/compiler/rustc_middle/src/traits/mod.rs @@ -10,7 +10,7 @@ mod structural_impls; pub mod util; use crate::infer::canonical::Canonical; -use crate::thir::abstract_const::NotConstEvaluatable; +use crate::ty::abstract_const::NotConstEvaluatable; use crate::ty::subst::SubstsRef; use crate::ty::{self, AdtKind, Ty, TyCtxt}; diff --git a/compiler/rustc_middle/src/ty/abstract_const.rs b/compiler/rustc_middle/src/ty/abstract_const.rs new file mode 100644 index 00000000000..3e376d54000 --- /dev/null +++ b/compiler/rustc_middle/src/ty/abstract_const.rs @@ -0,0 +1,302 @@ +//! A subset of a mir body used for const evaluatability checking. +use crate::mir; +use crate::ty::{self, subst::Subst, DelaySpanBugEmitted, EarlyBinder, SubstsRef, Ty, TyCtxt}; +use rustc_errors::ErrorGuaranteed; +use std::iter; +use std::ops::ControlFlow; + +rustc_index::newtype_index! { + /// An index into an `AbstractConst`. + pub struct NodeId { + derive [HashStable] + DEBUG_FORMAT = "n{}", + } +} + +/// A tree representing an anonymous constant. +/// +/// This is only able to represent a subset of `MIR`, +/// and should not leak any information about desugarings. +#[derive(Debug, Clone, Copy)] +pub struct AbstractConst<'tcx> { + // FIXME: Consider adding something like `IndexSlice` + // and use this here. + inner: &'tcx [Node<'tcx>], + substs: SubstsRef<'tcx>, +} + +impl<'tcx> AbstractConst<'tcx> { + pub fn new( + tcx: TyCtxt<'tcx>, + uv: ty::Unevaluated<'tcx, ()>, + ) -> Result>, ErrorGuaranteed> { + let inner = tcx.thir_abstract_const_opt_const_arg(uv.def)?; + debug!("AbstractConst::new({:?}) = {:?}", uv, inner); + Ok(inner.map(|inner| AbstractConst { inner, substs: tcx.erase_regions(uv.substs) })) + } + + pub fn from_const( + tcx: TyCtxt<'tcx>, + ct: ty::Const<'tcx>, + ) -> Result>, ErrorGuaranteed> { + match ct.kind() { + ty::ConstKind::Unevaluated(uv) => AbstractConst::new(tcx, uv.shrink()), + ty::ConstKind::Error(DelaySpanBugEmitted { reported, .. }) => Err(reported), + _ => Ok(None), + } + } + + #[inline] + pub fn subtree(self, node: NodeId) -> AbstractConst<'tcx> { + AbstractConst { inner: &self.inner[..=node.index()], substs: self.substs } + } + + #[inline] + pub fn root(self, tcx: TyCtxt<'tcx>) -> Node<'tcx> { + let node = self.inner.last().copied().unwrap(); + match node { + Node::Leaf(leaf) => Node::Leaf(EarlyBinder(leaf).subst(tcx, self.substs)), + Node::Cast(kind, operand, ty) => { + Node::Cast(kind, operand, EarlyBinder(ty).subst(tcx, self.substs)) + } + // Don't perform substitution on the following as they can't directly contain generic params + Node::Binop(_, _, _) | Node::UnaryOp(_, _) | Node::FunctionCall(_, _) => node, + } + } +} + +#[derive(Debug, Clone, Copy, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)] +pub enum CastKind { + /// thir::ExprKind::As + As, + /// thir::ExprKind::Use + Use, +} + +/// A node of an `AbstractConst`. +#[derive(Debug, Clone, Copy, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)] +pub enum Node<'tcx> { + Leaf(ty::Const<'tcx>), + Binop(mir::BinOp, NodeId, NodeId), + UnaryOp(mir::UnOp, NodeId), + FunctionCall(NodeId, &'tcx [NodeId]), + Cast(CastKind, NodeId, Ty<'tcx>), +} + +#[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)] +pub enum NotConstEvaluatable { + Error(ErrorGuaranteed), + MentionsInfer, + MentionsParam, +} + +impl From for NotConstEvaluatable { + fn from(e: ErrorGuaranteed) -> NotConstEvaluatable { + NotConstEvaluatable::Error(e) + } +} + +TrivialTypeTraversalAndLiftImpls! { + NotConstEvaluatable, +} + +impl<'tcx> TyCtxt<'tcx> { + #[inline] + pub fn thir_abstract_const_opt_const_arg( + self, + def: ty::WithOptConstParam, + ) -> Result]>, ErrorGuaranteed> { + if let Some((did, param_did)) = def.as_const_arg() { + self.thir_abstract_const_of_const_arg((did, param_did)) + } else { + self.thir_abstract_const(def.did) + } + } +} + +#[instrument(skip(tcx), level = "debug")] +pub fn try_unify_abstract_consts<'tcx>( + tcx: TyCtxt<'tcx>, + (a, b): (ty::Unevaluated<'tcx, ()>, ty::Unevaluated<'tcx, ()>), + param_env: ty::ParamEnv<'tcx>, +) -> bool { + (|| { + if let Some(a) = AbstractConst::new(tcx, a)? { + if let Some(b) = AbstractConst::new(tcx, b)? { + let const_unify_ctxt = ConstUnifyCtxt { tcx, param_env }; + return Ok(const_unify_ctxt.try_unify(a, b)); + } + } + + Ok(false) + })() + .unwrap_or_else(|_: ErrorGuaranteed| true) + // FIXME(generic_const_exprs): We should instead have this + // method return the resulting `ty::Const` and return `ConstKind::Error` + // on `ErrorGuaranteed`. +} + +#[instrument(skip(tcx, f), level = "debug")] +pub fn walk_abstract_const<'tcx, R, F>( + tcx: TyCtxt<'tcx>, + ct: AbstractConst<'tcx>, + mut f: F, +) -> ControlFlow +where + F: FnMut(AbstractConst<'tcx>) -> ControlFlow, +{ + #[instrument(skip(tcx, f), level = "debug")] + fn recurse<'tcx, R>( + tcx: TyCtxt<'tcx>, + ct: AbstractConst<'tcx>, + f: &mut dyn FnMut(AbstractConst<'tcx>) -> ControlFlow, + ) -> ControlFlow { + f(ct)?; + let root = ct.root(tcx); + debug!(?root); + match root { + Node::Leaf(_) => ControlFlow::CONTINUE, + Node::Binop(_, l, r) => { + recurse(tcx, ct.subtree(l), f)?; + recurse(tcx, ct.subtree(r), f) + } + Node::UnaryOp(_, v) => recurse(tcx, ct.subtree(v), f), + Node::FunctionCall(func, args) => { + recurse(tcx, ct.subtree(func), f)?; + args.iter().try_for_each(|&arg| recurse(tcx, ct.subtree(arg), f)) + } + Node::Cast(_, operand, _) => recurse(tcx, ct.subtree(operand), f), + } + } + + recurse(tcx, ct, &mut f) +} + +pub struct ConstUnifyCtxt<'tcx> { + pub tcx: TyCtxt<'tcx>, + pub param_env: ty::ParamEnv<'tcx>, +} + +impl<'tcx> ConstUnifyCtxt<'tcx> { + // Substitutes generics repeatedly to allow AbstractConsts to unify where a + // ConstKind::Unevaluated could be turned into an AbstractConst that would unify e.g. + // Param(N) should unify with Param(T), substs: [Unevaluated("T2", [Unevaluated("T3", [Param(N)])])] + #[inline] + #[instrument(skip(self), level = "debug")] + fn try_replace_substs_in_root( + &self, + mut abstr_const: AbstractConst<'tcx>, + ) -> Option> { + while let Node::Leaf(ct) = abstr_const.root(self.tcx) { + match AbstractConst::from_const(self.tcx, ct) { + Ok(Some(act)) => abstr_const = act, + Ok(None) => break, + Err(_) => return None, + } + } + + Some(abstr_const) + } + + /// Tries to unify two abstract constants using structural equality. + #[instrument(skip(self), level = "debug")] + pub fn try_unify(&self, a: AbstractConst<'tcx>, b: AbstractConst<'tcx>) -> bool { + let a = if let Some(a) = self.try_replace_substs_in_root(a) { + a + } else { + return true; + }; + + let b = if let Some(b) = self.try_replace_substs_in_root(b) { + b + } else { + return true; + }; + + let a_root = a.root(self.tcx); + let b_root = b.root(self.tcx); + debug!(?a_root, ?b_root); + + match (a_root, b_root) { + (Node::Leaf(a_ct), Node::Leaf(b_ct)) => { + let a_ct = a_ct.eval(self.tcx, self.param_env); + debug!("a_ct evaluated: {:?}", a_ct); + let b_ct = b_ct.eval(self.tcx, self.param_env); + debug!("b_ct evaluated: {:?}", b_ct); + + if a_ct.ty() != b_ct.ty() { + return false; + } + + match (a_ct.kind(), b_ct.kind()) { + // We can just unify errors with everything to reduce the amount of + // emitted errors here. + (ty::ConstKind::Error(_), _) | (_, ty::ConstKind::Error(_)) => true, + (ty::ConstKind::Param(a_param), ty::ConstKind::Param(b_param)) => { + a_param == b_param + } + (ty::ConstKind::Value(a_val), ty::ConstKind::Value(b_val)) => a_val == b_val, + // If we have `fn a() -> [u8; N + 1]` and `fn b() -> [u8; 1 + M]` + // we do not want to use `assert_eq!(a(), b())` to infer that `N` and `M` have to be `1`. This + // means that we only allow inference variables if they are equal. + (ty::ConstKind::Infer(a_val), ty::ConstKind::Infer(b_val)) => a_val == b_val, + // We expand generic anonymous constants at the start of this function, so this + // branch should only be taking when dealing with associated constants, at + // which point directly comparing them seems like the desired behavior. + // + // FIXME(generic_const_exprs): This isn't actually the case. + // We also take this branch for concrete anonymous constants and + // expand generic anonymous constants with concrete substs. + (ty::ConstKind::Unevaluated(a_uv), ty::ConstKind::Unevaluated(b_uv)) => { + a_uv == b_uv + } + // FIXME(generic_const_exprs): We may want to either actually try + // to evaluate `a_ct` and `b_ct` if they are are fully concrete or something like + // this, for now we just return false here. + _ => false, + } + } + (Node::Binop(a_op, al, ar), Node::Binop(b_op, bl, br)) if a_op == b_op => { + self.try_unify(a.subtree(al), b.subtree(bl)) + && self.try_unify(a.subtree(ar), b.subtree(br)) + } + (Node::UnaryOp(a_op, av), Node::UnaryOp(b_op, bv)) if a_op == b_op => { + self.try_unify(a.subtree(av), b.subtree(bv)) + } + (Node::FunctionCall(a_f, a_args), Node::FunctionCall(b_f, b_args)) + if a_args.len() == b_args.len() => + { + self.try_unify(a.subtree(a_f), b.subtree(b_f)) + && iter::zip(a_args, b_args) + .all(|(&an, &bn)| self.try_unify(a.subtree(an), b.subtree(bn))) + } + (Node::Cast(a_kind, a_operand, a_ty), Node::Cast(b_kind, b_operand, b_ty)) + if (a_ty == b_ty) && (a_kind == b_kind) => + { + self.try_unify(a.subtree(a_operand), b.subtree(b_operand)) + } + // use this over `_ => false` to make adding variants to `Node` less error prone + (Node::Cast(..), _) + | (Node::FunctionCall(..), _) + | (Node::UnaryOp(..), _) + | (Node::Binop(..), _) + | (Node::Leaf(..), _) => false, + } + } +} + +// We were unable to unify the abstract constant with +// a constant found in the caller bounds, there are +// now three possible cases here. +#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)] +pub enum FailureKind { + /// The abstract const still references an inference + /// variable, in this case we return `TooGeneric`. + MentionsInfer, + /// The abstract const references a generic parameter, + /// this means that we emit an error here. + MentionsParam, + /// The substs are concrete enough that we can simply + /// try and evaluate the given constant. + Concrete, +} diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs index 9a363914dc3..e6ea3d88853 100644 --- a/compiler/rustc_middle/src/ty/codec.rs +++ b/compiler/rustc_middle/src/ty/codec.rs @@ -12,7 +12,6 @@ use crate::mir::{ self, interpret::{AllocId, ConstAllocation}, }; -use crate::thir; use crate::traits; use crate::ty::subst::SubstsRef; use crate::ty::{self, AdtDef, Ty}; @@ -346,7 +345,7 @@ impl<'tcx, D: TyDecoder>> RefDecodable<'tcx, D> } impl<'tcx, D: TyDecoder>> RefDecodable<'tcx, D> - for [thir::abstract_const::Node<'tcx>] + for [ty::abstract_const::Node<'tcx>] { fn decode(decoder: &mut D) -> &'tcx Self { decoder.interner().arena.alloc_from_iter( @@ -356,7 +355,7 @@ impl<'tcx, D: TyDecoder>> RefDecodable<'tcx, D> } impl<'tcx, D: TyDecoder>> RefDecodable<'tcx, D> - for [thir::abstract_const::NodeId] + for [ty::abstract_const::NodeId] { fn decode(decoder: &mut D) -> &'tcx Self { decoder.interner().arena.alloc_from_iter( diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs index f15108fb750..d23019e1521 100644 --- a/compiler/rustc_middle/src/ty/mod.rs +++ b/compiler/rustc_middle/src/ty/mod.rs @@ -92,6 +92,7 @@ pub use self::sty::{ pub use self::trait_def::TraitDef; pub mod _match; +pub mod abstract_const; pub mod adjustment; pub mod binding; pub mod cast; diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs index 54ba9e84fdb..e189ee2fc4d 100644 --- a/compiler/rustc_middle/src/ty/parameterized.rs +++ b/compiler/rustc_middle/src/ty/parameterized.rs @@ -3,7 +3,7 @@ use rustc_index::vec::{Idx, IndexVec}; use crate::middle::exported_symbols::ExportedSymbol; use crate::mir::Body; -use crate::thir::abstract_const::Node; +use crate::ty::abstract_const::Node; use crate::ty::{ self, Const, FnSig, GeneratorDiagnosticData, GenericPredicates, Predicate, TraitRef, Ty, }; diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs index 5560d44aa0d..4e73c26d35f 100644 --- a/compiler/rustc_privacy/src/lib.rs +++ b/compiler/rustc_privacy/src/lib.rs @@ -23,7 +23,7 @@ use rustc_middle::bug; use rustc_middle::hir::nested_filter; use rustc_middle::middle::privacy::{AccessLevel, AccessLevels}; use rustc_middle::span_bug; -use rustc_middle::thir::abstract_const::Node as ACNode; +use rustc_middle::ty::abstract_const::{walk_abstract_const, AbstractConst, Node as ACNode}; use rustc_middle::ty::query::Providers; use rustc_middle::ty::subst::InternalSubsts; use rustc_middle::ty::{self, Const, DefIdTree, GenericParamDefKind}; @@ -32,7 +32,6 @@ use rustc_session::lint; use rustc_span::hygiene::Transparency; use rustc_span::symbol::{kw, Ident}; use rustc_span::Span; -use rustc_trait_selection::traits::const_evaluatable::{self, AbstractConst}; use std::marker::PhantomData; use std::ops::ControlFlow; @@ -164,7 +163,7 @@ where tcx: TyCtxt<'tcx>, ct: AbstractConst<'tcx>, ) -> ControlFlow { - const_evaluatable::walk_abstract_const(tcx, ct, |node| match node.root(tcx) { + walk_abstract_const(tcx, ct, |node| match node.root(tcx) { ACNode::Leaf(leaf) => self.visit_const(leaf), ACNode::Cast(_, _, ty) => self.visit_ty(ty), ACNode::Binop(..) | ACNode::UnaryOp(..) | ACNode::FunctionCall(_, _) => { diff --git a/compiler/rustc_query_impl/src/on_disk_cache.rs b/compiler/rustc_query_impl/src/on_disk_cache.rs index 4c25075327f..56fd90c9855 100644 --- a/compiler/rustc_query_impl/src/on_disk_cache.rs +++ b/compiler/rustc_query_impl/src/on_disk_cache.rs @@ -9,7 +9,6 @@ use rustc_index::vec::{Idx, IndexVec}; use rustc_middle::dep_graph::{DepNodeIndex, SerializedDepNodeIndex}; use rustc_middle::mir::interpret::{AllocDecodingSession, AllocDecodingState}; use rustc_middle::mir::{self, interpret}; -use rustc_middle::thir; use rustc_middle::ty::codec::{RefDecodable, TyDecoder, TyEncoder}; use rustc_middle::ty::{self, Ty, TyCtxt}; use rustc_query_system::dep_graph::DepContext; @@ -766,7 +765,7 @@ impl<'a, 'tcx> Decodable> } } -impl<'a, 'tcx> Decodable> for &'tcx [thir::abstract_const::Node<'tcx>] { +impl<'a, 'tcx> Decodable> for &'tcx [ty::abstract_const::Node<'tcx>] { fn decode(d: &mut CacheDecoder<'a, 'tcx>) -> Self { RefDecodable::decode(d) } diff --git a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs index 3a152eff485..38581538b17 100644 --- a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs +++ b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs @@ -8,22 +8,17 @@ //! In this case we try to build an abstract representation of this constant using //! `thir_abstract_const` which can then be checked for structural equality with other //! generic constants mentioned in the `caller_bounds` of the current environment. -use rustc_errors::ErrorGuaranteed; use rustc_hir::def::DefKind; -use rustc_index::vec::IndexVec; use rustc_infer::infer::InferCtxt; -use rustc_middle::mir; -use rustc_middle::mir::interpret::{ErrorHandled, LitToConstError, LitToConstInput}; -use rustc_middle::thir; -use rustc_middle::thir::abstract_const::{self, Node, NodeId, NotConstEvaluatable}; -use rustc_middle::ty::subst::{Subst, SubstsRef}; -use rustc_middle::ty::{self, DelaySpanBugEmitted, EarlyBinder, TyCtxt, TypeVisitable}; +use rustc_middle::mir::interpret::ErrorHandled; +use rustc_middle::ty::abstract_const::{ + walk_abstract_const, AbstractConst, ConstUnifyCtxt, FailureKind, Node, NotConstEvaluatable, +}; +use rustc_middle::ty::{self, TyCtxt, TypeVisitable}; use rustc_session::lint; -use rustc_span::def_id::LocalDefId; use rustc_span::Span; use std::cmp; -use std::iter; use std::ops::ControlFlow; /// Check if a given constant can be evaluated. @@ -42,21 +37,6 @@ pub fn is_const_evaluatable<'cx, 'tcx>( return Ok(()); } - // We were unable to unify the abstract constant with - // a constant found in the caller bounds, there are - // now three possible cases here. - #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)] - enum FailureKind { - /// The abstract const still references an inference - /// variable, in this case we return `TooGeneric`. - MentionsInfer, - /// The abstract const references a generic parameter, - /// this means that we emit an error here. - MentionsParam, - /// The substs are concrete enough that we can simply - /// try and evaluate the given constant. - Concrete, - } let mut failure_kind = FailureKind::Concrete; walk_abstract_const::(tcx, ct, |node| match node.root(tcx) { Node::Leaf(leaf) => { @@ -216,593 +196,3 @@ fn satisfied_from_param_env<'tcx>( Ok(false) } - -/// A tree representing an anonymous constant. -/// -/// This is only able to represent a subset of `MIR`, -/// and should not leak any information about desugarings. -#[derive(Debug, Clone, Copy)] -pub struct AbstractConst<'tcx> { - // FIXME: Consider adding something like `IndexSlice` - // and use this here. - inner: &'tcx [Node<'tcx>], - substs: SubstsRef<'tcx>, -} - -impl<'tcx> AbstractConst<'tcx> { - pub fn new( - tcx: TyCtxt<'tcx>, - uv: ty::Unevaluated<'tcx, ()>, - ) -> Result>, ErrorGuaranteed> { - let inner = tcx.thir_abstract_const_opt_const_arg(uv.def)?; - debug!("AbstractConst::new({:?}) = {:?}", uv, inner); - Ok(inner.map(|inner| AbstractConst { inner, substs: tcx.erase_regions(uv.substs) })) - } - - pub fn from_const( - tcx: TyCtxt<'tcx>, - ct: ty::Const<'tcx>, - ) -> Result>, ErrorGuaranteed> { - match ct.kind() { - ty::ConstKind::Unevaluated(uv) => AbstractConst::new(tcx, uv.shrink()), - ty::ConstKind::Error(DelaySpanBugEmitted { reported, .. }) => Err(reported), - _ => Ok(None), - } - } - - #[inline] - pub fn subtree(self, node: NodeId) -> AbstractConst<'tcx> { - AbstractConst { inner: &self.inner[..=node.index()], substs: self.substs } - } - - #[inline] - pub fn root(self, tcx: TyCtxt<'tcx>) -> Node<'tcx> { - let node = self.inner.last().copied().unwrap(); - match node { - Node::Leaf(leaf) => Node::Leaf(EarlyBinder(leaf).subst(tcx, self.substs)), - Node::Cast(kind, operand, ty) => { - Node::Cast(kind, operand, EarlyBinder(ty).subst(tcx, self.substs)) - } - // Don't perform substitution on the following as they can't directly contain generic params - Node::Binop(_, _, _) | Node::UnaryOp(_, _) | Node::FunctionCall(_, _) => node, - } - } -} - -struct AbstractConstBuilder<'a, 'tcx> { - tcx: TyCtxt<'tcx>, - body_id: thir::ExprId, - body: &'a thir::Thir<'tcx>, - /// The current WIP node tree. - nodes: IndexVec>, -} - -impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> { - fn root_span(&self) -> Span { - self.body.exprs[self.body_id].span - } - - fn error(&mut self, span: Span, msg: &str) -> Result { - let reported = self - .tcx - .sess - .struct_span_err(self.root_span(), "overly complex generic constant") - .span_label(span, msg) - .help("consider moving this anonymous constant into a `const` function") - .emit(); - - Err(reported) - } - fn maybe_supported_error(&mut self, span: Span, msg: &str) -> Result { - let reported = self - .tcx - .sess - .struct_span_err(self.root_span(), "overly complex generic constant") - .span_label(span, msg) - .help("consider moving this anonymous constant into a `const` function") - .note("this operation may be supported in the future") - .emit(); - - Err(reported) - } - - #[instrument(skip(tcx, body, body_id), level = "debug")] - fn new( - tcx: TyCtxt<'tcx>, - (body, body_id): (&'a thir::Thir<'tcx>, thir::ExprId), - ) -> Result>, ErrorGuaranteed> { - let builder = AbstractConstBuilder { tcx, body_id, body, nodes: IndexVec::new() }; - - struct IsThirPolymorphic<'a, 'tcx> { - is_poly: bool, - thir: &'a thir::Thir<'tcx>, - } - - use crate::rustc_middle::thir::visit::Visitor; - use thir::visit; - - impl<'a, 'tcx> IsThirPolymorphic<'a, 'tcx> { - fn expr_is_poly(&mut self, expr: &thir::Expr<'tcx>) -> bool { - if expr.ty.has_param_types_or_consts() { - return true; - } - - match expr.kind { - thir::ExprKind::NamedConst { substs, .. } => substs.has_param_types_or_consts(), - thir::ExprKind::ConstParam { .. } => true, - thir::ExprKind::Repeat { value, count } => { - self.visit_expr(&self.thir()[value]); - count.has_param_types_or_consts() - } - _ => false, - } - } - - fn pat_is_poly(&mut self, pat: &thir::Pat<'tcx>) -> bool { - if pat.ty.has_param_types_or_consts() { - return true; - } - - match pat.kind.as_ref() { - thir::PatKind::Constant { value } => value.has_param_types_or_consts(), - thir::PatKind::Range(thir::PatRange { lo, hi, .. }) => { - lo.has_param_types_or_consts() || hi.has_param_types_or_consts() - } - _ => false, - } - } - } - - impl<'a, 'tcx> visit::Visitor<'a, 'tcx> for IsThirPolymorphic<'a, 'tcx> { - fn thir(&self) -> &'a thir::Thir<'tcx> { - &self.thir - } - - #[instrument(skip(self), level = "debug")] - fn visit_expr(&mut self, expr: &thir::Expr<'tcx>) { - self.is_poly |= self.expr_is_poly(expr); - if !self.is_poly { - visit::walk_expr(self, expr) - } - } - - #[instrument(skip(self), level = "debug")] - fn visit_pat(&mut self, pat: &thir::Pat<'tcx>) { - self.is_poly |= self.pat_is_poly(pat); - if !self.is_poly { - visit::walk_pat(self, pat); - } - } - } - - let mut is_poly_vis = IsThirPolymorphic { is_poly: false, thir: body }; - visit::walk_expr(&mut is_poly_vis, &body[body_id]); - debug!("AbstractConstBuilder: is_poly={}", is_poly_vis.is_poly); - if !is_poly_vis.is_poly { - return Ok(None); - } - - Ok(Some(builder)) - } - - /// We do not allow all binary operations in abstract consts, so filter disallowed ones. - fn check_binop(op: mir::BinOp) -> bool { - use mir::BinOp::*; - match op { - Add | Sub | Mul | Div | Rem | BitXor | BitAnd | BitOr | Shl | Shr | Eq | Lt | Le - | Ne | Ge | Gt => true, - Offset => false, - } - } - - /// While we currently allow all unary operations, we still want to explicitly guard against - /// future changes here. - fn check_unop(op: mir::UnOp) -> bool { - use mir::UnOp::*; - match op { - Not | Neg => true, - } - } - - /// Builds the abstract const by walking the thir and bailing out when - /// encountering an unsupported operation. - fn build(mut self) -> Result<&'tcx [Node<'tcx>], ErrorGuaranteed> { - debug!("Abstractconstbuilder::build: body={:?}", &*self.body); - self.recurse_build(self.body_id)?; - - for n in self.nodes.iter() { - if let Node::Leaf(ct) = n { - if let ty::ConstKind::Unevaluated(ct) = ct.kind() { - // `AbstractConst`s should not contain any promoteds as they require references which - // are not allowed. - assert_eq!(ct.promoted, None); - assert_eq!(ct, self.tcx.erase_regions(ct)); - } - } - } - - Ok(self.tcx.arena.alloc_from_iter(self.nodes.into_iter())) - } - - fn recurse_build(&mut self, node: thir::ExprId) -> Result { - use thir::ExprKind; - let node = &self.body.exprs[node]; - Ok(match &node.kind { - // I dont know if handling of these 3 is correct - &ExprKind::Scope { value, .. } => self.recurse_build(value)?, - &ExprKind::PlaceTypeAscription { source, .. } - | &ExprKind::ValueTypeAscription { source, .. } => self.recurse_build(source)?, - &ExprKind::Literal { lit, neg} => { - let sp = node.span; - let constant = - match self.tcx.at(sp).lit_to_const(LitToConstInput { lit: &lit.node, ty: node.ty, neg }) { - Ok(c) => c, - Err(LitToConstError::Reported) => { - self.tcx.const_error(node.ty) - } - Err(LitToConstError::TypeError) => { - bug!("encountered type error in lit_to_const") - } - }; - - self.nodes.push(Node::Leaf(constant)) - } - &ExprKind::NonHirLiteral { lit , user_ty: _} => { - let val = ty::ValTree::from_scalar_int(lit); - self.nodes.push(Node::Leaf(ty::Const::from_value(self.tcx, val, node.ty))) - } - &ExprKind::ZstLiteral { user_ty: _ } => { - let val = ty::ValTree::zst(); - self.nodes.push(Node::Leaf(ty::Const::from_value(self.tcx, val, node.ty))) - } - &ExprKind::NamedConst { def_id, substs, user_ty: _ } => { - let uneval = ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs); - - let constant = self.tcx.mk_const(ty::ConstS { - kind: ty::ConstKind::Unevaluated(uneval), - ty: node.ty, - }); - - self.nodes.push(Node::Leaf(constant)) - } - - ExprKind::ConstParam {param, ..} => { - let const_param = self.tcx.mk_const(ty::ConstS { - kind: ty::ConstKind::Param(*param), - ty: node.ty, - }); - self.nodes.push(Node::Leaf(const_param)) - } - - ExprKind::Call { fun, args, .. } => { - let fun = self.recurse_build(*fun)?; - - let mut new_args = Vec::::with_capacity(args.len()); - for &id in args.iter() { - new_args.push(self.recurse_build(id)?); - } - let new_args = self.tcx.arena.alloc_slice(&new_args); - self.nodes.push(Node::FunctionCall(fun, new_args)) - } - &ExprKind::Binary { op, lhs, rhs } if Self::check_binop(op) => { - let lhs = self.recurse_build(lhs)?; - let rhs = self.recurse_build(rhs)?; - self.nodes.push(Node::Binop(op, lhs, rhs)) - } - &ExprKind::Unary { op, arg } if Self::check_unop(op) => { - let arg = self.recurse_build(arg)?; - self.nodes.push(Node::UnaryOp(op, arg)) - } - // This is necessary so that the following compiles: - // - // ``` - // fn foo(a: [(); N + 1]) { - // bar::<{ N + 1 }>(); - // } - // ``` - ExprKind::Block { body: thir::Block { stmts: box [], expr: Some(e), .. } } => { - self.recurse_build(*e)? - } - // `ExprKind::Use` happens when a `hir::ExprKind::Cast` is a - // "coercion cast" i.e. using a coercion or is a no-op. - // This is important so that `N as usize as usize` doesnt unify with `N as usize`. (untested) - &ExprKind::Use { source } => { - let arg = self.recurse_build(source)?; - self.nodes.push(Node::Cast(abstract_const::CastKind::Use, arg, node.ty)) - } - &ExprKind::Cast { source } => { - let arg = self.recurse_build(source)?; - self.nodes.push(Node::Cast(abstract_const::CastKind::As, arg, node.ty)) - } - ExprKind::Borrow{ arg, ..} => { - let arg_node = &self.body.exprs[*arg]; - - // Skip reborrows for now until we allow Deref/Borrow/AddressOf - // expressions. - // FIXME(generic_const_exprs): Verify/explain why this is sound - if let ExprKind::Deref {arg} = arg_node.kind { - self.recurse_build(arg)? - } else { - self.maybe_supported_error( - node.span, - "borrowing is not supported in generic constants", - )? - } - } - // FIXME(generic_const_exprs): We may want to support these. - ExprKind::AddressOf { .. } | ExprKind::Deref {..}=> self.maybe_supported_error( - node.span, - "dereferencing or taking the address is not supported in generic constants", - )?, - ExprKind::Repeat { .. } | ExprKind::Array { .. } => self.maybe_supported_error( - node.span, - "array construction is not supported in generic constants", - )?, - ExprKind::Block { .. } => self.maybe_supported_error( - node.span, - "blocks are not supported in generic constant", - )?, - ExprKind::NeverToAny { .. } => self.maybe_supported_error( - node.span, - "converting nevers to any is not supported in generic constant", - )?, - ExprKind::Tuple { .. } => self.maybe_supported_error( - node.span, - "tuple construction is not supported in generic constants", - )?, - ExprKind::Index { .. } => self.maybe_supported_error( - node.span, - "indexing is not supported in generic constant", - )?, - ExprKind::Field { .. } => self.maybe_supported_error( - node.span, - "field access is not supported in generic constant", - )?, - ExprKind::ConstBlock { .. } => self.maybe_supported_error( - node.span, - "const blocks are not supported in generic constant", - )?, - ExprKind::Adt(_) => self.maybe_supported_error( - node.span, - "struct/enum construction is not supported in generic constants", - )?, - // dont know if this is correct - ExprKind::Pointer { .. } => - self.error(node.span, "pointer casts are not allowed in generic constants")?, - ExprKind::Yield { .. } => - self.error(node.span, "generator control flow is not allowed in generic constants")?, - ExprKind::Continue { .. } | ExprKind::Break { .. } | ExprKind::Loop { .. } => self - .error( - node.span, - "loops and loop control flow are not supported in generic constants", - )?, - ExprKind::Box { .. } => - self.error(node.span, "allocations are not allowed in generic constants")?, - - ExprKind::Unary { .. } => unreachable!(), - // we handle valid unary/binary ops above - ExprKind::Binary { .. } => - self.error(node.span, "unsupported binary operation in generic constants")?, - ExprKind::LogicalOp { .. } => - self.error(node.span, "unsupported operation in generic constants, short-circuiting operations would imply control flow")?, - ExprKind::Assign { .. } | ExprKind::AssignOp { .. } => { - self.error(node.span, "assignment is not supported in generic constants")? - } - ExprKind::Closure { .. } | ExprKind::Return { .. } => self.error( - node.span, - "closures and function keywords are not supported in generic constants", - )?, - // let expressions imply control flow - ExprKind::Match { .. } | ExprKind::If { .. } | ExprKind::Let { .. } => - self.error(node.span, "control flow is not supported in generic constants")?, - ExprKind::InlineAsm { .. } => { - self.error(node.span, "assembly is not supported in generic constants")? - } - - // we dont permit let stmts so `VarRef` and `UpvarRef` cant happen - ExprKind::VarRef { .. } - | ExprKind::UpvarRef { .. } - | ExprKind::StaticRef { .. } - | ExprKind::ThreadLocalRef(_) => { - self.error(node.span, "unsupported operation in generic constant")? - } - }) - } -} - -/// Builds an abstract const, do not use this directly, but use `AbstractConst::new` instead. -pub(super) fn thir_abstract_const<'tcx>( - tcx: TyCtxt<'tcx>, - def: ty::WithOptConstParam, -) -> Result]>, ErrorGuaranteed> { - if tcx.features().generic_const_exprs { - match tcx.def_kind(def.did) { - // FIXME(generic_const_exprs): We currently only do this for anonymous constants, - // meaning that we do not look into associated constants. I(@lcnr) am not yet sure whether - // we want to look into them or treat them as opaque projections. - // - // Right now we do neither of that and simply always fail to unify them. - DefKind::AnonConst | DefKind::InlineConst => (), - _ => return Ok(None), - } - - let body = tcx.thir_body(def)?; - - AbstractConstBuilder::new(tcx, (&*body.0.borrow(), body.1))? - .map(AbstractConstBuilder::build) - .transpose() - } else { - Ok(None) - } -} - -#[instrument(skip(tcx), level = "debug")] -pub(super) fn try_unify_abstract_consts<'tcx>( - tcx: TyCtxt<'tcx>, - (a, b): (ty::Unevaluated<'tcx, ()>, ty::Unevaluated<'tcx, ()>), - param_env: ty::ParamEnv<'tcx>, -) -> bool { - (|| { - if let Some(a) = AbstractConst::new(tcx, a)? { - if let Some(b) = AbstractConst::new(tcx, b)? { - let const_unify_ctxt = ConstUnifyCtxt { tcx, param_env }; - return Ok(const_unify_ctxt.try_unify(a, b)); - } - } - - Ok(false) - })() - .unwrap_or_else(|_: ErrorGuaranteed| true) - // FIXME(generic_const_exprs): We should instead have this - // method return the resulting `ty::Const` and return `ConstKind::Error` - // on `ErrorGuaranteed`. -} - -#[instrument(skip(tcx, f), level = "debug")] -pub fn walk_abstract_const<'tcx, R, F>( - tcx: TyCtxt<'tcx>, - ct: AbstractConst<'tcx>, - mut f: F, -) -> ControlFlow -where - F: FnMut(AbstractConst<'tcx>) -> ControlFlow, -{ - #[instrument(skip(tcx, f), level = "debug")] - fn recurse<'tcx, R>( - tcx: TyCtxt<'tcx>, - ct: AbstractConst<'tcx>, - f: &mut dyn FnMut(AbstractConst<'tcx>) -> ControlFlow, - ) -> ControlFlow { - f(ct)?; - let root = ct.root(tcx); - debug!(?root); - match root { - Node::Leaf(_) => ControlFlow::CONTINUE, - Node::Binop(_, l, r) => { - recurse(tcx, ct.subtree(l), f)?; - recurse(tcx, ct.subtree(r), f) - } - Node::UnaryOp(_, v) => recurse(tcx, ct.subtree(v), f), - Node::FunctionCall(func, args) => { - recurse(tcx, ct.subtree(func), f)?; - args.iter().try_for_each(|&arg| recurse(tcx, ct.subtree(arg), f)) - } - Node::Cast(_, operand, _) => recurse(tcx, ct.subtree(operand), f), - } - } - - recurse(tcx, ct, &mut f) -} - -struct ConstUnifyCtxt<'tcx> { - tcx: TyCtxt<'tcx>, - param_env: ty::ParamEnv<'tcx>, -} - -impl<'tcx> ConstUnifyCtxt<'tcx> { - // Substitutes generics repeatedly to allow AbstractConsts to unify where a - // ConstKind::Unevaluated could be turned into an AbstractConst that would unify e.g. - // Param(N) should unify with Param(T), substs: [Unevaluated("T2", [Unevaluated("T3", [Param(N)])])] - #[inline] - #[instrument(skip(self), level = "debug")] - fn try_replace_substs_in_root( - &self, - mut abstr_const: AbstractConst<'tcx>, - ) -> Option> { - while let Node::Leaf(ct) = abstr_const.root(self.tcx) { - match AbstractConst::from_const(self.tcx, ct) { - Ok(Some(act)) => abstr_const = act, - Ok(None) => break, - Err(_) => return None, - } - } - - Some(abstr_const) - } - - /// Tries to unify two abstract constants using structural equality. - #[instrument(skip(self), level = "debug")] - fn try_unify(&self, a: AbstractConst<'tcx>, b: AbstractConst<'tcx>) -> bool { - let a = if let Some(a) = self.try_replace_substs_in_root(a) { - a - } else { - return true; - }; - - let b = if let Some(b) = self.try_replace_substs_in_root(b) { - b - } else { - return true; - }; - - let a_root = a.root(self.tcx); - let b_root = b.root(self.tcx); - debug!(?a_root, ?b_root); - - match (a_root, b_root) { - (Node::Leaf(a_ct), Node::Leaf(b_ct)) => { - let a_ct = a_ct.eval(self.tcx, self.param_env); - debug!("a_ct evaluated: {:?}", a_ct); - let b_ct = b_ct.eval(self.tcx, self.param_env); - debug!("b_ct evaluated: {:?}", b_ct); - - if a_ct.ty() != b_ct.ty() { - return false; - } - - match (a_ct.kind(), b_ct.kind()) { - // We can just unify errors with everything to reduce the amount of - // emitted errors here. - (ty::ConstKind::Error(_), _) | (_, ty::ConstKind::Error(_)) => true, - (ty::ConstKind::Param(a_param), ty::ConstKind::Param(b_param)) => { - a_param == b_param - } - (ty::ConstKind::Value(a_val), ty::ConstKind::Value(b_val)) => a_val == b_val, - // If we have `fn a() -> [u8; N + 1]` and `fn b() -> [u8; 1 + M]` - // we do not want to use `assert_eq!(a(), b())` to infer that `N` and `M` have to be `1`. This - // means that we only allow inference variables if they are equal. - (ty::ConstKind::Infer(a_val), ty::ConstKind::Infer(b_val)) => a_val == b_val, - // We expand generic anonymous constants at the start of this function, so this - // branch should only be taking when dealing with associated constants, at - // which point directly comparing them seems like the desired behavior. - // - // FIXME(generic_const_exprs): This isn't actually the case. - // We also take this branch for concrete anonymous constants and - // expand generic anonymous constants with concrete substs. - (ty::ConstKind::Unevaluated(a_uv), ty::ConstKind::Unevaluated(b_uv)) => { - a_uv == b_uv - } - // FIXME(generic_const_exprs): We may want to either actually try - // to evaluate `a_ct` and `b_ct` if they are are fully concrete or something like - // this, for now we just return false here. - _ => false, - } - } - (Node::Binop(a_op, al, ar), Node::Binop(b_op, bl, br)) if a_op == b_op => { - self.try_unify(a.subtree(al), b.subtree(bl)) - && self.try_unify(a.subtree(ar), b.subtree(br)) - } - (Node::UnaryOp(a_op, av), Node::UnaryOp(b_op, bv)) if a_op == b_op => { - self.try_unify(a.subtree(av), b.subtree(bv)) - } - (Node::FunctionCall(a_f, a_args), Node::FunctionCall(b_f, b_args)) - if a_args.len() == b_args.len() => - { - self.try_unify(a.subtree(a_f), b.subtree(b_f)) - && iter::zip(a_args, b_args) - .all(|(&an, &bn)| self.try_unify(a.subtree(an), b.subtree(bn))) - } - (Node::Cast(a_kind, a_operand, a_ty), Node::Cast(b_kind, b_operand, b_ty)) - if (a_ty == b_ty) && (a_kind == b_kind) => - { - self.try_unify(a.subtree(a_operand), b.subtree(b_operand)) - } - // use this over `_ => false` to make adding variants to `Node` less error prone - (Node::Cast(..), _) - | (Node::FunctionCall(..), _) - | (Node::UnaryOp(..), _) - | (Node::Binop(..), _) - | (Node::Leaf(..), _) => false, - } - } -} diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs index 34f4a9f7902..0ef9d3af15a 100644 --- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs +++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs @@ -24,8 +24,8 @@ use rustc_hir::Item; use rustc_hir::Node; use rustc_infer::infer::error_reporting::same_type_modulo_infer; use rustc_infer::traits::{AmbiguousSelection, TraitEngine}; -use rustc_middle::thir::abstract_const::NotConstEvaluatable; use rustc_middle::traits::select::OverflowError; +use rustc_middle::ty::abstract_const::NotConstEvaluatable; use rustc_middle::ty::error::ExpectedFound; use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable}; use rustc_middle::ty::{ diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs index 78600652254..4aa62f8078d 100644 --- a/compiler/rustc_trait_selection/src/traits/fulfill.rs +++ b/compiler/rustc_trait_selection/src/traits/fulfill.rs @@ -6,7 +6,7 @@ use rustc_data_structures::obligation_forest::{ObligationForest, ObligationProce use rustc_infer::traits::ProjectionCacheKey; use rustc_infer::traits::{SelectionError, TraitEngine, TraitEngineExt as _, TraitObligation}; use rustc_middle::mir::interpret::ErrorHandled; -use rustc_middle::thir::abstract_const::NotConstEvaluatable; +use rustc_middle::ty::abstract_const::NotConstEvaluatable; use rustc_middle::ty::error::{ExpectedFound, TypeError}; use rustc_middle::ty::subst::SubstsRef; use rustc_middle::ty::ToPredicate; diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs index 74d2eb17b6b..f6a8dd6bbf9 100644 --- a/compiler/rustc_trait_selection/src/traits/mod.rs +++ b/compiler/rustc_trait_selection/src/traits/mod.rs @@ -845,23 +845,9 @@ pub fn provide(providers: &mut ty::query::Providers) { vtable_entries, vtable_trait_upcasting_coercion_new_vptr_slot, subst_and_check_impossible_predicates, - thir_abstract_const: |tcx, def_id| { - let def_id = def_id.expect_local(); - if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) { - tcx.thir_abstract_const_of_const_arg(def) - } else { - const_evaluatable::thir_abstract_const(tcx, ty::WithOptConstParam::unknown(def_id)) - } - }, - thir_abstract_const_of_const_arg: |tcx, (did, param_did)| { - const_evaluatable::thir_abstract_const( - tcx, - ty::WithOptConstParam { did, const_param_did: Some(param_did) }, - ) - }, try_unify_abstract_consts: |tcx, param_env_and| { let (param_env, (a, b)) = param_env_and.into_parts(); - const_evaluatable::try_unify_abstract_consts(tcx, (a, b), param_env) + rustc_middle::ty::abstract_const::try_unify_abstract_consts(tcx, (a, b), param_env) }, ..*providers }; diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs index ac1811244ca..2921ce0ffef 100644 --- a/compiler/rustc_trait_selection/src/traits/object_safety.rs +++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs @@ -11,12 +11,12 @@ use super::elaborate_predicates; use crate::infer::TyCtxtInferExt; -use crate::traits::const_evaluatable::{self, AbstractConst}; use crate::traits::query::evaluate_obligation::InferCtxtExt; use crate::traits::{self, Obligation, ObligationCause}; use rustc_errors::{FatalError, MultiSpan}; use rustc_hir as hir; use rustc_hir::def_id::DefId; +use rustc_middle::ty::abstract_const::{walk_abstract_const, AbstractConst}; use rustc_middle::ty::subst::{GenericArg, InternalSubsts, Subst}; use rustc_middle::ty::{ self, EarlyBinder, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor, @@ -841,15 +841,13 @@ fn contains_illegal_self_type_reference<'tcx, T: TypeVisitable<'tcx>>( // // This shouldn't really matter though as we can't really use any // constants which are not considered const evaluatable. - use rustc_middle::thir::abstract_const::Node; + use rustc_middle::ty::abstract_const::Node; if let Ok(Some(ct)) = AbstractConst::new(self.tcx, uv.shrink()) { - const_evaluatable::walk_abstract_const(self.tcx, ct, |node| { - match node.root(self.tcx) { - Node::Leaf(leaf) => self.visit_const(leaf), - Node::Cast(_, _, ty) => self.visit_ty(ty), - Node::Binop(..) | Node::UnaryOp(..) | Node::FunctionCall(_, _) => { - ControlFlow::CONTINUE - } + walk_abstract_const(self.tcx, ct, |node| match node.root(self.tcx) { + Node::Leaf(leaf) => self.visit_const(leaf), + Node::Cast(_, _, ty) => self.visit_ty(ty), + Node::Binop(..) | Node::UnaryOp(..) | Node::FunctionCall(_, _) => { + ControlFlow::CONTINUE } }) } else { diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs index 2bb53a466ca..7c5673c8632 100644 --- a/compiler/rustc_trait_selection/src/traits/select/mod.rs +++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs @@ -32,7 +32,7 @@ use rustc_hir::def_id::DefId; use rustc_infer::infer::LateBoundRegionConversionTime; use rustc_middle::dep_graph::{DepKind, DepNodeIndex}; use rustc_middle::mir::interpret::ErrorHandled; -use rustc_middle::thir::abstract_const::NotConstEvaluatable; +use rustc_middle::ty::abstract_const::NotConstEvaluatable; use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams}; use rustc_middle::ty::fold::BottomUpFolder; use rustc_middle::ty::print::with_no_trimmed_paths; diff --git a/compiler/rustc_ty_utils/Cargo.toml b/compiler/rustc_ty_utils/Cargo.toml index d03d675bfd2..caad2ed4274 100644 --- a/compiler/rustc_ty_utils/Cargo.toml +++ b/compiler/rustc_ty_utils/Cargo.toml @@ -15,3 +15,4 @@ rustc_session = { path = "../rustc_session" } rustc_target = { path = "../rustc_target" } rustc_trait_selection = { path = "../rustc_trait_selection" } rustc_type_ir = { path = "../rustc_type_ir" } +rustc_index = { path = "../rustc_index" } diff --git a/compiler/rustc_ty_utils/src/consts.rs b/compiler/rustc_ty_utils/src/consts.rs index 0b83cdb78dc..80957d64465 100644 --- a/compiler/rustc_ty_utils/src/consts.rs +++ b/compiler/rustc_ty_utils/src/consts.rs @@ -1,4 +1,12 @@ -use rustc_middle::ty::{self, TyCtxt}; +use rustc_errors::ErrorGuaranteed; +use rustc_hir::def::DefKind; +use rustc_hir::def_id::LocalDefId; +use rustc_index::vec::IndexVec; +use rustc_middle::mir::interpret::{LitToConstError, LitToConstInput}; +use rustc_middle::ty::abstract_const::{CastKind, Node, NodeId}; +use rustc_middle::ty::{self, TyCtxt, TypeVisitable}; +use rustc_middle::{mir, thir}; +use rustc_span::Span; use rustc_target::abi::VariantIdx; use std::iter; @@ -72,6 +80,390 @@ pub(crate) fn destructure_const<'tcx>( ty::DestructuredConst { variant, fields } } -pub fn provide(providers: &mut ty::query::Providers) { - *providers = ty::query::Providers { destructure_const, ..*providers }; +pub struct AbstractConstBuilder<'a, 'tcx> { + tcx: TyCtxt<'tcx>, + body_id: thir::ExprId, + body: &'a thir::Thir<'tcx>, + /// The current WIP node tree. + nodes: IndexVec>, +} + +impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> { + fn root_span(&self) -> Span { + self.body.exprs[self.body_id].span + } + + fn error(&mut self, span: Span, msg: &str) -> Result { + let reported = self + .tcx + .sess + .struct_span_err(self.root_span(), "overly complex generic constant") + .span_label(span, msg) + .help("consider moving this anonymous constant into a `const` function") + .emit(); + + Err(reported) + } + fn maybe_supported_error(&mut self, span: Span, msg: &str) -> Result { + let reported = self + .tcx + .sess + .struct_span_err(self.root_span(), "overly complex generic constant") + .span_label(span, msg) + .help("consider moving this anonymous constant into a `const` function") + .note("this operation may be supported in the future") + .emit(); + + Err(reported) + } + + #[instrument(skip(tcx, body, body_id), level = "debug")] + pub fn new( + tcx: TyCtxt<'tcx>, + (body, body_id): (&'a thir::Thir<'tcx>, thir::ExprId), + ) -> Result>, ErrorGuaranteed> { + let builder = AbstractConstBuilder { tcx, body_id, body, nodes: IndexVec::new() }; + + struct IsThirPolymorphic<'a, 'tcx> { + is_poly: bool, + thir: &'a thir::Thir<'tcx>, + } + + use crate::rustc_middle::thir::visit::Visitor; + use thir::visit; + + impl<'a, 'tcx> IsThirPolymorphic<'a, 'tcx> { + fn expr_is_poly(&mut self, expr: &thir::Expr<'tcx>) -> bool { + if expr.ty.has_param_types_or_consts() { + return true; + } + + match expr.kind { + thir::ExprKind::NamedConst { substs, .. } => substs.has_param_types_or_consts(), + thir::ExprKind::ConstParam { .. } => true, + thir::ExprKind::Repeat { value, count } => { + self.visit_expr(&self.thir()[value]); + count.has_param_types_or_consts() + } + _ => false, + } + } + + fn pat_is_poly(&mut self, pat: &thir::Pat<'tcx>) -> bool { + if pat.ty.has_param_types_or_consts() { + return true; + } + + match pat.kind.as_ref() { + thir::PatKind::Constant { value } => value.has_param_types_or_consts(), + thir::PatKind::Range(thir::PatRange { lo, hi, .. }) => { + lo.has_param_types_or_consts() || hi.has_param_types_or_consts() + } + _ => false, + } + } + } + + impl<'a, 'tcx> visit::Visitor<'a, 'tcx> for IsThirPolymorphic<'a, 'tcx> { + fn thir(&self) -> &'a thir::Thir<'tcx> { + &self.thir + } + + #[instrument(skip(self), level = "debug")] + fn visit_expr(&mut self, expr: &thir::Expr<'tcx>) { + self.is_poly |= self.expr_is_poly(expr); + if !self.is_poly { + visit::walk_expr(self, expr) + } + } + + #[instrument(skip(self), level = "debug")] + fn visit_pat(&mut self, pat: &thir::Pat<'tcx>) { + self.is_poly |= self.pat_is_poly(pat); + if !self.is_poly { + visit::walk_pat(self, pat); + } + } + } + + let mut is_poly_vis = IsThirPolymorphic { is_poly: false, thir: body }; + visit::walk_expr(&mut is_poly_vis, &body[body_id]); + debug!("AbstractConstBuilder: is_poly={}", is_poly_vis.is_poly); + if !is_poly_vis.is_poly { + return Ok(None); + } + + Ok(Some(builder)) + } + + /// We do not allow all binary operations in abstract consts, so filter disallowed ones. + fn check_binop(op: mir::BinOp) -> bool { + use mir::BinOp::*; + match op { + Add | Sub | Mul | Div | Rem | BitXor | BitAnd | BitOr | Shl | Shr | Eq | Lt | Le + | Ne | Ge | Gt => true, + Offset => false, + } + } + + /// While we currently allow all unary operations, we still want to explicitly guard against + /// future changes here. + fn check_unop(op: mir::UnOp) -> bool { + use mir::UnOp::*; + match op { + Not | Neg => true, + } + } + + /// Builds the abstract const by walking the thir and bailing out when + /// encountering an unsupported operation. + pub fn build(mut self) -> Result<&'tcx [Node<'tcx>], ErrorGuaranteed> { + debug!("Abstractconstbuilder::build: body={:?}", &*self.body); + self.recurse_build(self.body_id)?; + + for n in self.nodes.iter() { + if let Node::Leaf(ct) = n { + if let ty::ConstKind::Unevaluated(ct) = ct.kind() { + // `AbstractConst`s should not contain any promoteds as they require references which + // are not allowed. + assert_eq!(ct.promoted, None); + assert_eq!(ct, self.tcx.erase_regions(ct)); + } + } + } + + Ok(self.tcx.arena.alloc_from_iter(self.nodes.into_iter())) + } + + fn recurse_build(&mut self, node: thir::ExprId) -> Result { + use thir::ExprKind; + let node = &self.body.exprs[node]; + Ok(match &node.kind { + // I dont know if handling of these 3 is correct + &ExprKind::Scope { value, .. } => self.recurse_build(value)?, + &ExprKind::PlaceTypeAscription { source, .. } + | &ExprKind::ValueTypeAscription { source, .. } => self.recurse_build(source)?, + &ExprKind::Literal { lit, neg} => { + let sp = node.span; + let constant = + match self.tcx.at(sp).lit_to_const(LitToConstInput { lit: &lit.node, ty: node.ty, neg }) { + Ok(c) => c, + Err(LitToConstError::Reported) => { + self.tcx.const_error(node.ty) + } + Err(LitToConstError::TypeError) => { + bug!("encountered type error in lit_to_const") + } + }; + + self.nodes.push(Node::Leaf(constant)) + } + &ExprKind::NonHirLiteral { lit , user_ty: _} => { + let val = ty::ValTree::from_scalar_int(lit); + self.nodes.push(Node::Leaf(ty::Const::from_value(self.tcx, val, node.ty))) + } + &ExprKind::ZstLiteral { user_ty: _ } => { + let val = ty::ValTree::zst(); + self.nodes.push(Node::Leaf(ty::Const::from_value(self.tcx, val, node.ty))) + } + &ExprKind::NamedConst { def_id, substs, user_ty: _ } => { + let uneval = ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs); + + let constant = self.tcx.mk_const(ty::ConstS { + kind: ty::ConstKind::Unevaluated(uneval), + ty: node.ty, + }); + + self.nodes.push(Node::Leaf(constant)) + } + + ExprKind::ConstParam {param, ..} => { + let const_param = self.tcx.mk_const(ty::ConstS { + kind: ty::ConstKind::Param(*param), + ty: node.ty, + }); + self.nodes.push(Node::Leaf(const_param)) + } + + ExprKind::Call { fun, args, .. } => { + let fun = self.recurse_build(*fun)?; + + let mut new_args = Vec::::with_capacity(args.len()); + for &id in args.iter() { + new_args.push(self.recurse_build(id)?); + } + let new_args = self.tcx.arena.alloc_slice(&new_args); + self.nodes.push(Node::FunctionCall(fun, new_args)) + } + &ExprKind::Binary { op, lhs, rhs } if Self::check_binop(op) => { + let lhs = self.recurse_build(lhs)?; + let rhs = self.recurse_build(rhs)?; + self.nodes.push(Node::Binop(op, lhs, rhs)) + } + &ExprKind::Unary { op, arg } if Self::check_unop(op) => { + let arg = self.recurse_build(arg)?; + self.nodes.push(Node::UnaryOp(op, arg)) + } + // This is necessary so that the following compiles: + // + // ``` + // fn foo(a: [(); N + 1]) { + // bar::<{ N + 1 }>(); + // } + // ``` + ExprKind::Block { body: thir::Block { stmts: box [], expr: Some(e), .. } } => { + self.recurse_build(*e)? + } + // `ExprKind::Use` happens when a `hir::ExprKind::Cast` is a + // "coercion cast" i.e. using a coercion or is a no-op. + // This is important so that `N as usize as usize` doesnt unify with `N as usize`. (untested) + &ExprKind::Use { source } => { + let arg = self.recurse_build(source)?; + self.nodes.push(Node::Cast(CastKind::Use, arg, node.ty)) + } + &ExprKind::Cast { source } => { + let arg = self.recurse_build(source)?; + self.nodes.push(Node::Cast(CastKind::As, arg, node.ty)) + } + ExprKind::Borrow{ arg, ..} => { + let arg_node = &self.body.exprs[*arg]; + + // Skip reborrows for now until we allow Deref/Borrow/AddressOf + // expressions. + // FIXME(generic_const_exprs): Verify/explain why this is sound + if let ExprKind::Deref {arg} = arg_node.kind { + self.recurse_build(arg)? + } else { + self.maybe_supported_error( + node.span, + "borrowing is not supported in generic constants", + )? + } + } + // FIXME(generic_const_exprs): We may want to support these. + ExprKind::AddressOf { .. } | ExprKind::Deref {..}=> self.maybe_supported_error( + node.span, + "dereferencing or taking the address is not supported in generic constants", + )?, + ExprKind::Repeat { .. } | ExprKind::Array { .. } => self.maybe_supported_error( + node.span, + "array construction is not supported in generic constants", + )?, + ExprKind::Block { .. } => self.maybe_supported_error( + node.span, + "blocks are not supported in generic constant", + )?, + ExprKind::NeverToAny { .. } => self.maybe_supported_error( + node.span, + "converting nevers to any is not supported in generic constant", + )?, + ExprKind::Tuple { .. } => self.maybe_supported_error( + node.span, + "tuple construction is not supported in generic constants", + )?, + ExprKind::Index { .. } => self.maybe_supported_error( + node.span, + "indexing is not supported in generic constant", + )?, + ExprKind::Field { .. } => self.maybe_supported_error( + node.span, + "field access is not supported in generic constant", + )?, + ExprKind::ConstBlock { .. } => self.maybe_supported_error( + node.span, + "const blocks are not supported in generic constant", + )?, + ExprKind::Adt(_) => self.maybe_supported_error( + node.span, + "struct/enum construction is not supported in generic constants", + )?, + // dont know if this is correct + ExprKind::Pointer { .. } => + self.error(node.span, "pointer casts are not allowed in generic constants")?, + ExprKind::Yield { .. } => + self.error(node.span, "generator control flow is not allowed in generic constants")?, + ExprKind::Continue { .. } | ExprKind::Break { .. } | ExprKind::Loop { .. } => self + .error( + node.span, + "loops and loop control flow are not supported in generic constants", + )?, + ExprKind::Box { .. } => + self.error(node.span, "allocations are not allowed in generic constants")?, + + ExprKind::Unary { .. } => unreachable!(), + // we handle valid unary/binary ops above + ExprKind::Binary { .. } => + self.error(node.span, "unsupported binary operation in generic constants")?, + ExprKind::LogicalOp { .. } => + self.error(node.span, "unsupported operation in generic constants, short-circuiting operations would imply control flow")?, + ExprKind::Assign { .. } | ExprKind::AssignOp { .. } => { + self.error(node.span, "assignment is not supported in generic constants")? + } + ExprKind::Closure { .. } | ExprKind::Return { .. } => self.error( + node.span, + "closures and function keywords are not supported in generic constants", + )?, + // let expressions imply control flow + ExprKind::Match { .. } | ExprKind::If { .. } | ExprKind::Let { .. } => + self.error(node.span, "control flow is not supported in generic constants")?, + ExprKind::InlineAsm { .. } => { + self.error(node.span, "assembly is not supported in generic constants")? + } + + // we dont permit let stmts so `VarRef` and `UpvarRef` cant happen + ExprKind::VarRef { .. } + | ExprKind::UpvarRef { .. } + | ExprKind::StaticRef { .. } + | ExprKind::ThreadLocalRef(_) => { + self.error(node.span, "unsupported operation in generic constant")? + } + }) + } +} + +/// Builds an abstract const, do not use this directly, but use `AbstractConst::new` instead. +pub fn thir_abstract_const<'tcx>( + tcx: TyCtxt<'tcx>, + def: ty::WithOptConstParam, +) -> Result]>, ErrorGuaranteed> { + if tcx.features().generic_const_exprs { + match tcx.def_kind(def.did) { + // FIXME(generic_const_exprs): We currently only do this for anonymous constants, + // meaning that we do not look into associated constants. I(@lcnr) am not yet sure whether + // we want to look into them or treat them as opaque projections. + // + // Right now we do neither of that and simply always fail to unify them. + DefKind::AnonConst | DefKind::InlineConst => (), + _ => return Ok(None), + } + + let body = tcx.thir_body(def)?; + + AbstractConstBuilder::new(tcx, (&*body.0.borrow(), body.1))? + .map(AbstractConstBuilder::build) + .transpose() + } else { + Ok(None) + } +} + +pub fn provide(providers: &mut ty::query::Providers) { + *providers = ty::query::Providers { + destructure_const, + thir_abstract_const: |tcx, def_id| { + let def_id = def_id.expect_local(); + if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) { + tcx.thir_abstract_const_of_const_arg(def) + } else { + thir_abstract_const(tcx, ty::WithOptConstParam::unknown(def_id)) + } + }, + thir_abstract_const_of_const_arg: |tcx, (did, param_did)| { + thir_abstract_const( + tcx, + ty::WithOptConstParam { did, const_param_did: Some(param_did) }, + ) + }, + ..*providers + }; } diff --git a/compiler/rustc_ty_utils/src/lib.rs b/compiler/rustc_ty_utils/src/lib.rs index 7624d31b40b..09f5c2a11aa 100644 --- a/compiler/rustc_ty_utils/src/lib.rs +++ b/compiler/rustc_ty_utils/src/lib.rs @@ -7,6 +7,8 @@ #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")] #![feature(control_flow_enum)] #![feature(let_else)] +#![feature(never_type)] +#![feature(box_patterns)] #![recursion_limit = "256"] #[macro_use]