| use rustc_hir as hir; |
| use rustc_hir::def_id::DefId; |
| use rustc_index::Idx; |
| use rustc_infer::infer::{InferCtxt, TyCtxtInferExt}; |
| use rustc_infer::traits::Obligation; |
| use rustc_middle::mir; |
| use rustc_middle::thir::{FieldPat, Pat, PatKind}; |
| use rustc_middle::ty::{self, Ty, TyCtxt, ValTree}; |
| use rustc_session::lint; |
| use rustc_span::Span; |
| use rustc_target::abi::{FieldIdx, VariantIdx}; |
| use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt; |
| use rustc_trait_selection::traits::{self, ObligationCause}; |
| |
| use std::cell::Cell; |
| |
| use super::PatCtxt; |
| use crate::errors::{ |
| FloatPattern, IndirectStructuralMatch, InvalidPattern, NontrivialStructuralMatch, |
| PointerPattern, TypeNotStructural, UnionPattern, UnsizedPattern, |
| }; |
| |
| impl<'a, 'tcx> PatCtxt<'a, 'tcx> { |
| /// Converts an evaluated constant to a pattern (if possible). |
| /// This means aggregate values (like structs and enums) are converted |
| /// to a pattern that matches the value (as if you'd compared via structural equality). |
| #[instrument(level = "debug", skip(self), ret)] |
| pub(super) fn const_to_pat( |
| &self, |
| cv: mir::ConstantKind<'tcx>, |
| id: hir::HirId, |
| span: Span, |
| check_body_for_struct_match_violation: Option<DefId>, |
| ) -> Box<Pat<'tcx>> { |
| let infcx = self.tcx.infer_ctxt().build(); |
| let mut convert = ConstToPat::new(self, id, span, infcx); |
| convert.to_pat(cv, check_body_for_struct_match_violation) |
| } |
| } |
| |
| struct ConstToPat<'tcx> { |
| id: hir::HirId, |
| span: Span, |
| param_env: ty::ParamEnv<'tcx>, |
| |
| // This tracks if we emitted some hard error for a given const value, so that |
| // we will not subsequently issue an irrelevant lint for the same const |
| // value. |
| saw_const_match_error: Cell<bool>, |
| |
| // This tracks if we emitted some diagnostic for a given const value, so that |
| // we will not subsequently issue an irrelevant lint for the same const |
| // value. |
| saw_const_match_lint: Cell<bool>, |
| |
| // For backcompat we need to keep allowing non-structurally-eq types behind references. |
| // See also all the `cant-hide-behind` tests. |
| behind_reference: Cell<bool>, |
| |
| // inference context used for checking `T: Structural` bounds. |
| infcx: InferCtxt<'tcx>, |
| |
| treat_byte_string_as_slice: bool, |
| } |
| |
| /// This error type signals that we encountered a non-struct-eq situation. |
| /// We bubble this up in order to get back to the reference destructuring and make that emit |
| /// a const pattern instead of a deref pattern. This allows us to simply call `PartialEq::eq` |
| /// on such patterns (since that function takes a reference) and not have to jump through any |
| /// hoops to get a reference to the value. |
| #[derive(Debug)] |
| struct FallbackToConstRef; |
| |
| impl<'tcx> ConstToPat<'tcx> { |
| fn new( |
| pat_ctxt: &PatCtxt<'_, 'tcx>, |
| id: hir::HirId, |
| span: Span, |
| infcx: InferCtxt<'tcx>, |
| ) -> Self { |
| trace!(?pat_ctxt.typeck_results.hir_owner); |
| ConstToPat { |
| id, |
| span, |
| infcx, |
| param_env: pat_ctxt.param_env, |
| saw_const_match_error: Cell::new(false), |
| saw_const_match_lint: Cell::new(false), |
| behind_reference: Cell::new(false), |
| treat_byte_string_as_slice: pat_ctxt |
| .typeck_results |
| .treat_byte_string_as_slice |
| .contains(&id.local_id), |
| } |
| } |
| |
| fn tcx(&self) -> TyCtxt<'tcx> { |
| self.infcx.tcx |
| } |
| |
| fn type_marked_structural(&self, ty: Ty<'tcx>) -> bool { |
| ty.is_structural_eq_shallow(self.infcx.tcx) |
| } |
| |
| fn to_pat( |
| &mut self, |
| cv: mir::ConstantKind<'tcx>, |
| check_body_for_struct_match_violation: Option<DefId>, |
| ) -> Box<Pat<'tcx>> { |
| trace!(self.treat_byte_string_as_slice); |
| // This method is just a wrapper handling a validity check; the heavy lifting is |
| // performed by the recursive `recur` method, which is not meant to be |
| // invoked except by this method. |
| // |
| // once indirect_structural_match is a full fledged error, this |
| // level of indirection can be eliminated |
| |
| let mir_structural_match_violation = check_body_for_struct_match_violation.map(|def_id| { |
| // `mir_const_qualif` must be called with the `DefId` of the item where the const is |
| // defined, not where it is declared. The difference is significant for associated |
| // constants. |
| self.tcx().mir_const_qualif(def_id).custom_eq |
| }); |
| debug!(?check_body_for_struct_match_violation, ?mir_structural_match_violation); |
| |
| let inlined_const_as_pat = match cv { |
| mir::ConstantKind::Ty(c) => match c.kind() { |
| ty::ConstKind::Param(_) |
| | ty::ConstKind::Infer(_) |
| | ty::ConstKind::Bound(_, _) |
| | ty::ConstKind::Placeholder(_) |
| | ty::ConstKind::Unevaluated(_) |
| | ty::ConstKind::Error(_) |
| | ty::ConstKind::Expr(_) => { |
| span_bug!(self.span, "unexpected const in `to_pat`: {:?}", c.kind()) |
| } |
| ty::ConstKind::Value(valtree) => self |
| .recur(valtree, cv.ty(), mir_structural_match_violation.unwrap_or(false)) |
| .unwrap_or_else(|_| { |
| Box::new(Pat { |
| span: self.span, |
| ty: cv.ty(), |
| kind: PatKind::Constant { value: cv }, |
| }) |
| }), |
| }, |
| mir::ConstantKind::Unevaluated(_, _) => { |
| span_bug!(self.span, "unevaluated const in `to_pat`: {cv:?}") |
| } |
| mir::ConstantKind::Val(_, _) => Box::new(Pat { |
| span: self.span, |
| ty: cv.ty(), |
| kind: PatKind::Constant { value: cv }, |
| }), |
| }; |
| |
| if !self.saw_const_match_error.get() { |
| // If we were able to successfully convert the const to some pat, |
| // double-check that all types in the const implement `Structural`. |
| |
| let structural = |
| traits::search_for_structural_match_violation(self.span, self.tcx(), cv.ty()); |
| debug!( |
| "search_for_structural_match_violation cv.ty: {:?} returned: {:?}", |
| cv.ty(), |
| structural |
| ); |
| |
| // This can occur because const qualification treats all associated constants as |
| // opaque, whereas `search_for_structural_match_violation` tries to monomorphize them |
| // before it runs. |
| // |
| // FIXME(#73448): Find a way to bring const qualification into parity with |
| // `search_for_structural_match_violation`. |
| if structural.is_none() && mir_structural_match_violation.unwrap_or(false) { |
| warn!("MIR const-checker found novel structural match violation. See #73448."); |
| return inlined_const_as_pat; |
| } |
| |
| if let Some(non_sm_ty) = structural { |
| if !self.type_may_have_partial_eq_impl(cv.ty()) { |
| if let ty::Adt(def, ..) = non_sm_ty.kind() { |
| if def.is_union() { |
| let err = UnionPattern { span: self.span }; |
| self.tcx().sess.emit_err(err); |
| } else { |
| // fatal avoids ICE from resolution of nonexistent method (rare case). |
| self.tcx() |
| .sess |
| .emit_fatal(TypeNotStructural { span: self.span, non_sm_ty }); |
| } |
| } else { |
| let err = InvalidPattern { span: self.span, non_sm_ty }; |
| self.tcx().sess.emit_err(err); |
| return Box::new(Pat { span: self.span, ty: cv.ty(), kind: PatKind::Wild }); |
| } |
| } else if !self.saw_const_match_lint.get() { |
| if let Some(mir_structural_match_violation) = mir_structural_match_violation { |
| match non_sm_ty.kind() { |
| ty::RawPtr(pointee) |
| if pointee.ty.is_sized(self.tcx(), self.param_env) => {} |
| ty::FnPtr(..) | ty::RawPtr(..) => { |
| self.tcx().emit_spanned_lint( |
| lint::builtin::POINTER_STRUCTURAL_MATCH, |
| self.id, |
| self.span, |
| PointerPattern, |
| ); |
| } |
| ty::Adt(..) if mir_structural_match_violation => { |
| self.tcx().emit_spanned_lint( |
| lint::builtin::INDIRECT_STRUCTURAL_MATCH, |
| self.id, |
| self.span, |
| IndirectStructuralMatch { non_sm_ty }, |
| ); |
| } |
| _ => { |
| debug!( |
| "`search_for_structural_match_violation` found one, but `CustomEq` was \ |
| not in the qualifs for that `const`" |
| ); |
| } |
| } |
| } |
| } |
| } else if !self.saw_const_match_lint.get() { |
| match cv.ty().kind() { |
| ty::RawPtr(pointee) if pointee.ty.is_sized(self.tcx(), self.param_env) => {} |
| ty::FnPtr(..) | ty::RawPtr(..) => { |
| self.tcx().emit_spanned_lint( |
| lint::builtin::POINTER_STRUCTURAL_MATCH, |
| self.id, |
| self.span, |
| PointerPattern, |
| ); |
| } |
| _ => {} |
| } |
| } |
| } |
| |
| inlined_const_as_pat |
| } |
| |
| #[instrument(level = "trace", skip(self), ret)] |
| fn type_may_have_partial_eq_impl(&self, ty: Ty<'tcx>) -> bool { |
| // double-check there even *is* a semantic `PartialEq` to dispatch to. |
| // |
| // (If there isn't, then we can safely issue a hard |
| // error, because that's never worked, due to compiler |
| // using `PartialEq::eq` in this scenario in the past.) |
| let partial_eq_trait_id = |
| self.tcx().require_lang_item(hir::LangItem::PartialEq, Some(self.span)); |
| let partial_eq_obligation = Obligation::new( |
| self.tcx(), |
| ObligationCause::dummy(), |
| self.param_env, |
| ty::TraitRef::new(self.tcx(), partial_eq_trait_id, [ty, ty]), |
| ); |
| |
| // FIXME: should this call a `predicate_must_hold` variant instead? |
| self.infcx.predicate_may_hold(&partial_eq_obligation) |
| } |
| |
| fn field_pats( |
| &self, |
| vals: impl Iterator<Item = (ValTree<'tcx>, Ty<'tcx>)>, |
| ) -> Result<Vec<FieldPat<'tcx>>, FallbackToConstRef> { |
| vals.enumerate() |
| .map(|(idx, (val, ty))| { |
| let field = FieldIdx::new(idx); |
| // Patterns can only use monomorphic types. |
| let ty = self.tcx().normalize_erasing_regions(self.param_env, ty); |
| Ok(FieldPat { field, pattern: self.recur(val, ty, false)? }) |
| }) |
| .collect() |
| } |
| |
| // Recursive helper for `to_pat`; invoke that (instead of calling this directly). |
| #[instrument(skip(self), level = "debug")] |
| fn recur( |
| &self, |
| cv: ValTree<'tcx>, |
| ty: Ty<'tcx>, |
| mir_structural_match_violation: bool, |
| ) -> Result<Box<Pat<'tcx>>, FallbackToConstRef> { |
| let id = self.id; |
| let span = self.span; |
| let tcx = self.tcx(); |
| let param_env = self.param_env; |
| |
| let kind = match ty.kind() { |
| ty::Float(_) => { |
| self.saw_const_match_lint.set(true); |
| tcx.emit_spanned_lint( |
| lint::builtin::ILLEGAL_FLOATING_POINT_LITERAL_PATTERN, |
| id, |
| span, |
| FloatPattern, |
| ); |
| return Err(FallbackToConstRef); |
| } |
| // If the type is not structurally comparable, just emit the constant directly, |
| // causing the pattern match code to treat it opaquely. |
| // FIXME: This code doesn't emit errors itself, the caller emits the errors. |
| // So instead of specific errors, you just get blanket errors about the whole |
| // const type. See |
| // https://github.com/rust-lang/rust/pull/70743#discussion_r404701963 for |
| // details. |
| // Backwards compatibility hack because we can't cause hard errors on these |
| // types, so we compare them via `PartialEq::eq` at runtime. |
| ty::Adt(..) if !self.type_marked_structural(ty) && self.behind_reference.get() => { |
| if !self.saw_const_match_error.get() && !self.saw_const_match_lint.get() { |
| self.saw_const_match_lint.set(true); |
| tcx.emit_spanned_lint( |
| lint::builtin::INDIRECT_STRUCTURAL_MATCH, |
| id, |
| span, |
| IndirectStructuralMatch { non_sm_ty: ty }, |
| ); |
| } |
| // Since we are behind a reference, we can just bubble the error up so we get a |
| // constant at reference type, making it easy to let the fallback call |
| // `PartialEq::eq` on it. |
| return Err(FallbackToConstRef); |
| } |
| ty::FnDef(..) => { |
| self.saw_const_match_error.set(true); |
| tcx.sess.emit_err(InvalidPattern { span, non_sm_ty: ty }); |
| PatKind::Wild |
| } |
| ty::Adt(adt_def, _) if !self.type_marked_structural(ty) => { |
| debug!("adt_def {:?} has !type_marked_structural for cv.ty: {:?}", adt_def, ty,); |
| self.saw_const_match_error.set(true); |
| let err = TypeNotStructural { span, non_sm_ty: ty }; |
| tcx.sess.emit_err(err); |
| PatKind::Wild |
| } |
| ty::Adt(adt_def, args) if adt_def.is_enum() => { |
| let (&variant_index, fields) = cv.unwrap_branch().split_first().unwrap(); |
| let variant_index = |
| VariantIdx::from_u32(variant_index.unwrap_leaf().try_to_u32().ok().unwrap()); |
| PatKind::Variant { |
| adt_def: *adt_def, |
| args, |
| variant_index, |
| subpatterns: self.field_pats( |
| fields.iter().copied().zip( |
| adt_def.variants()[variant_index] |
| .fields |
| .iter() |
| .map(|field| field.ty(self.tcx(), args)), |
| ), |
| )?, |
| } |
| } |
| ty::Tuple(fields) => PatKind::Leaf { |
| subpatterns: self |
| .field_pats(cv.unwrap_branch().iter().copied().zip(fields.iter()))?, |
| }, |
| ty::Adt(def, args) => PatKind::Leaf { |
| subpatterns: self.field_pats(cv.unwrap_branch().iter().copied().zip( |
| def.non_enum_variant().fields.iter().map(|field| field.ty(self.tcx(), args)), |
| ))?, |
| }, |
| ty::Slice(elem_ty) => PatKind::Slice { |
| prefix: cv |
| .unwrap_branch() |
| .iter() |
| .map(|val| self.recur(*val, *elem_ty, false)) |
| .collect::<Result<_, _>>()?, |
| slice: None, |
| suffix: Box::new([]), |
| }, |
| ty::Array(elem_ty, _) => PatKind::Array { |
| prefix: cv |
| .unwrap_branch() |
| .iter() |
| .map(|val| self.recur(*val, *elem_ty, false)) |
| .collect::<Result<_, _>>()?, |
| slice: None, |
| suffix: Box::new([]), |
| }, |
| ty::Ref(_, pointee_ty, ..) => match *pointee_ty.kind() { |
| // `&str` is represented as a valtree, let's keep using this |
| // optimization for now. |
| ty::Str => PatKind::Constant { |
| value: mir::ConstantKind::Ty(ty::Const::new_value(tcx, cv, ty)), |
| }, |
| // Backwards compatibility hack: support references to non-structural types, |
| // but hard error if we aren't behind a double reference. We could just use |
| // the fallback code path below, but that would allow *more* of this fishy |
| // code to compile, as then it only goes through the future incompat lint |
| // instead of a hard error. |
| ty::Adt(_, _) if !self.type_marked_structural(*pointee_ty) => { |
| if self.behind_reference.get() { |
| if !self.saw_const_match_error.get() && !self.saw_const_match_lint.get() { |
| self.saw_const_match_lint.set(true); |
| tcx.emit_spanned_lint( |
| lint::builtin::INDIRECT_STRUCTURAL_MATCH, |
| self.id, |
| span, |
| IndirectStructuralMatch { non_sm_ty: *pointee_ty }, |
| ); |
| } |
| return Err(FallbackToConstRef); |
| } else { |
| if !self.saw_const_match_error.get() { |
| self.saw_const_match_error.set(true); |
| let err = TypeNotStructural { span, non_sm_ty: *pointee_ty }; |
| tcx.sess.emit_err(err); |
| } |
| PatKind::Wild |
| } |
| } |
| // All other references are converted into deref patterns and then recursively |
| // convert the dereferenced constant to a pattern that is the sub-pattern of the |
| // deref pattern. |
| _ => { |
| if !pointee_ty.is_sized(tcx, param_env) && !pointee_ty.is_slice() { |
| let err = UnsizedPattern { span, non_sm_ty: *pointee_ty }; |
| tcx.sess.emit_err(err); |
| |
| // FIXME: introduce PatKind::Error to silence follow up diagnostics due to unreachable patterns. |
| PatKind::Wild |
| } else { |
| let old = self.behind_reference.replace(true); |
| // `b"foo"` produces a `&[u8; 3]`, but you can't use constants of array type when |
| // matching against references, you can only use byte string literals. |
| // The typechecker has a special case for byte string literals, by treating them |
| // as slices. This means we turn `&[T; N]` constants into slice patterns, which |
| // has no negative effects on pattern matching, even if we're actually matching on |
| // arrays. |
| let pointee_ty = match *pointee_ty.kind() { |
| ty::Array(elem_ty, _) if self.treat_byte_string_as_slice => { |
| Ty::new_slice(tcx, elem_ty) |
| } |
| _ => *pointee_ty, |
| }; |
| // References have the same valtree representation as their pointee. |
| let subpattern = self.recur(cv, pointee_ty, false)?; |
| self.behind_reference.set(old); |
| PatKind::Deref { subpattern } |
| } |
| } |
| }, |
| ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) => PatKind::Constant { |
| value: mir::ConstantKind::Ty(ty::Const::new_value(tcx, cv, ty)), |
| }, |
| ty::FnPtr(..) | ty::RawPtr(..) => unreachable!(), |
| _ => { |
| self.saw_const_match_error.set(true); |
| let err = InvalidPattern { span, non_sm_ty: ty }; |
| tcx.sess.emit_err(err); |
| PatKind::Wild |
| } |
| }; |
| |
| if !self.saw_const_match_error.get() |
| && !self.saw_const_match_lint.get() |
| && mir_structural_match_violation |
| // FIXME(#73448): Find a way to bring const qualification into parity with |
| // `search_for_structural_match_violation` and then remove this condition. |
| |
| // Obtain the actual type that isn't annotated. If we just looked at `cv.ty` we |
| // could get `Option<NonStructEq>`, even though `Option` is annotated with derive. |
| && let Some(non_sm_ty) = traits::search_for_structural_match_violation(span, tcx, ty) |
| { |
| self.saw_const_match_lint.set(true); |
| tcx.emit_spanned_lint( |
| lint::builtin::NONTRIVIAL_STRUCTURAL_MATCH, |
| id, |
| span, |
| NontrivialStructuralMatch {non_sm_ty} |
| ); |
| } |
| |
| Ok(Box::new(Pat { span, ty, kind })) |
| } |
| } |
