+++ /dev/null
-//! A pass that qualifies constness of temporaries in constants,
-//! static initializers and functions and also drives promotion.
-//!
-//! The Qualif flags below can be used to also provide better
-//! diagnostics as to why a constant rvalue wasn't promoted.
-
-use rustc_index::bit_set::BitSet;
-use rustc_index::vec::IndexVec;
-use rustc_target::spec::abi::Abi;
-use rustc::hir;
-use rustc::hir::def_id::DefId;
-use rustc::traits::{self, TraitEngine};
-use rustc::ty::{self, TyCtxt, Ty, TypeFoldable};
-use rustc::ty::cast::CastTy;
-use rustc::ty::query::Providers;
-use rustc::mir::*;
-use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext, NonMutatingUseContext};
-use rustc::middle::lang_items;
-use rustc::session::config::nightly_options;
-use syntax::feature_gate::{emit_feature_err, GateIssue};
-use syntax::symbol::sym;
-use syntax_pos::{Span, DUMMY_SP};
-
-use std::borrow::Cow;
-use std::cell::Cell;
-use std::fmt;
-use std::ops::{Deref, Index, IndexMut};
-use std::usize;
-
-use rustc::hir::HirId;
-use crate::transform::{MirPass, MirSource};
-use crate::transform::check_consts::ops::{self, NonConstOp};
-
-use rustc_error_codes::*;
-
-/// What kind of item we are in.
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-enum Mode {
- /// A `static` item.
- Static,
- /// A `static mut` item.
- StaticMut,
- /// A `const fn` item.
- ConstFn,
- /// A `const` item or an anonymous constant (e.g. in array lengths).
- Const,
- /// Other type of `fn`.
- NonConstFn,
-}
-
-impl Mode {
- /// Determine whether we have to do full const-checking because syntactically, we
- /// are required to be "const".
- #[inline]
- fn requires_const_checking(self) -> bool {
- self != Mode::NonConstFn
- }
-}
-
-impl fmt::Display for Mode {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- match *self {
- Mode::Const => write!(f, "constant"),
- Mode::Static | Mode::StaticMut => write!(f, "static"),
- Mode::ConstFn => write!(f, "constant function"),
- Mode::NonConstFn => write!(f, "function")
- }
- }
-}
-
-const QUALIF_COUNT: usize = 2;
-
-// FIXME(eddyb) once we can use const generics, replace this array with
-// something like `IndexVec` but for fixed-size arrays (`IndexArray`?).
-#[derive(Copy, Clone, Default)]
-struct PerQualif<T>([T; QUALIF_COUNT]);
-
-impl<T: Clone> PerQualif<T> {
- fn new(x: T) -> Self {
- PerQualif([x.clone(), x])
- }
-}
-
-impl<T> PerQualif<T> {
- fn as_mut(&mut self) -> PerQualif<&mut T> {
- let [x0, x1] = &mut self.0;
- PerQualif([x0, x1])
- }
-
- fn zip<U>(self, other: PerQualif<U>) -> PerQualif<(T, U)> {
- let [x0, x1] = self.0;
- let [y0, y1] = other.0;
- PerQualif([(x0, y0), (x1, y1)])
- }
-}
-
-impl PerQualif<bool> {
- fn encode_to_bits(self) -> u8 {
- self.0.iter().enumerate().fold(0, |bits, (i, &qualif)| {
- bits | ((qualif as u8) << i)
- })
- }
-
- fn decode_from_bits(bits: u8) -> Self {
- let mut qualifs = Self::default();
- for (i, qualif) in qualifs.0.iter_mut().enumerate() {
- *qualif = (bits & (1 << i)) != 0;
- }
- qualifs
- }
-}
-
-impl<Q: Qualif, T> Index<Q> for PerQualif<T> {
- type Output = T;
-
- fn index(&self, _: Q) -> &T {
- &self.0[Q::IDX]
- }
-}
-
-impl<Q: Qualif, T> IndexMut<Q> for PerQualif<T> {
- fn index_mut(&mut self, _: Q) -> &mut T {
- &mut self.0[Q::IDX]
- }
-}
-
-struct ConstCx<'a, 'tcx> {
- tcx: TyCtxt<'tcx>,
- param_env: ty::ParamEnv<'tcx>,
- mode: Mode,
- body: &'a Body<'tcx>,
-
- per_local: PerQualif<BitSet<Local>>,
-}
-
-impl<'a, 'tcx> ConstCx<'a, 'tcx> {
- fn is_const_panic_fn(&self, def_id: DefId) -> bool {
- Some(def_id) == self.tcx.lang_items().panic_fn() ||
- Some(def_id) == self.tcx.lang_items().begin_panic_fn()
- }
-}
-
-#[derive(Copy, Clone, Debug)]
-enum ValueSource<'a, 'tcx> {
- Rvalue(&'a Rvalue<'tcx>),
- DropAndReplace(&'a Operand<'tcx>),
- Call {
- callee: &'a Operand<'tcx>,
- args: &'a [Operand<'tcx>],
- return_ty: Ty<'tcx>,
- },
-}
-
-/// A "qualif"(-ication) is a way to look for something "bad" in the MIR that would disqualify some
-/// code for promotion or prevent it from evaluating at compile time. So `return true` means
-/// "I found something bad, no reason to go on searching". `false` is only returned if we
-/// definitely cannot find anything bad anywhere.
-///
-/// The default implementations proceed structurally.
-trait Qualif {
- const IDX: usize;
-
- /// Return the qualification that is (conservatively) correct for any value
- /// of the type, or `None` if the qualification is not value/type-based.
- fn in_any_value_of_ty(_cx: &ConstCx<'_, 'tcx>, _ty: Ty<'tcx>) -> Option<bool> {
- None
- }
-
- /// Return a mask for the qualification, given a type. This is `false` iff
- /// no value of that type can have the qualification.
- fn mask_for_ty(cx: &ConstCx<'_, 'tcx>, ty: Ty<'tcx>) -> bool {
- Self::in_any_value_of_ty(cx, ty).unwrap_or(true)
- }
-
- fn in_local(cx: &ConstCx<'_, '_>, local: Local) -> bool {
- cx.per_local.0[Self::IDX].contains(local)
- }
-
- fn in_static(_cx: &ConstCx<'_, 'tcx>, _static: &Static<'tcx>) -> bool {
- // FIXME(eddyb) should we do anything here for value properties?
- false
- }
-
- fn in_projection_structurally(
- cx: &ConstCx<'_, 'tcx>,
- place: PlaceRef<'_, 'tcx>,
- ) -> bool {
- if let [proj_base @ .., elem] = place.projection {
- let base_qualif = Self::in_place(cx, PlaceRef {
- base: place.base,
- projection: proj_base,
- });
- let qualif = base_qualif && Self::mask_for_ty(
- cx,
- Place::ty_from(place.base, proj_base, cx.body, cx.tcx)
- .projection_ty(cx.tcx, elem)
- .ty,
- );
- match elem {
- ProjectionElem::Deref |
- ProjectionElem::Subslice { .. } |
- ProjectionElem::Field(..) |
- ProjectionElem::ConstantIndex { .. } |
- ProjectionElem::Downcast(..) => qualif,
-
- // FIXME(eddyb) shouldn't this be masked *after* including the
- // index local? Then again, it's `usize` which is neither
- // `HasMutInterior` nor `NeedsDrop`.
- ProjectionElem::Index(local) => qualif || Self::in_local(cx, *local),
- }
- } else {
- bug!("This should be called if projection is not empty");
- }
- }
-
- fn in_projection(
- cx: &ConstCx<'_, 'tcx>,
- place: PlaceRef<'_, 'tcx>,
- ) -> bool {
- Self::in_projection_structurally(cx, place)
- }
-
- fn in_place(cx: &ConstCx<'_, 'tcx>, place: PlaceRef<'_, 'tcx>) -> bool {
- match place {
- PlaceRef {
- base: PlaceBase::Local(local),
- projection: [],
- } => Self::in_local(cx, *local),
- PlaceRef {
- base: PlaceBase::Static(box Static {
- kind: StaticKind::Promoted(..),
- ..
- }),
- projection: [],
- } => bug!("qualifying already promoted MIR"),
- PlaceRef {
- base: PlaceBase::Static(static_),
- projection: [],
- } => {
- Self::in_static(cx, static_)
- },
- PlaceRef {
- base: _,
- projection: [.., _],
- } => Self::in_projection(cx, place),
- }
- }
-
- fn in_operand(cx: &ConstCx<'_, 'tcx>, operand: &Operand<'tcx>) -> bool {
- match *operand {
- Operand::Copy(ref place) |
- Operand::Move(ref place) => Self::in_place(cx, place.as_ref()),
-
- Operand::Constant(ref constant) => {
- if let ty::ConstKind::Unevaluated(def_id, _) = constant.literal.val {
- // Don't peek inside trait associated constants.
- if cx.tcx.trait_of_item(def_id).is_some() {
- Self::in_any_value_of_ty(cx, constant.literal.ty).unwrap_or(false)
- } else {
- let bits = cx.tcx.at(constant.span).mir_const_qualif(def_id);
-
- let qualif = PerQualif::decode_from_bits(bits).0[Self::IDX];
-
- // Just in case the type is more specific than
- // the definition, e.g., impl associated const
- // with type parameters, take it into account.
- qualif && Self::mask_for_ty(cx, constant.literal.ty)
- }
- } else {
- false
- }
- }
- }
- }
-
- fn in_rvalue_structurally(cx: &ConstCx<'_, 'tcx>, rvalue: &Rvalue<'tcx>) -> bool {
- match *rvalue {
- Rvalue::NullaryOp(..) => false,
-
- Rvalue::Discriminant(ref place) |
- Rvalue::Len(ref place) => Self::in_place(cx, place.as_ref()),
-
- Rvalue::Use(ref operand) |
- Rvalue::Repeat(ref operand, _) |
- Rvalue::UnaryOp(_, ref operand) |
- Rvalue::Cast(_, ref operand, _) => Self::in_operand(cx, operand),
-
- Rvalue::BinaryOp(_, ref lhs, ref rhs) |
- Rvalue::CheckedBinaryOp(_, ref lhs, ref rhs) => {
- Self::in_operand(cx, lhs) || Self::in_operand(cx, rhs)
- }
-
- Rvalue::Ref(_, _, ref place) => {
- // Special-case reborrows to be more like a copy of the reference.
- if let &[ref proj_base @ .., elem] = place.projection.as_ref() {
- if ProjectionElem::Deref == elem {
- let base_ty = Place::ty_from(&place.base, proj_base, cx.body, cx.tcx).ty;
- if let ty::Ref(..) = base_ty.kind {
- return Self::in_place(cx, PlaceRef {
- base: &place.base,
- projection: proj_base,
- });
- }
- }
- }
-
- Self::in_place(cx, place.as_ref())
- }
-
- Rvalue::Aggregate(_, ref operands) => {
- operands.iter().any(|o| Self::in_operand(cx, o))
- }
- }
- }
-
- fn in_rvalue(cx: &ConstCx<'_, 'tcx>, rvalue: &Rvalue<'tcx>) -> bool {
- Self::in_rvalue_structurally(cx, rvalue)
- }
-
- fn in_call(
- cx: &ConstCx<'_, 'tcx>,
- _callee: &Operand<'tcx>,
- _args: &[Operand<'tcx>],
- return_ty: Ty<'tcx>,
- ) -> bool {
- // Be conservative about the returned value of a const fn.
- Self::in_any_value_of_ty(cx, return_ty).unwrap_or(false)
- }
-
- fn in_value(cx: &ConstCx<'_, 'tcx>, source: ValueSource<'_, 'tcx>) -> bool {
- match source {
- ValueSource::Rvalue(rvalue) => Self::in_rvalue(cx, rvalue),
- ValueSource::DropAndReplace(source) => Self::in_operand(cx, source),
- ValueSource::Call { callee, args, return_ty } => {
- Self::in_call(cx, callee, args, return_ty)
- }
- }
- }
-}
-
-/// Constant containing interior mutability (`UnsafeCell<T>`).
-/// This must be ruled out to make sure that evaluating the constant at compile-time
-/// and at *any point* during the run-time would produce the same result. In particular,
-/// promotion of temporaries must not change program behavior; if the promoted could be
-/// written to, that would be a problem.
-struct HasMutInterior;
-
-impl Qualif for HasMutInterior {
- const IDX: usize = 0;
-
- fn in_any_value_of_ty(cx: &ConstCx<'_, 'tcx>, ty: Ty<'tcx>) -> Option<bool> {
- Some(!ty.is_freeze(cx.tcx, cx.param_env, DUMMY_SP))
- }
-
- fn in_rvalue(cx: &ConstCx<'_, 'tcx>, rvalue: &Rvalue<'tcx>) -> bool {
- match *rvalue {
- // Returning `true` for `Rvalue::Ref` indicates the borrow isn't
- // allowed in constants (and the `Checker` will error), and/or it
- // won't be promoted, due to `&mut ...` or interior mutability.
- Rvalue::Ref(_, kind, ref place) => {
- let ty = place.ty(cx.body, cx.tcx).ty;
-
- if let BorrowKind::Mut { .. } = kind {
- // In theory, any zero-sized value could be borrowed
- // mutably without consequences. However, only &mut []
- // is allowed right now, and only in functions.
- if cx.mode == Mode::StaticMut {
- // Inside a `static mut`, &mut [...] is also allowed.
- match ty.kind {
- ty::Array(..) | ty::Slice(_) => {}
- _ => return true,
- }
- } else if let ty::Array(_, len) = ty.kind {
- // FIXME(eddyb) the `cx.mode == Mode::NonConstFn` condition
- // seems unnecessary, given that this is merely a ZST.
- match len.try_eval_usize(cx.tcx, cx.param_env) {
- Some(0) if cx.mode == Mode::NonConstFn => {},
- _ => return true,
- }
- } else {
- return true;
- }
- }
- }
-
- Rvalue::Aggregate(ref kind, _) => {
- if let AggregateKind::Adt(def, ..) = **kind {
- if Some(def.did) == cx.tcx.lang_items().unsafe_cell_type() {
- let ty = rvalue.ty(cx.body, cx.tcx);
- assert_eq!(Self::in_any_value_of_ty(cx, ty), Some(true));
- return true;
- }
- }
- }
-
- _ => {}
- }
-
- Self::in_rvalue_structurally(cx, rvalue)
- }
-}
-
-/// Constant containing an ADT that implements `Drop`.
-/// This must be ruled out (a) because we cannot run `Drop` during compile-time
-/// as that might not be a `const fn`, and (b) because implicit promotion would
-/// remove side-effects that occur as part of dropping that value.
-struct NeedsDrop;
-
-impl Qualif for NeedsDrop {
- const IDX: usize = 1;
-
- fn in_any_value_of_ty(cx: &ConstCx<'_, 'tcx>, ty: Ty<'tcx>) -> Option<bool> {
- Some(ty.needs_drop(cx.tcx, cx.param_env))
- }
-
- fn in_rvalue(cx: &ConstCx<'_, 'tcx>, rvalue: &Rvalue<'tcx>) -> bool {
- if let Rvalue::Aggregate(ref kind, _) = *rvalue {
- if let AggregateKind::Adt(def, ..) = **kind {
- if def.has_dtor(cx.tcx) {
- return true;
- }
- }
- }
-
- Self::in_rvalue_structurally(cx, rvalue)
- }
-}
-
-// Ensure the `IDX` values are sequential (`0..QUALIF_COUNT`).
-macro_rules! static_assert_seq_qualifs {
- ($i:expr => $first:ident $(, $rest:ident)*) => {
- static_assert!({
- static_assert_seq_qualifs!($i + 1 => $($rest),*);
-
- $first::IDX == $i
- });
- };
- ($i:expr =>) => {
- static_assert!(QUALIF_COUNT == $i);
- };
-}
-static_assert_seq_qualifs!(
- 0 => HasMutInterior, NeedsDrop
-);
-
-impl ConstCx<'_, 'tcx> {
- fn qualifs_in_any_value_of_ty(&self, ty: Ty<'tcx>) -> PerQualif<bool> {
- let mut qualifs = PerQualif::default();
- qualifs[HasMutInterior] = HasMutInterior::in_any_value_of_ty(self, ty).unwrap_or(false);
- qualifs[NeedsDrop] = NeedsDrop::in_any_value_of_ty(self, ty).unwrap_or(false);
- qualifs
- }
-
- fn qualifs_in_local(&self, local: Local) -> PerQualif<bool> {
- let mut qualifs = PerQualif::default();
- qualifs[HasMutInterior] = HasMutInterior::in_local(self, local);
- qualifs[NeedsDrop] = NeedsDrop::in_local(self, local);
- qualifs
- }
-
- fn qualifs_in_value(&self, source: ValueSource<'_, 'tcx>) -> PerQualif<bool> {
- let mut qualifs = PerQualif::default();
- qualifs[HasMutInterior] = HasMutInterior::in_value(self, source);
- qualifs[NeedsDrop] = NeedsDrop::in_value(self, source);
- qualifs
- }
-}
-
-/// Checks MIR for being admissible as a compile-time constant, using `ConstCx`
-/// for value qualifications, and accumulates writes of
-/// rvalue/call results to locals, in `local_qualif`.
-/// It also records candidates for promotion in `promotion_candidates`,
-/// both in functions and const/static items.
-struct Checker<'a, 'tcx> {
- cx: ConstCx<'a, 'tcx>,
-
- span: Span,
- def_id: DefId,
-
- /// If `true`, do not emit errors to the user, merely collect them in `errors`.
- suppress_errors: bool,
- errors: Vec<(Span, String)>,
-}
-
-macro_rules! unleash_miri {
- ($this:expr) => {{
- if $this.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
- if $this.mode.requires_const_checking() && !$this.suppress_errors {
- $this.tcx.sess.span_warn($this.span, "skipping const checks");
- }
- return;
- }
- }}
-}
-
-impl Deref for Checker<'a, 'tcx> {
- type Target = ConstCx<'a, 'tcx>;
-
- fn deref(&self) -> &Self::Target {
- &self.cx
- }
-}
-
-impl<'a, 'tcx> Checker<'a, 'tcx> {
- fn new(tcx: TyCtxt<'tcx>, def_id: DefId, body: &'a Body<'tcx>, mode: Mode) -> Self {
- assert!(def_id.is_local());
-
- let param_env = tcx.param_env(def_id);
-
- let mut cx = ConstCx {
- tcx,
- param_env,
- mode,
- body,
- per_local: PerQualif::new(BitSet::new_empty(body.local_decls.len())),
- };
-
- for (local, decl) in body.local_decls.iter_enumerated() {
- if let LocalKind::Arg = body.local_kind(local) {
- let qualifs = cx.qualifs_in_any_value_of_ty(decl.ty);
- for (per_local, qualif) in &mut cx.per_local.as_mut().zip(qualifs).0 {
- if *qualif {
- per_local.insert(local);
- }
- }
- }
- }
-
- Checker {
- cx,
- span: body.span,
- def_id,
- errors: vec![],
- suppress_errors: false,
- }
- }
-
- // FIXME(eddyb) we could split the errors into meaningful
- // categories, but enabling full miri would make that
- // slightly pointless (even with feature-gating).
- fn not_const(&mut self, op: impl NonConstOp) {
- unleash_miri!(self);
- if self.mode.requires_const_checking() && !self.suppress_errors {
- self.record_error(op);
- let mut err = struct_span_err!(
- self.tcx.sess,
- self.span,
- E0019,
- "{} contains unimplemented expression type",
- self.mode
- );
- if self.tcx.sess.teach(&err.get_code().unwrap()) {
- err.note("A function call isn't allowed in the const's initialization expression \
- because the expression's value must be known at compile-time.");
- err.note("Remember: you can't use a function call inside a const's initialization \
- expression! However, you can use it anywhere else.");
- }
- err.emit();
- }
- }
-
- fn record_error(&mut self, op: impl NonConstOp) {
- self.record_error_spanned(op, self.span);
- }
-
- fn record_error_spanned(&mut self, op: impl NonConstOp, span: Span) {
- self.errors.push((span, format!("{:?}", op)));
- }
-
- /// Assigns an rvalue/call qualification to the given destination.
- fn assign(&mut self, dest: &Place<'tcx>, source: ValueSource<'_, 'tcx>, location: Location) {
- trace!("assign: {:?} <- {:?}", dest, source);
-
- let mut qualifs = self.qualifs_in_value(source);
-
- match source {
- ValueSource::Rvalue(&Rvalue::Ref(_, kind, _)) => {
- // Getting `true` from `HasMutInterior::in_rvalue` means
- // the borrowed place is disallowed from being borrowed,
- // due to either a mutable borrow (with some exceptions),
- // or an shared borrow of a value with interior mutability.
- // Then `HasMutInterior` is cleared
- // to avoid duplicate errors (e.g. from reborrowing).
- if qualifs[HasMutInterior] {
- qualifs[HasMutInterior] = false;
-
- debug!("suppress_errors: {}", self.suppress_errors);
- if self.mode.requires_const_checking() && !self.suppress_errors {
- if !self.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
- self.record_error(ops::MutBorrow(kind));
- if let BorrowKind::Mut { .. } = kind {
- let mut err = struct_span_err!(self.tcx.sess, self.span, E0017,
- "references in {}s may only refer \
- to immutable values", self.mode);
- err.span_label(self.span, format!("{}s require immutable values",
- self.mode));
- if self.tcx.sess.teach(&err.get_code().unwrap()) {
- err.note("References in statics and constants may only refer \
- to immutable values.\n\n\
- Statics are shared everywhere, and if they refer to \
- mutable data one might violate memory safety since \
- holding multiple mutable references to shared data \
- is not allowed.\n\n\
- If you really want global mutable state, try using \
- static mut or a global UnsafeCell.");
- }
- err.emit();
- } else {
- span_err!(self.tcx.sess, self.span, E0492,
- "cannot borrow a constant which may contain \
- interior mutability, create a static instead");
- }
- }
- }
- }
- },
- _ => {},
- }
-
- let mut dest_projection = &dest.projection[..];
- let index = loop {
- match (&dest.base, dest_projection) {
- // We treat all locals equal in constants
- (&PlaceBase::Local(index), []) => break index,
- // projections are transparent for assignments
- // we qualify the entire destination at once, even if just a field would have
- // stricter qualification
- (base, [proj_base @ .., _]) => {
- // Catch more errors in the destination. `visit_place` also checks various
- // projection rules like union field access and raw pointer deref
- let context = PlaceContext::MutatingUse(MutatingUseContext::Store);
- self.visit_place_base(base, context, location);
- self.visit_projection(base, dest_projection, context, location);
- dest_projection = proj_base;
- },
- (&PlaceBase::Static(box Static {
- kind: StaticKind::Promoted(..),
- ..
- }), []) => bug!("promoteds don't exist yet during promotion"),
- (&PlaceBase::Static(box Static{ kind: _, .. }), []) => {
- // Catch more errors in the destination. `visit_place` also checks that we
- // do not try to access statics from constants or try to mutate statics
- let context = PlaceContext::MutatingUse(MutatingUseContext::Store);
- self.visit_place_base(&dest.base, context, location);
- return;
- }
- }
- };
-
- let kind = self.body.local_kind(index);
- debug!("store to {:?} {:?}", kind, index);
-
- // this is overly restrictive, because even full assignments do not clear the qualif
- // While we could special case full assignments, this would be inconsistent with
- // aggregates where we overwrite all fields via assignments, which would not get
- // that feature.
- for (per_local, qualif) in &mut self.cx.per_local.as_mut().zip(qualifs).0 {
- if *qualif {
- per_local.insert(index);
- }
- }
- }
-
- /// Check a whole const, static initializer or const fn.
- fn check_const(&mut self) -> u8 {
- use crate::transform::check_consts as new_checker;
-
- debug!("const-checking {} {:?}", self.mode, self.def_id);
-
- // FIXME: Also use the new validator when features that require it (e.g. `const_if`) are
- // enabled.
- let use_new_validator = self.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you;
- if use_new_validator {
- debug!("Using dataflow-based const validator");
- }
-
- let item = new_checker::Item::new(self.tcx, self.def_id, self.body);
- let mut validator = new_checker::validation::Validator::new(&item);
-
- validator.suppress_errors = !use_new_validator;
- self.suppress_errors = use_new_validator;
-
- let body = self.body;
-
- let mut seen_blocks = BitSet::new_empty(body.basic_blocks().len());
- let mut bb = START_BLOCK;
- loop {
- seen_blocks.insert(bb.index());
-
- self.visit_basic_block_data(bb, &body[bb]);
- validator.visit_basic_block_data(bb, &body[bb]);
-
- let target = match body[bb].terminator().kind {
- TerminatorKind::Goto { target } |
- TerminatorKind::FalseUnwind { real_target: target, .. } |
- TerminatorKind::Drop { target, .. } |
- TerminatorKind::DropAndReplace { target, .. } |
- TerminatorKind::Assert { target, .. } |
- TerminatorKind::Call { destination: Some((_, target)), .. } => {
- Some(target)
- }
-
- // Non-terminating calls cannot produce any value.
- TerminatorKind::Call { destination: None, .. } => {
- break;
- }
-
- TerminatorKind::SwitchInt {..} |
- TerminatorKind::Resume |
- TerminatorKind::Abort |
- TerminatorKind::GeneratorDrop |
- TerminatorKind::Yield { .. } |
- TerminatorKind::Unreachable |
- TerminatorKind::FalseEdges { .. } => None,
-
- TerminatorKind::Return => {
- break;
- }
- };
-
- match target {
- // No loops allowed.
- Some(target) if !seen_blocks.contains(target.index()) => {
- bb = target;
- }
- _ => {
- if !self.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
- self.tcx.sess.delay_span_bug(
- self.span,
- "complex control flow is forbidden in a const context",
- );
- }
- break;
- }
- }
- }
-
- // The new validation pass should agree with the old when running on simple const bodies
- // (e.g. no `if` or `loop`).
- if !use_new_validator {
- let mut new_errors = validator.take_errors();
-
- // FIXME: each checker sometimes emits the same error with the same span twice in a row.
- self.errors.dedup();
- new_errors.dedup();
-
- if self.errors != new_errors {
- validator_mismatch(
- self.tcx,
- body,
- std::mem::replace(&mut self.errors, vec![]),
- new_errors,
- );
- }
- }
-
- self.qualifs_in_local(RETURN_PLACE).encode_to_bits()
- }
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
- fn visit_place_base(
- &mut self,
- place_base: &PlaceBase<'tcx>,
- context: PlaceContext,
- location: Location,
- ) {
- self.super_place_base(place_base, context, location);
- match place_base {
- PlaceBase::Local(_) => {}
- PlaceBase::Static(box Static{ kind: StaticKind::Promoted(_, _), .. }) => {
- unreachable!()
- }
- PlaceBase::Static(box Static{ kind: StaticKind::Static, def_id, .. }) => {
- if self.tcx
- .get_attrs(*def_id)
- .iter()
- .any(|attr| attr.check_name(sym::thread_local)) {
- if self.mode.requires_const_checking() && !self.suppress_errors {
- self.record_error(ops::ThreadLocalAccess);
- span_err!(self.tcx.sess, self.span, E0625,
- "thread-local statics cannot be \
- accessed at compile-time");
- }
- return;
- }
-
- // Only allow statics (not consts) to refer to other statics.
- if self.mode == Mode::Static || self.mode == Mode::StaticMut {
- return;
- }
- unleash_miri!(self);
-
- if self.mode.requires_const_checking() && !self.suppress_errors {
- self.record_error(ops::StaticAccess);
- let mut err = struct_span_err!(self.tcx.sess, self.span, E0013,
- "{}s cannot refer to statics, use \
- a constant instead", self.mode);
- if self.tcx.sess.teach(&err.get_code().unwrap()) {
- err.note(
- "Static and const variables can refer to other const variables. \
- But a const variable cannot refer to a static variable."
- );
- err.help(
- "To fix this, the value can be extracted as a const and then used."
- );
- }
- err.emit()
- }
- }
- }
- }
-
- fn visit_projection_elem(
- &mut self,
- place_base: &PlaceBase<'tcx>,
- proj_base: &[PlaceElem<'tcx>],
- elem: &PlaceElem<'tcx>,
- context: PlaceContext,
- location: Location,
- ) {
- debug!(
- "visit_projection_elem: place_base={:?} proj_base={:?} elem={:?} \
- context={:?} location={:?}",
- place_base,
- proj_base,
- elem,
- context,
- location,
- );
-
- self.super_projection_elem(place_base, proj_base, elem, context, location);
-
- match elem {
- ProjectionElem::Deref => {
- if context.is_mutating_use() {
- // `not_const` errors out in const contexts
- self.not_const(ops::MutDeref)
- }
- let base_ty = Place::ty_from(place_base, proj_base, self.body, self.tcx).ty;
- match self.mode {
- Mode::NonConstFn => {}
- _ if self.suppress_errors => {}
- _ => {
- if let ty::RawPtr(_) = base_ty.kind {
- if !self.tcx.features().const_raw_ptr_deref {
- self.record_error(ops::RawPtrDeref);
- emit_feature_err(
- &self.tcx.sess.parse_sess, sym::const_raw_ptr_deref,
- self.span, GateIssue::Language,
- &format!(
- "dereferencing raw pointers in {}s is unstable",
- self.mode,
- ),
- );
- }
- }
- }
- }
- }
-
- ProjectionElem::ConstantIndex {..} |
- ProjectionElem::Subslice {..} |
- ProjectionElem::Field(..) |
- ProjectionElem::Index(_) => {
- let base_ty = Place::ty_from(place_base, proj_base, self.body, self.tcx).ty;
- if let Some(def) = base_ty.ty_adt_def() {
- if def.is_union() {
- match self.mode {
- Mode::ConstFn => {
- if !self.tcx.features().const_fn_union
- && !self.suppress_errors
- {
- self.record_error(ops::UnionAccess);
- emit_feature_err(
- &self.tcx.sess.parse_sess, sym::const_fn_union,
- self.span, GateIssue::Language,
- "unions in const fn are unstable",
- );
- }
- },
-
- | Mode::NonConstFn
- | Mode::Static
- | Mode::StaticMut
- | Mode::Const
- => {},
- }
- }
- }
- }
-
- ProjectionElem::Downcast(..) => {
- self.not_const(ops::Downcast)
- }
- }
- }
-
- fn visit_operand(&mut self, operand: &Operand<'tcx>, location: Location) {
- debug!("visit_operand: operand={:?} location={:?}", operand, location);
- self.super_operand(operand, location);
-
- match *operand {
- Operand::Move(ref place) => {
- // Mark the consumed locals to indicate later drops are noops.
- if let Some(local) = place.as_local() {
- self.cx.per_local[NeedsDrop].remove(local);
- }
- }
- Operand::Copy(_) |
- Operand::Constant(_) => {}
- }
- }
-
- fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
- debug!("visit_rvalue: rvalue={:?} location={:?}", rvalue, location);
-
- // Check nested operands and places.
- if let Rvalue::Ref(_, kind, ref place) = *rvalue {
- // Special-case reborrows.
- let mut reborrow_place = None;
- if let &[ref proj_base @ .., elem] = place.projection.as_ref() {
- if elem == ProjectionElem::Deref {
- let base_ty = Place::ty_from(&place.base, proj_base, self.body, self.tcx).ty;
- if let ty::Ref(..) = base_ty.kind {
- reborrow_place = Some(proj_base);
- }
- }
- }
-
- if let Some(proj) = reborrow_place {
- let ctx = match kind {
- BorrowKind::Shared => PlaceContext::NonMutatingUse(
- NonMutatingUseContext::SharedBorrow,
- ),
- BorrowKind::Shallow => PlaceContext::NonMutatingUse(
- NonMutatingUseContext::ShallowBorrow,
- ),
- BorrowKind::Unique => PlaceContext::NonMutatingUse(
- NonMutatingUseContext::UniqueBorrow,
- ),
- BorrowKind::Mut { .. } => PlaceContext::MutatingUse(
- MutatingUseContext::Borrow,
- ),
- };
- self.visit_place_base(&place.base, ctx, location);
- self.visit_projection(&place.base, proj, ctx, location);
- } else {
- self.super_rvalue(rvalue, location);
- }
- } else {
- self.super_rvalue(rvalue, location);
- }
-
- match *rvalue {
- Rvalue::Use(_) |
- Rvalue::Repeat(..) |
- Rvalue::UnaryOp(UnOp::Neg, _) |
- Rvalue::UnaryOp(UnOp::Not, _) |
- Rvalue::NullaryOp(NullOp::SizeOf, _) |
- Rvalue::CheckedBinaryOp(..) |
- Rvalue::Cast(CastKind::Pointer(_), ..) |
- Rvalue::Discriminant(..) |
- Rvalue::Len(_) |
- Rvalue::Ref(..) |
- Rvalue::Aggregate(..) => {}
-
- Rvalue::Cast(CastKind::Misc, ref operand, cast_ty) => {
- let operand_ty = operand.ty(self.body, self.tcx);
- let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast");
- let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
- match (cast_in, cast_out) {
- (CastTy::Ptr(_), CastTy::Int(_)) |
- (CastTy::FnPtr, CastTy::Int(_)) if self.mode != Mode::NonConstFn => {
- unleash_miri!(self);
- if !self.tcx.features().const_raw_ptr_to_usize_cast
- && !self.suppress_errors
- {
- // in const fn and constants require the feature gate
- // FIXME: make it unsafe inside const fn and constants
- self.record_error(ops::RawPtrToIntCast);
- emit_feature_err(
- &self.tcx.sess.parse_sess, sym::const_raw_ptr_to_usize_cast,
- self.span, GateIssue::Language,
- &format!(
- "casting pointers to integers in {}s is unstable",
- self.mode,
- ),
- );
- }
- }
- _ => {}
- }
- }
-
- Rvalue::BinaryOp(op, ref lhs, _) => {
- if let ty::RawPtr(_) | ty::FnPtr(..) = lhs.ty(self.body, self.tcx).kind {
- assert!(op == BinOp::Eq || op == BinOp::Ne ||
- op == BinOp::Le || op == BinOp::Lt ||
- op == BinOp::Ge || op == BinOp::Gt ||
- op == BinOp::Offset);
-
- unleash_miri!(self);
- if self.mode.requires_const_checking() &&
- !self.tcx.features().const_compare_raw_pointers &&
- !self.suppress_errors
- {
- self.record_error(ops::RawPtrComparison);
- // require the feature gate inside constants and const fn
- // FIXME: make it unsafe to use these operations
- emit_feature_err(
- &self.tcx.sess.parse_sess,
- sym::const_compare_raw_pointers,
- self.span,
- GateIssue::Language,
- &format!("comparing raw pointers inside {}", self.mode),
- );
- }
- }
- }
-
- Rvalue::NullaryOp(NullOp::Box, _) => {
- unleash_miri!(self);
- if self.mode.requires_const_checking() && !self.suppress_errors {
- self.record_error(ops::HeapAllocation);
- let mut err = struct_span_err!(self.tcx.sess, self.span, E0010,
- "allocations are not allowed in {}s", self.mode);
- err.span_label(self.span, format!("allocation not allowed in {}s", self.mode));
- if self.tcx.sess.teach(&err.get_code().unwrap()) {
- err.note(
- "The value of statics and constants must be known at compile time, \
- and they live for the entire lifetime of a program. Creating a boxed \
- value allocates memory on the heap at runtime, and therefore cannot \
- be done at compile time."
- );
- }
- err.emit();
- }
- }
- }
- }
-
- fn visit_terminator_kind(&mut self,
- kind: &TerminatorKind<'tcx>,
- location: Location) {
- debug!("visit_terminator_kind: kind={:?} location={:?}", kind, location);
- if let TerminatorKind::Call { ref func, ref args, ref destination, .. } = *kind {
- if let Some((ref dest, _)) = *destination {
- self.assign(dest, ValueSource::Call {
- callee: func,
- args,
- return_ty: dest.ty(self.body, self.tcx).ty,
- }, location);
- }
-
- let fn_ty = func.ty(self.body, self.tcx);
- match fn_ty.kind {
- ty::FnDef(def_id, _) => {
- match self.tcx.fn_sig(def_id).abi() {
- Abi::RustIntrinsic |
- Abi::PlatformIntrinsic => {
- assert!(!self.tcx.is_const_fn(def_id));
- match &*self.tcx.item_name(def_id).as_str() {
- // special intrinsic that can be called diretly without an intrinsic
- // feature gate needs a language feature gate
- "transmute" => {
- if self.mode.requires_const_checking()
- && !self.suppress_errors
- {
- // const eval transmute calls only with the feature gate
- if !self.tcx.features().const_transmute {
- self.record_error(ops::Transmute);
- emit_feature_err(
- &self.tcx.sess.parse_sess, sym::const_transmute,
- self.span, GateIssue::Language,
- &format!("The use of std::mem::transmute() \
- is gated in {}s", self.mode));
- }
- }
- }
-
- // no need to check feature gates, intrinsics are only callable
- // from the libstd or with forever unstable feature gates
- _ => {}
- }
- }
- _ => {
- // In normal functions no calls are feature-gated.
- if self.mode.requires_const_checking() {
- let unleash_miri = self
- .tcx
- .sess
- .opts
- .debugging_opts
- .unleash_the_miri_inside_of_you;
- if self.tcx.is_const_fn(def_id)
- || unleash_miri
- || self.suppress_errors
- {
- // stable const fns or unstable const fns
- // with their feature gate active
- // FIXME(eddyb) move stability checks from `is_const_fn` here.
- } else if self.is_const_panic_fn(def_id) {
- // Check the const_panic feature gate.
- // FIXME: cannot allow this inside `allow_internal_unstable`
- // because that would make `panic!` insta stable in constants,
- // since the macro is marked with the attribute.
- if !self.tcx.features().const_panic {
- // Don't allow panics in constants without the feature gate.
- self.record_error(ops::Panic);
- emit_feature_err(
- &self.tcx.sess.parse_sess,
- sym::const_panic,
- self.span,
- GateIssue::Language,
- &format!("panicking in {}s is unstable", self.mode),
- );
- }
- } else if let Some(feature)
- = self.tcx.is_unstable_const_fn(def_id) {
- // Check `#[unstable]` const fns or `#[rustc_const_unstable]`
- // functions without the feature gate active in this crate in
- // order to report a better error message than the one below.
- if !self.span.allows_unstable(feature) {
- self.record_error(ops::FnCallUnstable(def_id, feature));
- let mut err = self.tcx.sess.struct_span_err(self.span,
- &format!("`{}` is not yet stable as a const fn",
- self.tcx.def_path_str(def_id)));
- if nightly_options::is_nightly_build() {
- help!(&mut err,
- "add `#![feature({})]` to the \
- crate attributes to enable",
- feature);
- }
- err.emit();
- }
- } else {
- self.record_error(ops::FnCallNonConst(def_id));
- let mut err = struct_span_err!(
- self.tcx.sess,
- self.span,
- E0015,
- "calls in {}s are limited to constant functions, \
- tuple structs and tuple variants",
- self.mode,
- );
- err.emit();
- }
- }
- }
- }
- }
- ty::FnPtr(_) => {
- unleash_miri!(self);
- if self.mode.requires_const_checking() && !self.suppress_errors {
- self.record_error(ops::FnCallIndirect);
- let mut err = self.tcx.sess.struct_span_err(
- self.span,
- "function pointers are not allowed in const fn"
- );
- err.emit();
- }
- }
- _ => {
- self.not_const(ops::FnCallOther);
- }
- }
-
- // Check callee and argument operands.
- self.visit_operand(func, location);
- for arg in args {
- self.visit_operand(arg, location);
- }
- } else if let TerminatorKind::Drop {
- location: ref place, ..
- } | TerminatorKind::DropAndReplace {
- location: ref place, ..
- } = *kind {
- match *kind {
- TerminatorKind::DropAndReplace { .. } => {}
- _ => self.super_terminator_kind(kind, location),
- }
-
- // Deny *any* live drops anywhere other than functions.
- if self.mode.requires_const_checking() && !self.suppress_errors {
- unleash_miri!(self);
- // HACK(eddyb): emulate a bit of dataflow analysis,
- // conservatively, that drop elaboration will do.
- let needs_drop = if let Some(local) = place.as_local() {
- if NeedsDrop::in_local(self, local) {
- Some(self.body.local_decls[local].source_info.span)
- } else {
- None
- }
- } else {
- Some(self.span)
- };
-
- if let Some(span) = needs_drop {
- // Double-check the type being dropped, to minimize false positives.
- let ty = place.ty(self.body, self.tcx).ty;
- if ty.needs_drop(self.tcx, self.param_env) {
- self.record_error_spanned(ops::LiveDrop, span);
- struct_span_err!(self.tcx.sess, span, E0493,
- "destructors cannot be evaluated at compile-time")
- .span_label(span, format!("{}s cannot evaluate destructors",
- self.mode))
- .emit();
- }
- }
- }
-
- match *kind {
- TerminatorKind::DropAndReplace { ref value, .. } => {
- self.assign(place, ValueSource::DropAndReplace(value), location);
- self.visit_operand(value, location);
- }
- _ => {}
- }
- } else {
- // Qualify any operands inside other terminators.
- self.super_terminator_kind(kind, location);
- }
- }
-
- fn visit_assign(&mut self,
- dest: &Place<'tcx>,
- rvalue: &Rvalue<'tcx>,
- location: Location) {
- debug!("visit_assign: dest={:?} rvalue={:?} location={:?}", dest, rvalue, location);
- self.assign(dest, ValueSource::Rvalue(rvalue), location);
-
- self.visit_rvalue(rvalue, location);
- }
-
- fn visit_source_info(&mut self, source_info: &SourceInfo) {
- debug!("visit_source_info: source_info={:?}", source_info);
- self.span = source_info.span;
- }
-
- fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
- debug!("visit_statement: statement={:?} location={:?}", statement, location);
- match statement.kind {
- StatementKind::Assign(..) => {
- self.super_statement(statement, location);
- }
- StatementKind::FakeRead(FakeReadCause::ForMatchedPlace, _) => {
- if !self.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
- self.tcx.sess.delay_span_bug(
- self.span,
- "complex control flow is forbidden in a const context",
- );
- }
- }
- // FIXME(eddyb) should these really do nothing?
- StatementKind::FakeRead(..) |
- StatementKind::SetDiscriminant { .. } |
- StatementKind::StorageLive(_) |
- StatementKind::StorageDead(_) |
- StatementKind::InlineAsm {..} |
- StatementKind::Retag { .. } |
- StatementKind::AscribeUserType(..) |
- StatementKind::Nop => {}
- }
- }
-}
-
-pub fn provide(providers: &mut Providers<'_>) {
- *providers = Providers {
- mir_const_qualif,
- ..*providers
- };
-}
-
-// FIXME(eddyb) this is only left around for the validation logic
-// in `promote_consts`, see the comment in `validate_operand`.
-pub(super) const QUALIF_ERROR_BIT: u8 = 1 << 2;
-
-fn mir_const_qualif(tcx: TyCtxt<'_>, def_id: DefId) -> u8 {
- // N.B., this `borrow()` is guaranteed to be valid (i.e., the value
- // cannot yet be stolen), because `mir_validated()`, which steals
- // from `mir_const(), forces this query to execute before
- // performing the steal.
- let body = &tcx.mir_const(def_id).borrow();
-
- if body.return_ty().references_error() {
- tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors");
- return QUALIF_ERROR_BIT;
- }
-
- Checker::new(tcx, def_id, body, Mode::Const).check_const()
-}
-
-pub struct QualifyAndPromoteConstants<'tcx> {
- pub promoted: Cell<IndexVec<Promoted, Body<'tcx>>>,
-}
-
-impl<'tcx> Default for QualifyAndPromoteConstants<'tcx> {
- fn default() -> Self {
- QualifyAndPromoteConstants {
- promoted: Cell::new(IndexVec::new()),
- }
- }
-}
-
-impl<'tcx> MirPass<'tcx> for QualifyAndPromoteConstants<'tcx> {
- fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, body: &mut Body<'tcx>) {
- // There's not really any point in promoting errorful MIR.
- if body.return_ty().references_error() {
- tcx.sess.delay_span_bug(body.span, "QualifyAndPromoteConstants: MIR had errors");
- return;
- }
-
- if src.promoted.is_some() {
- return;
- }
-
- let def_id = src.def_id();
- let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
-
- let mode = determine_mode(tcx, hir_id, def_id);
-
- debug!("run_pass: mode={:?}", mode);
- if let Mode::NonConstFn = mode {
- // No need to const-check a non-const `fn` now that we don't do promotion here.
- return;
- } else if let Mode::ConstFn = mode {
- let mut checker = Checker::new(tcx, def_id, body, mode);
- let use_min_const_fn_checks =
- !tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you &&
- tcx.is_min_const_fn(def_id);
- if use_min_const_fn_checks {
- // Enforce `min_const_fn` for stable `const fn`s.
- use super::qualify_min_const_fn::is_min_const_fn;
- if let Err((span, err)) = is_min_const_fn(tcx, def_id, body) {
- error_min_const_fn_violation(tcx, span, err);
- return;
- }
- }
-
- // `check_const` should not produce any errors, but better safe than sorry
- // FIXME(#53819)
- // Enforce a constant-like CFG for `const fn`.
- checker.check_const();
- } else {
- check_short_circuiting_in_const_local(tcx, body, mode);
-
- match mode {
- Mode::Const => tcx.mir_const_qualif(def_id),
- _ => Checker::new(tcx, def_id, body, mode).check_const(),
- };
- }
-
- if mode == Mode::Static && !tcx.has_attr(def_id, sym::thread_local) {
- // `static`s (not `static mut`s) which are not `#[thread_local]` must be `Sync`.
- check_static_is_sync(tcx, body, hir_id);
- }
- }
-}
-
-fn determine_mode(tcx: TyCtxt<'_>, hir_id: HirId, def_id: DefId) -> Mode {
- match tcx.hir().body_owner_kind(hir_id) {
- hir::BodyOwnerKind::Closure => Mode::NonConstFn,
- hir::BodyOwnerKind::Fn if tcx.is_const_fn(def_id) => Mode::ConstFn,
- hir::BodyOwnerKind::Fn => Mode::NonConstFn,
- hir::BodyOwnerKind::Const => Mode::Const,
- hir::BodyOwnerKind::Static(hir::Mutability::Immutable) => Mode::Static,
- hir::BodyOwnerKind::Static(hir::Mutability::Mutable) => Mode::StaticMut,
- }
-}
-
-fn error_min_const_fn_violation(tcx: TyCtxt<'_>, span: Span, msg: Cow<'_, str>) {
- struct_span_err!(tcx.sess, span, E0723, "{}", msg)
- .note("for more information, see issue https://github.com/rust-lang/rust/issues/57563")
- .help("add `#![feature(const_fn)]` to the crate attributes to enable")
- .emit();
-}
-
-fn check_short_circuiting_in_const_local(tcx: TyCtxt<'_>, body: &mut Body<'tcx>, mode: Mode) {
- if body.control_flow_destroyed.is_empty() {
- return;
- }
-
- let mut locals = body.vars_iter();
- if let Some(local) = locals.next() {
- let span = body.local_decls[local].source_info.span;
- let mut error = tcx.sess.struct_span_err(
- span,
- &format!(
- "new features like let bindings are not permitted in {}s \
- which also use short circuiting operators",
- mode,
- ),
- );
- for (span, kind) in body.control_flow_destroyed.iter() {
- error.span_note(
- *span,
- &format!("use of {} here does not actually short circuit due to \
- the const evaluator presently not being able to do control flow. \
- See https://github.com/rust-lang/rust/issues/49146 for more \
- information.", kind),
- );
- }
- for local in locals {
- let span = body.local_decls[local].source_info.span;
- error.span_note(span, "more locals defined here");
- }
- error.emit();
- }
-}
-
-fn check_static_is_sync(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, hir_id: HirId) {
- let ty = body.return_ty();
- tcx.infer_ctxt().enter(|infcx| {
- let cause = traits::ObligationCause::new(body.span, hir_id, traits::SharedStatic);
- let mut fulfillment_cx = traits::FulfillmentContext::new();
- let sync_def_id = tcx.require_lang_item(lang_items::SyncTraitLangItem, Some(body.span));
- fulfillment_cx.register_bound(&infcx, ty::ParamEnv::empty(), ty, sync_def_id, cause);
- if let Err(err) = fulfillment_cx.select_all_or_error(&infcx) {
- infcx.report_fulfillment_errors(&err, None, false);
- }
- });
-}
-
-fn validator_mismatch(
- tcx: TyCtxt<'tcx>,
- body: &Body<'tcx>,
- mut old_errors: Vec<(Span, String)>,
- mut new_errors: Vec<(Span, String)>,
-) {
- error!("old validator: {:?}", old_errors);
- error!("new validator: {:?}", new_errors);
-
- // ICE on nightly if the validators do not emit exactly the same errors.
- // Users can supress this panic with an unstable compiler flag (hopefully after
- // filing an issue).
- let opts = &tcx.sess.opts;
- let strict_validation_enabled = opts.unstable_features.is_nightly_build()
- && !opts.debugging_opts.suppress_const_validation_back_compat_ice;
-
- if !strict_validation_enabled {
- return;
- }
-
- // If this difference would cause a regression from the old to the new or vice versa, trigger
- // the ICE.
- if old_errors.is_empty() || new_errors.is_empty() {
- span_bug!(body.span, "{}", VALIDATOR_MISMATCH_ERR);
- }
-
- // HACK: Borrows that would allow mutation are forbidden in const contexts, but they cause the
- // new validator to be more conservative about when a dropped local has been moved out of.
- //
- // Supress the mismatch ICE in cases where the validators disagree only on the number of
- // `LiveDrop` errors and both observe the same sequence of `MutBorrow`s.
-
- let is_live_drop = |(_, s): &mut (_, String)| s.starts_with("LiveDrop");
- let is_mut_borrow = |(_, s): &&(_, String)| s.starts_with("MutBorrow");
-
- let old_live_drops: Vec<_> = old_errors.drain_filter(is_live_drop).collect();
- let new_live_drops: Vec<_> = new_errors.drain_filter(is_live_drop).collect();
-
- let only_live_drops_differ = old_live_drops != new_live_drops && old_errors == new_errors;
-
- let old_mut_borrows = old_errors.iter().filter(is_mut_borrow);
- let new_mut_borrows = new_errors.iter().filter(is_mut_borrow);
-
- let at_least_one_mut_borrow = old_mut_borrows.clone().next().is_some();
-
- if only_live_drops_differ && at_least_one_mut_borrow && old_mut_borrows.eq(new_mut_borrows) {
- return;
- }
-
- span_bug!(body.span, "{}", VALIDATOR_MISMATCH_ERR);
-}
-
-const VALIDATOR_MISMATCH_ERR: &str =
- r"Disagreement between legacy and dataflow-based const validators.
- After filing an issue, use `-Zsuppress-const-validation-back-compat-ice` to compile your code.";
projects / rust.git / commitdiff