diff options
Diffstat (limited to 'compiler/rustc_const_eval/src/transform/check_consts/ops.rs')
| -rw-r--r-- | compiler/rustc_const_eval/src/transform/check_consts/ops.rs | 771 |
1 files changed, 771 insertions, 0 deletions
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/ops.rs b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs new file mode 100644 index 000000000..338022616 --- /dev/null +++ b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs @@ -0,0 +1,771 @@ +//! Concrete error types for all operations which may be invalid in a certain const context. + +use hir::def_id::LocalDefId; +use rustc_errors::{ + error_code, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed, +}; +use rustc_hir as hir; +use rustc_hir::def_id::DefId; +use rustc_infer::infer::TyCtxtInferExt; +use rustc_infer::traits::{ImplSource, Obligation, ObligationCause}; +use rustc_middle::mir; +use rustc_middle::ty::print::with_no_trimmed_paths; +use rustc_middle::ty::subst::{GenericArgKind, SubstsRef}; +use rustc_middle::ty::{ + suggest_constraining_type_param, Adt, Closure, DefIdTree, FnDef, FnPtr, Param, TraitPredicate, + Ty, +}; +use rustc_middle::ty::{Binder, BoundConstness, ImplPolarity, TraitRef}; +use rustc_session::parse::feature_err; +use rustc_span::symbol::sym; +use rustc_span::{BytePos, Pos, Span, Symbol}; +use rustc_trait_selection::traits::SelectionContext; + +use super::ConstCx; +use crate::errors::{ + MutDerefErr, NonConstOpErr, PanicNonStrErr, RawPtrToIntErr, StaticAccessErr, + TransientMutBorrowErr, TransientMutBorrowErrRaw, +}; +use crate::util::{call_kind, CallDesugaringKind, CallKind}; + +#[derive(Clone, Copy, Debug, PartialEq, Eq)] +pub enum Status { + Allowed, + Unstable(Symbol), + Forbidden, +} + +#[derive(Clone, Copy)] +pub enum DiagnosticImportance { + /// An operation that must be removed for const-checking to pass. + Primary, + + /// An operation that causes const-checking to fail, but is usually a side-effect of a `Primary` operation elsewhere. + Secondary, +} + +/// An operation that is not *always* allowed in a const context. +pub trait NonConstOp<'tcx>: std::fmt::Debug { + /// Returns an enum indicating whether this operation is allowed within the given item. + fn status_in_item(&self, _ccx: &ConstCx<'_, 'tcx>) -> Status { + Status::Forbidden + } + + fn importance(&self) -> DiagnosticImportance { + DiagnosticImportance::Primary + } + + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>; +} + +#[derive(Debug)] +pub struct FloatingPointOp; +impl<'tcx> NonConstOp<'tcx> for FloatingPointOp { + fn status_in_item(&self, ccx: &ConstCx<'_, 'tcx>) -> Status { + if ccx.const_kind() == hir::ConstContext::ConstFn { + Status::Unstable(sym::const_fn_floating_point_arithmetic) + } else { + Status::Allowed + } + } + + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + feature_err( + &ccx.tcx.sess.parse_sess, + sym::const_fn_floating_point_arithmetic, + span, + &format!("floating point arithmetic is not allowed in {}s", ccx.const_kind()), + ) + } +} + +/// A function call where the callee is a pointer. +#[derive(Debug)] +pub struct FnCallIndirect; +impl<'tcx> NonConstOp<'tcx> for FnCallIndirect { + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + ccx.tcx.sess.struct_span_err( + span, + &format!("function pointer calls are not allowed in {}s", ccx.const_kind()), + ) + } +} + +/// A function call where the callee is not marked as `const`. +#[derive(Debug, Clone, Copy)] +pub struct FnCallNonConst<'tcx> { + pub caller: LocalDefId, + pub callee: DefId, + pub substs: SubstsRef<'tcx>, + pub span: Span, + pub from_hir_call: bool, +} + +impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> { + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + _: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let FnCallNonConst { caller, callee, substs, span, from_hir_call } = *self; + let ConstCx { tcx, param_env, .. } = *ccx; + + let diag_trait = |err, self_ty: Ty<'_>, trait_id| { + let trait_ref = TraitRef::from_method(tcx, trait_id, substs); + + match self_ty.kind() { + Param(param_ty) => { + debug!(?param_ty); + let caller_hir_id = tcx.hir().local_def_id_to_hir_id(caller); + if let Some(generics) = tcx.hir().get(caller_hir_id).generics() { + let constraint = with_no_trimmed_paths!(format!( + "~const {}", + trait_ref.print_only_trait_path() + )); + suggest_constraining_type_param( + tcx, + generics, + err, + ¶m_ty.name.as_str(), + &constraint, + None, + ); + } + } + Adt(..) => { + let obligation = Obligation::new( + ObligationCause::dummy(), + param_env, + Binder::dummy(TraitPredicate { + trait_ref, + constness: BoundConstness::NotConst, + polarity: ImplPolarity::Positive, + }), + ); + + let implsrc = tcx.infer_ctxt().enter(|infcx| { + let mut selcx = SelectionContext::new(&infcx); + selcx.select(&obligation) + }); + + if let Ok(Some(ImplSource::UserDefined(data))) = implsrc { + let span = tcx.def_span(data.impl_def_id); + err.span_note(span, "impl defined here, but it is not `const`"); + } + } + _ => {} + } + }; + + let call_kind = call_kind(tcx, ccx.param_env, callee, substs, span, from_hir_call, None); + + debug!(?call_kind); + + let mut err = match call_kind { + CallKind::Normal { desugaring: Some((kind, self_ty)), .. } => { + macro_rules! error { + ($fmt:literal) => { + struct_span_err!(tcx.sess, span, E0015, $fmt, self_ty, ccx.const_kind()) + }; + } + + let mut err = match kind { + CallDesugaringKind::ForLoopIntoIter => { + error!("cannot convert `{}` into an iterator in {}s") + } + CallDesugaringKind::QuestionBranch => { + error!("`?` cannot determine the branch of `{}` in {}s") + } + CallDesugaringKind::QuestionFromResidual => { + error!("`?` cannot convert from residual of `{}` in {}s") + } + CallDesugaringKind::TryBlockFromOutput => { + error!("`try` block cannot convert `{}` to the result in {}s") + } + }; + + diag_trait(&mut err, self_ty, kind.trait_def_id(tcx)); + err + } + CallKind::FnCall { fn_trait_id, self_ty } => { + let mut err = struct_span_err!( + tcx.sess, + span, + E0015, + "cannot call non-const closure in {}s", + ccx.const_kind(), + ); + + match self_ty.kind() { + FnDef(def_id, ..) => { + let span = tcx.def_span(*def_id); + if ccx.tcx.is_const_fn_raw(*def_id) { + span_bug!(span, "calling const FnDef errored when it shouldn't"); + } + + err.span_note(span, "function defined here, but it is not `const`"); + } + FnPtr(..) => { + err.note(&format!( + "function pointers need an RFC before allowed to be called in {}s", + ccx.const_kind() + )); + } + Closure(..) => { + err.note(&format!( + "closures need an RFC before allowed to be called in {}s", + ccx.const_kind() + )); + } + _ => {} + } + + diag_trait(&mut err, self_ty, fn_trait_id); + err + } + CallKind::Operator { trait_id, self_ty, .. } => { + let mut err = struct_span_err!( + tcx.sess, + span, + E0015, + "cannot call non-const operator in {}s", + ccx.const_kind() + ); + + if Some(trait_id) == ccx.tcx.lang_items().eq_trait() { + match (substs[0].unpack(), substs[1].unpack()) { + (GenericArgKind::Type(self_ty), GenericArgKind::Type(rhs_ty)) + if self_ty == rhs_ty + && self_ty.is_ref() + && self_ty.peel_refs().is_primitive() => + { + let mut num_refs = 0; + let mut tmp_ty = self_ty; + while let rustc_middle::ty::Ref(_, inner_ty, _) = tmp_ty.kind() { + num_refs += 1; + tmp_ty = *inner_ty; + } + let deref = "*".repeat(num_refs); + + if let Ok(call_str) = ccx.tcx.sess.source_map().span_to_snippet(span) { + if let Some(eq_idx) = call_str.find("==") { + if let Some(rhs_idx) = + call_str[(eq_idx + 2)..].find(|c: char| !c.is_whitespace()) + { + let rhs_pos = + span.lo() + BytePos::from_usize(eq_idx + 2 + rhs_idx); + let rhs_span = span.with_lo(rhs_pos).with_hi(rhs_pos); + err.multipart_suggestion( + "consider dereferencing here", + vec![ + (span.shrink_to_lo(), deref.clone()), + (rhs_span, deref), + ], + Applicability::MachineApplicable, + ); + } + } + } + } + _ => {} + } + } + + diag_trait(&mut err, self_ty, trait_id); + err + } + CallKind::DerefCoercion { deref_target, deref_target_ty, self_ty } => { + let mut err = struct_span_err!( + tcx.sess, + span, + E0015, + "cannot perform deref coercion on `{}` in {}s", + self_ty, + ccx.const_kind() + ); + + err.note(&format!("attempting to deref into `{}`", deref_target_ty)); + + // Check first whether the source is accessible (issue #87060) + if tcx.sess.source_map().is_span_accessible(deref_target) { + err.span_note(deref_target, "deref defined here"); + } + + diag_trait(&mut err, self_ty, tcx.lang_items().deref_trait().unwrap()); + err + } + _ if tcx.opt_parent(callee) == tcx.get_diagnostic_item(sym::ArgumentV1Methods) => { + struct_span_err!( + ccx.tcx.sess, + span, + E0015, + "cannot call non-const formatting macro in {}s", + ccx.const_kind(), + ) + } + _ => struct_span_err!( + ccx.tcx.sess, + span, + E0015, + "cannot call non-const fn `{}` in {}s", + ccx.tcx.def_path_str_with_substs(callee, substs), + ccx.const_kind(), + ), + }; + + err.note(&format!( + "calls in {}s are limited to constant functions, \ + tuple structs and tuple variants", + ccx.const_kind(), + )); + + err + } +} + +/// A call to an `#[unstable]` const fn or `#[rustc_const_unstable]` function. +/// +/// Contains the name of the feature that would allow the use of this function. +#[derive(Debug)] +pub struct FnCallUnstable(pub DefId, pub Option<Symbol>); + +impl<'tcx> NonConstOp<'tcx> for FnCallUnstable { + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let FnCallUnstable(def_id, feature) = *self; + + let mut err = ccx.tcx.sess.struct_span_err( + span, + &format!("`{}` is not yet stable as a const fn", ccx.tcx.def_path_str(def_id)), + ); + + if ccx.is_const_stable_const_fn() { + err.help("const-stable functions can only call other const-stable functions"); + } else if ccx.tcx.sess.is_nightly_build() { + if let Some(feature) = feature { + err.help(&format!( + "add `#![feature({})]` to the crate attributes to enable", + feature + )); + } + } + + err + } +} + +#[derive(Debug)] +pub struct Generator(pub hir::GeneratorKind); +impl<'tcx> NonConstOp<'tcx> for Generator { + fn status_in_item(&self, _: &ConstCx<'_, 'tcx>) -> Status { + if let hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Block) = self.0 { + Status::Unstable(sym::const_async_blocks) + } else { + Status::Forbidden + } + } + + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let msg = format!("{}s are not allowed in {}s", self.0, ccx.const_kind()); + if let hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Block) = self.0 { + feature_err(&ccx.tcx.sess.parse_sess, sym::const_async_blocks, span, &msg) + } else { + ccx.tcx.sess.struct_span_err(span, &msg) + } + } +} + +#[derive(Debug)] +pub struct HeapAllocation; +impl<'tcx> NonConstOp<'tcx> for HeapAllocation { + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let mut err = struct_span_err!( + ccx.tcx.sess, + span, + E0010, + "allocations are not allowed in {}s", + ccx.const_kind() + ); + err.span_label(span, format!("allocation not allowed in {}s", ccx.const_kind())); + if ccx.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 + } +} + +#[derive(Debug)] +pub struct InlineAsm; +impl<'tcx> NonConstOp<'tcx> for InlineAsm { + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + struct_span_err!( + ccx.tcx.sess, + span, + E0015, + "inline assembly is not allowed in {}s", + ccx.const_kind() + ) + } +} + +#[derive(Debug)] +pub struct LiveDrop { + pub dropped_at: Option<Span>, +} +impl<'tcx> NonConstOp<'tcx> for LiveDrop { + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let mut err = struct_span_err!( + ccx.tcx.sess, + span, + E0493, + "destructors cannot be evaluated at compile-time" + ); + err.span_label(span, format!("{}s cannot evaluate destructors", ccx.const_kind())); + if let Some(span) = self.dropped_at { + err.span_label(span, "value is dropped here"); + } + err + } +} + +#[derive(Debug)] +/// A borrow of a type that contains an `UnsafeCell` somewhere. The borrow never escapes to +/// the final value of the constant. +pub struct TransientCellBorrow; +impl<'tcx> NonConstOp<'tcx> for TransientCellBorrow { + fn status_in_item(&self, _: &ConstCx<'_, 'tcx>) -> Status { + Status::Unstable(sym::const_refs_to_cell) + } + fn importance(&self) -> DiagnosticImportance { + // The cases that cannot possibly work will already emit a `CellBorrow`, so we should + // not additionally emit a feature gate error if activating the feature gate won't work. + DiagnosticImportance::Secondary + } + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + feature_err( + &ccx.tcx.sess.parse_sess, + sym::const_refs_to_cell, + span, + "cannot borrow here, since the borrowed element may contain interior mutability", + ) + } +} + +#[derive(Debug)] +/// A borrow of a type that contains an `UnsafeCell` somewhere. The borrow might escape to +/// the final value of the constant, and thus we cannot allow this (for now). We may allow +/// it in the future for static items. +pub struct CellBorrow; +impl<'tcx> NonConstOp<'tcx> for CellBorrow { + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let mut err = struct_span_err!( + ccx.tcx.sess, + span, + E0492, + "{}s cannot refer to interior mutable data", + ccx.const_kind(), + ); + err.span_label( + span, + "this borrow of an interior mutable value may end up in the final value", + ); + if let hir::ConstContext::Static(_) = ccx.const_kind() { + err.help( + "to fix this, the value can be extracted to a separate \ + `static` item and then referenced", + ); + } + if ccx.tcx.sess.teach(&err.get_code().unwrap()) { + err.note( + "A constant containing interior mutable data behind a reference can allow you + to modify that data. This would make multiple uses of a constant to be able to + see different values and allow circumventing the `Send` and `Sync` requirements + for shared mutable data, which is unsound.", + ); + } + err + } +} + +#[derive(Debug)] +/// This op is for `&mut` borrows in the trailing expression of a constant +/// which uses the "enclosing scopes rule" to leak its locals into anonymous +/// static or const items. +pub struct MutBorrow(pub hir::BorrowKind); + +impl<'tcx> NonConstOp<'tcx> for MutBorrow { + fn status_in_item(&self, _ccx: &ConstCx<'_, 'tcx>) -> Status { + Status::Forbidden + } + + fn importance(&self) -> DiagnosticImportance { + // If there were primary errors (like non-const function calls), do not emit further + // errors about mutable references. + DiagnosticImportance::Secondary + } + + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let raw = match self.0 { + hir::BorrowKind::Raw => "raw ", + hir::BorrowKind::Ref => "", + }; + + let mut err = struct_span_err!( + ccx.tcx.sess, + span, + E0764, + "{}mutable references are not allowed in the final value of {}s", + raw, + ccx.const_kind(), + ); + + if ccx.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 + } +} + +#[derive(Debug)] +pub struct TransientMutBorrow(pub hir::BorrowKind); + +impl<'tcx> NonConstOp<'tcx> for TransientMutBorrow { + fn status_in_item(&self, _: &ConstCx<'_, 'tcx>) -> Status { + Status::Unstable(sym::const_mut_refs) + } + + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let kind = ccx.const_kind(); + match self.0 { + hir::BorrowKind::Raw => ccx + .tcx + .sess + .create_feature_err(TransientMutBorrowErrRaw { span, kind }, sym::const_mut_refs), + hir::BorrowKind::Ref => ccx + .tcx + .sess + .create_feature_err(TransientMutBorrowErr { span, kind }, sym::const_mut_refs), + } + } +} + +#[derive(Debug)] +pub struct MutDeref; +impl<'tcx> NonConstOp<'tcx> for MutDeref { + fn status_in_item(&self, _: &ConstCx<'_, 'tcx>) -> Status { + Status::Unstable(sym::const_mut_refs) + } + + fn importance(&self) -> DiagnosticImportance { + // Usually a side-effect of a `TransientMutBorrow` somewhere. + DiagnosticImportance::Secondary + } + + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + ccx.tcx + .sess + .create_feature_err(MutDerefErr { span, kind: ccx.const_kind() }, sym::const_mut_refs) + } +} + +/// A call to a `panic()` lang item where the first argument is _not_ a `&str`. +#[derive(Debug)] +pub struct PanicNonStr; +impl<'tcx> NonConstOp<'tcx> for PanicNonStr { + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + ccx.tcx.sess.create_err(PanicNonStrErr { span }) + } +} + +/// Comparing raw pointers for equality. +/// Not currently intended to ever be allowed, even behind a feature gate: operation depends on +/// allocation base addresses that are not known at compile-time. +#[derive(Debug)] +pub struct RawPtrComparison; +impl<'tcx> NonConstOp<'tcx> for RawPtrComparison { + fn build_error( + &self, + _: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + span_bug!(span, "raw ptr comparison should already be caught in the trait system"); + } +} + +#[derive(Debug)] +pub struct RawMutPtrDeref; +impl<'tcx> NonConstOp<'tcx> for RawMutPtrDeref { + fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status { + Status::Unstable(sym::const_mut_refs) + } + + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + feature_err( + &ccx.tcx.sess.parse_sess, + sym::const_mut_refs, + span, + &format!("dereferencing raw mutable pointers in {}s is unstable", ccx.const_kind(),), + ) + } +} + +/// Casting raw pointer or function pointer to an integer. +/// Not currently intended to ever be allowed, even behind a feature gate: operation depends on +/// allocation base addresses that are not known at compile-time. +#[derive(Debug)] +pub struct RawPtrToIntCast; +impl<'tcx> NonConstOp<'tcx> for RawPtrToIntCast { + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + ccx.tcx.sess.create_err(RawPtrToIntErr { span }) + } +} + +/// An access to a (non-thread-local) `static`. +#[derive(Debug)] +pub struct StaticAccess; +impl<'tcx> NonConstOp<'tcx> for StaticAccess { + fn status_in_item(&self, ccx: &ConstCx<'_, 'tcx>) -> Status { + if let hir::ConstContext::Static(_) = ccx.const_kind() { + Status::Allowed + } else { + Status::Forbidden + } + } + + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + ccx.tcx.sess.create_err(StaticAccessErr { + span, + kind: ccx.const_kind(), + teach: ccx.tcx.sess.teach(&error_code!(E0013)).then_some(()), + }) + } +} + +/// An access to a thread-local `static`. +#[derive(Debug)] +pub struct ThreadLocalAccess; +impl<'tcx> NonConstOp<'tcx> for ThreadLocalAccess { + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + ccx.tcx.sess.create_err(NonConstOpErr { span }) + } +} + +// Types that cannot appear in the signature or locals of a `const fn`. +pub mod ty { + use super::*; + + #[derive(Debug)] + pub struct MutRef(pub mir::LocalKind); + impl<'tcx> NonConstOp<'tcx> for MutRef { + fn status_in_item(&self, _ccx: &ConstCx<'_, 'tcx>) -> Status { + Status::Unstable(sym::const_mut_refs) + } + + fn importance(&self) -> DiagnosticImportance { + match self.0 { + mir::LocalKind::Var | mir::LocalKind::Temp => DiagnosticImportance::Secondary, + mir::LocalKind::ReturnPointer | mir::LocalKind::Arg => { + DiagnosticImportance::Primary + } + } + } + + fn build_error( + &self, + ccx: &ConstCx<'_, 'tcx>, + span: Span, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + feature_err( + &ccx.tcx.sess.parse_sess, + sym::const_mut_refs, + span, + &format!("mutable references are not allowed in {}s", ccx.const_kind()), + ) + } + } +} |