| //! Concrete error types for all operations which may be invalid in a certain const context. |
| |
| use rustc_errors::{struct_span_err, DiagnosticBuilder}; |
| use rustc_hir as hir; |
| use rustc_hir::def_id::DefId; |
| use rustc_middle::mir; |
| use rustc_session::config::nightly_options; |
| use rustc_session::parse::feature_err; |
| use rustc_span::symbol::sym; |
| use rustc_span::{Span, Symbol}; |
| |
| use super::ConstCx; |
| |
| #[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: std::fmt::Debug { |
| /// Returns an enum indicating whether this operation is allowed within the given item. |
| fn status_in_item(&self, _ccx: &ConstCx<'_, '_>) -> Status { |
| Status::Forbidden |
| } |
| |
| fn importance(&self) -> DiagnosticImportance { |
| DiagnosticImportance::Primary |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx>; |
| } |
| |
| #[derive(Debug)] |
| pub struct FloatingPointOp; |
| impl NonConstOp for FloatingPointOp { |
| fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> 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> { |
| 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 NonConstOp for FnCallIndirect { |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| ccx.tcx.sess.struct_span_err(span, "function pointers are not allowed in const fn") |
| } |
| } |
| |
| /// A function call where the callee is not marked as `const`. |
| #[derive(Debug)] |
| pub struct FnCallNonConst(pub DefId); |
| impl NonConstOp for FnCallNonConst { |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| struct_span_err!( |
| ccx.tcx.sess, |
| span, |
| E0015, |
| "calls in {}s are limited to constant functions, \ |
| tuple structs and tuple variants", |
| ccx.const_kind(), |
| ) |
| } |
| } |
| |
| /// A call to a `#[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 NonConstOp for FnCallUnstable { |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| 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 nightly_options::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 FnPtrCast; |
| impl NonConstOp for FnPtrCast { |
| fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status { |
| if ccx.const_kind() != hir::ConstContext::ConstFn { |
| Status::Allowed |
| } else { |
| Status::Unstable(sym::const_fn_fn_ptr_basics) |
| } |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_fn_fn_ptr_basics, |
| span, |
| &format!("function pointer casts are not allowed in {}s", ccx.const_kind()), |
| ) |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct Generator(pub hir::GeneratorKind); |
| impl NonConstOp for Generator { |
| fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status { |
| Status::Forbidden |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| let msg = format!("{}s are not allowed in {}s", self.0, ccx.const_kind()); |
| ccx.tcx.sess.struct_span_err(span, &msg) |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct HeapAllocation; |
| impl NonConstOp for HeapAllocation { |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| 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 NonConstOp for InlineAsm { |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| 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 NonConstOp for LiveDrop { |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| 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)] |
| pub struct CellBorrow; |
| impl NonConstOp for CellBorrow { |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| struct_span_err!( |
| ccx.tcx.sess, |
| span, |
| E0492, |
| "cannot borrow a constant which may contain \ |
| interior mutability, create a static instead" |
| ) |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct MutBorrow(pub hir::BorrowKind); |
| |
| impl NonConstOp for MutBorrow { |
| fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status { |
| // Forbid everywhere except in const fn with a feature gate |
| if ccx.const_kind() == hir::ConstContext::ConstFn { |
| Status::Unstable(sym::const_mut_refs) |
| } else { |
| Status::Forbidden |
| } |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| let raw = match self.0 { |
| hir::BorrowKind::Raw => "raw ", |
| hir::BorrowKind::Ref => "", |
| }; |
| |
| let mut err = if ccx.const_kind() == hir::ConstContext::ConstFn { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_mut_refs, |
| span, |
| &format!("{}mutable references are not allowed in {}s", raw, ccx.const_kind()), |
| ) |
| } else { |
| let mut err = struct_span_err!( |
| ccx.tcx.sess, |
| span, |
| E0764, |
| "{}mutable references are not allowed in {}s", |
| raw, |
| ccx.const_kind(), |
| ); |
| err.span_label(span, format!("`&{}mut` is only allowed in `const fn`", raw)); |
| err |
| }; |
| 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 MutDeref; |
| impl NonConstOp for MutDeref { |
| fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status { |
| Status::Unstable(sym::const_mut_refs) |
| } |
| |
| fn importance(&self) -> DiagnosticImportance { |
| // Usually a side-effect of a `MutBorrow` somewhere. |
| DiagnosticImportance::Secondary |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_mut_refs, |
| span, |
| &format!("mutation through a reference is not allowed in {}s", ccx.const_kind()), |
| ) |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct Panic; |
| impl NonConstOp for Panic { |
| fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status { |
| Status::Unstable(sym::const_panic) |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_panic, |
| span, |
| &format!("panicking in {}s is unstable", ccx.const_kind()), |
| ) |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct RawPtrComparison; |
| impl NonConstOp for RawPtrComparison { |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| let mut err = ccx |
| .tcx |
| .sess |
| .struct_span_err(span, "pointers cannot be reliably compared during const eval."); |
| err.note( |
| "see issue #53020 <https://github.com/rust-lang/rust/issues/53020> \ |
| for more information", |
| ); |
| err |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct RawPtrDeref; |
| impl NonConstOp for RawPtrDeref { |
| fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status { |
| Status::Unstable(sym::const_raw_ptr_deref) |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_raw_ptr_deref, |
| span, |
| &format!("dereferencing raw pointers in {}s is unstable", ccx.const_kind(),), |
| ) |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct RawPtrToIntCast; |
| impl NonConstOp for RawPtrToIntCast { |
| fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status { |
| Status::Unstable(sym::const_raw_ptr_to_usize_cast) |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_raw_ptr_to_usize_cast, |
| span, |
| &format!("casting pointers to integers in {}s is unstable", ccx.const_kind(),), |
| ) |
| } |
| } |
| |
| /// An access to a (non-thread-local) `static`. |
| #[derive(Debug)] |
| pub struct StaticAccess; |
| impl NonConstOp for StaticAccess { |
| fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> 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> { |
| let mut err = struct_span_err!( |
| ccx.tcx.sess, |
| span, |
| E0013, |
| "{}s cannot refer to statics", |
| ccx.const_kind() |
| ); |
| err.help( |
| "consider extracting the value of the `static` to a `const`, and referring to that", |
| ); |
| if ccx.tcx.sess.teach(&err.get_code().unwrap()) { |
| err.note( |
| "`static` and `const` variables can refer to other `const` variables. \ |
| A `const` variable, however, cannot refer to a `static` variable.", |
| ); |
| err.help("To fix this, the value can be extracted to a `const` and then used."); |
| } |
| err |
| } |
| } |
| |
| /// An access to a thread-local `static`. |
| #[derive(Debug)] |
| pub struct ThreadLocalAccess; |
| impl NonConstOp for ThreadLocalAccess { |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| struct_span_err!( |
| ccx.tcx.sess, |
| span, |
| E0625, |
| "thread-local statics cannot be \ |
| accessed at compile-time" |
| ) |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct Transmute; |
| impl NonConstOp for Transmute { |
| fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status { |
| if ccx.const_kind() != hir::ConstContext::ConstFn { |
| Status::Allowed |
| } else { |
| Status::Unstable(sym::const_fn_transmute) |
| } |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| let mut err = feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_fn_transmute, |
| span, |
| &format!("`transmute` is not allowed in {}s", ccx.const_kind()), |
| ); |
| err.note("`transmute` is only allowed in constants and statics for now"); |
| err |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct UnionAccess; |
| impl NonConstOp for UnionAccess { |
| fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status { |
| // Union accesses are stable in all contexts except `const fn`. |
| if ccx.const_kind() != hir::ConstContext::ConstFn { |
| Status::Allowed |
| } else { |
| Status::Unstable(sym::const_fn_union) |
| } |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_fn_union, |
| span, |
| "unions in const fn are unstable", |
| ) |
| } |
| } |
| |
| /// See [#64992]. |
| /// |
| /// [#64992]: https://github.com/rust-lang/rust/issues/64992 |
| #[derive(Debug)] |
| pub struct UnsizingCast; |
| impl NonConstOp for UnsizingCast { |
| fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status { |
| mcf_status_in_item(ccx) |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| mcf_build_error( |
| ccx, |
| span, |
| "unsizing casts to types besides slices are not allowed in const fn", |
| ) |
| } |
| } |
| |
| // 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 NonConstOp for MutRef { |
| fn status_in_item(&self, _ccx: &ConstCx<'_, '_>) -> 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> { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_mut_refs, |
| span, |
| &format!("mutable references are not allowed in {}s", ccx.const_kind()), |
| ) |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct FnPtr(pub mir::LocalKind); |
| impl NonConstOp for FnPtr { |
| fn importance(&self) -> DiagnosticImportance { |
| match self.0 { |
| mir::LocalKind::Var | mir::LocalKind::Temp => DiagnosticImportance::Secondary, |
| mir::LocalKind::ReturnPointer | mir::LocalKind::Arg => { |
| DiagnosticImportance::Primary |
| } |
| } |
| } |
| |
| fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status { |
| if ccx.const_kind() != hir::ConstContext::ConstFn { |
| Status::Allowed |
| } else { |
| Status::Unstable(sym::const_fn_fn_ptr_basics) |
| } |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_fn_fn_ptr_basics, |
| span, |
| &format!("function pointers cannot appear in {}s", ccx.const_kind()), |
| ) |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct ImplTrait; |
| impl NonConstOp for ImplTrait { |
| fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status { |
| Status::Unstable(sym::const_impl_trait) |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_impl_trait, |
| span, |
| &format!("`impl Trait` is not allowed in {}s", ccx.const_kind()), |
| ) |
| } |
| } |
| |
| #[derive(Debug)] |
| pub struct TraitBound(pub mir::LocalKind); |
| impl NonConstOp for TraitBound { |
| fn importance(&self) -> DiagnosticImportance { |
| match self.0 { |
| mir::LocalKind::Var | mir::LocalKind::Temp => DiagnosticImportance::Secondary, |
| mir::LocalKind::ReturnPointer | mir::LocalKind::Arg => { |
| DiagnosticImportance::Primary |
| } |
| } |
| } |
| |
| fn status_in_item(&self, ccx: &ConstCx<'_, '_>) -> Status { |
| mcf_status_in_item(ccx) |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| mcf_build_error( |
| ccx, |
| span, |
| "trait bounds other than `Sized` on const fn parameters are unstable", |
| ) |
| } |
| } |
| |
| /// A trait bound with the `?const Trait` opt-out |
| #[derive(Debug)] |
| pub struct TraitBoundNotConst; |
| impl NonConstOp for TraitBoundNotConst { |
| fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status { |
| Status::Unstable(sym::const_trait_bound_opt_out) |
| } |
| |
| fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> { |
| feature_err( |
| &ccx.tcx.sess.parse_sess, |
| sym::const_trait_bound_opt_out, |
| span, |
| "`?const Trait` syntax is unstable", |
| ) |
| } |
| } |
| } |
| |
| fn mcf_status_in_item(ccx: &ConstCx<'_, '_>) -> Status { |
| if ccx.const_kind() != hir::ConstContext::ConstFn { |
| Status::Allowed |
| } else { |
| Status::Unstable(sym::const_fn) |
| } |
| } |
| |
| fn mcf_build_error(ccx: &ConstCx<'_, 'tcx>, span: Span, msg: &str) -> DiagnosticBuilder<'tcx> { |
| let mut err = struct_span_err!(ccx.tcx.sess, span, E0723, "{}", msg); |
| err.note( |
| "see issue #57563 <https://github.com/rust-lang/rust/issues/57563> \ |
| for more information", |
| ); |
| err.help("add `#![feature(const_fn)]` to the crate attributes to enable"); |
| err |
| } |
