pub mod no_landing_pads;
pub mod nrvo;
pub mod promote_consts;
-pub mod qualify_min_const_fn;
pub mod remove_noop_landing_pads;
pub mod remove_unneeded_drops;
pub mod required_consts;
+++ /dev/null
-use rustc_hir as hir;
-use rustc_hir::def_id::DefId;
-use rustc_middle::mir::*;
-use rustc_middle::ty::subst::GenericArgKind;
-use rustc_middle::ty::{self, adjustment::PointerCast, Ty, TyCtxt};
-use rustc_span::symbol::{sym, Symbol};
-use rustc_span::Span;
-use rustc_target::spec::abi::Abi::RustIntrinsic;
-use std::borrow::Cow;
-
-type McfResult = Result<(), (Span, Cow<'static, str>)>;
-
-pub fn is_min_const_fn(tcx: TyCtxt<'tcx>, def_id: DefId, body: &'a Body<'tcx>) -> McfResult {
- // Prevent const trait methods from being annotated as `stable`.
- if tcx.features().staged_api {
- let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
- if crate::const_eval::is_parent_const_impl_raw(tcx, hir_id) {
- return Err((body.span, "trait methods cannot be stable const fn".into()));
- }
- }
-
- let mut current = def_id;
- loop {
- let predicates = tcx.predicates_of(current);
- for (predicate, _) in predicates.predicates {
- match predicate.skip_binders() {
- ty::PredicateAtom::RegionOutlives(_)
- | ty::PredicateAtom::TypeOutlives(_)
- | ty::PredicateAtom::WellFormed(_)
- | ty::PredicateAtom::Projection(_)
- | ty::PredicateAtom::ConstEvaluatable(..)
- | ty::PredicateAtom::ConstEquate(..)
- | ty::PredicateAtom::TypeWellFormedFromEnv(..) => continue,
- ty::PredicateAtom::ObjectSafe(_) => {
- bug!("object safe predicate on function: {:#?}", predicate)
- }
- ty::PredicateAtom::ClosureKind(..) => {
- bug!("closure kind predicate on function: {:#?}", predicate)
- }
- ty::PredicateAtom::Subtype(_) => {
- bug!("subtype predicate on function: {:#?}", predicate)
- }
- ty::PredicateAtom::Trait(pred, constness) => {
- if Some(pred.def_id()) == tcx.lang_items().sized_trait() {
- continue;
- }
- match pred.self_ty().kind() {
- ty::Param(ref p) => {
- // Allow `T: ?const Trait`
- if constness == hir::Constness::NotConst
- && feature_allowed(tcx, def_id, sym::const_trait_bound_opt_out)
- {
- continue;
- }
-
- let generics = tcx.generics_of(current);
- let def = generics.type_param(p, tcx);
- let span = tcx.def_span(def.def_id);
- return Err((
- span,
- "trait bounds other than `Sized` \
- on const fn parameters are unstable"
- .into(),
- ));
- }
- // other kinds of bounds are either tautologies
- // or cause errors in other passes
- _ => continue,
- }
- }
- }
- }
- match predicates.parent {
- Some(parent) => current = parent,
- None => break,
- }
- }
-
- for local in &body.local_decls {
- check_ty(tcx, local.ty, local.source_info.span, def_id)?;
- }
- // impl trait is gone in MIR, so check the return type manually
- check_ty(
- tcx,
- tcx.fn_sig(def_id).output().skip_binder(),
- body.local_decls.iter().next().unwrap().source_info.span,
- def_id,
- )?;
-
- for bb in body.basic_blocks() {
- check_terminator(tcx, body, def_id, bb.terminator())?;
- for stmt in &bb.statements {
- check_statement(tcx, body, def_id, stmt)?;
- }
- }
- Ok(())
-}
-
-fn check_ty(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, span: Span, fn_def_id: DefId) -> McfResult {
- for arg in ty.walk() {
- let ty = match arg.unpack() {
- GenericArgKind::Type(ty) => ty,
-
- // No constraints on lifetimes or constants, except potentially
- // constants' types, but `walk` will get to them as well.
- GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => continue,
- };
-
- match ty.kind() {
- ty::Ref(_, _, hir::Mutability::Mut) => {
- if !feature_allowed(tcx, fn_def_id, sym::const_mut_refs) {
- return Err((span, "mutable references in const fn are unstable".into()));
- }
- }
- ty::Opaque(..) => return Err((span, "`impl Trait` in const fn is unstable".into())),
- ty::FnPtr(..) => {
- if !tcx.const_fn_is_allowed_fn_ptr(fn_def_id) {
- return Err((span, "function pointers in const fn are unstable".into()));
- }
- }
- ty::Dynamic(preds, _) => {
- for pred in preds.iter() {
- match pred.skip_binder() {
- ty::ExistentialPredicate::AutoTrait(_)
- | ty::ExistentialPredicate::Projection(_) => {
- return Err((
- span,
- "trait bounds other than `Sized` \
- on const fn parameters are unstable"
- .into(),
- ));
- }
- ty::ExistentialPredicate::Trait(trait_ref) => {
- if Some(trait_ref.def_id) != tcx.lang_items().sized_trait() {
- return Err((
- span,
- "trait bounds other than `Sized` \
- on const fn parameters are unstable"
- .into(),
- ));
- }
- }
- }
- }
- }
- _ => {}
- }
- }
- Ok(())
-}
-
-fn check_rvalue(
- tcx: TyCtxt<'tcx>,
- body: &Body<'tcx>,
- def_id: DefId,
- rvalue: &Rvalue<'tcx>,
- span: Span,
-) -> McfResult {
- match rvalue {
- Rvalue::ThreadLocalRef(_) => {
- Err((span, "cannot access thread local storage in const fn".into()))
- }
- Rvalue::Repeat(operand, _) | Rvalue::Use(operand) => {
- check_operand(tcx, operand, span, def_id, body)
- }
- Rvalue::Len(place)
- | Rvalue::Discriminant(place)
- | Rvalue::Ref(_, _, place)
- | Rvalue::AddressOf(_, place) => check_place(tcx, *place, span, def_id, body),
- Rvalue::Cast(CastKind::Misc, operand, cast_ty) => {
- use rustc_middle::ty::cast::CastTy;
- let cast_in = CastTy::from_ty(operand.ty(body, tcx)).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::FnPtr, CastTy::Int(_)) => {
- Err((span, "casting pointers to ints is unstable in const fn".into()))
- }
- _ => check_operand(tcx, operand, span, def_id, body),
- }
- }
- Rvalue::Cast(
- CastKind::Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer),
- operand,
- _,
- ) => check_operand(tcx, operand, span, def_id, body),
- Rvalue::Cast(
- CastKind::Pointer(
- PointerCast::UnsafeFnPointer
- | PointerCast::ClosureFnPointer(_)
- | PointerCast::ReifyFnPointer,
- ),
- _,
- _,
- ) => Err((span, "function pointer casts are not allowed in const fn".into())),
- Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), op, cast_ty) => {
- let pointee_ty = if let Some(deref_ty) = cast_ty.builtin_deref(true) {
- deref_ty.ty
- } else {
- // We cannot allow this for now.
- return Err((
- span,
- "unsizing casts are only allowed for references right now".into(),
- ));
- };
- let unsized_ty = tcx.struct_tail_erasing_lifetimes(pointee_ty, tcx.param_env(def_id));
- if let ty::Slice(_) | ty::Str = unsized_ty.kind() {
- check_operand(tcx, op, span, def_id, body)?;
- // Casting/coercing things to slices is fine.
- Ok(())
- } else {
- // We just can't allow trait objects until we have figured out trait method calls.
- Err((span, "unsizing casts are not allowed in const fn".into()))
- }
- }
- // binops are fine on integers
- Rvalue::BinaryOp(_, lhs, rhs) | Rvalue::CheckedBinaryOp(_, lhs, rhs) => {
- check_operand(tcx, lhs, span, def_id, body)?;
- check_operand(tcx, rhs, span, def_id, body)?;
- let ty = lhs.ty(body, tcx);
- if ty.is_integral() || ty.is_bool() || ty.is_char() {
- Ok(())
- } else {
- Err((span, "only int, `bool` and `char` operations are stable in const fn".into()))
- }
- }
- Rvalue::NullaryOp(NullOp::SizeOf, _) => Ok(()),
- Rvalue::NullaryOp(NullOp::Box, _) => {
- Err((span, "heap allocations are not allowed in const fn".into()))
- }
- Rvalue::UnaryOp(_, operand) => {
- let ty = operand.ty(body, tcx);
- if ty.is_integral() || ty.is_bool() {
- check_operand(tcx, operand, span, def_id, body)
- } else {
- Err((span, "only int and `bool` operations are stable in const fn".into()))
- }
- }
- Rvalue::Aggregate(_, operands) => {
- for operand in operands {
- check_operand(tcx, operand, span, def_id, body)?;
- }
- Ok(())
- }
- }
-}
-
-fn check_statement(
- tcx: TyCtxt<'tcx>,
- body: &Body<'tcx>,
- def_id: DefId,
- statement: &Statement<'tcx>,
-) -> McfResult {
- let span = statement.source_info.span;
- match &statement.kind {
- StatementKind::Assign(box (place, rval)) => {
- check_place(tcx, *place, span, def_id, body)?;
- check_rvalue(tcx, body, def_id, rval, span)
- }
-
- StatementKind::FakeRead(_, place) => check_place(tcx, **place, span, def_id, body),
-
- // just an assignment
- StatementKind::SetDiscriminant { place, .. } => {
- check_place(tcx, **place, span, def_id, body)
- }
-
- StatementKind::LlvmInlineAsm { .. } => {
- Err((span, "cannot use inline assembly in const fn".into()))
- }
-
- // These are all NOPs
- StatementKind::StorageLive(_)
- | StatementKind::StorageDead(_)
- | StatementKind::Retag { .. }
- | StatementKind::AscribeUserType(..)
- | StatementKind::Coverage(..)
- | StatementKind::Nop => Ok(()),
- }
-}
-
-fn check_operand(
- tcx: TyCtxt<'tcx>,
- operand: &Operand<'tcx>,
- span: Span,
- def_id: DefId,
- body: &Body<'tcx>,
-) -> McfResult {
- match operand {
- Operand::Move(place) | Operand::Copy(place) => check_place(tcx, *place, span, def_id, body),
- Operand::Constant(c) => match c.check_static_ptr(tcx) {
- Some(_) => Err((span, "cannot access `static` items in const fn".into())),
- None => Ok(()),
- },
- }
-}
-
-fn check_place(
- tcx: TyCtxt<'tcx>,
- place: Place<'tcx>,
- span: Span,
- def_id: DefId,
- body: &Body<'tcx>,
-) -> McfResult {
- let mut cursor = place.projection.as_ref();
- while let &[ref proj_base @ .., elem] = cursor {
- cursor = proj_base;
- match elem {
- ProjectionElem::Field(..) => {
- let base_ty = Place::ty_from(place.local, &proj_base, body, tcx).ty;
- if let Some(def) = base_ty.ty_adt_def() {
- // No union field accesses in `const fn`
- if def.is_union() {
- if !feature_allowed(tcx, def_id, sym::const_fn_union) {
- return Err((span, "accessing union fields is unstable".into()));
- }
- }
- }
- }
- ProjectionElem::ConstantIndex { .. }
- | ProjectionElem::Downcast(..)
- | ProjectionElem::Subslice { .. }
- | ProjectionElem::Deref
- | ProjectionElem::Index(_) => {}
- }
- }
-
- Ok(())
-}
-
-/// Returns `true` if the given feature gate is allowed within the function with the given `DefId`.
-fn feature_allowed(tcx: TyCtxt<'tcx>, def_id: DefId, feature_gate: Symbol) -> bool {
- // All features require that the corresponding gate be enabled,
- // even if the function has `#[allow_internal_unstable(the_gate)]`.
- if !tcx.features().enabled(feature_gate) {
- return false;
- }
-
- // If this crate is not using stability attributes, or this function is not claiming to be a
- // stable `const fn`, that is all that is required.
- if !tcx.features().staged_api || tcx.has_attr(def_id, sym::rustc_const_unstable) {
- return true;
- }
-
- // However, we cannot allow stable `const fn`s to use unstable features without an explicit
- // opt-in via `allow_internal_unstable`.
- super::check_consts::allow_internal_unstable(tcx, def_id, feature_gate)
-}
-
-/// Returns `true` if the given library feature gate is allowed within the function with the given `DefId`.
-pub fn lib_feature_allowed(tcx: TyCtxt<'tcx>, def_id: DefId, feature_gate: Symbol) -> bool {
- // All features require that the corresponding gate be enabled,
- // even if the function has `#[allow_internal_unstable(the_gate)]`.
- if !tcx.features().declared_lib_features.iter().any(|&(sym, _)| sym == feature_gate) {
- return false;
- }
-
- // If this crate is not using stability attributes, or this function is not claiming to be a
- // stable `const fn`, that is all that is required.
- if !tcx.features().staged_api || tcx.has_attr(def_id, sym::rustc_const_unstable) {
- return true;
- }
-
- // However, we cannot allow stable `const fn`s to use unstable features without an explicit
- // opt-in via `allow_internal_unstable`.
- super::check_consts::allow_internal_unstable(tcx, def_id, feature_gate)
-}
-
-fn check_terminator(
- tcx: TyCtxt<'tcx>,
- body: &'a Body<'tcx>,
- def_id: DefId,
- terminator: &Terminator<'tcx>,
-) -> McfResult {
- let span = terminator.source_info.span;
- match &terminator.kind {
- TerminatorKind::FalseEdge { .. }
- | TerminatorKind::FalseUnwind { .. }
- | TerminatorKind::Goto { .. }
- | TerminatorKind::Return
- | TerminatorKind::Resume
- | TerminatorKind::Unreachable => Ok(()),
-
- TerminatorKind::Drop { place, .. } => check_place(tcx, *place, span, def_id, body),
- TerminatorKind::DropAndReplace { place, value, .. } => {
- check_place(tcx, *place, span, def_id, body)?;
- check_operand(tcx, value, span, def_id, body)
- }
-
- TerminatorKind::SwitchInt { discr, switch_ty: _, values: _, targets: _ } => {
- check_operand(tcx, discr, span, def_id, body)
- }
-
- TerminatorKind::Abort => Err((span, "abort is not stable in const fn".into())),
- TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => {
- Err((span, "const fn generators are unstable".into()))
- }
-
- TerminatorKind::Call {
- func,
- args,
- from_hir_call: _,
- destination: _,
- cleanup: _,
- fn_span: _,
- } => {
- let fn_ty = func.ty(body, tcx);
- if let ty::FnDef(fn_def_id, _) = *fn_ty.kind() {
- // Allow unstable const if we opt in by using #[allow_internal_unstable]
- // on function or macro declaration.
- if !crate::const_eval::is_min_const_fn(tcx, fn_def_id)
- && !crate::const_eval::is_unstable_const_fn(tcx, fn_def_id)
- .map(|feature| {
- span.allows_unstable(feature)
- || lib_feature_allowed(tcx, def_id, feature)
- })
- .unwrap_or(false)
- {
- return Err((
- span,
- format!(
- "can only call other `const fn` within a `const fn`, \
- but `{:?}` is not stable as `const fn`",
- func,
- )
- .into(),
- ));
- }
-
- // HACK: This is to "unstabilize" the `transmute` intrinsic
- // within const fns. `transmute` is allowed in all other const contexts.
- // This won't really scale to more intrinsics or functions. Let's allow const
- // transmutes in const fn before we add more hacks to this.
- if tcx.fn_sig(fn_def_id).abi() == RustIntrinsic
- && tcx.item_name(fn_def_id) == sym::transmute
- && !feature_allowed(tcx, def_id, sym::const_fn_transmute)
- {
- return Err((
- span,
- "can only call `transmute` from const items, not `const fn`".into(),
- ));
- }
-
- check_operand(tcx, func, span, fn_def_id, body)?;
-
- for arg in args {
- check_operand(tcx, arg, span, fn_def_id, body)?;
- }
- Ok(())
- } else {
- Err((span, "can only call other const fns within const fn".into()))
- }
- }
-
- TerminatorKind::Assert { cond, expected: _, msg: _, target: _, cleanup: _ } => {
- check_operand(tcx, cond, span, def_id, body)
- }
-
- TerminatorKind::InlineAsm { .. } => {
- Err((span, "cannot use inline assembly in const fn".into()))
- }
- }
-}
#![feature(concat_idents)]
#![feature(crate_visibility_modifier)]
#![feature(drain_filter)]
+#![feature(in_band_lifetimes)]
#![feature(or_patterns)]
#![feature(rustc_private)]
#![feature(stmt_expr_attributes)]
use rustc_hir::{Body, Constness, FnDecl, GenericParamKind, HirId};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::lint::in_external_macro;
-use rustc_mir::transform::qualify_min_const_fn::is_min_const_fn;
+use crate::utils::qualify_min_const_fn::is_min_const_fn;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::Span;
use rustc_typeck::hir_ty_to_ty;
pub mod ptr;
pub mod sugg;
pub mod usage;
+pub mod qualify_min_const_fn;
pub use self::attrs::*;
pub use self::diagnostics::*;
--- /dev/null
+use rustc_hir as hir;
+use rustc_hir::def_id::DefId;
+use rustc_middle::mir::*;
+use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::{self, adjustment::PointerCast, Ty, TyCtxt};
+use rustc_span::symbol::{sym, Symbol};
+use rustc_span::Span;
+use rustc_target::spec::abi::Abi::RustIntrinsic;
+use std::borrow::Cow;
+
+type McfResult = Result<(), (Span, Cow<'static, str>)>;
+
+pub fn is_min_const_fn(tcx: TyCtxt<'tcx>, def_id: DefId, body: &'a Body<'tcx>) -> McfResult {
+ // Prevent const trait methods from being annotated as `stable`.
+ if tcx.features().staged_api {
+ let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
+ if rustc_mir::const_eval::is_parent_const_impl_raw(tcx, hir_id) {
+ return Err((body.span, "trait methods cannot be stable const fn".into()));
+ }
+ }
+
+ let mut current = def_id;
+ loop {
+ let predicates = tcx.predicates_of(current);
+ for (predicate, _) in predicates.predicates {
+ match predicate.skip_binders() {
+ ty::PredicateAtom::RegionOutlives(_)
+ | ty::PredicateAtom::TypeOutlives(_)
+ | ty::PredicateAtom::WellFormed(_)
+ | ty::PredicateAtom::Projection(_)
+ | ty::PredicateAtom::ConstEvaluatable(..)
+ | ty::PredicateAtom::ConstEquate(..)
+ | ty::PredicateAtom::TypeWellFormedFromEnv(..) => continue,
+ ty::PredicateAtom::ObjectSafe(_) => {
+ panic!("object safe predicate on function: {:#?}", predicate)
+ }
+ ty::PredicateAtom::ClosureKind(..) => {
+ panic!("closure kind predicate on function: {:#?}", predicate)
+ }
+ ty::PredicateAtom::Subtype(_) => {
+ panic!("subtype predicate on function: {:#?}", predicate)
+ }
+ ty::PredicateAtom::Trait(pred, constness) => {
+ if Some(pred.def_id()) == tcx.lang_items().sized_trait() {
+ continue;
+ }
+ match pred.self_ty().kind() {
+ ty::Param(ref p) => {
+ // Allow `T: ?const Trait`
+ if constness == hir::Constness::NotConst
+ && feature_allowed(tcx, def_id, sym::const_trait_bound_opt_out)
+ {
+ continue;
+ }
+
+ let generics = tcx.generics_of(current);
+ let def = generics.type_param(p, tcx);
+ let span = tcx.def_span(def.def_id);
+ return Err((
+ span,
+ "trait bounds other than `Sized` \
+ on const fn parameters are unstable"
+ .into(),
+ ));
+ }
+ // other kinds of bounds are either tautologies
+ // or cause errors in other passes
+ _ => continue,
+ }
+ }
+ }
+ }
+ match predicates.parent {
+ Some(parent) => current = parent,
+ None => break,
+ }
+ }
+
+ for local in &body.local_decls {
+ check_ty(tcx, local.ty, local.source_info.span, def_id)?;
+ }
+ // impl trait is gone in MIR, so check the return type manually
+ check_ty(
+ tcx,
+ tcx.fn_sig(def_id).output().skip_binder(),
+ body.local_decls.iter().next().unwrap().source_info.span,
+ def_id,
+ )?;
+
+ for bb in body.basic_blocks() {
+ check_terminator(tcx, body, def_id, bb.terminator())?;
+ for stmt in &bb.statements {
+ check_statement(tcx, body, def_id, stmt)?;
+ }
+ }
+ Ok(())
+}
+
+fn check_ty(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, span: Span, fn_def_id: DefId) -> McfResult {
+ for arg in ty.walk() {
+ let ty = match arg.unpack() {
+ GenericArgKind::Type(ty) => ty,
+
+ // No constraints on lifetimes or constants, except potentially
+ // constants' types, but `walk` will get to them as well.
+ GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => continue,
+ };
+
+ match ty.kind() {
+ ty::Ref(_, _, hir::Mutability::Mut) => {
+ if !feature_allowed(tcx, fn_def_id, sym::const_mut_refs) {
+ return Err((span, "mutable references in const fn are unstable".into()));
+ }
+ }
+ ty::Opaque(..) => return Err((span, "`impl Trait` in const fn is unstable".into())),
+ ty::FnPtr(..) => {
+ if !tcx.const_fn_is_allowed_fn_ptr(fn_def_id) {
+ return Err((span, "function pointers in const fn are unstable".into()));
+ }
+ }
+ ty::Dynamic(preds, _) => {
+ for pred in preds.iter() {
+ match pred.skip_binder() {
+ ty::ExistentialPredicate::AutoTrait(_)
+ | ty::ExistentialPredicate::Projection(_) => {
+ return Err((
+ span,
+ "trait bounds other than `Sized` \
+ on const fn parameters are unstable"
+ .into(),
+ ));
+ }
+ ty::ExistentialPredicate::Trait(trait_ref) => {
+ if Some(trait_ref.def_id) != tcx.lang_items().sized_trait() {
+ return Err((
+ span,
+ "trait bounds other than `Sized` \
+ on const fn parameters are unstable"
+ .into(),
+ ));
+ }
+ }
+ }
+ }
+ }
+ _ => {}
+ }
+ }
+ Ok(())
+}
+
+fn check_rvalue(
+ tcx: TyCtxt<'tcx>,
+ body: &Body<'tcx>,
+ def_id: DefId,
+ rvalue: &Rvalue<'tcx>,
+ span: Span,
+) -> McfResult {
+ match rvalue {
+ Rvalue::ThreadLocalRef(_) => {
+ Err((span, "cannot access thread local storage in const fn".into()))
+ }
+ Rvalue::Repeat(operand, _) | Rvalue::Use(operand) => {
+ check_operand(tcx, operand, span, def_id, body)
+ }
+ Rvalue::Len(place)
+ | Rvalue::Discriminant(place)
+ | Rvalue::Ref(_, _, place)
+ | Rvalue::AddressOf(_, place) => check_place(tcx, *place, span, def_id, body),
+ Rvalue::Cast(CastKind::Misc, operand, cast_ty) => {
+ use rustc_middle::ty::cast::CastTy;
+ let cast_in = CastTy::from_ty(operand.ty(body, tcx)).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::FnPtr, CastTy::Int(_)) => {
+ Err((span, "casting pointers to ints is unstable in const fn".into()))
+ }
+ _ => check_operand(tcx, operand, span, def_id, body),
+ }
+ }
+ Rvalue::Cast(
+ CastKind::Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer),
+ operand,
+ _,
+ ) => check_operand(tcx, operand, span, def_id, body),
+ Rvalue::Cast(
+ CastKind::Pointer(
+ PointerCast::UnsafeFnPointer
+ | PointerCast::ClosureFnPointer(_)
+ | PointerCast::ReifyFnPointer,
+ ),
+ _,
+ _,
+ ) => Err((span, "function pointer casts are not allowed in const fn".into())),
+ Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), op, cast_ty) => {
+ let pointee_ty = if let Some(deref_ty) = cast_ty.builtin_deref(true) {
+ deref_ty.ty
+ } else {
+ // We cannot allow this for now.
+ return Err((
+ span,
+ "unsizing casts are only allowed for references right now".into(),
+ ));
+ };
+ let unsized_ty = tcx.struct_tail_erasing_lifetimes(pointee_ty, tcx.param_env(def_id));
+ if let ty::Slice(_) | ty::Str = unsized_ty.kind() {
+ check_operand(tcx, op, span, def_id, body)?;
+ // Casting/coercing things to slices is fine.
+ Ok(())
+ } else {
+ // We just can't allow trait objects until we have figured out trait method calls.
+ Err((span, "unsizing casts are not allowed in const fn".into()))
+ }
+ }
+ // binops are fine on integers
+ Rvalue::BinaryOp(_, lhs, rhs) | Rvalue::CheckedBinaryOp(_, lhs, rhs) => {
+ check_operand(tcx, lhs, span, def_id, body)?;
+ check_operand(tcx, rhs, span, def_id, body)?;
+ let ty = lhs.ty(body, tcx);
+ if ty.is_integral() || ty.is_bool() || ty.is_char() {
+ Ok(())
+ } else {
+ Err((span, "only int, `bool` and `char` operations are stable in const fn".into()))
+ }
+ }
+ Rvalue::NullaryOp(NullOp::SizeOf, _) => Ok(()),
+ Rvalue::NullaryOp(NullOp::Box, _) => {
+ Err((span, "heap allocations are not allowed in const fn".into()))
+ }
+ Rvalue::UnaryOp(_, operand) => {
+ let ty = operand.ty(body, tcx);
+ if ty.is_integral() || ty.is_bool() {
+ check_operand(tcx, operand, span, def_id, body)
+ } else {
+ Err((span, "only int and `bool` operations are stable in const fn".into()))
+ }
+ }
+ Rvalue::Aggregate(_, operands) => {
+ for operand in operands {
+ check_operand(tcx, operand, span, def_id, body)?;
+ }
+ Ok(())
+ }
+ }
+}
+
+fn check_statement(
+ tcx: TyCtxt<'tcx>,
+ body: &Body<'tcx>,
+ def_id: DefId,
+ statement: &Statement<'tcx>,
+) -> McfResult {
+ let span = statement.source_info.span;
+ match &statement.kind {
+ StatementKind::Assign(box (place, rval)) => {
+ check_place(tcx, *place, span, def_id, body)?;
+ check_rvalue(tcx, body, def_id, rval, span)
+ }
+
+ StatementKind::FakeRead(_, place) => check_place(tcx, **place, span, def_id, body),
+
+ // just an assignment
+ StatementKind::SetDiscriminant { place, .. } => {
+ check_place(tcx, **place, span, def_id, body)
+ }
+
+ StatementKind::LlvmInlineAsm { .. } => {
+ Err((span, "cannot use inline assembly in const fn".into()))
+ }
+
+ // These are all NOPs
+ StatementKind::StorageLive(_)
+ | StatementKind::StorageDead(_)
+ | StatementKind::Retag { .. }
+ | StatementKind::AscribeUserType(..)
+ | StatementKind::Coverage(..)
+ | StatementKind::Nop => Ok(()),
+ }
+}
+
+fn check_operand(
+ tcx: TyCtxt<'tcx>,
+ operand: &Operand<'tcx>,
+ span: Span,
+ def_id: DefId,
+ body: &Body<'tcx>,
+) -> McfResult {
+ match operand {
+ Operand::Move(place) | Operand::Copy(place) => check_place(tcx, *place, span, def_id, body),
+ Operand::Constant(c) => match c.check_static_ptr(tcx) {
+ Some(_) => Err((span, "cannot access `static` items in const fn".into())),
+ None => Ok(()),
+ },
+ }
+}
+
+fn check_place(
+ tcx: TyCtxt<'tcx>,
+ place: Place<'tcx>,
+ span: Span,
+ def_id: DefId,
+ body: &Body<'tcx>,
+) -> McfResult {
+ let mut cursor = place.projection.as_ref();
+ while let &[ref proj_base @ .., elem] = cursor {
+ cursor = proj_base;
+ match elem {
+ ProjectionElem::Field(..) => {
+ let base_ty = Place::ty_from(place.local, &proj_base, body, tcx).ty;
+ if let Some(def) = base_ty.ty_adt_def() {
+ // No union field accesses in `const fn`
+ if def.is_union() {
+ if !feature_allowed(tcx, def_id, sym::const_fn_union) {
+ return Err((span, "accessing union fields is unstable".into()));
+ }
+ }
+ }
+ }
+ ProjectionElem::ConstantIndex { .. }
+ | ProjectionElem::Downcast(..)
+ | ProjectionElem::Subslice { .. }
+ | ProjectionElem::Deref
+ | ProjectionElem::Index(_) => {}
+ }
+ }
+
+ Ok(())
+}
+
+/// Returns `true` if the given feature gate is allowed within the function with the given `DefId`.
+fn feature_allowed(tcx: TyCtxt<'tcx>, def_id: DefId, feature_gate: Symbol) -> bool {
+ // All features require that the corresponding gate be enabled,
+ // even if the function has `#[allow_internal_unstable(the_gate)]`.
+ if !tcx.features().enabled(feature_gate) {
+ return false;
+ }
+
+ // If this crate is not using stability attributes, or this function is not claiming to be a
+ // stable `const fn`, that is all that is required.
+ if !tcx.features().staged_api || tcx.has_attr(def_id, sym::rustc_const_unstable) {
+ return true;
+ }
+
+ // However, we cannot allow stable `const fn`s to use unstable features without an explicit
+ // opt-in via `allow_internal_unstable`.
+ rustc_mir::transform::check_consts::allow_internal_unstable(tcx, def_id, feature_gate)
+}
+
+/// Returns `true` if the given library feature gate is allowed within the function with the given `DefId`.
+pub fn lib_feature_allowed(tcx: TyCtxt<'tcx>, def_id: DefId, feature_gate: Symbol) -> bool {
+ // All features require that the corresponding gate be enabled,
+ // even if the function has `#[allow_internal_unstable(the_gate)]`.
+ if !tcx.features().declared_lib_features.iter().any(|&(sym, _)| sym == feature_gate) {
+ return false;
+ }
+
+ // If this crate is not using stability attributes, or this function is not claiming to be a
+ // stable `const fn`, that is all that is required.
+ if !tcx.features().staged_api || tcx.has_attr(def_id, sym::rustc_const_unstable) {
+ return true;
+ }
+
+ // However, we cannot allow stable `const fn`s to use unstable features without an explicit
+ // opt-in via `allow_internal_unstable`.
+ rustc_mir::transform::check_consts::allow_internal_unstable(tcx, def_id, feature_gate)
+}
+
+fn check_terminator(
+ tcx: TyCtxt<'tcx>,
+ body: &'a Body<'tcx>,
+ def_id: DefId,
+ terminator: &Terminator<'tcx>,
+) -> McfResult {
+ let span = terminator.source_info.span;
+ match &terminator.kind {
+ TerminatorKind::FalseEdge { .. }
+ | TerminatorKind::FalseUnwind { .. }
+ | TerminatorKind::Goto { .. }
+ | TerminatorKind::Return
+ | TerminatorKind::Resume
+ | TerminatorKind::Unreachable => Ok(()),
+
+ TerminatorKind::Drop { place, .. } => check_place(tcx, *place, span, def_id, body),
+ TerminatorKind::DropAndReplace { place, value, .. } => {
+ check_place(tcx, *place, span, def_id, body)?;
+ check_operand(tcx, value, span, def_id, body)
+ }
+
+ TerminatorKind::SwitchInt { discr, switch_ty: _, values: _, targets: _ } => {
+ check_operand(tcx, discr, span, def_id, body)
+ }
+
+ TerminatorKind::Abort => Err((span, "abort is not stable in const fn".into())),
+ TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => {
+ Err((span, "const fn generators are unstable".into()))
+ }
+
+ TerminatorKind::Call {
+ func,
+ args,
+ from_hir_call: _,
+ destination: _,
+ cleanup: _,
+ fn_span: _,
+ } => {
+ let fn_ty = func.ty(body, tcx);
+ if let ty::FnDef(fn_def_id, _) = *fn_ty.kind() {
+ // Allow unstable const if we opt in by using #[allow_internal_unstable]
+ // on function or macro declaration.
+ if !rustc_mir::const_eval::is_min_const_fn(tcx, fn_def_id)
+ && !rustc_mir::const_eval::is_unstable_const_fn(tcx, fn_def_id)
+ .map(|feature| {
+ span.allows_unstable(feature)
+ || lib_feature_allowed(tcx, def_id, feature)
+ })
+ .unwrap_or(false)
+ {
+ return Err((
+ span,
+ format!(
+ "can only call other `const fn` within a `const fn`, \
+ but `{:?}` is not stable as `const fn`",
+ func,
+ )
+ .into(),
+ ));
+ }
+
+ // HACK: This is to "unstabilize" the `transmute` intrinsic
+ // within const fns. `transmute` is allowed in all other const contexts.
+ // This won't really scale to more intrinsics or functions. Let's allow const
+ // transmutes in const fn before we add more hacks to this.
+ if tcx.fn_sig(fn_def_id).abi() == RustIntrinsic
+ && tcx.item_name(fn_def_id) == sym::transmute
+ && !feature_allowed(tcx, def_id, sym::const_fn_transmute)
+ {
+ return Err((
+ span,
+ "can only call `transmute` from const items, not `const fn`".into(),
+ ));
+ }
+
+ check_operand(tcx, func, span, fn_def_id, body)?;
+
+ for arg in args {
+ check_operand(tcx, arg, span, fn_def_id, body)?;
+ }
+ Ok(())
+ } else {
+ Err((span, "can only call other const fns within const fn".into()))
+ }
+ }
+
+ TerminatorKind::Assert { cond, expected: _, msg: _, target: _, cleanup: _ } => {
+ check_operand(tcx, cond, span, def_id, body)
+ }
+
+ TerminatorKind::InlineAsm { .. } => {
+ Err((span, "cannot use inline assembly in const fn".into()))
+ }
+ }
+}
projects / rust.git / commitdiff