bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Auto merge of #88328 - fee1-dead:not-quite-const, r=oli-obk

Browse source 
Introduce `~const`

 - [x] Removed `?const` and change uses of `?const`
 - [x] Added `~const` to the AST. It is gated behind const_trait_impl.
 - [x] Validate `~const` in ast_validation.
 - [x] Update UI Tests
 - [x] Add enum `BoundConstness` (With variants `NotConst` and
 `ConstIfConst` allowing future extensions)
 - [x] Adjust trait selection and pre-existing code to use `BoundConstness`.
 - [ ] Optional steps for this PR
      - [x] Fix #88155
      - [x] ~~Do something with constness bounds in chalk~~ Must be done to rust-lang/chalk (just tried to refactor, there are a lot of errors to resolve :( )
      - [ ] Adjust Error messages for `~const` bounds that can't be satisfied.

r? `@oli-obk`
This commit is contained in:
bors 2021-08-27 21:35:08 +00:00
commit ac50a53359
79 changed files with 501 additions and 545 deletions
Download patch file Download diff file Expand all files Collapse all files

6
compiler/rustc_ast/src/ast.rs
View file

@ -284,7 +284,7 @@ impl ParenthesizedArgs {
pub use crate::node_id::{NodeId, CRATE_NODE_ID, DUMMY_NODE_ID};
/// A modifier on a bound, e.g., `?Sized` or `?const Trait`.
/// A modifier on a bound, e.g., `?Sized` or `~const Trait`.
///
/// Negative bounds should also be handled here.
#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug)]
@ -295,10 +295,10 @@ pub enum TraitBoundModifier {
/// `?Trait`
Maybe,
/// `?const Trait`
/// `~const Trait`
MaybeConst,
/// `?const ?Trait`
/// `~const ?Trait`
//
// This parses but will be rejected during AST validation.
MaybeConstMaybe,

2
compiler/rustc_ast_lowering/src/lib.rs
View file

@ -1414,7 +1414,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
ref ty,
TraitBoundModifier::None | TraitBoundModifier::MaybeConst,
) => Some(this.lower_poly_trait_ref(ty, itctx.reborrow())),
// `?const ?Bound` will cause an error during AST validation
// `~const ?Bound` will cause an error during AST validation
// anyways, so treat it like `?Bound` as compilation proceeds.
GenericBound::Trait(
_,

141
compiler/rustc_ast_passes/src/ast_validation.rs
View file

@ -33,24 +33,6 @@ enum SelfSemantic {
No,
}
/// A syntactic context that disallows certain kinds of bounds (e.g., `?Trait` or `?const Trait`).
#[derive(Clone, Copy)]
enum BoundContext {
ImplTrait,
TraitBounds,
TraitObject,
}
impl BoundContext {
fn description(&self) -> &'static str {
match self {
Self::ImplTrait => "`impl Trait`",
Self::TraitBounds => "supertraits",
Self::TraitObject => "trait objects",
}
}
}
struct AstValidator<'a> {
session: &'a Session,
@ -60,6 +42,8 @@ struct AstValidator<'a> {
/// Are we inside a trait impl?
in_trait_impl: bool,
in_const_trait_impl: bool,
has_proc_macro_decls: bool,
/// Used to ban nested `impl Trait`, e.g., `impl Into<impl Debug>`.
@ -67,11 +51,7 @@ struct AstValidator<'a> {
/// e.g., `impl Iterator<Item = impl Debug>`.
outer_impl_trait: Option<Span>,
/// Keeps track of the `BoundContext` as we recurse.
///
/// This is used to forbid `?const Trait` bounds in, e.g.,
/// `impl Iterator<Item = Box<dyn ?const Trait>`.
bound_context: Option<BoundContext>,
is_tilde_const_allowed: bool,
/// Used to ban `impl Trait` in path projections like `<impl Iterator>::Item`
/// or `Foo::Bar<impl Trait>`
@ -88,10 +68,18 @@ struct AstValidator<'a> {
}
impl<'a> AstValidator<'a> {
fn with_in_trait_impl(&mut self, is_in: bool, f: impl FnOnce(&mut Self)) {
fn with_in_trait_impl(
&mut self,
is_in: bool,
constness: Option<Const>,
f: impl FnOnce(&mut Self),
) {
let old = mem::replace(&mut self.in_trait_impl, is_in);
let old_const =
mem::replace(&mut self.in_const_trait_impl, matches!(constness, Some(Const::Yes(_))));
f(self);
self.in_trait_impl = old;
self.in_const_trait_impl = old_const;
}
fn with_banned_impl_trait(&mut self, f: impl FnOnce(&mut Self)) {
@ -100,6 +88,18 @@ impl<'a> AstValidator<'a> {
self.is_impl_trait_banned = old;
}
fn with_tilde_const_allowed(&mut self, f: impl FnOnce(&mut Self)) {
let old = mem::replace(&mut self.is_tilde_const_allowed, true);
f(self);
self.is_tilde_const_allowed = old;
}
fn with_banned_tilde_const(&mut self, f: impl FnOnce(&mut Self)) {
let old = mem::replace(&mut self.is_tilde_const_allowed, false);
f(self);
self.is_tilde_const_allowed = old;
}
fn with_let_allowed(&mut self, allowed: bool, f: impl FnOnce(&mut Self, bool)) {
let old = mem::replace(&mut self.is_let_allowed, allowed);
f(self, old);
@ -130,19 +130,13 @@ impl<'a> AstValidator<'a> {
fn with_impl_trait(&mut self, outer: Option<Span>, f: impl FnOnce(&mut Self)) {
let old = mem::replace(&mut self.outer_impl_trait, outer);
if outer.is_some() {
self.with_bound_context(BoundContext::ImplTrait, |this| f(this));
self.with_banned_tilde_const(f);
} else {
f(self)
f(self);
}
self.outer_impl_trait = old;
}
fn with_bound_context(&mut self, ctx: BoundContext, f: impl FnOnce(&mut Self)) {
let old = self.bound_context.replace(ctx);
f(self);
self.bound_context = old;
}
fn visit_assoc_ty_constraint_from_generic_args(&mut self, constraint: &'a AssocTyConstraint) {
match constraint.kind {
AssocTyConstraintKind::Equality { .. } => {}
@ -164,9 +158,7 @@ impl<'a> AstValidator<'a> {
TyKind::ImplTrait(..) => {
self.with_impl_trait(Some(t.span), |this| visit::walk_ty(this, t))
}
TyKind::TraitObject(..) => {
self.with_bound_context(BoundContext::TraitObject, |this| visit::walk_ty(this, t));
}
TyKind::TraitObject(..) => self.with_banned_tilde_const(|this| visit::walk_ty(this, t)),
TyKind::Path(ref qself, ref path) => {
// We allow these:
// - `Option<impl Trait>`
@ -1083,13 +1075,13 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
unsafety,
polarity,
defaultness: _,
constness: _,
generics: _,
constness,
ref generics,
of_trait: Some(ref t),
ref self_ty,
items: _,
ref items,
}) => {
self.with_in_trait_impl(true, |this| {
self.with_in_trait_impl(true, Some(constness), |this| {
this.invalid_visibility(&item.vis, None);
if let TyKind::Err = self_ty.kind {
this.err_handler()
@ -1112,7 +1104,17 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
.emit();
}
visit::walk_item(this, item);
this.visit_vis(&item.vis);
this.visit_ident(item.ident);
if let Const::Yes(_) = constness {
this.with_tilde_const_allowed(|this| this.visit_generics(generics));
} else {
this.visit_generics(generics);
}
this.visit_trait_ref(t);
this.visit_ty(self_ty);
walk_list!(this, visit_assoc_item, items, AssocCtxt::Impl);
});
return; // Avoid visiting again.
}
@ -1157,13 +1159,24 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
.emit();
}
}
ItemKind::Fn(box FnKind(def, _, _, ref body)) => {
ItemKind::Fn(box FnKind(def, ref sig, ref generics, ref body)) => {
self.check_defaultness(item.span, def);
if body.is_none() {
let msg = "free function without a body";
self.error_item_without_body(item.span, "function", msg, " { <body> }");
}
self.visit_vis(&item.vis);
self.visit_ident(item.ident);
if let Const::Yes(_) = sig.header.constness {
self.with_tilde_const_allowed(|this| this.visit_generics(generics));
} else {
self.visit_generics(generics);
}
let kind = FnKind::Fn(FnCtxt::Free, item.ident, sig, &item.vis, body.as_deref());
self.visit_fn(kind, item.span, item.id);
walk_list!(self, visit_attribute, &item.attrs);
return; // Avoid visiting again.
}
ItemKind::ForeignMod(ForeignMod { unsafety, .. }) => {
let old_item = mem::replace(&mut self.extern_mod, Some(item));
@ -1206,9 +1219,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
self.visit_vis(&item.vis);
self.visit_ident(item.ident);
self.visit_generics(generics);
self.with_bound_context(BoundContext::TraitBounds, |this| {
walk_list!(this, visit_param_bound, bounds);
});
self.with_banned_tilde_const(|this| walk_list!(this, visit_param_bound, bounds));
walk_list!(self, visit_assoc_item, trait_items, AssocCtxt::Trait);
walk_list!(self, visit_attribute, &item.attrs);
return;
@ -1281,7 +1292,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
_ => {}
}
visit::walk_item(self, item)
visit::walk_item(self, item);
}
fn visit_foreign_item(&mut self, fi: &'a ForeignItem) {
@ -1428,15 +1439,17 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
fn visit_param_bound(&mut self, bound: &'a GenericBound) {
match bound {
GenericBound::Trait(_, TraitBoundModifier::MaybeConst) => {
if let Some(ctx) = self.bound_context {
let msg = format!("`?const` is not permitted in {}", ctx.description());
self.err_handler().span_err(bound.span(), &msg);
if !self.is_tilde_const_allowed {
self.err_handler()
.struct_span_err(bound.span(), "`~const` is not allowed here")
.note("only allowed on bounds on traits' associated types, const fns, const impls and its associated functions")
.emit();
}
}
GenericBound::Trait(_, TraitBoundModifier::MaybeConstMaybe) => {
self.err_handler()
.span_err(bound.span(), "`?const` and `?` are mutually exclusive");
.span_err(bound.span(), "`~const` and `?` are mutually exclusive");
}
_ => {}
@ -1589,7 +1602,32 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
self.check_item_named(item.ident, "const");
}
self.with_in_trait_impl(false, |this| visit::walk_assoc_item(this, item, ctxt));
match item.kind {
AssocItemKind::TyAlias(box TyAliasKind(_, ref generics, ref bounds, ref ty))
if ctxt == AssocCtxt::Trait =>
{
self.visit_vis(&item.vis);
self.visit_ident(item.ident);
walk_list!(self, visit_attribute, &item.attrs);
self.with_tilde_const_allowed(|this| {
this.visit_generics(generics);
walk_list!(this, visit_param_bound, bounds);
});
walk_list!(self, visit_ty, ty);
}
AssocItemKind::Fn(box FnKind(_, ref sig, ref generics, ref body))
if self.in_const_trait_impl =>
{
self.visit_vis(&item.vis);
self.visit_ident(item.ident);
self.with_tilde_const_allowed(|this| this.visit_generics(generics));
let kind =
FnKind::Fn(FnCtxt::Assoc(ctxt), item.ident, sig, &item.vis, body.as_deref());
self.visit_fn(kind, item.span, item.id);
}
_ => self
.with_in_trait_impl(false, None, |this| visit::walk_assoc_item(this, item, ctxt)),
}
}
}
@ -1683,9 +1721,10 @@ pub fn check_crate(session: &Session, krate: &Crate, lints: &mut LintBuffer) ->
session,
extern_mod: None,
in_trait_impl: false,
in_const_trait_impl: false,
has_proc_macro_decls: false,
outer_impl_trait: None,
bound_context: None,
is_tilde_const_allowed: false,
is_impl_trait_banned: false,
is_assoc_ty_bound_banned: false,
is_let_allowed: false,

1
compiler/rustc_ast_passes/src/feature_gate.rs
View file

@ -656,7 +656,6 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
gate_all!(more_qualified_paths, "usage of qualified paths in this context is experimental");
gate_all!(generators, "yield syntax is experimental");
gate_all!(raw_ref_op, "raw address of syntax is experimental");
gate_all!(const_trait_bound_opt_out, "`?const` on trait bounds is experimental");
gate_all!(const_trait_impl, "const trait impls are experimental");
gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
gate_all!(inline_const, "inline-const is experimental");

3
compiler/rustc_feature/src/active.rs
View file

@ -515,9 +515,6 @@ declare_features! (
/// Allows `impl const Trait for T` syntax.
(active, const_trait_impl, "1.42.0", Some(67792), None),
/// Allows `T: ?const Trait` syntax in bounds.
(incomplete, const_trait_bound_opt_out, "1.42.0", Some(67794), None),
/// Allows the use of `no_sanitize` attribute.
(active, no_sanitize, "1.42.0", Some(39699), None),

3
compiler/rustc_feature/src/removed.rs
View file

@ -123,6 +123,9 @@ declare_features! (
/// Allows overlapping impls of marker traits.
(removed, overlapping_marker_traits, "1.42.0", Some(29864), None,
Some("removed in favor of `#![feature(marker_trait_attr)]`")),
/// Allows `T: ?const Trait` syntax in bounds.
(removed, const_trait_bound_opt_out, "1.42.0", Some(67794), None,
Some("Removed in favor of `~const` bound in #![feature(const_trait_impl)]")),
/// Allows `#[no_debug]`.
(removed, no_debug, "1.43.0", Some(29721), None, Some("removed due to lack of demand")),
/// Allows comparing raw pointers during const eval.

3
compiler/rustc_middle/src/traits/mod.rs
View file

@ -17,7 +17,6 @@ use rustc_data_structures::sync::Lrc;
use rustc_errors::{Applicability, DiagnosticBuilder};
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::Constness;
use rustc_span::symbol::Symbol;
use rustc_span::{Span, DUMMY_SP};
use smallvec::SmallVec;
@ -497,7 +496,7 @@ pub enum ImplSource<'tcx, N> {
/// for some type parameter. The `Vec<N>` represents the
/// obligations incurred from normalizing the where-clause (if
/// any).
Param(Vec<N>, Constness),
Param(Vec<N>, ty::BoundConstness),
/// Virtual calls through an object.
Object(ImplSourceObjectData<'tcx, N>),

4
compiler/rustc_middle/src/ty/error.rs
View file

@ -33,7 +33,7 @@ impl<T> ExpectedFound<T> {
#[derive(Clone, Debug, TypeFoldable)]
pub enum TypeError<'tcx> {
Mismatch,
ConstnessMismatch(ExpectedFound<hir::Constness>),
ConstnessMismatch(ExpectedFound<ty::BoundConstness>),
UnsafetyMismatch(ExpectedFound<hir::Unsafety>),
AbiMismatch(ExpectedFound<abi::Abi>),
Mutability,
@ -102,7 +102,7 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
CyclicConst(_) => write!(f, "encountered a self-referencing constant"),
Mismatch => write!(f, "types differ"),
ConstnessMismatch(values) => {
write!(f, "expected {} fn, found {} fn", values.expected, values.found)
write!(f, "expected {} bound, found {} bound", values.expected, values.found)
}
UnsafetyMismatch(values) => {
write!(f, "expected {} fn, found {} fn", values.expected, values.found)

40
compiler/rustc_middle/src/ty/mod.rs
View file

@ -37,7 +37,7 @@ use rustc_data_structures::tagged_ptr::CopyTaggedPtr;
use rustc_hir as hir;
use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LocalDefIdMap, CRATE_DEF_INDEX};
use rustc_hir::{Constness, Node};
use rustc_hir::Node;
use rustc_macros::HashStable;
use rustc_span::symbol::{kw, Ident, Symbol};
use rustc_span::Span;
@ -181,6 +181,25 @@ pub enum Visibility {
Invisible,
}
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)]
pub enum BoundConstness {
/// `T: Trait`
NotConst,
/// `T: ~const Trait`
///
/// Requires resolving to const only when we are in a const context.
ConstIfConst,
}
impl fmt::Display for BoundConstness {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::NotConst => f.write_str("normal"),
Self::ConstIfConst => f.write_str("`~const`"),
}
}
}
#[derive(
Clone,
Debug,
@ -457,10 +476,6 @@ pub enum PredicateKind<'tcx> {
/// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
/// the `Self` type of the trait reference and `A`, `B`, and `C`
/// would be the type parameters.
///
/// A trait predicate will have `Constness::Const` if it originates
/// from a bound on a `const fn` without the `?const` opt-out (e.g.,
/// `const fn foobar<Foo: Bar>() {}`).
Trait(TraitPredicate<'tcx>),
/// `where 'a: 'b`
@ -632,10 +647,7 @@ impl<'tcx> Predicate<'tcx> {
pub struct TraitPredicate<'tcx> {
pub trait_ref: TraitRef<'tcx>,
/// A trait predicate will have `Constness::Const` if it originates
/// from a bound on a `const fn` without the `?const` opt-out (e.g.,
/// `const fn foobar<Foo: Bar>() {}`).
pub constness: hir::Constness,
pub constness: BoundConstness,
}
pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
@ -1304,7 +1316,7 @@ impl<'tcx> ParamEnv<'tcx> {
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable)]
pub struct ConstnessAnd<T> {
pub constness: Constness,
pub constness: BoundConstness,
pub value: T,
}
@ -1312,18 +1324,18 @@ pub struct ConstnessAnd<T> {
// the constness of trait bounds is being propagated correctly.
pub trait WithConstness: Sized {
#[inline]
fn with_constness(self, constness: Constness) -> ConstnessAnd<Self> {
fn with_constness(self, constness: BoundConstness) -> ConstnessAnd<Self> {
ConstnessAnd { constness, value: self }
}
#[inline]
fn with_const(self) -> ConstnessAnd<Self> {
self.with_constness(Constness::Const)
fn with_const_if_const(self) -> ConstnessAnd<Self> {
self.with_constness(BoundConstness::ConstIfConst)
}
#[inline]
fn without_const(self) -> ConstnessAnd<Self> {
self.with_constness(Constness::NotConst)
self.with_constness(BoundConstness::NotConst)
}
}

8
compiler/rustc_middle/src/ty/relate.rs
View file

@ -200,12 +200,12 @@ impl<'tcx> Relate<'tcx> for ty::FnSig<'tcx> {
}
}
impl<'tcx> Relate<'tcx> for ast::Constness {
impl<'tcx> Relate<'tcx> for ty::BoundConstness {
fn relate<R: TypeRelation<'tcx>>(
relation: &mut R,
a: ast::Constness,
b: ast::Constness,
) -> RelateResult<'tcx, ast::Constness> {
a: ty::BoundConstness,
b: ty::BoundConstness,
) -> RelateResult<'tcx, ty::BoundConstness> {
if a != b {
Err(TypeError::ConstnessMismatch(expected_found(relation, a, b)))
} else {

6
compiler/rustc_middle/src/ty/structural_impls.rs
View file

@ -8,7 +8,6 @@ use crate::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
use crate::ty::print::{with_no_trimmed_paths, FmtPrinter, Printer};
use crate::ty::{self, InferConst, Lift, Ty, TyCtxt};
use rustc_data_structures::functor::IdFunctor;
use rustc_hir as hir;
use rustc_hir::def::Namespace;
use rustc_hir::def_id::CRATE_DEF_INDEX;
use rustc_index::vec::{Idx, IndexVec};
@ -155,8 +154,8 @@ impl fmt::Debug for ty::ParamConst {
impl fmt::Debug for ty::TraitPredicate<'tcx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if let hir::Constness::Const = self.constness {
write!(f, "const ")?;
if let ty::BoundConstness::ConstIfConst = self.constness {
write!(f, "~const ")?;
}
write!(f, "TraitPredicate({:?})", self.trait_ref)
}
@ -241,6 +240,7 @@ TrivialTypeFoldableAndLiftImpls! {
crate::traits::Reveal,
crate::ty::adjustment::AutoBorrowMutability,
crate::ty::AdtKind,
crate::ty::BoundConstness,
// Including `BoundRegionKind` is a *bit* dubious, but direct
// references to bound region appear in `ty::Error`, and aren't
// really meant to be folded. In general, we can only fold a fully

2
compiler/rustc_middle/src/ty/sty.rs
View file

@ -878,7 +878,7 @@ impl<'tcx> PolyTraitRef<'tcx> {
pub fn to_poly_trait_predicate(&self) -> ty::PolyTraitPredicate<'tcx> {
self.map_bound(|trait_ref| ty::TraitPredicate {
trait_ref,
constness: hir::Constness::NotConst,
constness: ty::BoundConstness::NotConst,
})
}
}

3
compiler/rustc_mir/src/borrow_check/type_check/canonical.rs
View file

@ -1,6 +1,5 @@
use std::fmt;
use rustc_hir as hir;
use rustc_infer::infer::canonical::Canonical;
use rustc_infer::traits::query::NoSolution;
use rustc_middle::mir::ConstraintCategory;
@ -88,7 +87,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
self.prove_predicates(
Some(ty::PredicateKind::Trait(ty::TraitPredicate {
trait_ref,
constness: hir::Constness::NotConst,
constness: ty::BoundConstness::NotConst,
})),
locations,
category,

87
compiler/rustc_mir/src/transform/check_consts/check.rs
View file

@ -805,6 +805,8 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
}
};
let mut nonconst_call_permission = false;
// Attempting to call a trait method?
if let Some(trait_id) = tcx.trait_of_item(callee) {
trace!("attempting to call a trait method");
@ -819,23 +821,54 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
param_env,
Binder::dummy(TraitPredicate {
trait_ref,
constness: hir::Constness::Const,
constness: ty::BoundConstness::ConstIfConst,
}),
);
let implsrc = tcx.infer_ctxt().enter(|infcx| {
let mut selcx = SelectionContext::new(&infcx);
selcx.select(&obligation).unwrap()
let mut selcx =
SelectionContext::with_constness(&infcx, hir::Constness::Const);
selcx.select(&obligation)
});
// If the method is provided via a where-clause that does not use the `?const`
// opt-out, the call is allowed.
if let Some(ImplSource::Param(_, hir::Constness::Const)) = implsrc {
debug!(
"const_trait_impl: provided {:?} via where-clause in {:?}",
trait_ref, param_env
);
return;
match implsrc {
Ok(Some(ImplSource::Param(_, ty::BoundConstness::ConstIfConst))) => {
debug!(
"const_trait_impl: provided {:?} via where-clause in {:?}",
trait_ref, param_env
);
return;
}
Ok(Some(ImplSource::UserDefined(data))) => {
let callee_name = tcx.item_name(callee);
if let Some(&did) = tcx
.associated_item_def_ids(data.impl_def_id)
.iter()
.find(|did| tcx.item_name(**did) == callee_name)
{
callee = did;
}
}
_ => {
if !tcx.is_const_fn_raw(callee) {
// At this point, it is only legal when the caller is marked with
// #[default_method_body_is_const], and the callee is in the same
// trait.
let callee_trait = tcx.trait_of_item(callee);
if callee_trait.is_some() {
if tcx.has_attr(caller, sym::default_method_body_is_const) {
if tcx.trait_of_item(caller) == callee_trait {
nonconst_call_permission = true;
}
}
}
if !nonconst_call_permission {
self.check_op(ops::FnCallNonConst);
return;
}
}
}
}
// Resolve a trait method call to its concrete implementation, which may be in a
@ -875,34 +908,16 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
let is_intrinsic = tcx.fn_sig(callee).abi() == RustIntrinsic;
if !tcx.is_const_fn_raw(callee) {
let mut permitted = false;
let callee_trait = tcx.trait_of_item(callee);
if let Some(trait_id) = callee_trait {
if tcx.has_attr(caller, sym::default_method_body_is_const) {
// permit call to non-const fn when caller has default_method_body_is_const..
if tcx.trait_of_item(caller) == callee_trait {
// ..and caller and callee are in the same trait.
permitted = true;
}
}
if !permitted {
// if trait's impls are all const, permit the call.
let mut const_impls = true;
tcx.for_each_relevant_impl(trait_id, substs.type_at(0), |imp| {
if const_impls {
if let hir::Constness::NotConst = tcx.impl_constness(imp) {
const_impls = false;
}
}
});
if const_impls {
permitted = true;
}
if tcx.trait_of_item(callee).is_some() {
if tcx.has_attr(callee, sym::default_method_body_is_const) {
// To get to here we must have already found a const impl for the
// trait, but for it to still be non-const can be that the impl is
// using default method bodies.
nonconst_call_permission = true;
}
}
if !permitted {
if !nonconst_call_permission {
self.check_op(ops::FnCallNonConst);
return;
}

46
compiler/rustc_parse/src/parser/ty.rs
View file

@ -11,12 +11,12 @@ use rustc_errors::{pluralize, struct_span_err, Applicability, PResult};
use rustc_span::source_map::Span;
use rustc_span::symbol::{kw, sym};
/// Any `?` or `?const` modifiers that appear at the start of a bound.
/// Any `?` or `~const` modifiers that appear at the start of a bound.
struct BoundModifiers {
/// `?Trait`.
maybe: Option<Span>,
/// `?const Trait`.
/// `~const Trait`.
maybe_const: Option<Span>,
}
@ -609,6 +609,7 @@ impl<'a> Parser<'a> {
|| self.check_lifetime()
|| self.check(&token::Not) // Used for error reporting only.
|| self.check(&token::Question)
|| self.check(&token::Tilde)
|| self.check_keyword(kw::For)
|| self.check(&token::OpenDelim(token::Paren))
}
@ -655,7 +656,7 @@ impl<'a> Parser<'a> {
let inner_lo = self.token.span;
let is_negative = self.eat(&token::Not);
let modifiers = self.parse_ty_bound_modifiers();
let modifiers = self.parse_ty_bound_modifiers()?;
let bound = if self.token.is_lifetime() {
self.error_lt_bound_with_modifiers(modifiers);
self.parse_generic_lt_bound(lo, inner_lo, has_parens)?
@ -690,7 +691,7 @@ impl<'a> Parser<'a> {
if let Some(span) = modifiers.maybe_const {
self.struct_span_err(
span,
"`?const` may only modify trait bounds, not lifetime bounds",
"`~const` may only modify trait bounds, not lifetime bounds",
)
.emit();
}
@ -721,34 +722,27 @@ impl<'a> Parser<'a> {
Ok(())
}
/// Parses the modifiers that may precede a trait in a bound, e.g. `?Trait` or `?const Trait`.
/// Parses the modifiers that may precede a trait in a bound, e.g. `?Trait` or `~const Trait`.
///
/// If no modifiers are present, this does not consume any tokens.
///
/// ```
/// TY_BOUND_MODIFIERS = "?" ["const" ["?"]]
/// TY_BOUND_MODIFIERS = ["~const"] ["?"]
/// ```
fn parse_ty_bound_modifiers(&mut self) -> BoundModifiers {
if !self.eat(&token::Question) {
return BoundModifiers { maybe: None, maybe_const: None };
}
fn parse_ty_bound_modifiers(&mut self) -> PResult<'a, BoundModifiers> {
let maybe_const = if self.eat(&token::Tilde) {
let tilde = self.prev_token.span;
self.expect_keyword(kw::Const)?;
let span = tilde.to(self.prev_token.span);
self.sess.gated_spans.gate(sym::const_trait_impl, span);
Some(span)
} else {
None
};
// `? ...`
let first_question = self.prev_token.span;
if !self.eat_keyword(kw::Const) {
return BoundModifiers { maybe: Some(first_question), maybe_const: None };
}
let maybe = if self.eat(&token::Question) { Some(self.prev_token.span) } else { None };
// `?const ...`
let maybe_const = first_question.to(self.prev_token.span);
self.sess.gated_spans.gate(sym::const_trait_bound_opt_out, maybe_const);
if !self.eat(&token::Question) {
return BoundModifiers { maybe: None, maybe_const: Some(maybe_const) };
}
// `?const ? ...`
let second_question = self.prev_token.span;
BoundModifiers { maybe: Some(second_question), maybe_const: Some(maybe_const) }
Ok(BoundModifiers { maybe, maybe_const })
}
/// Parses a type bound according to:
@ -757,7 +751,7 @@ impl<'a> Parser<'a> {
/// TY_BOUND_NOPAREN = [TY_BOUND_MODIFIERS] [for<LT_PARAM_DEFS>] SIMPLE_PATH
/// ```
///
/// For example, this grammar accepts `?const ?for<'a: 'b> m::Trait<'a>`.
/// For example, this grammar accepts `~const ?for<'a: 'b> m::Trait<'a>`.
fn parse_generic_ty_bound(
&mut self,
lo: Span,

2
compiler/rustc_trait_selection/src/traits/auto_trait.rs
View file

@ -285,7 +285,7 @@ impl AutoTraitFinder<'tcx> {
def_id: trait_did,
substs: infcx.tcx.mk_substs_trait(ty, &[]),
},
constness: hir::Constness::NotConst,
constness: ty::BoundConstness::NotConst,
}));
let computed_preds = param_env.caller_bounds().iter();

5
compiler/rustc_trait_selection/src/traits/mod.rs
View file

@ -778,7 +778,10 @@ pub fn vtable_trait_upcasting_coercion_new_vptr_slot(
let obligation = Obligation::new(
ObligationCause::dummy(),
ty::ParamEnv::reveal_all(),
ty::Binder::dummy(ty::TraitPredicate { trait_ref, constness: hir::Constness::NotConst }),
ty::Binder::dummy(ty::TraitPredicate {
trait_ref,
constness: ty::BoundConstness::NotConst,
}),
);
let implsrc = tcx.infer_ctxt().enter(|infcx| {

5
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View file

@ -8,7 +8,6 @@
//! https://rustc-dev-guide.rust-lang.org/traits/resolution.html#confirmation
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_hir::lang_items::LangItem;
use rustc_hir::Constness;
use rustc_index::bit_set::GrowableBitSet;
use rustc_infer::infer::InferOk;
use rustc_infer::infer::LateBoundRegionConversionTime::HigherRankedType;
@ -75,7 +74,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ProjectionCandidate(idx) => {
let obligations = self.confirm_projection_candidate(obligation, idx)?;
// FIXME(jschievink): constness
Ok(ImplSource::Param(obligations, Constness::NotConst))
Ok(ImplSource::Param(obligations, ty::BoundConstness::NotConst))
}
ObjectCandidate(idx) => {
@ -113,7 +112,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// This indicates something like `Trait + Send: Send`. In this case, we know that
// this holds because that's what the object type is telling us, and there's really
// no additional obligations to prove and no types in particular to unify, etc.
Ok(ImplSource::Param(Vec::new(), Constness::NotConst))
Ok(ImplSource::Param(Vec::new(), ty::BoundConstness::NotConst))
}
BuiltinUnsizeCandidate => {

78
compiler/rustc_trait_selection/src/traits/select/mod.rs
View file

@ -32,7 +32,6 @@ use rustc_data_structures::sync::Lrc;
use rustc_errors::ErrorReported;
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_hir::Constness;
use rustc_infer::infer::LateBoundRegionConversionTime;
use rustc_middle::dep_graph::{DepKind, DepNodeIndex};
use rustc_middle::mir::abstract_const::NotConstEvaluatable;
@ -130,8 +129,8 @@ pub struct SelectionContext<'cx, 'tcx> {
/// and a negative impl
allow_negative_impls: bool,
/// Do we only want const impls when we have a const trait predicate?
const_impls_required: bool,
/// Are we in a const context that needs `~const` bounds to be const?
is_in_const_context: bool,
/// The mode that trait queries run in, which informs our error handling
/// policy. In essence, canonicalized queries need their errors propagated
@ -224,7 +223,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: false,
is_in_const_context: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -236,7 +235,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: true,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: false,
is_in_const_context: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -252,7 +251,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls,
const_impls_required: false,
is_in_const_context: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -268,7 +267,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: false,
is_in_const_context: false,
query_mode,
}
}
@ -283,7 +282,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: matches!(constness, hir::Constness::Const),
is_in_const_context: matches!(constness, hir::Constness::Const),
query_mode: TraitQueryMode::Standard,
}
}
@ -316,14 +315,19 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
self.infcx.tcx
}
/// Returns `true` if the trait predicate is considerd `const` to this selection context.
pub fn is_trait_predicate_const(&self, pred: ty::TraitPredicate<'_>) -> bool {
match pred.constness {
ty::BoundConstness::ConstIfConst if self.is_in_const_context => true,
_ => false,
}
}
/// Returns `true` if the predicate is considered `const` to
/// this selection context.
pub fn is_predicate_const(&self, pred: ty::Predicate<'_>) -> bool {
match pred.kind().skip_binder() {
ty::PredicateKind::Trait(ty::TraitPredicate {
constness: hir::Constness::Const,
..
}) if self.const_impls_required => true,
ty::PredicateKind::Trait(pred) => self.is_trait_predicate_const(pred),
_ => false,
}
}
@ -1074,30 +1078,28 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
) -> SelectionResult<'tcx, SelectionCandidate<'tcx>> {
let tcx = self.tcx();
// Respect const trait obligations
if self.const_impls_required {
if let hir::Constness::Const = obligation.predicate.skip_binder().constness {
if Some(obligation.predicate.skip_binder().trait_ref.def_id)
!= tcx.lang_items().sized_trait()
// const Sized bounds are skipped
{
match candidate {
// const impl
ImplCandidate(def_id)
if tcx.impl_constness(def_id) == hir::Constness::Const => {}
// const param
ParamCandidate(ty::ConstnessAnd {
constness: hir::Constness::Const,
..
}) => {}
// auto trait impl
AutoImplCandidate(..) => {}
// generator, this will raise error in other places
// or ignore error with const_async_blocks feature
GeneratorCandidate => {}
_ => {
// reject all other types of candidates
return Err(Unimplemented);
}
if self.is_trait_predicate_const(obligation.predicate.skip_binder()) {
if Some(obligation.predicate.skip_binder().trait_ref.def_id)
!= tcx.lang_items().sized_trait()
// const Sized bounds are skipped
{
match candidate {
// const impl
ImplCandidate(def_id)
if tcx.impl_constness(def_id) == hir::Constness::Const => {}
// const param
ParamCandidate(ty::ConstnessAnd {
constness: ty::BoundConstness::ConstIfConst,
..
}) => {}
// auto trait impl
AutoImplCandidate(..) => {}
// generator, this will raise error in other places
// or ignore error with const_async_blocks feature
GeneratorCandidate => {}
_ => {
// reject all other types of candidates
return Err(Unimplemented);
}
}
}
@ -1495,7 +1497,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// probably best characterized as a "hack", since we might prefer to just do our
// best to *not* create essentially duplicate candidates in the first place.
other.value.bound_vars().len() <= victim.value.bound_vars().len()
} else if other.value == victim.value && victim.constness == Constness::NotConst {
} else if other.value == victim.value
&& victim.constness == ty::BoundConstness::NotConst
{
// Drop otherwise equivalent non-const candidates in favor of const candidates.
true
} else {

17
compiler/rustc_typeck/src/astconv/mod.rs
View file

@ -20,7 +20,7 @@ use rustc_hir::def::{CtorOf, DefKind, Namespace, Res};
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::intravisit::{walk_generics, Visitor as _};
use rustc_hir::lang_items::LangItem;
use rustc_hir::{Constness, GenericArg, GenericArgs};
use rustc_hir::{GenericArg, GenericArgs};
use rustc_middle::ty::subst::{self, GenericArgKind, InternalSubsts, Subst, SubstsRef};
use rustc_middle::ty::GenericParamDefKind;
use rustc_middle::ty::{self, Const, DefIdTree, Ty, TyCtxt, TypeFoldable};
@ -47,8 +47,6 @@ pub trait AstConv<'tcx> {
fn item_def_id(&self) -> Option<DefId>;
fn default_constness_for_trait_bounds(&self) -> Constness;
/// Returns predicates in scope of the form `X: Foo<T>`, where `X`
/// is a type parameter `X` with the given id `def_id` and T
/// matches `assoc_name`. This is a subset of the full set of
@ -724,7 +722,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
&self,
trait_ref: &hir::TraitRef<'_>,
span: Span,
constness: Constness,
constness: ty::BoundConstness,
self_ty: Ty<'tcx>,
bounds: &mut Bounds<'tcx>,
speculative: bool,
@ -795,7 +793,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
let bound_vars = tcx.late_bound_vars(hir_id);
let poly_trait_ref =
ty::Binder::bind_with_vars(ty::TraitRef::new(trait_def_id, substs), bound_vars);
bounds.trait_bounds.push((poly_trait_ref, span, Constness::NotConst));
bounds.trait_bounds.push((poly_trait_ref, span, ty::BoundConstness::NotConst));
let mut dup_bindings = FxHashMap::default();
for binding in assoc_bindings {
@ -920,14 +918,13 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
bounds: &mut Bounds<'tcx>,
bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
) {
let constness = self.default_constness_for_trait_bounds();
for ast_bound in ast_bounds {
match *ast_bound {
hir::GenericBound::Trait(ref b, hir::TraitBoundModifier::None) => {
self.instantiate_poly_trait_ref(
&b.trait_ref,
b.span,
constness,
ty::BoundConstness::NotConst,
param_ty,
bounds,
false,
@ -937,7 +934,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
self.instantiate_poly_trait_ref(
&b.trait_ref,
b.span,
Constness::NotConst,
ty::BoundConstness::ConstIfConst,
param_ty,
bounds,
false,
@ -1251,7 +1248,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
} = self.instantiate_poly_trait_ref(
&trait_bound.trait_ref,
trait_bound.span,
Constness::NotConst,
ty::BoundConstness::NotConst,
dummy_self,
&mut bounds,
false,
@ -1330,7 +1327,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
.filter(|(trait_ref, _, _)| !tcx.trait_is_auto(trait_ref.def_id()));
for (base_trait_ref, span, constness) in regular_traits_refs_spans {
assert_eq!(constness, Constness::NotConst);
assert_eq!(constness, ty::BoundConstness::NotConst);
for obligation in traits::elaborate_trait_ref(tcx, base_trait_ref) {
debug!(

3
compiler/rustc_typeck/src/bounds.rs
View file

@ -1,7 +1,6 @@
//! Bounds are restrictions applied to some types after they've been converted into the
//! `ty` form from the HIR.
use rustc_hir::Constness;
use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt, WithConstness};
use rustc_span::Span;
@ -30,7 +29,7 @@ pub struct Bounds<'tcx> {
/// A list of trait bounds. So if you had `T: Debug` this would be
/// `T: Debug`. Note that the self-type is explicit here.
pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span, Constness)>,
pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span, ty::BoundConstness)>,
/// A list of projection equality bounds. So if you had `T:
/// Iterator<Item = u32>` this would include `<T as

4
compiler/rustc_typeck/src/check/fn_ctxt/mod.rs
View file

@ -180,10 +180,6 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
None
}
fn default_constness_for_trait_bounds(&self) -> hir::Constness {
self.tcx.hir().get(self.body_id).constness_for_typeck()
}
fn get_type_parameter_bounds(
&self,
_: Span,

21
compiler/rustc_typeck/src/collect.rs
View file

@ -365,10 +365,6 @@ impl AstConv<'tcx> for ItemCtxt<'tcx> {
Some(self.item_def_id)
}
fn default_constness_for_trait_bounds(&self) -> hir::Constness {
self.node().constness_for_typeck()
}
fn get_type_parameter_bounds(
&self,
span: Span,
@ -664,7 +660,6 @@ impl ItemCtxt<'tcx> {
only_self_bounds: OnlySelfBounds,
assoc_name: Option<Ident>,
) -> Vec<(ty::Predicate<'tcx>, Span)> {
let constness = self.default_constness_for_trait_bounds();
let from_ty_params = ast_generics
.params
.iter()
@ -677,7 +672,7 @@ impl ItemCtxt<'tcx> {
Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
None => true,
})
.flat_map(|b| predicates_from_bound(self, ty, b, constness));
.flat_map(|b| predicates_from_bound(self, ty, b));
let from_where_clauses = ast_generics
.where_clause
@ -703,7 +698,7 @@ impl ItemCtxt<'tcx> {
})
.filter_map(move |b| bt.map(|bt| (bt, b)))
})
.flat_map(|(bt, b)| predicates_from_bound(self, bt, b, constness));
.flat_map(|(bt, b)| predicates_from_bound(self, bt, b));
from_ty_params.chain(from_where_clauses).collect()
}
@ -2031,7 +2026,6 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
let mut is_default_impl_trait = None;
let icx = ItemCtxt::new(tcx, def_id);
let constness = icx.default_constness_for_trait_bounds();
const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
@ -2227,8 +2221,10 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
match bound {
hir::GenericBound::Trait(poly_trait_ref, modifier) => {
let constness = match modifier {
hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
hir::TraitBoundModifier::None => constness,
hir::TraitBoundModifier::None => ty::BoundConstness::NotConst,
hir::TraitBoundModifier::MaybeConst => {
ty::BoundConstness::ConstIfConst
}
// We ignore `where T: ?Sized`, it is already part of
// type parameter `T`.
hir::TraitBoundModifier::Maybe => continue,
@ -2491,14 +2487,13 @@ fn predicates_from_bound<'tcx>(
astconv: &dyn AstConv<'tcx>,
param_ty: Ty<'tcx>,
bound: &'tcx hir::GenericBound<'tcx>,
constness: hir::Constness,
) -> Vec<(ty::Predicate<'tcx>, Span)> {
match *bound {
hir::GenericBound::Trait(ref tr, modifier) => {
let constness = match modifier {
hir::TraitBoundModifier::Maybe => return vec![],
hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
hir::TraitBoundModifier::None => constness,
hir::TraitBoundModifier::MaybeConst => ty::BoundConstness::ConstIfConst,
hir::TraitBoundModifier::None => ty::BoundConstness::NotConst,
};
let mut bounds = Bounds::default();

5
compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs
View file

@ -68,7 +68,6 @@
use crate::constrained_generic_params as cgp;
use rustc_data_structures::fx::FxHashSet;
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_infer::infer::outlives::env::OutlivesEnvironment;
use rustc_infer::infer::{InferCtxt, RegionckMode, TyCtxtInferExt};
@ -368,7 +367,7 @@ fn check_specialization_on<'tcx>(tcx: TyCtxt<'tcx>, predicate: ty::Predicate<'tc
// items.
ty::PredicateKind::Trait(ty::TraitPredicate {
trait_ref,
constness: hir::Constness::NotConst,
constness: ty::BoundConstness::NotConst,
}) => {
if !matches!(
trait_predicate_kind(tcx, predicate),
@ -399,7 +398,7 @@ fn trait_predicate_kind<'tcx>(
match predicate.kind().skip_binder() {
ty::PredicateKind::Trait(ty::TraitPredicate {
trait_ref,
constness: hir::Constness::NotConst,
constness: ty::BoundConstness::NotConst,
}) => Some(tcx.trait_def(trait_ref.def_id).specialization_kind),
ty::PredicateKind::Trait(_)
| ty::PredicateKind::RegionOutlives(_)

2
compiler/rustc_typeck/src/lib.rs
View file

@ -548,7 +548,7 @@ pub fn hir_trait_to_predicates<'tcx>(
&item_cx,
hir_trait,
DUMMY_SP,
hir::Constness::NotConst,
ty::BoundConstness::NotConst,
self_ty,
&mut bounds,
true,