diff --git a/compiler/rustc_const_eval/src/const_eval/fn_queries.rs b/compiler/rustc_const_eval/src/const_eval/fn_queries.rs
index 10afd9560fa95..df4cc295fac5f 100644
--- a/compiler/rustc_const_eval/src/const_eval/fn_queries.rs
+++ b/compiler/rustc_const_eval/src/const_eval/fn_queries.rs
@@ -6,23 +6,6 @@ use rustc_middle::ty::TyCtxt;
use rustc_span::symbol::Symbol;
use rustc_target::spec::abi::Abi;
-/// Whether the `def_id` counts as const fn in your current crate, considering all active
-/// feature gates
-pub fn is_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
- tcx.is_const_fn_raw(def_id)
- && match is_unstable_const_fn(tcx, def_id) {
- Some(feature_name) => {
- // has a `rustc_const_unstable` attribute, check whether the user enabled the
- // corresponding feature gate.
- tcx.features().declared_lib_features.iter().any(|&(sym, _)| sym == feature_name)
- }
- // functions without const stability are either stable user written
- // const fn or the user is using feature gates and we thus don't
- // care what they do
- None => true,
- }
-}
-
/// Whether the `def_id` is an unstable const fn and what feature gate is necessary to enable it
pub fn is_unstable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Symbol> {
if tcx.is_const_fn_raw(def_id) {
@@ -77,7 +60,7 @@ fn is_const_fn_raw(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
}
fn is_promotable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
- is_const_fn(tcx, def_id)
+ tcx.is_const_fn(def_id)
&& match tcx.lookup_const_stability(def_id) {
Some(stab) => {
if cfg!(debug_assertions) && stab.promotable {
diff --git a/compiler/rustc_const_eval/src/transform/promote_consts.rs b/compiler/rustc_const_eval/src/transform/promote_consts.rs
index 52d04cb4ff1e0..c1cb5326ca35a 100644
--- a/compiler/rustc_const_eval/src/transform/promote_consts.rs
+++ b/compiler/rustc_const_eval/src/transform/promote_consts.rs
@@ -26,7 +26,6 @@ use rustc_index::vec::{Idx, IndexVec};
use std::cell::Cell;
use std::{cmp, iter, mem};
-use crate::const_eval::{is_const_fn, is_unstable_const_fn};
use crate::transform::check_consts::{is_lang_panic_fn, qualifs, ConstCx};
use crate::transform::MirPass;
@@ -656,9 +655,7 @@ impl<'tcx> Validator<'_, 'tcx> {
let is_const_fn = match *fn_ty.kind() {
ty::FnDef(def_id, _) => {
- is_const_fn(self.tcx, def_id)
- || is_unstable_const_fn(self.tcx, def_id).is_some()
- || is_lang_panic_fn(self.tcx, def_id)
+ self.tcx.is_const_fn_raw(def_id) || is_lang_panic_fn(self.tcx, def_id)
}
_ => false,
};
@@ -1079,7 +1076,7 @@ pub fn is_const_fn_in_array_repeat_expression<'tcx>(
if let ty::FnDef(def_id, _) = *literal.ty().kind() {
if let Some((destination_place, _)) = destination {
if destination_place == place {
- if is_const_fn(ccx.tcx, def_id) {
+ if ccx.tcx.is_const_fn(def_id) {
return true;
}
}
diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs
index 3c0fedb360827..e236c4712c883 100644
--- a/compiler/rustc_middle/src/traits/select.rs
+++ b/compiler/rustc_middle/src/traits/select.rs
@@ -120,7 +120,9 @@ pub enum SelectionCandidate<'tcx> {
/// Implementation of a `Fn`-family trait by one of the anonymous
/// types generated for a fn pointer type (e.g., `fn(int) -> int`)
- FnPointerCandidate,
+ FnPointerCandidate {
+ is_const: bool,
+ },
/// Builtin implementation of `DiscriminantKind`.
DiscriminantKindCandidate,
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 1f5057d1da22f..8cbae81f67348 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -2741,6 +2741,29 @@ impl<'tcx> TyCtxt<'tcx> {
pub fn lifetime_scope(self, id: HirId) -> Option<LifetimeScopeForPath> {
self.lifetime_scope_map(id.owner).and_then(|mut map| map.remove(&id.local_id))
}
+
+ /// Whether the `def_id` counts as const fn in the current crate, considering all active
+ /// feature gates
+ pub fn is_const_fn(self, def_id: DefId) -> bool {
+ if self.is_const_fn_raw(def_id) {
+ match self.lookup_const_stability(def_id) {
+ Some(stability) if stability.level.is_unstable() => {
+ // has a `rustc_const_unstable` attribute, check whether the user enabled the
+ // corresponding feature gate.
+ self.features()
+ .declared_lib_features
+ .iter()
+ .any(|&(sym, _)| sym == stability.feature)
+ }
+ // functions without const stability are either stable user written
+ // const fn or the user is using feature gates and we thus don't
+ // care what they do
+ _ => true,
+ }
+ } else {
+ false
+ }
+ }
}
impl TyCtxtAt<'tcx> {
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 6d64dc8254bb4..d31ae216d3a57 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -475,7 +475,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
..
} = self_ty.fn_sig(self.tcx()).skip_binder()
{
- candidates.vec.push(FnPointerCandidate);
+ candidates.vec.push(FnPointerCandidate { is_const: false });
}
}
// Provide an impl for suitable functions, rejecting `#[target_feature]` functions (RFC 2396).
@@ -488,7 +488,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
} = self_ty.fn_sig(self.tcx()).skip_binder()
{
if self.tcx().codegen_fn_attrs(def_id).target_features.is_empty() {
- candidates.vec.push(FnPointerCandidate);
+ candidates
+ .vec
+ .push(FnPointerCandidate { is_const: self.tcx().is_const_fn(def_id) });
}
}
}
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 3b6555de912e9..b3ebd1cb1c440 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -92,7 +92,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
Ok(ImplSource::Generator(vtable_generator))
}
- FnPointerCandidate => {
+ FnPointerCandidate { .. } => {
let data = self.confirm_fn_pointer_candidate(obligation)?;
Ok(ImplSource::FnPointer(data))
}
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 7b948a0939fff..8dfd71e9cfb65 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1100,6 +1100,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// generator, this will raise error in other places
// or ignore error with const_async_blocks feature
GeneratorCandidate => {}
+ // FnDef where the function is const
+ FnPointerCandidate { is_const: true } => {}
ConstDropCandidate => {}
_ => {
// reject all other types of candidates
@@ -1513,6 +1515,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
}
+ // Drop otherwise equivalent non-const fn pointer candidates
+ (FnPointerCandidate { .. }, FnPointerCandidate { is_const: false }) => true,
+
// Global bounds from the where clause should be ignored
// here (see issue #50825). Otherwise, we have a where
// clause so don't go around looking for impls.
@@ -1523,7 +1528,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(..)
| ClosureCandidate
| GeneratorCandidate
- | FnPointerCandidate
+ | FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
@@ -1541,7 +1546,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(_)
| ClosureCandidate
| GeneratorCandidate
- | FnPointerCandidate
+ | FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
@@ -1571,7 +1576,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(..)
| ClosureCandidate
| GeneratorCandidate
- | FnPointerCandidate
+ | FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
@@ -1583,7 +1588,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(..)
| ClosureCandidate
| GeneratorCandidate
- | FnPointerCandidate
+ | FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
@@ -1664,7 +1669,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(_)
| ClosureCandidate
| GeneratorCandidate
- | FnPointerCandidate
+ | FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
@@ -1673,7 +1678,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ImplCandidate(_)
| ClosureCandidate
| GeneratorCandidate
- | FnPointerCandidate
+ | FnPointerCandidate { .. }
| BuiltinObjectCandidate
| BuiltinUnsizeCandidate
| TraitUpcastingUnsizeCandidate(_)
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index e281bbc59c255..ae7e818f106a6 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -11,7 +11,7 @@ crate mod utils;
use rustc_ast as ast;
use rustc_attr as attr;
-use rustc_const_eval::const_eval::{is_const_fn, is_unstable_const_fn};
+use rustc_const_eval::const_eval::is_unstable_const_fn;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_hir as hir;
use rustc_hir::def::{CtorKind, DefKind, Res};
@@ -787,7 +787,7 @@ fn clean_fn_or_proc_macro(
let mut func = (sig, generics, body_id).clean(cx);
let def_id = item.def_id.to_def_id();
func.header.constness =
- if is_const_fn(cx.tcx, def_id) && is_unstable_const_fn(cx.tcx, def_id).is_none() {
+ if cx.tcx.is_const_fn(def_id) && is_unstable_const_fn(cx.tcx, def_id).is_none() {
hir::Constness::Const
} else {
hir::Constness::NotConst
diff --git a/src/test/ui/rfc-2632-const-trait-impl/const-closures.rs b/src/test/ui/rfc-2632-const-trait-impl/const-closures.rs
new file mode 100644
index 0000000000000..99e608797ff65
--- /dev/null
+++ b/src/test/ui/rfc-2632-const-trait-impl/const-closures.rs
@@ -0,0 +1,31 @@
+// run-pass
+
+#![feature(const_trait_impl)]
+#![feature(const_fn_trait_bound)]
+
+const fn answer_p1<F>(f: &F) -> u8
+ where
+ F: ~const FnOnce() -> u8,
+ F: ~const FnMut() -> u8,
+ F: ~const Fn() -> u8,
+{
+ f() * 7
+}
+
+const fn three() -> u8 {
+ 3
+}
+
+const fn answer_p2() -> u8 {
+ answer_p1(&three)
+}
+
+const fn answer<F: ~const Fn() -> u8>(f: &F) -> u8 {
+ f() + f()
+}
+
+const ANSWER: u8 = answer(&answer_p2);
+
+fn main() {
+ assert_eq!(ANSWER, 42)
+}
diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs
index 3a94f47298390..beddc6f09be81 100644
--- a/src/tools/clippy/clippy_utils/src/lib.rs
+++ b/src/tools/clippy/clippy_utils/src/lib.rs
@@ -18,7 +18,6 @@
extern crate rustc_ast;
extern crate rustc_ast_pretty;
extern crate rustc_attr;
-extern crate rustc_const_eval;
extern crate rustc_data_structures;
extern crate rustc_errors;
extern crate rustc_hir;
diff --git a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
index e9a9895cb746f..67dda33e9daaf 100644
--- a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
+++ b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
@@ -364,7 +364,7 @@ fn check_terminator(
}
fn is_const_fn(tcx: TyCtxt<'_>, def_id: DefId, msrv: Option<&RustcVersion>) -> bool {
- rustc_const_eval::const_eval::is_const_fn(tcx, def_id)
+ tcx.is_const_fn(def_id)
&& tcx.lookup_const_stability(def_id).map_or(true, |const_stab| {
if let rustc_attr::StabilityLevel::Stable { since } = const_stab.level {
// Checking MSRV is manually necessary because `rustc` has no such concept. This entire