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Add a helper function for checking whether a default function in a trait can be treated as const

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This commit is contained in:
Oli Scherer 2022-05-11 16:02:20 +00:00
parent 257f06587c
commit 4d390de4a3
7 changed files with 20 additions and 18 deletions
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3
compiler/rustc_const_eval/src/const_eval/machine.rs
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@ -278,8 +278,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
// at all.
if !ecx.tcx.is_const_fn_raw(def.did) {
// allow calling functions inside a trait marked with #[const_trait].
if !matches!(ecx.tcx.trait_of_item(def.did), Some(trait_id) if ecx.tcx.has_attr(trait_id, sym::const_trait))
{
if !ecx.tcx.is_const_default_method(def.did) {
// We certainly do *not* want to actually call the fn
// though, so be sure we return here.
throw_unsup_format!("calling non-const function `{}`", instance)

12
compiler/rustc_const_eval/src/transform/check_consts/check.rs
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@ -872,13 +872,11 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
let is_intrinsic = tcx.is_intrinsic(callee);
if !tcx.is_const_fn_raw(callee) {
if tcx.trait_of_item(callee).is_some() {
if let Some(callee_trait) = tcx.trait_of_item(callee) && tcx.has_attr(callee_trait, sym::const_trait) {
// 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 tcx.is_const_default_method(callee) {
// 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 !nonconst_call_permission {

4
compiler/rustc_const_eval/src/transform/check_consts/mod.rs
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@ -9,7 +9,7 @@ use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_middle::mir;
use rustc_middle::ty::{self, TyCtxt};
use rustc_span::{sym, Symbol};
use rustc_span::Symbol;
pub use self::qualifs::Qualif;
@ -87,7 +87,7 @@ pub fn is_const_stable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
// A default body in a `#[const_trait]` is not const-stable because const
// trait fns currently cannot be const-stable. We shouldn't
// restrict default bodies to only call const-stable functions.
if let Some(trait_id) = tcx.trait_of_item(def_id) && tcx.has_attr(trait_id, sym::const_trait) {
if tcx.is_const_default_method(def_id) {
return false;
}

6
compiler/rustc_metadata/src/rmeta/encoder.rs
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@ -892,10 +892,8 @@ fn should_encode_mir(tcx: TyCtxt<'_>, def_id: LocalDefId) -> (bool, bool) {
|| tcx.codegen_fn_attrs(def_id).requests_inline())
&& tcx.sess.opts.output_types.should_codegen();
// The function has a `const` modifier or is in a `#[const_trait]`.
let mut is_const_fn = tcx.is_const_fn_raw(def_id.to_def_id());
if let Some(trait_) = tcx.trait_of_item(def_id.to_def_id()) {
is_const_fn = is_const_fn || tcx.has_attr(trait_, sym::const_trait);
}
let is_const_fn = tcx.is_const_fn_raw(def_id.to_def_id())
|| tcx.is_const_default_method(def_id.to_def_id());
let always_encode_mir = tcx.sess.opts.debugging_opts.always_encode_mir;
(is_const_fn, needs_inline || always_encode_mir)
}

2
compiler/rustc_middle/src/hir/map/mod.rs
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@ -494,7 +494,7 @@ impl<'hir> Map<'hir> {
BodyOwnerKind::Fn if self.tcx.is_const_fn_raw(def_id.to_def_id()) => {
ConstContext::ConstFn
}
BodyOwnerKind::Fn if matches!(self.tcx.trait_of_item(def_id.to_def_id()), Some(trait_id) if self.tcx.has_attr(trait_id, sym::const_trait)) => {
BodyOwnerKind::Fn if self.tcx.is_const_default_method(def_id.to_def_id()) => {
ConstContext::ConstFn
}
BodyOwnerKind::Fn | BodyOwnerKind::Closure => return None,

5
compiler/rustc_middle/src/ty/mod.rs
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@ -2301,6 +2301,11 @@ impl<'tcx> TyCtxt<'tcx> {
matches!(self.def_kind(def_id), DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(..))
&& self.impl_constness(def_id) == hir::Constness::Const
}
#[inline]
pub fn is_const_default_method(self, def_id: DefId) -> bool {
matches!(self.trait_of_item(def_id), Some(trait_id) if self.has_attr(trait_id, sym::const_trait))
}
}
/// Yields the parent function's `LocalDefId` if `def_id` is an `impl Trait` definition.

6
compiler/rustc_ty_utils/src/ty.rs
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@ -5,7 +5,7 @@ use rustc_middle::ty::subst::Subst;
use rustc_middle::ty::{
self, Binder, EarlyBinder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt,
};
use rustc_span::{sym, Span};
use rustc_span::Span;
use rustc_trait_selection::traits;
fn sized_constraint_for_ty<'tcx>(
@ -152,7 +152,9 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
let constness = match hir_id {
Some(hir_id) => match tcx.hir().get(hir_id) {
hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. }) if matches!(tcx.trait_of_item(def_id), Some(trait_id) if tcx.has_attr(trait_id, sym::const_trait)) => {
hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
if tcx.is_const_default_method(def_id) =>
{
hir::Constness::Const
}