bjoernager/rust
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Auto merge of #116015 - EvanMerlock:master, r=oli-obk

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const_eval: allow function pointer signatures containing &mut T in const contexts

potentially fixes #114994

We utilize a `TypeVisitor` here in order to more easily handle control flow.
- In the event the typekind the Visitor sees is a function pointer, we skip over it
- However, otherwise we do one of two things:
   - If we find a mutable reference, check it, then continue visiting types
   - If we find any other type, continue visiting types

This means we will check if the function pointer _itself_ is mutable, but not if any of the types _within_ are.
This commit is contained in:
bors 2023-10-14 09:18:28 +00:00
commit 139f63a6eb
4 changed files with 76 additions and 15 deletions
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38
compiler/rustc_const_eval/src/transform/check_consts/check.rs
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@ -9,16 +9,17 @@ use rustc_infer::traits::{ImplSource, Obligation, ObligationCause};
use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
use rustc_middle::mir::*;
use rustc_middle::traits::BuiltinImplSource;
use rustc_middle::ty::GenericArgs;
use rustc_middle::ty::{self, adjustment::PointerCoercion, Instance, InstanceDef, Ty, TyCtxt};
use rustc_middle::ty::{GenericArgKind, GenericArgs};
use rustc_middle::ty::{TraitRef, TypeVisitableExt};
use rustc_mir_dataflow::{self, Analysis};
use rustc_span::{sym, Span, Symbol};
use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
use rustc_trait_selection::traits::{self, ObligationCauseCode, ObligationCtxt, SelectionContext};
use rustc_type_ir::visit::{TypeSuperVisitable, TypeVisitor};
use std::mem;
use std::ops::Deref;
use std::ops::{ControlFlow, Deref};
use super::ops::{self, NonConstOp, Status};
use super::qualifs::{self, CustomEq, HasMutInterior, NeedsDrop};
@ -188,6 +189,24 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
}
}
struct LocalReturnTyVisitor<'ck, 'mir, 'tcx> {
kind: LocalKind,
checker: &'ck mut Checker<'mir, 'tcx>,
}
impl<'ck, 'mir, 'tcx> TypeVisitor<TyCtxt<'tcx>> for LocalReturnTyVisitor<'ck, 'mir, 'tcx> {
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
match t.kind() {
ty::FnPtr(_) => ControlFlow::Continue(()),
ty::Ref(_, _, hir::Mutability::Mut) => {
self.checker.check_op(ops::ty::MutRef(self.kind));
t.super_visit_with(self)
}
_ => t.super_visit_with(self),
}
}
}
pub struct Checker<'mir, 'tcx> {
ccx: &'mir ConstCx<'mir, 'tcx>,
qualifs: Qualifs<'mir, 'tcx>,
@ -346,20 +365,9 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
fn check_local_or_return_ty(&mut self, ty: Ty<'tcx>, local: Local) {
let kind = self.body.local_kind(local);
for ty in ty.walk() {
let ty = match ty.unpack() {
GenericArgKind::Type(ty) => ty,
let mut visitor = LocalReturnTyVisitor { kind, checker: self };
// 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) => self.check_op(ops::ty::MutRef(kind)),
_ => {}
}
}
visitor.visit_ty(ty);
}
fn check_mut_borrow(&mut self, local: Local, kind: hir::BorrowKind) {