squiid/rust
1
0
Fork 0
Code Issues Pull requests Projects Activity

Elaborate some more on what mutability field means what

Browse source
This commit is contained in:
Oliver Scherer 2019-06-13 17:18:10 +02:00
parent 521d38adb5
commit 6229a8f1f6
1 changed files with 8 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
src/librustc_mir/interpret/intern.rs
View file

@ -181,6 +181,8 @@ for
(InternMode::Const, hir::Mutability::MutMutable) =>
bug!("const qualif failed to prevent mutable references"),
}
// Compute the mutability with which we'll start visiting the allocation. This is
// what gets changed when we encounter an `UnsafeCell`
let mutability = match (self.mutability, mutability) {
// The only way a mutable reference actually works as a mutable reference is
// by being in a `static mut` directly or behind another mutable reference.
@ -190,6 +192,7 @@ for
(Mutability::Mutable, hir::Mutability::MutMutable) => Mutability::Mutable,
_ => Mutability::Immutable,
};
// Compute the mutability of the allocation
let intern_mutability = intern_mutability(
self.ecx.tcx.tcx,
self.param_env,
@ -244,6 +247,7 @@ pub fn intern_const_alloc_recursive(
param_env: ty::ParamEnv<'tcx>,
) -> InterpResult<'tcx> {
let tcx = ecx.tcx;
// this `mutability` is the mutability of the place, ignoring the type
let (mutability, base_intern_mode) = match tcx.static_mutability(def_id) {
Some(hir::Mutability::MutImmutable) => (Mutability::Immutable, InternMode::Static),
None => (Mutability::Immutable, InternMode::ConstBase),
@ -255,6 +259,10 @@ pub fn intern_const_alloc_recursive(
let mut ref_tracking = RefTracking::new((ret, mutability, base_intern_mode));
let leftover_relocations = &mut FxHashSet::default();
// This mutability is the combination of the place mutability and the type mutability. If either
// is mutable, `alloc_mutability` is mutable. This exists because the entire allocation needs
// to be mutable if it contains an `UnsafeCell` anywhere. The other `mutability` exists so that
// the visitor does not treat everything outside the `UnsafeCell` as mutable.
let alloc_mutability = intern_mutability(
tcx.tcx, param_env, ret.layout.ty, tcx.span, mutability,
);