From 2ab85e41789e3996458f1a0578f225669a8e1d84 Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Wed, 3 Jan 2024 18:26:26 +0100 Subject: [PATCH] reword comment --- .../rustc_const_eval/src/interpret/intern.rs | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/compiler/rustc_const_eval/src/interpret/intern.rs b/compiler/rustc_const_eval/src/interpret/intern.rs index a5a94e80b6606..751fbfacaad00 100644 --- a/compiler/rustc_const_eval/src/interpret/intern.rs +++ b/compiler/rustc_const_eval/src/interpret/intern.rs @@ -178,13 +178,16 @@ pub fn intern_const_alloc_recursive< // promoteds as immutable. found_bad_mutable_pointer = true; } - // It is tempting to intern as immutable if `prov.immutable()`. However, there - // might be multiple pointers to the same allocation, and if *at least one* of - // them is mutable, the allocation must be interned mutably. We will intern the - // allocation when we encounter the first pointer. Therefore we always intern - // with `inner_mutability`, and furthermore we ensured above that if that is - // "immutable", then there are *no* mutable pointers anywhere in the newly - // interned memory. + // We always intern with `inner_mutability`, and furthermore we ensured above that if + // that is "immutable", then there are *no* mutable pointers anywhere in the newly + // interned memory -- justifying that we can indeed intern immutably. However this also + // means we can *not* easily intern immutably here if `prov.immutable()` is true and + // `inner_mutability` is `Mut`: there might be other pointers to that allocation, and + // we'd have to somehow check that they are *all* immutable before deciding that this + // allocation can be made immutable. In the future we could consider analyzing all + // pointers before deciding which allocations can be made immutable; but for now we are + // okay with losing some potential for immutability here. This can anyway only affect + // `static mut`. todo.push((alloc_id, inner_mutability)); }) .map_err(|()| {