From 719dafc48b3a076e9f6341be97bad0cef316f24b Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Mon, 28 Jun 2021 09:19:36 +0200
Subject: [PATCH] double-check mutability inside Allocation

---
 compiler/rustc_middle/src/mir/interpret/allocation.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index ee3902991e911..c0cfc7b1ba4ec 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -340,6 +340,8 @@ impl<Tag: Copy, Extra> Allocation<Tag, Extra> {
         range: AllocRange,
         val: ScalarMaybeUninit<Tag>,
     ) -> AllocResult {
+        assert!(self.mutability == Mutability::Mut);
+
         let val = match val {
             ScalarMaybeUninit::Scalar(scalar) => scalar,
             ScalarMaybeUninit::Uninit => {
@@ -463,6 +465,7 @@ impl<Tag: Copy, Extra> Allocation<Tag, Extra> {
         if range.size.bytes() == 0 {
             return;
         }
+        assert!(self.mutability == Mutability::Mut);
         self.init_mask.set_range(range.start, range.end(), is_init);
     }
 }