From 6b0ef9c8105fad1bf7ca43c638ffb491c493cc97 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Wed, 19 Oct 2022 17:10:19 +0000
Subject: [PATCH] Deny const variables as well

---
 compiler/rustc_middle/src/ty/consts/kind.rs | 11 ++++++++++-
 compiler/rustc_middle/src/ty/context.rs     |  4 +---
 compiler/rustc_type_ir/src/lib.rs           |  2 +-
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_middle/src/ty/consts/kind.rs b/compiler/rustc_middle/src/ty/consts/kind.rs
index c444ec23563ce..03866d5e054fd 100644
--- a/compiler/rustc_middle/src/ty/consts/kind.rs
+++ b/compiler/rustc_middle/src/ty/consts/kind.rs
@@ -5,6 +5,7 @@ use crate::mir::interpret::{AllocId, ConstValue, Scalar};
 use crate::ty::subst::{InternalSubsts, SubstsRef};
 use crate::ty::ParamEnv;
 use crate::ty::{self, TyCtxt, TypeVisitable};
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::DefId;
 use rustc_macros::HashStable;
@@ -108,7 +109,6 @@ impl<'tcx> ConstKind<'tcx> {
 
 /// An inference variable for a const, for use in const generics.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable, Hash)]
-#[derive(HashStable)]
 pub enum InferConst<'tcx> {
     /// Infer the value of the const.
     Var(ty::ConstVid<'tcx>),
@@ -116,6 +116,15 @@ pub enum InferConst<'tcx> {
     Fresh(u32),
 }
 
+impl<CTX> HashStable<CTX> for InferConst<'_> {
+    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
+        match self {
+            InferConst::Var(_) => panic!("const variables should not be hashed: {self:?}"),
+            InferConst::Fresh(i) => i.hash_stable(hcx, hasher),
+        }
+    }
+}
+
 enum EvalMode {
     Typeck,
     Mir,
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index b4971ce6ae550..03bb7e54fd5af 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -200,9 +200,7 @@ impl<'tcx> CtxtInterners<'tcx> {
 
                     // It's impossible to hash inference variables (and will ICE), so we don't need to try to cache them.
                     // Without incremental, we rarely stable-hash types, so let's not do it proactively.
-                    let stable_hash = if flags
-                        .flags
-                        .intersects(TypeFlags::HAS_RE_INFER | TypeFlags::HAS_TY_INFER)
+                    let stable_hash = if flags.flags.intersects(TypeFlags::NEEDS_INFER)
                         || sess.opts.incremental.is_none()
                     {
                         Fingerprint::ZERO
diff --git a/compiler/rustc_type_ir/src/lib.rs b/compiler/rustc_type_ir/src/lib.rs
index c950e4e500c9a..7fbe78aa52353 100644
--- a/compiler/rustc_type_ir/src/lib.rs
+++ b/compiler/rustc_type_ir/src/lib.rs
@@ -676,7 +676,7 @@ impl<CTX> HashStable<CTX> for InferTy {
         discriminant(self).hash_stable(ctx, hasher);
         match self {
             TyVar(_) | IntVar(_) | FloatVar(_) => {
-                panic!("inference variables should not be hashed: {self:?}")
+                panic!("type variables should not be hashed: {self:?}")
             }
             FreshTy(v) | FreshIntTy(v) | FreshFloatTy(v) => v.hash_stable(ctx, hasher),
         }