From 4d9451b1d1e334e90e6725d5577545eae4e28545 Mon Sep 17 00:00:00 2001
From: Oli Scherer <git-spam-no-reply9815368754983@oli-obk.de>
Date: Thu, 17 Nov 2022 15:30:42 +0000
Subject: [PATCH] Fix an ICE that I just made worse

---
 .../src/thir/pattern/const_to_pat.rs          | 10 +---------
 .../const-partial_eq-fallback-ice.rs          | 20 +++++++++++++++++++
 .../const-partial_eq-fallback-ice.stderr      |  8 ++++++++
 3 files changed, 29 insertions(+), 9 deletions(-)
 create mode 100644 src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.rs
 create mode 100644 src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.stderr

diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
index 1ed954bdd46..4364fca9739 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
@@ -1,7 +1,6 @@
 use rustc_errors::DelayDm;
 use rustc_hir as hir;
 use rustc_index::vec::Idx;
-use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_middle::mir::{self, Field};
 use rustc_middle::thir::{FieldPat, Pat, PatKind};
@@ -227,13 +226,6 @@ impl<'tcx> ConstToPat<'tcx> {
         // using `PartialEq::eq` in this scenario in the past.)
         let partial_eq_trait_id =
             self.tcx().require_lang_item(hir::LangItem::PartialEq, Some(self.span));
-        let any_ty = self
-            .infcx
-            .next_ty_var(TypeVariableOrigin {
-                kind: TypeVariableOriginKind::MiscVariable,
-                span: self.span,
-            })
-            .into();
         let obligation: PredicateObligation<'_> = predicate_for_trait_def(
             self.tcx(),
             self.param_env,
@@ -241,7 +233,7 @@ impl<'tcx> ConstToPat<'tcx> {
             partial_eq_trait_id,
             0,
             ty,
-            [any_ty],
+            [ty.into()],
         );
         // FIXME: should this call a `predicate_must_hold` variant instead?
 
diff --git a/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.rs b/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.rs
new file mode 100644
index 00000000000..daa432d9ae5
--- /dev/null
+++ b/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.rs
@@ -0,0 +1,20 @@
+#![allow(warnings)]
+
+struct MyType;
+
+impl PartialEq<usize> for MyType {
+    fn eq(&self, y: &usize) -> bool {
+        true
+    }
+}
+
+const CONSTANT: &&MyType = &&MyType;
+
+fn main() {
+    if let CONSTANT = &&MyType {
+        //~^ ERROR must be annotated with `#[derive(PartialEq, Eq)]`
+        println!("semantic!");
+    } else {
+        println!("structural!");
+    }
+}
diff --git a/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.stderr b/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.stderr
new file mode 100644
index 00000000000..358421cd6d2
--- /dev/null
+++ b/src/test/ui/pattern/usefulness/const-partial_eq-fallback-ice.stderr
@@ -0,0 +1,8 @@
+error: to use a constant of type `MyType` in a pattern, `MyType` must be annotated with `#[derive(PartialEq, Eq)]`
+  --> $DIR/const-partial_eq-fallback-ice.rs:14:12
+   |
+LL |     if let CONSTANT = &&MyType {
+   |            ^^^^^^^^
+
+error: aborting due to previous error
+