Add unit test for issue 78174

src/test/ui/inline-const/const-expr-lifetime.rs

@@ -0,0 +1,36 @@
+// run-pass
+
+#![allow(incomplete_features)]
+#![feature(const_mut_refs)]
+#![feature(inline_const)]
+
+use std::marker::PhantomData;
+
+// rust-lang/rust#78174: ICE: "cannot convert ReErased to a region vid"
+fn issue_78174() {
+    let foo = const { "foo" };
+    assert_eq!(foo, "foo");
+}
+
+pub struct InvariantRef<'a, T: ?Sized>(&'a T, PhantomData<&'a mut &'a T>);
+
+impl<'a, T: ?Sized> InvariantRef<'a, T> {
+    pub const fn new(r: &'a T) -> Self {
+        InvariantRef(r, PhantomData)
+    }
+}
+
+fn get_invariant_ref<'a>() -> InvariantRef<'a, ()> {
+    const { InvariantRef::<'a, ()>::new(&()) }
+}
+
+fn get_invariant_ref2<'a>() -> InvariantRef<'a, ()> {
+    // Try some type inference
+    const { InvariantRef::new(&()) }
+}
+
+fn main() {
+    issue_78174();
+    get_invariant_ref();
+    get_invariant_ref2();
+}

src/test/ui/inline-const/const-match-pat-lifetime.rs

@@ -0,0 +1,36 @@
+// run-pass
+
+#![allow(incomplete_features)]
+#![feature(const_mut_refs)]
+#![feature(inline_const)]
+
+use std::marker::PhantomData;
+
+// rust-lang/rust#78174: ICE: "cannot convert ReErased to a region vid"
+fn issue_78174() {
+    match "foo" {
+        const { concat!("fo", "o") } => (),
+        _ => unreachable!(),
+    }
+}
+
+#[derive(PartialEq, Eq)]
+pub struct InvariantRef<'a, T: ?Sized>(&'a T, PhantomData<&'a mut &'a T>);
+
+impl<'a, T: ?Sized> InvariantRef<'a, T> {
+    pub const fn new(r: &'a T) -> Self {
+        InvariantRef(r, PhantomData)
+    }
+}
+
+fn match_invariant_ref<'a>() {
+    match const { InvariantRef::<'a, _>::new(&()) } {
+        const { InvariantRef::<'a, ()>::new(&()) } => {
+        }
+    }
+}
+
+fn main() {
+    issue_78174();
+    match_invariant_ref();
+}