Overloaded deref on type Foo is not a projection

[darichey]

This can probably be minimized further, but I don't understand the code well enough...

struct Foo {}

fn foo() {
    let x: Box<Foo> = todo!();
    let y: &Foo = todo!();

    || match x {
        ref x => x,
        _ => y,
    }
}

internal error: entered unreachable code: Overloaded deref on type Foo is not a projection
stack backtrace:
   0: rust_begin_unwind
             at /rustc/90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf/library/std/src/panicking.rs:665:5
   1: core::panicking::panic_fmt
             at /rustc/90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf/library/core/src/panicking.rs:74:14
   2: hir_ty::mir::ProjectionElem<V,T>::projected_ty
             at /Users/davidrichey/Desktop/test/rust-analyzer/crates/hir-ty/src/mir.rs:162:21
   3: hir_ty::infer::closure::<impl hir_ty::infer::InferenceContext>::restrict_precision_for_unsafe
             at /Users/davidrichey/Desktop/test/rust-analyzer/crates/hir-ty/src/infer/closure.rs:1050:22
   4: hir_ty::infer::closure::<impl hir_ty::infer::InferenceContext>::analyze_closure
             at /Users/davidrichey/Desktop/test/rust-analyzer/crates/hir-ty/src/infer/closure.rs:1299:9
   5: hir_ty::infer::closure::<impl hir_ty::infer::InferenceContext>::infer_closures
             at /Users/davidrichey/Desktop/test/rust-analyzer/crates/hir-ty/src/infer/closure.rs:1339:24
   6: hir_ty::infer::infer_query
             at /Users/davidrichey/Desktop/test/rust-analyzer/crates/hir-ty/src/infer.rs:143:5

rust-analyzer/crates/hir-ty/src/mir.rs

Lines 156 to 168 in 6e4c29f

	ProjectionElem::Deref => match &base.kind(Interner) {
	TyKind::Raw(_, inner) | TyKind::Ref(_, _, inner) => inner.clone(),
	TyKind::Adt(adt, subst) if is_box(db, adt.0) => {
	subst.at(Interner, 0).assert_ty_ref(Interner).clone()
	}
	_ => {
	never!(
	"Overloaded deref on type {} is not a projection",
	base.display(db, db.crate_graph()[krate].edition)
	);
	TyKind::Error.intern(Interner)
	}
	},

[ShoyuVanilla]

Oh, this is strange 🤔

[Veykril]

That's a never! check that fails, so not really a panic. It only panics in builds where instructed to do so (usually a manual build, not a github release)