From 22f415692ea6ede328f938b343d334658331b3e1 Mon Sep 17 00:00:00 2001
From: bohan <bohan-zhang@foxmail.com>
Date: Sat, 18 Feb 2023 20:54:49 +0800
Subject: [PATCH] fix: mock `ConstParm` when encounter `LateBound` during
 convert path expr

---
 compiler/rustc_mir_build/src/thir/cx/expr.rs  | 25 ++++++++++++++-----
 .../traits/non_lifetime_binders/path-expr.rs  | 10 ++++++++
 .../non_lifetime_binders/path-expr.stderr     | 11 ++++++++
 3 files changed, 40 insertions(+), 6 deletions(-)
 create mode 100644 tests/ui/traits/non_lifetime_binders/path-expr.rs
 create mode 100644 tests/ui/traits/non_lifetime_binders/path-expr.stderr

diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 261b95ba95b0e..feba226895e3a 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -856,12 +856,25 @@ impl<'tcx> Cx<'tcx> {
 
             Res::Def(DefKind::ConstParam, def_id) => {
                 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
-                let generics = self.tcx.generics_of(hir_id.owner);
-                let index = generics.param_def_id_to_index[&def_id];
-                let name = self.tcx.hir().name(hir_id);
-                let param = ty::ParamConst::new(index, name);
-
-                ExprKind::ConstParam { param, def_id }
+                if let Some(index) =
+                    self.tcx.generics_of(hir_id.owner).param_def_id_to_index.get(&def_id)
+                {
+                    let name = self.tcx.hir().name(hir_id);
+                    let param = ty::ParamConst::new(*index, name);
+                    ExprKind::ConstParam { param, def_id }
+                } else {
+                    use rustc_middle::middle::resolve_bound_vars as rbv;
+                    match self.tcx.named_bound_var(expr.hir_id) {
+                        Some(rbv::ResolvedArg::LateBound(_, index, _)) => {
+                            let name = self.tcx.hir().name(hir_id);
+                            let param = ty::ParamConst::new(index, name);
+                            ExprKind::ConstParam { param, def_id }
+                        }
+                        arg => {
+                            bug!("unexpected bound var resolution for {:?}: {arg:?}", expr.hir_id)
+                        }
+                    }
+                }
             }
 
             Res::Def(DefKind::Const, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
diff --git a/tests/ui/traits/non_lifetime_binders/path-expr.rs b/tests/ui/traits/non_lifetime_binders/path-expr.rs
new file mode 100644
index 0000000000000..adcdf2a1cfe83
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/path-expr.rs
@@ -0,0 +1,10 @@
+// check-pass
+
+#![feature(non_lifetime_binders)]
+//~^ WARN the feature `non_lifetime_binders` is incomplete
+
+fn b() where for<const C: usize> [(); C]: Clone {}
+
+fn main() {
+    b();
+}
diff --git a/tests/ui/traits/non_lifetime_binders/path-expr.stderr b/tests/ui/traits/non_lifetime_binders/path-expr.stderr
new file mode 100644
index 0000000000000..65473a45e3064
--- /dev/null
+++ b/tests/ui/traits/non_lifetime_binders/path-expr.stderr
@@ -0,0 +1,11 @@
+warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/path-expr.rs:3:12
+   |
+LL | #![feature(non_lifetime_binders)]
+   |            ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+