normalize receiver substs and erase the regions

use a smaller example

compiler/rustc_ty_utils/src/instance.rs

@@ -44,7 +44,13 @@ fn inner_resolve_instance<'tcx>(
 
     let result = if let Some(trait_def_id) = tcx.trait_of_item(def.did) {
         debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env);
-        resolve_associated_item(tcx, def.did, param_env, trait_def_id, substs)
+        resolve_associated_item(
+            tcx,
+            def.did,
+            param_env,
+            trait_def_id,
+            tcx.normalize_erasing_regions(param_env, substs),
+        )
     } else {
         let ty = tcx.type_of(def.def_id_for_type_of());
         let item_type = tcx.subst_and_normalize_erasing_regions(substs, param_env, ty);

src/test/ui/associated-item/issue-105449.rs

@@ -0,0 +1,59 @@
+// check-pass
+// compile-flags: -C debug_assertions=yes -Zunstable-options
+
+#[allow(dead_code)]
+fn problematic_function<Space>()
+where
+    DefaultAlloc: FinAllok<R1, Space>,
+{
+    let e = Edge2dElement;
+    let _ = Into::<Point>::into(e.map_reference_coords());
+}
+impl<N> Allocator<N, R0> for DefaultAlloc {
+    type Buffer = MStorage;
+}
+impl<N> Allocator<N, R1> for DefaultAlloc {
+    type Buffer = MStorage;
+}
+impl<N, D> From<VectorN<N, D>> for Point
+where
+    DefaultAlloc: Allocator<N, D>,
+{
+    fn from(_: VectorN<N, D>) -> Self {
+        unimplemented!()
+    }
+}
+impl<GeometryDim, NodalDim> FinAllok<GeometryDim, NodalDim> for DefaultAlloc
+where
+    DefaultAlloc: Allocator<Ure, GeometryDim>,
+    DefaultAlloc: Allocator<Ure, NodalDim>
+{
+}
+impl FiniteElement<R1> for Edge2dElement {
+    fn map_reference_coords(&self) -> VectorN<Ure, R1> {
+        unimplemented!()
+    }
+}
+type VectorN<N, R> = (N, R, <DefaultAlloc as Allocator<N, R>>::Buffer);
+struct DefaultAlloc;
+struct R0;
+struct R1;
+struct MStorage;
+struct Point;
+struct Edge2dElement;
+struct Ure;
+trait Allocator<N, R> {
+    type Buffer;
+}
+trait FinAllok<GeometryDim, NodalDim>:
+    Allocator<Ure, GeometryDim> +
+    Allocator<Ure, NodalDim> +
+{
+}
+trait FiniteElement<Rau>
+where
+    DefaultAlloc: FinAllok<Rau, Rau>,
+{
+    fn map_reference_coords(&self) -> VectorN<Ure, Rau>;
+}
+fn main() {}