Fix ICE on invalid const param types

Author: gurry

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -551,6 +551,24 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         if let Err(guar) = ty.error_reported() {
                             return ty::Const::new_error(tcx, guar, ty).into();
                         }
+
+                        let param_span = match tcx.hir().span_if_local(param.def_id) {
+                            Some(sp) => sp,
+                            _ => self.span,
+                        };
+
+                        // Ensure that the const param does not have an unsupported
+                        // type or we ICE later (see #123863)
+                        if !tcx.features().adt_const_params
+                            && !matches!(ty.kind(), ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_))
+                        {
+                            let guar = tcx.dcx().span_delayed_bug(
+                                param_span,
+                                "Const param has unsupported type but no error emitted",
+                            );
+                            return ty::Const::new_error(tcx, guar, ty).into();
+                        };
+
                         // FIXME(effects) see if we should special case effect params here
                         if !infer_args && has_default {
                             tcx.const_param_default(param.def_id)