Add LoweringContext::new.

compiler/rustc_ast_lowering/src/lib.rs

@@ -144,6 +144,46 @@ struct LoweringContext<'a, 'hir> {
     host_param_id: Option<LocalDefId>,
 }
 
+impl<'a, 'hir> LoweringContext<'a, 'hir> {
+    fn new(tcx: TyCtxt<'hir>, resolver: &'a mut ResolverAstLowering) -> Self {
+        Self {
+            // Pseudo-globals.
+            tcx,
+            resolver: resolver,
+            arena: tcx.hir_arena,
+
+            // HirId handling.
+            bodies: Vec::new(),
+            attrs: SortedMap::default(),
+            children: Vec::default(),
+            current_hir_id_owner: hir::CRATE_OWNER_ID,
+            item_local_id_counter: hir::ItemLocalId::new(0),
+            node_id_to_local_id: Default::default(),
+            trait_map: Default::default(),
+
+            // Lowering state.
+            catch_scope: None,
+            loop_scope: None,
+            is_in_loop_condition: false,
+            is_in_trait_impl: false,
+            is_in_dyn_type: false,
+            coroutine_kind: None,
+            task_context: None,
+            current_item: None,
+            impl_trait_defs: Vec::new(),
+            impl_trait_bounds: Vec::new(),
+            allow_try_trait: Some([sym::try_trait_v2, sym::yeet_desugar_details][..].into()),
+            allow_gen_future: Some(if tcx.features().async_fn_track_caller {
+                [sym::gen_future, sym::closure_track_caller][..].into()
+            } else {
+                [sym::gen_future][..].into()
+            }),
+            generics_def_id_map: Default::default(),
+            host_param_id: None,
+        }
+    }
+}
+
 trait ResolverAstLoweringExt {
     fn legacy_const_generic_args(&self, expr: &Expr) -> Option<Vec<usize>>;
     fn get_partial_res(&self, id: NodeId) -> Option<PartialRes>;