Call methods on the right tcx

There are two `TyCtxt`s, one global, one local. Methods must be called
on the right one, as they differ by invariant lifetimes.

src/librustc_typeck/check/wfcheck.rs

@@ -343,8 +343,8 @@ fn check_item_fn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, item: &hir::Item) {
 fn check_item_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, item_id: ast::NodeId, ty_span: Span) {
     debug!("check_item_type: {:?}", item_id);
 
-    for_id(tcx, item_id, ty_span).with_fcx(|fcx, _this| {
-        let ty = fcx.tcx.type_of(fcx.tcx.hir.local_def_id(item_id));
+    for_id(tcx, item_id, ty_span).with_fcx(|fcx, gcx| {
+        let ty = gcx.type_of(gcx.hir.local_def_id(item_id));
         let item_ty = fcx.normalize_associated_types_in(ty_span, &ty);
 
         fcx.register_wf_obligation(item_ty, ty_span, ObligationCauseCode::MiscObligation);