Do not ICE on closure typeck

Tackle rust-lang#66868.

Author: estebank

src/librustc/traits/error_reporting.rs

@@ -2214,6 +2214,10 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         }
 
         let span = self.tcx.def_span(generator_did);
+        // Do not ICE on closure typeck (#66868).
+        if let None = self.tcx.hir().as_local_hir_id(generator_did) {
+            return false;
+        }
         let tables = self.tcx.typeck_tables_of(generator_did);
         debug!("note_obligation_cause_for_async_await: generator_did={:?} span={:?} ",
                generator_did, span);