Fix summary type inference for async closures.

pkg/analyzer/lib/src/summary/link.dart

Index: pkg/analyzer/lib/src/summary/link.dart
diff --git a/pkg/analyzer/lib/src/summary/link.dart b/pkg/analyzer/lib/src/summary/link.dart
index b12d17dad26cc168b4d98bbc6d3b862c47c7bc0a..0587df1322e7bb2621550c509412fd6c96ea3054 100644
--- a/pkg/analyzer/lib/src/summary/link.dart
+++ b/pkg/analyzer/lib/src/summary/link.dart
@@ -4672,6 +4672,9 @@ class TypeInferenceNode extends Node<TypeInferenceNode> {
         var linker = functionElement.compilationUnit.library._linker;
         var typeProvider = linker.typeProvider;
         var typeSystem = linker.typeSystem;
+        if (bodyType.isDartAsyncFutureOr) {
+          bodyType = (bodyType as InterfaceType).typeArguments[0];
+        }
         bodyType = typeProvider.futureType
             .instantiate([bodyType.flattenFutures(typeSystem)]);
       }