Report wrong async function result type as type error in checked mode (Fixes #26133).

runtime/vm/ast.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_AST_H_
 #define VM_AST_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/growable_array.h"
@@ skipping 598 matching lines @@
 
   DECLARE_COMMON_NODE_FUNCTIONS(PrimaryNode);
 
  private:
   const Object& primary_;
   bool is_deferred_reference_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PrimaryNode);
 };
 
-// In asynchronous code that gets suspeded and resumed, return nodes
+// In asynchronous code that gets suspended and resumed, return nodes
 // can be of different types:
 // * A regular return node that in the case of async functions
 //    gets replaced with appropriate completer calls. (kRegular)
 // * A continuation return that just returns from a function, without
 //   completing the Future. (kContinuation)
 // * A continuation return followed by a continuation target, i.e. the
 //   location at which the closure resumes the next time it gets invoked.
 //   (kContinuationTarget).
 // In synchronous functions, return nodes are always of type'kRegular'
 class ReturnNode : public AstNode {
@@ skipping 1384 matching lines @@
   const intptr_t try_index_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(InlinedFinallyNode);
 };
 
 }  // namespace dart
 
 #undef DECLARE_COMMON_NODE_FUNCTIONS
 
 #endif  // VM_AST_H_