Use declared return type for inference of return and yield statements.

pkg/front_end/testcases/inference/top_level_return_and_yield.dart.strong.expect

Index: pkg/front_end/testcases/inference/top_level_return_and_yield.dart.strong.expect
diff --git a/pkg/front_end/testcases/inference/top_level_return_and_yield.dart.strong.expect b/pkg/front_end/testcases/inference/top_level_return_and_yield.dart.strong.expect
new file mode 100644
index 0000000000000000000000000000000000000000..51b8de5293e0f6a5b5c9e202afbbe1c5754cb999
--- /dev/null
+++ b/pkg/front_end/testcases/inference/top_level_return_and_yield.dart.strong.expect
@@ -0,0 +1,126 @@
+library test;
+import self as self;
+import "dart:core" as core;
+import "dart:async" as asy;
+
+typedef IntToInt = (core::int) → core::int;
+static method a() → (core::int) → core::int {
+  return (core::int x) → core::int => x;
+}
+static method b() → asy::Future<(core::int) → core::int> /* originally async */ {
+  final asy::Completer<asy::FutureOr<(core::int) → core::int>> :completer = asy::Completer::sync<asy::FutureOr<(core::int) → core::int>>();
+  asy::FutureOr<(core::int) → core::int> :return_value;
+  dynamic :async_op_then;
+  dynamic :async_op_error;
+  dynamic :await_jump_var = 0;
+  dynamic :await_ctx_var;
+  function :async_op([dynamic :result, dynamic :exception, dynamic :stack_trace]) → dynamic yielding 
+    try {
+      #L1:
+      {
+        :return_value = (dynamic x) → dynamic => x;
+        break #L1;
+      }
+      :completer.complete(:return_value);
+      return;
+    }
+    on dynamic catch(dynamic :exception, dynamic :stack_trace) {
+      :completer.completeError(:exception, :stack_trace);
+    }
+  :async_op_then = asy::_asyncThenWrapperHelper(:async_op);
+  :async_op_error = asy::_asyncErrorWrapperHelper(:async_op);
+  asy::Future::microtask<dynamic>(:async_op);
+  return :completer.future;
+}
+static method c() → core::Iterable<(core::int) → core::int> /* originally sync* */ {
+  dynamic :await_jump_var = 0;
+  dynamic :await_ctx_var;
+  function :sync_op(core::Iterator<dynamic> :iterator) → core::bool yielding {
+    {
+      {
+        :iterator._current = (core::int x) → core::int => x;
+        [yield] true;
+      }
+    }
+    return false;
+  }
+  return new core::_SyncIterable::•(:sync_op);
+}
+static method d() → core::Iterable<(core::int) → core::int> /* originally sync* */ {
+  dynamic :await_jump_var = 0;
+  dynamic :await_ctx_var;
+  function :sync_op(core::Iterator<dynamic> :iterator) → core::bool yielding {
+    {
+      {
+        :iterator.isYieldEach = true;
+        :iterator._current = <(core::int) → core::int>[(core::int x) → core::int => x];
+        [yield] true;
+      }
+    }
+    return false;
+  }
+  return new core::_SyncIterable::•(:sync_op);
+}
+static method e() → asy::Stream<(core::int) → core::int> /* originally async* */ {
+  dynamic :controller;
+  dynamic :async_op_then;
+  dynamic :async_op_error;
+  dynamic :await_jump_var = 0;
+  dynamic :await_ctx_var;
+  dynamic :saved_try_context_var0;
+  dynamic :saved_try_context_var1;
+  function :async_op([dynamic :result, dynamic :exception, dynamic :stack_trace]) → dynamic yielding 
+    try
+      try {
+        #L2:
+        {
+          if(:controller.add((core::int x) → core::int => x))
+            return null;
+          else
+            [yield] null;
+        }
+        return;
+      }
+      on dynamic catch(dynamic :exception, dynamic :stack_trace) {
+        :controller.addError(:exception, :stack_trace);
+      }
+    finally {
+      :controller.close();
+    }
+  :async_op_then = asy::_asyncThenWrapperHelper(:async_op);
+  :async_op_error = asy::_asyncErrorWrapperHelper(:async_op);
+  :controller = new asy::_AsyncStarStreamController::•(:async_op);
+  return :controller.stream;
+}
+static method f() → asy::Stream<(core::int) → core::int> /* originally async* */ {
+  dynamic :controller;
+  dynamic :async_op_then;
+  dynamic :async_op_error;
+  dynamic :await_jump_var = 0;
+  dynamic :await_ctx_var;
+  dynamic :saved_try_context_var0;
+  dynamic :saved_try_context_var1;
+  function :async_op([dynamic :result, dynamic :exception, dynamic :stack_trace]) → dynamic yielding 
+    try
+      try {
+        #L3:
+        {
+          if(:controller.addStream(asy::Stream::fromIterable<(core::int) → core::int>(<(core::int) → core::int>[(core::int x) → core::int => x])))
+            return null;
+          else
+            [yield] null;
+        }
+        return;
+      }
+      on dynamic catch(dynamic :exception, dynamic :stack_trace) {
+        :controller.addError(:exception, :stack_trace);
+      }
+    finally {
+      :controller.close();
+    }
+  :async_op_then = asy::_asyncThenWrapperHelper(:async_op);
+  :async_op_error = asy::_asyncErrorWrapperHelper(:async_op);
+  :controller = new asy::_AsyncStarStreamController::•(:async_op);
+  return :controller.stream;
+}
+static method main() → dynamic {}