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

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

+library test;
+import self as self;
+import "dart:core" as core;
+import "dart:async" as asy;
+
+typedef IntToInt = (core::int) → core::int;
+static method main() → dynamic {
+  function a() → (core::int) → core::int {
+    return (core::int x) → core::int => x;
+  }
+  function 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;
+  }
+  function 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);
+  }
+  function 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);
+  }
+  function 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;
+  }
+  function 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;
+  }
+}