Fix for 'returnType' when extract a method with a single expression.

pkg/analysis_server/test/services/refactoring/extract_method_test.dart

Index: pkg/analysis_server/test/services/refactoring/extract_method_test.dart
diff --git a/pkg/analysis_server/test/services/refactoring/extract_method_test.dart b/pkg/analysis_server/test/services/refactoring/extract_method_test.dart
index e039419e8e5dd5f2357470646e670f09945b0994..39d38556129dbd334a9659a71d7cb957a192dd0b 100644
--- a/pkg/analysis_server/test/services/refactoring/extract_method_test.dart
+++ b/pkg/analysis_server/test/services/refactoring/extract_method_test.dart
@@ -1032,11 +1032,9 @@ main() {
   test_offsets_lengths() {
     indexTestUnit('''
 main() {
-main() {
   int a = 1 + 2;
   int b = 1 +  2;
 }
-}
 ''');
     _createRefactoringForString('1 +  2');
     // apply refactoring
@@ -1048,6 +1046,50 @@ main() {
     });
   }
 
+  test_returnType_expression() {
+    indexTestUnit('''
+main() {
+  int a = 1 + 2;
+}
+''');
+    _createRefactoringForString('1 + 2');
+    // do check
+    return refactoring.checkInitialConditions().then((_) {
+      expect(refactoring.returnType, 'int');
+    });
+  }
+
+  test_returnType_statements() {
+    indexTestUnit('''
+main() {
+// start
+  double v = 5.0;
+// end
+  print(v);
+}
+''');
+    _createRefactoringForStartEndComments();
+    // do check
+    return refactoring.checkInitialConditions().then((_) {
+      expect(refactoring.returnType, 'double');
+    });
+  }
+
+  test_returnType_statements_void() {
+    indexTestUnit('''
+main() {
+// start
+  print(42);
+// end
+}
+''');
+    _createRefactoringForStartEndComments();
+    // do check
+    return refactoring.checkInitialConditions().then((_) {
+      expect(refactoring.returnType, 'void');
+    });
+  }
+
   test_setExtractGetter() {
     indexTestUnit('''
 main() {