guava type migration: method parameter migration involves local variables migration if need

java/typeMigration/src/com/intellij/refactoring/typeMigration/rules/guava/GuavaFluentIterableConversionRule.java

@@ -29,7 +29,6 @@ import com.intellij.refactoring.typeMigration.TypeConversionDescriptor;
 import com.intellij.refactoring.typeMigration.TypeConversionDescriptorBase;
 import com.intellij.refactoring.typeMigration.TypeMigrationLabeler;
 import com.intellij.refactoring.typeMigration.rules.TypeConversionRule;
-import com.intellij.util.Function;
 import com.intellij.util.IncorrectOperationException;
 import com.intellij.util.SmartList;
 import com.intellij.util.containers.ContainerUtil;
@@ -306,6 +305,10 @@ public class GuavaFluentIterableConversionRule extends BaseGuavaTypeConversionRu
         }
         break;
       }
+      else if (qualifier instanceof PsiReferenceExpression && ((PsiReferenceExpression)qualifier).resolve() instanceof PsiVariable) {
+        labeler.migrateExpressionType(qualifier, to, qualifier.getParent(), false, false);
+        break;
+      }
       else {
         return null;
       }

java/typeMigration/test/com/intellij/codeInsight/inspections/GuavaInspectionTest.java

@@ -182,6 +182,10 @@ public class GuavaInspectionTest extends JavaCodeInsightFixtureTestCase {
     doTest();
   }
 
+  public void testTypeMigrationRootBackTraverse() {
+    doTest();
+  }
+
   private void doTestNoQuickFixes(final Class<? extends IntentionAction>... quickFixesClasses) {
     myFixture.configureByFile(getTestName(true) + ".java");
     myFixture.enableInspections(new GuavaInspection());

java/typeMigration/testData/inspections/guava/typeMigrationRootBackTraverse.java

@@ -0,0 +1,17 @@
+import com.google.common.collect.FluentIterable;
+
+import java.util.ArrayList;
+
+public class MainFluentIterable {
+
+  FluentIter<caret>able<String> m2() {
+
+    FluentIterable<String> it = FluentIterable.from(new ArrayList<String>());
+
+    return it.transform(s -> s + s);
+  }
+
+  void m3() {
+    System.out.println((int) m2().size());
+  }
+}

java/typeMigration/testData/inspections/guava/typeMigrationRootBackTraverse_after.java

@@ -0,0 +1,16 @@
+import java.util.ArrayList;
+import java.util.stream.Stream;
+
+public class MainFluentIterable {
+
+  Stream<String> m2() {
+
+    Stream<String> it = new ArrayList<String>().stream();
+
+    return it.map(s -> s + s);
+  }
+
+  void m3() {
+    System.out.println((int) (int) m2().count());
+  }
+}