introduce variable: distinguish lambda parameters but allow param free expressions (IDEA-163785)

java/java-tests/testData/refactoring/introduceVariable/DistinguishLambdaParams.after.java

@@ -0,0 +1,15 @@
+import java.util.function.UnaryOperator;
+
+class Main {
+  public static void main(String[] args) {
+    UnaryOperator<String> f1 = s -> {
+      System.out.println("foo");
+        String temp = s.trim();
+        return temp;
+    };
+    UnaryOperator<String> f2 = s -> {
+      System.out.println("foo");
+      return s.trim();
+    };
+  }
+}

java/java-tests/testData/refactoring/introduceVariable/DistinguishLambdaParams.java

@@ -0,0 +1,14 @@
+import java.util.function.UnaryOperator;
+
+class Main {
+  public static void main(String[] args) {
+    UnaryOperator<String> f1 = s -> {
+      System.out.println("foo");
+      return <selection>s.trim()</selection>;
+    };
+    UnaryOperator<String> f2 = s -> {
+      System.out.println("foo");
+      return s.trim();
+    };
+  }
+}