extract method: suggest return type by unique variable defined in extracted code (IDEA-108296)

java/java-tests/testData/refactoring/extractMethod/MakeVoidMethodReturnVariable.java

@@ -0,0 +1,5 @@
+class X {
+  void foo() {
+      <selection>int x = 0;</selection>
+  }
+}

java/java-tests/testData/refactoring/extractMethod/MakeVoidMethodReturnVariable_after.java

@@ -0,0 +1,10 @@
+class X {
+  void foo() {
+      int x = newMethod();
+  }
+
+    private int newMethod() {
+        int x = 0;
+        return x;
+    }
+}

java/java-tests/testData/refactoring/extractMethod/MultipleVarsInMethodNoReturnStatementAndAssignment.java

@@ -0,0 +1,7 @@
+class X {
+  void foo() {
+      <selection>int x = 0;
+      int y = 42;
+      </selection>
+  }
+}

java/java-tests/testData/refactoring/extractMethod/MultipleVarsInMethodNoReturnStatementAndAssignment_after.java

@@ -0,0 +1,11 @@
+class X {
+  void foo() {
+      newMethod();
+      
+  }
+
+    private int newMethod() {
+        int x = 0;
+        int y = 42;
+    }
+}