Bugfix. EMPTY_BLOCK_STRUCTURE_ERROR shouldn't trigger on empty lambdas

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/rules/chapter3/EmptyBlock.kt

@@ -34,9 +34,6 @@ class EmptyBlock(configRules: List<RulesConfig>) : DiktatRule(
         val configuration = EmptyBlockStyleConfiguration(
             configRules.getRuleConfig(EMPTY_BLOCK_STRUCTURE_ERROR)?.configuration ?: emptyMap()
         )
-        if (node.elementType == FILE) {
-            println(node.prettyPrint())
-        }
         searchNode(node, configuration)
     }
 
@@ -106,16 +103,19 @@ class EmptyBlock(configRules: List<RulesConfig>) : DiktatRule(
     @Suppress("UnsafeCallOnNullableType")
     private fun isLambdaUsedAsFunction(node: ASTNode): Boolean {
         val parents = node.parents()
-        if (parents.any { it.elementType == CALL_EXPRESSION }) {
-            val callExpression = parents.find { it.elementType == CALL_EXPRESSION }!!
-            // excepting cases like list.map { }
-            return callExpression.treeParent.elementType != DOT_QUALIFIED_EXPRESSION
-        } else if (parents.any { it.elementType == LAMBDA_EXPRESSION }) {
-            val lambdaExpression = parents.find { it.elementType == LAMBDA_EXPRESSION }!!
-            // cases like A({}). Here Lambda expression is used as a value parameter.
-            return lambdaExpression.treeParent.elementType == VALUE_PARAMETER
+        return when {
+            parents.any { it.elementType == CALL_EXPRESSION } -> {
+                val callExpression = parents.find { it.elementType == CALL_EXPRESSION }!!
+                // excepting cases like list.map { }
+                callExpression.treeParent.elementType != DOT_QUALIFIED_EXPRESSION
+            }
+            parents.any { it.elementType == LAMBDA_EXPRESSION } -> {
+                val lambdaExpression = parents.find { it.elementType == LAMBDA_EXPRESSION }!!
+                // cases like A({}). Here Lambda expression is used as a value parameter.
+                lambdaExpression.treeParent.elementType == VALUE_PARAMETER
+            }
+            else -> false
         }
-        return false
     }
 
     /**

info/guide/guide-chapter-3.md

@@ -1,4 +1,4 @@
-# <a name="c3"></a>3. General formatting (typesetting)
+__# <a name="c3"></a>3. General formatting (typesetting)
 <!-- =============================================================================== -->
 ### <a name="c3.1"></a> 3.1 File-related rules
 This section describes the rules related to using files in your code.
@@ -305,7 +305,7 @@ class A
 Avoid empty blocks, and ensure braces start on a new line. An empty code block can be closed immediately on the same line and the next line. However, a newline is recommended between opening and closing braces `{}` (see the examples below.)
 
 Generally, empty code blocks are prohibited; using them is considered a bad practice (especially for catch block).
-They are only appropriate for overridden functions when the base class's functionality is not needed in the class-inheritor.
+They are appropriate for overridden functions, when the base class's functionality is not needed in the class-inheritor, for lambdas used as a function and for empty function in implementation of functional interface. 
 ```kotlin
 override fun foo() {    
 }
@@ -318,6 +318,8 @@ fun doNothing() {}
 
 fun doNothingElse() {
 }
+
+fun foo(bar: () -> Unit = {})__
 ```
 
 **Invalid examples:**