Minor, fix KotlinSignature of DFS methods

compiler/backend-common/src/bridges/bridges.kt

@@ -71,14 +71,14 @@ public fun <Function : FunctionHandle, Signature> generateBridges(
 
 private fun <Function : FunctionHandle> findAllReachableDeclarations(function: Function): MutableSet<Function> {
     val collector = object : DFS.NodeHandlerWithListResult<Function, Function>() {
-        override fun afterChildren(current: Function?) {
-            if (current != null && current.isDeclaration) {
+        override fun afterChildren(current: Function) {
+            if (current.isDeclaration) {
                 result.add(current)
             }
         }
     }
     [suppress("UNCHECKED_CAST")]
-    DFS.dfs(listOf(function), { it!!.getOverridden() as Iterable<Function> }, collector)
+    DFS.dfs(listOf(function), { it.getOverridden() as Iterable<Function> }, collector)
     return HashSet(collector.result())
 }
 

compiler/tests/org/jetbrains/jet/codegen/BridgeTest.kt

@@ -75,13 +75,13 @@ class BridgeTest : TestCase() {
 
         fun findAllReachableDeclarations(from: Fun): MutableSet<Fun> {
             val handler = object : DFS.NodeHandlerWithListResult<Fun, Fun>() {
-                override fun afterChildren(current: Fun?) {
-                    if (current!!.isDeclaration) {
+                override fun afterChildren(current: Fun) {
+                    if (current.isDeclaration) {
                         result.add(current)
                     }
                 }
             }
-            DFS.dfs(listOf(from), { it!!.getOverridden() }, handler)
+            DFS.dfs(listOf(from), { it.getOverridden() }, handler)
             val result = HashSet(handler.result())
             result.remove(from)
             return result

core/util.runtime/src/org/jetbrains/jet/utils/DFS.java

@@ -79,16 +79,17 @@ public class DFS {
     }
 
     public interface NodeHandler<N, R> {
-
+        @KotlinSignature("fun beforeChildren(current: N): Unit")
         void beforeChildren(N current);
 
+        @KotlinSignature("fun afterChildren(current: N): Unit")
         void afterChildren(N current);
 
         R result();
     }
 
     public interface Neighbors<N> {
-        @KotlinSignature("fun getNeighbors(current: N?): Iterable<N>")
+        @KotlinSignature("fun getNeighbors(current: N): Iterable<N>")
         @NotNull
         Iterable<N> getNeighbors(N current);
     }