[kotlin-tooling-core] linearClosure & withLinearClosure: Support loops

KT-54312

libraries/tools/kotlin-tooling-core/src/main/kotlin/org/jetbrains/kotlin/tooling/core/closure.kt

@@ -115,7 +115,7 @@ inline fun <reified T : Any> T.linearClosure(next: (T) -> T?): Set<T> {
     while (enqueued != null) {
         if (enqueued != this && results.add(enqueued)) {
             enqueued = next(enqueued)
-        }
+        } else break
     }
 
     return results
@@ -134,7 +134,7 @@ inline fun <reified T : Any> T.withLinearClosure(next: (T) -> T?): Set<T> {
     while (enqueued != null) {
         if (results.add(enqueued)) {
             enqueued = next(enqueued)
-        }
+        } else break
     }
 
     return results

libraries/tools/kotlin-tooling-core/src/test/kotlin/org/jetbrains/kotlin/tooling/core/ClosureTest.kt

@@ -288,6 +288,21 @@ class ClosureTest {
         )
     }
 
+    @Test
+    fun `linearClosure - loop`() {
+        val a = Node("a")
+        val b = Node("b")
+        val c = Node("c")
+
+        c.parent = b
+        b.parent = a
+        a.parent = c
+
+        assertEquals(
+            listOf("b", "a"), c.linearClosure { it.parent }.map { it.value },
+        )
+    }
+
     @Test
     fun `linearClosure on empty`() {
         assertSame(
@@ -310,6 +325,21 @@ class ClosureTest {
         )
     }
 
+    @Test
+    fun `withLinearClosure - loop`() {
+        val a = Node("a")
+        val b = Node("b")
+        val c = Node("c")
+
+        c.parent = b
+        b.parent = a
+        a.parent = c
+
+        assertEquals(
+            listOf("c", "b", "a"), c.withLinearClosure { it.parent }.map { it.value },
+        )
+    }
+
     @Test
     fun `withLinearClosure on empty`() {
         assertEquals(