Add immutable collections hierarchy with runtime/compiler/docs/tests

lynglib/src/commonTest/kotlin/ImmutableCollectionsTest.kt

@@ -0,0 +1,107 @@
+/*
+ * Copyright 2026 Sergey S. Chernov
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+import kotlinx.coroutines.test.runTest
+import net.sergeych.lyng.eval
+import kotlin.test.Test
+import kotlin.test.assertFails
+
+class ImmutableCollectionsTest {
+    @Test
+    fun immutableListSnapshotAndConversion() = runTest {
+        eval(
+            """
+            val src = [1,2,3]
+            val imm = src.toImmutable()
+            assert(imm is ImmutableList<Int>)
+            assert(imm is Array<Int>)
+            assert(imm is Collection<Int>)
+            assert(imm is Iterable<Int>)
+
+            src += 4
+            assertEquals(3, imm.size)
+            assertEquals([1,2,3], imm.toMutable())
+            assertEquals([1,2,3], (1..3).toImmutableList().toMutable())
+            """
+        )
+    }
+
+    @Test
+    fun immutableSetSnapshotAndConversion() = runTest {
+        eval(
+            """
+            val src = Set(1,2,3)
+            val imm = src.toImmutable()
+            assert(imm is ImmutableSet<Int>)
+            assert(imm is Collection<Int>)
+            assert(imm is Iterable<Int>)
+            src += 4
+            assertEquals(3, imm.size)
+            assertEquals(Set(1,2,3), imm.toMutable())
+            assertEquals(Set(1,2,3), [1,2,3].toImmutableSet.toMutable())
+            """
+        )
+    }
+
+    @Test
+    fun immutableMapSnapshotAndConversion() = runTest {
+        eval(
+            """
+            val src = Map("a" => 1, "b" => 2)
+            val imm = src.toImmutable()
+            assert(imm is ImmutableMap<String,Int>)
+            assert(imm is Collection<MapEntry<String,Int>>)
+            assert(imm is Iterable<MapEntry<String,Int>>)
+            src["a"] = 100
+            assertEquals(1, imm["a"])
+            assertEquals(Map("a" => 1, "b" => 2), imm.toMutable())
+
+            val imm2 = ["x" => 10, "y" => 20].toImmutableMap
+            assertEquals(10, imm2["x"])
+            assertEquals(Map("x" => 10, "y" => 20), imm2.toMutable())
+            """
+        )
+    }
+
+    @Test
+    fun immutableCollectionsRejectMutationOps() = runTest {
+        assertFails {
+            eval(
+                """
+                val xs = ImmutableList(1,2,3)
+                xs += 4
+                """
+            )
+        }
+        assertFails {
+            eval(
+                """
+                val s = ImmutableSet(1,2,3)
+                s += 4
+                """
+            )
+        }
+        assertFails {
+            eval(
+                """
+                val m = ImmutableMap("a" => 1)
+                m["a"] = 10
+                """
+            )
+        }
+    }
+}