Fix multiline list parsing and expose actionable HTTP failures

lynglib/src/commonTest/kotlin/MultilineListLiteralTest.kt

@@ -0,0 +1,21 @@
+import kotlinx.coroutines.test.runTest
+import net.sergeych.lyng.Script
+import kotlin.test.*
+
+class MultilineListLiteralTest {
+    @Test fun finalNewlineCommentsAndTrailingCommaAreWhitespace() = runTest {
+        val scope = Script.newScope()
+        for (source in listOf(
+            "[\n \"first\",\n \"second\"\n]",
+            "[\n \"first\",\n \"second\",\n]",
+            "[\n // before\n \"first\", /* between */\n \"second\" // after\n]",
+        )) assertEquals("[first,second]", scope.eval(source).toString(scope).value)
+    }
+    @Test fun nestedAndEmptyMultilineListsAndExpressionsRemainValid() = runTest {
+        val scope = Script.newScope()
+        assertEquals("[]", scope.eval("[\n]").toString(scope).value)
+        assertEquals("[[1,2],[3,4]]", scope.eval("[\n [1,2],\n [3,4]\n]").toString(scope).value)
+        assertEquals("[3,7]", scope.eval("[\n 1+2,\n 3+4\n]").toString(scope).value)
+        assertFails { scope.eval("[\n @\n]") }
+    }
+}