Fix argument priority handling in ObjInstance resolution logic and add corresponding tests

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Scope.kt

@@ -347,7 +347,16 @@ open class Scope(
         // 1. Prefer direct locals/bindings declared in this frame
         tryGetLocalRecord(this, name, currentClassCtx)?.let { return it }
 
-        // 2. Then, check members of thisObj
+        val p = parent
+
+        // 2. If we share thisObj with parent, delegate to parent to maintain
+        // "locals shadow members" priority across the this-context.
+        if (p != null && p.thisObj === thisObj) {
+            return p.get(name)
+        }
+
+        // 3. Otherwise, we are the "primary" scope for this thisObj (or have no parent),
+        // so check members of thisObj before walking up to a different this-context.
         val receiver = thisObj
         val effectiveClass = receiver as? ObjClass ?: receiver.objClass
         for (cls in effectiveClass.mro) {
@@ -365,8 +374,8 @@ open class Scope(
             }
         }
 
-        // 3. Finally, walk up ancestry
-        return parent?.get(name)
+        // 4. Finally, walk up ancestry to a scope with a different thisObj context
+        return p?.get(name)
     }
 
     // Slot fast-path API

lynglib/src/commonMain/kotlin/net/sergeych/lyng/obj/ObjInstance.kt

@@ -76,6 +76,7 @@ class ObjInstance(override val objClass: ObjClass) : Obj() {
     }
 
     override suspend fun resolveRecord(scope: Scope, obj: ObjRecord, name: String, decl: ObjClass?): ObjRecord {
+        if (obj.type.isArgument) return super.resolveRecord(scope, obj, name, decl)
         if (obj.type == ObjRecord.Type.Delegated) {
             val d = decl ?: obj.declaringClass
             val storageName = "${d?.className}::$name"

lynglib/src/commonTest/kotlin/OOTest.kt

@@ -20,6 +20,7 @@ import net.sergeych.lyng.Script
 import net.sergeych.lyng.eval
 import net.sergeych.lyng.obj.ObjInstance
 import net.sergeych.lyng.obj.ObjList
+import net.sergeych.lyng.toSource
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFails
@@ -731,4 +732,48 @@ class OOTest {
             """.trimIndent())
     }
 
+    @Test
+    fun testArgsPriority() = runTest {
+        eval("""
+            class A(id) {
+                var stored = null
+                // Arguments should have priority on
+                // instance fields
+                fun setStored(id) { stored = id }
+            }
+            val a = A(1)
+            assertEquals(1, a.id)
+            assertEquals(null, a.stored)
+            
+            // Check that arguments of the call have the priority:
+            a.setStored(2)
+            assertEquals(1, a.id)
+            assertEquals(2, a.stored)
+        """.trimIndent())
+    }
+
+    /**
+     * Demonstrates that function parameters are shadowed by class methods of the same name
+     * when accessed within a block, but not in a single expression.
+     */
+    @Test
+    fun testParameterShadowingConflict() = runTest {
+        val scope = Script.newScope()
+        val result = scope.eval("""
+            class Tester() {
+                fun id() { "method" }
+                // This correctly returns "success"
+                fun checkOk(id) = id
+                // This incorrectly returns the 'id' method (a Callable) instead of "success"
+                fun checkFail(id) {
+                    id
+                }
+            }
+            val t = Tester()
+            if (t.checkOk("success") != "success") throw "checkOk failed"
+            t.checkFail("success")
+        """.trimIndent().toSource("repro"))
+
+        assertEquals("success", result.toString(), "Parameter 'id' should shadow method 'id' in block")
+    }
 }