extern generics classes fix, documentation on extern classes updated

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

@@ -7727,7 +7727,6 @@ class Compiler(
 
         val annotation = lastAnnotation
         val parentContext = codeContexts.last()
-        val parentClassCtx = parentContext as? CodeContext.ClassBody
 
         // Is extension?
         if (looksLikeExtensionReceiver()) {
@@ -7761,13 +7760,6 @@ class Compiler(
             name = t.value
             nameStartPos = t.pos
         }
-        if (parentClassCtx?.isExtern == true && !isExtern) {
-            val owner = parentClassCtx.name
-            throw ScriptError(
-                nameStartPos,
-                "member '$name' in extern class/object '$owner' must be declared extern (use `extern fun $name(...)`)"
-            )
-        }
         val extensionWrapperName = extTypeName?.let { extensionCallableName(it, name) }
         val classCtx = codeContexts.asReversed().firstOrNull { it is CodeContext.ClassBody } as? CodeContext.ClassBody
         var memberMethodId = if (extTypeName == null) classCtx?.memberMethodIds?.get(name) else null
@@ -8790,16 +8782,6 @@ class Compiler(
             name = nameToken.value
             nameStartPos = nameToken.pos
         }
-        val parentClassCtx = codeContexts.lastOrNull() as? CodeContext.ClassBody
-        if (parentClassCtx?.isExtern == true && !isExtern) {
-            val owner = parentClassCtx.name
-            val kind = if (isMutable) "var" else "val"
-            throw ScriptError(
-                nameStartPos,
-                "member '$name' in extern class/object '$owner' must be declared extern (use `extern $kind $name: ...`)"
-            )
-        }
-
         val receiverNormalization = normalizeReceiverTypeDecl(receiverTypeDecl, emptySet())
         val implicitTypeParams = receiverNormalization.second
         if (implicitTypeParams.isNotEmpty()) pendingTypeParamStack.add(implicitTypeParams)

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bridge/ClassBridge.kt

@@ -51,8 +51,9 @@ interface BridgeInstanceContext {
  * Use [LyngClassBridge.bind] to obtain a binder and register implementations.
  * Bindings must happen before the first instance of the class is created.
  *
- * Important: members you bind here must be declared as `extern` in Lyng so the
- * compiler emits the ABI slots that Kotlin bindings attach to.
+ * Important: members you bind here must be extern in Lyng (explicitly, or
+ * implicitly by being inside `extern class` / `extern object`) so the compiler
+ * emits the ABI slots that Kotlin bindings attach to.
  */
 interface ClassBridgeBinder {
     /** Arbitrary Kotlin-side data attached to the class. */
@@ -70,7 +71,7 @@ interface ClassBridgeBinder {
         replaceWith = ReplaceWith("initWithInstance { block(this, thisObj) }")
     )
     fun initWithInstance(block: suspend (ScopeFacade, Obj) -> Unit)
-    /** Bind a Lyng function/member to a Kotlin implementation (requires `extern` in Lyng). */
+    /** Bind a Lyng function/member to a Kotlin implementation (requires extern member in Lyng). */
     fun addFun(name: String, impl: suspend ScopeFacade.() -> Obj)
     /**
      * Legacy addFun form.
@@ -81,7 +82,7 @@ interface ClassBridgeBinder {
         replaceWith = ReplaceWith("addFun(name) { impl(this, thisObj, args) }")
     )
     fun addFun(name: String, impl: suspend (ScopeFacade, Obj, Arguments) -> Obj)
-    /** Bind a read-only member (val/property getter) declared as `extern`. */
+    /** Bind a read-only member (val/property getter) declared extern in Lyng. */
     fun addVal(name: String, impl: suspend ScopeFacade.() -> Obj)
     /**
      * Legacy addVal form.
@@ -92,7 +93,7 @@ interface ClassBridgeBinder {
         replaceWith = ReplaceWith("addVal(name) { impl(this, thisObj) }")
     )
     fun addVal(name: String, impl: suspend (ScopeFacade, Obj) -> Obj)
-    /** Bind a mutable member (var/property getter/setter) declared as `extern`. */
+    /** Bind a mutable member (var/property getter/setter) declared extern in Lyng. */
     fun addVar(
         name: String,
         get: suspend ScopeFacade.() -> Obj,
@@ -119,8 +120,9 @@ interface ClassBridgeBinder {
  * Entry point for Kotlin bindings to declared Lyng classes.
  *
  * The workflow is Lyng-first: declare the class and its members in Lyng,
- * then bind the implementations from Kotlin. Bound members must be marked
- * `extern` so the compiler emits the ABI slots for Kotlin to attach to.
+ * then bind the implementations from Kotlin. Bound members must be extern
+ * (explicitly or by enclosing `extern class` / `extern object`) so the compiler
+ * emits the ABI slots for Kotlin to attach to.
  */
 object LyngClassBridge {
     /**
@@ -212,7 +214,7 @@ object LyngObjectBridge {
 /**
  * Sugar for [LyngClassBridge.bind] on a module scope.
  *
- * Bound members must be declared as `extern` in Lyng.
+ * Bound members must be extern in Lyng (explicitly or via enclosing extern class/object).
  */
 suspend fun ModuleScope.bind(
     className: String,
@@ -222,7 +224,7 @@ suspend fun ModuleScope.bind(
 /**
  * Sugar for [LyngObjectBridge.bind] on a module scope.
  *
- * Bound members must be declared as `extern` in Lyng.
+ * Bound members must be extern in Lyng (explicitly or via enclosing extern class/object).
  */
 suspend fun ModuleScope.bindObject(
     objectName: String,

lynglib/src/commonTest/kotlin/ScriptTest.kt

@@ -30,8 +30,8 @@ import kotlinx.serialization.json.JsonPrimitive
 import kotlinx.serialization.json.encodeToJsonElement
 import net.sergeych.lyng.*
 import net.sergeych.lyng.obj.*
-import net.sergeych.lyng.thisAs
 import net.sergeych.lyng.pacman.InlineSourcesImportProvider
+import net.sergeych.lyng.thisAs
 import net.sergeych.mp_tools.globalDefer
 import net.sergeych.tools.bm
 import kotlin.test.*
@@ -3097,19 +3097,6 @@ class ScriptTest {
         )
     }
 
-    @Test
-    fun testExternClassMembersMustBeExplicitlyExtern() = runTest {
-        assertFailsWith<ScriptError> {
-            eval(
-                """
-                extern class HostClass {
-                    fun doSomething(): Int
-                }
-                """.trimIndent()
-            )
-        }
-    }
-
     @Test
     fun testExternExtension() = runTest {
         eval(

lynglib/src/commonTest/kotlin/TypesTest.kt

@@ -621,24 +621,23 @@ class TypesTest {
         eval("""
             extern fun f<T>(x: T): T 
             extern class Cell<T> {
-                extern var value: T
+                var value: T
             }
         """)
     }
 
     @Test
-    fun testExternClassMemberMustBeExternMessage() = runTest {
+    fun testExternClassMemberInitializerStillFailsWithoutExplicitExtern() = runTest {
         val e = assertFailsWith<ScriptError> {
             eval(
                 """
                 extern class Cell<T> {
-                    var value: T
+                    var value: T = 1
                 }
                 """.trimIndent()
             )
         }
-        assertTrue(e.message?.contains("must be declared extern") == true)
-        assertTrue(e.message?.contains("extern var value") == true)
+        assertTrue(e.message?.contains("extern variable value cannot have an initializer or delegate") == true)
     }
 
 //    @Test fun nonTrivialOperatorsTest() = runTest {