From 066101a1a748091daa0f1b9fff466fb0276d250b Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Sat, 14 Sep 2024 19:48:23 +0200
Subject: [PATCH] Fix treatment of separately compiled @native methods in
 FirstTransform

We need to use a SymTransformer, fixing the method in the tree is not enough.
---
 .../src/dotty/tools/dotc/core/Flags.scala     |  1 +
 .../tools/dotc/transform/FirstTransform.scala | 26 +++++++++++--------
 tests/pos/i20588/Baz_2.scala                  |  1 +
 tests/pos/i20588/Foo_1.scala                  |  3 +++
 4 files changed, 20 insertions(+), 11 deletions(-)
 create mode 100644 tests/pos/i20588/Baz_2.scala
 create mode 100644 tests/pos/i20588/Foo_1.scala

diff --git a/compiler/src/dotty/tools/dotc/core/Flags.scala b/compiler/src/dotty/tools/dotc/core/Flags.scala
index b1bf7a266c91..b915373da021 100644
--- a/compiler/src/dotty/tools/dotc/core/Flags.scala
+++ b/compiler/src/dotty/tools/dotc/core/Flags.scala
@@ -569,6 +569,7 @@ object Flags {
   val ConstructorProxyModule: FlagSet        = ConstructorProxy | Module
   val DefaultParameter: FlagSet              = HasDefault | Param                             // A Scala 2x default parameter
   val DeferredInline: FlagSet                = Deferred | Inline
+  val DeferredMethod: FlagSet                = Deferred | Method
   val DeferredOrLazy: FlagSet                = Deferred | Lazy
   val DeferredOrLazyOrMethod: FlagSet        = Deferred | Lazy | Method
   val DeferredOrTermParamOrAccessor: FlagSet = Deferred | ParamAccessor | TermParam           // term symbols without right-hand sides
diff --git a/compiler/src/dotty/tools/dotc/transform/FirstTransform.scala b/compiler/src/dotty/tools/dotc/transform/FirstTransform.scala
index b5bc43ee762c..c66e6b9471cb 100644
--- a/compiler/src/dotty/tools/dotc/transform/FirstTransform.scala
+++ b/compiler/src/dotty/tools/dotc/transform/FirstTransform.scala
@@ -14,6 +14,7 @@ import Decorators.*
 import scala.collection.mutable
 import DenotTransformers.*
 import NameOps.*
+import SymDenotations.SymDenotation
 import NameKinds.OuterSelectName
 import StdNames.*
 import config.Feature
@@ -35,22 +36,26 @@ object FirstTransform {
  *          if (true) A else B    ==> A
  *          if (false) A else B   ==> B
  */
-class FirstTransform extends MiniPhase with InfoTransformer { thisPhase =>
+class FirstTransform extends MiniPhase with SymTransformer { thisPhase =>
   import ast.tpd.*
 
   override def phaseName: String = FirstTransform.name
 
   override def description: String = FirstTransform.description
 
-  /** eliminate self symbol in ClassInfo */
-  override def transformInfo(tp: Type, sym: Symbol)(using Context): Type = tp match {
-    case tp @ ClassInfo(_, _, _, _, self: Symbol) =>
-      tp.derivedClassInfo(selfInfo = self.info)
-    case _ =>
-      tp
-  }
-
-  override protected def infoMayChange(sym: Symbol)(using Context): Boolean = sym.isClass
+  /** eliminate self symbol in ClassInfo, reset Deferred for @native methods */
+  override def transformSym(sym: SymDenotation)(using Context): SymDenotation =
+    if sym.isClass then
+      sym.info match
+        case tp @ ClassInfo(_, _, _, _, self: Symbol) =>
+          val info1 = tp.derivedClassInfo(selfInfo = self.info)
+          sym.copySymDenotation(info = info1).copyCaches(sym, ctx.phase.next)
+        case _ =>
+          sym
+    else if sym.isAllOf(DeferredMethod) && sym.hasAnnotation(defn.NativeAnnot) then
+      sym.copySymDenotation(initFlags = sym.flags &~ Deferred)
+    else
+      sym
 
   override def checkPostCondition(tree: Tree)(using Context): Unit =
     tree match {
@@ -121,7 +126,6 @@ class FirstTransform extends MiniPhase with InfoTransformer { thisPhase =>
   override def transformDefDef(ddef: DefDef)(using Context): Tree =
     val meth = ddef.symbol.asTerm
     if meth.hasAnnotation(defn.NativeAnnot) then
-      meth.resetFlag(Deferred)
       DefDef(meth, _ =>
         ref(defn.Sys_error.termRef).withSpan(ddef.span)
           .appliedTo(Literal(Constant(s"native method stub"))))
diff --git a/tests/pos/i20588/Baz_2.scala b/tests/pos/i20588/Baz_2.scala
new file mode 100644
index 000000000000..7dbb038d38da
--- /dev/null
+++ b/tests/pos/i20588/Baz_2.scala
@@ -0,0 +1 @@
+class Baz extends Foo
diff --git a/tests/pos/i20588/Foo_1.scala b/tests/pos/i20588/Foo_1.scala
new file mode 100644
index 000000000000..1f99cba7ff1c
--- /dev/null
+++ b/tests/pos/i20588/Foo_1.scala
@@ -0,0 +1,3 @@
+class Foo {
+  @native def test(): Unit
+}