From f905aa43ef46b94a51e134889aa1c1ca2475167c Mon Sep 17 00:00:00 2001
From: Jakub Ciesluk <323892@uwr.edu.pl>
Date: Fri, 24 Nov 2023 09:26:08 +0100
Subject: [PATCH] bugfix: Remove incorrect synthetic decorations in partial
 functions

---
 .../pc/PcSyntheticDecorationsProvider.scala    | 11 +++++++++--
 .../tests/pc/SyntheticDecorationsSuite.scala   | 18 ++++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/mtags/src/main/scala-2/scala/meta/internal/pc/PcSyntheticDecorationsProvider.scala b/mtags/src/main/scala-2/scala/meta/internal/pc/PcSyntheticDecorationsProvider.scala
index dfbc95b0a34..42fb9bb68dd 100644
--- a/mtags/src/main/scala-2/scala/meta/internal/pc/PcSyntheticDecorationsProvider.scala
+++ b/mtags/src/main/scala-2/scala/meta/internal/pc/PcSyntheticDecorationsProvider.scala
@@ -157,9 +157,11 @@ final class PcSyntheticDecorationsProvider(
       case dd @ DefDef(_, _, _, _, tpt, _)
           if hasMissingTypeAnnot(dd, tpt) &&
             !dd.symbol.isConstructor &&
-            !dd.symbol.isMutable =>
+            !dd.symbol.isMutable &&
+            !samePosAsOwner(dd.symbol) =>
         Some(dd.symbol.tpe.widen.finalResultType, findTpePos(dd))
-      case bb @ Bind(name, Ident(nme.WILDCARD)) if name != nme.WILDCARD =>
+      case bb @ Bind(name, Ident(nme.WILDCARD))
+          if name != nme.WILDCARD && name != nme.DEFAULT_CASE =>
         Some(bb.symbol.tpe.widen.finalResultType, bb.namePosition)
       case _ => None
     }
@@ -169,6 +171,11 @@ final class PcSyntheticDecorationsProvider(
     private def primaryConstructorParam(sym: Symbol) =
       sym.safeOwner.isPrimaryConstructor
 
+    private def samePosAsOwner(sym: Symbol) = {
+      val owner = sym.safeOwner
+      sym.pos == owner.pos
+    }
+
     private def findTpePos(dd: DefDef) = {
       if (dd.rhs.isEmpty) dd.pos
       else {
diff --git a/tests/cross/src/test/scala/tests/pc/SyntheticDecorationsSuite.scala b/tests/cross/src/test/scala/tests/pc/SyntheticDecorationsSuite.scala
index 105e3f352d2..d43b38059c7 100644
--- a/tests/cross/src/test/scala/tests/pc/SyntheticDecorationsSuite.scala
+++ b/tests/cross/src/test/scala/tests/pc/SyntheticDecorationsSuite.scala
@@ -548,4 +548,22 @@ class SyntheticDecorationsSuite extends BaseSyntheticDecorationsSuite {
        |}
        |""".stripMargin
   )
+
+  check(
+    "partial-fun".tag(IgnoreScalaVersion.forLessThan("2.13.0")),
+    """|object Main {
+       |  List(1).collect { case x => x }
+       |  val x: PartialFunction[Int, Int] = { 
+       |    case 1 => 2 
+       |  }
+       |}
+       |""".stripMargin,
+    """|object Main {
+       |  List[Int](1).collect[Int] { case x: Int => x }
+       |  val x: PartialFunction[Int, Int] = { 
+       |    case 1 => 2 
+       |  }
+       |}
+       |""".stripMargin
+  )
 }