From bdbed61ce90a99d11608b4841998d2c72f7f0ed7 Mon Sep 17 00:00:00 2001
From: Jakub Ciesluk <323892@uwr.edu.pl>
Date: Wed, 20 Mar 2024 18:37:36 +0100
Subject: [PATCH] bugfix: Arg completions on null symbol in Scala 2

---
 .../pc/completions/ArgCompletions.scala       |  8 ++++---
 .../scala/tests/pc/CompletionArgSuite.scala   | 22 +++++++++++++++++++
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/mtags/src/main/scala-2/scala/meta/internal/pc/completions/ArgCompletions.scala b/mtags/src/main/scala-2/scala/meta/internal/pc/completions/ArgCompletions.scala
index bda448b11fe..edc6f60c7ff 100644
--- a/mtags/src/main/scala-2/scala/meta/internal/pc/completions/ArgCompletions.scala
+++ b/mtags/src/main/scala-2/scala/meta/internal/pc/completions/ArgCompletions.scala
@@ -208,9 +208,11 @@ trait ArgCompletions { this: MetalsGlobal =>
     }
 
     override def contribute: List[Member] = {
-      params.distinct.map(param =>
-        new NamedArgMember(param)
-      ) ::: findPossibleDefaults() ::: fillAllFields()
+      if (methodSym == null) Nil
+      else
+        params.distinct.map(param =>
+          new NamedArgMember(param)
+        ) ::: findPossibleDefaults() ::: fillAllFields()
     }
 
     case class MethodParams(params: List[Symbol], isNamed: Set[Name]) {
diff --git a/tests/cross/src/test/scala/tests/pc/CompletionArgSuite.scala b/tests/cross/src/test/scala/tests/pc/CompletionArgSuite.scala
index f35b03a76e8..42bdf5cb13f 100644
--- a/tests/cross/src/test/scala/tests/pc/CompletionArgSuite.scala
+++ b/tests/cross/src/test/scala/tests/pc/CompletionArgSuite.scala
@@ -1216,4 +1216,26 @@ class CompletionArgSuite extends BaseCompletionSuite {
     topLines = Some(1)
   )
 
+  check(
+    "null-symbol",
+    """|object O {
+       |  val t1 = true
+       |  val t2 = true
+       |  val f1 = false
+       |
+       |  (t1, t2, f1) match {
+       |    case (_, false, false) => prinl=t@@n()
+       |    case (true, _, true) => println("KO")
+       |    case _ => println("OK")
+       |  }
+       |}
+       |""".stripMargin,
+    "",
+    compat = Map(
+      "3" -> """|t1: Boolean
+                |""".stripMargin
+    ),
+    topLines = Some(1)
+  )
+
 }