fix: correctly prefix scope completions when conflicting for Scala 2

mtags/src/main/scala-2/scala/meta/internal/pc/CompletionProvider.scala

@@ -3,6 +3,7 @@ package scala.meta.internal.pc
 import java.net.URI
 import java.{util => ju}
 
+import scala.annotation.tailrec
 import scala.collection.mutable
 
 import scala.meta.internal.jdk.CollectionConverters._
@@ -73,10 +74,34 @@ class CompletionProvider(
     lazy val importPosition = autoImportPosition(pos, params.text())
     lazy val context = doLocateImportContext(pos)
 
+    @tailrec
+    def findNonConflictingPrefix(sym: Symbol, acc: List[String]): String = {
+      val symName = if (sym.name.isTermName) sym.name.dropLocal else sym.name
+      context.lookupSymbol(symName, _ => true) match {
+        case LookupSucceeded(_, symbol)
+            if sym.effectiveOwner.exists && symbol.effectiveOwner.exists && symbol.effectiveOwner != sym.effectiveOwner =>
+          findNonConflictingPrefix(
+            sym.effectiveOwner,
+            Identifier.backtickWrap(sym.effectiveOwner.name.decoded) :: acc
+          )
+        case _ => acc.mkString(".")
+      }
+    }
+
     val items = sorted.iterator.zipWithIndex.map { case (member, idx) =>
       params.checkCanceled()
       val symbolName = member.symNameDropLocal.decoded
-      val ident = Identifier.backtickWrap(symbolName)
+      val simpleIdent = Identifier.backtickWrap(symbolName)
+      val ident =
+        member match {
+          case _: WorkspaceMember | _: WorkspaceImplicitMember |
+              _: NamedArgMember | _: DependecyMember =>
+            simpleIdent
+          case _: ScopeMember =>
+            findNonConflictingPrefix(member.sym, List(simpleIdent))
+          case _ => simpleIdent
+        }
+
       val detail = member match {
         case o: OverrideDefMember => o.detail
         case t: TextEditMember if t.detail.isDefined => t.detail.get

tests/cross/src/test/scala/tests/pc/CompletionSuite.scala

@@ -2325,4 +2325,47 @@ class CompletionSuite extends BaseCompletionSuite {
     filter = _ == "O(i: Int): Int"
   )
 
+  check(
+    "conflict",
+    """|package a
+       |object O {
+       |  val x: Int = 123
+       |  def method = {
+       |    val x: String = "abc"
+       |    x@@
+       |  }
+       |}
+       |""".stripMargin,
+    """|x: String
+       |O.x: Int
+       |""".stripMargin,
+    compat = Map(
+      "3" -> """|x: String
+                |x: Int
+                |""".stripMargin
+    )
+  )
+
+  checkEdit(
+    "conflict-edit",
+    """|object O {
+       |  val x: Int = 123
+       |  def method = {
+       |    val x: String = "abc"
+       |    x@@
+       |  }
+       |}
+       |""".stripMargin,
+    """|object O {
+       |  val x: Int = 123
+       |  def method = {
+       |    val x: String = "abc"
+       |    O.x
+       |  }
+       |}
+       |""".stripMargin,
+    assertSingleItem = false,
+    itemIndex = 1
+  )
+
 }