bugfix: hover for select chains ending with function Scala 2 (#5883)

mtags/src/main/scala-2/scala/meta/internal/pc/completions/Completions.scala

@@ -711,6 +711,12 @@ trait Completions { this: MetalsGlobal =>
           // for named args apply becomes transparent but fun doesn't
           case Apply(fun, args) =>
             !fun.pos.isTransparent && args.forall(_.pos.isOffset)
+          // for synthetic val definition select on it becomes transparent
+          case sel @ Select(qual: Ident, _) =>
+            val qualifierIsSyntheticVal =
+              Option(qual.symbol).exists(sym => sym.isValue && sym.isSynthetic)
+            qualifierIsSyntheticVal &&
+            !sel.namePosition.isTransparent && sel.namePosition.encloses(pos)
           case _ => false
         }
       }
@@ -728,6 +734,11 @@ trait Completions { this: MetalsGlobal =>
             super.traverse(t)
           } else {
             t match {
+              // workaround for Scala 2.13,
+              // where position is not set properly for synthetic val definition
+              // we are interested only in its children, which have correct positions set
+              case v: ValDef if v.pos.isOffset && v.symbol.isSynthetic =>
+                super.traverse(v)
               case mdef: MemberDef =>
                 val annTrees = mdef.mods.annotations match {
                   case Nil if mdef.symbol != null =>

tests/cross/src/test/scala/tests/hover/HoverTermSuite.scala

@@ -520,7 +520,45 @@ class HoverTermSuite extends BaseHoverSuite {
   )
 
   check(
-    "apply-chain".tag(IgnoreScala2),
+    "function-chain",
+    """
+      |trait Consumer {
+      |  def subConsumer: Consumer
+      |  def consume(value: Int): Unit
+      |}
+      |
+      |object O {
+      |  val consumer: Consumer = ???
+      |  List(1).foreach(<<consumer.subConsumer.co@@nsume>>)
+      |}
+      |""".stripMargin,
+    """|```scala
+       |def consume(value: Int): Unit
+       |```
+       |""".stripMargin
+  )
+
+  check(
+    "function-chain2",
+    """
+      |trait Consumer {
+      |  def subConsumer: Consumer
+      |  def consume(value: Int): Unit
+      |}
+      |
+      |object O {
+      |  val consumer: Consumer = ???
+      |  List(1).foreach(<<cons@@umer>>.subConsumer.consume)
+      |}
+      |""".stripMargin,
+    """|```scala
+       |val consumer: Consumer
+       |```
+       |""".stripMargin
+  )
+
+  check(
+    "function-chain3",
     """
       |trait Consumer {
       |  def subConsumer: Consumer
@@ -529,7 +567,7 @@ class HoverTermSuite extends BaseHoverSuite {
       |
       |object O {
       |  val consumer: Consumer = ???
-      |  val m = consumer.subConsumer.<<co@@nsume>>
+      |  List(1).foreach(<<consumer.subConsumer.subConsumer.con@@sume>>)
       |}
       |""".stripMargin,
     """|```scala
@@ -538,4 +576,49 @@ class HoverTermSuite extends BaseHoverSuite {
        |""".stripMargin
   )
 
+  check(
+    "function-chain4",
+    """
+      |trait Consumer {
+      |  def subConsumer[T](i: T): T
+      |  def consume(value: Int)(n: Int): Unit
+      |}
+      |
+      |object O {
+      |  val consumer: Consumer = ???
+      |  List(1).foreach(<<consumer.su@@bConsumer(consumer)>>.consume(1))
+      |}
+      |""".stripMargin,
+    """|**Expression type**:
+       |```scala
+       |Consumer
+       |```
+       |**Symbol signature**:
+       |```scala
+       |def subConsumer[T](i: T): T
+       |```
+       |""".stripMargin
+  )
+
+  check(
+    "function-chain5",
+    """
+      |trait Consumer {
+      |  def subConsumer[T](i: T): T
+      |  def consume(value: Int)(n: Int): Unit
+      |}
+      |
+      |object O {
+      |  def w = {
+      |    val consumer: Consumer = ???
+      |    List(1).foreach(consumer.subConsumer(<<consu@@mer>>).consume(1))
+      |  }
+      |}
+      |""".stripMargin,
+    """|```scala
+       |val consumer: Consumer
+       |```
+       |""".stripMargin
+  )
+
 }