Fix goto-def on exported forwarders (#19494)

Author: dwijnand

Diff for: compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -1142,6 +1142,11 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       buf.toList
     }
 
+    def collectSubTrees[A](f: PartialFunction[Tree, A])(using Context): List[A] =
+      val buf = mutable.ListBuffer[A]()
+      foreachSubTree(f.runWith(buf += _)(_))
+      buf.toList
+
     /** Set this tree as the `defTree` of its symbol and return this tree */
     def setDefTree(using Context): ThisTree = {
       val sym = tree.symbol

Diff for: compiler/src/dotty/tools/dotc/core/Flags.scala

@@ -363,7 +363,7 @@ object Flags {
   val (Enum @ _, EnumVal @ _, _) = newFlags(40, "enum")
 
   /** An export forwarder */
-  val (Exported @ _, _, _) = newFlags(41, "exported")
+  val (Exported @ _, ExportedTerm @ _, ExportedType @ _) = newFlags(41, "exported")
 
   /** Labeled with `erased` modifier (erased value or class)  */
   val (Erased @ _, _, _) = newFlags(42, "erased")

Diff for: compiler/src/dotty/tools/dotc/core/Symbols.scala

@@ -19,9 +19,7 @@ import DenotTransformers.*
 import StdNames.*
 import NameOps.*
 import NameKinds.LazyImplicitName
-import ast.tpd
-import tpd.{Tree, TreeProvider, TreeOps}
-import ast.TreeTypeMap
+import ast.*, tpd.*
 import Constants.Constant
 import Variances.Variance
 import reporting.Message
@@ -325,13 +323,26 @@ object Symbols extends SymUtils {
 
     /** A symbol related to `sym` that is defined in source code.
      *
-     *  @see enclosingSourceSymbols
+     *  @see [[interactive.Interactive.enclosingSourceSymbols]]
      */
     @annotation.tailrec final def sourceSymbol(using Context): Symbol =
       if (!denot.exists)
         this
       else if (denot.is(ModuleVal))
         this.moduleClass.sourceSymbol // The module val always has a zero-extent position
+      else if denot.is(ExportedType) then
+        denot.info.dropAlias.finalResultType.typeConstructor match
+          case tp: NamedType => tp.symbol.sourceSymbol
+          case _             => this
+      else if denot.is(ExportedTerm) then
+        val root = denot.maybeOwner match
+          case cls: ClassSymbol => cls.rootTreeContaining(name.toString)
+          case _                => EmptyTree
+        val targets = root.collectSubTrees:
+          case tree: DefDef if tree.symbol == denot.symbol => methPart(tree.rhs).tpe
+        targets.match
+          case (tp: NamedType) :: _ => tp.symbol.sourceSymbol
+          case _                    => this
       else if (denot.is(Synthetic)) {
         val linked = denot.linkedClass
         if (linked.exists && !linked.is(Synthetic))

Diff for: compiler/src/dotty/tools/dotc/interactive/SourceTree.scala

@@ -42,7 +42,12 @@ case class SourceTree(tree: tpd.Import | tpd.NameTree, source: SourceFile) {
               (treeSpan.end - nameLength, treeSpan.end)
           Span(start, end, start)
         }
-        source.atSpan(position)
+        // Don't widen the span, only narrow.
+        // E.g. The star in a wildcard export is 1 character,
+        // and that is the span of the type alias that results from it
+        // but the name may very well be larger, which we don't want.
+        val span1 = if treeSpan.contains(position) then position else treeSpan
+        source.atSpan(span1)
       }
     case _ =>
       NoSourcePosition

Diff for: presentation-compiler/src/main/dotty/tools/pc/MetalsInteractive.scala

@@ -1,19 +1,14 @@
-package dotty.tools.pc
+package dotty.tools
+package pc
 
 import scala.annotation.tailrec
 
-import dotty.tools.dotc.ast.tpd
-import dotty.tools.dotc.ast.tpd.*
-import dotty.tools.dotc.ast.untpd
-import dotty.tools.dotc.core.Contexts.*
-import dotty.tools.dotc.core.Flags.*
-import dotty.tools.dotc.core.Names.Name
-import dotty.tools.dotc.core.StdNames
-import dotty.tools.dotc.core.Symbols.*
-import dotty.tools.dotc.core.Types.Type
-import dotty.tools.dotc.interactive.SourceTree
-import dotty.tools.dotc.util.SourceFile
-import dotty.tools.dotc.util.SourcePosition
+import dotc.*
+import ast.*, tpd.*
+import core.*, Contexts.*, Decorators.*, Flags.*, Names.*, Symbols.*, Types.*
+import interactive.*
+import util.*
+import util.SourcePosition
 
 object MetalsInteractive:
 
@@ -205,7 +200,10 @@ object MetalsInteractive:
             Nil
 
       case path @ head :: tail =>
-        if head.symbol.is(Synthetic) then
+        if head.symbol.is(Exported) then
+          val sym = head.symbol.sourceSymbol
+          List((sym, sym.info))
+        else if head.symbol.is(Synthetic) then
           enclosingSymbolsWithExpressionType(
             tail,
             pos,

Diff for: presentation-compiler/src/main/dotty/tools/pc/PcDefinitionProvider.scala

@@ -124,7 +124,7 @@ class PcDefinitionProvider(
         val isLocal = sym.source == pos.source
         if isLocal then
           val defs =
-            Interactive.findDefinitions(List(sym), driver, false, false)
+            Interactive.findDefinitions(List(sym), driver, false, false).filter(_.source == sym.source)
           defs.headOption match
             case Some(srcTree) =>
               val pos = srcTree.namePos

Diff for: presentation-compiler/test/dotty/tools/pc/tests/definition/PcDefinitionSuite.scala

@@ -199,6 +199,81 @@ class PcDefinitionSuite extends BasePcDefinitionSuite:
          |""".stripMargin
     )
 
+  @Test def exportType0 =
+    check(
+      """object Foo:
+        |  trait <<Cat>>
+        |object Bar:
+        |  export Foo.*
+        |class Test:
+        |  import Bar.*
+        |  def test = new Ca@@t {}
+        |""".stripMargin
+    )
+
+  @Test def exportType1 =
+    check(
+      """object Foo:
+        |  trait <<Cat>>[A]
+        |object Bar:
+        |  export Foo.*
+        |class Test:
+        |  import Bar.*
+        |  def test = new Ca@@t[Int] {}
+        |""".stripMargin
+    )
+
+  @Test def exportTerm0Nullary =
+    check(
+      """trait Foo:
+        |  def <<meth>>: Int
+        |class Bar(val foo: Foo):
+        |  export foo.*
+        |  def test(bar: Bar) = bar.me@@th
+        |""".stripMargin
+    )
+
+  @Test def exportTerm0 =
+    check(
+      """trait Foo:
+        |  def <<meth>>(): Int
+        |class Bar(val foo: Foo):
+        |  export foo.*
+        |  def test(bar: Bar) = bar.me@@th()
+        |""".stripMargin
+    )
+
+  @Test def exportTerm1 =
+    check(
+      """trait Foo:
+        |  def <<meth>>(x: Int): Int
+        |class Bar(val foo: Foo):
+        |  export foo.*
+        |  def test(bar: Bar) = bar.me@@th(0)
+        |""".stripMargin
+    )
+
+  @Test def exportTerm1Poly =
+    check(
+      """trait Foo:
+        |  def <<meth>>[A](x: A): A
+        |class Bar(val foo: Foo):
+        |  export foo.*
+        |  def test(bar: Bar) = bar.me@@th(0)
+        |""".stripMargin
+    )
+
+  @Test def exportTerm1Overload =
+    check(
+      """trait Foo:
+        |  def <<meth>>(x: Int): Int
+        |  def meth(x: String): String
+        |class Bar(val foo: Foo):
+        |  export foo.*
+        |  def test(bar: Bar) = bar.me@@th(0)
+        |""".stripMargin
+    )
+
   @Test def `named-arg-local` =
     check(
       """|