fix: prefer non-export definition locations (#20252)

fixes: scalameta/metals#5892

Author: tgodzik

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

@@ -13,7 +13,7 @@ import dotty.tools.dotc.ast.NavigateAST
 import dotty.tools.dotc.ast.tpd.*
 import dotty.tools.dotc.ast.untpd
 import dotty.tools.dotc.core.Contexts.Context
-import dotty.tools.dotc.core.Flags.ModuleClass
+import dotty.tools.dotc.core.Flags.{Exported, ModuleClass}
 import dotty.tools.dotc.core.Symbols.*
 import dotty.tools.dotc.interactive.Interactive
 import dotty.tools.dotc.interactive.InteractiveDriver
@@ -123,9 +123,12 @@ class PcDefinitionProvider(
       case symbols @ (sym :: other) =>
         val isLocal = sym.source == pos.source
         if isLocal then
-          val defs =
-            Interactive.findDefinitions(List(sym), driver, false, false).filter(_.source == sym.source)
-          defs.headOption match
+          val (exportedDefs, otherDefs) =
+            Interactive.findDefinitions(List(sym), driver, false, false)
+              .filter(_.source == sym.source)
+              .partition(_.tree.symbol.is(Exported))
+
+          otherDefs.headOption.orElse(exportedDefs.headOption)  match
             case Some(srcTree) =>
               val pos = srcTree.namePos
               pos.toLocation match

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

@@ -274,6 +274,23 @@ class PcDefinitionSuite extends BasePcDefinitionSuite:
         |""".stripMargin
     )
 
+  @Test def exportTermExtension =
+    check(
+      """|package a
+         |class Test extends A {
+         |  assert("Hello".fo@@o == "HelloFoo")
+         |}
+         |
+         |trait A {
+         |  export B.*
+         |}
+         |
+         |object B {
+         |  extension (value: String) def <<foo>>: String = s"${value}Foo"
+         |}
+         |""".stripMargin
+    )
+
   @Test def `named-arg-local` =
     check(
       """|