Added jpath check to ClassLikeSupport getParentsAsTreeSymbolTuples

Fixes scala#15927

Check for whether the java parent exists before checking the start
and end of the span to confirm whether the span exists in
getParentsAsTreeSymbolTuples.

Author: yzia2000

scaladoc-testcases/src/tests/noJavaParent.scala

@@ -0,0 +1,6 @@
+package tests
+package noJavaParent
+
+// https://github.com/lampepfl/dotty/issues/15927
+
+trait Foo3 extends Numeric[Any]

scaladoc/src/dotty/tools/scaladoc/tasty/ClassLikeSupport.scala

@@ -266,7 +266,8 @@ trait ClassLikeSupport:
     def getParentsAsTreeSymbolTuples: List[(Tree, Symbol)] =
       if noPosClassDefs.contains(c.symbol) then Nil
       else for
-        parentTree <- c.parents if parentTree.pos.start != parentTree.pos.end // We assume here that order is correct
+        // TODO: add exists function to position methods in Quotes and replace the condition here for checking the JPath
+        parentTree <- c.parents if parentTree.pos.sourceFile.getJPath.isDefined && parentTree.pos.start != parentTree.pos.end // We assume here that order is correct
         parentSymbol = parentTree match
           case t: TypeTree => t.tpe.typeSymbol
           case tree if tree.symbol.isClassConstructor => tree.symbol.owner

scaladoc/test/dotty/tools/scaladoc/signatures/TranslatableSignaturesTestCases.scala

@@ -106,3 +106,5 @@ class ImplicitMembers extends SignatureTest(
   Seq("def"),
   filterFunc = _.toString.endsWith("OuterClass$ImplicitMemberTarget.html")
 )
+
+class NoJavaParent extends SignatureTest("noJavaParent", SignatureTest.all)