Work around 2.13 collection performance bug

Author: smarter

compiler/src/dotty/tools/dotc/ast/Trees.scala

@@ -361,13 +361,16 @@ object Trees {
           val nameStart =
             if (point != span.start) point
             else {
+              // Use an immutable ArraySeq to work around https://github.com/scala/bug/issues/11708
+              val content = collection.immutable.ArraySeq.unsafeWrapArray(source.content())
+
               // Point might be too far away from start to be recorded. In this case we fall back to scanning
               // forwards from the start offset for the name.
               // Note: This might be inaccurate since scanning might hit accidentally the same
               // name (e.g. in a comment) before finding the real definition.
               // To make this behavior more robust we'd have to change the trees for definitions to contain
               // a fully positioned Ident in place of a name.
-              val idx = source.content().indexOfSlice(realName, point)
+              val idx = content.indexOfSlice(realName, point)
               if (idx >= 0) idx
               else point // use `point` anyway. This is important if no source exists so scanning fails
             }