Fix namedTrees with substring search

This functin used to produce a string representation of the whole tree
and then look whether this contains the substring we're looking for.

When we're not including references in the search, we can limit the
search to the trees names rather than their whole representation.

Author: Duhemm

compiler/src/dotty/tools/dotc/interactive/Interactive.scala

@@ -269,8 +269,12 @@ object Interactive {
    *  @param includeReferences  If true, include references and not just definitions
    */
   def namedTrees(trees: List[SourceTree], includeReferences: Boolean, nameSubstring: String)
-   (implicit ctx: Context): List[SourceTree] =
-    namedTrees(trees, includeReferences, _.show.toString.contains(nameSubstring))
+   (implicit ctx: Context): List[SourceTree] = {
+    val predicate: NameTree => Boolean =
+      if (includeReferences) _.show.contains(nameSubstring)
+      else _.name.toString.contains(nameSubstring)
+    namedTrees(trees, includeReferences, predicate)
+  }
 
   /** Find named trees with a non-empty position satisfying `treePredicate` in `trees`.
    *