From 4db804bc7b75038a8b4a36d4132af21e30c15ebc Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Tue, 8 Mar 2016 18:05:41 +0100
Subject: More detailed diagnostic in NavigateAST

---
 src/dotty/tools/dotc/ast/NavigateAST.scala | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/dotty/tools/dotc/ast/NavigateAST.scala b/src/dotty/tools/dotc/ast/NavigateAST.scala
index 9c1c17f50..3753c6702 100644
--- a/src/dotty/tools/dotc/ast/NavigateAST.scala
+++ b/src/dotty/tools/dotc/ast/NavigateAST.scala
@@ -17,7 +17,12 @@ object NavigateAST {
       case (utree: untpd.Tree) :: _ =>
         utree
       case _ =>
-        throw new Error(i"no untyped tree for $tree, best matching path =\n${untypedPath(tree, exactMatch = false)}%\n====\n%")
+        val loosePath = untypedPath(tree, exactMatch = false)
+        throw new
+          Error(i"""no untyped tree for $tree, pos = ${tree.pos}, envelope = ${tree.envelope}
+                   |best matching path =\n$loosePath%\n====\n%
+                   |path positions = ${loosePath.map(_.pos)}
+                   |path envelopes = ${loosePath.map(_.envelope)}""".stripMargin)
     }
 
   /** The reverse path of untyped trees starting with a tree that closest matches
-- 
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