Use context for buffering errors that cannot/shouldn't be reported in the given moment (instead of throwing type errors). This avoids previous problems where we were creating fake error trees in some incorrect places like in type completers in Namers etc. Implicits relied heavily on type errors being thrown but performance should stay the same due to some explicit checks/returns.

Some of the problems involved how ambiguous error messages were collected/reported because it was very random (similarly for divergent implicits). This should be more explicit now. Reduced the number of unnecessary cyclic references being thrown (apart from those in Symbols/Types which don't have a context and need to stay for now as is).

Review by @paulp, @odersky.

1 files changed, 4 insertions, 1 deletions

diff --git a/test/files/neg/t1878.check b/test/files/neg/t1878.check
index f3a6701d41..128741a022 100644
--- a/test/files/neg/t1878.check
+++ b/test/files/neg/t1878.check
@@ -6,10 +6,13 @@ t1878.scala:3: error: scrutinee is incompatible with pattern type;
  required: String
   val err1 = "" match { case Seq(f @ _*, ',') => f }
                                 ^
+t1878.scala:3: error: not found: value f
+  val err1 = "" match { case Seq(f @ _*, ',') => f }
+                                                 ^
 t1878.scala:9: error: _* may only come last
   val List(List(_*, arg2), _) = List(List(1,2,3), List(4,5,6))
                  ^
 t1878.scala:13: error: _* may only come last
     case <p> { _* } </p> =>
                 ^
-four errors found
+5 errors found