SI-7319 Clear error buffer during Typer reset.

Contexts share error/warning buffers with their
children, and this also applies ot the shared
`startContext`.

That context flushes the buffers in `startContext`
in `resetContexts`.

It also removes `typerReportAnyContextErrors`, which
appears to be an elaborate no-op. It is only ever passed
a context `c` which is a direct child of `this.context`.
So taking a buffered error out of `c` and reissuing it
into `this.context` merely re-inserts into into the same
error buffer. Consrast this with `silent`, which uses
a child context with a fresh error buffer.

SI-7319 Flush error buffer in typerReportAnyContextErrors.

After this change, we no longer rely on the backstop in resetContexts
introduced in the previous commit.

1 files changed, 13 insertions, 0 deletions

diff --git a/test/files/run/t7319.scala b/test/files/run/t7319.scala
new file mode 100644
index 0000000000..23ffeb977d
--- /dev/null
+++ b/test/files/run/t7319.scala
@@ -0,0 +1,13 @@
+import scala.tools.partest.ReplTest
+
+object Test extends ReplTest {
+  // so we can provide the ambiguities, rather than relying in Predef implicits
+  override def extraSettings = "-Yno-predef"
+  override def code = """
+class M[A]
+implicit def ma0[A](a: A): M[A] = null
+implicit def ma1[A](a: A): M[A] = null
+def convert[F[X <: F[X]]](builder: F[_ <: F[_]]) = 0
+convert(Some[Int](0))
+0""" // before the fix, this line, and all that followed, re-issued the implicit ambiguity error.
+}