SI-8675 Avoid unreported error after second try using implicit view

This is specific to situations in which we first typecheck an
application `qual.m(arg)` against the method `m` directly provided
by `qual`, and then fall back to `implicitView(qual).m(arg)`.

Regressed in SI-3971 / 7fa77af, in which error reports were moved
to the innermost `Apply`, and the check for `errorInResult` was
accordingly changed to recurse through `Apply` trees.

Before that change, we did not fall back to using a view. After the
change, we do try a view. We retypecheck the arguments under the
`retyping` mode (see `tryTypedArgs`), but this doesn't seem to
be enough to avoid leaking the error typed nested trees from the
first try.

Here's an example from the enclosed test case:

    a.update(0, x[A]({new isString(true)}))
                                   `-- error typed

    refArrayOps(a).update(0, x[A]({new isString(true)}))
                             `                  `-- error type persists
                              `-- this tree is retypecked by tryTypedArgs

This commit changes `onError` to only proceed with the second
try if the retyped argument trees are error free.

1 files changed, 24 insertions, 0 deletions

diff --git a/test/files/neg/t8675.scala b/test/files/neg/t8675.scala
new file mode 100644
index 0000000000..ca9bb57ffa
--- /dev/null
+++ b/test/files/neg/t8675.scala
@@ -0,0 +1,24 @@
+class A(s: String) {
+  def foo(x: A) = x
+}
+
+class isString(s: String)
+
+class Test {
+
+  def x[A](a: Any): A = ???
+
+  def test {
+    val a = Array[A]()
+    a.update(0, x[A]({new isString(true)})) // !!! allowed
+
+    // boils down to
+    class X {
+      def m(p: Any) {}
+    }
+    implicit class XOps(x: X) {
+      def m(p: Any) {}
+    }
+    new X().m(x[A]({new isString(true)})) // !!! allowed
+  }
+}