SI-7167 implicit macros decide what is divergence

This is a port of https://github.com/scala/scala/commit/8168f118c9 from 2.10.x,
with an additional change to the `enclosingImplicits` and `openImplicits` APIs,
which encapsulates tuples of `pt` and `tree` into `ImplicitCandidate`.

2 files changed, 26 insertions, 0 deletions

diff --git a/test/files/run/macro-divergence-spurious/Impls_Macros_1.scala b/test/files/run/macro-divergence-spurious/Impls_Macros_1.scala
new file mode 100644
index 0000000000..bc4a9fded7
--- /dev/null
+++ b/test/files/run/macro-divergence-spurious/Impls_Macros_1.scala
@@ -0,0 +1,23 @@
+import scala.reflect.macros.Context
+import language.experimental.macros
+
+trait Complex[T]
+
+class Foo(val bar: Bar)
+class Bar(val s: String)
+
+object Complex {
+  def impl[T: c.WeakTypeTag](c: Context): c.Expr[Complex[T]] = {
+    import c.universe._
+    val tpe = weakTypeOf[T]
+    for (f <- tpe.declarations.collect{case f: TermSymbol if f.isParamAccessor && !f.isMethod => f}) {
+      val trecur = appliedType(typeOf[Complex[_]], List(f.typeSignature))
+      val recur = c.inferImplicitValue(trecur, silent = true)
+      if (recur == EmptyTree) c.abort(c.enclosingPosition, s"couldn't synthesize $trecur")
+    }
+    c.literalNull
+  }
+
+  implicit object ComplexString extends Complex[String]
+  implicit def genComplex[T]: Complex[T] = macro impl[T]
+}
diff --git a/test/files/run/macro-divergence-spurious/Test_2.scala b/test/files/run/macro-divergence-spurious/Test_2.scala
new file mode 100644
index 0000000000..dcc4593335
--- /dev/null
+++ b/test/files/run/macro-divergence-spurious/Test_2.scala
@@ -0,0 +1,3 @@
+object Test extends App {
+  println(implicitly[Complex[Foo]])
+}
\ No newline at end of file