From 59cdd50fa8d2466b9778dca4b354afc03f17be67 Mon Sep 17 00:00:00 2001
From: Eugene Burmako <xeno.by@gmail.com>
Date: Mon, 9 Dec 2013 18:25:43 +0100
Subject: awakens default getter synthesis from the untyper nightmare
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Our happy little macro paradise is regularly invaded by resetAllAttrs,
the bane of all macros and typers. It’s so ruthless and devastating that
we’ve been long scheming to hack something really cool and to one day
defeat it.

Today we make the first step towards the happy future. Today we overthrow
the UnTyper, resetAllAttrs’s elder brother that rules in the kingdoms of
GetterLand and CaseClassia, and banish him from the land of getters.
In the name of what’s good and meta, let’s band together and completely
drive him away in a subsequent pull request!

To put it in a nutshell, instead of using untyper on a DefDef to do
default getter synthesis, the commit duplicates the DefDef and does
resetLocalAttrs on it.

As default getter synthesis proceeds with figuring out type and value
parameters for the getter, then its tpt and finally its rhs, the commit
destructures the duplicated DefDef and then assembles the default getter
from the destructured parts instead of doing copyUntyped/copyUntypedInvariant
on the original DefDef.

I would say the test coverage is pretty good, as I had to figure out
3 or 4 test failures before I got to the stage when everything worked.
Iirc it tests pretty exotic stuff like polymorphic default parameters
in both second and third parameter lists, so it looks like we're pretty
good in this department.
---
 test/files/run/macro-default-params/Macros_1.scala | 27 ++++++++++++++++++++++
 test/files/run/macro-default-params/Test_2.scala   |  3 +++
 2 files changed, 30 insertions(+)
 create mode 100644 test/files/run/macro-default-params/Macros_1.scala
 create mode 100644 test/files/run/macro-default-params/Test_2.scala

(limited to 'test/files/run/macro-default-params')

diff --git a/test/files/run/macro-default-params/Macros_1.scala b/test/files/run/macro-default-params/Macros_1.scala
new file mode 100644
index 0000000000..47780ea4b8
--- /dev/null
+++ b/test/files/run/macro-default-params/Macros_1.scala
@@ -0,0 +1,27 @@
+import scala.language.experimental.macros
+import scala.reflect.macros.WhiteboxContext
+
+object Macros {
+  def id[A]: A = null.asInstanceOf[A]
+
+  def foo: Any = macro impl
+  def impl(c: WhiteboxContext): c.Tree = {
+    import c.universe._
+    import Flag._
+
+    lazy val tpe = TypeTree(typeOf[Int])
+
+    /* If we used this line instead, it would work! */
+    // lazy val tpe = tq"Int"
+
+    lazy val param: ValDef = {
+      val p1 = q"val a: ${tpe.duplicate} = Macros.id[${tpe.duplicate}]"
+      ValDef(Modifiers(DEFAULTPARAM), p1.name, p1.tpt, p1.rhs)
+    }
+
+    q"""
+      class C { def f($param) = a }
+      println(new C().f())
+    """
+  }
+}
diff --git a/test/files/run/macro-default-params/Test_2.scala b/test/files/run/macro-default-params/Test_2.scala
new file mode 100644
index 0000000000..5d19639cdd
--- /dev/null
+++ b/test/files/run/macro-default-params/Test_2.scala
@@ -0,0 +1,3 @@
+object Test extends App {
+  Macros.foo
+}
-- 
cgit v1.2.3