implement inverse transformation to mkFor

This effectively reconstructs a sequence of enumerators and body
from the tree produced by mkFor. This lets to define bi-directional
SyntacticFor and SyntacticForYield constructors/extractors to work
with for loops.

Correctness of the transformation is tested by a scalacheck test
that generates a sequence of random enumerators, sugars them into
maps/flatMaps/foreach/withFilter calls and reconstructs them back.

2 files changed, 39 insertions, 0 deletions

diff --git a/test/files/scalacheck/quasiquotes/ForProps.scala b/test/files/scalacheck/quasiquotes/ForProps.scala
new file mode 100644
index 0000000000..234f4d10eb
--- /dev/null
+++ b/test/files/scalacheck/quasiquotes/ForProps.scala
@@ -0,0 +1,38 @@
+import org.scalacheck._, Prop._, Gen._, Arbitrary._
+import scala.reflect.runtime.universe._, Flag._, build.{Ident => _, _}
+
+object ForProps extends QuasiquoteProperties("for") {
+  case class ForEnums(val value: List[Tree])
+
+  def genSimpleBind: Gen[Bind] =
+    for(name <- genTermName)
+      yield pq"$name @ _"
+
+  def genForFilter: Gen[Tree] =
+    for(cond <- genIdent(genTermName))
+      yield SyntacticFilter(cond)
+
+  def genForFrom: Gen[Tree] =
+    for(lhs <- genSimpleBind; rhs <- genIdent(genTermName))
+      yield SyntacticValFrom(lhs, rhs)
+
+  def genForEq: Gen[Tree] =
+    for(lhs <- genSimpleBind; rhs <- genIdent(genTermName))
+      yield SyntacticValEq(lhs, rhs)
+
+  def genForEnums(size: Int): Gen[ForEnums] =
+    for(first <- genForFrom; rest <- listOfN(size, oneOf(genForFrom, genForFilter, genForEq)))
+      yield new ForEnums(first :: rest)
+
+  implicit val arbForEnums: Arbitrary[ForEnums] = arbitrarySized(genForEnums)
+
+  property("construct-reconstruct for") = forAll { (enums: ForEnums, body: Tree) =>
+    val SyntacticFor(recoveredEnums, recoveredBody) = SyntacticFor(enums.value, body)
+    recoveredEnums ≈ enums.value && recoveredBody ≈ body
+  }
+
+  property("construct-reconstruct for-yield") = forAll { (enums: ForEnums, body: Tree) =>
+    val SyntacticForYield(recoveredEnums, recoveredBody) = SyntacticForYield(enums.value, body)
+    recoveredEnums ≈ enums.value && recoveredBody ≈ body
+  }
+}
\ No newline at end of file
diff --git a/test/files/scalacheck/quasiquotes/Test.scala b/test/files/scalacheck/quasiquotes/Test.scala
index 73cac0368c..8b1e779ab2 100644
--- a/test/files/scalacheck/quasiquotes/Test.scala
+++ b/test/files/scalacheck/quasiquotes/Test.scala
@@ -12,5 +12,6 @@ object Test extends Properties("quasiquotes") {
   include(DefinitionConstructionProps)
   include(DefinitionDeconstructionProps)
   include(DeprecationProps)
+  include(ForProps)
   include(TypecheckedProps)
 }