Merge pull request #3858 from densh/si/8703

SI-8703 add support for blocks with just a single expression to quasiquotes

3 files changed, 19 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/reflect/quasiquotes/Parsers.scala b/src/compiler/scala/tools/reflect/quasiquotes/Parsers.scala
index b68022afd9..392b7fc881 100644
--- a/src/compiler/scala/tools/reflect/quasiquotes/Parsers.scala
+++ b/src/compiler/scala/tools/reflect/quasiquotes/Parsers.scala
@@ -69,9 +69,16 @@ trait Parsers { self: Quasiquotes =>
         override def makeTupleType(trees: List[Tree]): Tree = TupleTypePlaceholder(trees)
 
         // q"{ $x }"
-        override def makeBlock(stats: List[Tree]): Tree = stats match {
-          case (head @ Ident(name)) :: Nil if isHole(name) => Block(Nil, head)
-          case _ => super.makeBlock(stats)
+        override def makeBlock(stats: List[Tree]): Tree = method match {
+          case nme.apply   =>
+            stats match {
+              // we don't want to eagerly flatten trees with placeholders as they
+              // might have to be wrapped into a block depending on their value
+              case (head @ Ident(name)) :: Nil if isHole(name) => Block(Nil, head)
+              case _ => gen.mkBlock(stats, doFlatten = true)
+            }
+          case nme.unapply => gen.mkBlock(stats, doFlatten = false)
+          case other       => global.abort("unreachable")
         }
 
         // tq"$a => $b"
diff --git a/src/reflect/scala/reflect/internal/TreeGen.scala b/src/reflect/scala/reflect/internal/TreeGen.scala
index 9066c73393..6e8e992d16 100644
--- a/src/reflect/scala/reflect/internal/TreeGen.scala
+++ b/src/reflect/scala/reflect/internal/TreeGen.scala
@@ -451,10 +451,10 @@ abstract class TreeGen {
   def mkSyntheticUnit() = Literal(Constant(())).updateAttachment(SyntheticUnitAttachment)
 
   /** Create block of statements `stats`  */
-  def mkBlock(stats: List[Tree]): Tree =
+  def mkBlock(stats: List[Tree], doFlatten: Boolean = true): Tree =
     if (stats.isEmpty) mkSyntheticUnit()
     else if (!stats.last.isTerm) Block(stats, mkSyntheticUnit())
-    else if (stats.length == 1) stats.head
+    else if (stats.length == 1 && doFlatten) stats.head
     else Block(stats.init, stats.last)
 
   /** Create a block that wraps multiple statements but don't
diff --git a/test/files/scalacheck/quasiquotes/TermDeconstructionProps.scala b/test/files/scalacheck/quasiquotes/TermDeconstructionProps.scala
index 49ffaff630..07e8f3faac 100644
--- a/test/files/scalacheck/quasiquotes/TermDeconstructionProps.scala
+++ b/test/files/scalacheck/quasiquotes/TermDeconstructionProps.scala
@@ -246,4 +246,11 @@ object TermDeconstructionProps extends QuasiquoteProperties("term deconstruction
     assert(f ≈ `new`)
     assert(argss.isEmpty)
   }
+
+  property("SI-8703 extract block with single expression") = test {
+    val q"{ $a }" = Block(Nil, q"1")
+    val Literal(Constant(1)) = a
+    val q"{ $b }" = q"2"
+    val Literal(Constant(2)) = b
+  }
 }