From 072af0012ac10b5d24d91954911825be543a6517 Mon Sep 17 00:00:00 2001
From: liu fengyun <liu@fengy.me>
Date: Wed, 7 Dec 2016 23:09:06 +0100
Subject: [PATCH] fix #1773: handle patterns in interpolated string

---
 compiler/src/dotty/tools/dotc/ast/Desugar.scala |  6 ++++++
 tests/run/i1773.check                           |  2 ++
 tests/run/i1773.scala                           | 14 ++++++++++++++
 3 files changed, 22 insertions(+)
 create mode 100644 tests/run/i1773.check
 create mode 100644 tests/run/i1773.scala

diff --git a/compiler/src/dotty/tools/dotc/ast/Desugar.scala b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
index c8b1ed909967..7f25d6b0c5f6 100644
--- a/compiler/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
@@ -916,7 +916,11 @@ object desugar {
         val elems = segments flatMap {
           case ts: Thicket => ts.trees.tail
           case t => Nil
+        } map {
+          case Block(Nil, expr) => expr // important for interpolated string as patterns, see i1773.scala
+          case t => t
         }
+
         Apply(Select(Apply(Ident(nme.StringContext), strs), id), elems)
       case InfixOp(l, op, r) =>
         if (ctx.mode is Mode.Type)
@@ -1081,6 +1085,8 @@ object desugar {
         trees foreach collect
       case Thicket(trees) =>
         trees foreach collect
+      case Block(Nil, expr) =>
+        collect(expr)
       case _ =>
     }
     collect(tree)
diff --git a/tests/run/i1773.check b/tests/run/i1773.check
new file mode 100644
index 000000000000..888299747af9
--- /dev/null
+++ b/tests/run/i1773.check
@@ -0,0 +1,2 @@
+class 
+ extends 
diff --git a/tests/run/i1773.scala b/tests/run/i1773.scala
new file mode 100644
index 000000000000..82fa0dfb4e74
--- /dev/null
+++ b/tests/run/i1773.scala
@@ -0,0 +1,14 @@
+object Test {
+  implicit class Foo(sc: StringContext) {
+    object q {
+      def unapply(arg: Any): Option[(Any, Any)] =
+        Some((sc.parts(0), sc.parts(1)))
+    }
+  }
+
+  def main(args: Array[String]): Unit = {
+    val q"class ${name: String} extends ${parent: String}" = new Object
+    println(name)
+    println(parent)
+  }
+}