fix #1779: support $_ and $_id in interpolated string

4 files changed, 19 insertions, 1 deletions

diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
index 51dafc928..1f5ad397d 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -625,6 +625,10 @@ object Parsers {
             atPos(in.offset) {
               if (in.token == IDENTIFIER)
                 termIdent()
+              else if (in.token == USCORE) {
+                in.nextToken()
+                Ident(nme.WILDCARD)
+              }
               else if (in.token == THIS) {
                 in.nextToken()
                 This(EmptyTypeIdent)
diff --git a/compiler/src/dotty/tools/dotc/parsing/Scanners.scala b/compiler/src/dotty/tools/dotc/parsing/Scanners.scala
index 60003d098..101be167e 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Scanners.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Scanners.scala
@@ -758,7 +758,7 @@ object Scanners {
           finishStringPart()
           nextRawChar()
           next.token = LBRACE
-        } else if (Character.isUnicodeIdentifierStart(ch)) {
+        } else if (Character.isUnicodeIdentifierStart(ch) || ch == '_') {
           finishStringPart()
           do {
             putChar(ch)
diff --git a/tests/run/i1779.check b/tests/run/i1779.check
new file mode 100644
index 000000000..4ef6e900e
--- /dev/null
+++ b/tests/run/i1779.check
@@ -0,0 +1 @@
+ extends 
diff --git a/tests/run/i1779.scala b/tests/run/i1779.scala
new file mode 100644
index 000000000..e81bc97b6
--- /dev/null
+++ b/tests/run/i1779.scala
@@ -0,0 +1,13 @@
+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 $_ extends $_parent" = new Object
+    println(_parent)
+  }
+}