SI-6631 Handle invalid escapes in string interpolators

Patch contributed by Rex Kerr.

Author: retronym

src/library/scala/StringContext.scala

@@ -191,22 +191,23 @@ object StringContext {
     var cur = 0
     var idx = 0
     def output(ch: Char) = {
-      bldr append str.substring (start, cur)
+      bldr.append(str, start, cur)
       bldr append ch
       start = idx
     }
     while (idx < len) {
       cur = idx
       if (str(idx) == '\\') {
         idx += 1
+        if (idx >= len) throw new InvalidEscapeException(str, cur)
         if ('0' <= str(idx) && str(idx) <= '7') {
           val leadch = str(idx)
           var oct = leadch - '0'
           idx += 1
-          if ('0' <= str(idx) && str(idx) <= '7') {
+          if (idx < len && '0' <= str(idx) && str(idx) <= '7') {
             oct = oct * 8 + str(idx) - '0'
             idx += 1
-            if (leadch <= '3' && '0' <= str(idx) && str(idx) <= '7') {
+            if (idx < len && leadch <= '3' && '0' <= str(idx) && str(idx) <= '7') {
               oct = oct * 8 + str(idx) - '0'
               idx += 1
             }
@@ -234,6 +235,6 @@ object StringContext {
       }
     }
     if (start == 0) str
-    else (bldr append str.substring(start, idx)).toString
+    else bldr.append(str, start, idx).toString
   }
 }

test/files/run/t6631.scala

@@ -0,0 +1,18 @@
+import reflect.ClassTag
+
+object Test extends App {
+  def intercept[T <: Throwable : ClassTag](act: => Any) = try {
+    act
+  } catch {
+    case x: Throwable =>
+      val cls = implicitly[ClassTag[T]].runtimeClass
+      assert(cls.isInstance(x), (x.getClass, x, cls).toString)
+  }
+  assert(s"""\f\r\n\t""" == "\f\r\n\t")
+
+  import StringContext.InvalidEscapeException
+  intercept[InvalidEscapeException](s"""\""")
+  intercept[InvalidEscapeException](s"""\x""")
+  intercept[InvalidEscapeException](s"\")
+
+}