amarki@amarki-462836:~$ scala -Xlint:missing-interpolator
Welcome to Scala version 2.11.2 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_05).
Type in expressions to have them evaluated.
Type :help for more information.

scala> { val foo = 1 ; "hi $foo" }
<console>:8: warning: possible missing interpolator: detected interpolated identifier `$foo`
              { val foo = 1 ; "hi $foo" }
                              ^
res0: String = hi $foo

scala> { val foo, bar = 1 ; "hi $foo$bar" }
res1: String = hi $foo$bar