upgrade to Scala 2.13.4

Author: SethTisue

.travis.yml

@@ -8,7 +8,7 @@ scala:
   - 3.0.0-M2
   - 2.11.12
   - 2.12.12
-  - 2.13.3
+  - 2.13.4
 
 env:
   - ADOPTOPENJDK=8     SCALAJS_VERSION=

build.sbt

@@ -13,6 +13,9 @@ lazy val parserCombinators = crossProject(JVMPlatform, JSPlatform, NativePlatfor
 
     libraryDependencies += "junit" % "junit" % "4.13.1" % Test,
     libraryDependencies += "com.novocode" % "junit-interface" % "0.11" % Test,
+    // so we can `@nowarn` in test code, but only in test code, so the dependency
+    // doesn't leak downstream
+    libraryDependencies += "org.scala-lang.modules" %% "scala-collection-compat" % "2.3.1" % Test,
 
     apiMappings ++= scalaInstance.value.libraryJars.collect {
       case file if file.getName.startsWith("scala-library") && file.getName.endsWith(".jar") =>

shared/src/main/scala/scala/util/parsing/combinator/Parsers.scala

@@ -403,7 +403,9 @@ trait Parsers {
         val res1 = Parser.this(in)
         val res2 = q(in)
 
-        (res1, res2) match {
+        // compiler thinks match isn't exhaustive; perhaps it's right, but does that mean there's a bug here?
+        // that's not clear to me, so for now let's just `@unchecked` it
+        ((res1, res2): @unchecked) match {
           case (s1 @ Success(_, next1), s2 @ Success(_, next2)) => if (next2.pos < next1.pos || next2.pos == next1.pos) s1 else s2
           case (s1 @ Success(_, _), _) => s1
           case (_, s2 @ Success(_, _)) => s2

shared/src/test/scala/scala/util/parsing/combinator/PackratParsersTest.scala

@@ -190,7 +190,8 @@ private object grammars3 extends StandardTokenParsers with PackratParsers {
    | success(Nil)
   )
 
+  @annotation.nowarn  // Some(xs) in pattern isn't exhaustive
   def repMany1[T](p: => Parser[T], q: => Parser[T]): Parser[List[T]] =
-   p~opt(repMany(p,q))~q ^^ {case x~Some(xs)~y => x::xs:::(y::Nil)}
+    p~opt(repMany(p,q))~q ^^ {case x~Some(xs)~y => x::xs:::(y::Nil)}
 
 }