Fix codegen for String Ordering ops

Author: Alexey Romanov

src/common/OrderingOps.scala

@@ -152,8 +152,19 @@ trait ScalaGenOrderingOps extends ScalaGenBase {
     case OrderingGT(a,b) => emitValDef(sym, src"$a > $b")
     case OrderingGTEQ(a,b) => emitValDef(sym, src"$a >= $b")
     case OrderingEquiv(a,b) => emitValDef(sym, src"$a equiv $b")
-    case OrderingMax(a,b) => emitValDef(sym, src"$a max $b")
-    case OrderingMin(a,b) => emitValDef(sym, src"$a min $b")
+    // "$a max $b" is wrong for Strings because it tries to use `StringLike.max(Ordering)`
+    case c@OrderingMax(a,b) =>
+      val rhs = if (c.mev == manifest[String])
+        src"scala.math.Ordering.String.max($a, $b)"
+      else
+        src"$a max $b"
+      emitValDef(sym, rhs)
+    case c@OrderingMin(a,b) =>
+      val rhs = if (c.mev == manifest[String])
+        src"scala.math.Ordering.String.min($a, $b)"
+      else
+        src"$a min $b"
+      emitValDef(sym, rhs)
     case c@OrderingCompare(a,b) => c.mev match {
       case m if m == Manifest.Int => emitValDef(sym, "java.lang.Integer.compare("+quote(a)+","+quote(b)+")")
       case m if m == Manifest.Long => emitValDef(sym, "java.lang.Long.compare("+quote(a)+","+quote(b)+")")