Fix an erroneous comparison of RefinedType with Type.

sjrd · sjrd · commit 21729f3c9d81 · 2019-06-18T16:27:56.000+02:00
Discovered by new warnings emitted by the 2.13.0 compiler, yeah!
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -3095,7 +3095,7 @@ private[optimizer] abstract class OptimizerCore(config: CommonPhaseConfig) {
             PreTransLit(StringLiteral(s1 + s2))
           case (_, PreTransLit(StringLiteral(""))) =>
             foldBinaryOp(op, rhs1, lhs1)
-          case (PreTransLit(StringLiteral("")), _) if rhs1.tpe == StringType =>
+          case (PreTransLit(StringLiteral("")), _) if rhs1.tpe.base == StringType =>
             rhs1
           case (_, PreTransBinaryOp(String_+, rl, rr)) =>
             foldBinaryOp(String_+, PreTransBinaryOp(String_+, lhs1, rl), rr)
