Avoid fishy reference equality on strings

While the code looks correct (because strippedName comes from stripSuffix and because of stripSuffix's contract and implementation), this is subtle enough that we should either add a test or use !=.

Since `String.equals` happens to be O(1) in this case, changing the code looks simpler. `String.equals` is O(1) here because it will either succeed by testing pointer equality or fail by noticing a length mismatch, so it will never look at the actual contents!

Author: Blaisorblade

compiler/src/dotty/tools/dotc/core/Decorators.scala

@@ -157,7 +157,7 @@ object Decorators {
         names exists { name =>
           name == "all" || {
             val strippedName = name.stripSuffix("+")
-            val logNextPhase = name ne strippedName
+            val logNextPhase = name != strippedName
             phase.phaseName.startsWith(strippedName) ||
               (logNextPhase && phase.prev.phaseName.startsWith(strippedName))
           }