Merge pull request #8288 from soronpo/pickling

Fixes #8287 by simplifying the pickled folded constant presentation via homogenize

Author: smarter

compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -61,8 +61,9 @@ class PlainPrinter(_ctx: Context) extends Printer {
           homogenize(tp.info)
         case tp: LazyRef =>
           homogenize(tp.ref)
-        case AppliedType(tycon, args) =>
-          tycon.dealias.appliedTo(args)
+        case tp @ AppliedType(tycon, args) =>
+          if (defn.isCompiletimeAppliedType(tycon.typeSymbol)) tp.tryCompiletimeConstantFold
+          else tycon.dealias.appliedTo(args)
         case _ =>
           tp
       }

tests/pos/singleton-ops-test-issue-8287.scala

@@ -0,0 +1,14 @@
+import scala.compiletime.ops.int._
+import scala.annotation.infix
+
+object Test {
+  class Vec[S <: Int] {
+    @infix def concat [RS <: Int](that : Vec[RS]) : Vec[S + RS] = new Vec[S + RS]
+  }
+
+  val v1 = new Vec[1]
+  val v2 = new Vec[2]
+  val v3 : Vec[3] = v1 concat v2
+  val v3a = v1 concat v2
+  val v3b : Vec[3] = v3a
+}