Do not synthesize type tag for param prefixes

Author: nicolasstucki

compiler/src/dotty/tools/dotc/transform/ReifyQuotes.scala

@@ -297,7 +297,7 @@ class ReifyQuotes extends MacroTransformWithImplicits with InfoTransformer {
       else if (sym.exists && !sym.isStaticOwner && !levelOK(sym))
         for (errMsg <- tryHeal(tp, pos))
           ctx.error(em"""access to $symStr from wrong staging level:
-                        | - the definition is at level ${levelOf(sym)},
+                        | - the definition is at level ${levelOf.getOrElse(sym, 0)},
                         | - but the access is at level $level.$errMsg""", pos)
     }
 

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -571,7 +571,7 @@ trait Implicits { self: Typer =>
     }
 
     def synthesizedTypeTag(formal: Type): Tree = formal.argInfos match {
-      case arg :: Nil =>
+      case arg :: Nil if !arg.typeSymbol.is(Param) =>
         object bindFreeVars extends TypeMap {
           var ok = true
           def apply(t: Type) = t match {