Move MappedAlternative check into reorder

Author: som-snytt

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

@@ -350,7 +350,6 @@ object SymDenotations {
 
       ensureCompleted()
       if rawParamss.isEmpty then recurWithoutParamss(info)
-      else if symbol.hasAnnotation(defn.MappedAlternativeAnnot) then recurWithParamss(info.stripPoly, rawParamss)
       else recurWithParamss(info, rawParamss)
     end paramSymss
 

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

@@ -645,7 +645,11 @@ trait Applications extends Compatibility {
           version.map(v => s" (since $v)").getOrElse("")
 
       val deprecatedNames: Map[Name, Annotation] =
-        methRef.symbol.paramSymss.find(_.exists(_.isTerm)) match
+        val sym = methRef.symbol
+        val paramss =
+          if sym.hasAnnotation(defn.MappedAlternativeAnnot) then sym.rawParamss
+          else sym.paramSymss
+        paramss.find(_.exists(_.isTerm)) match
         case Some(ps) if ps.exists(_.hasAnnotation(defn.DeprecatedNameAnnot)) =>
           ps.flatMap: p =>
             p.getAnnotation(defn.DeprecatedNameAnnot).map(p.name -> _)