Change the printers to print erased function parameters

Author: natsukagami

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

@@ -297,9 +297,13 @@ class PlainPrinter(_ctx: Context) extends Printer {
     "(" ~ toTextRef(tp) ~ " : " ~ toTextGlobal(tp.underlying) ~ ")"
 
   protected def paramsText(lam: LambdaType): Text = {
-    def paramText(name: Name, tp: Type) =
-      toText(name) ~ lambdaHash(lam) ~ toTextRHS(tp, isParameter = true)
-    Text(lam.paramNames.lazyZip(lam.paramInfos).map(paramText), ", ")
+    val companion = lam.companion
+    val isErased = if companion.isInstanceOf[ErasedMethodCompanion] then
+        companion.asInstanceOf[ErasedMethodCompanion].isErased
+      else List.fill(lam.paramNames.length)(false)
+    def paramText(name: Name, tp: Type, erased: Boolean) =
+      keywordText("erased ").provided(erased) ~ toText(name) ~ lambdaHash(lam) ~ toTextRHS(tp, isParameter = true)
+    Text(lam.paramNames.lazyZip(lam.paramInfos).lazyZip(isErased).map(paramText), ", ")
   }
 
   protected def ParamRefNameString(name: Name): String = nameString(name)

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

@@ -166,7 +166,6 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
       case info: MethodType =>
         changePrec(GlobalPrec) {
           "("
-          ~ keywordText("erased ").provided(info.isErasedMethod)
           ~ paramsText(info)
           ~ ") "
           ~ arrow(info.isImplicitMethod, isPure)
@@ -868,7 +867,6 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
       "()"
     case untpd.ValDefs(vparams @ (vparam :: _)) =>
       "(" ~ keywordText("using ").provided(vparam.mods.is(Given))
-          ~ keywordText("erased ").provided(vparam.mods.is(Erased))
           ~ toText(vparams, ", ") ~ ")"
     case untpd.TypeDefs(tparams) =>
       "[" ~ toText(tparams, ", ") ~ "]"
@@ -879,6 +877,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
   protected def valDefToText[T <: Untyped](tree: ValDef[T]): Text = {
     dclTextOr(tree) {
       modText(tree.mods, tree.symbol, keywordStr(if (tree.mods.is(Mutable)) "var" else "val"), isType = false) ~~
+        keywordText("erased ").provided(tree.mods.flags.is(Flags.Erased)) ~
         valDefText(nameIdText(tree)) ~ optAscription(tree.tpt) ~
         withEnclosingDef(tree) { optText(tree.rhs)(" = " ~ _) }
     }