pass typedesc as NimNode to macros (#11400)

* change typedesc's design in macros

* Manual and changelog entry.

* add link to RFC

compiler/semstmts.nim

@@ -1554,11 +1554,7 @@ proc activate(c: PContext, n: PNode) =
 
 proc maybeAddResult(c: PContext, s: PSym, n: PNode) =
   if s.kind == skMacro:
-    let resultType =
-      if s.typ.sons[0] != nil and s.typ.sons[0].kind == tyTypeDesc:
-        s.typ.sons[0]
-      else:
-        sysTypeFromName(c.graph, n.info, "NimNode")
+    let resultType = sysTypeFromName(c.graph, n.info, "NimNode")
     addResult(c, resultType, n.info, s.kind)
     addResultNode(c, n)
   elif s.typ.sons[0] != nil and not isInlineIterator(s):

compiler/semtypes.nim

@@ -869,8 +869,8 @@ proc addParamOrResult(c: PContext, param: PSym, kind: TSymKind) =
       var a = copySym(param)
       a.typ = staticType.base
       addDecl(c, a)
-    elif param.typ != nil and param.typ.kind == tyTypeDesc:
-      addDecl(c, param)
+      #elif param.typ != nil and param.typ.kind == tyTypeDesc:
+      #  addDecl(c, param)
     else:
       # within a macro, every param has the type NimNode!
       let nn = getSysSym(c.graph, param.info, "NimNode")

compiler/vm.nim

@@ -2028,8 +2028,8 @@ proc setupMacroParam(x: PNode, typ: PType): TFullReg =
   case typ.kind
   of tyStatic:
     putIntoReg(result, x)
-  of tyTypeDesc:
-    putIntoReg(result, x)
+  #of tyTypeDesc:
+  #  putIntoReg(result, x)
   else:
     result.kind = rkNode
     var n = x