Fixes #5167 and related problems (#5475)

This commit returns to a bit less strict checking of the number
of macro arguments, because some old immediate macros rely on a
behavior where even the arity of the macro is not being checked.

It may be better if such macros are just declared to use varargs[expr],
but this remains for another day.

compiler/semstmts.nim

@@ -499,6 +499,8 @@ proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
         if hasEmpty(typ):
           localError(def.info, errCannotInferTypeOfTheLiteral,
                      ($typ.kind).substr(2).toLowerAscii)
+        elif typ.kind == tyProc and tfUnresolved in typ.flags:
+          localError(def.info, errProcHasNoConcreteType, def.renderTree)
     else:
       if symkind == skLet: localError(a.info, errLetNeedsInit)