Require namespace-scope objects to have a concrete type, closes hsutter#315

Author: hsutter

source/parse.h

@@ -1934,7 +1934,7 @@ struct declaration_node
  ;
  }
 
- auto is_wildcard() const
+ auto has_wildcard_type() const
  -> bool
  {
  return
@@ -5488,6 +5488,14 @@ class parser
  // First see if it's an alias declaration
  n = alias();
  if (n) {
+ if (is_parameter) {
+ errors.emplace_back(
+ curr().position(),
+ "a parameter declaration may not be an alias declaration"
+ );
+ return {};
+ }
+
  n->pos = start_pos;
  n->identifier = std::move(id);
  n->access = access;
@@ -5513,6 +5521,20 @@ class parser
 
  // Note: Do this after trying to parse this as a declaration, for parse backtracking
 
+ if (
+ !is_parameter
+ && n->is_object()
+ && n->has_wildcard_type()
+ && n->parent_is_namespace()
+ )
+ {
+ errors.emplace_back(
+ n->identifier->position(),
+ "namespace scope objects must have a concrete type, not a deduced type"
+ );
+ return {};
+ }
+
  if (
  n->has_name("_")
  && !n->is_object()