expand: Move cfg-attrs related functions out of MacroExpander

The current situation where the MacroExpander and AttrVisitor recursively
call into each other is not great, and causes pains for macro imports. We
need to split this pass in two, with one pass being responsible for cfg-attr
checking and stripping, and one being responsible for macro expansion.

gcc/rust/ChangeLog:

	* expand/rust-macro-expand.cc (MacroExpander::expand_crate): Do not cfg-attr
	strip in MacroExpander
	(MacroExpander::fails_cfg): Function moved...
	(MacroExpander::fails_cfg_with_expand): Function moved...
	(MacroExpander::expand_cfg_attrs): Function moved...
	* expand/rust-attribute-visitor.cc (fails_cfg): ...here.
	(fails_cfg_with_expand): ...here.
	(expand_cfg_attrs): ...here.
	(AttrVisitor::expand_struct_fields): Use new functions.
	(AttrVisitor::expand_tuple_fields): Likewise.
	(AttrVisitor::expand_function_params): Likewise.
	(AttrVisitor::visit): Likewise.
	(AttrVisitor::go): New function.
	* expand/rust-attribute-visitor.h: Declare AttrVisitor::go.
	* expand/rust-macro-expand.h (struct MacroExpander): Remove cfg-attr related
	functions.

4 files changed, 329 insertions, 314 deletions

diff --git a/gcc/rust/expand/rust-attribute-visitor.cc b/gcc/rust/expand/rust-attribute-visitor.cc
index 13ae28c..7d86b6d 100644
--- a/gcc/rust/expand/rust-attribute-visitor.cc
+++ b/gcc/rust/expand/rust-attribute-visitor.cc
@@ -21,6 +21,129 @@
 
 namespace Rust {
 
+/**
+ * Determines whether any cfg predicate is false and hence item with attributes
+ * should be stripped. Note that attributes must be expanded before calling.
+ */
+bool
+fails_cfg (const AST::AttrVec &attrs)
+{
+  auto &session = Session::get_instance ();
+
+  for (const auto &attr : attrs)
+    {
+      if (attr.get_path () == "cfg" && !attr.check_cfg_predicate (session))
+	return true;
+    }
+  return false;
+}
+
+/**
+ * Determines whether any cfg predicate is false and hence item with attributes
+ * should be stripped. Will expand attributes as well.
+ */
+bool
+fails_cfg_with_expand (AST::AttrVec &attrs)
+{
+  auto &session = Session::get_instance ();
+
+  // TODO: maybe have something that strips cfg attributes that evaluate true?
+  for (auto &attr : attrs)
+    {
+      if (attr.get_path () == "cfg")
+	{
+	  if (!attr.is_parsed_to_meta_item ())
+	    attr.parse_attr_to_meta_item ();
+
+	  // DEBUG
+	  if (!attr.is_parsed_to_meta_item ())
+	    rust_debug ("failed to parse attr to meta item, right before "
+			"cfg predicate check");
+	  else
+	    rust_debug ("attr has been successfully parsed to meta item, "
+			"right before cfg predicate check");
+
+	  if (!attr.check_cfg_predicate (session))
+	    {
+	      // DEBUG
+	      rust_debug (
+		"cfg predicate failed for attribute: \033[0;31m'%s'\033[0m",
+		attr.as_string ().c_str ());
+
+	      return true;
+	    }
+	  else
+	    {
+	      // DEBUG
+	      rust_debug ("cfg predicate succeeded for attribute: "
+			  "\033[0;31m'%s'\033[0m",
+			  attr.as_string ().c_str ());
+	    }
+	}
+    }
+  return false;
+}
+
+/**
+ * Expands cfg_attr attributes.
+ */
+void
+expand_cfg_attrs (AST::AttrVec &attrs)
+{
+  auto &session = Session::get_instance ();
+
+  for (std::size_t i = 0; i < attrs.size (); i++)
+    {
+      auto &attr = attrs[i];
+      if (attr.get_path () == "cfg_attr")
+	{
+	  if (!attr.is_parsed_to_meta_item ())
+	    attr.parse_attr_to_meta_item ();
+
+	  if (attr.check_cfg_predicate (session))
+	    {
+	      // split off cfg_attr
+	      AST::AttrVec new_attrs = attr.separate_cfg_attrs ();
+
+	      // remove attr from vector
+	      attrs.erase (attrs.begin () + i);
+
+	      // add new attrs to vector
+	      attrs.insert (attrs.begin () + i,
+			    std::make_move_iterator (new_attrs.begin ()),
+			    std::make_move_iterator (new_attrs.end ()));
+	    }
+
+	  /* do something - if feature (first token in tree) is in fact enabled,
+	   * make tokens listed afterwards into attributes. i.e.: for
+	   * [cfg_attr(feature = "wow", wow1, wow2)], if "wow" is true, then add
+	   * attributes [wow1] and [wow2] to attribute list. This can also be
+	   * recursive, so check for expanded attributes being recursive and
+	   * possibly recursively call the expand_attrs? */
+	}
+      else
+	{
+	  i++;
+	}
+    }
+  attrs.shrink_to_fit ();
+}
+
+void
+AttrVisitor::go (AST::Crate &crate)
+{
+  // expand crate cfg_attr attributes
+  expand_cfg_attrs (crate.inner_attrs);
+
+  if (fails_cfg_with_expand (crate.inner_attrs))
+    {
+      // basically, delete whole crate
+      crate.strip_crate ();
+      // TODO: maybe create warning here? probably not desired behaviour
+    }
+  // expand module attributes?
+}
+
 // Visitor used to expand attributes.
 void
 AttrVisitor::expand_struct_fields (std::vector<AST::StructField> &fields)
@@ -30,8 +153,8 @@ AttrVisitor::expand_struct_fields (std::vector<AST::StructField> &fields)
       auto &field = *it;
 
       auto &field_attrs = field.get_outer_attrs ();
-      expander.expand_cfg_attrs (field_attrs);
-      if (expander.fails_cfg_with_expand (field_attrs))
+      expand_cfg_attrs (field_attrs);
+      if (fails_cfg_with_expand (field_attrs))
 	{
 	  it = fields.erase (it);
 	  continue;
@@ -64,8 +187,8 @@ AttrVisitor::expand_tuple_fields (std::vector<AST::TupleField> &fields)
       auto &field = *it;
 
       auto &field_attrs = field.get_outer_attrs ();
-      expander.expand_cfg_attrs (field_attrs);
-      if (expander.fails_cfg_with_expand (field_attrs))
+      expand_cfg_attrs (field_attrs);
+      if (fails_cfg_with_expand (field_attrs))
 	{
 	  it = fields.erase (it);
 	  continue;
@@ -93,8 +216,8 @@ AttrVisitor::expand_function_params (std::vector<AST::FunctionParam> &params)
       auto &param = *it;
 
       auto &param_attrs = param.get_outer_attrs ();
-      expander.expand_cfg_attrs (param_attrs);
-      if (expander.fails_cfg_with_expand (param_attrs))
+      expand_cfg_attrs (param_attrs);
+      if (fails_cfg_with_expand (param_attrs))
 	{
 	  it = params.erase (it);
 	  continue;
@@ -215,8 +338,8 @@ AttrVisitor::AttrVisitor::expand_closure_params (
       auto &param = *it;
 
       auto &param_attrs = param.get_outer_attrs ();
-      expander.expand_cfg_attrs (param_attrs);
-      if (expander.fails_cfg_with_expand (param_attrs))
+      expand_cfg_attrs (param_attrs);
+      if (fails_cfg_with_expand (param_attrs))
 	{
 	  it = params.erase (it);
 	  continue;
@@ -363,8 +486,8 @@ void
 AttrVisitor::visit (AST::IdentifierExpr &ident_expr)
 {
   // strip test based on outer attrs
-  expander.expand_cfg_attrs (ident_expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (ident_expr.get_outer_attrs ()))
+  expand_cfg_attrs (ident_expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (ident_expr.get_outer_attrs ()))
     {
       ident_expr.mark_for_strip ();
       return;
@@ -390,8 +513,8 @@ void
 AttrVisitor::visit (AST::MacroInvocation &macro_invoc)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (macro_invoc.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (macro_invoc.get_outer_attrs ()))
+  expand_cfg_attrs (macro_invoc.get_outer_attrs ());
+  if (fails_cfg_with_expand (macro_invoc.get_outer_attrs ()))
     {
       macro_invoc.mark_for_strip ();
       return;
@@ -409,8 +532,8 @@ void
 AttrVisitor::visit (AST::PathInExpression &path)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (path.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (path.get_outer_attrs ()))
+  expand_cfg_attrs (path.get_outer_attrs ());
+  if (fails_cfg_with_expand (path.get_outer_attrs ()))
     {
       path.mark_for_strip ();
       return;
@@ -477,8 +600,8 @@ void
 AttrVisitor::visit (AST::QualifiedPathInExpression &path)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (path.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (path.get_outer_attrs ()))
+  expand_cfg_attrs (path.get_outer_attrs ());
+  if (fails_cfg_with_expand (path.get_outer_attrs ()))
     {
       path.mark_for_strip ();
       return;
@@ -506,8 +629,8 @@ void
 AttrVisitor::visit (AST::LiteralExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -532,8 +655,8 @@ void
 AttrVisitor::visit (AST::BorrowExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -553,8 +676,8 @@ void
 AttrVisitor::visit (AST::DereferenceExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -574,8 +697,8 @@ void
 AttrVisitor::visit (AST::ErrorPropagationExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -595,8 +718,8 @@ void
 AttrVisitor::visit (AST::NegationExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -725,8 +848,8 @@ AttrVisitor::visit (AST::TypeCastExpr &expr)
 void
 AttrVisitor::visit (AST::AssignmentExpr &expr)
 {
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -788,8 +911,8 @@ void
 AttrVisitor::visit (AST::GroupedExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -797,8 +920,8 @@ AttrVisitor::visit (AST::GroupedExpr &expr)
 
   /* strip test based on inner attrs - spec says these are inner
    * attributes, not outer attributes of inner expr */
-  expander.expand_cfg_attrs (expr.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_inner_attrs ()))
+  expand_cfg_attrs (expr.get_inner_attrs ());
+  if (fails_cfg_with_expand (expr.get_inner_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -848,8 +971,8 @@ void
 AttrVisitor::visit (AST::ArrayExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -857,8 +980,8 @@ AttrVisitor::visit (AST::ArrayExpr &expr)
 
   /* strip test based on inner attrs - spec says there are separate
    * inner attributes, not just outer attributes of inner exprs */
-  expander.expand_cfg_attrs (expr.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_inner_attrs ()))
+  expand_cfg_attrs (expr.get_inner_attrs ());
+  if (fails_cfg_with_expand (expr.get_inner_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -875,8 +998,8 @@ AttrVisitor::visit (AST::ArrayIndexExpr &expr)
    * allowed, but conceptually it wouldn't make much sense, but
    * having expansion code anyway. TODO */
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -906,8 +1029,8 @@ AttrVisitor::visit (AST::TupleExpr &expr)
    * tuple expressions" */
 
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -915,8 +1038,8 @@ AttrVisitor::visit (AST::TupleExpr &expr)
 
   /* strip test based on inner attrs - spec says these are inner
    * attributes, not outer attributes of inner expr */
-  expander.expand_cfg_attrs (expr.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_inner_attrs ()))
+  expand_cfg_attrs (expr.get_inner_attrs ());
+  if (fails_cfg_with_expand (expr.get_inner_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -930,8 +1053,8 @@ void
 AttrVisitor::visit (AST::TupleIndexExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -951,8 +1074,8 @@ void
 AttrVisitor::visit (AST::StructExprStruct &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -960,8 +1083,8 @@ AttrVisitor::visit (AST::StructExprStruct &expr)
 
   /* strip test based on inner attrs - spec says these are inner
    * attributes, not outer attributes of inner expr */
-  expander.expand_cfg_attrs (expr.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_inner_attrs ()))
+  expand_cfg_attrs (expr.get_inner_attrs ());
+  if (fails_cfg_with_expand (expr.get_inner_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1007,8 +1130,8 @@ void
 AttrVisitor::visit (AST::StructExprStructFields &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1016,8 +1139,8 @@ AttrVisitor::visit (AST::StructExprStructFields &expr)
 
   /* strip test based on inner attrs - spec says these are inner
    * attributes, not outer attributes of inner expr */
-  expander.expand_cfg_attrs (expr.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_inner_attrs ()))
+  expand_cfg_attrs (expr.get_inner_attrs ());
+  if (fails_cfg_with_expand (expr.get_inner_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1056,8 +1179,8 @@ void
 AttrVisitor::visit (AST::StructExprStructBase &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1065,8 +1188,8 @@ AttrVisitor::visit (AST::StructExprStructBase &expr)
 
   /* strip test based on inner attrs - spec says these are inner
    * attributes, not outer attributes of inner expr */
-  expander.expand_cfg_attrs (expr.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_inner_attrs ()))
+  expand_cfg_attrs (expr.get_inner_attrs ());
+  if (fails_cfg_with_expand (expr.get_inner_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1093,8 +1216,8 @@ void
 AttrVisitor::visit (AST::CallExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1143,8 +1266,8 @@ void
 AttrVisitor::visit (AST::MethodCallExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1172,8 +1295,8 @@ void
 AttrVisitor::visit (AST::FieldAccessExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1193,8 +1316,8 @@ void
 AttrVisitor::visit (AST::ClosureExprInner &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1217,8 +1340,8 @@ void
 AttrVisitor::visit (AST::BlockExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1226,8 +1349,8 @@ AttrVisitor::visit (AST::BlockExpr &expr)
 
   /* strip test based on inner attrs - spec says there are inner
    * attributes, not just outer attributes of inner stmts */
-  expander.expand_cfg_attrs (expr.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_inner_attrs ()))
+  expand_cfg_attrs (expr.get_inner_attrs ());
+  if (fails_cfg_with_expand (expr.get_inner_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1236,10 +1359,10 @@ AttrVisitor::visit (AST::BlockExpr &expr)
   std::function<std::unique_ptr<AST::Stmt> (AST::SingleASTNode)> extractor
     = [] (AST::SingleASTNode node) { return node.take_stmt (); };
 
-  expand_macro_children (MacroExpander::BLOCK, expr.get_statements (),
-			 extractor);
+  expand_macro_children (MacroExpander::ContextType::BLOCK,
+			 expr.get_statements (), extractor);
 
-  expander.push_context (MacroExpander::BLOCK);
+  expander.push_context (MacroExpander::ContextType::BLOCK);
 
   // strip tail expression if exists - can actually fully remove it
   if (expr.has_tail_expr ())
@@ -1259,8 +1382,8 @@ void
 AttrVisitor::visit (AST::ClosureExprInnerTyped &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1295,8 +1418,8 @@ void
 AttrVisitor::visit (AST::ContinueExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1306,8 +1429,8 @@ void
 AttrVisitor::visit (AST::BreakExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1436,8 +1559,8 @@ void
 AttrVisitor::visit (AST::ReturnExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1467,8 +1590,8 @@ void
 AttrVisitor::visit (AST::UnsafeBlockExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1486,8 +1609,8 @@ void
 AttrVisitor::visit (AST::LoopExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1505,8 +1628,8 @@ void
 AttrVisitor::visit (AST::WhileLoopExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1532,8 +1655,8 @@ void
 AttrVisitor::visit (AST::WhileLetLoopExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1567,8 +1690,8 @@ void
 AttrVisitor::visit (AST::ForLoopExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1604,8 +1727,8 @@ AttrVisitor::visit (AST::IfExpr &expr)
   // when used as statement
 
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1632,8 +1755,8 @@ void
 AttrVisitor::visit (AST::IfExprConseqElse &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1668,8 +1791,8 @@ void
 AttrVisitor::visit (AST::IfExprConseqIf &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1704,8 +1827,8 @@ void
 AttrVisitor::visit (AST::IfExprConseqIfLet &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1741,8 +1864,8 @@ void
 AttrVisitor::visit (AST::IfLetExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1776,8 +1899,8 @@ void
 AttrVisitor::visit (AST::IfLetExprConseqElse &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1819,8 +1942,8 @@ void
 AttrVisitor::visit (AST::IfLetExprConseqIf &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1862,8 +1985,8 @@ void
 AttrVisitor::visit (AST::IfLetExprConseqIfLet &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1906,16 +2029,16 @@ void
 AttrVisitor::visit (AST::MatchExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
     }
 
   // inner attr strip test
-  expander.expand_cfg_attrs (expr.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_inner_attrs ()))
+  expand_cfg_attrs (expr.get_inner_attrs ());
+  if (fails_cfg_with_expand (expr.get_inner_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -1937,8 +2060,8 @@ AttrVisitor::visit (AST::MatchExpr &expr)
 
       // strip match case based on outer attributes in match arm
       auto &match_arm = match_case.get_arm ();
-      expander.expand_cfg_attrs (match_arm.get_outer_attrs ());
-      if (expander.fails_cfg_with_expand (match_arm.get_outer_attrs ()))
+      expand_cfg_attrs (match_arm.get_outer_attrs ());
+      if (fails_cfg_with_expand (match_arm.get_outer_attrs ()))
 	{
 	  // strip match case
 	  it = match_cases.erase (it);
@@ -1983,8 +2106,8 @@ void
 AttrVisitor::visit (AST::AwaitExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -2003,8 +2126,8 @@ void
 AttrVisitor::visit (AST::AsyncBlockExpr &expr)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (expr.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (expr.get_outer_attrs ()))
+  expand_cfg_attrs (expr.get_outer_attrs ());
+  if (fails_cfg_with_expand (expr.get_outer_attrs ()))
     {
       expr.mark_for_strip ();
       return;
@@ -2076,8 +2199,8 @@ void
 AttrVisitor::visit (AST::Method &method)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (method.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (method.get_outer_attrs ()))
+  expand_cfg_attrs (method.get_outer_attrs ());
+  if (fails_cfg_with_expand (method.get_outer_attrs ()))
     {
       method.mark_for_strip ();
       return;
@@ -2129,8 +2252,8 @@ void
 AttrVisitor::visit (AST::Module &module)
 {
   // strip test based on outer attrs
-  expander.expand_cfg_attrs (module.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (module.get_outer_attrs ()))
+  expand_cfg_attrs (module.get_outer_attrs ());
+  if (fails_cfg_with_expand (module.get_outer_attrs ()))
     {
       module.mark_for_strip ();
       return;
@@ -2140,8 +2263,8 @@ AttrVisitor::visit (AST::Module &module)
   if (module.get_kind () == AST::Module::ModuleKind::LOADED)
     {
       // strip test based on inner attrs
-      expander.expand_cfg_attrs (module.get_inner_attrs ());
-      if (expander.fails_cfg_with_expand (module.get_inner_attrs ()))
+      expand_cfg_attrs (module.get_inner_attrs ());
+      if (fails_cfg_with_expand (module.get_inner_attrs ()))
 	{
 	  module.mark_for_strip ();
 	  return;
@@ -2155,8 +2278,8 @@ void
 AttrVisitor::visit (AST::ExternCrate &extern_crate)
 {
   // strip test based on outer attrs
-  expander.expand_cfg_attrs (extern_crate.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (extern_crate.get_outer_attrs ()))
+  expand_cfg_attrs (extern_crate.get_outer_attrs ());
+  if (fails_cfg_with_expand (extern_crate.get_outer_attrs ()))
     {
       extern_crate.mark_for_strip ();
       return;
@@ -2188,8 +2311,8 @@ void
 AttrVisitor::visit (AST::UseDeclaration &use_decl)
 {
   // strip test based on outer attrs
-  expander.expand_cfg_attrs (use_decl.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (use_decl.get_outer_attrs ()))
+  expand_cfg_attrs (use_decl.get_outer_attrs ());
+  if (fails_cfg_with_expand (use_decl.get_outer_attrs ()))
     {
       use_decl.mark_for_strip ();
       return;
@@ -2199,8 +2322,8 @@ void
 AttrVisitor::visit (AST::Function &function)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (function.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (function.get_outer_attrs ()))
+  expand_cfg_attrs (function.get_outer_attrs ());
+  if (fails_cfg_with_expand (function.get_outer_attrs ()))
     {
       function.mark_for_strip ();
       return;
@@ -2247,8 +2370,8 @@ void
 AttrVisitor::visit (AST::TypeAlias &type_alias)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (type_alias.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (type_alias.get_outer_attrs ()))
+  expand_cfg_attrs (type_alias.get_outer_attrs ());
+  if (fails_cfg_with_expand (type_alias.get_outer_attrs ()))
     {
       type_alias.mark_for_strip ();
       return;
@@ -2270,8 +2393,8 @@ void
 AttrVisitor::visit (AST::StructStruct &struct_item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (struct_item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (struct_item.get_outer_attrs ()))
+  expand_cfg_attrs (struct_item.get_outer_attrs ());
+  if (fails_cfg_with_expand (struct_item.get_outer_attrs ()))
     {
       struct_item.mark_for_strip ();
       return;
@@ -2292,8 +2415,8 @@ void
 AttrVisitor::visit (AST::TupleStruct &tuple_struct)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (tuple_struct.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (tuple_struct.get_outer_attrs ()))
+  expand_cfg_attrs (tuple_struct.get_outer_attrs ());
+  if (fails_cfg_with_expand (tuple_struct.get_outer_attrs ()))
     {
       tuple_struct.mark_for_strip ();
       return;
@@ -2314,8 +2437,8 @@ void
 AttrVisitor::visit (AST::EnumItem &item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  expand_cfg_attrs (item.get_outer_attrs ());
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     {
       item.mark_for_strip ();
       return;
@@ -2325,8 +2448,8 @@ void
 AttrVisitor::visit (AST::EnumItemTuple &item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  expand_cfg_attrs (item.get_outer_attrs ());
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     {
       item.mark_for_strip ();
       return;
@@ -2340,8 +2463,8 @@ void
 AttrVisitor::visit (AST::EnumItemStruct &item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  expand_cfg_attrs (item.get_outer_attrs ());
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     {
       item.mark_for_strip ();
       return;
@@ -2355,8 +2478,8 @@ void
 AttrVisitor::visit (AST::EnumItemDiscriminant &item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  expand_cfg_attrs (item.get_outer_attrs ());
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     {
       item.mark_for_strip ();
       return;
@@ -2376,8 +2499,8 @@ void
 AttrVisitor::visit (AST::Enum &enum_item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (enum_item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (enum_item.get_outer_attrs ()))
+  expand_cfg_attrs (enum_item.get_outer_attrs ());
+  if (fails_cfg_with_expand (enum_item.get_outer_attrs ()))
     {
       enum_item.mark_for_strip ();
       return;
@@ -2398,8 +2521,8 @@ void
 AttrVisitor::visit (AST::Union &union_item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (union_item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (union_item.get_outer_attrs ()))
+  expand_cfg_attrs (union_item.get_outer_attrs ());
+  if (fails_cfg_with_expand (union_item.get_outer_attrs ()))
     {
       union_item.mark_for_strip ();
       return;
@@ -2420,8 +2543,8 @@ void
 AttrVisitor::visit (AST::ConstantItem &const_item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (const_item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (const_item.get_outer_attrs ()))
+  expand_cfg_attrs (const_item.get_outer_attrs ());
+  if (fails_cfg_with_expand (const_item.get_outer_attrs ()))
     {
       const_item.mark_for_strip ();
       return;
@@ -2454,8 +2577,8 @@ void
 AttrVisitor::visit (AST::StaticItem &static_item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (static_item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (static_item.get_outer_attrs ()))
+  expand_cfg_attrs (static_item.get_outer_attrs ());
+  if (fails_cfg_with_expand (static_item.get_outer_attrs ()))
     {
       static_item.mark_for_strip ();
       return;
@@ -2488,8 +2611,8 @@ void
 AttrVisitor::visit (AST::TraitItemFunc &item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  expand_cfg_attrs (item.get_outer_attrs ());
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     {
       item.mark_for_strip ();
       return;
@@ -2514,8 +2637,8 @@ void
 AttrVisitor::visit (AST::TraitItemMethod &item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  expand_cfg_attrs (item.get_outer_attrs ());
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     {
       item.mark_for_strip ();
       return;
@@ -2540,8 +2663,8 @@ void
 AttrVisitor::visit (AST::TraitItemConst &item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  expand_cfg_attrs (item.get_outer_attrs ());
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     {
       item.mark_for_strip ();
       return;
@@ -2577,8 +2700,8 @@ void
 AttrVisitor::visit (AST::TraitItemType &item)
 {
   // initial test based on outer attrs
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  expand_cfg_attrs (item.get_outer_attrs ());
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     {
       item.mark_for_strip ();
       return;
@@ -2595,16 +2718,16 @@ void
 AttrVisitor::visit (AST::Trait &trait)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (trait.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (trait.get_outer_attrs ()))
+  expand_cfg_attrs (trait.get_outer_attrs ());
+  if (fails_cfg_with_expand (trait.get_outer_attrs ()))
     {
       trait.mark_for_strip ();
       return;
     }
 
   // strip test based on inner attrs
-  expander.expand_cfg_attrs (trait.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (trait.get_inner_attrs ()))
+  expand_cfg_attrs (trait.get_inner_attrs ());
+  if (fails_cfg_with_expand (trait.get_inner_attrs ()))
     {
       trait.mark_for_strip ();
       return;
@@ -2627,23 +2750,23 @@ AttrVisitor::visit (AST::Trait &trait)
   std::function<std::unique_ptr<AST::TraitItem> (AST::SingleASTNode)> extractor
     = [] (AST::SingleASTNode node) { return node.take_trait_item (); };
 
-  expand_macro_children (MacroExpander::TRAIT, trait.get_trait_items (),
-			 extractor);
+  expand_macro_children (MacroExpander::ContextType::TRAIT,
+			 trait.get_trait_items (), extractor);
 }
 void
 AttrVisitor::visit (AST::InherentImpl &impl)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (impl.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (impl.get_outer_attrs ()))
+  expand_cfg_attrs (impl.get_outer_attrs ());
+  if (fails_cfg_with_expand (impl.get_outer_attrs ()))
     {
       impl.mark_for_strip ();
       return;
     }
 
   // strip test based on inner attrs
-  expander.expand_cfg_attrs (impl.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (impl.get_inner_attrs ()))
+  expand_cfg_attrs (impl.get_inner_attrs ());
+  if (fails_cfg_with_expand (impl.get_inner_attrs ()))
     {
       impl.mark_for_strip ();
       return;
@@ -2671,23 +2794,23 @@ AttrVisitor::visit (AST::InherentImpl &impl)
   std::function<std::unique_ptr<AST::InherentImplItem> (AST::SingleASTNode)>
     extractor = [] (AST::SingleASTNode node) { return node.take_impl_item (); };
 
-  expand_macro_children (MacroExpander::IMPL, impl.get_impl_items (),
-			 extractor);
+  expand_macro_children (MacroExpander::ContextType::IMPL,
+			 impl.get_impl_items (), extractor);
 }
 void
 AttrVisitor::visit (AST::TraitImpl &impl)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (impl.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (impl.get_outer_attrs ()))
+  expand_cfg_attrs (impl.get_outer_attrs ());
+  if (fails_cfg_with_expand (impl.get_outer_attrs ()))
     {
       impl.mark_for_strip ();
       return;
     }
 
   // strip test based on inner attrs
-  expander.expand_cfg_attrs (impl.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (impl.get_inner_attrs ()))
+  expand_cfg_attrs (impl.get_inner_attrs ());
+  if (fails_cfg_with_expand (impl.get_inner_attrs ()))
     {
       impl.mark_for_strip ();
       return;
@@ -2722,16 +2845,16 @@ AttrVisitor::visit (AST::TraitImpl &impl)
     extractor
     = [] (AST::SingleASTNode node) { return node.take_trait_impl_item (); };
 
-  expand_macro_children (MacroExpander::TRAIT_IMPL, impl.get_impl_items (),
-			 extractor);
+  expand_macro_children (MacroExpander::ContextType::TRAIT_IMPL,
+			 impl.get_impl_items (), extractor);
 }
 
 void
 AttrVisitor::visit (AST::ExternalTypeItem &item)
 {
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
+  expand_cfg_attrs (item.get_outer_attrs ());
 
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     item.mark_for_strip ();
 
   // TODO: Can we do anything like expand a macro here?
@@ -2743,8 +2866,8 @@ void
 AttrVisitor::visit (AST::ExternalStaticItem &item)
 {
   // strip test based on outer attrs
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  expand_cfg_attrs (item.get_outer_attrs ());
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     {
       item.mark_for_strip ();
       return;
@@ -2767,8 +2890,8 @@ void
 AttrVisitor::visit (AST::ExternalFunctionItem &item)
 {
   // strip test based on outer attrs
-  expander.expand_cfg_attrs (item.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (item.get_outer_attrs ()))
+  expand_cfg_attrs (item.get_outer_attrs ());
+  if (fails_cfg_with_expand (item.get_outer_attrs ()))
     {
       item.mark_for_strip ();
       return;
@@ -2786,8 +2909,8 @@ AttrVisitor::visit (AST::ExternalFunctionItem &item)
       auto &param = *it;
 
       auto &param_attrs = param.get_outer_attrs ();
-      expander.expand_cfg_attrs (param_attrs);
-      if (expander.fails_cfg_with_expand (param_attrs))
+      expand_cfg_attrs (param_attrs);
+      if (fails_cfg_with_expand (param_attrs))
 	{
 	  it = params.erase (it);
 	  continue;
@@ -2840,16 +2963,16 @@ void
 AttrVisitor::visit (AST::ExternBlock &block)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (block.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (block.get_outer_attrs ()))
+  expand_cfg_attrs (block.get_outer_attrs ());
+  if (fails_cfg_with_expand (block.get_outer_attrs ()))
     {
       block.mark_for_strip ();
       return;
     }
 
   // strip test based on inner attrs
-  expander.expand_cfg_attrs (block.get_inner_attrs ());
-  if (expander.fails_cfg_with_expand (block.get_inner_attrs ()))
+  expand_cfg_attrs (block.get_inner_attrs ());
+  if (fails_cfg_with_expand (block.get_inner_attrs ()))
     {
       block.mark_for_strip ();
       return;
@@ -2859,8 +2982,8 @@ AttrVisitor::visit (AST::ExternBlock &block)
     extractor
     = [] (AST::SingleASTNode node) { return node.take_external_item (); };
 
-  expand_macro_children (MacroExpander::EXTERN, block.get_extern_items (),
-			 extractor);
+  expand_macro_children (MacroExpander::ContextType::EXTERN,
+			 block.get_extern_items (), extractor);
 }
 
 // I don't think it would be possible to strip macros without expansion
@@ -2877,8 +3000,8 @@ void
 AttrVisitor::visit (AST::MacroRulesDefinition &rules_def)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (rules_def.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (rules_def.get_outer_attrs ()))
+  expand_cfg_attrs (rules_def.get_outer_attrs ());
+  if (fails_cfg_with_expand (rules_def.get_outer_attrs ()))
     {
       rules_def.mark_for_strip ();
       return;
@@ -2975,8 +3098,8 @@ void
 AttrVisitor::visit (AST::StructPatternFieldTuplePat &field)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (field.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (field.get_outer_attrs ()))
+  expand_cfg_attrs (field.get_outer_attrs ());
+  if (fails_cfg_with_expand (field.get_outer_attrs ()))
     {
       field.mark_for_strip ();
       return;
@@ -2993,8 +3116,8 @@ void
 AttrVisitor::visit (AST::StructPatternFieldIdentPat &field)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (field.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (field.get_outer_attrs ()))
+  expand_cfg_attrs (field.get_outer_attrs ());
+  if (fails_cfg_with_expand (field.get_outer_attrs ()))
     {
       field.mark_for_strip ();
       return;
@@ -3011,8 +3134,8 @@ void
 AttrVisitor::visit (AST::StructPatternFieldIdent &field)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (field.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (field.get_outer_attrs ()))
+  expand_cfg_attrs (field.get_outer_attrs ());
+  if (fails_cfg_with_expand (field.get_outer_attrs ()))
     {
       field.mark_for_strip ();
       return;
@@ -3040,8 +3163,8 @@ AttrVisitor::visit (AST::StructPattern &pattern)
   // assuming you can strip the ".." part
   if (elems.has_etc ())
     {
-      expander.expand_cfg_attrs (elems.get_etc_outer_attrs ());
-      if (expander.fails_cfg_with_expand (elems.get_etc_outer_attrs ()))
+      expand_cfg_attrs (elems.get_etc_outer_attrs ());
+      if (fails_cfg_with_expand (elems.get_etc_outer_attrs ()))
 	elems.strip_etc ();
     }
 }
@@ -3187,8 +3310,8 @@ void
 AttrVisitor::visit (AST::LetStmt &stmt)
 {
   // initial strip test based on outer attrs
-  expander.expand_cfg_attrs (stmt.get_outer_attrs ());
-  if (expander.fails_cfg_with_expand (stmt.get_outer_attrs ()))
+  expand_cfg_attrs (stmt.get_outer_attrs ());
+  if (fails_cfg_with_expand (stmt.get_outer_attrs ()))
     {
       stmt.mark_for_strip ();
       return;
@@ -3401,8 +3524,8 @@ AttrVisitor::visit (AST::BareFunctionType &type)
       auto &param = *it;
 
       auto &param_attrs = param.get_outer_attrs ();
-      expander.expand_cfg_attrs (param_attrs);
-      if (expander.fails_cfg_with_expand (param_attrs))
+      expand_cfg_attrs (param_attrs);
+      if (fails_cfg_with_expand (param_attrs))
 	{
 	  it = params.erase (it);
 	  continue;
diff --git a/gcc/rust/expand/rust-attribute-visitor.h b/gcc/rust/expand/rust-attribute-visitor.h
index ceada60..132a896 100644
--- a/gcc/rust/expand/rust-attribute-visitor.h
+++ b/gcc/rust/expand/rust-attribute-visitor.h
@@ -32,6 +32,9 @@ private:
 public:
   AttrVisitor (MacroExpander &expander) : expander (expander) {}
 
+  /* Run the AttrVisitor on an entire crate */
+  void go (AST::Crate &crate);
+
   void expand_struct_fields (std::vector<AST::StructField> &fields);
   void expand_tuple_fields (std::vector<AST::TupleField> &fields);
   void expand_function_params (std::vector<AST::FunctionParam> &params);
diff --git a/gcc/rust/expand/rust-macro-expand.cc b/gcc/rust/expand/rust-macro-expand.cc
index 71aafef..28ba563 100644
--- a/gcc/rust/expand/rust-macro-expand.cc
+++ b/gcc/rust/expand/rust-macro-expand.cc
@@ -285,102 +285,6 @@ MacroExpander::expand_invoc (AST::MacroInvocation &invoc, bool has_semicolon)
   set_expanded_fragment (std::move (fragment));
 }
 
-/* Determines whether any cfg predicate is false and hence item with attributes
- * should be stripped. Note that attributes must be expanded before calling. */
-bool
-MacroExpander::fails_cfg (const AST::AttrVec &attrs) const
-{
-  for (const auto &attr : attrs)
-    {
-      if (attr.get_path () == "cfg" && !attr.check_cfg_predicate (session))
-	return true;
-    }
-  return false;
-}
-
-/* Determines whether any cfg predicate is false and hence item with attributes
- * should be stripped. Will expand attributes as well. */
-bool
-MacroExpander::fails_cfg_with_expand (AST::AttrVec &attrs) const
-{
-  // TODO: maybe have something that strips cfg attributes that evaluate true?
-  for (auto &attr : attrs)
-    {
-      if (attr.get_path () == "cfg")
-	{
-	  if (!attr.is_parsed_to_meta_item ())
-	    attr.parse_attr_to_meta_item ();
-
-	  // DEBUG
-	  if (!attr.is_parsed_to_meta_item ())
-	    rust_debug ("failed to parse attr to meta item, right before "
-			"cfg predicate check");
-	  else
-	    rust_debug ("attr has been successfully parsed to meta item, "
-			"right before cfg predicate check");
-
-	  if (!attr.check_cfg_predicate (session))
-	    {
-	      // DEBUG
-	      rust_debug (
-		"cfg predicate failed for attribute: \033[0;31m'%s'\033[0m",
-		attr.as_string ().c_str ());
-
-	      return true;
-	    }
-	  else
-	    {
-	      // DEBUG
-	      rust_debug ("cfg predicate succeeded for attribute: "
-			  "\033[0;31m'%s'\033[0m",
-			  attr.as_string ().c_str ());
-	    }
-	}
-    }
-  return false;
-}
-
-// Expands cfg_attr attributes.
-void
-MacroExpander::expand_cfg_attrs (AST::AttrVec &attrs)
-{
-  for (std::size_t i = 0; i < attrs.size (); i++)
-    {
-      auto &attr = attrs[i];
-      if (attr.get_path () == "cfg_attr")
-	{
-	  if (!attr.is_parsed_to_meta_item ())
-	    attr.parse_attr_to_meta_item ();
-
-	  if (attr.check_cfg_predicate (session))
-	    {
-	      // split off cfg_attr
-	      AST::AttrVec new_attrs = attr.separate_cfg_attrs ();
-
-	      // remove attr from vector
-	      attrs.erase (attrs.begin () + i);
-
-	      // add new attrs to vector
-	      attrs.insert (attrs.begin () + i,
-			    std::make_move_iterator (new_attrs.begin ()),
-			    std::make_move_iterator (new_attrs.end ()));
-	    }
-
-	  /* do something - if feature (first token in tree) is in fact enabled,
-	   * make tokens listed afterwards into attributes. i.e.: for
-	   * [cfg_attr(feature = "wow", wow1, wow2)], if "wow" is true, then add
-	   * attributes [wow1] and [wow2] to attribute list. This can also be
-	   * recursive, so check for expanded attributes being recursive and
-	   * possibly recursively call the expand_attrs? */
-	}
-      else
-	{
-	  i++;
-	}
-    }
-  attrs.shrink_to_fit ();
-}
-
 void
 MacroExpander::expand_crate ()
 {
@@ -393,17 +297,6 @@ MacroExpander::expand_crate ()
   // TODO: does cfg apply for inner attributes? research.
   // the apparent answer (from playground test) is yes
 
-  // expand crate cfg_attr attributes
-  expand_cfg_attrs (crate.inner_attrs);
-
-  if (fails_cfg_with_expand (crate.inner_attrs))
-    {
-      // basically, delete whole crate
-      crate.strip_crate ();
-      // TODO: maybe create warning here? probably not desired behaviour
-    }
-  // expand module attributes?
-
   push_context (ITEM);
 
   // expand attributes recursively and strip items if required
diff --git a/gcc/rust/expand/rust-macro-expand.h b/gcc/rust/expand/rust-macro-expand.h
index 9471416..aea761b 100644
--- a/gcc/rust/expand/rust-macro-expand.h
+++ b/gcc/rust/expand/rust-macro-expand.h
@@ -256,10 +256,6 @@ struct MacroExpander
 				   AST::MacroRulesDefinition &rules_def,
 				   bool semicolon);
 
-  void expand_cfg_attrs (AST::AttrVec &attrs);
-  bool fails_cfg (const AST::AttrVec &attr) const;
-  bool fails_cfg_with_expand (AST::AttrVec &attrs) const;
-
   bool depth_exceeds_recursion_limit () const;
 
   bool try_match_rule (AST::MacroRule &match_rule,