Merge #1607

1607: Improve AST Fragment class r=CohenArthur a=CohenArthur

This changes the APIs around creating AST fragments and refactors the class into its own header and source file, hopefully making it easier to use. This will also help creating "unexpanded" AST fragments for proper builtin macro expansion with the new fixed-point algorithm introduced by #1606 

`@liushuyu` pinging you since you've worked extensively with the macro system. Would love your review!

Co-authored-by: Arthur Cohen <arthur.cohen@embecosm.com>

1 files changed, 171 insertions, 0 deletions

diff --git a/gcc/rust/ast/rust-ast-fragment.cc b/gcc/rust/ast/rust-ast-fragment.cc
new file mode 100644
index 0000000..c491609
--- /dev/null
+++ b/gcc/rust/ast/rust-ast-fragment.cc
@@ -0,0 +1,171 @@
+// Copyright (C) 2020-2022 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include "rust-ast-fragment.h"
+
+namespace Rust {
+namespace AST {
+
+Fragment::Fragment (FragmentKind kind, std::vector<SingleASTNode> nodes)
+  : kind (kind), nodes (std::move (nodes))
+{}
+
+Fragment::Fragment (Fragment const &other) : kind (other.get_kind ())
+{
+  *this = other;
+}
+
+Fragment &
+Fragment::operator= (Fragment const &other)
+{
+  nodes.clear ();
+  nodes.reserve (other.nodes.size ());
+  kind = other.get_kind ();
+  for (auto &n : other.nodes)
+    {
+      nodes.push_back (n);
+    }
+
+  return *this;
+}
+
+Fragment
+Fragment::create_error ()
+{
+  return Fragment (FragmentKind::Error, {});
+}
+
+Fragment
+Fragment::complete (std::vector<AST::SingleASTNode> nodes)
+{
+  return Fragment (FragmentKind::Complete, std::move (nodes));
+}
+
+Fragment
+Fragment::unexpanded ()
+{
+  return Fragment (FragmentKind::Unexpanded, {});
+}
+
+std::vector<SingleASTNode> &
+Fragment::get_nodes ()
+{
+  return nodes;
+}
+
+FragmentKind
+Fragment::get_kind () const
+{
+  return kind;
+}
+
+bool
+Fragment::is_error () const
+{
+  return get_kind () == FragmentKind::Error;
+}
+
+bool
+Fragment::should_expand () const
+{
+  return !is_error ();
+}
+
+bool
+Fragment::is_expression_fragment () const
+{
+  return is_single_fragment_of_kind (SingleASTNode::NodeType::EXPRESSION);
+}
+
+bool
+Fragment::is_type_fragment () const
+{
+  return is_single_fragment_of_kind (SingleASTNode::NodeType::TYPE);
+}
+
+std::unique_ptr<Expr>
+Fragment::take_expression_fragment ()
+{
+  assert_single_fragment (SingleASTNode::NodeType::EXPRESSION);
+  return nodes[0].take_expr ();
+}
+
+std::unique_ptr<Type>
+Fragment::take_type_fragment ()
+{
+  assert_single_fragment (SingleASTNode::NodeType::TYPE);
+  return nodes[0].take_type ();
+}
+
+void
+Fragment::accept_vis (ASTVisitor &vis)
+{
+  for (auto &node : nodes)
+    node.accept_vis (vis);
+}
+
+bool
+Fragment::is_single_fragment () const
+{
+  return nodes.size () == 1;
+}
+
+bool
+Fragment::is_single_fragment_of_kind (SingleASTNode::NodeType expected) const
+{
+  return is_single_fragment () && nodes[0].get_kind () == expected;
+}
+
+void
+Fragment::assert_single_fragment (SingleASTNode::NodeType expected) const
+{
+  static const std::map<SingleASTNode::NodeType, const char *> str_map = {
+    {SingleASTNode::NodeType::IMPL, "impl"},
+    {SingleASTNode::NodeType::ITEM, "item"},
+    {SingleASTNode::NodeType::TYPE, "type"},
+    {SingleASTNode::NodeType::EXPRESSION, "expr"},
+    {SingleASTNode::NodeType::STMT, "stmt"},
+    {SingleASTNode::NodeType::EXTERN, "extern"},
+    {SingleASTNode::NodeType::TRAIT, "trait"},
+    {SingleASTNode::NodeType::TRAIT_IMPL, "trait impl"},
+  };
+
+  auto actual = nodes[0].get_kind ();
+  auto fail = false;
+
+  if (!is_single_fragment ())
+    {
+      rust_error_at (Location (), "fragment is not single");
+      fail = true;
+    }
+
+  if (actual != expected)
+    {
+      rust_error_at (
+	Location (),
+	"invalid fragment operation: expected %qs node, got %qs node",
+	str_map.find (expected)->second,
+	str_map.find (nodes[0].get_kind ())->second);
+      fail = true;
+    }
+
+  rust_assert (!fail);
+}
+
+} // namespace AST
+} // namespace Rust