Eliminate moved_ref

Use real rvalue references instead

src/common.h

@@ -479,15 +479,6 @@ inline wcstring to_string(const int &x) {
     return to_string(static_cast<long>(x));
 }
 
-// A hackish thing to simulate rvalue references in C++98. The idea is that you can define a
-// constructor to take a moved_ref<T> and then swap() out of it.
-template <typename T>
-struct moved_ref {
-    T &val;
-
-    explicit moved_ref(T &v) : val(v) {}
-};
-
 wchar_t **make_null_terminated_array(const wcstring_list_t &lst);
 char **make_null_terminated_array(const std::vector<std::string> &lst);
 

src/parse_execution.cpp

@@ -75,10 +75,10 @@ static wcstring profiling_cmd_name_for_redirectable_block(const parse_node_t &no
     return result;
 }
 
-parse_execution_context_t::parse_execution_context_t(moved_ref<parse_node_tree_t> t,
+parse_execution_context_t::parse_execution_context_t(parse_node_tree_t t,
                                                      const wcstring &s, parser_t *p,
                                                      int initial_eval_level)
-    : tree(t),
+    : tree(std::move(t)),
       src(s),
       parser(p),
       eval_level(initial_eval_level),

src/parse_execution.h

@@ -127,7 +127,7 @@ class parse_execution_context_t {
     int line_offset_of_character_at_offset(size_t char_idx);
 
    public:
-    parse_execution_context_t(moved_ref<parse_node_tree_t> t, const wcstring &s, parser_t *p,
+    parse_execution_context_t(parse_node_tree_t t, const wcstring &s, parser_t *p,
                               int initial_eval_level);
 
     /// Returns the current eval level.

src/parse_tree.cpp

@@ -603,15 +603,11 @@ void parse_ll_t::determine_node_ranges(void) {
 
 void parse_ll_t::acquire_output(parse_node_tree_t *output, parse_error_list_t *errors) {
     if (output != NULL) {
-        output->swap(this->nodes);
+        *output = std::move(this->nodes);
     }
-    this->nodes.clear();
-
     if (errors != NULL) {
-        errors->swap(this->errors);
+        *errors = std::move(this->errors);
     }
-    this->errors.clear();
-    this->symbol_stack.clear();
 }
 
 void parse_ll_t::parse_error(parse_token_t token, parse_error_code_t code, const wchar_t *fmt,

src/parse_tree.h

@@ -140,8 +140,10 @@ class parse_node_t {
 class parse_node_tree_t : public std::vector<parse_node_t> {
    public:
     parse_node_tree_t() {}
-
+    parse_node_tree_t(parse_node_tree_t &&) = default;
-    parse_node_tree_t(moved_ref<parse_node_tree_t> t) { this->swap(t.val); }
+    parse_node_tree_t &operator=(parse_node_tree_t &&) = default;
+    parse_node_tree_t(const parse_node_tree_t &) = delete; // no copying
+    parse_node_tree_t &operator=(const parse_node_tree_t &) = delete; // no copying
 
     // Get the node corresponding to a child of the given node, or NULL if there is no such child.
     // If expected_type is provided, assert that the node has that type.

src/parser.cpp

@@ -593,15 +593,14 @@ int parser_t::eval(const wcstring &cmd, const io_chain_t &io, enum block_type_t
         fwprintf(stderr, L"%ls\n", backtrace_and_desc.c_str());
         return 1;
     }
-    return this->eval_acquiring_tree(cmd, io, block_type, moved_ref<parse_node_tree_t>(tree));
+    return this->eval(cmd, io, block_type, std::move(tree));
 }
 
-int parser_t::eval_acquiring_tree(const wcstring &cmd, const io_chain_t &io,
+int parser_t::eval(const wcstring &cmd, const io_chain_t &io, enum block_type_t block_type, parse_node_tree_t tree) {
-                                  enum block_type_t block_type, moved_ref<parse_node_tree_t> tree) {
     CHECK_BLOCK(1);
     assert(block_type == TOP || block_type == SUBST);
 
-    if (tree.val.empty()) {
+    if (tree.empty()) {
         return 0;
     }
 
@@ -613,7 +612,8 @@ int parser_t::eval_acquiring_tree(const wcstring &cmd, const io_chain_t &io,
         (execution_contexts.empty() ? -1 : execution_contexts.back()->current_eval_level());
 
     // Append to the execution context stack.
-    execution_contexts.push_back(make_unique<parse_execution_context_t>(tree, cmd, this, exec_eval_level));
+    execution_contexts.push_back(make_unique<parse_execution_context_t>(std::move(tree), cmd,
+                                                                        this, exec_eval_level));
     const parse_execution_context_t *ctx = execution_contexts.back().get();
 
     // Execute the first node.

src/parser.h

@@ -244,9 +244,7 @@ class parser_t {
     int eval(const wcstring &cmd, const io_chain_t &io, enum block_type_t block_type);
 
     /// Evaluate the expressions contained in cmd, which has been parsed into the given parse tree.
-    /// This takes ownership of the tree.
+    int eval(const wcstring &cmd, const io_chain_t &io, enum block_type_t block_type, parse_node_tree_t t);
-    int eval_acquiring_tree(const wcstring &cmd, const io_chain_t &io, enum block_type_t block_type,
-                            moved_ref<parse_node_tree_t> t);
 
     /// Evaluates a block node at the given node offset in the topmost execution context.
     int eval_block_node(node_offset_t node_idx, const io_chain_t &io, enum block_type_t block_type);

src/reader.cpp

@@ -3305,7 +3305,7 @@ static int read_ni(int fd, const io_chain_t &io) {
         parse_error_list_t errors;
         parse_node_tree_t tree;
         if (!parse_util_detect_errors(str, &errors, false /* do not accept incomplete */, &tree)) {
-            parser.eval_acquiring_tree(str, io, TOP, moved_ref<parse_node_tree_t>(tree));
+            parser.eval(str, io, TOP, std::move(tree));
         } else {
             wcstring sb;
             parser.get_backtrace(str, errors, &sb);