parsed_source_t to hold an ast directly instead of through unique_ptr

We have untangled the dependency loop and so now parsed_source_t no longer
requires indirection.

src/parse_execution.h

@@ -164,7 +164,7 @@ class parse_execution_context_t {
     const wcstring &get_source() const { return pstree->src; }
 
     /// Return the parsed ast.
-    const ast::ast_t &ast() const { return *pstree->ast; }
+    const ast::ast_t &ast() const { return pstree->ast; }
 
     /// Start executing at the given node. Returns 0 if there was no error, 1 if there was an
     /// error.

src/parse_tree.cpp

@@ -203,7 +203,7 @@ wcstring parse_token_t::user_presentable_description() const {
 }
 
 parsed_source_t::parsed_source_t(wcstring s, ast::ast_t &&ast)
-    : src(std::move(s)), ast(make_unique<ast::ast_t>(std::move(ast))) {}
+    : src(std::move(s)), ast(std::move(ast)) {}
 
 parsed_source_t::~parsed_source_t() = default;
 

src/parse_tree.h

@@ -10,6 +10,7 @@
 #include <memory>
 #include <vector>
 
+#include "ast.h"
 #include "common.h"
 #include "maybe.h"
 #include "parse_constants.h"
@@ -62,7 +63,7 @@ class ast_t;
 /// A type wrapping up a parse tree and the original source behind it.
 struct parsed_source_t {
     wcstring src;
-    std::unique_ptr<ast::ast_t> ast;
+    ast::ast_t ast;
 
     parsed_source_t(wcstring s, ast::ast_t &&ast);
     ~parsed_source_t();

src/parser.cpp

@@ -655,7 +655,7 @@ eval_res_t parser_t::eval(const wcstring &cmd, const io_chain_t &io,
 eval_res_t parser_t::eval(const parsed_source_ref_t &ps, const io_chain_t &io,
                           const job_group_ref_t &job_group, enum block_type_t block_type) {
     assert(block_type == block_type_t::top || block_type == block_type_t::subst);
-    const auto *job_list = ps->ast->top()->as<ast::job_list_t>();
+    const auto *job_list = ps->ast.top()->as<ast::job_list_t>();
     if (!job_list->empty()) {
         // Execute the top job list.
         return this->eval_node(ps, *job_list, io, job_group, block_type);