refactor code to prepare for multiple files

verbose compiler output is now behind --verbose flag

src/parser.cpp

@@ -100,6 +100,8 @@ const char *node_type_str(NodeType node_type) {
             return "Symbol";
         case NodeTypePrefixOpExpr:
             return "PrefixOpExpr";
+        case NodeTypeUse:
+            return "Use";
     }
     zig_unreachable();
 }
@@ -241,6 +243,9 @@ void ast_print(AstNode *node, int indent) {
             fprintf(stderr, "PrimaryExpr Symbol %s\n",
                     buf_ptr(&node->data.symbol));
             break;
+        case NodeTypeUse:
+            fprintf(stderr, "%s '%s'\n", node_type_str(node->type), buf_ptr(&node->data.use.path));
+            break;
     }
 }
 
@@ -1231,7 +1236,36 @@ static AstNode *ast_parse_root_export_decl(ParseContext *pc, int *token_index, b
 }
 
 /*
-TopLevelDecl : FnDef | ExternBlock | RootExportDecl
+Use : many(Directive) token(Use) token(String) token(Semicolon)
+*/
+static AstNode *ast_parse_use(ParseContext *pc, int *token_index, bool mandatory) {
+    assert(mandatory == false);
+
+    Token *use_kw = &pc->tokens->at(*token_index);
+    if (use_kw->id != TokenIdKeywordUse)
+        return nullptr;
+    *token_index += 1;
+
+    Token *use_name = &pc->tokens->at(*token_index);
+    *token_index += 1;
+    ast_expect_token(pc, use_name, TokenIdStringLiteral);
+
+    Token *semicolon = &pc->tokens->at(*token_index);
+    *token_index += 1;
+    ast_expect_token(pc, semicolon, TokenIdSemicolon);
+
+    AstNode *node = ast_create_node(NodeTypeUse, use_kw);
+
+    parse_string_literal(pc, use_name, &node->data.use.path);
+
+    node->data.use.directives = pc->directive_list;
+    pc->directive_list = nullptr;
+
+    return node;
+}
+
+/*
+TopLevelDecl : FnDef | ExternBlock | RootExportDecl | Use
 */
 static void ast_parse_top_level_decls(ParseContext *pc, int *token_index, ZigList<AstNode *> *top_level_decls) {
     for (;;) {
@@ -1258,6 +1292,12 @@ static void ast_parse_top_level_decls(ParseContext *pc, int *token_index, ZigLis
             continue;
         }
 
+        AstNode *use_node = ast_parse_use(pc, token_index, false);
+        if (use_node) {
+            top_level_decls->append(use_node);
+            continue;
+        }
+
         if (pc->directive_list->length > 0) {
             ast_error(directive_token, "invalid directive");
         }