path: root/boot/visit.c

/*
 * visit system for the catskill syntax tree,
 * implementing a default traversal mechanism,
 * allowing for selective operations on it.
 * includes a simple tree printer as the primary example of usage.
 */

struct Visit
{
    struct Visit_Table* table;
    void* user_data;
};

struct Visit_Table
{
    void (*visit_tree)(struct Visit* visitor, struct Tree* tree);

    void (*visit_statement)(struct Visit* visitor, struct Statement* stmt);
    void (*visit_statement_declaration)(struct Visit* visitor, struct Statement* stmt);
    void (*visit_statement_conditional)(struct Visit* visitor, struct Statement* stmt);
    void (*visit_statement_loop)(struct Visit* visitor, struct Statement* stmt);
    void (*visit_statement_return)(struct Visit* visitor, struct Statement* stmt);
    void (*visit_statement_break)(struct Visit* visitor, struct Statement* stmt);
    void (*visit_statement_continue)(struct Visit* visitor, struct Statement* stmt);
    void (*visit_statement_defer)(struct Visit* visitor, struct Statement* stmt);

    void (*visit_expression)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_integer_literal)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_float_literal)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_string_literal)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_boolean_literal)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_name)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_unary_operation)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_binary_operation)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_group)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_call_or_construct)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_subscript)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_member)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_increment_decrement)(struct Visit* visitor, struct Expression* expr);
    void (*visit_expression_function)(struct Visit* visitor, struct Expression* expr);

    void (*visit_type_node)(struct Visit* visitor, struct Type_Node* node);
    void (*visit_type_node_name)(struct Visit* visitor, struct Type_Node* node);
    void (*visit_type_node_array)(struct Visit* visitor, struct Type_Node* node);
    void (*visit_type_node_reference)(struct Visit* visitor, struct Type_Node* node);
    void (*visit_type_node_maybe)(struct Visit* visitor, struct Type_Node* node);
    void (*visit_type_node_tuple)(struct Visit* visitor, struct Type_Node* node);
    void (*visit_type_node_map)(struct Visit* visitor, struct Type_Node* node);
    void (*visit_type_node_function)(struct Visit* visitor, struct Type_Node* node);
    void (*visit_type_node_structure)(struct Visit* visitor, struct Type_Node* node);
    void (*visit_type_node_variant)(struct Visit* visitor, struct Type_Node* node);
    void (*visit_type_node_class)(struct Visit* visitor, struct Type_Node* node);

    void (*visit_block_node)(struct Visit* visitor, struct Block_Node* node);
    void (*visit_bare_declaration_node)(struct Visit* visitor, struct Bare_Declaration_Node* node);
    void (*visit_function_header_node)(struct Visit* visitor, struct Function_Header_Node* header);
};

#define VISIT(visit_function, node) visit->table->visit_function(visit, node);

#define VISIT_MAYBE(visit_function, node) \
    if (node) visit->table->visit_function(visit, node)

#define DATA_FOR_VISIT(type, name)        \
    type* name = (type*)visit->user_data; \
    if (!name) { failure("visit user data is NULL for " #name); }

// walk functions are the default traversal mechanism

// define a walk function which goes nowhere.
#define WALK_LEAF_FUNCTION(name, type) \
    void name(struct Visit* visit, type node) {}

// top-level walk function for beginning the visit flow.
void
walk(struct Visit* visit, struct Tree* tree)
{
    VISIT(visit_tree, tree);
}

void
walk_tree(struct Visit* visit, struct Tree* tree)
{
    FOR_EACH (struct Statement*, statement, tree->top_level_statements) {
        VISIT(visit_statement, statement);
    }
}

void
walk_statement(struct Visit* visit, struct Statement* statement)
{
    switch (statement->kind) {
    case STATEMENT_EXPRESSION:
        VISIT(visit_expression, statement->value.expression.inner);
        break;
    case STATEMENT_DECLARATION:
        VISIT(visit_statement_declaration, statement);
        break;
    case STATEMENT_BLOCK:
        VISIT(visit_block_node, &statement->value.block.inner);
        break;
    case STATEMENT_CONDITIONAL:
        VISIT(visit_statement_conditional, statement);
        break;
    case STATEMENT_LOOP:
        VISIT(visit_statement_loop, statement);
        break;
    case STATEMENT_RETURN:
        VISIT(visit_statement_return, statement);
        break;
    case STATEMENT_BREAK:
        VISIT(visit_statement_break, statement);
        break;
    case STATEMENT_CONTINUE:
        VISIT(visit_statement_continue, statement);
        break;
    case STATEMENT_DEFER:
        VISIT(visit_statement_defer, statement);
        break;
    default:
        failure("unexpected statement kind in `walk_statement`");
    }
}

void
walk_statement_declaration(struct Visit* visit, struct Statement* statement)
{
    VISIT(visit_bare_declaration_node, &statement->value.declaration.inner);
}

void
walk_statement_conditional(struct Visit* visit, struct Statement* statement)
{
    struct Statement_Value_Conditional* conditional = &statement->value.conditional;
    for (uint i = 0; i < conditional->condition_count; ++i) {
        VISIT_MAYBE(visit_expression, conditional->conditions[i].when);
        VISIT(visit_block_node, &conditional->conditions[i].then);
    }
}

void
walk_statement_loop(struct Visit* visit, struct Statement* statement)
{
    struct Statement_Value_Loop* loop = &statement->value.loop;
    VISIT_MAYBE(visit_expression, loop->condition);
    VISIT_MAYBE(visit_expression, loop->iteration);
    VISIT(visit_block_node, &loop->body);
}

void
walk_statement_return(struct Visit* visit, struct Statement* statement)
{
    VISIT_MAYBE(visit_expression, statement->value.return_value.value);
}

// although.. maybe with `break` we could make a loop become an expression,
// this returning the break value as the value of the loop?
// something to think about.
WALK_LEAF_FUNCTION(walk_statement_break, struct Statement*);

WALK_LEAF_FUNCTION(walk_statement_continue, struct Statement*);

void
walk_statement_defer(struct Visit* visit, struct Statement* statement)
{
    VISIT_MAYBE(visit_expression, statement->value.defer.expression);
    VISIT(visit_block_node, &statement->value.defer.block);
}

void
walk_expression(struct Visit* visit, struct Expression* expression)
{
    switch (expression->kind) {
    case EXPRESSION_INTEGER_LITERAL:
        VISIT(visit_expression_integer_literal, expression);
        break;
    case EXPRESSION_FLOAT_LITERAL:
        VISIT(visit_expression_float_literal, expression);
        break;
    case EXPRESSION_STRING_LITERAL:
        VISIT(visit_expression_string_literal, expression);
        break;
    case EXPRESSION_BOOLEAN_LITERAL:
        VISIT(visit_expression_boolean_literal, expression);
        break;
    case EXPRESSION_NAME:
        VISIT(visit_expression_name, expression);
        break;
    case EXPRESSION_UNARY_OPERATION:
        VISIT(visit_expression_unary_operation, expression);
        break;
    case EXPRESSION_BINARY_OPERATION:
        VISIT(visit_expression_binary_operation, expression);
        break;
    case EXPRESSION_GROUP:
        VISIT(visit_expression_group, expression);
        break;
    case EXPRESSION_CALL_OR_CONSTRUCT:
        VISIT(visit_expression_call_or_construct, expression);
        break;
    case EXPRESSION_SUBSCRIPT:
        VISIT(visit_expression_subscript, expression);
        break;
    case EXPRESSION_MEMBER:
        VISIT(visit_expression_member, expression);
        break;
    case EXPRESSION_INCREMENT_DECREMENT:
        VISIT(visit_expression_increment_decrement, expression);
        break;
    case EXPRESSION_FUNCTION:
        VISIT(visit_expression_function, expression);
        break;
    case EXPRESSION_TYPE:
        VISIT(visit_type_node, expression->value.type.type);
        break;
    default:
        failure("unexpected expression kind in `walk_expression`");
    }
}

WALK_LEAF_FUNCTION(walk_expression_integer_literal, struct Expression*);

WALK_LEAF_FUNCTION(walk_expression_float_literal, struct Expression*);

WALK_LEAF_FUNCTION(walk_expression_string_literal, struct Expression*);

WALK_LEAF_FUNCTION(walk_expression_boolean_literal, struct Expression*);

WALK_LEAF_FUNCTION(walk_expression_name, struct Expression*);

void
walk_expression_unary_operation(struct Visit* visit, struct Expression* expression)
{
    VISIT(visit_expression, expression->value.unary_operator.operand);
}

void
walk_expression_binary_operation(struct Visit* visit, struct Expression* expression)
{
    VISIT(visit_expression, expression->value.binary_operator.left_operand);
    VISIT(visit_expression, expression->value.binary_operator.right_operand);
}

void
walk_expression_group(struct Visit* visit, struct Expression* expression)
{
    VISIT(visit_expression, expression->value.group.inner_expression);
}

void
walk_expression_call_or_construct(struct Visit* visit, struct Expression* expression)
{
    struct Expression_Call_Or_Construct* coc = &expression->value.call_or_construct;
    VISIT(visit_expression, coc->subject);
    FOR_EACH (struct Expression*, argument, coc->arguments) { VISIT(visit_expression, argument); }
}

void
walk_expression_subscript(struct Visit* visit, struct Expression* expression)
{
    VISIT(visit_expression, expression->value.subscript.subject);
    VISIT(visit_expression, expression->value.subscript.index);
}

void
walk_expression_member(struct Visit* visit, struct Expression* expression)
{
    VISIT(visit_expression, expression->value.member.subject);
}

void
walk_expression_increment_decrement(struct Visit* visit, struct Expression* expression)
{
    VISIT(visit_expression, expression->value.increment_decrement.subject);
}

void
walk_expression_function(struct Visit* visit, struct Expression* expression)
{
    VISIT(visit_function_header_node, &expression->value.function.header);
    VISIT(visit_block_node, &expression->value.function.body);
}

void
walk_type_node(struct Visit* visit, struct Type_Node* node)
{
    switch (node->type) {
    case TYPE_NODE_NONE:
        break;
    case TYPE_NODE_NAME:
        VISIT(visit_type_node_name, node);
        break;
    case TYPE_NODE_ARRAY:
        VISIT(visit_type_node_array, node);
        break;
    case TYPE_NODE_REFERENCE:
        VISIT(visit_type_node_reference, node);
        break;
    case TYPE_NODE_MAYBE:
        VISIT(visit_type_node_maybe, node);
        break;
    case TYPE_NODE_TUPLE:
        VISIT(visit_type_node_tuple, node);
        break;
    case TYPE_NODE_MAP:
        VISIT(visit_type_node_map, node);
        break;
    case TYPE_NODE_FUNCTION:
        VISIT(visit_type_node_function, node);
        break;
    case TYPE_NODE_STRUCTURE:
        VISIT(visit_type_node_structure, node);
        break;
    case TYPE_NODE_VARIANT:
        VISIT(visit_type_node_variant, node);
        break;
    case TYPE_NODE_CLASS:
        VISIT(visit_type_node_class, node);
        break;
    default:
        failure("unexpected type node kind in `walk_type_node`");
    }
}

WALK_LEAF_FUNCTION(walk_type_node_name, struct Type_Node*);

void
walk_type_node_array(struct Visit* visit, struct Type_Node* node)
{
    VISIT(visit_type_node, node->value.array.element_type);
}

void
walk_type_node_reference(struct Visit* visit, struct Type_Node* node)
{
    VISIT(visit_type_node, node->value.reference.referenced_type);
}

void
walk_type_node_maybe(struct Visit* visit, struct Type_Node* node)
{
    VISIT(visit_type_node, node->value.maybe.inner_type);
}

void
walk_type_node_tuple(struct Visit* visit, struct Type_Node* node)
{
    FOR_EACH (struct Type_Node*, current, node->value.tuple.head) {
        VISIT(visit_type_node, current);
    }
}

void
walk_type_node_map(struct Visit* visit, struct Type_Node* node)
{
    VISIT(visit_type_node, node->value.map.key_type);
    VISIT(visit_type_node, node->value.map.value_type);
}

void
walk_type_node_function(struct Visit* visit, struct Type_Node* node)
{
    VISIT(visit_function_header_node, &node->value.function.header);
}

void
walk_type_node_structure(struct Visit* visit, struct Type_Node* node)
{
    FOR_EACH (struct Type_Node*, field, node->value.structure.fields) {
        VISIT(visit_type_node, field);
    }
}

void
walk_type_node_variant(struct Visit* visit, struct Type_Node* node)
{
    FOR_EACH (struct Type_Node*, method, node->value.variant.variants) {
        VISIT(visit_type_node, method);
    }
}

void
walk_type_node_class(struct Visit* visit, struct Type_Node* node)
{
    FOR_EACH (struct Type_Node*, method, node->value.class.methods) {
        VISIT(visit_type_node, method);
    }
}

void
walk_block_node(struct Visit* visit, struct Block_Node* node)
{
    FOR_EACH (struct Statement*, statement, node->statements) { VISIT(visit_statement, statement); }
}

void
walk_bare_declaration_node(struct Visit* visit, struct Bare_Declaration_Node* node)
{
    VISIT_MAYBE(visit_type_node, node->type);
    VISIT(visit_expression, node->initializer);
}

void
walk_function_header_node(struct Visit* visit, struct Function_Header_Node* header)
{
    FOR_EACH (struct Type_Node*, param_type, header->parameters_type_and_name) {
        VISIT(visit_type_node, param_type);
    }
    VISIT_MAYBE(visit_type_node, header->return_type);
}

struct Visit_Table walk_functions = {
    .visit_tree = walk_tree,

    .visit_statement = walk_statement,
    .visit_statement_declaration = walk_statement_declaration,
    .visit_statement_conditional = walk_statement_conditional,
    .visit_statement_loop = walk_statement_loop,
    .visit_statement_return = walk_statement_return,
    .visit_statement_break = walk_statement_break,
    .visit_statement_continue = walk_statement_continue,
    .visit_statement_defer = walk_statement_defer,

    .visit_expression = walk_expression,
    .visit_expression_integer_literal = walk_expression_integer_literal,
    .visit_expression_float_literal = walk_expression_float_literal,
    .visit_expression_string_literal = walk_expression_string_literal,
    .visit_expression_boolean_literal = walk_expression_boolean_literal,
    .visit_expression_name = walk_expression_name,
    .visit_expression_unary_operation = walk_expression_unary_operation,
    .visit_expression_binary_operation = walk_expression_binary_operation,
    .visit_expression_group = walk_expression_group,
    .visit_expression_call_or_construct = walk_expression_call_or_construct,
    .visit_expression_subscript = walk_expression_subscript,
    .visit_expression_member = walk_expression_member,
    .visit_expression_increment_decrement = walk_expression_increment_decrement,
    .visit_expression_function = walk_expression_function,

    .visit_type_node = walk_type_node,
    .visit_type_node_name = walk_type_node_name,
    .visit_type_node_array = walk_type_node_array,
    .visit_type_node_reference = walk_type_node_reference,
    .visit_type_node_maybe = walk_type_node_maybe,
    .visit_type_node_tuple = walk_type_node_tuple,
    .visit_type_node_map = walk_type_node_map,
    .visit_type_node_function = walk_type_node_function,
    .visit_type_node_structure = walk_type_node_structure,
    .visit_type_node_variant = walk_type_node_variant,
    .visit_type_node_class = walk_type_node_class,

    .visit_block_node = walk_block_node,
    .visit_bare_declaration_node = walk_bare_declaration_node,
    .visit_function_header_node = walk_function_header_node,
};

// fills in the visit table with default walk functions
void
visit_table_fill_defaults(struct Visit_Table* table)
{
    // not portable, nor safe, but sometimes you need to have a bit of fun! :3

    // assumptions:
    // - sizeof(struct Visit_Table) is a multiple of the size of a function pointer,
    //   with no padding between function pointers.
    // - the size of a function pointer is the same across all platforms we care about.
    // - casting struct Visit_Table to a function pointer array is undefined, but safe.
    const uint function_count = sizeof(struct Visit_Table) / sizeof(void (*)());
    typedef void (*Function_Ptr)();

    for (uint fi = 0; fi < function_count; ++fi) {
        Function_Ptr* function_slot = &((Function_Ptr*)table)[fi];
        Function_Ptr* walk = &((Function_Ptr*)&walk_functions)[fi];
        if (!*function_slot) *function_slot = *walk;
    }
}

// the most rudimentary usage of the visit system is a simple tree printer.
// prints the tree in a simple, human-readable format that resembles Lisp syntax,
// to a file or stdout (by default).
struct Tree_Printer
{
    uint indentation_level;
    FILE* output;
};

void
tree_printer_indent(struct Tree_Printer* printer)
{
    for (uint i = 0; i < printer->indentation_level; ++i) fprintf(printer->output, "\t");
}

void
printer_visit_tree(struct Visit* visit, struct Tree* tree)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);
    FOR_EACH (struct Statement*, statement, tree->top_level_statements) {
        VISIT(visit_statement, statement);
        fprintf(printer->output, "\n");
    }
}

void
printer_visit_statement(struct Visit* visit, struct Statement* statement)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);
    tree_printer_indent(printer);
    walk_statement(visit, statement);
}

void
printer_visit_statement_declaration(struct Visit* visit, struct Statement* stmt)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    if (stmt->value.declaration.kind == STATEMENT_DECLARATION_VARIABLE)
        fprintf(printer->output, "(variable ");
    else if (stmt->value.declaration.kind == STATEMENT_DECLARATION_CONSTANT)
        fprintf(printer->output, "(constant ");

    VISIT(visit_bare_declaration_node, &stmt->value.declaration.inner);
    fprintf(printer->output, ")");
}

void
printer_visit_statement_conditional(struct Visit* visit, struct Statement* stmt)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(conditional");
    for (uint i = 0; i < stmt->value.conditional.condition_count; ++i) {
        const struct Statement_Conditional_Branch* branch = &stmt->value.conditional.conditions[i];
        fprintf(printer->output, " ");
        if (branch->when) {
            fprintf(printer->output, "(when ");
            VISIT(visit_expression, branch->when);
            fprintf(printer->output, ") ");
        } else {
            fprintf(printer->output, "(always) ");
        }
        VISIT(visit_block_node, (struct Block_Node*)&branch->then);
    }
    fprintf(printer->output, ")");
}

void
printer_visit_statement_loop(struct Visit* visit, struct Statement* stmt)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(loop ");

    switch (stmt->value.loop.style) {
    case STATEMENT_LOOP_STYLE_C:
        fprintf(printer->output, "c-style ");
        VISIT(visit_bare_declaration_node, &stmt->value.loop.declaration);
        fprintf(printer->output, " (condition ");
        VISIT(visit_expression, stmt->value.loop.condition);
        fprintf(printer->output, ") (iteration ");
        VISIT(visit_expression, stmt->value.loop.iteration);
        fprintf(printer->output, ") ");
        break;
    case STATEMENT_LOOP_STYLE_FOR_EACH:
        fprintf(printer->output, "for-each ");
        VISIT(visit_bare_declaration_node, &stmt->value.loop.declaration);
        fprintf(printer->output, " ");
        break;
    case STATEMENT_LOOP_STYLE_WHILE:
        fprintf(printer->output, "while (condition ");
        VISIT(visit_expression, stmt->value.loop.condition);
        fprintf(printer->output, ") ");
        break;
    case STATEMENT_LOOP_STYLE_ENDLESS:
        fprintf(printer->output, "endless ");
        break;
    default:
        fprintf(stderr, "unexpected loop style in `printer_visit_statement_loop`");
        break;
    }

    VISIT(visit_block_node, &stmt->value.loop.body);
    fprintf(printer->output, ")");
}

void
printer_visit_statement_return(struct Visit* visit, struct Statement* stmt)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(return");
    if (stmt->value.return_value.value) {
        fprintf(printer->output, " ");
        VISIT(visit_expression, stmt->value.return_value.value);
    }
    fprintf(printer->output, ")");
}

void
printer_visit_statement_break(struct Visit* visit, struct Statement* stmt)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(break)");
}

void
printer_visit_statement_continue(struct Visit* visit, struct Statement* stmt)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(continue)");
}

void
printer_visit_statement_defer(struct Visit* visit, struct Statement* stmt)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(defer ");
    if (stmt->value.defer.expression) {
        VISIT(visit_expression, stmt->value.defer.expression);
    } else {
        VISIT(visit_block_node, &stmt->value.defer.block);
    }
    fprintf(printer->output, ")");
}

void
printer_visit_expression(struct Visit* visit, struct Expression* expression)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);
    fprintf(printer->output, "(expr ");
    walk_expression(visit, expression);
    fprintf(printer->output, ")");
}

void
printer_visit_expression_integer_literal(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "%ld", expr->value.integer_literal.value);
}

void
printer_visit_expression_float_literal(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "%lf", expr->value.float_literal.value);
}

void
printer_visit_expression_string_literal(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "\"%s\"", expr->value.string_literal.value.data);
}

void
printer_visit_expression_boolean_literal(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "%s", expr->value.bool_literal.value ? "true" : "false");
}

void
printer_visit_expression_name(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(name %s)", expr->value.name.name.data);
}

void
printer_visit_expression_unary_operation(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(unary %s ",
            unary_operation_to_string(expr->value.unary_operator.operation));
    VISIT(visit_expression, expr->value.unary_operator.operand);
    fprintf(printer->output, ")");
}

void
printer_visit_expression_binary_operation(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(binary %s ",
            binary_operation_to_string(expr->value.binary_operator.operation));
    VISIT(visit_expression, expr->value.binary_operator.left_operand);
    fprintf(printer->output, " ");
    VISIT(visit_expression, expr->value.binary_operator.right_operand);
    fprintf(printer->output, ")");
}

void
printer_visit_expression_group(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(group ");
    VISIT(visit_expression, expr->value.group.inner_expression);
    fprintf(printer->output, ")");
}

void
printer_visit_expression_call_or_construct(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    struct Expression_Call_Or_Construct* coc = &expr->value.call_or_construct;
    fprintf(printer->output, "(call/construct ");
    VISIT(visit_expression, coc->subject);

    uint i = 0;
    FOR_EACH (struct Expression*, argument, coc->arguments) {
        struct String name = string_array_at(&coc->argument_names, i++);
        if (name.data && name.data[0] != '\0') {
            fprintf(printer->output, " (named arg '%s' ", name.data);
        } else {
            fprintf(printer->output, " (arg ");
        }
        VISIT(visit_expression, argument);
        fprintf(printer->output, ")");
    }
    fprintf(printer->output, ")");
}

void
printer_visit_expression_subscript(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(subscript ");
    VISIT(visit_expression, expr->value.subscript.subject);
    fprintf(printer->output, " ");
    VISIT(visit_expression, expr->value.subscript.index);
    fprintf(printer->output, ")");
}

void
printer_visit_expression_member(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(member of ");
    VISIT(visit_expression, expr->value.member.subject);
    fprintf(printer->output, " named %s)", expr->value.member.name.data);
}

void
printer_visit_expression_increment_decrement(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    const struct Expression_Increment_Decrement* inc_dec = &expr->value.increment_decrement;
    const ascii* prefix_or_postfix = inc_dec->prefix ? "prefix" : "postfix";
    fprintf(printer->output, "(increment/decrement %s %s ",
            increment_decrement_operation_to_string(inc_dec->operation), prefix_or_postfix);
    VISIT(visit_expression, inc_dec->subject);
    fprintf(printer->output, ")");
}

void
printer_visit_expression_function(struct Visit* visit, struct Expression* expr)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    struct Expression_Function* fun = &expr->value.function;
    fprintf(printer->output, "(function ");
    VISIT(visit_function_header_node, &fun->header);
    fprintf(printer->output, " ");
    VISIT(visit_block_node, (struct Block_Node*)&fun->body);
    fprintf(printer->output, ")");
}

void
printer_visit_type_node(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);
    fprintf(printer->output, "(type ");
    walk_type_node(visit, node);
    fprintf(printer->output, ")");
}

void
printer_visit_type_node_name(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "name %s", node->value.name.name.data);
}

void
printer_visit_type_node_array(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "array of ");
    VISIT(visit_type_node, node->value.array.element_type);
}

void
printer_visit_type_node_reference(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "reference to ");
    VISIT(visit_type_node, node->value.reference.referenced_type);
}

void
printer_visit_type_node_maybe(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "maybe ");
    VISIT(visit_type_node, node->value.maybe.inner_type);
}

void
printer_visit_type_node_tuple(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "tuple");
    FOR_EACH (struct Type_Node*, current, node->value.tuple.head) {
        fprintf(printer->output, " ");
        VISIT(visit_type_node, current);
    }
}

void
printer_visit_type_node_map(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "map ");
    VISIT(visit_type_node, node->value.map.key_type);
    fprintf(printer->output, " = ");
    VISIT(visit_type_node, node->value.map.value_type);
}

void
printer_visit_type_node_function(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "function ");
    VISIT(visit_function_header_node, &node->value.function.header);
}

void
printer_visit_type_node_structure(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "structure");
    FOR_EACH (struct Type_Node*, current, node->value.structure.fields) {
        fprintf(printer->output, " (field %s) ", current->value_name.data);
        VISIT(visit_type_node, current);
    }
}

void
printer_visit_type_node_variant(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "variant");
    FOR_EACH (struct Type_Node*, current, node->value.variant.variants) {
        if (current->type == TYPE_NODE_NONE) {
            fprintf(printer->output, " (variant %s)", current->value_name.data);
        } else {
            fprintf(printer->output, " (variant %s of ", current->value_name.data);
            VISIT(visit_type_node, current);
            fprintf(printer->output, ")");
        }
    }
}

void
printer_visit_type_node_class(struct Visit* visit, struct Type_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "class");
    FOR_EACH (struct Type_Node*, current, node->value.class.methods) {
        fprintf(printer->output, " (method %s ", current->value_name.data);
        VISIT(visit_function_header_node, &current->value.function.header);
        fprintf(printer->output, ")");
    }
}

void
printer_visit_block_node(struct Visit* visit, struct Block_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(block \n");
    printer->indentation_level++;
    FOR_EACH (struct Statement*, statement, node->statements) {
        VISIT(visit_statement, statement);
        fprintf(printer->output, "\n");
    }
    printer->indentation_level--;
    tree_printer_indent(printer);
    fprintf(printer->output, ")");
}

void
printer_visit_bare_declaration_node(struct Visit* visit, struct Bare_Declaration_Node* node)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    fprintf(printer->output, "(declaration ");
    STRING_ARRAY_FOR_EACH (i, name, node->names) { fprintf(printer->output, "%s ", name.data); }

    if (node->type && node->type->type != TYPE_NODE_NONE) {
        VISIT(visit_type_node, node->type);
        fprintf(printer->output, " ");
    }

    if (node->initializer) {
        fprintf(printer->output, "(initializer ");
        VISIT(visit_expression, node->initializer);
        fprintf(printer->output, ")");
    }
    fprintf(printer->output, ")");
}

void
printer_visit_function_header(struct Visit* visit, struct Function_Header_Node* header)
{
    DATA_FOR_VISIT(struct Tree_Printer, printer);

    FOR_EACH (struct Type_Node*, current, header->parameters_type_and_name) {
        if (current != header->parameters_type_and_name) fprintf(printer->output, " ");

        if (current->value_name.data && current->value_name.data[0] != '\0')
            fprintf(printer->output, "(param %s) ", current->value_name.data);
        else
            fprintf(printer->output, "(param) ");

        VISIT(visit_type_node, current);
    }

    if (header->return_type) {
        fprintf(printer->output, " (returns ");
        VISIT(visit_type_node, header->return_type);
        fprintf(printer->output, ")");
    }
}

struct Visit_Table printer_visit_functions = {
    .visit_tree = printer_visit_tree,

    .visit_statement = printer_visit_statement,
    .visit_statement_declaration = printer_visit_statement_declaration,
    .visit_statement_conditional = printer_visit_statement_conditional,
    .visit_statement_loop = printer_visit_statement_loop,
    .visit_statement_return = printer_visit_statement_return,
    .visit_statement_break = printer_visit_statement_break,
    .visit_statement_continue = printer_visit_statement_continue,
    .visit_statement_defer = printer_visit_statement_defer,

    .visit_expression = printer_visit_expression,
    .visit_expression_integer_literal = printer_visit_expression_integer_literal,
    .visit_expression_float_literal = printer_visit_expression_float_literal,
    .visit_expression_string_literal = printer_visit_expression_string_literal,
    .visit_expression_boolean_literal = printer_visit_expression_boolean_literal,
    .visit_expression_name = printer_visit_expression_name,
    .visit_expression_unary_operation = printer_visit_expression_unary_operation,
    .visit_expression_binary_operation = printer_visit_expression_binary_operation,
    .visit_expression_group = printer_visit_expression_group,
    .visit_expression_call_or_construct = printer_visit_expression_call_or_construct,
    .visit_expression_subscript = printer_visit_expression_subscript,
    .visit_expression_member = printer_visit_expression_member,
    .visit_expression_increment_decrement = printer_visit_expression_increment_decrement,
    .visit_expression_function = printer_visit_expression_function,

    .visit_type_node = printer_visit_type_node,
    .visit_type_node_name = printer_visit_type_node_name,
    .visit_type_node_array = printer_visit_type_node_array,
    .visit_type_node_reference = printer_visit_type_node_reference,
    .visit_type_node_maybe = printer_visit_type_node_maybe,
    .visit_type_node_tuple = printer_visit_type_node_tuple,
    .visit_type_node_map = printer_visit_type_node_map,
    .visit_type_node_function = printer_visit_type_node_function,
    .visit_type_node_structure = printer_visit_type_node_structure,
    .visit_type_node_variant = printer_visit_type_node_variant,
    .visit_type_node_class = printer_visit_type_node_class,

    .visit_block_node = printer_visit_block_node,
    .visit_bare_declaration_node = printer_visit_bare_declaration_node,
    .visit_function_header_node = printer_visit_function_header,
};

void
tree_printer(struct Tree* tree)
{
    struct Tree_Printer printer = { .indentation_level = 0, .output = stdout };
    struct Visit visit = { .table = &printer_visit_functions, .user_data = &printer };

    walk(&visit, tree);
}