Move tree visit definitions in visit.c to visit/tree.c for future consistency

Signed-off-by: Mel <mel@rnrd.eu>

1 files changed, 1185 insertions, 0 deletions

diff --git a/boot/visit/tree.c b/boot/visit/tree.c
new file mode 100644
index 0000000..001cd36
--- /dev/null
+++ b/boot/visit/tree.c
@@ -0,0 +1,1185 @@
+/*
+ * 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.
+ *
+ * Copyright (c) 2025, Mel G. <mel@rnrd.eu>
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ */
+
+#pragma once
+
+#include "../catboot.h"
+
+struct Tree_Visit
+{
+    struct Tree_Visit_Table* table;
+    void* user_data;
+};
+
+struct Tree_Visit_Table
+{
+    void (*visit_tree)(struct Tree_Visit* visitor, struct Tree* tree);
+
+    void (*visit_statement)(struct Tree_Visit* visitor, struct Tree_Statement* stmt);
+    void (*visit_statement_declaration)(struct Tree_Visit* visitor, struct Tree_Statement* stmt);
+    void (*visit_statement_conditional)(struct Tree_Visit* visitor, struct Tree_Statement* stmt);
+    void (*visit_statement_loop)(struct Tree_Visit* visitor, struct Tree_Statement* stmt);
+    void (*visit_statement_return)(struct Tree_Visit* visitor, struct Tree_Statement* stmt);
+    void (*visit_statement_break)(struct Tree_Visit* visitor, struct Tree_Statement* stmt);
+    void (*visit_statement_continue)(struct Tree_Visit* visitor, struct Tree_Statement* stmt);
+    void (*visit_statement_defer)(struct Tree_Visit* visitor, struct Tree_Statement* stmt);
+
+    void (*visit_expression)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_integer_literal)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_float_literal)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_string_literal)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_boolean_literal)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_name)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_unary_operation)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_binary_operation)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_group)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_call)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_construct)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_subscript)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_member)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_increment_decrement)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_try)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_must)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+    void (*visit_expression_function)(struct Tree_Visit* visitor, struct Tree_Expression* expr);
+
+    void (*visit_type_node)(struct Tree_Visit* visitor, struct Tree_Type* node);
+    void (*visit_type_node_name)(struct Tree_Visit* visitor, struct Tree_Type* node);
+    void (*visit_type_node_array)(struct Tree_Visit* visitor, struct Tree_Type* node);
+    void (*visit_type_node_reference)(struct Tree_Visit* visitor, struct Tree_Type* node);
+    void (*visit_type_node_maybe)(struct Tree_Visit* visitor, struct Tree_Type* node);
+    void (*visit_type_node_tuple)(struct Tree_Visit* visitor, struct Tree_Type* node);
+    void (*visit_type_node_map)(struct Tree_Visit* visitor, struct Tree_Type* node);
+    void (*visit_type_node_function)(struct Tree_Visit* visitor, struct Tree_Type* node);
+    void (*visit_type_node_structure)(struct Tree_Visit* visitor, struct Tree_Type* node);
+    void (*visit_type_node_variant)(struct Tree_Visit* visitor, struct Tree_Type* node);
+    void (*visit_type_node_class)(struct Tree_Visit* visitor, struct Tree_Type* node);
+
+    void (*visit_block_node)(struct Tree_Visit* visitor, struct Tree_Block* node);
+    void (*visit_bare_declaration_node)(struct Tree_Visit* visitor, struct Tree_Bare_Declaration* node);
+    void (*visit_function_header_node)(struct Tree_Visit* visitor, struct Tree_Function_Header* header);
+    void (*visit_argument_group_node)(struct Tree_Visit* visitor, struct Tree_Argument_Group* node);
+    void (*visit_pragma_node)(struct Tree_Visit* visitor, struct Tree_Pragma* node);
+};
+
+#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); }
+
+// tree_walk functions are the default traversal mechanism
+
+// define a tree_walk function which goes nowhere.
+#define TREE_WALK_LEAF_FUNCTION(name, type) \
+    void name(struct Tree_Visit* visit, type node) {}
+
+// top-level tree_walk function for beginning the visit flow.
+void
+tree_walk(struct Tree_Visit* visit, struct Tree* tree)
+{
+    VISIT(visit_tree, tree);
+}
+
+void
+tree_walk_tree(struct Tree_Visit* visit, struct Tree* tree)
+{
+    FOR_EACH (struct Tree_Statement*, statement, tree->top_level_statements) {
+        VISIT(visit_statement, statement);
+    }
+}
+
+void
+tree_walk_statement(struct Tree_Visit* visit, struct Tree_Statement* statement)
+{
+    switch (statement->kind) {
+    case TREE_STATEMENT_EXPRESSION:
+        VISIT(visit_expression, statement->value.expression.inner);
+        break;
+    case TREE_STATEMENT_DECLARATION:
+        VISIT(visit_statement_declaration, statement);
+        break;
+    case TREE_STATEMENT_BLOCK:
+        VISIT(visit_block_node, &statement->value.block.inner);
+        break;
+    case TREE_STATEMENT_CONDITIONAL:
+        VISIT(visit_statement_conditional, statement);
+        break;
+    case TREE_STATEMENT_LOOP:
+        VISIT(visit_statement_loop, statement);
+        break;
+    case TREE_STATEMENT_RETURN:
+        VISIT(visit_statement_return, statement);
+        break;
+    case TREE_STATEMENT_BREAK:
+        VISIT(visit_statement_break, statement);
+        break;
+    case TREE_STATEMENT_CONTINUE:
+        VISIT(visit_statement_continue, statement);
+        break;
+    case TREE_STATEMENT_DEFER:
+        VISIT(visit_statement_defer, statement);
+        break;
+    case TREE_STATEMENT_PRAGMA:
+        VISIT(visit_pragma_node, statement->value.pragma.inner);
+        break;
+    default:
+        failure("unexpected statement kind in `tree_walk_statement`");
+    }
+}
+
+void
+tree_walk_statement_declaration(struct Tree_Visit* visit, struct Tree_Statement* statement)
+{
+    VISIT(visit_bare_declaration_node, &statement->value.declaration.inner);
+}
+
+void
+tree_walk_statement_conditional(struct Tree_Visit* visit, struct Tree_Statement* statement)
+{
+    struct Tree_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
+tree_walk_statement_loop(struct Tree_Visit* visit, struct Tree_Statement* statement)
+{
+    struct Tree_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
+tree_walk_statement_return(struct Tree_Visit* visit, struct Tree_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.
+TREE_WALK_LEAF_FUNCTION(tree_walk_statement_break, struct Tree_Statement*);
+
+TREE_WALK_LEAF_FUNCTION(tree_walk_statement_continue, struct Tree_Statement*);
+
+void
+tree_walk_statement_defer(struct Tree_Visit* visit, struct Tree_Statement* statement)
+{
+    VISIT_MAYBE(visit_expression, statement->value.defer.expression);
+    VISIT(visit_block_node, &statement->value.defer.block);
+}
+
+void
+tree_walk_expression(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    switch (expression->kind) {
+    case TREE_EXPRESSION_INTEGER_LITERAL:
+        VISIT(visit_expression_integer_literal, expression);
+        break;
+    case TREE_EXPRESSION_FLOAT_LITERAL:
+        VISIT(visit_expression_float_literal, expression);
+        break;
+    case TREE_EXPRESSION_STRING_LITERAL:
+        VISIT(visit_expression_string_literal, expression);
+        break;
+    case TREE_EXPRESSION_BOOLEAN_LITERAL:
+        VISIT(visit_expression_boolean_literal, expression);
+        break;
+    case TREE_EXPRESSION_NAME:
+        VISIT(visit_expression_name, expression);
+        break;
+    case TREE_EXPRESSION_UNARY_OPERATION:
+        VISIT(visit_expression_unary_operation, expression);
+        break;
+    case TREE_EXPRESSION_BINARY_OPERATION:
+        VISIT(visit_expression_binary_operation, expression);
+        break;
+    case TREE_EXPRESSION_GROUP:
+        VISIT(visit_expression_group, expression);
+        break;
+    case TREE_EXPRESSION_CALL:
+        VISIT(visit_expression_call, expression);
+        break;
+    case TREE_EXPRESSION_CONSTRUCT:
+        VISIT(visit_expression_construct, expression);
+        break;
+    case TREE_EXPRESSION_SUBSCRIPT:
+        VISIT(visit_expression_subscript, expression);
+        break;
+    case TREE_EXPRESSION_MEMBER:
+        VISIT(visit_expression_member, expression);
+        break;
+    case TREE_EXPRESSION_INCREMENT_DECREMENT:
+        VISIT(visit_expression_increment_decrement, expression);
+        break;
+    case TREE_EXPRESSION_TRY:
+        VISIT(visit_expression_try, expression);
+        break;
+    case TREE_EXPRESSION_MUST:
+        VISIT(visit_expression_must, expression);
+        break;
+    case TREE_EXPRESSION_FUNCTION:
+        VISIT(visit_expression_function, expression);
+        break;
+    case TREE_EXPRESSION_TYPE:
+        VISIT(visit_type_node, expression->value.type.type);
+        break;
+    default:
+        failure("unexpected expression kind in `tree_walk_expression`");
+    }
+}
+
+TREE_WALK_LEAF_FUNCTION(tree_walk_expression_integer_literal, struct Tree_Expression*);
+
+TREE_WALK_LEAF_FUNCTION(tree_walk_expression_float_literal, struct Tree_Expression*);
+
+TREE_WALK_LEAF_FUNCTION(tree_walk_expression_string_literal, struct Tree_Expression*);
+
+TREE_WALK_LEAF_FUNCTION(tree_walk_expression_boolean_literal, struct Tree_Expression*);
+
+TREE_WALK_LEAF_FUNCTION(tree_walk_expression_name, struct Tree_Expression*);
+
+void
+tree_walk_expression_unary_operation(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    VISIT(visit_expression, expression->value.unary_operator.operand);
+}
+
+void
+tree_walk_expression_binary_operation(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    VISIT(visit_expression, expression->value.binary_operator.left_operand);
+    VISIT(visit_expression, expression->value.binary_operator.right_operand);
+}
+
+void
+tree_walk_expression_group(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    VISIT(visit_expression, expression->value.group.inner_expression);
+}
+
+void
+tree_walk_expression_call(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    struct Tree_Expression_Call* call = &expression->value.call;
+    VISIT(visit_expression, call->subject);
+    VISIT(visit_argument_group_node, &call->argument_group);
+}
+
+void
+tree_walk_expression_construct(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    struct Tree_Expression_Construct* construct = &expression->value.construct;
+    VISIT(visit_expression, construct->subject);
+    VISIT(visit_argument_group_node, &construct->argument_group);
+}
+
+void
+tree_walk_expression_subscript(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    VISIT(visit_expression, expression->value.subscript.subject);
+    VISIT(visit_expression, expression->value.subscript.index);
+}
+
+void
+tree_walk_expression_member(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    VISIT(visit_expression, expression->value.member.subject);
+}
+
+void
+tree_walk_expression_increment_decrement(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    VISIT(visit_expression, expression->value.increment_decrement.subject);
+}
+
+TREE_WALK_LEAF_FUNCTION(tree_walk_expression_try, struct Tree_Expression*);
+
+TREE_WALK_LEAF_FUNCTION(tree_walk_expression_must, struct Tree_Expression*);
+
+void
+tree_walk_expression_function(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    VISIT(visit_function_header_node, &expression->value.function.header);
+    VISIT(visit_block_node, &expression->value.function.body);
+}
+
+void
+tree_walk_type(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    switch (node->type) {
+    case TREE_TYPE_NONE:
+        break;
+    case TREE_TYPE_NAME:
+        VISIT(visit_type_node_name, node);
+        break;
+    case TREE_TYPE_ARRAY:
+        VISIT(visit_type_node_array, node);
+        break;
+    case TREE_TYPE_REFERENCE:
+        VISIT(visit_type_node_reference, node);
+        break;
+    case TREE_TYPE_MAYBE:
+        VISIT(visit_type_node_maybe, node);
+        break;
+    case TREE_TYPE_TUPLE:
+        VISIT(visit_type_node_tuple, node);
+        break;
+    case TREE_TYPE_MAP:
+        VISIT(visit_type_node_map, node);
+        break;
+    case TREE_TYPE_FUNCTION:
+        VISIT(visit_type_node_function, node);
+        break;
+    case TREE_TYPE_STRUCTURE:
+        VISIT(visit_type_node_structure, node);
+        break;
+    case TREE_TYPE_VARIANT:
+        VISIT(visit_type_node_variant, node);
+        break;
+    case TREE_TYPE_CLASS:
+        VISIT(visit_type_node_class, node);
+        break;
+    default:
+        failure("unexpected type node kind in `tree_walk_type`");
+    }
+}
+
+TREE_WALK_LEAF_FUNCTION(tree_walk_type_name, struct Tree_Type*);
+
+void
+tree_walk_type_array(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    VISIT(visit_type_node, node->value.array.element_type);
+}
+
+void
+tree_walk_type_reference(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    VISIT(visit_type_node, node->value.reference.referenced_type);
+}
+
+void
+tree_walk_type_maybe(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    VISIT(visit_type_node, node->value.maybe.inner_type);
+}
+
+void
+tree_walk_type_tuple(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    FOR_EACH (struct Tree_Type*, current, node->value.tuple.head) {
+        VISIT(visit_type_node, current);
+    }
+}
+
+void
+tree_walk_type_map(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    VISIT(visit_type_node, node->value.map.key_type);
+    VISIT(visit_type_node, node->value.map.value_type);
+}
+
+void
+tree_walk_type_function(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    VISIT(visit_function_header_node, &node->value.function.header);
+}
+
+void
+tree_walk_type_structure(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    FOR_EACH (struct Tree_Type*, field, node->value.structure.fields) {
+        VISIT(visit_type_node, field);
+    }
+}
+
+void
+tree_walk_type_variant(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    FOR_EACH (struct Tree_Type*, method, node->value.variant.variants) {
+        VISIT(visit_type_node, method);
+    }
+}
+
+void
+tree_walk_type_class(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    FOR_EACH (struct Tree_Type*, method, node->value.class.methods) {
+        VISIT(visit_type_node, method);
+    }
+}
+
+void
+tree_walk_block(struct Tree_Visit* visit, struct Tree_Block* node)
+{
+    FOR_EACH (struct Tree_Statement*, statement, node->statements) { VISIT(visit_statement, statement); }
+}
+
+void
+tree_walk_bare_declaration(struct Tree_Visit* visit, struct Tree_Bare_Declaration* node)
+{
+    VISIT_MAYBE(visit_type_node, node->type);
+    VISIT(visit_expression, node->initializer);
+}
+
+void
+tree_walk_function_header(struct Tree_Visit* visit, struct Tree_Function_Header* header)
+{
+    FOR_EACH (struct Tree_Type*, param_type, header->parameters_type_and_name) {
+        VISIT(visit_type_node, param_type);
+    }
+    VISIT_MAYBE(visit_type_node, header->return_type);
+}
+
+void
+tree_walk_argument_group(struct Tree_Visit* visit, struct Tree_Argument_Group* node)
+{
+    FOR_EACH (struct Tree_Expression*, argument, node->arguments) { VISIT(visit_expression, argument); }
+}
+
+void
+tree_walk_pragma(struct Tree_Visit* visit, struct Tree_Pragma* node)
+{
+    // visit each pragma node in the linked list.
+    VISIT_MAYBE(visit_pragma_node, node->next);
+}
+
+struct Tree_Visit_Table tree_walk_functions = {
+    .visit_tree = tree_walk_tree,
+
+    .visit_statement = tree_walk_statement,
+    .visit_statement_declaration = tree_walk_statement_declaration,
+    .visit_statement_conditional = tree_walk_statement_conditional,
+    .visit_statement_loop = tree_walk_statement_loop,
+    .visit_statement_return = tree_walk_statement_return,
+    .visit_statement_break = tree_walk_statement_break,
+    .visit_statement_continue = tree_walk_statement_continue,
+    .visit_statement_defer = tree_walk_statement_defer,
+
+    .visit_expression = tree_walk_expression,
+    .visit_expression_integer_literal = tree_walk_expression_integer_literal,
+    .visit_expression_float_literal = tree_walk_expression_float_literal,
+    .visit_expression_string_literal = tree_walk_expression_string_literal,
+    .visit_expression_boolean_literal = tree_walk_expression_boolean_literal,
+    .visit_expression_name = tree_walk_expression_name,
+    .visit_expression_unary_operation = tree_walk_expression_unary_operation,
+    .visit_expression_binary_operation = tree_walk_expression_binary_operation,
+    .visit_expression_group = tree_walk_expression_group,
+    .visit_expression_call = tree_walk_expression_call,
+    .visit_expression_construct = tree_walk_expression_construct,
+    .visit_expression_subscript = tree_walk_expression_subscript,
+    .visit_expression_member = tree_walk_expression_member,
+    .visit_expression_increment_decrement = tree_walk_expression_increment_decrement,
+    .visit_expression_function = tree_walk_expression_function,
+
+    .visit_type_node = tree_walk_type,
+    .visit_type_node_name = tree_walk_type_name,
+    .visit_type_node_array = tree_walk_type_array,
+    .visit_type_node_reference = tree_walk_type_reference,
+    .visit_type_node_maybe = tree_walk_type_maybe,
+    .visit_type_node_tuple = tree_walk_type_tuple,
+    .visit_type_node_map = tree_walk_type_map,
+    .visit_type_node_function = tree_walk_type_function,
+    .visit_type_node_structure = tree_walk_type_structure,
+    .visit_type_node_variant = tree_walk_type_variant,
+    .visit_type_node_class = tree_walk_type_class,
+
+    .visit_block_node = tree_walk_block,
+    .visit_bare_declaration_node = tree_walk_bare_declaration,
+    .visit_function_header_node = tree_walk_function_header,
+    .visit_argument_group_node = tree_walk_argument_group,
+    .visit_pragma_node = tree_walk_pragma,
+};
+
+// fills in the visit table with default tree_walk functions
+void
+tree_visit_table_fill_defaults(struct Tree_Visit_Table* table)
+{
+    // not portable, nor safe, but sometimes you need to have a bit of fun! :3
+
+    // assumptions:
+    // - sizeof(struct Tree_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 Tree_Visit_Table to a function pointer array is undefined, but safe.
+    const uint function_count = sizeof(struct Tree_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* tree_walk = &((Function_Ptr*)&tree_walk_functions)[fi];
+        if (!*function_slot) *function_slot = *tree_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;
+    bool did_print_last_visit;
+};
+
+#define TREE_PRINTER_PREAMBLE                     \
+    DATA_FOR_VISIT(struct Tree_Printer, printer); \
+    tree_printer_reset_print_state(printer);
+
+void
+tree_printer_out(struct Tree_Printer* printer, const ascii* format, ...)
+{
+    va_list args;
+    va_start(args, format);
+    vfprintf(printer->output, format, args);
+    va_end(args);
+
+    printer->did_print_last_visit = true;
+}
+
+#define PRINT(...) tree_printer_out(printer, __VA_ARGS__)
+#define PRINT_WHITESPACE_IF_NEEDED(s)                    \
+    do {                                                 \
+        if (printer->did_print_last_visit) { PRINT(s); } \
+        tree_printer_reset_print_state(printer);         \
+    } while (0)
+
+void
+tree_printer_reset_print_state(struct Tree_Printer* printer)
+{
+    printer->did_print_last_visit = false;
+}
+
+void
+tree_printer_indent(struct Tree_Printer* printer)
+{
+    for (uint i = 0; i < printer->indentation_level; ++i) PRINT("\t");
+}
+
+void
+tree_printer_visit_tree(struct Tree_Visit* visit, struct Tree* tree)
+{
+    TREE_PRINTER_PREAMBLE
+
+    FOR_EACH (struct Tree_Statement*, statement, tree->top_level_statements) {
+        VISIT(visit_statement, statement);
+        PRINT("\n");
+    }
+}
+
+void
+tree_printer_visit_statement(struct Tree_Visit* visit, struct Tree_Statement* statement)
+{
+    TREE_PRINTER_PREAMBLE
+
+    tree_printer_indent(printer);
+    tree_walk_statement(visit, statement);
+}
+
+void
+tree_printer_visit_statement_declaration(struct Tree_Visit* visit, struct Tree_Statement* stmt)
+{
+    TREE_PRINTER_PREAMBLE
+
+    if (stmt->value.declaration.kind == TREE_STATEMENT_DECLARATION_VARIABLE)
+        PRINT("(variable ");
+    else if (stmt->value.declaration.kind == TREE_STATEMENT_DECLARATION_CONSTANT)
+        PRINT("(constant ");
+
+    VISIT(visit_bare_declaration_node, &stmt->value.declaration.inner);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_statement_conditional(struct Tree_Visit* visit, struct Tree_Statement* stmt)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(conditional");
+    for (uint i = 0; i < stmt->value.conditional.condition_count; ++i) {
+        const struct Tree_Statement_Conditional_Branch* branch = &stmt->value.conditional.conditions[i];
+        PRINT(" ");
+        if (branch->when) {
+            PRINT("(when ");
+            VISIT(visit_expression, branch->when);
+            PRINT(") ");
+        } else {
+            PRINT("(always) ");
+        }
+        VISIT(visit_block_node, (struct Tree_Block*)&branch->then);
+    }
+    PRINT(")");
+}
+
+void
+tree_printer_visit_statement_loop(struct Tree_Visit* visit, struct Tree_Statement* stmt)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(loop ");
+
+    switch (stmt->value.loop.style) {
+    case TREE_STATEMENT_LOOP_STYLE_C:
+        PRINT("c-style ");
+        VISIT(visit_bare_declaration_node, &stmt->value.loop.declaration);
+        PRINT(" (condition ");
+        VISIT(visit_expression, stmt->value.loop.condition);
+        PRINT(") (iteration ");
+        VISIT(visit_expression, stmt->value.loop.iteration);
+        PRINT(") ");
+        break;
+    case TREE_STATEMENT_LOOP_STYLE_FOR_EACH:
+        PRINT("for-each ");
+        VISIT(visit_bare_declaration_node, &stmt->value.loop.declaration);
+        PRINT(" ");
+        break;
+    case TREE_STATEMENT_LOOP_STYLE_WHILE:
+        PRINT("while (condition ");
+        VISIT(visit_expression, stmt->value.loop.condition);
+        PRINT(") ");
+        break;
+    case TREE_STATEMENT_LOOP_STYLE_ENDLESS:
+        PRINT("endless ");
+        break;
+    default:
+        fprintf(stderr, "unexpected loop style in `tree_printer_visit_statement_loop`");
+        break;
+    }
+
+    VISIT(visit_block_node, &stmt->value.loop.body);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_statement_return(struct Tree_Visit* visit, struct Tree_Statement* stmt)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(return");
+    if (stmt->value.return_value.value) {
+        PRINT(" ");
+        VISIT(visit_expression, stmt->value.return_value.value);
+    }
+    PRINT(")");
+}
+
+void
+tree_printer_visit_statement_break(struct Tree_Visit* visit, struct Tree_Statement* stmt)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(break)");
+}
+
+void
+tree_printer_visit_statement_continue(struct Tree_Visit* visit, struct Tree_Statement* stmt)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(continue)");
+}
+
+void
+tree_printer_visit_statement_defer(struct Tree_Visit* visit, struct Tree_Statement* stmt)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(defer ");
+    if (stmt->value.defer.expression) {
+        VISIT(visit_expression, stmt->value.defer.expression);
+    } else {
+        VISIT(visit_block_node, &stmt->value.defer.block);
+    }
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression(struct Tree_Visit* visit, struct Tree_Expression* expression)
+{
+    TREE_PRINTER_PREAMBLE
+    PRINT("(expr ");
+    tree_walk_expression(visit, expression);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression_integer_literal(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("%ld", expr->value.integer_literal.value);
+}
+
+void
+tree_printer_visit_expression_float_literal(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("%lf", expr->value.float_literal.value);
+}
+
+void
+tree_printer_visit_expression_string_literal(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("\"%s\"", expr->value.string_literal.value.data);
+}
+
+void
+tree_printer_visit_expression_boolean_literal(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("%s", expr->value.bool_literal.value ? "true" : "false");
+}
+
+void
+tree_printer_visit_expression_name(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(name %s)", expr->value.name.name.data);
+}
+
+void
+tree_printer_visit_expression_unary_operation(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(unary %s ", unary_operation_to_string(expr->value.unary_operator.operation));
+    VISIT(visit_expression, expr->value.unary_operator.operand);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression_binary_operation(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(binary %s ", binary_operation_to_string(expr->value.binary_operator.operation));
+    VISIT(visit_expression, expr->value.binary_operator.left_operand);
+    PRINT(" ");
+    VISIT(visit_expression, expr->value.binary_operator.right_operand);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression_group(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(group ");
+    VISIT(visit_expression, expr->value.group.inner_expression);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression_call(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    struct Tree_Expression_Call* call = &expr->value.call;
+    PRINT("(call ");
+    VISIT(visit_expression, call->subject);
+    VISIT(visit_argument_group_node, &call->argument_group);
+
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression_construct(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    struct Tree_Expression_Construct* construct = &expr->value.construct;
+    PRINT("(construct ");
+    VISIT(visit_expression, construct->subject);
+    VISIT(visit_argument_group_node, &construct->argument_group);
+
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression_subscript(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(subscript ");
+    VISIT(visit_expression, expr->value.subscript.subject);
+    PRINT(" ");
+    VISIT(visit_expression, expr->value.subscript.index);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression_member(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(member of ");
+    VISIT(visit_expression, expr->value.member.subject);
+    PRINT(" named %s)", expr->value.member.name.data);
+}
+
+void
+tree_printer_visit_expression_increment_decrement(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    const struct Tree_Expression_Increment_Decrement* inc_dec = &expr->value.increment_decrement;
+    const ascii* prefix_or_postfix = inc_dec->prefix ? "prefix" : "postfix";
+    PRINT("(increment/decrement %s %s ",
+          increment_decrement_operation_to_string(inc_dec->operation), prefix_or_postfix);
+    VISIT(visit_expression, inc_dec->subject);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression_try(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(try ");
+    VISIT(visit_expression, expr->value.try.expression);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression_must(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(must ");
+    VISIT(visit_expression, expr->value.must.expression);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_expression_function(struct Tree_Visit* visit, struct Tree_Expression* expr)
+{
+    TREE_PRINTER_PREAMBLE
+
+    struct Tree_Expression_Function* fun = &expr->value.function;
+    PRINT("(function ");
+    VISIT(visit_function_header_node, &fun->header);
+    PRINT_WHITESPACE_IF_NEEDED(" ");
+    VISIT(visit_block_node, (struct Tree_Block*)&fun->body);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_type(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+    PRINT("(type ");
+    if (node->variadic) PRINT("variadic ");
+    tree_walk_type(visit, node);
+    PRINT(")");
+}
+
+void
+tree_printer_visit_type_name(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("name %s", node->value.name.name.data);
+}
+
+void
+tree_printer_visit_type_array(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("array of ");
+    VISIT(visit_type_node, node->value.array.element_type);
+}
+
+void
+tree_printer_visit_type_reference(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("reference to ");
+    VISIT(visit_type_node, node->value.reference.referenced_type);
+}
+
+void
+tree_printer_visit_type_maybe(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("maybe ");
+    VISIT(visit_type_node, node->value.maybe.inner_type);
+}
+
+void
+tree_printer_visit_type_tuple(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("tuple");
+    FOR_EACH (struct Tree_Type*, current, node->value.tuple.head) {
+        PRINT(" ");
+        VISIT(visit_type_node, current);
+    }
+}
+
+void
+tree_printer_visit_type_map(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("map ");
+    VISIT(visit_type_node, node->value.map.key_type);
+    PRINT(" = ");
+    VISIT(visit_type_node, node->value.map.value_type);
+}
+
+void
+tree_printer_visit_type_function(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("function ");
+    VISIT(visit_function_header_node, &node->value.function.header);
+}
+
+void
+tree_printer_visit_type_structure(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("structure");
+    FOR_EACH (struct Tree_Type*, current, node->value.structure.fields) {
+        PRINT(" (field %s) ", current->value_name.data);
+        VISIT(visit_type_node, current);
+    }
+}
+
+void
+tree_printer_visit_type_variant(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("variant");
+    FOR_EACH (struct Tree_Type*, current, node->value.variant.variants) {
+        if (current->type == TREE_TYPE_NONE) {
+            PRINT(" (variant %s)", current->value_name.data);
+        } else {
+            PRINT(" (variant %s of ", current->value_name.data);
+            VISIT(visit_type_node, current);
+            PRINT(")");
+        }
+    }
+}
+
+void
+tree_printer_visit_type_class(struct Tree_Visit* visit, struct Tree_Type* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("class");
+    FOR_EACH (struct Tree_Type*, current, node->value.class.methods) {
+        PRINT(" (method %s ", current->value_name.data);
+        VISIT(visit_function_header_node, &current->value.function.header);
+        PRINT(")");
+    }
+}
+
+void
+tree_printer_visit_block(struct Tree_Visit* visit, struct Tree_Block* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(block");
+    if (node->statements) {
+        PRINT("\n");
+        printer->indentation_level++;
+        FOR_EACH (struct Tree_Statement*, statement, node->statements) {
+            VISIT(visit_statement, statement);
+            PRINT("\n");
+        }
+        printer->indentation_level--;
+        tree_printer_indent(printer);
+    }
+    PRINT(")");
+}
+
+void
+tree_printer_visit_bare_declaration(struct Tree_Visit* visit, struct Tree_Bare_Declaration* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    PRINT("(declaration ");
+    FOR_EACH_ARRAY(struct String, name, &node->names, {
+        PRINT("%s ", name.data);
+    })
+
+    if (node->type && node->type->type != TREE_TYPE_NONE) {
+        VISIT(visit_type_node, node->type);
+        PRINT(" ");
+    }
+
+    if (node->initializer) {
+        PRINT("(initializer ");
+        VISIT(visit_expression, node->initializer);
+        PRINT(")");
+    }
+    PRINT(")");
+}
+
+void
+printer_visit_function_header(struct Tree_Visit* visit, struct Tree_Function_Header* header)
+{
+    TREE_PRINTER_PREAMBLE
+
+    FOR_EACH (struct Tree_Type*, current, header->parameters_type_and_name) {
+        // if (current != header->parameters_type_and_name) PRINT(" ");
+        PRINT_WHITESPACE_IF_NEEDED(" ");
+
+        if (current->value_name.data && current->value_name.data[0] != '\0')
+            PRINT("(param %s) ", current->value_name.data);
+        else
+            PRINT("(param) ");
+
+        VISIT(visit_type_node, current);
+    }
+
+    PRINT_WHITESPACE_IF_NEEDED(" ");
+
+    if (header->return_type) {
+        PRINT("(returns ");
+        VISIT(visit_type_node, header->return_type);
+        PRINT(")");
+    }
+}
+
+void
+tree_printer_visit_pragma(struct Tree_Visit* visit, struct Tree_Pragma* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    const ascii* pragma_name = tree_pragma_type_to_string(node->type);
+
+    PRINT("(pragma %s", pragma_name);
+    for (uint ai = 0; ai < node->argument_count; ++ai) {
+        struct Tree_Pragma_Argument* arg = &node->arguments[ai];
+        switch (arg->type) {
+        case TREE_PRAGMA_ARGUMENT_NUMBER:
+            PRINT(" (number %ld)", arg->value.number);
+            break;
+        case TREE_PRAGMA_ARGUMENT_DECIMAL:
+            PRINT(" (decimal %lf)", arg->value.decimal);
+            break;
+        case TREE_PRAGMA_ARGUMENT_NAME_OR_STRING:
+            PRINT(" (name/string '%s')", arg->value.name_or_string.data);
+            break;
+        default:
+            failure("unexpected pragma argument type in `tree_printer_visit_pragma`");
+        }
+    }
+    PRINT(")");
+
+    if (node->next) {
+        PRINT(" ");
+        VISIT(visit_pragma_node, node->next);
+    }
+}
+
+void
+tree_printer_visit_argument_group(struct Tree_Visit* visit, struct Tree_Argument_Group* node)
+{
+    TREE_PRINTER_PREAMBLE
+
+    uint i = 0;
+    FOR_EACH (struct Tree_Expression*, argument, node->arguments) {
+        struct String name = *array_at(struct String, &node->argument_names, i++);
+        if (name.data && name.data[0] != '\0') {
+            PRINT(" (named arg '%s' ", name.data);
+        } else {
+            PRINT(" (arg ");
+        }
+        VISIT(visit_expression, argument);
+        PRINT(")");
+    }
+}
+
+struct Tree_Visit_Table tree_printer_visit_functions = {
+    .visit_tree = tree_printer_visit_tree,
+
+    .visit_statement = tree_printer_visit_statement,
+    .visit_statement_declaration = tree_printer_visit_statement_declaration,
+    .visit_statement_conditional = tree_printer_visit_statement_conditional,
+    .visit_statement_loop = tree_printer_visit_statement_loop,
+    .visit_statement_return = tree_printer_visit_statement_return,
+    .visit_statement_break = tree_printer_visit_statement_break,
+    .visit_statement_continue = tree_printer_visit_statement_continue,
+    .visit_statement_defer = tree_printer_visit_statement_defer,
+
+    .visit_expression = tree_printer_visit_expression,
+    .visit_expression_integer_literal = tree_printer_visit_expression_integer_literal,
+    .visit_expression_float_literal = tree_printer_visit_expression_float_literal,
+    .visit_expression_string_literal = tree_printer_visit_expression_string_literal,
+    .visit_expression_boolean_literal = tree_printer_visit_expression_boolean_literal,
+    .visit_expression_name = tree_printer_visit_expression_name,
+    .visit_expression_unary_operation = tree_printer_visit_expression_unary_operation,
+    .visit_expression_binary_operation = tree_printer_visit_expression_binary_operation,
+    .visit_expression_group = tree_printer_visit_expression_group,
+    .visit_expression_call = tree_printer_visit_expression_call,
+    .visit_expression_construct = tree_printer_visit_expression_construct,
+    .visit_expression_subscript = tree_printer_visit_expression_subscript,
+    .visit_expression_member = tree_printer_visit_expression_member,
+    .visit_expression_increment_decrement = tree_printer_visit_expression_increment_decrement,
+    .visit_expression_try = tree_printer_visit_expression_try,
+    .visit_expression_must = tree_printer_visit_expression_must,
+    .visit_expression_function = tree_printer_visit_expression_function,
+
+    .visit_type_node = tree_printer_visit_type,
+    .visit_type_node_name = tree_printer_visit_type_name,
+    .visit_type_node_array = tree_printer_visit_type_array,
+    .visit_type_node_reference = tree_printer_visit_type_reference,
+    .visit_type_node_maybe = tree_printer_visit_type_maybe,
+    .visit_type_node_tuple = tree_printer_visit_type_tuple,
+    .visit_type_node_map = tree_printer_visit_type_map,
+    .visit_type_node_function = tree_printer_visit_type_function,
+    .visit_type_node_structure = tree_printer_visit_type_structure,
+    .visit_type_node_variant = tree_printer_visit_type_variant,
+    .visit_type_node_class = tree_printer_visit_type_class,
+
+    .visit_block_node = tree_printer_visit_block,
+    .visit_bare_declaration_node = tree_printer_visit_bare_declaration,
+    .visit_function_header_node = printer_visit_function_header,
+    .visit_argument_group_node = tree_printer_visit_argument_group,
+    .visit_pragma_node = tree_printer_visit_pragma,
+};
+
+void
+tree_printer(struct Tree* tree)
+{
+    struct Tree_Printer printer = {
+        .indentation_level = 0, .output = stdout, .did_print_last_visit = false
+    };
+    struct Tree_Visit visit = { .table = &tree_printer_visit_functions, .user_data = &printer };
+
+    tree_walk(&visit, tree);
+}
+
+#undef PRINT
+#undef PRINT_WHITESPACE_IF_NEEDED
+#undef TREE_PRINTER_PREAMBLE