Merge pull request 'Implement Control Flow Statements in Kym' (#37) from kym-control-flow into main

Reviewed-on: #37

debug/app.ona

@@ -1,24 +1,23 @@
 
-# Test comment.
+i = 0
 
-pos = @vec3(10, 20, 0.3)
-coord = pos.xz
+while i < 5:
+	@print("hello, world")
 
-options = {
-	.title = "Afterglow",
+	i = i + 1
+end
+
+if i > 6:
+	@print("`i` greater than `6`")
+elif i == 4:
+	@print("`i` is equal to `4`")
+else:
+	@print("i'unno")
+end
+
+return {
+	.title = "Game",
 	.width = 1280,
 	.height = 800,
 	.tick_rate = 60,
-
-	["foo"] = "bar",
-	[42] = "42",
 }
-
-options["foo"] = "rab"
-options[42] = "24"
-
-@print(options.title)
-@print(options["foo"])
-@print(options[42])
-
-return options

source/ona/kym.zig

@@ -1,4 +1,4 @@
-const Ast = @import("./kym/Ast.zig");
+const ast = @import("./kym/ast.zig");
 
 const coral = @import("coral");
 
@@ -36,6 +36,7 @@ pub const RuntimeEnv = struct {
 		};
 
 		const Opcode = union (enum) {
+			pop,
 			push_nil,
 			push_true,
 			push_false,
@@ -61,6 +62,9 @@ pub const RuntimeEnv = struct {
 			clt,
 			cge,
 			cle,
+
+			jt: u32,
+			jf: u32,
 		};
 
 		const OpcodeList = coral.list.Stack(Opcode);
@@ -69,7 +73,7 @@ pub const RuntimeEnv = struct {
 			local_identifiers_buffer: [255][]const coral.io.Byte = [_][]const coral.io.Byte{""} ** 255,
 			local_identifiers_count: u8 = 0,
 
-			fn compile_expression(self: *CompilationUnit, chunk: *Chunk, expression: Ast.Expression) RuntimeError!void {
+			fn compile_expression(self: *CompilationUnit, chunk: *Chunk, expression: ast.Expression) RuntimeError!void {
 				const number_format = coral.utf8.DecimalFormat{
 					.delimiter = "_",
 					.positive_prefix = .none,
@@ -132,9 +136,9 @@ pub const RuntimeEnv = struct {
 							.subtraction => .sub,
 							.multiplication => .mul,
 							.divsion => .div,
-							.greater_equals_comparison => .eql,
+							.greater_equals_comparison => .cge,
 							.greater_than_comparison => .cgt,
-							.equals_comparison => .cge,
+							.equals_comparison => .eql,
 							.less_than_comparison => .clt,
 							.less_equals_comparison => .cle,
 						});
@@ -200,21 +204,23 @@ pub const RuntimeEnv = struct {
 
 					.local_get => |local_get| {
 						try chunk.opcodes.push_one(.{
-							.push_local = self.resolve_local(local_get) orelse {
+							.push_local = self.resolve_local(local_get.identifier) orelse {
 								return chunk.env.raise(error.OutOfMemory, "undefined local");
 							},
 						});
 					},
 
 					.local_set => |local_set| {
-						if (self.resolve_local(local_set)) |index| {
+						try self.compile_expression(chunk, local_set.value_expression.*);
+
+						if (self.resolve_local(local_set.identifier)) |index| {
 							try chunk.opcodes.push_one(.{.local_set = index});
 						} else {
 							if (self.local_identifiers_count == self.local_identifiers_buffer.len) {
 								return chunk.env.raise(error.BadSyntax, "chunks may have a maximum of 255 locals");
 							}
 
-							self.local_identifiers_buffer[self.local_identifiers_count] = local_set;
+							self.local_identifiers_buffer[self.local_identifiers_count] = local_set.identifier;
 							self.local_identifiers_count += 1;
 						}
 					},
@@ -255,17 +261,62 @@ pub const RuntimeEnv = struct {
 				}
 			}
 
-			fn compile_statement(self: *CompilationUnit, chunk: *Chunk, statement: Ast.Statement) RuntimeError!void {
+			fn compile_statement(self: *CompilationUnit, chunk: *Chunk, statement: ast.Statement) RuntimeError!void {
 				switch (statement) {
 					.@"return" => |@"return"| {
-						if (@"return".expression) |expression| {
+						if (@"return") |expression| {
 							try self.compile_expression(chunk, expression);
 						} else {
 							try chunk.opcodes.push_one(.push_nil);
 						}
 					},
 
-					.expression => |expression| try self.compile_expression(chunk, expression),
+					.block => |block| {
+						for (block.values) |block_statement| {
+							try self.compile_statement(chunk, block_statement);
+						}
+					},
+
+					.@"while" => |@"while"| {
+						try self.compile_expression(chunk, @"while".condition_expression);
+						try chunk.opcodes.push_one(.{.jf = 0});
+
+						const origin_index = @as(u32, @intCast(chunk.opcodes.values.len - 1));
+
+						for (@"while".block_statements.values) |block_statement| {
+							try self.compile_statement(chunk, block_statement);
+						}
+
+						chunk.opcodes.values[origin_index].jf = @intCast(chunk.opcodes.values.len - 1);
+
+						try self.compile_expression(chunk, @"while".condition_expression);
+						try chunk.opcodes.push_one(.{.jt = origin_index});
+					},
+
+					.@"if" => |@"if"| {
+						try self.compile_expression(chunk, @"if".condition_expression);
+						try chunk.opcodes.push_one(.{.jf = 0});
+
+						const origin_index = @as(u32, @intCast(chunk.opcodes.values.len - 1));
+
+						for (@"if".block_statements.values) |block_statement| {
+							try self.compile_statement(chunk, block_statement);
+						}
+
+						chunk.opcodes.values[origin_index].jf = @intCast(chunk.opcodes.values.len - 1);
+
+						if (@"if".else_statement) |else_statement| {
+							try self.compile_statement(chunk, else_statement.*);
+						}
+					},
+
+					.expression => |expression| {
+						try self.compile_expression(chunk, expression);
+
+						if (expression == .invoke) {
+							try chunk.opcodes.push_one(.pop);
+						}
+					},
 				}
 			}
 
@@ -288,10 +339,10 @@ pub const RuntimeEnv = struct {
 			}
 		};
 
-		fn compile(self: *Chunk, ast: Ast) RuntimeError!void {
+		fn compile(self: *Chunk, statements: []const ast.Statement) RuntimeError!void {
 			var unit = CompilationUnit{};
 
-			for (ast.list_statements()) |statement| {
+			for (statements) |statement| {
 				try unit.compile_statement(self, statement);
 			}
 		}
@@ -322,8 +373,16 @@ pub const RuntimeEnv = struct {
 
 			defer coral.debug.assert(self.env.frames.pop() != null);
 
-			for (self.opcodes.values) |opcode| {
-				switch (opcode) {
+			var opcode_cursor = @as(u32, 0);
+
+			while (opcode_cursor < self.opcodes.values.len) : (opcode_cursor += 1) {
+				switch (self.opcodes.values[opcode_cursor]) {
+					.pop => {
+						if (try self.pop_local()) |ref| {
+							self.env.discard(ref);
+						}
+					},
+
 					.push_nil => try self.env.locals.push_one(null),
 					.push_true => try self.env.locals.push_one(try self.env.new_boolean(true)),
 					.push_false => try self.env.locals.push_one(try self.env.new_boolean(false)),
@@ -337,6 +396,10 @@ pub const RuntimeEnv = struct {
 					},
 
 					.push_local => |push_local| {
+						if (push_local >= self.env.locals.values.len) {
+							return self.env.raise(error.IllegalState, "invalid local");
+						}
+
 						if (self.env.locals.values[push_local]) |local| {
 							try self.env.locals.push_one(try self.env.acquire(local));
 						} else {
@@ -401,15 +464,11 @@ pub const RuntimeEnv = struct {
 					},
 
 					.object_get => {
-						const index = (try self.pop_local()) orelse {
-							return self.env.raise(error.TypeMismatch, "nil is not a valid index");
-						};
+						const index = try self.env.expect(try self.pop_local());
 
 						defer self.env.discard(index);
 
-						const indexable = (try self.pop_local()) orelse {
-							return self.env.raise(error.TypeMismatch, "nil is not a valid indexable");
-						};
+						const indexable = try self.env.expect(try self.pop_local());
 
 						defer self.env.discard(indexable);
 
@@ -791,6 +850,29 @@ pub const RuntimeEnv = struct {
 						}));
 					},
 
+					.jf => |jf| {
+						const condition = (try self.pop_local()) orelse {
+							opcode_cursor = jf;
+
+							continue;
+						};
+
+						self.env.discard(condition);
+
+						if (!condition.is_truthy()) {
+							opcode_cursor = jf;
+						}
+					},
+
+					.jt => |jt| {
+						const condition = (try self.pop_local()) orelse continue;
+
+						self.env.discard(condition);
+
+						if (condition.is_truthy()) {
+							opcode_cursor = jt;
+						}
+					},
 				}
 			}
 
@@ -1044,20 +1126,18 @@ pub const RuntimeEnv = struct {
 		defer self.allocator.deallocate(file_data);
 
 		const file_name = file_path.to_string() orelse "<script>";
-		var ast = Ast.make(self.allocator, file_name);
-
-		defer ast.free();
-
-		ast.parse(file_data) catch |parse_error| return switch (parse_error) {
-			error.BadSyntax => self.raise(error.BadSyntax, ast.error_message()),
-			error.OutOfMemory => error.OutOfMemory,
-		};
-
 		var chunk = try Chunk.make(self, file_name);
 
 		defer chunk.free();
 
-		try chunk.compile(ast);
+		var ast_tree = ast.Tree.make(self.allocator, file_name);
+
+		defer ast_tree.free();
+
+		try chunk.compile(ast_tree.parse(file_data) catch |parse_error| return switch (parse_error) {
+			error.BadSyntax => self.raise(error.BadSyntax, ast_tree.error_message()),
+			error.OutOfMemory => error.OutOfMemory,
+		});
 
 		return chunk.execute();
 	}
@@ -1512,6 +1592,21 @@ pub const RuntimeRef = opaque {
 			.dynamic => true,
 		};
 	}
+
+	pub fn typename(self: *const RuntimeRef) []const coral.io.Byte {
+		return switch (self.object().payload) {
+			.false => "false",
+			.true => "true",
+			.float => "float",
+			.fixed => "fixed",
+			.symbol => "symbol",
+			.vector2 => "vector2",
+			.vector3 => "vector3",
+			.syscall => "syscall",
+			.string => "string",
+			.dynamic => "dynamic",
+		};
+	}
 };
 
 pub const Syscall = fn (env: *RuntimeEnv) RuntimeError!?*RuntimeRef;

source/ona/kym/Ast.zig

@@ -1,567 +0,0 @@
-const coral = @import("coral");
-
-const tokens = @import("./tokens.zig");
-
-name: []const coral.io.Byte,
-allocator: coral.io.Allocator,
-arena: coral.arena.Stacking,
-statements: Statement.List,
-error_buffer: coral.list.ByteStack,
-tokenizer: tokens.Tokenizer,
-
-pub const Expression = union (enum) {
-	nil_literal,
-	true_literal,
-	false_literal,
-	builtin: []const coral.io.Byte,
-	number_literal: []const coral.io.Byte,
-	string_literal: []const coral.io.Byte,
-	symbol_literal: []const coral.io.Byte,
-	table_literal: TableLiteral,
-	grouped_expression: *Expression,
-	local_get: []const coral.io.Byte,
-	local_set: []const coral.io.Byte,
-
-	field_get: struct {
-		object_expression: *Expression,
-		identifier: []const coral.io.Byte,
-	},
-
-	field_set: struct {
-		object_expression: *Expression,
-		identifier: []const coral.io.Byte,
-		value_expression: *Expression,
-	},
-
-	subscript_get: struct {
-		object_expression: *Expression,
-		subscript_expression: *Expression,
-	},
-
-	subscript_set: struct {
-		object_expression: *Expression,
-		subscript_expression: *Expression,
-		value_expression: *Expression,
-	},
-
-	binary_operation: struct {
-		operator: BinaryOperator,
-		lhs_expression: *Expression,
-		rhs_expression: *Expression,
-	},
-
-	unary_operation: struct {
-		operator: UnaryOperator,
-		expression: *Expression,
-	},
-
-	invoke: struct {
-		object_expression: *Expression,
-		argument_expressions: List,
-	},
-
-	pub const BinaryOperator = enum {
-		addition,
-		subtraction,
-		multiplication,
-		divsion,
-		equals_comparison,
-		greater_than_comparison,
-		greater_equals_comparison,
-		less_than_comparison,
-		less_equals_comparison,
-
-		fn token(self: BinaryOperator) tokens.Token {
-			return switch (self) {
-				.addition => .symbol_plus,
-				.subtraction => .symbol_minus,
-				.multiplication => .symbol_asterisk,
-				.divsion => .symbol_forward_slash,
-				.equals_comparison => .symbol_double_equals,
-				.greater_than_comparison => .symbol_greater_than,
-				.greater_equals_comparison => .symbol_greater_equals,
-				.less_than_comparison => .symbol_less_than,
-				.less_equals_comparison => .symbol_less_equals,
-			};
-		}
-	};
-
-	pub const TableLiteral = coral.list.Stack(struct {
-		key_expression: Expression,
-		value_expression: Expression,
-	});
-
-	pub const List = coral.list.Stack(Expression);
-};
-
-const ExpressionParser = fn (self: *Self) ParseError!Expression;
-
-pub const ParseError = error {
-	OutOfMemory,
-	BadSyntax,
-};
-
-const Self = @This();
-
-pub const Statement = union (enum) {
-	@"return": struct {
-		expression: ?Expression,
-	},
-
-	expression: Expression,
-
-	const List = coral.list.Stack(Statement);
-};
-
-const UnaryOperator = enum {
-	boolean_negation,
-	numeric_negation,
-};
-
-fn binary_operation_parser(
-	comptime parse_next: ExpressionParser,
-	comptime operators: []const Expression.BinaryOperator) ExpressionParser {
-
-	const BinaryOperationParser = struct {
-		fn parse(self: *Self) ParseError!Expression {
-			const allocator = self.arena.as_allocator();
-			var expression = try parse_next(self);
-
-			inline for (operators) |operator| {
-				const token = comptime operator.token();
-
-				if (self.tokenizer.token == coral.io.tag_of(token)) {
-					self.tokenizer.step();
-
-					if (self.tokenizer.token == .end) {
-						return self.report("expected other half of expression after `" ++ comptime token.text() ++ "`");
-					}
-
-					expression = .{
-						.binary_operation = .{
-							.operator = operator,
-							.lhs_expression = try coral.io.allocate_one(allocator, expression),
-							.rhs_expression = try coral.io.allocate_one(allocator, try parse_next(self)),
-						},
-					};
-				}
-			}
-
-			return expression;
-		}
-	};
-
-	return BinaryOperationParser.parse;
-}
-
-pub fn error_message(self: Self) []const coral.io.Byte {
-	return self.error_buffer.values;
-}
-
-pub fn free(self: *Self) void {
-	self.arena.free();
-	self.statements.free();
-	self.error_buffer.free();
-}
-
-pub fn make(allocator: coral.io.Allocator, ast_name: []const coral.io.Byte) Self {
-	return Self{
-		.arena = coral.arena.Stacking.make(allocator, 4096),
-		.error_buffer = coral.list.ByteStack.make(allocator),
-		.statements = Statement.List.make(allocator),
-		.tokenizer = .{.source = ""},
-		.allocator = allocator,
-		.name = ast_name,
-	};
-}
-
-fn report(self: *Self, message: []const coral.io.Byte) ParseError {
-	coral.utf8.print_formatted(coral.list.stack_as_writer(&self.error_buffer), "{name}@{line}: {message}", .{
-		.name = self.name,
-		.line = self.tokenizer.lines_stepped,
-		.message = message,
-	}) catch return error.OutOfMemory;
-
-	return error.BadSyntax;
-}
-
-pub fn list_statements(self: Self) []const Statement {
-	return self.statements.values;
-}
-
-pub fn parse(self: *Self, data: []const coral.io.Byte) ParseError!void {
-	self.tokenizer = .{.source = data};
-
-	var has_returned = false;
-
-	self.tokenizer.skip_newlines();
-
-	while (true) {
-		try self.statements.push_one(parse_statement: {
-			switch (self.tokenizer.token) {
-				.end => return,
-
-				.keyword_return => {
-					if (has_returned) {
-						return self.report("multiple returns in function scope but expected only one");
-					}
-
-					self.tokenizer.step();
-
-					if (self.tokenizer.token != .end and self.tokenizer.token != .newline) {
-						break: parse_statement .{
-							.@"return" = .{
-								.expression = try self.parse_expression(),
-							},
-						};
-					}
-
-					if (self.tokenizer.token != .end and self.tokenizer.token != .newline) {
-						return self.report("expected end or newline after return statement");
-					}
-
-					has_returned = true;
-
-					break: parse_statement .{
-						.@"return" = .{
-							.expression = null,
-						},
-					};
-				},
-
-				else => {
-					break: parse_statement .{
-						.expression = try self.parse_expression()
-					};
-				},
-			}
-		});
-	}
-}
-
-const parse_additive = binary_operation_parser(parse_equality, &.{
-	.addition,
-	.subtraction,
-});
-
-const parse_comparison = binary_operation_parser(parse_term, &.{
-	.greater_than_comparison,
-	.greater_equals_comparison,
-	.less_than_comparison,
-	.less_equals_comparison
-});
-
-const parse_equality = binary_operation_parser(parse_comparison, &.{
-	.equals_comparison,
-});
-
-pub fn parse_expression(self: *Self) ParseError!Expression {
-	const allocator = self.arena.as_allocator();
-	const expression = try parse_additive(self);
-
-	if (self.tokenizer.token == .symbol_equals) {
-		self.tokenizer.skip_newlines();
-
-		if (self.tokenizer.token == .end) {
-			return self.report("expected assignment after `=`");
-		}
-
-		return switch (expression) {
-			.local_get => |local_get| .{.local_set = local_get},
-
-			.field_get => |field_get| .{
-				.field_set = .{
-					.object_expression = field_get.object_expression,
-					.identifier = field_get.identifier,
-					.value_expression = try coral.io.allocate_one(allocator, try self.parse_expression()),
-				},
-			},
-
-			.subscript_get => |subscript_get| .{
-				.subscript_set = .{
-					.object_expression = subscript_get.object_expression,
-					.subscript_expression = subscript_get.subscript_expression,
-					.value_expression = try coral.io.allocate_one(allocator, try self.parse_expression()),
-				},
-			},
-
-			else => self.report("expected local or field on left-hand side of expression"),
-		};
-	}
-
-	return expression;
-}
-
-fn parse_factor(self: *Self) ParseError!Expression {
-	const allocator = self.arena.as_allocator();
-
-	var expression = @as(Expression, parse: {
-		switch (self.tokenizer.token) {
-			.symbol_paren_left => {
-				self.tokenizer.skip_newlines();
-
-				if (self.tokenizer.token == .end) {
-					return self.report("expected an expression after `(`");
-				}
-
-				const expression = try self.parse_expression();
-
-				if (self.tokenizer.token != .symbol_paren_right) {
-					return self.report("expected a closing `)` after expression");
-				}
-
-				self.tokenizer.skip_newlines();
-
-				break: parse .{.grouped_expression = try coral.io.allocate_one(allocator, expression)};
-			},
-
-			.keyword_nil => {
-				self.tokenizer.skip_newlines();
-
-				break: parse .nil_literal;
-			},
-
-			.keyword_true => {
-				self.tokenizer.skip_newlines();
-
-				break: parse .true_literal;
-			},
-
-			.keyword_false => {
-				self.tokenizer.skip_newlines();
-
-				break: parse .false_literal;
-			},
-
-			.number => |value| {
-				self.tokenizer.skip_newlines();
-
-				break: parse .{.number_literal = value};
-			},
-
-			.string => |value| {
-				self.tokenizer.skip_newlines();
-
-				break: parse .{.string_literal = value};
-			},
-
-			.identifier => |identifier| {
-				self.tokenizer.skip_newlines();
-
-				break: parse .{.local_get = identifier};
-			},
-
-			.builtin => |builtin| {
-				self.tokenizer.skip_newlines();
-
-				break: parse .{.builtin = builtin};
-			},
-
-			.symbol_brace_left => {
-				var table_literal = Expression.TableLiteral.make(allocator);
-
-				self.tokenizer.skip_newlines();
-
-				while (true) {
-					switch (self.tokenizer.token) {
-						.symbol_brace_right => {
-							self.tokenizer.skip_newlines();
-
-							break: parse .{.table_literal = table_literal};
-						},
-
-						.symbol_period => {
-							self.tokenizer.step();
-
-							const identifier = switch (self.tokenizer.token) {
-								.identifier => |identifier| identifier,
-								else => return self.report("expected identifier after `.`"),
-							};
-
-							self.tokenizer.skip_newlines();
-
-							if (self.tokenizer.token != .symbol_equals) {
-								return self.report("expected `=` after symbol");
-							}
-
-							self.tokenizer.skip_newlines();
-
-							try table_literal.push_one(.{
-								.value_expression = try self.parse_expression(),
-								.key_expression = .{.symbol_literal = identifier},
-							});
-
-							switch (self.tokenizer.token) {
-								.symbol_comma => self.tokenizer.skip_newlines(),
-
-								.symbol_brace_right => {
-									self.tokenizer.skip_newlines();
-
-									break: parse .{.table_literal = table_literal};
-								},
-
-								else => return self.report("expected `,` or `}` after expression"),
-							}
-						},
-
-						.symbol_bracket_left => {
-							self.tokenizer.step();
-
-							const subscript_expression = try self.parse_expression();
-
-							if (self.tokenizer.token != .symbol_bracket_right) {
-								return self.report("expected `]` after subscript expression");
-							}
-
-							self.tokenizer.skip_newlines();
-
-							if (self.tokenizer.token != .symbol_equals) {
-								return self.report("expected `=` after `]`");
-							}
-
-							self.tokenizer.skip_newlines();
-
-							try table_literal.push_one(.{
-								.value_expression = try self.parse_expression(),
-								.key_expression = subscript_expression,
-							});
-
-							switch (self.tokenizer.token) {
-								.symbol_comma => self.tokenizer.skip_newlines(),
-
-								.symbol_brace_right => {
-									self.tokenizer.skip_newlines();
-
-									break: parse .{.table_literal = table_literal};
-								},
-
-								else => return self.report("expected `,` or `}` after expression"),
-							}
-						},
-
-						else => return self.report("expected `}` or fields in table literal"),
-					}
-				}
-			},
-
-			.symbol_minus => {
-				self.tokenizer.skip_newlines();
-
-				if (self.tokenizer.token == .end) {
-					return self.report("expected expression after numeric negation (`-`)");
-				}
-
-				break: parse .{
-					.unary_operation = .{
-						.expression = try coral.io.allocate_one(allocator, try self.parse_factor()),
-						.operator = .numeric_negation,
-					},
-				};
-			},
-
-			.symbol_bang => {
-				self.tokenizer.skip_newlines();
-
-				if (self.tokenizer.token == .end) {
-					return self.report("expected expression after boolean negation (`!`)");
-				}
-
-				break: parse .{
-					.unary_operation = .{
-						.expression = try coral.io.allocate_one(allocator, try self.parse_factor()),
-						.operator = .boolean_negation,
-					},
-				};
-			},
-
-			else => return self.report("unexpected token in expression"),
-		}
-	});
-
-	while (true) {
-		switch (self.tokenizer.token) {
-			.symbol_period => {
-				self.tokenizer.skip_newlines();
-
-				// TODO: Remove when Zig fixes miscompilation with in-place struct re-assignment.
-				const unnecessary_temp = try coral.io.allocate_one(allocator, expression);
-
-				expression = .{
-					.field_get = .{
-						.identifier = switch (self.tokenizer.token) {
-							.identifier => |field_identifier| field_identifier,
-							else => return self.report("expected identifier after `.`"),
-						},
-
-						.object_expression = unnecessary_temp,
-					},
-				};
-
-				self.tokenizer.skip_newlines();
-			},
-
-			.symbol_bracket_left => {
-				self.tokenizer.skip_newlines();
-
-				// TODO: Remove when Zig fixes miscompilation with in-place struct re-assignment.
-				const unnecessary_temp = try coral.io.allocate_one(allocator, expression);
-
-				expression = .{
-					.subscript_get = .{
-						.subscript_expression = try coral.io.allocate_one(allocator, try self.parse_expression()),
-						.object_expression = unnecessary_temp,
-					},
-				};
-
-				if (self.tokenizer.token != .symbol_bracket_right) {
-					return self.report("expected `]` subscript expression");
-				}
-
-				self.tokenizer.skip_newlines();
-			},
-
-			.symbol_paren_left => {
-				var argument_expressions = Expression.List.make(allocator);
-
-				while (true) {
-					self.tokenizer.skip_newlines();
-
-					switch (self.tokenizer.token) {
-						.symbol_paren_right => break,
-
-						else => {
-							try argument_expressions.push_one(try self.parse_expression());
-
-							switch (self.tokenizer.token) {
-								.symbol_comma => continue,
-								.symbol_paren_right => break,
-								else => return self.report("expected `,` or `)` after function argument expression"),
-							}
-						},
-					}
-				}
-
-				self.tokenizer.skip_newlines();
-
-				// TODO: Remove when Zig fixes miscompilation with in-place struct re-assignment.
-				const unnecessary_temp = try coral.io.allocate_one(allocator, expression);
-
-				expression = .{
-					.invoke = .{
-						.argument_expressions = argument_expressions,
-						.object_expression = unnecessary_temp,
-					},
-				};
-			},
-
-			else => break,
-		}
-	}
-
-	return expression;
-}
-
-const parse_term = binary_operation_parser(parse_factor, &.{
-	.multiplication,
-	.divsion,
-});

source/ona/kym/ast.zig

@@ -0,0 +1,677 @@
+const coral = @import("coral");
+
+const tokens = @import("./tokens.zig");
+
+pub const BinaryOperator = enum {
+	addition,
+	subtraction,
+	multiplication,
+	divsion,
+	equals_comparison,
+	greater_than_comparison,
+	greater_equals_comparison,
+	less_than_comparison,
+	less_equals_comparison,
+
+	fn builder(comptime build_next: ExpressionBuilder, comptime operators: []const BinaryOperator) ExpressionBuilder {
+		const Builder = struct {
+			fn build(self: *Tree) ParseError!Expression {
+				const allocator = self.arena.as_allocator();
+				var expression = try build_next(self);
+
+				inline for (operators) |operator| {
+					const token = @as(tokens.Token, switch (operator) {
+						.addition => .symbol_plus,
+						.subtraction => .symbol_minus,
+						.multiplication => .symbol_asterisk,
+						.divsion => .symbol_forward_slash,
+						.equals_comparison => .symbol_double_equals,
+						.greater_than_comparison => .symbol_greater_than,
+						.greater_equals_comparison => .symbol_greater_equals,
+						.less_than_comparison => .symbol_less_than,
+						.less_equals_comparison => .symbol_less_equals,
+					});
+
+					if (self.tokenizer.token == coral.io.tag_of(token)) {
+						self.tokenizer.step();
+
+						if (self.tokenizer.token == .end) {
+							return self.report(
+								"expected other half of expression after `" ++
+								comptime token.text() ++
+								"`");
+						}
+
+						// TODO: Remove once Zig has fixed struct self-reassignment.
+						const unnecessary_temp = try coral.io.allocate_one(allocator, expression);
+
+						expression = .{
+							.binary_operation = .{
+								.operator = operator,
+								.lhs_expression = unnecessary_temp,
+								.rhs_expression = try coral.io.allocate_one(allocator, try build_next(self)),
+							},
+						};
+					}
+				}
+
+				return expression;
+			}
+		};
+
+		return Builder.build;
+	}
+};
+
+pub const Expression = union (enum) {
+	nil_literal,
+	true_literal,
+	false_literal,
+	builtin: []const coral.io.Byte,
+	number_literal: []const coral.io.Byte,
+	string_literal: []const coral.io.Byte,
+	symbol_literal: []const coral.io.Byte,
+	table_literal: TableLiteral,
+	grouped_expression: *Expression,
+
+	local_get: struct {
+		identifier: []const coral.io.Byte,
+	},
+
+	local_set: struct {
+		identifier: []const coral.io.Byte,
+		value_expression: *Expression,
+	},
+
+	field_get: struct {
+		object_expression: *Expression,
+		identifier: []const coral.io.Byte,
+	},
+
+	field_set: struct {
+		object_expression: *Expression,
+		identifier: []const coral.io.Byte,
+		value_expression: *Expression,
+	},
+
+	subscript_get: struct {
+		object_expression: *Expression,
+		subscript_expression: *Expression,
+	},
+
+	subscript_set: struct {
+		object_expression: *Expression,
+		subscript_expression: *Expression,
+		value_expression: *Expression,
+	},
+
+	binary_operation: struct {
+		operator: BinaryOperator,
+		lhs_expression: *Expression,
+		rhs_expression: *Expression,
+	},
+
+	unary_operation: struct {
+		operator: UnaryOperator,
+		expression: *Expression,
+	},
+
+	invoke: struct {
+		object_expression: *Expression,
+		argument_expressions: List,
+	},
+
+	const List = coral.list.Stack(Expression);
+
+	const TableLiteral = coral.list.Stack(struct {
+		key_expression: Expression,
+		value_expression: Expression,
+	});
+};
+
+const ExpressionBuilder = fn (self: *Tree) ParseError!Expression;
+
+pub const ParseError = error {
+	OutOfMemory,
+	BadSyntax,
+};
+
+pub const Statement = union (enum) {
+	@"return": ?Expression,
+
+	@"if": struct {
+		condition_expression: Expression,
+		block_statements: List,
+		else_statement: ?*Statement,
+	},
+
+	@"while": struct {
+		condition_expression: Expression,
+		block_statements: List,
+	},
+
+	block: List,
+	expression: Expression,
+
+	const List = coral.list.Stack(Statement);
+};
+
+pub const Tree = struct {
+	name: []const coral.io.Byte,
+	allocator: coral.io.Allocator,
+	arena: coral.arena.Stacking,
+	error_buffer: coral.list.ByteStack,
+	tokenizer: tokens.Tokenizer,
+	parsed_statements: Statement.List,
+	has_returned: bool,
+
+	pub fn error_message(self: Tree) []const coral.io.Byte {
+		return self.error_buffer.values;
+	}
+
+	pub fn free(self: *Tree) void {
+		self.parsed_statements.free();
+		self.error_buffer.free();
+		self.arena.free();
+	}
+
+	pub fn make(allocator: coral.io.Allocator, ast_name: []const coral.io.Byte) Tree {
+		return .{
+			.arena = coral.arena.Stacking.make(allocator, 4096),
+			.error_buffer = coral.list.ByteStack.make(allocator),
+			.parsed_statements = Statement.List.make(allocator),
+			.tokenizer = .{.source = ""},
+			.allocator = allocator,
+			.name = ast_name,
+			.has_returned = false,
+		};
+	}
+
+	pub fn parse(self: *Tree, data: []const coral.io.Byte) ParseError![]const Statement {
+		self.free();
+
+		self.tokenizer = .{.source = data};
+		self.has_returned = false;
+
+		self.tokenizer.skip_newlines();
+
+		while (self.tokenizer.token != .end) {
+			try self.parsed_statements.push_one(try self.parse_statement());
+		}
+
+		return self.parsed_statements.values;
+	}
+
+	const parse_additive = BinaryOperator.builder(parse_equality, &.{
+		.addition,
+		.subtraction,
+	});
+
+	fn parse_branch(self: *Tree) ParseError!Statement {
+		const allocator = self.arena.as_allocator();
+
+		defer self.tokenizer.skip_newlines();
+
+		self.tokenizer.step();
+
+		const condition_expression = try self.parse_expression();
+
+		if (self.tokenizer.token != .symbol_colon) {
+			return self.report("expected `:` after `if` statement condition");
+		}
+
+		var statements = Statement.List.make(allocator);
+
+		self.tokenizer.skip_newlines();
+
+		while (true) {
+			switch (self.tokenizer.token) {
+				.keyword_end => {
+					return .{
+						.@"if" = .{
+							.condition_expression = condition_expression,
+							.block_statements = statements,
+							.else_statement = null,
+						},
+					};
+				},
+
+				.keyword_else => {
+					self.tokenizer.step();
+
+					if (self.tokenizer.token != .symbol_colon) {
+						return self.report("expected `:` after `if` statement condition");
+					}
+
+					var else_statements = Statement.List.make(allocator);
+
+					self.tokenizer.skip_newlines();
+
+					while (self.tokenizer.token != .keyword_end) {
+						try else_statements.push_one(try self.parse_statement());
+					}
+
+					return .{
+						.@"if" = .{
+							.else_statement = try coral.io.allocate_one(allocator, Statement{.block = else_statements}),
+							.condition_expression = condition_expression,
+							.block_statements = statements,
+						},
+					};
+				},
+
+				.keyword_elif => {
+					return .{
+						.@"if" = .{
+							.else_statement = try coral.io.allocate_one(allocator, try self.parse_branch()),
+							.condition_expression = condition_expression,
+							.block_statements = statements,
+						},
+					};
+				},
+
+				else => try statements.push_one(try self.parse_statement()),
+			}
+		}
+	}
+
+	const parse_comparison = BinaryOperator.builder(parse_term, &.{
+		.greater_than_comparison,
+		.greater_equals_comparison,
+		.less_than_comparison,
+		.less_equals_comparison
+	});
+
+	const parse_equality = BinaryOperator.builder(parse_comparison, &.{
+		.equals_comparison,
+	});
+
+	pub fn parse_expression(self: *Tree) ParseError!Expression {
+		const allocator = self.arena.as_allocator();
+		const expression = try self.parse_additive();
+
+		if (self.tokenizer.token == .symbol_equals) {
+			self.tokenizer.skip_newlines();
+
+			if (self.tokenizer.token == .end) {
+				return self.report("expected assignment after `=`");
+			}
+
+			return switch (expression) {
+				.local_get => |local_get| .{
+					.local_set = .{
+						.identifier = local_get.identifier,
+						.value_expression = try coral.io.allocate_one(allocator, try self.parse_expression()),
+					},
+				},
+
+				.field_get => |field_get| .{
+					.field_set = .{
+						.object_expression = field_get.object_expression,
+						.identifier = field_get.identifier,
+						.value_expression = try coral.io.allocate_one(allocator, try self.parse_expression()),
+					},
+				},
+
+				.subscript_get => |subscript_get| .{
+					.subscript_set = .{
+						.object_expression = subscript_get.object_expression,
+						.subscript_expression = subscript_get.subscript_expression,
+						.value_expression = try coral.io.allocate_one(allocator, try self.parse_expression()),
+					},
+				},
+
+				else => self.report("expected local or field on left-hand side of expression"),
+			};
+		}
+
+		return expression;
+	}
+
+	fn parse_factor(self: *Tree) ParseError!Expression {
+		const allocator = self.arena.as_allocator();
+
+		var expression = @as(Expression, parse: {
+			switch (self.tokenizer.token) {
+				.symbol_paren_left => {
+					self.tokenizer.skip_newlines();
+
+					if (self.tokenizer.token == .end) {
+						return self.report("expected an expression after `(`");
+					}
+
+					const expression = try self.parse_expression();
+
+					if (self.tokenizer.token != .symbol_paren_right) {
+						return self.report("expected a closing `)` after expression");
+					}
+
+					self.tokenizer.skip_newlines();
+
+					break: parse .{.grouped_expression = try coral.io.allocate_one(allocator, expression)};
+				},
+
+				.keyword_nil => {
+					self.tokenizer.skip_newlines();
+
+					break: parse .nil_literal;
+				},
+
+				.keyword_true => {
+					self.tokenizer.skip_newlines();
+
+					break: parse .true_literal;
+				},
+
+				.keyword_false => {
+					self.tokenizer.skip_newlines();
+
+					break: parse .false_literal;
+				},
+
+				.number => |value| {
+					self.tokenizer.skip_newlines();
+
+					break: parse .{.number_literal = value};
+				},
+
+				.string => |value| {
+					self.tokenizer.skip_newlines();
+
+					break: parse .{.string_literal = value};
+				},
+
+				.identifier => |identifier| {
+					self.tokenizer.skip_newlines();
+
+					break: parse .{.local_get = .{.identifier = identifier}};
+				},
+
+				.builtin => |builtin| {
+					self.tokenizer.skip_newlines();
+
+					break: parse .{.builtin = builtin};
+				},
+
+				.symbol_brace_left => {
+					var table_literal = Expression.TableLiteral.make(allocator);
+
+					self.tokenizer.skip_newlines();
+
+					while (true) {
+						switch (self.tokenizer.token) {
+							.symbol_brace_right => {
+								self.tokenizer.skip_newlines();
+
+								break: parse .{.table_literal = table_literal};
+							},
+
+							.symbol_period => {
+								self.tokenizer.step();
+
+								const identifier = switch (self.tokenizer.token) {
+									.identifier => |identifier| identifier,
+									else => return self.report("expected identifier after `.`"),
+								};
+
+								self.tokenizer.skip_newlines();
+
+								if (self.tokenizer.token != .symbol_equals) {
+									return self.report("expected `=` after symbol");
+								}
+
+								self.tokenizer.skip_newlines();
+
+								try table_literal.push_one(.{
+									.value_expression = try self.parse_expression(),
+									.key_expression = .{.symbol_literal = identifier},
+								});
+
+								switch (self.tokenizer.token) {
+									.symbol_comma => self.tokenizer.skip_newlines(),
+
+									.symbol_brace_right => {
+										self.tokenizer.skip_newlines();
+
+										break: parse .{.table_literal = table_literal};
+									},
+
+									else => return self.report("expected `,` or `}` after expression"),
+								}
+							},
+
+							.symbol_bracket_left => {
+								self.tokenizer.step();
+
+								const subscript_expression = try self.parse_expression();
+
+								if (self.tokenizer.token != .symbol_bracket_right) {
+									return self.report("expected `]` after subscript expression");
+								}
+
+								self.tokenizer.skip_newlines();
+
+								if (self.tokenizer.token != .symbol_equals) {
+									return self.report("expected `=` after `]`");
+								}
+
+								self.tokenizer.skip_newlines();
+
+								try table_literal.push_one(.{
+									.value_expression = try self.parse_expression(),
+									.key_expression = subscript_expression,
+								});
+
+								switch (self.tokenizer.token) {
+									.symbol_comma => self.tokenizer.skip_newlines(),
+
+									.symbol_brace_right => {
+										self.tokenizer.skip_newlines();
+
+										break: parse .{.table_literal = table_literal};
+									},
+
+									else => return self.report("expected `,` or `}` after expression"),
+								}
+							},
+
+							else => return self.report("expected `}` or fields in table literal"),
+						}
+					}
+				},
+
+				.symbol_minus => {
+					self.tokenizer.skip_newlines();
+
+					if (self.tokenizer.token == .end) {
+						return self.report("expected expression after numeric negation (`-`)");
+					}
+
+					break: parse .{
+						.unary_operation = .{
+							.expression = try coral.io.allocate_one(allocator, try self.parse_factor()),
+							.operator = .numeric_negation,
+						},
+					};
+				},
+
+				.symbol_bang => {
+					self.tokenizer.skip_newlines();
+
+					if (self.tokenizer.token == .end) {
+						return self.report("expected expression after boolean negation (`!`)");
+					}
+
+					break: parse .{
+						.unary_operation = .{
+							.expression = try coral.io.allocate_one(allocator, try self.parse_factor()),
+							.operator = .boolean_negation,
+						},
+					};
+				},
+
+				else => return self.report("unexpected token in expression"),
+			}
+		});
+
+		while (true) {
+			switch (self.tokenizer.token) {
+				.symbol_period => {
+					self.tokenizer.skip_newlines();
+
+					// TODO: Remove when Zig fixes miscompilation with in-place struct re-assignment.
+					const unnecessary_temp = try coral.io.allocate_one(allocator, expression);
+
+					expression = .{
+						.field_get = .{
+							.identifier = switch (self.tokenizer.token) {
+								.identifier => |field_identifier| field_identifier,
+								else => return self.report("expected identifier after `.`"),
+							},
+
+							.object_expression = unnecessary_temp,
+						},
+					};
+
+					self.tokenizer.skip_newlines();
+				},
+
+				.symbol_bracket_left => {
+					self.tokenizer.skip_newlines();
+
+					// TODO: Remove when Zig fixes miscompilation with in-place struct re-assignment.
+					const unnecessary_temp = try coral.io.allocate_one(allocator, expression);
+
+					expression = .{
+						.subscript_get = .{
+							.subscript_expression = try coral.io.allocate_one(allocator, try self.parse_expression()),
+							.object_expression = unnecessary_temp,
+						},
+					};
+
+					if (self.tokenizer.token != .symbol_bracket_right) {
+						return self.report("expected `]` subscript expression");
+					}
+
+					self.tokenizer.skip_newlines();
+				},
+
+				.symbol_paren_left => {
+					var argument_expressions = Expression.List.make(allocator);
+
+					while (true) {
+						self.tokenizer.skip_newlines();
+
+						switch (self.tokenizer.token) {
+							.symbol_paren_right => break,
+
+							else => {
+								try argument_expressions.push_one(try self.parse_expression());
+
+								switch (self.tokenizer.token) {
+									.symbol_comma => continue,
+									.symbol_paren_right => break,
+									else => return self.report("expected `,` or `)` after function argument expression"),
+								}
+							},
+						}
+					}
+
+					self.tokenizer.skip_newlines();
+
+					// TODO: Remove when Zig fixes miscompilation with in-place struct re-assignment.
+					const unnecessary_temp = try coral.io.allocate_one(allocator, expression);
+
+					expression = .{
+						.invoke = .{
+							.argument_expressions = argument_expressions,
+							.object_expression = unnecessary_temp,
+						},
+					};
+				},
+
+				else => break,
+			}
+		}
+
+		return expression;
+	}
+
+	fn parse_statement(self: *Tree) ParseError!Statement {
+		const allocator = self.arena.as_allocator();
+
+		switch (self.tokenizer.token) {
+			.keyword_return => {
+				defer self.tokenizer.skip_newlines();
+
+				if (self.has_returned) {
+					return self.report("multiple returns in lambda scope but expected only one");
+				}
+
+				self.tokenizer.step();
+
+				if (self.tokenizer.token != .end and self.tokenizer.token != .newline) {
+					return .{.@"return" = try self.parse_expression()};
+				}
+
+				if (self.tokenizer.token != .end and self.tokenizer.token != .newline) {
+					return self.report("expected end or newline after return statement");
+				}
+
+				self.has_returned = true;
+
+				return .{.@"return" = null};
+			},
+
+			.keyword_while => {
+				defer self.tokenizer.skip_newlines();
+
+				self.tokenizer.step();
+
+				const condition_expression = try self.parse_expression();
+
+				if (self.tokenizer.token != .symbol_colon) {
+					return self.report("expected `:` after `while` statement");
+				}
+
+				var statements = Statement.List.make(allocator);
+
+				self.tokenizer.skip_newlines();
+
+				while (self.tokenizer.token != .keyword_end) {
+					try statements.push_one(try self.parse_statement());
+				}
+
+				return .{
+					.@"while" = .{
+						.block_statements = statements,
+						.condition_expression = condition_expression,
+					},
+				};
+			},
+
+			.keyword_if => return self.parse_branch(),
+			else => return .{.expression = try self.parse_expression()},
+		}
+	}
+
+	const parse_term = BinaryOperator.builder(parse_factor, &.{
+		.multiplication,
+		.divsion,
+	});
+
+	fn report(self: *Tree, message: []const coral.io.Byte) ParseError {
+		coral.utf8.print_formatted(coral.list.stack_as_writer(&self.error_buffer), "{name}@{line}: {message}", .{
+			.name = self.name,
+			.line = self.tokenizer.lines_stepped,
+			.message = message,
+		}) catch return error.OutOfMemory;
+
+		return error.BadSyntax;
+	}
+};
+
+pub const UnaryOperator = enum {
+	boolean_negation,
+	numeric_negation,
+};

source/ona/kym/tokens.zig

@@ -21,7 +21,7 @@ pub const Token = union(enum) {
 	symbol_bracket_left,
 	symbol_bracket_right,
 	symbol_period,
-	symbol_lambda,
+	symbol_colon,
 	symbol_less_than,
 	symbol_less_equals,
 	symbol_greater_than,
@@ -38,6 +38,12 @@ pub const Token = union(enum) {
 	keyword_return,
 	keyword_self,
 	keyword_const,
+	keyword_if,
+	keyword_do,
+	keyword_end,
+	keyword_while,
+	keyword_else,
+	keyword_elif,
 
 	pub fn text(self: Token) []const coral.io.Byte {
 		return switch (self) {
@@ -62,7 +68,7 @@ pub const Token = union(enum) {
 			.symbol_bracket_left => "[",
 			.symbol_bracket_right => "]",
 			.symbol_period => ".",
-			.symbol_lambda => "=>",
+			.symbol_colon => ":",
 			.symbol_less_than => "<",
 			.symbol_less_equals => "<=",
 			.symbol_greater_than => ">",
@@ -79,6 +85,12 @@ pub const Token = union(enum) {
 			.keyword_true => "true",
 			.keyword_return => "return",
 			.keyword_self => "self",
+			.keyword_if => "if",
+			.keyword_do => "do",
+			.keyword_end => "end",
+			.keyword_while => "while",
+			.keyword_elif => "elif",
+			.keyword_else => "else",
 		};
 	}
 };
@@ -86,7 +98,7 @@ pub const Token = union(enum) {
 pub const Tokenizer = struct {
 	source: []const coral.io.Byte,
 	lines_stepped: usize = 1,
-	token: Token = .end,
+	token: Token = .newline,
 
 	pub fn skip_newlines(self: *Tokenizer) void {
 		self.step();
@@ -173,9 +185,29 @@ pub const Tokenizer = struct {
 							}
 						},
 
-						'n' => {
-							if (coral.io.ends_with(identifier, "il")) {
-								self.token = .keyword_nil;
+						'd' => {
+							if (coral.io.ends_with(identifier, "o")) {
+								self.token = .keyword_do;
+
+								return;
+							}
+						},
+
+						'e' => {
+							if (coral.io.ends_with(identifier, "lse")) {
+								self.token = .keyword_else;
+
+								return;
+							}
+
+							if (coral.io.ends_with(identifier, "lif")) {
+								self.token = .keyword_elif;
+
+								return;
+							}
+
+							if (coral.io.ends_with(identifier, "nd")) {
+								self.token = .keyword_end;
 
 								return;
 							}
@@ -189,9 +221,17 @@ pub const Tokenizer = struct {
 							}
 						},
 
-						't' => {
-							if (coral.io.ends_with(identifier, "rue")) {
-								self.token = .keyword_true;
+						'i' => {
+							if (coral.io.ends_with(identifier, "f")) {
+								self.token = .keyword_if;
+
+								return;
+							}
+						},
+
+						'n' => {
+							if (coral.io.ends_with(identifier, "il")) {
+								self.token = .keyword_nil;
 
 								return;
 							}
@@ -213,6 +253,22 @@ pub const Tokenizer = struct {
 							}
 						},
 
+						't' => {
+							if (coral.io.ends_with(identifier, "rue")) {
+								self.token = .keyword_true;
+
+								return;
+							}
+						},
+
+						'w' => {
+							if (coral.io.ends_with(identifier, "hile")) {
+								self.token = .keyword_while;
+
+								return;
+							}
+						},
+
 						else => {},
 					}
 
@@ -338,6 +394,13 @@ pub const Tokenizer = struct {
 					return;
 				},
 
+				':' => {
+					self.token = .symbol_colon;
+					cursor += 1;
+
+					return;
+				},
+
 				'=' => {
 					cursor += 1;
 
@@ -350,13 +413,6 @@ pub const Tokenizer = struct {
 								return;
 							},
 
-							'>' => {
-								cursor += 1;
-								self.token = .symbol_lambda;
-
-								return;
-							},
-
 							else => {},
 						}
 					}