From 83680607b7e43c16e550a8ddb80d5312dc7394d4 Mon Sep 17 00:00:00 2001
From: kayomn <kayomn@kayomn.net>
Date: Mon, 6 Nov 2023 20:16:22 +0000
Subject: [PATCH 1/6] Fix arity check error message formatting

---
 source/ona/kym.zig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/source/ona/kym.zig b/source/ona/kym.zig
index 2fc8f88..69c40fe 100644
--- a/source/ona/kym.zig
+++ b/source/ona/kym.zig
@@ -533,8 +533,8 @@ pub const RuntimeEnv = struct {
 
 			if (arg_count < arity) {
 				return self.raise(error.BadOperation, "expected `{expected}` {noun}, {provided} provided", .{
-					.expected = arity,
-					.provided = arg_count,
+					.expected = arg_count,
+					.provided = arity,
 					.noun = if (arity == 1) "argument" else "arguments",
 				});
 			}

From eb9552c390d32f0c9e2874cf5629cbc636f8bff5 Mon Sep 17 00:00:00 2001
From: kayomn <kayomn@kayomn.net>
Date: Mon, 6 Nov 2023 20:53:24 +0000
Subject: [PATCH 2/6] Merge compiler into Chunk.zig

---
 source/ona/kym/Chunk.zig    | 408 ++++++++++++++++++++++++++++++++++-
 source/ona/kym/Compiler.zig | 413 ------------------------------------
 2 files changed, 406 insertions(+), 415 deletions(-)
 delete mode 100644 source/ona/kym/Compiler.zig

diff --git a/source/ona/kym/Chunk.zig b/source/ona/kym/Chunk.zig
index bcfd649..7ebb7fb 100644
--- a/source/ona/kym/Chunk.zig
+++ b/source/ona/kym/Chunk.zig
@@ -1,6 +1,8 @@
-const app = @import("../app.zig");
+const Expr = @import("./Expr.zig");
 
-const Compiler = @import("./Compiler.zig");
+const Stmt = @import("./Stmt.zig");
+
+const app = @import("../app.zig");
 
 const coral = @import("coral");
 
@@ -25,6 +27,408 @@ const Builtin = enum {
 	vec3,
 };
 
+const Compiler = struct {
+	chunk: *Self,
+	env: *kym.RuntimeEnv,
+
+	fn compile_argument(self: *const Compiler, environment: *const tree.Environment, initial_argument: ?*const Expr) kym.RuntimeError!u8 {
+		// TODO: Exceeding 255 arguments will make the VM crash.
+		var maybe_argument = initial_argument;
+		var argument_count = @as(u8, 0);
+
+		while (maybe_argument) |argument| {
+			try self.compile_expression(environment, argument, null);
+
+			maybe_argument = argument.next;
+			argument_count += 1;
+		}
+
+		return argument_count;
+	}
+
+	fn compile_expression(self: *const Compiler, environment: *const tree.Environment, expression: *const Expr, name: ?[]const coral.io.Byte) kym.RuntimeError!void {
+		const number_format = coral.utf8.DecimalFormat{
+			.delimiter = "_",
+			.positive_prefix = .none,
+		};
+
+		switch (expression.kind) {
+			.nil_literal => try self.chunk.write(expression.line, .push_nil),
+			.true_literal => try self.chunk.write(expression.line, .push_true),
+			.false_literal => try self.chunk.write(expression.line, .push_false),
+
+			.number_literal => |literal| {
+				for (literal) |codepoint| {
+					if (codepoint == '.') {
+						return self.chunk.write(expression.line, .{
+							.push_const = try self.declare_float(number_format.parse(literal, kym.Float) orelse unreachable),
+						});
+					}
+				}
+
+				try self.chunk.write(expression.line, .{
+					.push_const = try self.declare_fixed(number_format.parse(literal, kym.Fixed) orelse unreachable),
+				});
+			},
+
+			.string_literal => |literal| {
+				try self.chunk.write(expression.line, .{.push_const = try self.declare_string(literal)});
+			},
+
+			.symbol_literal => |literal| {
+				try self.chunk.write(expression.line, .{.push_const = try self.declare_symbol(literal)});
+			},
+
+			.table_construct => |table_construct| {
+				var table_entry = table_construct.entry;
+				var field_count = @as(u32, 0);
+
+				while (table_entry) |entry| : (table_entry = entry.next) {
+					try self.compile_expression(environment, entry, null);
+
+					if (entry.kind != .key_value) {
+						try self.chunk.write(expression.line, .push_top);
+					}
+
+					field_count += 1;
+				}
+
+				try self.chunk.write(expression.line, .{.push_table = field_count});
+			},
+
+			.key_value => |key_value| {
+				try self.compile_expression(environment, key_value.value, null);
+				try self.compile_expression(environment, key_value.key, null);
+			},
+
+			.lambda_construct => |lambda_construct| {
+				var chunk = try Self.make(self.env, name orelse "<lambda>", lambda_construct.environment);
+
+				errdefer chunk.free(self.env);
+
+				if (lambda_construct.environment.capture_count == 0) {
+					try self.chunk.write(expression.line, .{.push_const = try self.declare_chunk(chunk)});
+				} else {
+					const lambda_captures = lambda_construct.environment.get_captures();
+					var index = lambda_captures.len;
+
+					while (index != 0) {
+						index -= 1;
+
+						try self.chunk.write(expression.line, switch (lambda_captures[index]) {
+							.declaration_index => |declaration_index| .{.push_local = declaration_index},
+							.capture_index => |capture_index| .{.push_binding = capture_index},
+						});
+					}
+
+					try self.chunk.write(expression.line, .{.push_const = try self.declare_chunk(chunk)});
+					try self.chunk.write(expression.line, .{.bind = lambda_construct.environment.capture_count});
+				}
+			},
+
+			.binary_op => |binary_op| {
+				try self.compile_expression(environment, binary_op.lhs_operand, null);
+				try self.compile_expression(environment, binary_op.rhs_operand, null);
+
+				try self.chunk.write(expression.line, switch (binary_op.operation) {
+					.addition => .add,
+					.subtraction => .sub,
+					.multiplication => .mul,
+					.divsion => .div,
+					.greater_equals_comparison => .cge,
+					.greater_than_comparison => .cgt,
+					.equals_comparison => .eql,
+					.less_than_comparison => .clt,
+					.less_equals_comparison => .cle,
+				});
+			},
+
+			.unary_op => |unary_op| {
+				try self.compile_expression(environment, unary_op.operand, null);
+
+				try self.chunk.write(expression.line, switch (unary_op.operation) {
+					.boolean_negation => .not,
+					.numeric_negation => .neg,
+				});
+			},
+
+			.invoke => |invoke| {
+				const argument_count = try self.compile_argument(environment, invoke.argument);
+
+				try self.compile_expression(environment, invoke.object, null);
+				try self.chunk.write(expression.line, .{.call = argument_count});
+			},
+
+			.group => |group| try self.compile_expression(environment, group, null),
+			.import_builtin => try self.chunk.write(expression.line, .{.push_builtin = .import}),
+			.print_builtin => try self.chunk.write(expression.line, .{.push_builtin = .print}),
+			.vec2_builtin => try self.chunk.write(expression.line, .{.push_builtin = .vec2}),
+			.vec3_builtin => try self.chunk.write(expression.line, .{.push_builtin = .vec3}),
+
+			.declaration_get => |declaration_get| {
+				if (get_local_index(environment, declaration_get.declaration)) |index| {
+					return self.chunk.write(expression.line, .{.push_local = index});
+				}
+
+				if (try self.get_binding_index(environment, declaration_get.declaration)) |index| {
+					try self.chunk.write(expression.line, .{.push_binding = index});
+
+					if (is_declaration_boxed(declaration_get.declaration)) {
+						try self.chunk.write(expression.line, .get_box);
+					}
+
+					return;
+				}
+
+				return self.env.raise(error.IllegalState, "local out of scope", .{});
+			},
+
+			.declaration_set => |declaration_set| {
+				if (get_local_index(environment, declaration_set.declaration)) |index| {
+					try self.compile_expression(environment, declaration_set.assign, null);
+
+					return self.chunk.write(expression.line, .{.set_local = index});
+				}
+
+				if (try self.get_binding_index(environment, declaration_set.declaration)) |index| {
+					try self.chunk.write(expression.line, .{.push_binding = index});
+					try self.compile_expression(environment, declaration_set.assign, null);
+
+					if (is_declaration_boxed(declaration_set.declaration)) {
+						try self.chunk.write(expression.line, .set_box);
+					}
+
+					return;
+				}
+
+				return self.env.raise(error.IllegalState, "local out of scope", .{});
+			},
+
+			.field_get => |field_get| {
+				try self.compile_expression(environment, field_get.object, null);
+				try self.chunk.write(expression.line, .{.push_const = try self.declare_symbol(field_get.identifier)});
+				try self.chunk.write(expression.line, .get_dynamic);
+			},
+
+			.field_set => |field_set| {
+				try self.compile_expression(environment, field_set.object, null);
+				try self.chunk.write(expression.line, .{.push_const = try self.declare_symbol(field_set.identifier)});
+				try self.compile_expression(environment, field_set.assign, null);
+				try self.chunk.write(expression.line, .set_dynamic);
+			},
+
+			.subscript_get => |subscript_get| {
+				try self.compile_expression(environment, subscript_get.object, null);
+				try self.compile_expression(environment, subscript_get.index, null);
+				try self.chunk.write(expression.line, .get_dynamic);
+			},
+
+			.subscript_set => |subscript_set| {
+				try self.compile_expression(environment, subscript_set.object, null);
+				try self.compile_expression(environment, subscript_set.index, null);
+				try self.compile_expression(environment, subscript_set.assign, null);
+				try self.chunk.write(expression.line, .set_dynamic);
+			},
+		}
+	}
+
+	pub fn compile_environment(self: *const Compiler, environment: *const tree.Environment) kym.RuntimeError!void {
+		if (environment.statement) |statement| {
+			const last_statement = try self.compile_statement(environment, statement);
+
+			if (last_statement.kind != .@"return") {
+				try self.chunk.write(last_statement.line, .push_nil);
+			}
+		}
+	}
+
+	fn compile_statement(self: *const Compiler, environment: *const tree.Environment, initial_statement: *const Stmt) kym.RuntimeError!*const Stmt {
+		var current_statement = initial_statement;
+
+		while (true) {
+			switch (current_statement.kind) {
+				.@"return" => |@"return"| {
+					if (@"return".returned_expression) |expression| {
+						try self.compile_expression(environment, expression, null);
+					} else {
+						try self.chunk.write(current_statement.line, .push_nil);
+					}
+
+					// TODO: Omit ret calls at ends of chunk.
+					try self.chunk.write(current_statement.line, .ret);
+				},
+
+				.@"while" => |@"while"| {
+					try self.compile_expression(environment, @"while".loop_expression, null);
+					try self.chunk.write(current_statement.line, .{.jf = 0});
+
+					const origin_index = @as(u32, @intCast(self.chunk.opcodes.values.len - 1));
+
+					_ = try self.compile_statement(environment, @"while".loop);
+					self.chunk.opcodes.values[origin_index].jf = @intCast(self.chunk.opcodes.values.len - 1);
+
+					try self.compile_expression(environment, @"while".loop_expression, null);
+					try self.chunk.write(current_statement.line, .{.jt = origin_index});
+				},
+
+				.@"if" => |@"if"| {
+					try self.compile_expression(environment, @"if".then_expression, null);
+					try self.chunk.write(current_statement.line, .{.jf = 0});
+
+					const origin_index = @as(u32, @intCast(self.chunk.opcodes.values.len - 1));
+
+					_ = try self.compile_statement(environment, @"if".@"then");
+					self.chunk.opcodes.values[origin_index].jf = @intCast(self.chunk.opcodes.values.len - 1);
+
+					if (@"if".@"else") |@"else"| {
+						_ = try self.compile_statement(environment, @"else");
+					}
+				},
+
+				.declare => |declare| {
+					try self.compile_expression(environment, declare.initial_expression, declare.declaration.identifier);
+
+					if (is_declaration_boxed(declare.declaration)) {
+						try self.chunk.write(current_statement.line, .push_boxed);
+					}
+				},
+
+				.top_expression => |top_expression| {
+					try self.compile_expression(environment, top_expression, null);
+
+					if (top_expression.kind == .invoke) {
+						try self.chunk.write(current_statement.line, .pop);
+					}
+				},
+			}
+
+			current_statement = current_statement.next orelse return current_statement;
+		}
+	}
+
+	const constants_max = @as(usize, coral.math.max_int(@typeInfo(u16).Int));
+
+	fn declare_chunk(self: *const Compiler, chunk: Self) kym.RuntimeError!u16 {
+		if (self.chunk.constants.values.len == coral.math.max_int(@typeInfo(u16).Int)) {
+			return self.env.raise(error.BadSyntax, "chunks cannot contain more than {max} constants", .{
+				.max = @as(usize, coral.math.max_int(@typeInfo(u16).Int)),
+			});
+		}
+
+		const constant = try self.env.new_dynamic(coral.io.bytes_of(&chunk), typeinfo);
+
+		errdefer self.env.discard(constant);
+
+		try self.chunk.constants.push_one(constant);
+
+		return @intCast(self.chunk.constants.values.len - 1);
+	}
+
+	fn declare_fixed(self: *const Compiler, fixed: kym.Fixed) kym.RuntimeError!u16 {
+		if (self.chunk.constants.values.len == constants_max) {
+			return self.env.raise(error.BadSyntax, "chunks cannot contain more than {max} constants", .{
+				.max = constants_max,
+			});
+		}
+
+		const constant = try self.env.new_fixed(fixed);
+
+		errdefer self.env.discard(constant);
+
+		try self.chunk.constants.push_one(constant);
+
+		return @intCast(self.chunk.constants.values.len - 1);
+	}
+
+	fn declare_float(self: *const Compiler, float: kym.Float) kym.RuntimeError!u16 {
+		if (self.chunk.constants.values.len == constants_max) {
+			return self.env.raise(error.BadSyntax, "chunks cannot contain more than {max} constants", .{
+				.max = constants_max,
+			});
+		}
+
+		const constant = try self.env.new_float(float);
+
+		errdefer self.env.discard(constant);
+
+		try self.chunk.constants.push_one(constant);
+
+		return @intCast(self.chunk.constants.values.len - 1);
+	}
+
+	fn declare_string(self: *const Compiler, string: []const coral.io.Byte) kym.RuntimeError!u16 {
+		if (self.chunk.constants.values.len == constants_max) {
+			return self.env.raise(error.BadSyntax, "chunks cannot contain more than {max} constants", .{
+				.max = constants_max,
+			});
+		}
+
+		const constant = try self.env.new_string(string);
+
+		errdefer self.env.discard(constant);
+
+		try self.chunk.constants.push_one(constant);
+
+		return @intCast(self.chunk.constants.values.len - 1);
+	}
+
+	fn declare_symbol(self: *const Compiler, symbol: []const coral.io.Byte) kym.RuntimeError!u16 {
+		if (self.chunk.constants.values.len == constants_max) {
+			return self.env.raise(error.BadSyntax, "chunks cannot contain more than {max} constants", .{
+				.max = constants_max,
+			});
+		}
+
+		const constant = try self.env.new_symbol(symbol);
+
+		errdefer self.env.discard(constant);
+
+		try self.chunk.constants.push_one(constant);
+
+		return @intCast(self.chunk.constants.values.len - 1);
+	}
+
+	fn get_binding_index(self: *const Compiler, environment: *const tree.Environment, declaration: *const tree.Declaration) kym.RuntimeError!?u8 {
+		var binding_index = @as(u8, 0);
+
+		while (binding_index < environment.capture_count) : (binding_index += 1) {
+			var capture = &environment.captures[binding_index];
+			var target_environment = environment.enclosing orelse return null;
+
+			while (capture.* == .capture_index) {
+				capture = &target_environment.captures[capture.capture_index];
+				target_environment = target_environment.enclosing orelse return null;
+			}
+
+			try kym.assert(self.env, capture.* == .declaration_index);
+
+			if (&target_environment.declarations[capture.declaration_index] == declaration) {
+				return binding_index;
+			}
+		}
+
+		return null;
+	}
+
+	fn get_local_index(environment: *const tree.Environment, declaration: *const tree.Declaration) ?u8 {
+		var remaining = environment.declaration_count;
+
+		while (remaining != 0) {
+			remaining -= 1;
+
+			if (&environment.declarations[remaining] == declaration) {
+				return remaining;
+			}
+		}
+
+		return null;
+	}
+
+	fn is_declaration_boxed(declaration: *const tree.Declaration) bool {
+		return declaration.is.captured and !declaration.is.readonly;
+	}
+};
+
 const ConstList = coral.list.Stack(*kym.RuntimeRef);
 
 const LineList = coral.list.Stack(u32);
diff --git a/source/ona/kym/Compiler.zig b/source/ona/kym/Compiler.zig
deleted file mode 100644
index 771331f..0000000
--- a/source/ona/kym/Compiler.zig
+++ /dev/null
@@ -1,413 +0,0 @@
-const Chunk = @import("./Chunk.zig");
-
-const Expr = @import("./Expr.zig");
-
-const Stmt = @import("./Stmt.zig");
-
-const coral = @import("coral");
-
-const kym = @import("../kym.zig");
-
-const tree = @import("./tree.zig");
-
-chunk: *Chunk,
-env: *kym.RuntimeEnv,
-
-const Self = @This();
-
-fn compile_argument(self: Self, environment: *const tree.Environment, initial_argument: ?*const Expr) kym.RuntimeError!u8 {
-	// TODO: Exceeding 255 arguments will make the VM crash.
-	var maybe_argument = initial_argument;
-	var argument_count = @as(u8, 0);
-
-	while (maybe_argument) |argument| {
-		try self.compile_expression(environment, argument, null);
-
-		maybe_argument = argument.next;
-		argument_count += 1;
-	}
-
-	return argument_count;
-}
-
-fn compile_expression(self: Self, environment: *const tree.Environment, expression: *const Expr, name: ?[]const coral.io.Byte) kym.RuntimeError!void {
-	const number_format = coral.utf8.DecimalFormat{
-		.delimiter = "_",
-		.positive_prefix = .none,
-	};
-
-	switch (expression.kind) {
-		.nil_literal => try self.chunk.write(expression.line, .push_nil),
-		.true_literal => try self.chunk.write(expression.line, .push_true),
-		.false_literal => try self.chunk.write(expression.line, .push_false),
-
-		.number_literal => |literal| {
-			for (literal) |codepoint| {
-				if (codepoint == '.') {
-					return self.chunk.write(expression.line, .{
-						.push_const = try self.declare_float(number_format.parse(literal, kym.Float) orelse unreachable),
-					});
-				}
-			}
-
-			try self.chunk.write(expression.line, .{
-				.push_const = try self.declare_fixed(number_format.parse(literal, kym.Fixed) orelse unreachable),
-			});
-		},
-
-		.string_literal => |literal| {
-			try self.chunk.write(expression.line, .{.push_const = try self.declare_string(literal)});
-		},
-
-		.symbol_literal => |literal| {
-			try self.chunk.write(expression.line, .{.push_const = try self.declare_symbol(literal)});
-		},
-
-		.table_construct => |table_construct| {
-			var table_entry = table_construct.entry;
-			var field_count = @as(u32, 0);
-
-			while (table_entry) |entry| : (table_entry = entry.next) {
-				try self.compile_expression(environment, entry, null);
-
-				if (entry.kind != .key_value) {
-					try self.chunk.write(expression.line, .push_top);
-				}
-
-				field_count += 1;
-			}
-
-			try self.chunk.write(expression.line, .{.push_table = field_count});
-		},
-
-		.key_value => |key_value| {
-			try self.compile_expression(environment, key_value.value, null);
-			try self.compile_expression(environment, key_value.key, null);
-		},
-
-		.lambda_construct => |lambda_construct| {
-			var chunk = try Chunk.make(self.env, name orelse "<lambda>", lambda_construct.environment);
-
-			errdefer chunk.free(self.env);
-
-			if (lambda_construct.environment.capture_count == 0) {
-				try self.chunk.write(expression.line, .{.push_const = try self.declare_chunk(chunk)});
-			} else {
-				const lambda_captures = lambda_construct.environment.get_captures();
-				var index = lambda_captures.len;
-
-				while (index != 0) {
-					index -= 1;
-
-					try self.chunk.write(expression.line, switch (lambda_captures[index]) {
-						.declaration_index => |declaration_index| .{.push_local = declaration_index},
-						.capture_index => |capture_index| .{.push_binding = capture_index},
-					});
-				}
-
-				try self.chunk.write(expression.line, .{.push_const = try self.declare_chunk(chunk)});
-				try self.chunk.write(expression.line, .{.bind = lambda_construct.environment.capture_count});
-			}
-		},
-
-		.binary_op => |binary_op| {
-			try self.compile_expression(environment, binary_op.lhs_operand, null);
-			try self.compile_expression(environment, binary_op.rhs_operand, null);
-
-			try self.chunk.write(expression.line, switch (binary_op.operation) {
-				.addition => .add,
-				.subtraction => .sub,
-				.multiplication => .mul,
-				.divsion => .div,
-				.greater_equals_comparison => .cge,
-				.greater_than_comparison => .cgt,
-				.equals_comparison => .eql,
-				.less_than_comparison => .clt,
-				.less_equals_comparison => .cle,
-			});
-		},
-
-		.unary_op => |unary_op| {
-			try self.compile_expression(environment, unary_op.operand, null);
-
-			try self.chunk.write(expression.line, switch (unary_op.operation) {
-				.boolean_negation => .not,
-				.numeric_negation => .neg,
-			});
-		},
-
-		.invoke => |invoke| {
-			const argument_count = try self.compile_argument(environment, invoke.argument);
-
-			try self.compile_expression(environment, invoke.object, null);
-			try self.chunk.write(expression.line, .{.call = argument_count});
-		},
-
-		.group => |group| try self.compile_expression(environment, group, null),
-		.import_builtin => try self.chunk.write(expression.line, .{.push_builtin = .import}),
-		.print_builtin => try self.chunk.write(expression.line, .{.push_builtin = .print}),
-		.vec2_builtin => try self.chunk.write(expression.line, .{.push_builtin = .vec2}),
-		.vec3_builtin => try self.chunk.write(expression.line, .{.push_builtin = .vec3}),
-
-		.declaration_get => |declaration_get| {
-			if (get_local_index(environment, declaration_get.declaration)) |index| {
-				return self.chunk.write(expression.line, .{.push_local = index});
-			}
-
-			if (try self.get_binding_index(environment, declaration_get.declaration)) |index| {
-				try self.chunk.write(expression.line, .{.push_binding = index});
-
-				if (is_declaration_boxed(declaration_get.declaration)) {
-					try self.chunk.write(expression.line, .get_box);
-				}
-
-				return;
-			}
-
-			return self.env.raise(error.IllegalState, "local out of scope", .{});
-		},
-
-		.declaration_set => |declaration_set| {
-			if (get_local_index(environment, declaration_set.declaration)) |index| {
-				try self.compile_expression(environment, declaration_set.assign, null);
-
-				return self.chunk.write(expression.line, .{.set_local = index});
-			}
-
-			if (try self.get_binding_index(environment, declaration_set.declaration)) |index| {
-				try self.chunk.write(expression.line, .{.push_binding = index});
-				try self.compile_expression(environment, declaration_set.assign, null);
-
-				if (is_declaration_boxed(declaration_set.declaration)) {
-					try self.chunk.write(expression.line, .set_box);
-				}
-
-				return;
-			}
-
-			return self.env.raise(error.IllegalState, "local out of scope", .{});
-		},
-
-		.field_get => |field_get| {
-			try self.compile_expression(environment, field_get.object, null);
-			try self.chunk.write(expression.line, .{.push_const = try self.declare_symbol(field_get.identifier)});
-			try self.chunk.write(expression.line, .get_dynamic);
-		},
-
-		.field_set => |field_set| {
-			try self.compile_expression(environment, field_set.object, null);
-			try self.chunk.write(expression.line, .{.push_const = try self.declare_symbol(field_set.identifier)});
-			try self.compile_expression(environment, field_set.assign, null);
-			try self.chunk.write(expression.line, .set_dynamic);
-		},
-
-		.subscript_get => |subscript_get| {
-			try self.compile_expression(environment, subscript_get.object, null);
-			try self.compile_expression(environment, subscript_get.index, null);
-			try self.chunk.write(expression.line, .get_dynamic);
-		},
-
-		.subscript_set => |subscript_set| {
-			try self.compile_expression(environment, subscript_set.object, null);
-			try self.compile_expression(environment, subscript_set.index, null);
-			try self.compile_expression(environment, subscript_set.assign, null);
-			try self.chunk.write(expression.line, .set_dynamic);
-		},
-	}
-}
-
-pub fn compile_environment(self: Self, environment: *const tree.Environment) kym.RuntimeError!void {
-	if (environment.statement) |statement| {
-		const last_statement = try self.compile_statement(environment, statement);
-
-		if (last_statement.kind != .@"return") {
-			try self.chunk.write(last_statement.line, .push_nil);
-		}
-	}
-}
-
-fn compile_statement(self: Self, environment: *const tree.Environment, initial_statement: *const Stmt) kym.RuntimeError!*const Stmt {
-	var current_statement = initial_statement;
-
-	while (true) {
-		switch (current_statement.kind) {
-			.@"return" => |@"return"| {
-				if (@"return".returned_expression) |expression| {
-					try self.compile_expression(environment, expression, null);
-				} else {
-					try self.chunk.write(current_statement.line, .push_nil);
-				}
-
-				// TODO: Omit ret calls at ends of chunk.
-				try self.chunk.write(current_statement.line, .ret);
-			},
-
-			.@"while" => |@"while"| {
-				try self.compile_expression(environment, @"while".loop_expression, null);
-				try self.chunk.write(current_statement.line, .{.jf = 0});
-
-				const origin_index = @as(u32, @intCast(self.chunk.opcodes.values.len - 1));
-
-				_ = try self.compile_statement(environment, @"while".loop);
-				self.chunk.opcodes.values[origin_index].jf = @intCast(self.chunk.opcodes.values.len - 1);
-
-				try self.compile_expression(environment, @"while".loop_expression, null);
-				try self.chunk.write(current_statement.line, .{.jt = origin_index});
-			},
-
-			.@"if" => |@"if"| {
-				try self.compile_expression(environment, @"if".then_expression, null);
-				try self.chunk.write(current_statement.line, .{.jf = 0});
-
-				const origin_index = @as(u32, @intCast(self.chunk.opcodes.values.len - 1));
-
-				_ = try self.compile_statement(environment, @"if".@"then");
-				self.chunk.opcodes.values[origin_index].jf = @intCast(self.chunk.opcodes.values.len - 1);
-
-				if (@"if".@"else") |@"else"| {
-					_ = try self.compile_statement(environment, @"else");
-				}
-			},
-
-			.declare => |declare| {
-				try self.compile_expression(environment, declare.initial_expression, declare.declaration.identifier);
-
-				if (is_declaration_boxed(declare.declaration)) {
-					try self.chunk.write(current_statement.line, .push_boxed);
-				}
-			},
-
-			.top_expression => |top_expression| {
-				try self.compile_expression(environment, top_expression, null);
-
-				if (top_expression.kind == .invoke) {
-					try self.chunk.write(current_statement.line, .pop);
-				}
-			},
-		}
-
-		current_statement = current_statement.next orelse return current_statement;
-	}
-}
-
-const constants_max = @as(usize, coral.math.max_int(@typeInfo(u16).Int));
-
-fn declare_chunk(self: Self, chunk: Chunk) kym.RuntimeError!u16 {
-	if (self.chunk.constants.values.len == coral.math.max_int(@typeInfo(u16).Int)) {
-		return self.env.raise(error.BadSyntax, "chunks cannot contain more than {max} constants", .{
-			.max = @as(usize, coral.math.max_int(@typeInfo(u16).Int)),
-		});
-	}
-
-	const constant = try self.env.new_dynamic(coral.io.bytes_of(&chunk), Chunk.typeinfo);
-
-	errdefer self.env.discard(constant);
-
-	try self.chunk.constants.push_one(constant);
-
-	return @intCast(self.chunk.constants.values.len - 1);
-}
-
-fn declare_fixed(self: Self, fixed: kym.Fixed) kym.RuntimeError!u16 {
-	if (self.chunk.constants.values.len == constants_max) {
-		return self.env.raise(error.BadSyntax, "chunks cannot contain more than {max} constants", .{
-			.max = constants_max,
-		});
-	}
-
-	const constant = try self.env.new_fixed(fixed);
-
-	errdefer self.env.discard(constant);
-
-	try self.chunk.constants.push_one(constant);
-
-	return @intCast(self.chunk.constants.values.len - 1);
-}
-
-fn declare_float(self: Self, float: kym.Float) kym.RuntimeError!u16 {
-	if (self.chunk.constants.values.len == constants_max) {
-		return self.env.raise(error.BadSyntax, "chunks cannot contain more than {max} constants", .{
-			.max = constants_max,
-		});
-	}
-
-	const constant = try self.env.new_float(float);
-
-	errdefer self.env.discard(constant);
-
-	try self.chunk.constants.push_one(constant);
-
-	return @intCast(self.chunk.constants.values.len - 1);
-}
-
-fn declare_string(self: Self, string: []const coral.io.Byte) kym.RuntimeError!u16 {
-	if (self.chunk.constants.values.len == constants_max) {
-		return self.env.raise(error.BadSyntax, "chunks cannot contain more than {max} constants", .{
-			.max = constants_max,
-		});
-	}
-
-	const constant = try self.env.new_string(string);
-
-	errdefer self.env.discard(constant);
-
-	try self.chunk.constants.push_one(constant);
-
-	return @intCast(self.chunk.constants.values.len - 1);
-}
-
-fn declare_symbol(self: Self, symbol: []const coral.io.Byte) kym.RuntimeError!u16 {
-	if (self.chunk.constants.values.len == constants_max) {
-		return self.env.raise(error.BadSyntax, "chunks cannot contain more than {max} constants", .{
-			.max = constants_max,
-		});
-	}
-
-	const constant = try self.env.new_symbol(symbol);
-
-	errdefer self.env.discard(constant);
-
-	try self.chunk.constants.push_one(constant);
-
-	return @intCast(self.chunk.constants.values.len - 1);
-}
-
-pub fn get_binding_index(self: *const Self, environment: *const tree.Environment, declaration: *const tree.Declaration) kym.RuntimeError!?u8 {
-	var binding_index = @as(u8, 0);
-
-	while (binding_index < environment.capture_count) : (binding_index += 1) {
-		var capture = &environment.captures[binding_index];
-		var target_environment = environment.enclosing orelse return null;
-
-		while (capture.* == .capture_index) {
-			capture = &target_environment.captures[capture.capture_index];
-			target_environment = target_environment.enclosing orelse return null;
-		}
-
-		try kym.assert(self.env, capture.* == .declaration_index);
-
-		if (&target_environment.declarations[capture.declaration_index] == declaration) {
-			return binding_index;
-		}
-	}
-
-	return null;
-}
-
-pub fn get_local_index(environment: *const tree.Environment, declaration: *const tree.Declaration) ?u8 {
-	var remaining = environment.declaration_count;
-
-	while (remaining != 0) {
-		remaining -= 1;
-
-		if (&environment.declarations[remaining] == declaration) {
-			return remaining;
-		}
-	}
-
-	return null;
-}
-
-fn is_declaration_boxed(declaration: *const tree.Declaration) bool {
-	return declaration.is.captured and !declaration.is.readonly;
-}

From b28b1a86c96ba3cd920173c6a55cdbf20fbf265e Mon Sep 17 00:00:00 2001
From: kayomn <kayomn@kayomn.net>
Date: Mon, 6 Nov 2023 22:27:09 +0000
Subject: [PATCH 3/6] Fix double free and boxing bugs in VM

---
 debug/app.ona            |  6 +++++-
 source/ona/kym.zig       |  4 ++--
 source/ona/kym/Chunk.zig | 23 +++++++++++++++++++----
 3 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/debug/app.ona b/debug/app.ona
index bb14b64..6920724 100644
--- a/debug/app.ona
+++ b/debug/app.ona
@@ -1,5 +1,9 @@
 
-let test_param = "monkey wrench"
+let wrench = "wrench"
+
+var test_param = "monkey {wrench}"
+
+test_param = "monkey"
 
 let printer = lambda (pfx):
 	@print(test_param)
diff --git a/source/ona/kym.zig b/source/ona/kym.zig
index 69c40fe..7ad0543 100644
--- a/source/ona/kym.zig
+++ b/source/ona/kym.zig
@@ -282,7 +282,7 @@ pub const RuntimeEnv = struct {
 	pub fn get_boxed(self: *RuntimeEnv, boxable: *RuntimeRef) RuntimeError!?*RuntimeRef {
 		return switch (boxable.object().payload) {
 			.boxed => |boxed| if (boxed) |boxed_value| boxed_value.acquire() else null,
-			else => self.raise(error.TypeMismatch, "{typename} is not boxable", .{.typename = boxable.typename()}),
+			else => self.raise(error.TypeMismatch, "{typename} is not box-gettable", .{.typename = boxable.typename()}),
 		};
 	}
 
@@ -624,7 +624,7 @@ pub const RuntimeEnv = struct {
 				boxed.* = if (value) |ref| ref.acquire() else null;
 			},
 
-			else => return self.raise(error.TypeMismatch, "{typename} is not boxable", .{
+			else => return self.raise(error.TypeMismatch, "{typename} is not box-settable", .{
 				.typename = boxable.typename(),
 			}),
 		}
diff --git a/source/ona/kym/Chunk.zig b/source/ona/kym/Chunk.zig
index 7ebb7fb..20be8b5 100644
--- a/source/ona/kym/Chunk.zig
+++ b/source/ona/kym/Chunk.zig
@@ -167,7 +167,14 @@ const Compiler = struct {
 
 			.declaration_get => |declaration_get| {
 				if (get_local_index(environment, declaration_get.declaration)) |index| {
-					return self.chunk.write(expression.line, .{.push_local = index});
+					if (is_declaration_boxed(declaration_get.declaration)) {
+						try self.chunk.write(expression.line, .{.push_local = index});
+						try self.chunk.write(expression.line, .get_box);
+					} else {
+						try self.chunk.write(expression.line, .{.push_local = index});
+					}
+
+					return;
 				}
 
 				if (try self.get_binding_index(environment, declaration_get.declaration)) |index| {
@@ -187,12 +194,19 @@ const Compiler = struct {
 				if (get_local_index(environment, declaration_set.declaration)) |index| {
 					try self.compile_expression(environment, declaration_set.assign, null);
 
-					return self.chunk.write(expression.line, .{.set_local = index});
+					if (is_declaration_boxed(declaration_set.declaration)) {
+						try self.chunk.write(expression.line, .{.push_local = index});
+						try self.chunk.write(expression.line, .set_box);
+					} else {
+						try self.chunk.write(expression.line, .{.set_local = index});
+					}
+
+					return;
 				}
 
 				if (try self.get_binding_index(environment, declaration_set.declaration)) |index| {
-					try self.chunk.write(expression.line, .{.push_binding = index});
 					try self.compile_expression(environment, declaration_set.assign, null);
+					try self.chunk.write(expression.line, .{.push_binding = index});
 
 					if (is_declaration_boxed(declaration_set.declaration)) {
 						try self.chunk.write(expression.line, .set_box);
@@ -730,7 +744,8 @@ pub fn execute(self: *Self, env: *kym.RuntimeEnv, frame: *const kym.Frame) kym.R
 
 				const value = try env.expect(try env.pop_local());
 
-				defer env.discard(box);
+				errdefer env.discard(value);
+
 				try env.set_boxed(box, value);
 			},
 

From 94a13b0d3c3dde275a060d82a1efb9e08287103f Mon Sep 17 00:00:00 2001
From: kayomn <kayomn@kayomn.net>
Date: Tue, 7 Nov 2023 23:02:49 +0000
Subject: [PATCH 4/6] Fix compilation errors with Stack list

---
 source/coral/list.zig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/coral/list.zig b/source/coral/list.zig
index a9f48ea..5fa5040 100644
--- a/source/coral/list.zig
+++ b/source/coral/list.zig
@@ -17,7 +17,7 @@ pub fn Stack(comptime Value: type) type {
 		}
 
 		pub fn drop(self: *Self, count: usize) bool {
-			if (math.checked_sub(self.values, count)) |updated_count| {
+			if (math.checked_sub(self.values.len, count)) |updated_count| {
 				self.values = self.values[0 .. updated_count];
 
 				return true;

From 63792ea98393ce7e175e07bd36fa41fbe6058bed Mon Sep 17 00:00:00 2001
From: kayomn <kayomn@kayomn.net>
Date: Tue, 7 Nov 2023 23:06:11 +0000
Subject: [PATCH 5/6] Make tokenization aware of string templates

---
 source/ona/kym/tokens.zig | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/source/ona/kym/tokens.zig b/source/ona/kym/tokens.zig
index 4acf6e6..cbc604d 100755
--- a/source/ona/kym/tokens.zig
+++ b/source/ona/kym/tokens.zig
@@ -31,6 +31,7 @@ pub const Token = union(enum) {
 
 	number: []const coral.io.Byte,
 	string: []const coral.io.Byte,
+	template_string: []const coral.io.Byte,
 
 	keyword_nil,
 	keyword_false,
@@ -81,6 +82,7 @@ pub const Token = union(enum) {
 
 			.number => |literal| literal,
 			.string => |literal| literal,
+			.template_string => |literal| literal,
 
 			.keyword_const => "const",
 			.keyword_nil => "nil",
@@ -305,6 +307,22 @@ pub const Stream = struct {
 					return;
 				},
 
+				'`' => {
+					cursor += 1;
+
+					const begin = cursor;
+
+					while (cursor < self.source.len) switch (self.source[cursor]) {
+						'`' => break,
+						else => cursor += 1,
+					};
+
+					self.token = .{.template_string = self.source[begin .. cursor]};
+					cursor += 1;
+
+					return;
+				},
+
 				'"' => {
 					cursor += 1;
 

From c30f10db96af773bd13a7d793a347a623085ddea Mon Sep 17 00:00:00 2001
From: kayomn <kayomn@kayomn.net>
Date: Tue, 7 Nov 2023 23:22:25 +0000
Subject: [PATCH 6/6] Implement string interpolation

---
 debug/app.ona                      |   7 +-
 source/ona/kym.zig                 |  81 ++++++++++-
 source/ona/kym/Chunk.zig           |  66 +++++++--
 source/ona/kym/tokens.zig          |   8 +-
 source/ona/kym/tree.zig            |  14 +-
 source/ona/kym/{ => tree}/Expr.zig | 212 ++++++++++++++++++++++-------
 source/ona/kym/{ => tree}/Stmt.zig |  38 +++---
 7 files changed, 331 insertions(+), 95 deletions(-)
 rename source/ona/kym/{ => tree}/Expr.zig (71%)
 rename source/ona/kym/{ => tree}/Stmt.zig (81%)

diff --git a/debug/app.ona b/debug/app.ona
index 6920724..cf95daf 100644
--- a/debug/app.ona
+++ b/debug/app.ona
@@ -1,9 +1,6 @@
 
-let wrench = "wrench"
-
-var test_param = "monkey {wrench}"
-
-test_param = "monkey"
+let tool = "wrench"
+var test_param = `monkey {tool} {2 + 1 - 1}`
 
 let printer = lambda (pfx):
 	@print(test_param)
diff --git a/source/ona/kym.zig b/source/ona/kym.zig
index 7ad0543..bbebc34 100644
--- a/source/ona/kym.zig
+++ b/source/ona/kym.zig
@@ -133,6 +133,80 @@ pub const RuntimeEnv = struct {
 		};
 	}
 
+	pub fn concat(self: *RuntimeEnv, values: []const *const RuntimeRef) RuntimeError!*RuntimeRef {
+		if (values.len == 0) {
+			return self.new_string("");
+		}
+
+		var remaining_value_count = values.len;
+
+		errdefer {
+			var poppable_value_count = values.len - remaining_value_count;
+
+			while (poppable_value_count != 0) {
+				poppable_value_count -= 1;
+
+				const popped_value = self.pop_local() catch unreachable;
+
+				coral.debug.assert(popped_value != null);
+				self.discard(popped_value.?);
+			}
+		}
+
+		var length = @as(usize, 0);
+
+		while (remaining_value_count != 0) {
+			remaining_value_count -= 1;
+
+			const value_string = try self.to_string(values[remaining_value_count]);
+
+			errdefer self.discard(value_string);
+
+			const string = value_string.as_string();
+
+			coral.debug.assert(string != null);
+
+			try self.locals.push_one(value_string);
+
+			length += string.?.len;
+		}
+
+		const buffer = try coral.io.allocate_many(self.allocator, length, @as(coral.io.Byte, 0));
+
+		errdefer self.allocator.deallocate(buffer);
+
+		var written = @as(usize, 0);
+
+		while (remaining_value_count != values.len) : (remaining_value_count += 1) {
+			const value_string = try self.pop_local();
+
+			coral.debug.assert(value_string != null);
+
+			defer self.discard(value_string.?);
+
+			const string = value_string.?.as_string();
+
+			coral.debug.assert(string != null);
+
+			coral.io.copy(buffer[written ..], string.?);
+
+			written += string.?.len;
+
+			coral.debug.assert(written <= length);
+		}
+
+		return RuntimeRef.allocate(self.allocator, .{
+			.ref_count = 1,
+
+			.payload = .{
+				.string = .{
+					.ptr = buffer.ptr,
+					.len = @intCast(buffer.len),
+				},
+			},
+		});
+	}
+
 	pub fn discard(self: *RuntimeEnv, value: *RuntimeRef) void {
 		var object = value.object();
 
@@ -573,8 +647,9 @@ pub const RuntimeEnv = struct {
 
 				if (callable.as_dynamic(Chunk.typeinfo)) |chunk_userdata| {
 					const chunk = @as(*Chunk, @ptrCast(@alignCast(chunk_userdata)));
+					const line = chunk.lines.values[chunk.cursor];
 
-					const chunk_name = try coral.utf8.alloc_formatted(self.allocator, "{name}@{line}", .{
+					const chunk_name = try coral.utf8.alloc_formatted(self.allocator, "{name}@{line_number}", .{
 						.name = get_name: {
 							const string = name.as_string();
 
@@ -583,7 +658,7 @@ pub const RuntimeEnv = struct {
 							break: get_name string.?;
 						},
 
-						.line = chunk.lines.values[chunk.cursor],
+						.line_number = line.number,
 					});
 
 					defer self.allocator.deallocate(chunk_name);
@@ -1013,6 +1088,8 @@ pub const Typeinfo = struct {
 };
 
 pub fn assert(env: *RuntimeEnv, condition: bool) RuntimeError!void {
+	coral.debug.assert(condition);
+
 	if (!condition) {
 		return env.raise(error.IllegalState, "assertion", .{});
 	}
diff --git a/source/ona/kym/Chunk.zig b/source/ona/kym/Chunk.zig
index 20be8b5..6fef2c3 100644
--- a/source/ona/kym/Chunk.zig
+++ b/source/ona/kym/Chunk.zig
@@ -1,7 +1,3 @@
-const Expr = @import("./Expr.zig");
-
-const Stmt = @import("./Stmt.zig");
-
 const app = @import("../app.zig");
 
 const coral = @import("coral");
@@ -10,6 +6,8 @@ const file = @import("../file.zig");
 
 const kym = @import("../kym.zig");
 
+const tokens = @import("./tokens.zig");
+
 const tree = @import("./tree.zig");
 
 name: *kym.RuntimeRef,
@@ -31,7 +29,7 @@ const Compiler = struct {
 	chunk: *Self,
 	env: *kym.RuntimeEnv,
 
-	fn compile_argument(self: *const Compiler, environment: *const tree.Environment, initial_argument: ?*const Expr) kym.RuntimeError!u8 {
+	fn compile_argument(self: *const Compiler, environment: *const tree.Environment, initial_argument: ?*const tree.Expr) kym.RuntimeError!u8 {
 		// TODO: Exceeding 255 arguments will make the VM crash.
 		var maybe_argument = initial_argument;
 		var argument_count = @as(u8, 0);
@@ -46,7 +44,7 @@ const Compiler = struct {
 		return argument_count;
 	}
 
-	fn compile_expression(self: *const Compiler, environment: *const tree.Environment, expression: *const Expr, name: ?[]const coral.io.Byte) kym.RuntimeError!void {
+	fn compile_expression(self: *const Compiler, environment: *const tree.Environment, expression: *const tree.Expr, name: ?[]const coral.io.Byte) kym.RuntimeError!void {
 		const number_format = coral.utf8.DecimalFormat{
 			.delimiter = "_",
 			.positive_prefix = .none,
@@ -75,6 +73,24 @@ const Compiler = struct {
 				try self.chunk.write(expression.line, .{.push_const = try self.declare_string(literal)});
 			},
 
+			.string_template => {
+				var current_expression = expression.next orelse {
+					return self.chunk.write(expression.line, .{.push_const = try self.declare_string("")});
+				};
+
+				var component_count = @as(u8, 0);
+
+				while (true) {
+					try self.compile_expression(environment, current_expression, null);
+
+					component_count += 1;
+
+					current_expression = current_expression.next orelse {
+						return self.chunk.write(expression.line, .{.push_concat = component_count});
+					};
+				}
+			},
+
 			.symbol_literal => |literal| {
 				try self.chunk.write(expression.line, .{.push_const = try self.declare_symbol(literal)});
 			},
@@ -256,7 +272,7 @@ const Compiler = struct {
 		}
 	}
 
-	fn compile_statement(self: *const Compiler, environment: *const tree.Environment, initial_statement: *const Stmt) kym.RuntimeError!*const Stmt {
+	fn compile_statement(self: *const Compiler, environment: *const tree.Environment, initial_statement: *const tree.Stmt) kym.RuntimeError!*const tree.Stmt {
 		var current_statement = initial_statement;
 
 		while (true) {
@@ -445,7 +461,7 @@ const Compiler = struct {
 
 const ConstList = coral.list.Stack(*kym.RuntimeRef);
 
-const LineList = coral.list.Stack(u32);
+const LineList = coral.list.Stack(tokens.Line);
 
 pub const Opcode = union (enum) {
 	ret,
@@ -459,6 +475,7 @@ pub const Opcode = union (enum) {
 	push_table: u32,
 	push_builtin: Builtin,
 	push_binding: u8,
+	push_concat: u8,
 	push_boxed,
 	set_local: u8,
 	get_dynamic,
@@ -540,6 +557,10 @@ pub fn dump(chunk: Self, env: *kym.RuntimeEnv) kym.RuntimeError!*kym.RuntimeRef
 				.binding = push_binding,
 			}),
 
+			.push_concat => |push_concat| coral.utf8.print_formatted(writer, "push concat ({count})\n", .{
+				.count = push_concat,
+			}),
+
 			.push_builtin => |push_builtin| coral.utf8.print_formatted(writer, "push builtin ({builtin})\n", .{
 				.builtin = switch (push_builtin) {
 					.import => "import",
@@ -670,6 +691,33 @@ pub fn execute(self: *Self, env: *kym.RuntimeEnv, frame: *const kym.Frame) kym.R
 				try env.locals.push_one(if (self.bindings[push_binding]) |value| value.acquire() else null);
 			},
 
+			.push_concat => |push_concat| {
+				const frame_locals = env.locals.values[frame.locals_top ..];
+
+				try kym.assert(env, push_concat <= frame_locals.len);
+
+				const concat_locals = frame_locals[(frame_locals.len - push_concat) .. frame_locals.len];
+
+				for (concat_locals) |value| {
+					_ = try env.expect(value);
+				}
+
+				const concatenated_value = try env.concat(@ptrCast(concat_locals));
+
+				errdefer env.discard(concatenated_value);
+
+				var to_pop = concat_locals.len;
+
+				while (to_pop != 0) : (to_pop -= 1) {
+					const popped = env.pop_local() catch unreachable;
+
+					coral.debug.assert(popped != null);
+					env.discard(popped.?);
+				}
+
+				try env.locals.push_one(concatenated_value);
+			},
+
 			.bind => |bind| {
 				const callable = try env.expect(try env.pop_local());
 
@@ -1071,7 +1119,7 @@ fn typeinfo_to_string(env: *kym.RuntimeEnv, userdata: []coral.io.Byte) coral.io.
 	return env.to_string(@as(*Self, @ptrCast(@alignCast(userdata))).name);
 }
 
-pub fn write(self: *Self, line: u32, opcode: Opcode) coral.io.AllocationError!void {
+pub fn write(self: *Self, line: tokens.Line, opcode: Opcode) coral.io.AllocationError!void {
 	try self.opcodes.push_one(opcode);
 	try self.lines.push_one(line);
 }
diff --git a/source/ona/kym/tokens.zig b/source/ona/kym/tokens.zig
index cbc604d..edb37fa 100755
--- a/source/ona/kym/tokens.zig
+++ b/source/ona/kym/tokens.zig
@@ -1,5 +1,9 @@
 const coral = @import("coral");
 
+pub const Line = struct {
+	number: u32,
+};
+
 pub const Token = union(enum) {
 	end,
 	unknown: coral.io.Byte,
@@ -105,7 +109,7 @@ pub const Token = union(enum) {
 
 pub const Stream = struct {
 	source: []const coral.io.Byte,
-	lines_stepped: u32 = 1,
+	line: Line = .{.number = 1},
 	token: Token = .newline,
 
 	pub fn skip_newlines(self: *Stream) void {
@@ -136,7 +140,7 @@ pub const Stream = struct {
 				'\n' => {
 					cursor += 1;
 					self.token = .newline;
-					self.lines_stepped += 1;
+					self.line.number += 1;
 
 					return;
 				},
diff --git a/source/ona/kym/tree.zig b/source/ona/kym/tree.zig
index 8b1c4b4..ee2ca11 100644
--- a/source/ona/kym/tree.zig
+++ b/source/ona/kym/tree.zig
@@ -1,6 +1,6 @@
-const Expr = @import("./Expr.zig");
+pub const Expr = @import("./tree/Expr.zig");
 
-const Stmt = @import("./Stmt.zig");
+pub const Stmt = @import("./tree/Stmt.zig");
 
 const coral = @import("coral");
 
@@ -163,22 +163,22 @@ pub const Root = struct {
 
 	const MessageList = coral.list.Stack([]coral.io.Byte);
 
-	pub fn report_error(self: *Root, stream: *tokens.Stream, comptime format: []const u8, args: anytype) ParseError {
+	pub fn report_error(self: *Root, line: tokens.Line, comptime format: []const u8, args: anytype) ParseError {
 		const allocator = self.arena.as_allocator();
 
-		try self.error_messages.push_one(try coral.utf8.alloc_formatted(allocator, "{line}: {message}", .{
+		try self.error_messages.push_one(try coral.utf8.alloc_formatted(allocator, "{line_number}: {message}", .{
 			.message = try coral.utf8.alloc_formatted(allocator, format, args),
-			.line = stream.lines_stepped,
+			.line_number = line.number,
 		}));
 
 		return error.BadSyntax;
 	}
 
-	pub fn report_declare_error(self: *Root, stream: *tokens.Stream, identifier: []const coral.io.Byte, @"error": Environment.DeclareError) ParseError {
+	pub fn report_declare_error(self: *Root, line: tokens.Line, identifier: []const coral.io.Byte, @"error": Environment.DeclareError) ParseError {
 		return switch (@"error") {
 			error.OutOfMemory => error.OutOfMemory,
 
-			error.DeclarationExists => self.report_error(stream, "declaration `{identifier}` already exists", .{
+			error.DeclarationExists => self.report_error(line, "declaration `{identifier}` already exists", .{
 				.identifier = identifier,
 			}),
 		};
diff --git a/source/ona/kym/Expr.zig b/source/ona/kym/tree/Expr.zig
similarity index 71%
rename from source/ona/kym/Expr.zig
rename to source/ona/kym/tree/Expr.zig
index 3213191..5d32261 100644
--- a/source/ona/kym/Expr.zig
+++ b/source/ona/kym/tree/Expr.zig
@@ -2,12 +2,12 @@ const Stmt = @import("./Stmt.zig");
 
 const coral = @import("coral");
 
-const tokens = @import("./tokens.zig");
+const tokens = @import("../tokens.zig");
 
-const tree = @import("./tree.zig");
+const tree = @import("../tree.zig");
 
 next: ?*const Self = null,
-line: u32,
+line: tokens.Line,
 
 kind: union (enum) {
 	nil_literal,
@@ -15,6 +15,7 @@ kind: union (enum) {
 	false_literal,
 	number_literal: []const coral.io.Byte,
 	string_literal: []const coral.io.Byte,
+	string_template,
 	symbol_literal: []const coral.io.Byte,
 	table_construct: TableConstruct,
 	key_value: KeyValue,
@@ -74,14 +75,14 @@ pub const BinaryOp = struct {
 						stream.step();
 
 						if (stream.token == .end) {
-							return root.report_error(stream, "expected other half of expression after `" ++ comptime token.text() ++ "`", .{});
+							return root.report_error(stream.line, "expected other half of expression after `" ++ comptime token.text() ++ "`", .{});
 						}
 
 						// TODO: Remove once Zig has fixed struct self-reassignment.
 						const unnecessary_temp = expression;
 
 						expression = try root.create_expr(.{
-							.line = stream.lines_stepped,
+							.line = stream.line,
 
 							.kind = .{
 								.binary_op = .{
@@ -155,6 +156,68 @@ pub const TableConstruct = struct {
 	entry: ?*const Self,
 };
 
+const TemplateToken = union (enum) {
+	invalid: []const coral.io.Byte,
+	literal: []const coral.io.Byte,
+	expression: []const coral.io.Byte,
+
+	fn extract(source: *[]const coral.io.Byte) ?TemplateToken {
+		var cursor = @as(usize, 0);
+
+		defer source.* = source.*[cursor ..];
+
+		while (cursor < source.len) {
+			switch (source.*[cursor]) {
+				'{' => {
+					cursor += 1;
+
+					while (true) : (cursor += 1) {
+						if (cursor == source.len) {
+							return .{.invalid = source.*[0 .. cursor]};
+						}
+
+						if (source.*[cursor] == '}') {
+							const token = TemplateToken{.expression = source.*[1 .. cursor]};
+
+							cursor += 1;
+
+							return token;
+						}
+					}
+				},
+
+				else => {
+					cursor += 1;
+
+					while (true) : (cursor += 1) {
+						if (cursor == source.len) {
+							return .{.literal = source.*[0 .. cursor]};
+						}
+
+						if (source.*[cursor] == '{') {
+							const cursor_next = cursor + 1;
+
+							if (cursor_next == source.len) {
+								return .{.invalid = source.*[0 .. cursor]};
+							}
+
+							if (source.*[cursor_next] == '{') {
+								cursor = cursor_next;
+
+								return .{.literal = source.*[0 .. cursor]};
+							}
+
+							return .{.literal = source.*[0 .. cursor]};
+						}
+					}
+				}
+			}
+		}
+
+		return null;
+	}
+};
+
 pub const UnaryOp = struct {
 	operand: *Self,
 	operation: Operation,
@@ -172,16 +235,16 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 		stream.skip_newlines();
 
 		if (stream.token == .end) {
-			return root.report_error(stream, "expected assignment after `=`", .{});
+			return root.report_error(stream.line, "expected assignment after `=`", .{});
 		}
 
 		return root.create_expr(.{
-			.line = stream.lines_stepped,
+			.line = stream.line,
 
 			.kind = switch (expression.kind) {
 				.declaration_get => |declaration_get| convert: {
 					if (declaration_get.declaration.is.readonly) {
-						return root.report_error(stream, "readonly declarations cannot be re-assigned", .{});
+						return root.report_error(stream.line, "readonly declarations cannot be re-assigned", .{});
 					}
 
 					break: convert .{
@@ -208,7 +271,7 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 					},
 				},
 
-				else => return root.report_error(stream, "expected local or field on left-hand side of expression", .{}),
+				else => return root.report_error(stream.line, "expected local or field on left-hand side of expression", .{}),
 			},
 		});
 	}
@@ -244,13 +307,13 @@ fn parse_factor(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 				const unnecessary_temp = expression;
 
 				expression = try root.create_expr(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 
 					.kind = .{
 						.field_get = .{
 							.identifier = switch (stream.token) {
 								.identifier => |field_identifier| field_identifier,
-								else => return root.report_error(stream, "expected identifier after `.`", .{}),
+								else => return root.report_error(stream.line, "expected identifier after `.`", .{}),
 							},
 
 							.object = unnecessary_temp,
@@ -268,7 +331,7 @@ fn parse_factor(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 				const unnecessary_temp = expression;
 
 				expression = try root.create_expr(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 
 					.kind = .{
 						.subscript_get = .{
@@ -279,14 +342,14 @@ fn parse_factor(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 				});
 
 				if (stream.token != .symbol_bracket_right) {
-					return root.report_error(stream, "expected closing `]` on subscript", .{});
+					return root.report_error(stream.line, "expected closing `]` on subscript", .{});
 				}
 
 				stream.skip_newlines();
 			},
 
 			.symbol_paren_left => {
-				const lines_stepped = stream.lines_stepped;
+				const lines_stepped = stream.line;
 
 				stream.skip_newlines();
 
@@ -301,7 +364,7 @@ fn parse_factor(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 						switch (stream.token) {
 							.symbol_comma => stream.skip_newlines(),
 							.symbol_paren_right => break,
-							else => return root.report_error(stream, "expected `,` or `)` after lambda argument", .{}),
+							else => return root.report_error(stream.line, "expected `,` or `)` after lambda argument", .{}),
 						}
 
 						const next_argument = try parse(root, stream, environment);
@@ -343,13 +406,13 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			const expression = try parse(root, stream, environment);
 
 			if (stream.token != .symbol_paren_right) {
-				return root.report_error(stream, "expected a closing `)` after expression", .{});
+				return root.report_error(stream.line, "expected a closing `)` after expression", .{});
 			}
 
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 				.kind = .{.group = expression},
 			});
 		},
@@ -358,7 +421,7 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 				.kind = .nil_literal,
 			});
 		},
@@ -367,7 +430,7 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 				.kind = .true_literal,
 			});
 		},
@@ -376,7 +439,7 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 				.kind = .false_literal,
 			});
 		},
@@ -385,7 +448,7 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 				.kind = .{.number_literal = value},
 			});
 		},
@@ -394,50 +457,58 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 				.kind = .{.string_literal = value},
 			});
 		},
 
+		.template_string => |value| {
+			const line = stream.line;
+
+			stream.skip_newlines();
+
+			return parse_template(root, value, line, environment);
+		},
+
 		.symbol_at => {
 			stream.step();
 
 			const identifier = switch (stream.token) {
 				.identifier => |identifier| identifier,
-				else => return root.report_error(stream, "expected identifier after `@`", .{}),
+				else => return root.report_error(stream.line, "expected identifier after `@`", .{}),
 			};
 
 			stream.skip_newlines();
 
 			if (coral.io.are_equal(identifier, "import")) {
 				return root.create_expr(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 					.kind = .import_builtin,
 				});
 			}
 
 			if (coral.io.are_equal(identifier, "print")) {
 				return root.create_expr(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 					.kind = .print_builtin,
 				});
 			}
 
 			if (coral.io.are_equal(identifier, "vec2")) {
 				return root.create_expr(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 					.kind = .vec2_builtin,
 				});
 			}
 
 			if (coral.io.are_equal(identifier, "vec3")) {
 				return root.create_expr(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 					.kind = .vec3_builtin,
 				});
 			}
 
-			return root.report_error(stream, "unexpected identifier after `@`", .{});
+			return root.report_error(stream.line, "unexpected identifier after `@`", .{});
 		},
 
 		.symbol_period => {
@@ -445,13 +516,13 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 
 			const identifier = switch (stream.token) {
 				.identifier => |identifier| identifier,
-				else => return root.report_error(stream, "expected identifier after `.`", .{}),
+				else => return root.report_error(stream.line, "expected identifier after `.`", .{}),
 			};
 
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 				.kind = .{.symbol_literal = identifier},
 			});
 		},
@@ -460,12 +531,12 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 
 				.kind = .{
 					.declaration_get = .{
 						.declaration = (try environment.resolve_declaration(identifier)) orelse {
-							return root.report_error(stream, "undefined identifier `{identifier}`", .{
+							return root.report_error(stream.line, "undefined identifier `{identifier}`", .{
 								.identifier = identifier,
 							});
 						}
@@ -478,7 +549,7 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			stream.skip_newlines();
 
 			if (stream.token != .symbol_paren_left) {
-				return root.report_error(stream, "expected `(` after opening lambda block", .{});
+				return root.report_error(stream.line, "expected `(` after opening lambda block", .{});
 			}
 
 			stream.skip_newlines();
@@ -488,11 +559,11 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			while (stream.token != .symbol_paren_right) {
 				const identifier = switch (stream.token) {
 					.identifier => |identifier| identifier,
-					else => return root.report_error(stream, "expected identifier", .{}),
+					else => return root.report_error(stream.line, "expected identifier", .{}),
 				};
 
 				_ = lambda_environment.declare_argument(identifier) catch |declare_error| {
-					return root.report_declare_error(stream, identifier, declare_error);
+					return root.report_declare_error(stream.line, identifier, declare_error);
 				};
 
 				stream.skip_newlines();
@@ -500,14 +571,14 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 				switch (stream.token) {
 					.symbol_comma => stream.skip_newlines(),
 					.symbol_paren_right => break,
-					else => return root.report_error(stream, "expected `,` or `)` after identifier", .{}),
+					else => return root.report_error(stream.line, "expected `,` or `)` after identifier", .{}),
 				}
 			}
 
 			stream.skip_newlines();
 
 			if (stream.token != .symbol_colon) {
-				return root.report_error(stream, "expected `:` after closing `)` of lambda identifiers", .{});
+				return root.report_error(stream.line, "expected `:` after closing `)` of lambda identifiers", .{});
 			}
 
 			stream.skip_newlines();
@@ -529,7 +600,7 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 				.kind = .{.lambda_construct = .{.environment = lambda_environment}},
 			});
 		},
@@ -539,7 +610,7 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 
 			if (stream.token == .symbol_brace_right) {
 				return root.create_expr(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 					.kind = .{.table_construct = .{.entry = null}},
 				});
 			}
@@ -561,13 +632,13 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			}
 
 			if (stream.token != .symbol_brace_right) {
-				return root.report_error(stream, "expected closing `}` on table construct", .{});
+				return root.report_error(stream.line, "expected closing `}` on table construct", .{});
 			}
 
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 				.kind = .{.table_construct = .{.entry = first_entry}},
 			});
 		},
@@ -576,7 +647,7 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 
 				.kind = .{
 					.unary_op = .{
@@ -591,7 +662,7 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 
 				.kind = .{
 					.unary_op = .{
@@ -602,7 +673,7 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 			});
 		},
 
-		else => return root.report_error(stream, "unexpected token in expression", .{}),
+		else => return root.report_error(stream.line, "unexpected token in expression", .{}),
 	}
 }
 
@@ -613,26 +684,26 @@ fn parse_table_entry(root: *tree.Root, stream: *tokens.Stream, environment: *tre
 
 			const field = switch (stream.token) {
 				.identifier => |identifier| identifier,
-				else => return root.report_error(stream, "expected identifier in field symbol literal", .{}),
+				else => return root.report_error(stream.line, "expected identifier in field symbol literal", .{}),
 			};
 
 			stream.skip_newlines();
 
 			if (stream.token != .symbol_equals) {
-				return root.report_error(stream, "expected `=` after table symbol key", .{});
+				return root.report_error(stream.line, "expected `=` after table symbol key", .{});
 			}
 
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 
 				.kind = .{
 					.key_value = .{
 						.value = try parse(root, stream, environment),
 
 						.key = try root.create_expr(.{
-							.line = stream.lines_stepped,
+							.line = stream.line,
 							.kind = .{.symbol_literal = field},
 						}),
 					},
@@ -646,19 +717,19 @@ fn parse_table_entry(root: *tree.Root, stream: *tokens.Stream, environment: *tre
 			const key = try parse(root, stream, environment);
 
 			if (stream.token != .symbol_bracket_right)  {
-				return root.report_error(stream, "expected `]` after subscript index expression", .{});
+				return root.report_error(stream.line, "expected `]` after subscript index expression", .{});
 			}
 
 			stream.skip_newlines();
 
 			if (stream.token != .symbol_equals) {
-				return root.report_error(stream, "expected `=` after table expression key", .{});
+				return root.report_error(stream.line, "expected `=` after table expression key", .{});
 			}
 
 			stream.skip_newlines();
 
 			return root.create_expr(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 
 				.kind = .{
 					.key_value = .{
@@ -673,6 +744,45 @@ fn parse_table_entry(root: *tree.Root, stream: *tokens.Stream, environment: *tre
 	}
 }
 
+fn parse_template(root: *tree.Root, template: []const coral.io.Byte, line: tokens.Line, environment: *tree.Environment) tree.ParseError!*Self {
+	const expression_head = try root.create_expr(.{
+		.line = line,
+		.kind = .string_template,
+	});
+
+	var expression_tail = expression_head;
+	var source = template;
+
+	while (TemplateToken.extract(&source)) |token| {
+		const expression = try switch (token) {
+			.invalid => |invalid| root.report_error(line, "invalid template format: `{invalid}`", .{
+				.invalid = invalid,
+			}),
+
+			.literal => |literal| root.create_expr(.{
+				.line = line,
+				.kind = .{.string_literal = literal},
+			}),
+
+			.expression => |expression| create: {
+				var stream = tokens.Stream{
+					.source = expression,
+					.line = line,
+				};
+
+				stream.step();
+
+				break: create try parse(root, &stream, environment);
+			},
+		};
+
+		expression_tail.next = expression;
+		expression_tail = expression;
+	}
+
+	return expression_head;
+}
+
 const parse_term = BinaryOp.parser(parse_factor, &.{
 	.multiplication,
 	.divsion,
diff --git a/source/ona/kym/Stmt.zig b/source/ona/kym/tree/Stmt.zig
similarity index 81%
rename from source/ona/kym/Stmt.zig
rename to source/ona/kym/tree/Stmt.zig
index df49893..f1cdff6 100644
--- a/source/ona/kym/Stmt.zig
+++ b/source/ona/kym/tree/Stmt.zig
@@ -2,12 +2,12 @@ const Expr = @import("./Expr.zig");
 
 const coral = @import("coral");
 
-const tokens = @import("./tokens.zig");
+const tokens = @import("../tokens.zig");
 
-const tree = @import("./tree.zig");
+const tree = @import("../tree.zig");
 
 next: ?*const Self = null,
-line: u32,
+line: tokens.Line,
 
 kind: union (enum) {
 	top_expression: *const Expr,
@@ -46,17 +46,17 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 
 			if (stream.token != .end and stream.token != .newline) {
 				return root.create_stmt(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 					.kind = .{.@"return" = .{.returned_expression = try Expr.parse(root, stream, environment)}},
 				});
 			}
 
 			if (stream.token != .end and stream.token != .newline) {
-				return root.report_error(stream, "expected end or newline after return statement", .{});
+				return root.report_error(stream.line, "expected end or newline after return statement", .{});
 			}
 
 			return root.create_stmt(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 				.kind = .{.@"return" = .{.returned_expression = null}},
 			});
 		},
@@ -69,7 +69,7 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 			const condition_expression = try Expr.parse(root, stream, environment);
 
 			if (stream.token != .symbol_colon) {
-				return root.report_error(stream, "expected `:` after `while` statement", .{});
+				return root.report_error(stream.line, "expected `:` after `while` statement", .{});
 			}
 
 			stream.skip_newlines();
@@ -88,7 +88,7 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 			}
 
 			return root.create_stmt(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 
 				.kind = .{
 					.@"while" = .{
@@ -106,13 +106,13 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 
 			const identifier = switch (stream.token) {
 				.identifier => |identifier| identifier,
-				else => return root.report_error(stream, "expected identifier after declaration", .{}),
+				else => return root.report_error(stream.line, "expected identifier after declaration", .{}),
 			};
 
 			stream.skip_newlines();
 
 			if (stream.token != .symbol_equals) {
-				return root.report_error(stream, "expected `=` after declaration `{identifier}`", .{
+				return root.report_error(stream.line, "expected `=` after declaration `{identifier}`", .{
 					.identifier = identifier,
 				});
 			}
@@ -120,7 +120,7 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 			stream.skip_newlines();
 
 			return root.create_stmt(.{
-				.line = stream.lines_stepped,
+				.line = stream.line,
 
 				.kind = .{
 					.declare = .{
@@ -129,12 +129,12 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 						.declaration = declare: {
 							if (is_constant) {
 								break: declare environment.declare_constant(identifier) catch |declaration_error| {
-									return root.report_declare_error(stream, identifier, declaration_error);
+									return root.report_declare_error(stream.line, identifier, declaration_error);
 								};
 							}
 
 							break: declare environment.declare_variable(identifier) catch |declaration_error| {
-								return root.report_declare_error(stream, identifier, declaration_error);
+								return root.report_declare_error(stream.line, identifier, declaration_error);
 							};
 						},
 					},
@@ -145,7 +145,7 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 		.keyword_if => return parse_branch(root, stream, environment),
 
 		else => return root.create_stmt(.{
-			.line = stream.lines_stepped,
+			.line = stream.line,
 			.kind = .{.top_expression = try Expr.parse(root, stream, environment)},
 		}),
 	}
@@ -157,7 +157,7 @@ fn parse_branch(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 	const expression = try Expr.parse(root, stream, environment);
 
 	if (stream.token != .symbol_colon) {
-		return root.report_error(stream, "expected `:` after `{token}`", .{.token = stream.token.text()});
+		return root.report_error(stream.line, "expected `:` after `{token}`", .{.token = stream.token.text()});
 	}
 
 	stream.skip_newlines();
@@ -171,7 +171,7 @@ fn parse_branch(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 				stream.skip_newlines();
 
 				return root.create_stmt(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 
 					.kind = .{
 						.@"if" = .{
@@ -187,7 +187,7 @@ fn parse_branch(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 				stream.step();
 
 				if (stream.token != .symbol_colon) {
-					return root.report_error(stream, "expected `:` after `if` statement condition", .{});
+					return root.report_error(stream.line, "expected `:` after `if` statement condition", .{});
 				}
 
 				stream.skip_newlines();
@@ -205,7 +205,7 @@ fn parse_branch(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 				stream.skip_newlines();
 
 				return root.create_stmt(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 
 					.kind = .{
 						.@"if" = .{
@@ -219,7 +219,7 @@ fn parse_branch(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Env
 
 			.keyword_elif => {
 				return root.create_stmt(.{
-					.line = stream.lines_stepped,
+					.line = stream.line,
 
 					.kind = .{
 						.@"if" = .{