kuroko/compiler.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>

#include "kuroko.h"
#include "compiler.h"
#include "memory.h"
#include "scanner.h"
#include "object.h"
#include "debug.h"
#include "vm.h"

/**
 * There's nothing really especially different here compared to the Lox
 * compiler from Crafting Interpreters. A handful of additional pieces
 * of functionality are added, and some work is done to make blocks use
 * indentation instead of braces, but the basic layout and operation
 * of the compiler are the same top-down Pratt parser.
 *
 * The parser error handling has been improved over the Lox compiler with
 * the addition of column offsets and a printed copy of the original source
 * line and the offending token.
 *
 * String parsing also includes escape sequence support, so you can print
 * quotation marks properly, as well as escape sequences for terminals.
 *
 * One notable part of the compiler is the handling of list comprehensions.
 * In order to support Python-style syntax, the parser has been set up to
 * support rolling back to a previous state, so that when the compiler sees
 * an expression with references to a variable that has yet to be defined it
 * will first output the expression as if that variable was a global, then it
 * will see the 'in', rewind, parse the rest of the list comprehension, and
 * then output the expression as a loop body, with the correct local references.
 *
 * if/else and try/except blocks also have to similarly handle rollback cases
 * as they can not peek forward to see if a statement after an indentation
 * block is an else/except.
 */

typedef struct {
	KrkToken current;
	KrkToken previous;
	int hadError;
	int panicMode;
} Parser;

typedef enum {
	PREC_NONE,
	PREC_ASSIGNMENT, /* = */
	PREC_OR,         /* or */
	PREC_AND,        /* and */
	PREC_BITOR,      /* | */
	PREC_BITXOR,     /* ^ */
	PREC_BITAND,     /* & */
	PREC_EQUALITY,   /* == != in */
	PREC_COMPARISON, /* < > <= >= */
	PREC_SHIFT,      /* << >> */
	PREC_TERM,       /* + - */
	PREC_FACTOR,     /* * / % */
	PREC_UNARY,      /* ! - not */
	PREC_CALL,       /* . () */
	PREC_PRIMARY
} Precedence;

typedef void (*ParseFn)(int);

typedef struct {
	const char * name;
	ParseFn prefix;
	ParseFn infix;
	Precedence precedence;
} ParseRule;

typedef struct {
	KrkToken name;
	ssize_t depth;
	int isCaptured;
} Local;

typedef struct {
	size_t index;
	int    isLocal;
} Upvalue;

typedef enum {
	TYPE_FUNCTION,
	TYPE_MODULE,
	TYPE_METHOD,
	TYPE_INIT,
} FunctionType;

typedef struct Compiler {
	struct Compiler * enclosing;
	KrkFunction * function;
	FunctionType type;
	size_t localCount;
	size_t scopeDepth;
	size_t localsSpace;
	Local  * locals;
	size_t upvaluesSpace;
	Upvalue * upvalues;

	size_t loopLocalCount;
	size_t breakCount;
	size_t breakSpace;
	int * breaks;
	size_t continueCount;
	size_t continueSpace;
	int * continues;
} Compiler;

typedef struct ClassCompiler {
	struct ClassCompiler * enclosing;
	KrkToken name;
	int hasSuperClass;
} ClassCompiler;

static Parser parser;
static Compiler * current = NULL;
static ClassCompiler * currentClass = NULL;

static KrkChunk * currentChunk() {
	return &current->function->chunk;
}

#define EMIT_CONSTANT_OP(opc, arg) do { if (arg < 256) { emitBytes(opc, arg); } \
	else { emitBytes(opc ## _LONG, arg >> 16); emitBytes(arg >> 8, arg); } } while (0)

static void initCompiler(Compiler * compiler, FunctionType type) {
	compiler->enclosing = current;
	current = compiler;
	compiler->function = NULL;
	compiler->type = type;
	compiler->scopeDepth = 0;
	compiler->function = krk_newFunction();
	compiler->localCount = 0;
	compiler->localsSpace = 8;
	compiler->locals = GROW_ARRAY(Local,NULL,0,8);
	compiler->upvaluesSpace = 0;
	compiler->upvalues = NULL;
	compiler->breakCount = 0;
	compiler->breakSpace = 0;
	compiler->breaks = NULL;
	compiler->continueCount = 0;
	compiler->continueSpace = 0;
	compiler->continues = NULL;
	compiler->loopLocalCount = 0;

	if (type != TYPE_MODULE) {
		current->function->name = krk_copyString(parser.previous.start, parser.previous.length);
	}


	if (type == TYPE_INIT || type == TYPE_METHOD) {
		Local * local = &current->locals[current->localCount++];
		local->depth = 0;
		local->isCaptured = 0;
		local->name.start = "self";
		local->name.length = 4;
	}
}

static void parsePrecedence(Precedence precedence);
static ssize_t parseVariable(const char * errorMessage);
static void variable(int canAssign);
static void defineVariable(size_t global);
static ssize_t identifierConstant(KrkToken * name);
static ssize_t resolveLocal(Compiler * compiler, KrkToken * name);
static ParseRule * getRule(KrkTokenType type);
static void defDeclaration();
static void expression();
static void statement();
static void declaration();
static void or_(int canAssign);
static void and_(int canAssign);
static void classDeclaration();
static void declareVariable();
static void namedVariable(KrkToken name, int canAssign);
static void addLocal(KrkToken name);
static void string(int canAssign);
static KrkToken decorator(size_t level, FunctionType type);
static void call(int canAssign);

static void errorAt(KrkToken * token, const char * message) {
	if (parser.panicMode) return;
	parser.panicMode = 1;

	size_t i = (token->col - 1);
	while (token->linePtr[i] && token->linePtr[i] != '\n') i++;

	fprintf(stderr, "Parse error in \"%s\" on line %d col %d (%s): %s\n"
					"    %.*s\033[31m%.*s\033[39m%.*s\n"
					"    %-*s\033[31m^\033[39m\n",
		currentChunk()->filename->chars,
		(int)token->line,
		(int)token->col,
		getRule(token->type)->name,
		message,
		(int)(token->col - 1),
		token->linePtr,
		(int)(token->literalWidth),
		token->linePtr + (token->col - 1),
		(int)(i - (token->col - 1 + token->literalWidth)),
		token->linePtr + (token->col - 1 + token->literalWidth),
		(int)token->col-1,
		""
		);
	parser.hadError = 1;
}

static void error(const char * message) {
	errorAt(&parser.previous, message);
}

static void errorAtCurrent(const char * message) {
	errorAt(&parser.current, message);
}

static void advance() {
	parser.previous = parser.current;

	for (;;) {
		parser.current = krk_scanToken();

#ifdef ENABLE_SCAN_TRACING
		if (vm.flags & KRK_ENABLE_SCAN_TRACING) {
			fprintf(stderr, "[%s %d:%d '%.*s'] ",
				getRule(parser.current.type)->name,
				(int)parser.current.line,
				(int)parser.current.col,
				(int)parser.current.length,
				parser.current.start);
		}
#endif

		if (parser.current.type == TOKEN_RETRY) continue;
		if (parser.current.type != TOKEN_ERROR) break;

		errorAtCurrent(parser.current.start);
	}
}

static void consume(KrkTokenType type, const char * message) {
	if (parser.current.type == type) {
		advance();
		return;
	}

	errorAtCurrent(message);
}

static int check(KrkTokenType type) {
	return parser.current.type == type;
}

static int match(KrkTokenType type) {
	if (!check(type)) return 0;
	advance();
	return 1;
}

static int identifiersEqual(KrkToken * a, KrkToken * b) {
	return (a->length == b->length && memcmp(a->start, b->start, a->length) == 0);
}

static KrkToken syntheticToken(const char * text) {
	KrkToken token;
	token.start = text;
	token.length = (int)strlen(text);
	return token;
}

static void emitByte(uint8_t byte) {
	krk_writeChunk(currentChunk(), byte, parser.previous.line);
}

static void emitBytes(uint8_t byte1, uint8_t byte2) {
	emitByte(byte1);
	emitByte(byte2);
}

static void emitReturn() {
	if (current->type == TYPE_INIT) {
		emitBytes(OP_GET_LOCAL, 0);
	} else if (current->type == TYPE_MODULE) {
		/* Un-pop the last stack value */
		emitBytes(OP_GET_LOCAL, 0);
	} else {
		emitByte(OP_NONE);
	}
	emitByte(OP_RETURN);
}

static KrkFunction * endCompiler() {
	emitReturn();
	KrkFunction * function = current->function;

	/* Attach contants for arguments */
	for (int i = 0; i < function->requiredArgs; ++i) {
		KrkValue value = OBJECT_VAL(krk_copyString(current->locals[i].name.start, current->locals[i].name.length));
		krk_push(value);
		krk_writeValueArray(&function->requiredArgNames, value);
		krk_pop();
	}
	for (int i = 0; i < function->keywordArgs; ++i) {
		KrkValue value = OBJECT_VAL(krk_copyString(current->locals[i+function->requiredArgs].name.start,
			current->locals[i+function->requiredArgs].name.length));
		krk_push(value);
		krk_writeValueArray(&function->keywordArgNames, value);
		krk_pop();
	}
	size_t args = current->function->requiredArgs + current->function->keywordArgs;
	if (current->function->collectsArguments) {
		KrkValue value = OBJECT_VAL(krk_copyString(current->locals[args].name.start,
			current->locals[args].name.length));
		krk_push(value);
		krk_writeValueArray(&function->keywordArgNames, value);
		krk_pop();
		args++;
	}
	if (current->function->collectsKeywords) {
		KrkValue value = OBJECT_VAL(krk_copyString(current->locals[args].name.start,
			current->locals[args].name.length));
		krk_push(value);
		krk_writeValueArray(&function->keywordArgNames, value);
		krk_pop();
		args++;
	}

#ifdef ENABLE_DISASSEMBLY
	if ((vm.flags & KRK_ENABLE_DISASSEMBLY) && !parser.hadError) {
		krk_disassembleChunk(currentChunk(), function->name ? function->name->chars : "<module>");
		fprintf(stderr, "Function metadata: requiredArgs=%d keywordArgs=%d upvalueCount=%d\n",
			function->requiredArgs, function->keywordArgs, (int)function->upvalueCount);
		fprintf(stderr, "__doc__: \"%s\"\n", function->docstring ? function->docstring->chars : "");
		fprintf(stderr, "Constants: ");
		for (size_t i = 0; i < currentChunk()->constants.count; ++i) {
			fprintf(stderr, "%d: ", (int)i);
			krk_printValueSafe(stderr, currentChunk()->constants.values[i]);
			if (i != currentChunk()->constants.count - 1) {
				fprintf(stderr, ", ");
			}
		}
		fprintf(stderr, "\nRequired arguments: ");
		int i = 0;
		for (; i < function->requiredArgs; ++i) {
			fprintf(stderr, "%.*s%s",
				(int)current->locals[i].name.length,
				current->locals[i].name.start,
				(i == function->requiredArgs - 1) ? "" : ", ");
		}
		fprintf(stderr, "\nKeyword arguments: ");
		for (; i < function->requiredArgs + function->keywordArgs; ++i) {
			fprintf(stderr, "%.*s=None%s",
				(int)current->locals[i].name.length,
				current->locals[i].name.start,
				(i == function->keywordArgs - 1) ? "" : ", ");
		}
		fprintf(stderr, "\n");
	}
#endif

	current = current->enclosing;
	return function;
}

static void freeCompiler(Compiler * compiler) {
	FREE_ARRAY(Local,compiler->locals, compiler->localsSpace);
	FREE_ARRAY(Upvalue,compiler->upvalues, compiler->upvaluesSpace);
	FREE_ARRAY(int,compiler->breaks, compiler->breakSpace);
	FREE_ARRAY(int,compiler->continues, compiler->continueSpace);
}

static size_t emitConstant(KrkValue value) {
	return krk_writeConstant(currentChunk(), value, parser.previous.line);
}

static void number(int canAssign) {
	const char * start = parser.previous.start;
	int base = 10;

	/*  These special cases for hexadecimal, binary, octal values. */
	if (start[0] == '0' && (start[1] == 'x' || start[1] == 'X')) {
		base = 16;
		start += 2;
	} else if (start[0] == '0' && (start[1] == 'b' || start[1] == 'B')) {
		base = 2;
		start += 2;
	} else if (start[0] == '0' && (start[1] == 'o' || start[1] == 'O')) {
		base = 8;
		start += 2;
	}

	/* If it wasn't a special base, it may be a floating point value. */
	if (base == 10) {
		for (size_t j = 0; j < parser.previous.length; ++j) {
			if (parser.previous.start[j] == '.') {
				double value = strtod(start, NULL);
				emitConstant(FLOATING_VAL(value));
				return;
			}
		}
	}

	/* If we got here, it's an integer of some sort. */
	long value = strtol(start, NULL, base);
	emitConstant(INTEGER_VAL(value));
}

static void binary(int canAssign) {
	KrkTokenType operatorType = parser.previous.type;
	ParseRule * rule = getRule(operatorType);
	parsePrecedence((Precedence)(rule->precedence + 1));

	switch (operatorType) {
		case TOKEN_BANG_EQUAL:    emitBytes(OP_EQUAL, OP_NOT); break;
		case TOKEN_EQUAL_EQUAL:   emitByte(OP_EQUAL); break;
		case TOKEN_GREATER:       emitByte(OP_GREATER); break;
		case TOKEN_GREATER_EQUAL: emitBytes(OP_LESS, OP_NOT); break;
		case TOKEN_LESS:          emitByte(OP_LESS); break;
		case TOKEN_LESS_EQUAL:    emitBytes(OP_GREATER, OP_NOT); break;

		case TOKEN_PIPE:        emitByte(OP_BITOR); break;
		case TOKEN_CARET:       emitByte(OP_BITXOR); break;
		case TOKEN_AMPERSAND:   emitByte(OP_BITAND); break;
		case TOKEN_LEFT_SHIFT:  emitByte(OP_SHIFTLEFT); break;
		case TOKEN_RIGHT_SHIFT: emitByte(OP_SHIFTRIGHT); break;

		case TOKEN_PLUS:     emitByte(OP_ADD); break;
		case TOKEN_MINUS:    emitByte(OP_SUBTRACT); break;
		case TOKEN_ASTERISK: emitByte(OP_MULTIPLY); break;
		case TOKEN_SOLIDUS:  emitByte(OP_DIVIDE); break;
		case TOKEN_MODULO:   emitByte(OP_MODULO); break;
		case TOKEN_IN:       emitByte(OP_EQUAL); break;
		default: return;
	}
}

static int matchAssignment(void) {
	return match(TOKEN_EQUAL) || match(TOKEN_PLUS_EQUAL) || match(TOKEN_MINUS_EQUAL) ||
		match(TOKEN_PLUS_PLUS) || match(TOKEN_MINUS_MINUS);
}

static void assignmentValue(void) {
	switch (parser.previous.type) {
		case TOKEN_PLUS_EQUAL:
			expression();
			emitByte(OP_ADD);
			break;
		case TOKEN_MINUS_EQUAL:
			expression();
			emitByte(OP_SUBTRACT);
			break;
		case TOKEN_PLUS_PLUS:
			emitConstant(INTEGER_VAL(1));
			emitByte(OP_ADD);
			break;
		case TOKEN_MINUS_MINUS:
			emitConstant(INTEGER_VAL(1));
			emitByte(OP_SUBTRACT);
			break;
		default:
			error("Unexpected operand in assignment");
			break;
	}
}

static void get_(int canAssign) {
	int isSlice = 0;
	if (match(TOKEN_COLON)) {
		emitByte(OP_NONE);
		isSlice = 1;
	} else {
		expression();
	}
	if (isSlice || match(TOKEN_COLON)) {
		if (isSlice && match(TOKEN_COLON)) {
			error("Step value not supported in slice.");
			return;
		}
		if (match(TOKEN_RIGHT_SQUARE)) {
			emitByte(OP_NONE);
		} else {
			expression();
			consume(TOKEN_RIGHT_SQUARE, "Expected ending square bracket after slice.");
		}
		if (canAssign && matchAssignment()) {
			error("Can not assign to slice.");
		} else {
			emitByte(OP_INVOKE_GETSLICE);
		}
	} else {
		consume(TOKEN_RIGHT_SQUARE, "Expected ending square bracket after index.");
		if (canAssign && match(TOKEN_EQUAL)) {
			expression();
			emitByte(OP_INVOKE_SETTER);
		} else if (canAssign && matchAssignment()) {
			emitByte(OP_SWAP);
			emitBytes(OP_DUP, 1);
			emitByte(OP_INVOKE_GETTER);
			assignmentValue();
			emitByte(OP_INVOKE_SETTER);
		} else {
			emitByte(OP_INVOKE_GETTER);
		}
	}
}

static void dot(int canAssign) {
	consume(TOKEN_IDENTIFIER, "Expected property name");
	size_t ind = identifierConstant(&parser.previous);
	if (canAssign && match(TOKEN_EQUAL)) {
		expression();
		EMIT_CONSTANT_OP(OP_SET_PROPERTY, ind);
	} else if (canAssign && matchAssignment()) {
		emitBytes(OP_DUP, 0); /* Duplicate the object */
		EMIT_CONSTANT_OP(OP_GET_PROPERTY, ind);
		assignmentValue();
		EMIT_CONSTANT_OP(OP_SET_PROPERTY, ind);
	} else {
		EMIT_CONSTANT_OP(OP_GET_PROPERTY, ind);
	}
}

static void in_(int canAssign) {
	parsePrecedence(PREC_COMPARISON);
	KrkToken contains = syntheticToken("__contains__");
	ssize_t ind = identifierConstant(&contains);
	EMIT_CONSTANT_OP(OP_GET_PROPERTY, ind);
	emitByte(OP_SWAP);
	emitBytes(OP_CALL,1);
}

static void literal(int canAssign) {
	switch (parser.previous.type) {
		case TOKEN_FALSE: emitByte(OP_FALSE); break;
		case TOKEN_NONE:  emitByte(OP_NONE); break;
		case TOKEN_TRUE:  emitByte(OP_TRUE); break;
		default: return;
	}
}

static void expression() {
	parsePrecedence(PREC_ASSIGNMENT);
}

static void varDeclaration() {
	ssize_t ind = parseVariable("Expected variable name.");

	if (match(TOKEN_EQUAL)) {
		expression();
	} else {
		emitByte(OP_NONE);
	}

	defineVariable(ind);
}

static void printStatement() {
	int argCount = 0;
	do {
		expression();
		argCount++;
	} while (match(TOKEN_COMMA));
	EMIT_CONSTANT_OP(OP_PRINT, argCount);
}

static void synchronize() {
	parser.panicMode = 0;
	while (parser.current.type != TOKEN_EOF) {
		if (parser.previous.type == TOKEN_EOL) return;

		switch (parser.current.type) {
			case TOKEN_CLASS:
			case TOKEN_DEF:
			case TOKEN_LET:
			case TOKEN_FOR:
			case TOKEN_IF:
			case TOKEN_WHILE:
			case TOKEN_PRINT:
			case TOKEN_RETURN:
				return;
			default: break;
		}

		advance();
	}
}

static void declaration() {
	if (check(TOKEN_DEF)) {
		defDeclaration();
	} else if (match(TOKEN_LET)) {
		varDeclaration();
		if (!match(TOKEN_EOL) && !match(TOKEN_EOF)) {
			error("Expected EOL after variable declaration.\n");
		}
	} else if (check(TOKEN_CLASS)) {
		classDeclaration();
	} else if (check(TOKEN_AT)) {
		decorator(0, TYPE_FUNCTION);
	} else if (match(TOKEN_EOL) || match(TOKEN_EOF)) {
		return;
	} else if (check(TOKEN_INDENTATION)) {
		return;
	} else {
		statement();
	}

	if (parser.panicMode) synchronize();
}

static void expressionStatement() {
	expression();
	emitByte(OP_POP);
}

static void beginScope() {
	current->scopeDepth++;
}

static void endScope() {
	current->scopeDepth--;
	while (current->localCount > 0 &&
	       current->locals[current->localCount - 1].depth > (ssize_t)current->scopeDepth) {
		if (current->locals[current->localCount - 1].isCaptured) {
			emitByte(OP_CLOSE_UPVALUE);
		} else {
			emitByte(OP_POP);
		}
		current->localCount--;
	}
}

static int emitJump(uint8_t opcode) {
	emitByte(opcode);
	emitBytes(0xFF, 0xFF);
	return currentChunk()->count - 2;
}

static void patchJump(int offset) {
	int jump = currentChunk()->count - offset - 2;
	if (jump > 0xFFFF) {
		error("Unsupported far jump (we'll get there)");
	}

	currentChunk()->code[offset] = (jump >> 8) & 0xFF;
	currentChunk()->code[offset + 1] =  (jump) & 0xFF;
}

static void block(size_t indentation, const char * blockName) {
	if (match(TOKEN_EOL)) {
		if (check(TOKEN_INDENTATION)) {
			size_t currentIndentation = parser.current.length;
			if (currentIndentation <= indentation) return;
			advance();
			if (!strcmp(blockName,"def") && match(TOKEN_STRING)) {
				size_t before = currentChunk()->count;
				string(0);
				/* That wrote to the chunk, rewind it; this should only ever go back two bytes
				 * because this should only happen as the first thing in a function definition,
				 * and thus this _should_ be the first constant and thus opcode + one-byte operand
				 * to OP_CONSTANT, but just to be safe we'll actually use the previous offset... */
				currentChunk()->count = before;
				/* Retreive the docstring from the constant table */
				current->function->docstring = AS_STRING(currentChunk()->constants.values[currentChunk()->constants.count-1]);
				consume(TOKEN_EOL,"Garbage after docstring defintion");
				if (!check(TOKEN_INDENTATION) || parser.current.length != currentIndentation) {
					error("Expected at least one statement in function with docstring.");
				}
				advance();
			}
			declaration();
			while (check(TOKEN_INDENTATION)) {
				if (parser.current.length < currentIndentation) break;
				advance();
				declaration();
			};
#ifdef ENABLE_SCAN_TRACING
			if (vm.flags & KRK_ENABLE_SCAN_TRACING) {
				fprintf(stderr, "finished with block %s (ind=%d) on line %d, sitting on a %s (len=%d)\n",
					blockName, (int)indentation, (int)parser.current.line,
					getRule(parser.current.type)->name, (int)parser.current.length);
			}
#endif
		}
	} else {
		statement();
	}
}

static void function(FunctionType type, size_t blockWidth) {
	Compiler compiler;
	initCompiler(&compiler, type);
	compiler.function->chunk.filename = compiler.enclosing->function->chunk.filename;

	beginScope();

	if (type == TYPE_METHOD || type == TYPE_INIT) current->function->requiredArgs = 1;

	int hasCollectors = 0;

	consume(TOKEN_LEFT_PAREN, "Expected start of parameter list after function name.");
	if (!check(TOKEN_RIGHT_PAREN)) {
		do {
			if (match(TOKEN_SELF)) {
				if (type != TYPE_INIT && type != TYPE_METHOD) {
					error("Invalid use of `self` as a function paramenter.");
				}
				continue;
			}
			if (match(TOKEN_ASTERISK)) {
				if (match(TOKEN_ASTERISK)) {
					if (hasCollectors == 2) {
						error("Duplicate ** in parameter list.");
						return;
					}
					hasCollectors = 2;
					current->function->collectsKeywords = 1;
				} else {
					if (hasCollectors) {
						error("Syntax error.");
						return;
					}
					hasCollectors = 1;
					current->function->collectsArguments = 1;
				}
				/* Collect a name, specifically "args" or "kwargs" are commont */
				ssize_t paramConstant = parseVariable("Expect parameter name.");
				defineVariable(paramConstant);
				/* Make that a valid local for this function */
				size_t myLocal = current->localCount - 1;
				EMIT_CONSTANT_OP(OP_GET_LOCAL, myLocal);
				/* Check if it's equal to the unset-kwarg-sentinel value */
				emitConstant(KWARGS_VAL(0));
				emitByte(OP_EQUAL);
				int jumpIndex = emitJump(OP_JUMP_IF_FALSE);
				/* And if it is, set it to the appropriate type */
				beginScope();
				KrkToken synth = syntheticToken(hasCollectors == 1 ? "listOf" : "dictOf");
				namedVariable(synth, 0);
				emitBytes(OP_CALL, 0);
				EMIT_CONSTANT_OP(OP_SET_LOCAL, myLocal);
				endScope();
				/* Otherwise pop the comparison. */
				patchJump(jumpIndex);
				emitByte(OP_POP); /* comparison value */
				continue;
			}
			ssize_t paramConstant = parseVariable("Expect parameter name.");
			defineVariable(paramConstant);
			if (match(TOKEN_EQUAL)) {
				/*
				 * We inline default arguments by checking if they are equal
				 * to a sentinel value and replacing them with the requested
				 * argument. This allows us to send None (useful) to override
				 * defaults that are something else. This essentially ends
				 * up as the following at the top of the function:
				 * if param == KWARGS_SENTINEL:
				 *     param = EXPRESSION
				 */
				size_t myLocal = current->localCount - 1;
				EMIT_CONSTANT_OP(OP_GET_LOCAL, myLocal);
				emitConstant(KWARGS_VAL(0));
				emitByte(OP_EQUAL);
				int jumpIndex = emitJump(OP_JUMP_IF_FALSE);
				beginScope();
				expression(); /* Read expression */
				EMIT_CONSTANT_OP(OP_SET_LOCAL, myLocal);
				endScope();
				patchJump(jumpIndex);
				emitByte(OP_POP);
				current->function->keywordArgs++;
			} else {
				current->function->requiredArgs++;
			}
		} while (match(TOKEN_COMMA));
	}
	consume(TOKEN_RIGHT_PAREN, "Expected end of parameter list.");

	consume(TOKEN_COLON, "Expected colon after function signature.");
	block(blockWidth,"def");

	KrkFunction * function = endCompiler();
	size_t ind = krk_addConstant(currentChunk(), OBJECT_VAL(function));
	EMIT_CONSTANT_OP(OP_CLOSURE, ind);

	for (size_t i = 0; i < function->upvalueCount; ++i) {
		/* TODO: if the maximum count changes, fix the sizes for this */
		emitByte(compiler.upvalues[i].isLocal ? 1 : 0);
		if (i > 255) {
			emitByte((compiler.upvalues[i].index >> 16) & 0xFF);
			emitByte((compiler.upvalues[i].index >> 8) & 0xFF);
		}
		emitByte((compiler.upvalues[i].index) & 0xFF);
	}
	freeCompiler(&compiler);
}

static void method(size_t blockWidth) {
	/* This is actually "inside of a class definition", and that might mean
	 * arbitrary blank lines we need to accept... Sorry. */
	if (match(TOKEN_EOL)) {
		return;
	}

	/* def method(...): - just like functions; unlike Python, I'm just always
	 * going to assign `self` because Lox always assigns `this`; it should not
	 * show up in the initializer list; I may add support for it being there
	 * as a redundant thing, just to make more Python stuff work with changes. */
	if (check(TOKEN_AT)) {
		decorator(0, TYPE_METHOD);
	} else {
		consume(TOKEN_DEF, "expected a definition, got nothing");
		consume(TOKEN_IDENTIFIER, "expected method name");
		size_t ind = identifierConstant(&parser.previous);
		FunctionType type = TYPE_METHOD;

		if (parser.previous.length == 8 && memcmp(parser.previous.start, "__init__", 8) == 0) {
			type = TYPE_INIT;
		}

		function(type, blockWidth);
		EMIT_CONSTANT_OP(OP_METHOD, ind);
	}
}

static void classDeclaration() {
	size_t blockWidth = (parser.previous.type == TOKEN_INDENTATION) ? parser.previous.length : 0;
	advance(); /* Collect the `class` */

	consume(TOKEN_IDENTIFIER, "Expected class name.");
	KrkToken className = parser.previous;
	size_t constInd = identifierConstant(&parser.previous);
	declareVariable();

	EMIT_CONSTANT_OP(OP_CLASS, constInd);
	defineVariable(constInd);

	ClassCompiler classCompiler;
	classCompiler.name = parser.previous;
	classCompiler.hasSuperClass = 0;
	classCompiler.enclosing = currentClass;
	currentClass = &classCompiler;

	if (match(TOKEN_LEFT_PAREN)) {
		if (match(TOKEN_IDENTIFIER)) {
			variable(0);
			if (identifiersEqual(&className, &parser.previous)) {
				error("A class can not inherit from itself.");
			}

			beginScope();
			addLocal(syntheticToken("super"));
			defineVariable(0);

			namedVariable(className, 0);
			emitByte(OP_INHERIT);
			classCompiler.hasSuperClass = 1;
		}
		consume(TOKEN_RIGHT_PAREN, "Expected closing brace after superclass.");
	}

	namedVariable(className, 0);

	consume(TOKEN_COLON, "Expected colon after class");
	if (match(TOKEN_EOL)) {
		if (check(TOKEN_INDENTATION)) {
			size_t currentIndentation = parser.current.length;
			if (currentIndentation <= blockWidth) {
				errorAtCurrent("Unexpected indentation level for class");
			}
			advance();
			if (match(TOKEN_STRING)) {
				string(0);
				emitByte(OP_DOCSTRING);
				consume(TOKEN_EOL,"Garbage after docstring defintion");
				if (!check(TOKEN_INDENTATION) || parser.current.length != currentIndentation) {
					goto _pop_class;
				}
				advance();
			}
			method(currentIndentation);
			while (check(TOKEN_INDENTATION)) {
				if (parser.current.length < currentIndentation) break;
				advance(); /* Pass the indentation */
				method(currentIndentation);
			}
#ifdef ENABLE_SCAN_TRACING
			if (vm.flags & KRK_ENABLE_SCAN_TRACING) fprintf(stderr, "Exiting from class definition on %s\n", getRule(parser.current.type)->name);
#endif
			/* Exit from block */
		}
	} /* else empty class (and at end of file?) we'll allow it for now... */
_pop_class:
	emitByte(OP_POP);
	if (classCompiler.hasSuperClass) {
		endScope();
	}
	currentClass = currentClass->enclosing;
}

static void markInitialized() {
	if (current->scopeDepth == 0) return;
	current->locals[current->localCount - 1].depth = current->scopeDepth;
}

static void defDeclaration() {
	size_t blockWidth = (parser.previous.type == TOKEN_INDENTATION) ? parser.previous.length : 0;
	advance(); /* Collect the `def` */

	ssize_t global = parseVariable("Expected function name.");
	markInitialized();
	function(TYPE_FUNCTION, blockWidth);
	defineVariable(global);
}

static KrkToken decorator(size_t level, FunctionType type) {
	size_t blockWidth = (parser.previous.type == TOKEN_INDENTATION) ? parser.previous.length : 0;
	advance(); /* Collect the `@` */

	/* Collect an identifier */
	expression();

	consume(TOKEN_EOL, "Expected line feed after decorator.");
	if (blockWidth) {
		consume(TOKEN_INDENTATION, "Expected next line after decorator to have same indentation.");
		if (parser.previous.length != blockWidth) error("Expected next line after decorator to have same indentation.");
	}

	KrkToken funcName;
	if (check(TOKEN_DEF)) {
		/* We already checked for block level */
		advance();
		consume(TOKEN_IDENTIFIER, "Expected function name.");
		funcName = parser.previous;
		if (type == TYPE_METHOD && funcName.length == 8 && !memcmp(funcName.start,"__init__",8)) {
			type = TYPE_INIT;
		}
		function(type, blockWidth);
	} else if (check(TOKEN_AT)) {
		funcName = decorator(level+1, type);
	} else {
		error("Expected a function declaration or another decorator.");
	}

	emitBytes(OP_CALL, 1);

	if (level == 0) {
		if (type == TYPE_FUNCTION) {
			parser.previous = funcName;
			declareVariable();
			size_t ind = (current->scopeDepth > 0) ? 0 : identifierConstant(&funcName);
			defineVariable(ind);
		} else {
			size_t ind = identifierConstant(&funcName);
			EMIT_CONSTANT_OP(OP_METHOD, ind);
		}
	}

	return funcName;
}

static void emitLoop(int loopStart) {

	/* Patch continue statements to point to here, before the loop operation (yes that's silly) */
	while (current->continueCount > 0 && current->continues[current->continueCount-1] > loopStart) {
		patchJump(current->continues[current->continueCount-1]);
		current->continueCount--;
	}

	emitByte(OP_LOOP);

	int offset = currentChunk()->count - loopStart + 2;
	if (offset > 0xFFFF) error("offset too big");
	emitBytes(offset >> 8, offset);

	/* Patch break statements */
}

static void ifStatement() {
	/* Figure out what block level contains us so we can match our partner else */
	size_t blockWidth = (parser.previous.type == TOKEN_INDENTATION) ? parser.previous.length : 0;
	KrkToken myPrevious = parser.previous;

	/* Collect the if token that started this statement */
	advance();

	/* Collect condition expression */
	expression();

	/* if EXPR: */
	consume(TOKEN_COLON, "Expect ':' after condition.");

	int thenJump = emitJump(OP_JUMP_IF_FALSE);
	emitByte(OP_POP);

	/* Start a new scope and enter a block */
	beginScope();
	block(blockWidth,"if");
	endScope();

	int elseJump = emitJump(OP_JUMP);
	patchJump(thenJump);
	emitByte(OP_POP);

	/* See if we have a matching else block */
	if (blockWidth == 0 || (check(TOKEN_INDENTATION) && (parser.current.length == blockWidth))) {
		/* This is complicated */
		KrkToken previous;
		if (blockWidth) {
			previous = parser.previous;
			advance();
		}
		if (match(TOKEN_ELSE)) {
			if (check(TOKEN_IF)) {
				parser.previous = myPrevious;
				ifStatement(); /* Keep nesting */
			} else {
				consume(TOKEN_COLON, "Expect ':' after else.");
				beginScope();
				block(blockWidth,"else");
				endScope();
			}
		} else {
			if (!check(TOKEN_EOF) && !check(TOKEN_EOL)) {
				krk_ungetToken(parser.current);
				parser.current = parser.previous;
				if (blockWidth) {
					parser.previous = previous;
				}
			}
		}
	}

	patchJump(elseJump);
}

static void patchBreaks(int loopStart) {
	/* Patch break statements to go here, after the loop operation and operand. */
	while (current->breakCount > 0 && current->breaks[current->breakCount-1] > loopStart) {
		patchJump(current->breaks[current->breakCount-1]);
		current->breakCount--;
	}
}

static void breakStatement() {
	if (current->breakSpace < current->breakCount + 1) {
		size_t old = current->breakSpace;
		current->breakSpace = GROW_CAPACITY(old);
		current->breaks = GROW_ARRAY(int,current->breaks,old,current->breakSpace);
	}

	for (size_t i = current->loopLocalCount; i < current->localCount; ++i) {
		emitByte(OP_POP);
	}
	current->breaks[current->breakCount++] = emitJump(OP_JUMP);
}

static void continueStatement() {
	if (current->continueSpace < current->continueCount + 1) {
		size_t old = current->continueSpace;
		current->continueSpace = GROW_CAPACITY(old);
		current->continues = GROW_ARRAY(int,current->continues,old,current->continueSpace);
	}

	for (size_t i = current->loopLocalCount; i < current->localCount; ++i) {
		emitByte(OP_POP);
	}
	current->continues[current->continueCount++] = emitJump(OP_JUMP);
}

static void whileStatement() {
	size_t blockWidth = (parser.previous.type == TOKEN_INDENTATION) ? parser.previous.length : 0;
	advance();

	int loopStart = currentChunk()->count;

	expression();
	consume(TOKEN_COLON, "Expect ':' after condition.");

	int exitJump = emitJump(OP_JUMP_IF_FALSE);
	emitByte(OP_POP);

	int oldLocalCount = current->loopLocalCount;
	current->loopLocalCount = current->localCount;
	beginScope();
	block(blockWidth,"while");
	endScope();

	current->loopLocalCount = oldLocalCount;
	emitLoop(loopStart);
	patchJump(exitJump);
	emitByte(OP_POP);
	patchBreaks(loopStart);
}

static void forStatement() {
	/* I'm not sure if I want this to be more like Python or C/Lox/etc. */
	size_t blockWidth = (parser.previous.type == TOKEN_INDENTATION) ? parser.previous.length : 0;
	advance();

	/* For now this is going to be kinda broken */
	beginScope();

	ssize_t loopInd = current->localCount;
	varDeclaration();

	int loopStart;
	int exitJump;

	if (match(TOKEN_IN)) {
		defineVariable(loopInd);

		/* ITERABLE.__iter__() */
		beginScope();
		expression();
		endScope();

		KrkToken _it = syntheticToken("__loop_iter");
		size_t indLoopIter = current->localCount;
		addLocal(_it);
		defineVariable(indLoopIter);

		KrkToken _iter = syntheticToken("__iter__");
		ssize_t ind = identifierConstant(&_iter);
		EMIT_CONSTANT_OP(OP_GET_PROPERTY, ind);
		emitBytes(OP_CALL, 0);

		/* assign */
		EMIT_CONSTANT_OP(OP_SET_LOCAL, indLoopIter);

		/* LOOP STARTS HERE */
		loopStart = currentChunk()->count;

		/* Call the iterator */
		EMIT_CONSTANT_OP(OP_GET_LOCAL, indLoopIter);
		emitBytes(OP_CALL, 0);

		/* Assign the result to our loop index */
		EMIT_CONSTANT_OP(OP_SET_LOCAL, loopInd);

		/* Get the loop iterator again */
		EMIT_CONSTANT_OP(OP_GET_LOCAL, indLoopIter);
		emitBytes(OP_EQUAL, OP_NOT);
		exitJump = emitJump(OP_JUMP_IF_FALSE);
		emitByte(OP_POP);

	} else {
		consume(TOKEN_COMMA,"expect ,");
		loopStart = currentChunk()->count;


		beginScope();
		expression(); /* condition */
		endScope();
		exitJump = emitJump(OP_JUMP_IF_FALSE);
		emitByte(OP_POP);

		if (check(TOKEN_COMMA)) {
			advance();
			int bodyJump = emitJump(OP_JUMP);
			int incrementStart = currentChunk()->count;
			beginScope();
			expression();
			endScope();
			emitByte(OP_POP);

			emitLoop(loopStart);
			loopStart = incrementStart;
			patchJump(bodyJump);
		}
	}

	consume(TOKEN_COLON,"expect :");

	int oldLocalCount = current->loopLocalCount;
	current->loopLocalCount = current->localCount;
	beginScope();
	block(blockWidth,"for");
	endScope();

	current->loopLocalCount = oldLocalCount;
	emitLoop(loopStart);
	patchJump(exitJump);
	emitByte(OP_POP);
	patchBreaks(loopStart);

	endScope();
}

static void returnStatement() {
	if (check(TOKEN_EOL) || check(TOKEN_EOF)) {
		emitReturn();
	} else {
		if (current->type == TYPE_INIT) {
			error("Can not return values from __init__");
		}
		expression();
		emitByte(OP_RETURN);
	}
}

static void tryStatement() {
	size_t blockWidth = (parser.previous.type == TOKEN_INDENTATION) ? parser.previous.length : 0;
	advance();
	consume(TOKEN_COLON, "Expect ':' after try.");

	/* Make sure we are in a local scope so this ends up on the stack */
	beginScope();
	int tryJump = emitJump(OP_PUSH_TRY);
	addLocal(syntheticToken("exception"));
	defineVariable(0);

	beginScope();
	block(blockWidth,"try");
	endScope();

	int successJump = emitJump(OP_JUMP);
	patchJump(tryJump);

	if (blockWidth == 0 || (check(TOKEN_INDENTATION) && (parser.current.length == blockWidth))) {
		KrkToken previous;
		if (blockWidth) {
			previous = parser.previous;
			advance();
		}
		if (match(TOKEN_EXCEPT)) {
			consume(TOKEN_COLON, "Expect ':' after except.");
			beginScope();
			block(blockWidth,"except");
			endScope();
		} else if (!check(TOKEN_EOL) && !check(TOKEN_EOF)) {
			krk_ungetToken(parser.current);
			parser.current = parser.previous;
			if (blockWidth) {
				parser.previous = previous;
			}
		}
	}

	patchJump(successJump);
	endScope(); /* will pop the exception handler */
}

static void raiseStatement() {
	expression();
	emitByte(OP_RAISE);
}

static void importStatement() {
	consume(TOKEN_IDENTIFIER, "Expected module name");
	size_t ind = identifierConstant(&parser.previous);
	EMIT_CONSTANT_OP(OP_IMPORT, ind);
	if (match(TOKEN_AS)) {
		consume(TOKEN_IDENTIFIER, "Expected identifier after `as`");
		ind = identifierConstant(&parser.previous);
	}
	declareVariable();
	defineVariable(ind);
}

static void exportStatement() {
	do {
		consume(TOKEN_IDENTIFIER, "only named variable may be exported to the global namespace");
		namedVariable(parser.previous, 0);
		namedVariable(parser.previous, 0);
		size_t ind = identifierConstant(&parser.previous);
		EMIT_CONSTANT_OP(OP_DEFINE_GLOBAL, ind);
		EMIT_CONSTANT_OP(OP_SET_GLOBAL, ind);
		emitByte(OP_POP);
	} while (match(TOKEN_COMMA));
}

static void statement() {
	if (match(TOKEN_EOL) || match(TOKEN_EOF)) {
		return; /* Meaningless blank line */
	}

	if (check(TOKEN_IF)) {
		ifStatement();
	} else if (check(TOKEN_WHILE)) {
		whileStatement();
	} else if (check(TOKEN_FOR)) {
		forStatement();
	} else if (check(TOKEN_TRY)) {
		tryStatement();
	} else {
		if (match(TOKEN_PRINT)) {
			printStatement();
		} else if (match(TOKEN_EXPORT)) {
			exportStatement();
		} else if (match(TOKEN_RAISE)) {
			raiseStatement();
		} else if (match(TOKEN_RETURN)) {
			returnStatement();
		} else if (match(TOKEN_IMPORT)) {
			importStatement();
		} else if (match(TOKEN_BREAK)) {
			breakStatement();
		} else if (match(TOKEN_CONTINUE)) {
			continueStatement();
		} else {
			expressionStatement();
		}
		if (!match(TOKEN_EOL) && !match(TOKEN_EOF)) {
			errorAtCurrent("Unexpected token after statement.");
		}
	}
}

static void grouping(int canAssign) {
	expression();
	consume(TOKEN_RIGHT_PAREN, "Expect ')' after expression.");
}

static void unary(int canAssign) {
	KrkTokenType operatorType = parser.previous.type;

	parsePrecedence(PREC_UNARY);

	switch (operatorType) {
		case TOKEN_MINUS: emitByte(OP_NEGATE); break;
		case TOKEN_TILDE: emitByte(OP_BITNEGATE); break;

		/* These are equivalent */
		case TOKEN_BANG:
		case TOKEN_NOT:
			emitByte(OP_NOT);
			break;

		default: return;
	}
}

static void string(int type) {
	/* We'll just build with a flexible array like everything else. */
	size_t stringCapacity = 0;
	size_t stringLength   = 0;
	char * stringBytes    = 0;
#define PUSH_CHAR(c) do { if (stringCapacity < stringLength + 1) { \
		size_t old = stringCapacity; stringCapacity = GROW_CAPACITY(old); \
		stringBytes = GROW_ARRAY(char, stringBytes, old, stringCapacity); \
	} stringBytes[stringLength++] = c; } while (0)

	/* This should capture everything but the quotes. */
	do {
		int type = parser.previous.type == TOKEN_BIG_STRING ? 3 : 1;
		const char * c = parser.previous.start + type;
		while (c < parser.previous.start + parser.previous.length - type) {
			if (*c == '\\') {
				switch (c[1]) {
					case 'n': PUSH_CHAR('\n'); break;
					case 'r': PUSH_CHAR('\r'); break;
					case 't': PUSH_CHAR('\t'); break;
					case '[': PUSH_CHAR('\033'); break;
					case '\n': break;
					default: PUSH_CHAR(c[1]); break;
				}
				c += 2;
			} else {
				PUSH_CHAR(*c);
				c++;
			}
		}
	} while (match(TOKEN_STRING) || match(TOKEN_BIG_STRING));
	emitConstant(OBJECT_VAL(krk_copyString(stringBytes,stringLength)));
	FREE_ARRAY(char,stringBytes,stringCapacity);
}

static size_t addUpvalue(Compiler * compiler, ssize_t index, int isLocal) {
	size_t upvalueCount = compiler->function->upvalueCount;
	for (size_t i = 0; i < upvalueCount; ++i) {
		Upvalue * upvalue = &compiler->upvalues[i];
		if ((ssize_t)upvalue->index == index && upvalue->isLocal == isLocal) {
			return i;
		}
	}
	if (upvalueCount + 1 > current->upvaluesSpace) {
		size_t old = current->upvaluesSpace;
		current->upvaluesSpace = GROW_CAPACITY(old);
		current->upvalues = GROW_ARRAY(Upvalue,current->upvalues,old,current->upvaluesSpace);
	}
	compiler->upvalues[upvalueCount].isLocal = isLocal;
	compiler->upvalues[upvalueCount].index = index;
	return compiler->function->upvalueCount++;
}

static ssize_t resolveUpvalue(Compiler * compiler, KrkToken * name) {
	if (compiler->enclosing == NULL) return -1;
	ssize_t local = resolveLocal(compiler->enclosing, name);
	if (local != -1) {
		compiler->enclosing->locals[local].isCaptured = 1;
		return addUpvalue(compiler, local, 1);
	}
	ssize_t upvalue = resolveUpvalue(compiler->enclosing, name);
	if (upvalue != -1) {
		return addUpvalue(compiler, upvalue, 0);
	}
	return -1;
}

#define DO_VARIABLE(opset,opget) do { \
	if (canAssign && match(TOKEN_EQUAL)) { \
		expression(); \
		EMIT_CONSTANT_OP(opset, arg); \
	} else if (canAssign && matchAssignment()) { \
		EMIT_CONSTANT_OP(opget, arg); \
		assignmentValue(); \
		EMIT_CONSTANT_OP(opset, arg); \
	} else { \
		EMIT_CONSTANT_OP(opget, arg); \
	} } while (0)

static void namedVariable(KrkToken name, int canAssign) {
	ssize_t arg = resolveLocal(current, &name);
	if (arg != -1) {
		DO_VARIABLE(OP_SET_LOCAL, OP_GET_LOCAL);
	} else if ((arg = resolveUpvalue(current, &name)) != -1) {
		DO_VARIABLE(OP_SET_UPVALUE, OP_GET_UPVALUE);
	} else {
		arg = identifierConstant(&name);
		DO_VARIABLE(OP_SET_GLOBAL, OP_GET_GLOBAL);
	}
}
#undef DO_VARIABLE

static void variable(int canAssign) {
	namedVariable(parser.previous, canAssign);
}

static void self(int canAssign) {
	if (currentClass == NULL) {
		error("Invalid reference to `self` outside of a class method.");
		return;
	}
	variable(0);
}

static void super_(int canAssign) {
	if (currentClass == NULL) {
		error("Invalid reference to `super` outside of a class.");
	} else if (!currentClass->hasSuperClass) {
		error("Invalid reference to `super` from a base class.");
	}
	consume(TOKEN_LEFT_PAREN, "Expected `super` to be called.");
	consume(TOKEN_RIGHT_PAREN, "`super` can not take arguments.");
	consume(TOKEN_DOT, "Expected a field of `super()` to be referenced.");
	consume(TOKEN_IDENTIFIER, "Expected a field name.");
	size_t ind = identifierConstant(&parser.previous);
	namedVariable(syntheticToken("self"), 0);
	namedVariable(syntheticToken("super"), 0);
	EMIT_CONSTANT_OP(OP_GET_SUPER, ind);
}

static void list(int canAssign) {
	size_t     chunkBefore = currentChunk()->count;

	KrkToken listOf = syntheticToken("listOf");
	size_t ind = identifierConstant(&listOf);
	EMIT_CONSTANT_OP(OP_GET_GLOBAL, ind);

	if (!check(TOKEN_RIGHT_SQUARE)) {
		KrkScanner scannerBefore = krk_tellScanner();
		Parser  parserBefore = parser;
		expression();

		/* This is a bit complicated and the Pratt parser does not handle it
		 * well; if we read an expression and then saw a `for`, we need to back
		 * up and start over, as we'll need to define a variable _after_ it
		 * gets used in this expression; so we record the parser state before
		 * reading the first expression of a list constant. If it _is_ a real
		 * list constant, we'll see a comma next and we can begin the normal
		 * loop of counting arguments. */
		if (match(TOKEN_FOR)) {
			/* Roll back the earlier compiler */
			currentChunk()->count = chunkBefore;

			/* Compile list comprehension as a function */
			Compiler subcompiler;
			initCompiler(&subcompiler, current->type == TYPE_METHOD ? TYPE_METHOD : TYPE_FUNCTION);
			subcompiler.function->chunk.filename = subcompiler.enclosing->function->chunk.filename;

			beginScope();

			/* for i=0, */
			emitConstant(INTEGER_VAL(0));
			size_t indLoopCounter = current->localCount;
			addLocal(syntheticToken("__loop_count"));
			defineVariable(indLoopCounter);

			/* x in... */
			ssize_t loopInd = current->localCount;
			varDeclaration();
			defineVariable(loopInd);

			consume(TOKEN_IN, "Only iterator loops (for ... in ...) are allowed in list comprehensions.");

			beginScope();
			expression();
			endScope();

			/* iterable... */
			size_t indLoopIter = current->localCount;
			addLocal(syntheticToken("__loop_iter"));
			defineVariable(indLoopIter);

			/* Now try to call .__iter__ on the result to produce our iterator */
			KrkToken _iter = syntheticToken("__iter__");
			ssize_t ind = identifierConstant(&_iter);
			EMIT_CONSTANT_OP(OP_GET_PROPERTY, ind);
			emitBytes(OP_CALL, 0);

			/* Assign the resulting iterator to indLoopIter */
			EMIT_CONSTANT_OP(OP_SET_LOCAL, indLoopIter);

			/* Mark the start of the loop */
			int loopStart = currentChunk()->count;

			/* Call the iterator to get a value for our list */
			EMIT_CONSTANT_OP(OP_GET_LOCAL, indLoopIter);
			emitBytes(OP_CALL, 0);

			/* Assign the result to our loop index */
			EMIT_CONSTANT_OP(OP_SET_LOCAL, loopInd);

			/* Compare the iterator to the loop index;
			 * our iterators return themselves to say they are done;
			 * this allows them to return None without any issue,
			 * and there's no feasible way they can return themselves without
			 * our intended sentinel meaning, right? Surely? */
			EMIT_CONSTANT_OP(OP_GET_LOCAL, indLoopIter);
			emitBytes(OP_EQUAL, OP_NOT);
			int exitJump = emitJump(OP_JUMP_IF_FALSE);
			emitByte(OP_POP);

			/* Now we can rewind the scanner to have it parse the original
			 * expression that uses our iterated values! */
			KrkScanner scannerAfter = krk_tellScanner();
			Parser  parserAfter = parser;
			krk_rewindScanner(scannerBefore);
			parser = parserBefore;

			beginScope();
			expression();
			endScope();

			/* Then we can put the parser back to where it was at the end of
			 * the iterator expression and continue. */
			krk_rewindScanner(scannerAfter);
			parser = parserAfter;

			/* We keep a counter so we can keep track of how many arguments
			 * are on the stack, which we need in order to find the listOf()
			 * method above; having run the expression and generated an
			 * item which is now on the stack, increment the counter */
			EMIT_CONSTANT_OP(OP_INC, indLoopCounter);
			/* ... and loop back to the iterator call. */
			emitLoop(loopStart);

			/* Finally, at this point, we've seen the iterator produce itself
			 * and we're done receiving objects, so mark this instruction
			 * offset as the exit target for the OP_JUMP_IF_FALSE above */
			patchJump(exitJump);
			/* Parse the ] that indicates the end of the list comprehension */
			consume(TOKEN_RIGHT_SQUARE,"Expected ] at end of list expression.");
			/* Pop the last loop expression result which was already stored */
			emitByte(OP_POP);
			/* Pull in listOf from the global namespace */
			KrkToken listOf = syntheticToken("listOf");
			size_t indList = identifierConstant(&listOf);
			EMIT_CONSTANT_OP(OP_GET_GLOBAL, indList);
			/* And move it into where we were storing the loop iterator */
			EMIT_CONSTANT_OP(OP_SET_LOCAL, indLoopIter);
			/* (And pop it from the top of the stack) */
			emitByte(OP_POP);
			/* Then get the counter for our arg count */
			EMIT_CONSTANT_OP(OP_GET_LOCAL, indLoopCounter);
			/* And then call the native method which should be ^ that many items down */
			emitByte(OP_CALL_STACK);
			/* And return the result back to the original scope */
			emitByte(OP_RETURN);
			/* Now because we made a function we need to fill out its upvalues
			 * and write the closure call for it. */
			KrkFunction *subfunction = endCompiler();
			size_t indFunc = krk_addConstant(currentChunk(), OBJECT_VAL(subfunction));
			EMIT_CONSTANT_OP(OP_CLOSURE, indFunc);
			for (size_t i = 0; i < subfunction->upvalueCount; ++i) {
				emitByte(subcompiler.upvalues[i].isLocal ? 1 : 0);
				if (i > 255) {
					emitByte((subcompiler.upvalues[i].index >> 16) & 0xFF);
					emitByte((subcompiler.upvalues[i].index >> 8) & 0xFF);
				}
				emitByte((subcompiler.upvalues[i].index) & 0xFF);
			}
			freeCompiler(&subcompiler);

			/* And finally we can call the subfunction and get the result. */
			emitBytes(OP_CALL, 0);
		} else {
			size_t argCount = 1;
			while (match(TOKEN_COMMA)) {
				expression();
				argCount++;
			}
			consume(TOKEN_RIGHT_SQUARE,"Expected ] at end of list expression.");
			EMIT_CONSTANT_OP(OP_CALL, argCount);
		}
	} else {
		/* Empty list expression */
		advance();
		emitBytes(OP_CALL, 0);
	}
}

static void dict(int canAssign) {
	KrkToken dictOf = syntheticToken("dictOf");
	size_t ind = identifierConstant(&dictOf);
	EMIT_CONSTANT_OP(OP_GET_GLOBAL, ind);
	size_t argCount = 0;
	if (!check(TOKEN_RIGHT_BRACE)) {
		do {
			expression();
			consume(TOKEN_COLON, "Expect colon after dict key.");
			expression();
			argCount += 2;
		} while (match(TOKEN_COMMA));
	}
	consume(TOKEN_RIGHT_BRACE,"Expected } at end of dict expression.");
	EMIT_CONSTANT_OP(OP_CALL, argCount);
}

#define RULE(token, a, b, c) [token] = {# token, a, b, c}

ParseRule rules[] = {
	RULE(TOKEN_LEFT_PAREN,    grouping, call,   PREC_CALL),
	RULE(TOKEN_RIGHT_PAREN,   NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_LEFT_BRACE,    dict,     NULL,   PREC_NONE),
	RULE(TOKEN_RIGHT_BRACE,   NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_LEFT_SQUARE,   list,     get_,   PREC_CALL),
	RULE(TOKEN_RIGHT_SQUARE,  NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_COLON,         NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_COMMA,         NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_DOT,           NULL,     dot,    PREC_CALL),
	RULE(TOKEN_MINUS,         unary,    binary, PREC_TERM),
	RULE(TOKEN_PLUS,          NULL,     binary, PREC_TERM),
	RULE(TOKEN_SEMICOLON,     NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_SOLIDUS,       NULL,     binary, PREC_FACTOR),
	RULE(TOKEN_ASTERISK,      NULL,     binary, PREC_FACTOR),
	RULE(TOKEN_MODULO,        NULL,     binary, PREC_FACTOR),
	RULE(TOKEN_BANG,          unary,    NULL,   PREC_NONE),
	RULE(TOKEN_BANG_EQUAL,    NULL,     binary, PREC_EQUALITY),
	RULE(TOKEN_EQUAL,         NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_EQUAL_EQUAL,   NULL,     binary, PREC_EQUALITY),
	RULE(TOKEN_GREATER,       NULL,     binary, PREC_COMPARISON),
	RULE(TOKEN_GREATER_EQUAL, NULL,     binary, PREC_COMPARISON),
	RULE(TOKEN_LESS,          NULL,     binary, PREC_COMPARISON),
	RULE(TOKEN_LESS_EQUAL,    NULL,     binary, PREC_COMPARISON),
	RULE(TOKEN_IDENTIFIER,    variable, NULL,   PREC_NONE),
	RULE(TOKEN_STRING,        string,   NULL,   PREC_NONE),
	RULE(TOKEN_BIG_STRING,    string,   NULL,   PREC_NONE),
	RULE(TOKEN_NUMBER,        number,   NULL,   PREC_NONE),
	RULE(TOKEN_AND,           NULL,     and_,   PREC_AND),
	RULE(TOKEN_CLASS,         NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_ELSE,          NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_FALSE,         literal,  NULL,   PREC_NONE),
	RULE(TOKEN_FOR,           NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_DEF,           NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_IF,            NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_IN,            NULL,     in_,    PREC_COMPARISON),
	RULE(TOKEN_LET,           NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_NONE,          literal,  NULL,   PREC_NONE),
	RULE(TOKEN_NOT,           unary,    NULL,   PREC_NONE),
	RULE(TOKEN_OR,            NULL,     or_,    PREC_OR),
	RULE(TOKEN_PRINT,         NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_RETURN,        NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_SELF,          self,     NULL,   PREC_NONE),
	RULE(TOKEN_SUPER,         super_,   NULL,   PREC_NONE),
	RULE(TOKEN_TRUE,          literal,  NULL,   PREC_NONE),
	RULE(TOKEN_WHILE,         NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_BREAK,         NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_CONTINUE,      NULL,     NULL,   PREC_NONE),

	RULE(TOKEN_AT,            NULL,     NULL,   PREC_NONE),

	RULE(TOKEN_TILDE,         unary,    NULL,   PREC_NONE),
	RULE(TOKEN_PIPE,          NULL,     binary, PREC_BITOR),
	RULE(TOKEN_CARET,         NULL,     binary, PREC_BITXOR),
	RULE(TOKEN_AMPERSAND,     NULL,     binary, PREC_BITAND),
	RULE(TOKEN_LEFT_SHIFT,    NULL,     binary, PREC_SHIFT),
	RULE(TOKEN_RIGHT_SHIFT,   NULL,     binary, PREC_SHIFT),

	RULE(TOKEN_PLUS_EQUAL,    NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_MINUS_EQUAL,   NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_PLUS_PLUS,     NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_MINUS_MINUS,   NULL,     NULL,   PREC_NONE),

	/* This is going to get interesting */
	RULE(TOKEN_INDENTATION,   NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_ERROR,         NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_EOL,           NULL,     NULL,   PREC_NONE),
	RULE(TOKEN_EOF,           NULL,     NULL,   PREC_NONE),
};

static void parsePrecedence(Precedence precedence) {
	advance();
	ParseFn prefixRule = getRule(parser.previous.type)->prefix;
	if (prefixRule == NULL) {
		errorAtCurrent("Unexpected token.");
		return;
	}
	int canAssign = precedence <= PREC_ASSIGNMENT;
	prefixRule(canAssign);
	while (precedence <= getRule(parser.current.type)->precedence) {
		advance();
		ParseFn infixRule = getRule(parser.previous.type)->infix;
		infixRule(canAssign);
	}

	if (canAssign && matchAssignment()) {
		error("invalid assignment target");
	}
}

static ssize_t identifierConstant(KrkToken * name) {
	return krk_addConstant(currentChunk(), OBJECT_VAL(krk_copyString(name->start, name->length)));
}

static ssize_t resolveLocal(Compiler * compiler, KrkToken * name) {
	for (ssize_t i = compiler->localCount - 1; i >= 0; i--) {
		Local * local = &compiler->locals[i];
		if (identifiersEqual(name, &local->name)) {
			if (local->depth == -1) {
				error("Can not initialize value recursively (are you shadowing something?)");
			}
			return i;
		}
	}
	return -1;
}

static void addLocal(KrkToken name) {
	if (current->localCount + 1 > current->localsSpace) {
		size_t old = current->localsSpace;
		current->localsSpace = GROW_CAPACITY(old);
		current->locals = GROW_ARRAY(Local,current->locals,old,current->localsSpace);
	}
	Local * local = &current->locals[current->localCount++];
	local->name = name;
	local->depth = -1;
	local->isCaptured = 0;
}

static void declareVariable() {
	if (current->scopeDepth == 0) return;
	KrkToken * name = &parser.previous;
	/* Detect duplicate definition */
	for (ssize_t i = current->localCount - 1; i >= 0; i--) {
		Local * local = &current->locals[i];
		if (local->depth != -1 && local->depth < (ssize_t)current->scopeDepth) break;
		if (identifiersEqual(name, &local->name)) {
			error("Duplicate definition");
			__asm__("int $3");
		}
	}
	addLocal(*name);
}

static ssize_t parseVariable(const char * errorMessage) {
	consume(TOKEN_IDENTIFIER, errorMessage);

	declareVariable();
	if (current->scopeDepth > 0) return 0;

	return identifierConstant(&parser.previous);
}

static void defineVariable(size_t global) {
	if (current->scopeDepth > 0) {
		markInitialized();
		return;
	}

	EMIT_CONSTANT_OP(OP_DEFINE_GLOBAL, global);
}

static void call(int canAssign) {
	size_t argCount = 0, specialArgs = 0, keywordArgs = 0, seenKeywordUnpacking = 0;
	if (!check(TOKEN_RIGHT_PAREN)) {
		do {
			if (match(TOKEN_ASTERISK)) {
				specialArgs++;
				if (match(TOKEN_ASTERISK)) {
					seenKeywordUnpacking = 1;
					emitBytes(OP_EXPAND_ARGS, 2); /* Outputs something special */
					expression(); /* Expect dict */
					continue;
				} else {
					if (seenKeywordUnpacking) {
						error("Iterable expansion follows keyword argument unpacking.");
						return;
					}
					emitBytes(OP_EXPAND_ARGS, 1); /* outputs something special */
					expression();
					continue;
				}
			}
			if (match(TOKEN_IDENTIFIER)) {
				KrkToken argName = parser.previous;
				if (check(TOKEN_EQUAL)) {
					/* This is a keyword argument. */
					advance();
					/* Output the name */
					size_t ind = identifierConstant(&argName);
					EMIT_CONSTANT_OP(OP_CONSTANT, ind);
					expression();
					keywordArgs++;
					specialArgs++;
					continue;
				} else {
					/*
					 * This is a regular argument that happened to start with an identifier,
					 * roll it back so we can process it that way.
					 */
					krk_ungetToken(parser.current);
					parser.current = argName;
				}
			} else if (seenKeywordUnpacking) {
				error("positional argument follows keyword argument unpacking");
				return;
			} else if (keywordArgs) {
				error("Positional argument follows keyword argument");
				return;
			} else if (specialArgs) {
				emitBytes(OP_EXPAND_ARGS, 0);
				expression();
				specialArgs++;
				continue;
			}
			expression();
			argCount++;
		} while (match(TOKEN_COMMA));
	}
	consume(TOKEN_RIGHT_PAREN, "Expected ')' after arguments.");
	if (specialArgs) {
		/*
		 * Creates a sentinel at the top of the stack to tell the CALL instruction
		 * how many keyword arguments are at the top of the stack. This value
		 * triggers special handling in the CALL that processes the keyword arguments,
		 * which is relatively slow, so only use keyword arguments if you have to!
		 */
		EMIT_CONSTANT_OP(OP_KWARGS, specialArgs);
		/*
		 * We added two elements - name and value - for each keyword arg,
		 * plus the sentinel object that will show up at the end after the
		 * OP_KWARGS instruction complets, so make sure we have the
		 * right depth into the stack when we execute CALL
		 */
		argCount += 1 /* for the sentinel */ + 2 * specialArgs;
	}
	EMIT_CONSTANT_OP(OP_CALL, argCount);
}

static void and_(int canAssign) {
	int endJump = emitJump(OP_JUMP_IF_FALSE);
	emitByte(OP_POP);
	parsePrecedence(PREC_AND);
	patchJump(endJump);
}

static void or_(int canAssign) {
	int endJump = emitJump(OP_JUMP_IF_TRUE);
	emitByte(OP_POP);
	parsePrecedence(PREC_OR);
	patchJump(endJump);
}

static ParseRule * getRule(KrkTokenType type) {
	return &rules[type];
}

KrkFunction * krk_compile(const char * src, int newScope, char * fileName) {
	krk_initScanner(src);
	Compiler compiler;
	initCompiler(&compiler, TYPE_MODULE);
	compiler.function->chunk.filename = krk_copyString(fileName, strlen(fileName));

	if (newScope) beginScope();

	parser.hadError = 0;
	parser.panicMode = 0;

	advance();

	while (!match(TOKEN_EOF)) {
		declaration();
		if (check(TOKEN_EOL) || check(TOKEN_INDENTATION) || check(TOKEN_EOF)) {
			/* There's probably already and error... */
			advance();
		}
	}

	KrkFunction * function = endCompiler();
	freeCompiler(&compiler);
	return parser.hadError ? NULL : function;
}

void krk_markCompilerRoots() {
	Compiler * compiler = current;
	while (compiler != NULL) {
		krk_markObject((KrkObj*)compiler->function);
		compiler = compiler->enclosing;
	}
}