odin-lang.Odin/src/parser.cpp

struct AstNode;
struct Scope;

enum ParseFileError {
	ParseFile_None,

	ParseFile_WrongExtension,
	ParseFile_InvalidFile,
	ParseFile_EmptyFile,
	ParseFile_Permission,
	ParseFile_NotFound,
	ParseFile_InvalidToken,

	ParseFile_Count,
};

typedef gbArray(AstNode *) AstNodeArray;

struct AstFile {
	gbArena        arena;
	Tokenizer      tokenizer;
	gbArray(Token) tokens;
	Token *        cursor; // NOTE(bill): Current token, easy to peek forward and backwards if needed

	// >= 0: In Expression
	// <  0: In Control Clause
	// NOTE(bill): Used to prevent type literals in control clauses
	isize expr_level;

	AstNodeArray decls;
	b32 is_global_scope;

	AstNode *curr_proc;
	isize    scope_level;
	Scope *  scope; // NOTE(bill): Created in checker

	ErrorCollector error_collector;

	// TODO(bill): Error recovery
	// NOTE(bill): Error recovery
#define PARSER_MAX_FIX_COUNT 6
	isize    fix_count;
	TokenPos fix_prev_pos;
};

struct ImportedFile {
	String path;
	TokenPos pos; // #import
};

struct Parser {
	String init_fullpath;
	gbArray(AstFile) files;
	gbArray(ImportedFile) imports;
	gbArray(String) libraries;
	gbArray(String) system_libraries;
	isize load_index;
	isize total_token_count;
};

enum DeclKind {
	Declaration_Invalid,
	Declaration_Mutable,
	Declaration_Immutable,
	Declaration_Count,
};

enum ProcTag {
	ProcTag_bounds_check    = GB_BIT(0),
	ProcTag_no_bounds_check = GB_BIT(1),
	ProcTag_foreign         = GB_BIT(2),
	ProcTag_inline          = GB_BIT(3),
	ProcTag_no_inline       = GB_BIT(4),
};

enum VarDeclTag {
	VarDeclTag_thread_local = GB_BIT(0),
};


enum TypeFlag : u32 {
	TypeFlag_thread_local = GB_BIT(0),
	TypeFlag_volatile     = GB_BIT(1),
	TypeFlag_atomic       = GB_BIT(2),

};

enum StmtStateFlag : u32 {
	StmtStateFlag_bounds_check    = GB_BIT(0),
	StmtStateFlag_no_bounds_check = GB_BIT(1),
};


enum CallExprKind {
	CallExpr_Prefix,  // call(...)
	CallExpr_Postfix, // a'call
	CallExpr_Infix,   // a ''call b
};

AstNodeArray make_ast_node_array(AstFile *f) {
	AstNodeArray a;
	gb_array_init(a, gb_arena_allocator(&f->arena));
	GB_ASSERT(a != NULL);
	return a;
}


#define AST_NODE_KINDS \
	AST_NODE_KIND(Invalid,  "invalid node",  struct{}) \
	AST_NODE_KIND(BasicLit, "basic literal", Token) \
	AST_NODE_KIND(Ident,    "identifier",    Token) \
	AST_NODE_KIND(Ellipsis, "ellipsis", struct { \
		Token token; \
		AstNode *expr; \
	}) \
	AST_NODE_KIND(ProcLit, "procedure literal", struct { \
		AstNode *type; \
		AstNode *body; \
		u64 tags;      \
	}) \
	AST_NODE_KIND(CompoundLit, "compound literal", struct { \
		AstNode *type; \
		AstNodeArray elems; \
		Token open, close; \
	}) \
AST_NODE_KIND(_ExprBegin,  "",  struct{}) \
	AST_NODE_KIND(BadExpr,      "bad expression",         struct { Token begin, end; }) \
	AST_NODE_KIND(TagExpr,      "tag expression",         struct { Token token, name; AstNode *expr; }) \
	AST_NODE_KIND(UnaryExpr,    "unary expression",       struct { Token op; AstNode *expr; }) \
	AST_NODE_KIND(BinaryExpr,   "binary expression",      struct { Token op; AstNode *left, *right; } ) \
	AST_NODE_KIND(ParenExpr,    "parentheses expression", struct { AstNode *expr; Token open, close; }) \
	AST_NODE_KIND(SelectorExpr, "selector expression",    struct { Token token; AstNode *expr, *selector; }) \
	AST_NODE_KIND(IndexExpr,    "index expression",       struct { AstNode *expr, *index; Token open, close; }) \
	AST_NODE_KIND(DerefExpr,    "dereference expression", struct { Token op; AstNode *expr; }) \
	AST_NODE_KIND(CallExpr,     "call expression", struct { \
		AstNode *proc; \
		gbArray(AstNode *) args; \
		Token open, close; \
		Token ellipsis; \
		CallExprKind kind; \
	}) \
	AST_NODE_KIND(SliceExpr, "slice expression", struct { \
		AstNode *expr; \
		Token open, close; \
		AstNode *low, *high, *max; \
		b32 triple_indexed; \
	}) \
	AST_NODE_KIND(FieldValue, "field value", struct { Token eq; AstNode *field, *value; }) \
AST_NODE_KIND(_ExprEnd,       "", struct{}) \
AST_NODE_KIND(_StmtBegin,     "", struct{}) \
	AST_NODE_KIND(BadStmt,    "bad statement",                 struct { Token begin, end; }) \
	AST_NODE_KIND(EmptyStmt,  "empty statement",               struct { Token token; }) \
	AST_NODE_KIND(ExprStmt,   "expression statement",          struct { AstNode *expr; } ) \
	AST_NODE_KIND(IncDecStmt, "increment/decrement statement", struct { Token op; AstNode *expr; }) \
	AST_NODE_KIND(TagStmt,    "tag statement", struct { \
		Token token; \
		Token name; \
		AstNode *stmt; \
	}) \
	AST_NODE_KIND(AssignStmt, "assign statement", struct { \
		Token op; \
		AstNodeArray lhs, rhs; \
	}) \
AST_NODE_KIND(_ComplexStmtBegin, "", struct{}) \
	AST_NODE_KIND(BlockStmt, "block statement", struct { \
		AstNodeArray stmts; \
		Token open, close; \
	}) \
	AST_NODE_KIND(IfStmt, "if statement", struct { \
		Token token; \
		AstNode *init; \
		AstNode *cond; \
		AstNode *body; \
		AstNode *else_stmt; \
	}) \
	AST_NODE_KIND(ReturnStmt, "return statement", struct { \
		Token token; \
		AstNodeArray results; \
	}) \
	AST_NODE_KIND(ForStmt, "for statement", struct { \
		Token token; \
		AstNode *init, *cond, *post; \
		AstNode *body; \
	}) \
	AST_NODE_KIND(CaseClause, "case clause", struct { \
		Token token; \
		AstNodeArray list, stmts; \
	}) \
	AST_NODE_KIND(MatchStmt, "match statement", struct { \
		Token token; \
		AstNode *init, *tag; \
		AstNode *body; \
	}) \
	AST_NODE_KIND(TypeMatchStmt, "type match statement", struct { \
		Token token; \
		AstNode *tag, *var; \
		AstNode *body; \
	}) \
	AST_NODE_KIND(DeferStmt,  "defer statement",  struct { Token token; AstNode *stmt; }) \
	AST_NODE_KIND(BranchStmt, "branch statement", struct { Token token; }) \
	AST_NODE_KIND(UsingStmt,  "using statement",  struct { Token token; AstNode *node; }) \
	AST_NODE_KIND(AsmOperand, "assembly operand", struct { \
		Token string; \
		AstNode *operand; \
	}) \
	AST_NODE_KIND(AsmStmt,    "assembly statement", struct { \
		Token token; \
		b32 is_volatile; \
		Token open, close; \
		Token code_string; \
		AstNode *output_list; \
		AstNode *input_list; \
		AstNode *clobber_list; \
		isize output_count, input_count, clobber_count; \
	}) \
\
AST_NODE_KIND(_ComplexStmtEnd, "", struct{}) \
AST_NODE_KIND(_StmtEnd,        "", struct{}) \
AST_NODE_KIND(_DeclBegin,      "", struct{}) \
	AST_NODE_KIND(BadDecl,  "bad declaration", struct { Token begin, end; }) \
	AST_NODE_KIND(VarDecl,  "variable declaration", struct { \
			DeclKind kind; \
			u32      tags; \
			b32      is_using; \
			AstNodeArray names; \
			AstNode *type; \
			AstNodeArray values; \
		}) \
	AST_NODE_KIND(ProcDecl, "procedure declaration", struct { \
			AstNode *name;        \
			AstNode *type;        \
			AstNode *body;        \
			u64     tags;         \
			String  foreign_name; \
		}) \
	AST_NODE_KIND(TypeDecl,   "type declaration",   struct { Token token; AstNode *name, *type; }) \
	AST_NODE_KIND(ImportDecl, "import declaration", struct { \
		Token token, relpath; \
		String fullpath;      \
		Token import_name;    \
	}) \
	AST_NODE_KIND(ForeignSystemLibrary, "foreign system library", struct { Token token, filepath; }) \
AST_NODE_KIND(_DeclEnd,   "", struct{}) \
AST_NODE_KIND(_TypeBegin, "", struct{}) \
	AST_NODE_KIND(Field, "field", struct { \
		AstNodeArray names; \
		AstNode *type; \
		b32 is_using; \
	}) \
	AST_NODE_KIND(ProcType, "procedure type", struct { \
		Token token;          \
		AstNodeArray params;  \
		AstNodeArray results; \
	}) \
	AST_NODE_KIND(PointerType, "pointer type", struct { \
		Token token; \
		AstNode *type; \
	}) \
	AST_NODE_KIND(ArrayType, "array type", struct { \
		Token token; \
		AstNode *count; \
		AstNode *elem; \
	}) \
	AST_NODE_KIND(VectorType, "vector type", struct { \
		Token token; \
		AstNode *count; \
		AstNode *elem; \
	}) \
	AST_NODE_KIND(StructType, "struct type", struct { \
		Token token; \
		AstNodeArray decls; \
		isize decl_count; \
		b32 is_packed; \
		b32 is_ordered; \
	}) \
	AST_NODE_KIND(UnionType, "union type", struct { \
		Token token; \
		AstNodeArray decls; \
		isize decl_count; \
	}) \
	AST_NODE_KIND(RawUnionType, "raw union type", struct { \
		Token token; \
		AstNodeArray decls; \
		isize decl_count; \
	}) \
	AST_NODE_KIND(EnumType, "enum type", struct { \
		Token token; \
		AstNode *base_type; \
		AstNodeArray fields; \
	}) \
AST_NODE_KIND(_TypeEnd,  "", struct{}) \
	AST_NODE_KIND(Count, "", struct{})

enum AstNodeKind {
#define AST_NODE_KIND(_kind_name_, ...) GB_JOIN2(AstNode_, _kind_name_),
	AST_NODE_KINDS
#undef AST_NODE_KIND
};

String const ast_node_strings[] = {
#define AST_NODE_KIND(_kind_name_, name, ...) {cast(u8 *)name, gb_size_of(name)-1},
	AST_NODE_KINDS
#undef AST_NODE_KIND
};

struct AstNode {
	AstNodeKind kind;
	// AstNode *prev, *next; // NOTE(bill): allow for Linked list
	u32 type_flags;
	u32 stmt_state_flags;
	union {
#define AST_NODE_KIND(_kind_name_, name, ...) __VA_ARGS__ _kind_name_;
	AST_NODE_KINDS
#undef AST_NODE_KIND
	};
};


#define ast_node(n_, Kind_, node_) auto *n_ = &(node_)->Kind_; GB_ASSERT((node_)->kind == GB_JOIN2(AstNode_, Kind_))
#define case_ast_node(n_, Kind_, node_) case GB_JOIN2(AstNode_, Kind_): { ast_node(n_, Kind_, node_);
#define case_end } break;




gb_inline b32 is_ast_node_expr(AstNode *node) {
	return gb_is_between(node->kind, AstNode__ExprBegin+1, AstNode__ExprEnd-1);
}
gb_inline b32 is_ast_node_stmt(AstNode *node) {
	return gb_is_between(node->kind, AstNode__StmtBegin+1, AstNode__StmtEnd-1);
}
gb_inline b32 is_ast_node_complex_stmt(AstNode *node) {
	return gb_is_between(node->kind, AstNode__ComplexStmtBegin+1, AstNode__ComplexStmtEnd-1);
}
gb_inline b32 is_ast_node_decl(AstNode *node) {
	return gb_is_between(node->kind, AstNode__DeclBegin+1, AstNode__DeclEnd-1);
}
gb_inline b32 is_ast_node_type(AstNode *node) {
	return gb_is_between(node->kind, AstNode__TypeBegin+1, AstNode__TypeEnd-1);
}


Token ast_node_token(AstNode *node) {
	switch (node->kind) {
	case AstNode_BasicLit:
		return node->BasicLit;
	case AstNode_Ident:
		return node->Ident;
	case AstNode_ProcLit:
		return ast_node_token(node->ProcLit.type);
	case AstNode_CompoundLit:
		return ast_node_token(node->CompoundLit.type);
	case AstNode_TagExpr:
		return node->TagExpr.token;
	case AstNode_BadExpr:
		return node->BadExpr.begin;
	case AstNode_UnaryExpr:
		return node->UnaryExpr.op;
	case AstNode_BinaryExpr:
		return ast_node_token(node->BinaryExpr.left);
	case AstNode_ParenExpr:
		return node->ParenExpr.open;
	case AstNode_CallExpr:
		return ast_node_token(node->CallExpr.proc);
	case AstNode_SelectorExpr:
		return ast_node_token(node->SelectorExpr.selector);
	case AstNode_IndexExpr:
		return node->IndexExpr.open;
	case AstNode_SliceExpr:
		return node->SliceExpr.open;
	case AstNode_Ellipsis:
		return node->Ellipsis.token;
	case AstNode_FieldValue:
		return node->FieldValue.eq;
	case AstNode_DerefExpr:
		return node->DerefExpr.op;
	case AstNode_BadStmt:
		return node->BadStmt.begin;
	case AstNode_EmptyStmt:
		return node->EmptyStmt.token;
	case AstNode_ExprStmt:
		return ast_node_token(node->ExprStmt.expr);
	case AstNode_TagStmt:
		return node->TagStmt.token;
	case AstNode_IncDecStmt:
		return node->IncDecStmt.op;
	case AstNode_AssignStmt:
		return node->AssignStmt.op;
	case AstNode_BlockStmt:
		return node->BlockStmt.open;
	case AstNode_IfStmt:
		return node->IfStmt.token;
	case AstNode_ReturnStmt:
		return node->ReturnStmt.token;
	case AstNode_ForStmt:
		return node->ForStmt.token;
	case AstNode_MatchStmt:
		return node->MatchStmt.token;
	case AstNode_CaseClause:
		return node->CaseClause.token;
	case AstNode_DeferStmt:
		return node->DeferStmt.token;
	case AstNode_BranchStmt:
		return node->BranchStmt.token;
	case AstNode_UsingStmt:
		return node->UsingStmt.token;
	case AstNode_AsmStmt:
		return node->AsmStmt.token;
	case AstNode_BadDecl:
		return node->BadDecl.begin;
	case AstNode_VarDecl:
		return ast_node_token(node->VarDecl.names[0]);
	case AstNode_ProcDecl:
		return node->ProcDecl.name->Ident;
	case AstNode_TypeDecl:
		return node->TypeDecl.token;
	case AstNode_ImportDecl:
		return node->ImportDecl.token;
	case AstNode_ForeignSystemLibrary:
		return node->ForeignSystemLibrary.token;
	case AstNode_Field: {
		if (node->Field.names)
			return ast_node_token(node->Field.names[0]);
		else
			return ast_node_token(node->Field.type);
	}
	case AstNode_ProcType:
		return node->ProcType.token;
	case AstNode_PointerType:
		return node->PointerType.token;
	case AstNode_ArrayType:
		return node->ArrayType.token;
	case AstNode_VectorType:
		return node->VectorType.token;
	case AstNode_StructType:
		return node->StructType.token;
	case AstNode_UnionType:
		return node->UnionType.token;
	case AstNode_RawUnionType:
		return node->RawUnionType.token;
	case AstNode_EnumType:
		return node->EnumType.token;
	}

	return empty_token;
}

HashKey hash_token(Token t) {
	return hash_string(t.string);
}

#define ast_file_err(f, token, fmt, ...) ast_file_err_(f, __FUNCTION__, token, fmt, ##__VA_ARGS__)
void ast_file_err_(AstFile *file, char *function, Token token, char *fmt, ...) {
	// NOTE(bill): Duplicate error, skip it
	if (!token_pos_are_equal(file->error_collector.prev, token.pos)) {
		va_list va;

		file->error_collector.prev = token.pos;

	#if 0
		gb_printf_err("%s()\n", function);
	#endif
		va_start(va, fmt);
		gb_printf_err("%.*s(%td:%td) Syntax error: %s\n",
		              LIT(token.pos.file), token.pos.line, token.pos.column,
		              gb_bprintf_va(fmt, va));
		va_end(va);
	}
	file->error_collector.count++;
}


// NOTE(bill): And this below is why is I/we need a new language! Discriminated unions are a pain in C/C++
gb_inline AstNode *make_node(AstFile *f, AstNodeKind kind) {
	gbArena *arena = &f->arena;
	if (gb_arena_size_remaining(arena, GB_DEFAULT_MEMORY_ALIGNMENT) <= gb_size_of(AstNode)) {
		// NOTE(bill): If a syntax error is so bad, just quit!
		gb_exit(1);
	}
	AstNode *node = gb_alloc_item(gb_arena_allocator(arena), AstNode);
	node->kind = kind;
	return node;
}

gb_inline AstNode *make_bad_expr(AstFile *f, Token begin, Token end) {
	AstNode *result = make_node(f, AstNode_BadExpr);
	result->BadExpr.begin = begin;
	result->BadExpr.end   = end;
	return result;
}

gb_inline AstNode *make_tag_expr(AstFile *f, Token token, Token name, AstNode *expr) {
	AstNode *result = make_node(f, AstNode_TagExpr);
	result->TagExpr.token = token;
	result->TagExpr.name = name;
	result->TagExpr.expr = expr;
	return result;
}

gb_inline AstNode *make_tag_stmt(AstFile *f, Token token, Token name, AstNode *stmt) {
	AstNode *result = make_node(f, AstNode_TagStmt);
	result->TagStmt.token = token;
	result->TagStmt.name = name;
	result->TagStmt.stmt = stmt;
	return result;
}

gb_inline AstNode *make_unary_expr(AstFile *f, Token op, AstNode *expr) {
	AstNode *result = make_node(f, AstNode_UnaryExpr);
	result->UnaryExpr.op = op;
	result->UnaryExpr.expr = expr;
	return result;
}

gb_inline AstNode *make_binary_expr(AstFile *f, Token op, AstNode *left, AstNode *right) {
	AstNode *result = make_node(f, AstNode_BinaryExpr);

	if (left == NULL) {
		ast_file_err(f, op, "No lhs expression for binary expression `%.*s`", LIT(op.string));
		left = make_bad_expr(f, op, op);
	}
	if (right == NULL) {
		ast_file_err(f, op, "No rhs expression for binary expression `%.*s`", LIT(op.string));
		right = make_bad_expr(f, op, op);
	}

	result->BinaryExpr.op = op;
	result->BinaryExpr.left = left;
	result->BinaryExpr.right = right;

	return result;
}

gb_inline AstNode *make_paren_expr(AstFile *f, AstNode *expr, Token open, Token close) {
	AstNode *result = make_node(f, AstNode_ParenExpr);
	result->ParenExpr.expr = expr;
	result->ParenExpr.open = open;
	result->ParenExpr.close = close;
	return result;
}

gb_inline AstNode *make_call_expr(AstFile *f, AstNode *proc, gbArray(AstNode *)args, Token open, Token close, Token ellipsis) {
	AstNode *result = make_node(f, AstNode_CallExpr);
	result->CallExpr.proc = proc;
	result->CallExpr.args = args;
	result->CallExpr.open     = open;
	result->CallExpr.close    = close;
	result->CallExpr.ellipsis = ellipsis;
	return result;
}

gb_inline AstNode *make_selector_expr(AstFile *f, Token token, AstNode *expr, AstNode *selector) {
	AstNode *result = make_node(f, AstNode_SelectorExpr);
	result->SelectorExpr.expr = expr;
	result->SelectorExpr.selector = selector;
	return result;
}

gb_inline AstNode *make_index_expr(AstFile *f, AstNode *expr, AstNode *index, Token open, Token close) {
	AstNode *result = make_node(f, AstNode_IndexExpr);
	result->IndexExpr.expr = expr;
	result->IndexExpr.index = index;
	result->IndexExpr.open = open;
	result->IndexExpr.close = close;
	return result;
}


gb_inline AstNode *make_slice_expr(AstFile *f, AstNode *expr, Token open, Token close, AstNode *low, AstNode *high, AstNode *max, b32 triple_indexed) {
	AstNode *result = make_node(f, AstNode_SliceExpr);
	result->SliceExpr.expr = expr;
	result->SliceExpr.open = open;
	result->SliceExpr.close = close;
	result->SliceExpr.low = low;
	result->SliceExpr.high = high;
	result->SliceExpr.max = max;
	result->SliceExpr.triple_indexed = triple_indexed;
	return result;
}

gb_inline AstNode *make_deref_expr(AstFile *f, AstNode *expr, Token op) {
	AstNode *result = make_node(f, AstNode_DerefExpr);
	result->DerefExpr.expr = expr;
	result->DerefExpr.op = op;
	return result;
}


gb_inline AstNode *make_basic_lit(AstFile *f, Token basic_lit) {
	AstNode *result = make_node(f, AstNode_BasicLit);
	result->BasicLit = basic_lit;
	return result;
}

gb_inline AstNode *make_ident(AstFile *f, Token token) {
	AstNode *result = make_node(f, AstNode_Ident);
	result->Ident = token;
	return result;
}

gb_inline AstNode *make_ellipsis(AstFile *f, Token token, AstNode *expr) {
	AstNode *result = make_node(f, AstNode_Ellipsis);
	result->Ellipsis.token = token;
	result->Ellipsis.expr = expr;
	return result;
}


gb_inline AstNode *make_proc_lit(AstFile *f, AstNode *type, AstNode *body, u64 tags) {
	AstNode *result = make_node(f, AstNode_ProcLit);
	result->ProcLit.type = type;
	result->ProcLit.body = body;
	result->ProcLit.tags = tags;
	return result;
}

gb_inline AstNode *make_field_value(AstFile *f, AstNode *field, AstNode *value, Token eq) {
	AstNode *result = make_node(f, AstNode_FieldValue);
	result->FieldValue.field = field;
	result->FieldValue.value = value;
	result->FieldValue.eq = eq;
	return result;
}

gb_inline AstNode *make_compound_lit(AstFile *f, AstNode *type, AstNodeArray elems, Token open, Token close) {
	AstNode *result = make_node(f, AstNode_CompoundLit);
	result->CompoundLit.type = type;
	result->CompoundLit.elems = elems;
	result->CompoundLit.open = open;
	result->CompoundLit.close = close;
	return result;
}

gb_inline AstNode *make_bad_stmt(AstFile *f, Token begin, Token end) {
	AstNode *result = make_node(f, AstNode_BadStmt);
	result->BadStmt.begin = begin;
	result->BadStmt.end   = end;
	return result;
}

gb_inline AstNode *make_empty_stmt(AstFile *f, Token token) {
	AstNode *result = make_node(f, AstNode_EmptyStmt);
	result->EmptyStmt.token = token;
	return result;
}

gb_inline AstNode *make_expr_stmt(AstFile *f, AstNode *expr) {
	AstNode *result = make_node(f, AstNode_ExprStmt);
	result->ExprStmt.expr = expr;
	return result;
}

gb_inline AstNode *make_inc_dec_stmt(AstFile *f, Token op, AstNode *expr) {
	AstNode *result = make_node(f, AstNode_IncDecStmt);
	result->IncDecStmt.op = op;
	result->IncDecStmt.expr = expr;
	return result;
}

gb_inline AstNode *make_assign_stmt(AstFile *f, Token op, AstNodeArray lhs, AstNodeArray rhs) {
	AstNode *result = make_node(f, AstNode_AssignStmt);
	result->AssignStmt.op = op;
	result->AssignStmt.lhs = lhs;
	result->AssignStmt.rhs = rhs;
	return result;
}

gb_inline AstNode *make_block_stmt(AstFile *f, AstNodeArray stmts, Token open, Token close) {
	AstNode *result = make_node(f, AstNode_BlockStmt);
	result->BlockStmt.stmts = stmts;
	result->BlockStmt.open = open;
	result->BlockStmt.close = close;
	return result;
}

gb_inline AstNode *make_if_stmt(AstFile *f, Token token, AstNode *init, AstNode *cond, AstNode *body, AstNode *else_stmt) {
	AstNode *result = make_node(f, AstNode_IfStmt);
	result->IfStmt.token = token;
	result->IfStmt.init = init;
	result->IfStmt.cond = cond;
	result->IfStmt.body = body;
	result->IfStmt.else_stmt = else_stmt;
	return result;
}

gb_inline AstNode *make_return_stmt(AstFile *f, Token token, AstNodeArray results) {
	AstNode *result = make_node(f, AstNode_ReturnStmt);
	result->ReturnStmt.token = token;
	result->ReturnStmt.results = results;
	return result;
}

gb_inline AstNode *make_for_stmt(AstFile *f, Token token, AstNode *init, AstNode *cond, AstNode *post, AstNode *body) {
	AstNode *result = make_node(f, AstNode_ForStmt);
	result->ForStmt.token = token;
	result->ForStmt.init  = init;
	result->ForStmt.cond  = cond;
	result->ForStmt.post  = post;
	result->ForStmt.body  = body;
	return result;
}


gb_inline AstNode *make_match_stmt(AstFile *f, Token token, AstNode *init, AstNode *tag, AstNode *body) {
	AstNode *result = make_node(f, AstNode_MatchStmt);
	result->MatchStmt.token = token;
	result->MatchStmt.init  = init;
	result->MatchStmt.tag   = tag;
	result->MatchStmt.body  = body;
	return result;
}


gb_inline AstNode *make_type_match_stmt(AstFile *f, Token token, AstNode *tag, AstNode *var, AstNode *body) {
	AstNode *result = make_node(f, AstNode_TypeMatchStmt);
	result->TypeMatchStmt.token = token;
	result->TypeMatchStmt.tag   = tag;
	result->TypeMatchStmt.var   = var;
	result->TypeMatchStmt.body  = body;
	return result;
}

gb_inline AstNode *make_case_clause(AstFile *f, Token token, AstNodeArray list, AstNodeArray stmts) {
	AstNode *result = make_node(f, AstNode_CaseClause);
	result->CaseClause.token = token;
	result->CaseClause.list  = list;
	result->CaseClause.stmts = stmts;
	return result;
}


gb_inline AstNode *make_defer_stmt(AstFile *f, Token token, AstNode *stmt) {
	AstNode *result = make_node(f, AstNode_DeferStmt);
	result->DeferStmt.token = token;
	result->DeferStmt.stmt = stmt;
	return result;
}

gb_inline AstNode *make_branch_stmt(AstFile *f, Token token) {
	AstNode *result = make_node(f, AstNode_BranchStmt);
	result->BranchStmt.token = token;
	return result;
}

gb_inline AstNode *make_using_stmt(AstFile *f, Token token, AstNode *node) {
	AstNode *result = make_node(f, AstNode_UsingStmt);
	result->UsingStmt.token = token;
	result->UsingStmt.node  = node;
	return result;
}

gb_inline AstNode *make_asm_operand(AstFile *f, Token string, AstNode *operand) {
	AstNode *result = make_node(f, AstNode_AsmOperand);
	result->AsmOperand.string  = string;
	result->AsmOperand.operand = operand;
	return result;

}

gb_inline AstNode *make_asm_stmt(AstFile *f, Token token, b32 is_volatile, Token open, Token close, Token code_string,
                                 AstNode *output_list, AstNode *input_list, AstNode *clobber_list,
                                 isize output_count, isize input_count, isize clobber_count) {
	AstNode *result = make_node(f, AstNode_AsmStmt);
	result->AsmStmt.token = token;
	result->AsmStmt.is_volatile = is_volatile;
	result->AsmStmt.open  = open;
	result->AsmStmt.close = close;
	result->AsmStmt.code_string = code_string;
	result->AsmStmt.output_list = output_list;
	result->AsmStmt.input_list = input_list;
	result->AsmStmt.clobber_list = clobber_list;
	result->AsmStmt.output_count = output_count;
	result->AsmStmt.input_count = input_count;
	result->AsmStmt.clobber_count = clobber_count;
	return result;
}





gb_inline AstNode *make_bad_decl(AstFile *f, Token begin, Token end) {
	AstNode *result = make_node(f, AstNode_BadDecl);
	result->BadDecl.begin = begin;
	result->BadDecl.end = end;
	return result;
}

gb_inline AstNode *make_var_decl(AstFile *f, DeclKind kind, AstNodeArray names, AstNode *type, AstNodeArray values) {
	AstNode *result = make_node(f, AstNode_VarDecl);
	result->VarDecl.kind = kind;
	result->VarDecl.names = names;
	result->VarDecl.type = type;
	result->VarDecl.values = values;
	return result;
}

gb_inline AstNode *make_field(AstFile *f, AstNodeArray names, AstNode *type, b32 is_using) {
	AstNode *result = make_node(f, AstNode_Field);
	result->Field.names = names;
	result->Field.type = type;
	result->Field.is_using = is_using;
	return result;
}

gb_inline AstNode *make_proc_type(AstFile *f, Token token, AstNodeArray params, AstNodeArray results) {
	AstNode *result = make_node(f, AstNode_ProcType);
	result->ProcType.token = token;
	result->ProcType.params = params;
	result->ProcType.results = results;
	return result;
}

gb_inline AstNode *make_proc_decl(AstFile *f, AstNode *name, AstNode *proc_type, AstNode *body, u64 tags, String foreign_name) {
	AstNode *result = make_node(f, AstNode_ProcDecl);
	result->ProcDecl.name = name;
	result->ProcDecl.type = proc_type;
	result->ProcDecl.body = body;
	result->ProcDecl.tags = tags;
	result->ProcDecl.foreign_name = foreign_name;
	return result;
}

gb_inline AstNode *make_pointer_type(AstFile *f, Token token, AstNode *type) {
	AstNode *result = make_node(f, AstNode_PointerType);
	result->PointerType.token = token;
	result->PointerType.type = type;
	return result;
}

gb_inline AstNode *make_array_type(AstFile *f, Token token, AstNode *count, AstNode *elem) {
	AstNode *result = make_node(f, AstNode_ArrayType);
	result->ArrayType.token = token;
	result->ArrayType.count = count;
	result->ArrayType.elem = elem;
	return result;
}

gb_inline AstNode *make_vector_type(AstFile *f, Token token, AstNode *count, AstNode *elem) {
	AstNode *result = make_node(f, AstNode_VectorType);
	result->VectorType.token = token;
	result->VectorType.count = count;
	result->VectorType.elem  = elem;
	return result;
}

gb_inline AstNode *make_struct_type(AstFile *f, Token token, AstNodeArray decls, isize decl_count, b32 is_packed, b32 is_ordered) {
	AstNode *result = make_node(f, AstNode_StructType);
	result->StructType.token = token;
	result->StructType.decls = decls;
	result->StructType.decl_count = decl_count;
	result->StructType.is_packed = is_packed;
	result->StructType.is_ordered = is_ordered;
	return result;
}


gb_inline AstNode *make_union_type(AstFile *f, Token token, AstNodeArray decls, isize decl_count) {
	AstNode *result = make_node(f, AstNode_UnionType);
	result->UnionType.token = token;
	result->UnionType.decls = decls;
	result->UnionType.decl_count = decl_count;
	return result;
}

gb_inline AstNode *make_raw_union_type(AstFile *f, Token token, AstNodeArray decls, isize decl_count) {
	AstNode *result = make_node(f, AstNode_RawUnionType);
	result->RawUnionType.token = token;
	result->RawUnionType.decls = decls;
	result->RawUnionType.decl_count = decl_count;
	return result;
}


gb_inline AstNode *make_enum_type(AstFile *f, Token token, AstNode *base_type, AstNodeArray fields) {
	AstNode *result = make_node(f, AstNode_EnumType);
	result->EnumType.token = token;
	result->EnumType.base_type = base_type;
	result->EnumType.fields = fields;
	return result;
}

gb_inline AstNode *make_type_decl(AstFile *f, Token token, AstNode *name, AstNode *type) {
	AstNode *result = make_node(f, AstNode_TypeDecl);
	result->TypeDecl.token = token;
	result->TypeDecl.name = name;
	result->TypeDecl.type = type;
	return result;
}

gb_inline AstNode *make_import_decl(AstFile *f, Token token, Token relpath, Token import_name) {
	AstNode *result = make_node(f, AstNode_ImportDecl);
	result->ImportDecl.token = token;
	result->ImportDecl.relpath = relpath;
	result->ImportDecl.import_name = import_name;
	return result;
}

gb_inline AstNode *make_foreign_system_library(AstFile *f, Token token, Token filepath) {
	AstNode *result = make_node(f, AstNode_ForeignSystemLibrary);
	result->ForeignSystemLibrary.token = token;
	result->ForeignSystemLibrary.filepath = filepath;
	return result;
}

gb_inline b32 next_token(AstFile *f) {
	if (f->cursor+1 < f->tokens + gb_array_count(f->tokens)) {
		f->cursor++;
		return true;
	} else {
		ast_file_err(f, f->cursor[0], "Token is EOF");
		return false;
	}
}

gb_inline Token expect_token(AstFile *f, TokenKind kind) {
	Token prev = f->cursor[0];
	if (prev.kind != kind) {
		ast_file_err(f, f->cursor[0], "Expected `%.*s`, got `%.*s`",
		             LIT(token_strings[kind]),
		             LIT(token_strings[prev.kind]));
	}
	next_token(f);
	return prev;
}

gb_inline Token expect_operator(AstFile *f) {
	Token prev = f->cursor[0];
	if (!gb_is_between(prev.kind, Token__OperatorBegin+1, Token__OperatorEnd-1)) {
		ast_file_err(f, f->cursor[0], "Expected an operator, got `%.*s`",
		             LIT(token_strings[prev.kind]));
	}
	next_token(f);
	return prev;
}

gb_inline Token expect_keyword(AstFile *f) {
	Token prev = f->cursor[0];
	if (!gb_is_between(prev.kind, Token__KeywordBegin+1, Token__KeywordEnd-1)) {
		ast_file_err(f, f->cursor[0], "Expected a keyword, got `%.*s`",
		             LIT(token_strings[prev.kind]));
	}
	next_token(f);
	return prev;
}

gb_inline b32 allow_token(AstFile *f, TokenKind kind) {
	Token prev = f->cursor[0];
	if (prev.kind == kind) {
		next_token(f);
		return true;
	}
	return false;
}


b32 is_blank_ident(String str) {
	if (str.len == 1) {
		return str.text[0] == '_';
	}
	return false;
}


void fix_advance_to_next_stmt(AstFile *f) {
	// TODO(bill): fix_advance_to_next_stmt
#if 0
	for (;;) {
		Token t = f->cursor[0];
		switch (t.kind) {
		case Token_EOF:
			return;

		case Token_type:
		case Token_break:
		case Token_continue:
		case Token_fallthrough:
		case Token_if:
		case Token_for:
		case Token_defer:
		case Token_return:
			if (token_pos_are_equal(t.pos, f->fix_prev_pos) &&
			    f->fix_count < PARSER_MAX_FIX_COUNT) {
				f->fix_count++;
				return;
			}
			if (token_pos_cmp(f->fix_prev_pos, t.pos) < 0) {
				f->fix_prev_pos = t.pos;
				f->fix_count = 0; // NOTE(bill): Reset
				return;
			}

		}
		next_token(f);
	}
#endif
}

b32 expect_semicolon_after_stmt(AstFile *f, AstNode *s) {
	// if (s != NULL) {
	// 	switch (s->kind) {
	// 	case AstNode_ProcDecl:
	// 		return true;
	// 	case AstNode_TypeDecl: {
	// 		switch (s->TypeDecl.type->kind) {
	// 		case AstNode_StructType:
	// 		case AstNode_UnionType:
	// 		case AstNode_EnumType:
	// 		case AstNode_ProcType:
	// 			return true;
	// 		}
	// 	} break;
	// 	}
	// }

	if (!allow_token(f, Token_Semicolon)) {
		if (f->cursor[0].pos.line == f->cursor[-1].pos.line) {
			if (f->cursor[0].kind != Token_CloseBrace) {
				// CLEANUP(bill): Semicolon handling in parser
				ast_file_err(f, f->cursor[0],
				             "Expected `;` after %.*s, got `%.*s`",
				             LIT(ast_node_strings[s->kind]), LIT(token_strings[f->cursor[0].kind]));
				return false;
			}
		}
	}
	return true;
}


AstNode *    parse_expr(AstFile *f, b32 lhs);
AstNode *    parse_proc_type(AstFile *f);
AstNodeArray parse_stmt_list(AstFile *f);
AstNode *    parse_stmt(AstFile *f);
AstNode *    parse_body(AstFile *f);

AstNode *parse_identifier(AstFile *f) {
	Token token = f->cursor[0];
	if (token.kind == Token_Identifier) {
		next_token(f);
	} else {
		token.string = make_string("_");
		expect_token(f, Token_Identifier);
	}
	return make_ident(f, token);
}

AstNode *parse_tag_expr(AstFile *f, AstNode *expression) {
	Token token = expect_token(f, Token_Hash);
	Token name  = expect_token(f, Token_Identifier);
	return make_tag_expr(f, token, name, expression);
}

AstNode *parse_tag_stmt(AstFile *f, AstNode *statement) {
	Token token = expect_token(f, Token_Hash);
	Token name  = expect_token(f, Token_Identifier);
	return make_tag_stmt(f, token, name, statement);
}

AstNode *unparen_expr(AstNode *node) {
	for (;;) {
		if (node->kind != AstNode_ParenExpr)
			return node;
		node = node->ParenExpr.expr;
	}
}

AstNode *parse_value(AstFile *f);

AstNodeArray parse_element_list(AstFile *f) {
	AstNodeArray elems = make_ast_node_array(f);

	while (f->cursor[0].kind != Token_CloseBrace &&
	       f->cursor[0].kind != Token_EOF) {
		AstNode *elem = parse_value(f);
		if (f->cursor[0].kind == Token_Eq) {
			Token eq = expect_token(f, Token_Eq);
			AstNode *value = parse_value(f);
			elem = make_field_value(f, elem, value, eq);
		}

		gb_array_append(elems, elem);

		if (f->cursor[0].kind != Token_Comma) {
			break;
		}
		next_token(f);
	}

	return elems;
}

AstNode *parse_literal_value(AstFile *f, AstNode *type) {
	AstNodeArray elems = NULL;
	Token open = expect_token(f, Token_OpenBrace);
	f->expr_level++;
	if (f->cursor[0].kind != Token_CloseBrace) {
		elems = parse_element_list(f);
	}
	f->expr_level--;
	Token close = expect_token(f, Token_CloseBrace);

	return make_compound_lit(f, type, elems, open, close);
}

AstNode *parse_value(AstFile *f) {
	if (f->cursor[0].kind == Token_OpenBrace)
		return parse_literal_value(f, NULL);

	AstNode *value = parse_expr(f, false);
	return value;
}

AstNode *parse_identifier_or_type(AstFile *f, u32 flags = 0);


void check_proc_add_tag(AstFile *f, AstNode *tag_expr, u64 *tags, ProcTag tag, String tag_name) {
	if (*tags & tag) {
		ast_file_err(f, ast_node_token(tag_expr), "Procedure tag already used: %.*s", LIT(tag_name));
	}
	*tags |= tag;
}

b32 is_foreign_name_valid(String name) {
	// TODO(bill): is_foreign_name_valid
	if (name.len == 0)
		return false;
	isize offset = 0;
	while (offset < name.len) {
		Rune rune;
		isize remaining = name.len - offset;
		isize width = gb_utf8_decode(name.text+offset, remaining, &rune);
		if (rune == GB_RUNE_INVALID && width == 1) {
			return false;
		} else if (rune == GB_RUNE_BOM && remaining > 0) {
			return false;
		}

		if (offset == 0) {
			switch (rune) {
			case '-':
			case '$':
			case '.':
			case '_':
				break;
			default:
				if (!gb_char_is_alpha(cast(char)rune))
					return false;
				break;
			}
		} else {
			switch (rune) {
			case '-':
			case '$':
			case '.':
			case '_':
				break;
			default:
				if (!gb_char_is_alphanumeric(cast(char)rune)) {
					return false;
				}
				break;
			}
		}

		offset += width;
	}

	return true;
}

void parse_proc_tags(AstFile *f, u64 *tags, String *foreign_name) {
	// TODO(bill): Add this to procedure literals too
	while (f->cursor[0].kind == Token_Hash) {
		AstNode *tag_expr = parse_tag_expr(f, NULL);
		ast_node(te, TagExpr, tag_expr);
		String tag_name = te->name.string;
		if (are_strings_equal(tag_name, make_string("foreign"))) {
			check_proc_add_tag(f, tag_expr, tags, ProcTag_foreign, tag_name);
			if (f->cursor[0].kind == Token_String) {
				*foreign_name = f->cursor[0].string;
				// TODO(bill): Check if valid string
				if (!is_foreign_name_valid(*foreign_name)) {
					ast_file_err(f, ast_node_token(tag_expr), "Invalid alternative foreign procedure name");
				}

				next_token(f);
			}
		} else if (are_strings_equal(tag_name, make_string("bounds_check"))) {
			check_proc_add_tag(f, tag_expr, tags, ProcTag_bounds_check, tag_name);
		} else if (are_strings_equal(tag_name, make_string("no_bounds_check"))) {
			check_proc_add_tag(f, tag_expr, tags, ProcTag_no_bounds_check, tag_name);
		} else if (are_strings_equal(tag_name, make_string("inline"))) {
			check_proc_add_tag(f, tag_expr, tags, ProcTag_inline, tag_name);
		} else if (are_strings_equal(tag_name, make_string("no_inline"))) {
			check_proc_add_tag(f, tag_expr, tags, ProcTag_no_inline, tag_name);
		// } else if (are_strings_equal(tag_name, make_string("no_context"))) {
			// check_proc_add_tag(f, tag_expr, tags, ProcTag_no_context, tag_name);
		} else {
			ast_file_err(f, ast_node_token(tag_expr), "Unknown procedure tag");
		}
	}

	if ((*tags & ProcTag_inline) && (*tags & ProcTag_no_inline)) {
		ast_file_err(f, f->cursor[0], "You cannot apply both #inline and #no_inline to a procedure");
	}

	if ((*tags & ProcTag_bounds_check) && (*tags & ProcTag_no_bounds_check)) {
		ast_file_err(f, f->cursor[0], "You cannot apply both #bounds_check and #no_bounds_check to a procedure");
	}

	if (((*tags & ProcTag_bounds_check) || (*tags & ProcTag_no_bounds_check)) && (*tags & ProcTag_foreign)) {
		ast_file_err(f, f->cursor[0], "You cannot apply both #bounds_check or #no_bounds_check to a procedure without a body");
	}
}

AstNode *parse_operand(AstFile *f, b32 lhs) {
	AstNode *operand = NULL; // Operand
	switch (f->cursor[0].kind) {
	case Token_Identifier:
		operand = parse_identifier(f);
		if (!lhs) {
			// TODO(bill): Handle?
		}
		return operand;

	case Token_Integer:
	case Token_Float:
	case Token_String:
	case Token_Rune:
		operand = make_basic_lit(f, f->cursor[0]);
		next_token(f);
		return operand;

	case Token_OpenParen: {
		Token open, close;
		// NOTE(bill): Skip the Paren Expression
		open = expect_token(f, Token_OpenParen);
		f->expr_level++;
		operand = parse_expr(f, false);
		f->expr_level--;
		close = expect_token(f, Token_CloseParen);
		return make_paren_expr(f, operand, open, close);
	}

	case Token_Hash: {
		operand = parse_tag_expr(f, NULL);
		String name = operand->TagExpr.name.string;
		if (are_strings_equal(name, make_string("rune"))) {
			if (f->cursor[0].kind == Token_String) {
				Token *s = &f->cursor[0];

				if (gb_utf8_strnlen(s->string.text, s->string.len) != 1) {
					ast_file_err(f, *s, "Invalid rune literal %.*s", LIT(s->string));
				}
				s->kind = Token_Rune; // NOTE(bill): Change it
			} else {
				expect_token(f, Token_String);
			}
			operand = parse_operand(f, lhs);
		} else {
			operand->TagExpr.expr = parse_expr(f, false);
		}
		return operand;
	}

	// Parse Procedure Type or Literal
	case Token_proc: {
		AstNode *curr_proc = f->curr_proc;
		AstNode *type = parse_proc_type(f);
		f->curr_proc = type;
		defer (f->curr_proc = curr_proc);

		u64 tags = 0;
		String foreign_name = {};
		parse_proc_tags(f, &tags, &foreign_name);
		if (tags & ProcTag_foreign) {
			ast_file_err(f, f->cursor[0], "#foreign cannot be applied to procedure literals");
		}

		if (f->cursor[0].kind != Token_OpenBrace) {
			return type;
		} else {
			AstNode *body;

			f->expr_level++;
			body = parse_body(f);
			f->expr_level--;

			return make_proc_lit(f, type, body, tags);
		}
	}

	default: {
		AstNode *type = parse_identifier_or_type(f);
		if (type != NULL) {
			// NOTE(bill): Sanity check as identifiers should be handled already
			GB_ASSERT_MSG(type->kind != AstNode_Ident, "Type Cannot be identifier");
			return type;
		}
	}
	}

	Token begin = f->cursor[0];
	ast_file_err(f, begin, "Expected an operand");
	fix_advance_to_next_stmt(f);
	return make_bad_expr(f, begin, f->cursor[0]);
}

b32 is_literal_type(AstNode *node) {
	switch (node->kind) {
	case AstNode_BadExpr:
	case AstNode_Ident:
	case AstNode_SelectorExpr:
	case AstNode_ArrayType:
	case AstNode_VectorType:
	case AstNode_StructType:
		return true;
	}
	return false;
}

AstNode *parse_call_expr(AstFile *f, AstNode *operand) {
	AstNodeArray args = make_ast_node_array(f);
	Token open_paren, close_paren;
	Token ellipsis = {};

	f->expr_level++;
	open_paren = expect_token(f, Token_OpenParen);

	while (f->cursor[0].kind != Token_CloseParen &&
	       f->cursor[0].kind != Token_EOF &&
	       ellipsis.pos.line == 0) {
		if (f->cursor[0].kind == Token_Comma)
			ast_file_err(f, f->cursor[0], "Expected an expression not a ,");

		if (f->cursor[0].kind == Token_Ellipsis) {
			ellipsis = f->cursor[0];
			next_token(f);
		}

		gb_array_append(args, parse_expr(f, false));

		if (f->cursor[0].kind != Token_Comma) {
			if (f->cursor[0].kind == Token_CloseParen)
				break;
		}

		next_token(f);
	}

	f->expr_level--;
	close_paren = expect_token(f, Token_CloseParen);

	return make_call_expr(f, operand, args, open_paren, close_paren, ellipsis);
}

AstNode *parse_atom_expr(AstFile *f, b32 lhs) {
	AstNode *operand = parse_operand(f, lhs);

	b32 loop = true;
	while (loop) {
		switch (f->cursor[0].kind) {

		case Token_Prime: {
			Token op = expect_token(f, Token_Prime);
			if (lhs) {
				// TODO(bill): Handle this
			}
			AstNode *proc = parse_identifier(f);
			gbArray(AstNode *) args;
			gb_array_init_reserve(args, gb_arena_allocator(&f->arena), 1);
			gb_array_append(args, operand);
			operand = make_call_expr(f, proc, args, ast_node_token(operand), op, empty_token);
		} break;

		case Token_OpenParen: {
			if (lhs) {
				// TODO(bill): Handle this shit! Is this even allowed in this language?!
			}
			operand = parse_call_expr(f, operand);
		} break;

		case Token_Period: {
			Token token = f->cursor[0];
			next_token(f);
			if (lhs) {
				// TODO(bill): handle this
			}
			switch (f->cursor[0].kind) {
			case Token_Identifier:
				operand = make_selector_expr(f, token, operand, parse_identifier(f));
				break;
			default: {
				ast_file_err(f, f->cursor[0], "Expected a selector");
				next_token(f);
				operand = make_selector_expr(f, f->cursor[0], operand, NULL);
			} break;
			}
		} break;

		case Token_OpenBracket: {
			if (lhs) {
				// TODO(bill): Handle this
			}
			Token open, close;
			AstNode *indices[3] = {};

			f->expr_level++;
			open = expect_token(f, Token_OpenBracket);

			if (f->cursor[0].kind != Token_Colon)
				indices[0] = parse_expr(f, false);
			isize colon_count = 0;
			Token colons[2] = {};

			while (f->cursor[0].kind == Token_Colon && colon_count < 2) {
				colons[colon_count++] = f->cursor[0];
				next_token(f);
				if (f->cursor[0].kind != Token_Colon &&
				    f->cursor[0].kind != Token_CloseBracket &&
				    f->cursor[0].kind != Token_EOF) {
					indices[colon_count] = parse_expr(f, false);
				}
			}

			f->expr_level--;
			close = expect_token(f, Token_CloseBracket);

			if (colon_count == 0) {
				operand = make_index_expr(f, operand, indices[0], open, close);
			} else {
				b32 triple_indexed = false;
				if (colon_count == 2) {
					triple_indexed = true;
					if (indices[1] == NULL) {
						ast_file_err(f, colons[0], "Second index is required in a triple indexed slice");
						indices[1] = make_bad_expr(f, colons[0], colons[1]);
					}
					if (indices[2] == NULL) {
						ast_file_err(f, colons[1], "Third index is required in a triple indexed slice");
						indices[2] = make_bad_expr(f, colons[1], close);
					}
				}
				operand = make_slice_expr(f, operand, open, close, indices[0], indices[1], indices[2], triple_indexed);
			}
		} break;

		case Token_Pointer: // Deference
			operand = make_deref_expr(f, operand, expect_token(f, Token_Pointer));
			break;

		case Token_OpenBrace: {
			if (!lhs && is_literal_type(operand) && f->expr_level >= 0) {
				operand = parse_literal_value(f, operand);
			} else {
				loop = false;
			}
		} break;

		default:
			loop = false;
			break;
		}

		lhs = false; // NOTE(bill): 'tis not lhs anymore
	}

	return operand;
}

AstNode *parse_type(AstFile *f);

AstNode *parse_unary_expr(AstFile *f, b32 lhs) {
	switch (f->cursor[0].kind) {
	case Token_Pointer:
	case Token_Add:
	case Token_Sub:
	case Token_Not:
	case Token_Xor: {
		AstNode *operand;
		Token op = f->cursor[0];
		next_token(f);
		operand = parse_unary_expr(f, lhs);
		return make_unary_expr(f, op, operand);
	} break;
	}

	return parse_atom_expr(f, lhs);
}

AstNode *parse_binary_expr(AstFile *f, b32 lhs, i32 prec_in) {
	AstNode *expression = parse_unary_expr(f, lhs);
	for (i32 prec = token_precedence(f->cursor[0]); prec >= prec_in; prec--) {
		for (;;) {
			AstNode *right;
			Token op = f->cursor[0];
			i32 op_prec = token_precedence(op);
			if (op_prec != prec)
				break;
			expect_operator(f); // NOTE(bill): error checks too
			if (lhs) {
				// TODO(bill): error checking
				lhs = false;
			}

			switch (op.kind) {
			case Token_DoublePrime: {
				AstNode *proc = parse_identifier(f);
				AstNode *right = parse_binary_expr(f, false, prec+1);
				gbArray(AstNode *) args;
				gb_array_init_reserve(args, gb_arena_allocator(&f->arena), 2);
				gb_array_append(args, expression);
				gb_array_append(args, right);
				expression = make_call_expr(f, proc, args, op, ast_node_token(right), empty_token);
				continue;
			} break;

			case Token_as:
			case Token_transmute:
			case Token_down_cast:
				right = parse_type(f);
				break;

			default:
				right = parse_binary_expr(f, false, prec+1);
				if (!right) {
					ast_file_err(f, op, "Expected expression on the right hand side of the binary operator");
				}
				break;
			}
			expression = make_binary_expr(f, op, expression, right);
		}
	}
	return expression;
}

AstNode *parse_expr(AstFile *f, b32 lhs) {
	return parse_binary_expr(f, lhs, 0+1);
}


AstNodeArray parse_expr_list(AstFile *f, b32 lhs) {
	AstNodeArray list = make_ast_node_array(f);
	do {
		AstNode *e = parse_expr(f, lhs);
		gb_array_append(list, e);
		if (f->cursor[0].kind != Token_Comma ||
		    f->cursor[0].kind == Token_EOF) {
		    break;
		}
		next_token(f);
	} while (true);

	return list;
}

AstNodeArray parse_lhs_expr_list(AstFile *f) {
	return parse_expr_list(f, true);
}

AstNodeArray parse_rhs_expr_list(AstFile *f) {
	return parse_expr_list(f, false);
}

AstNode *parse_decl(AstFile *f, AstNodeArray names);

AstNode *parse_simple_stmt(AstFile *f) {
	isize lhs_count = 0, rhs_count = 0;
	AstNodeArray lhs = parse_lhs_expr_list(f);


	AstNode *statement = NULL;
	Token token = f->cursor[0];
	switch (token.kind) {
	case Token_Eq:
	case Token_AddEq:
	case Token_SubEq:
	case Token_MulEq:
	case Token_QuoEq:
	case Token_ModEq:
	case Token_AndEq:
	case Token_OrEq:
	case Token_XorEq:
	case Token_ShlEq:
	case Token_ShrEq:
	case Token_AndNotEq:
	case Token_CmpAndEq:
	case Token_CmpOrEq:
	{
		if (f->curr_proc == NULL) {
			ast_file_err(f, f->cursor[0], "You cannot use a simple statement in the file scope");
			return make_bad_stmt(f, f->cursor[0], f->cursor[0]);
		}
		next_token(f);
		AstNodeArray rhs = parse_rhs_expr_list(f);
		if (gb_array_count(rhs) == 0) {
			ast_file_err(f, token, "No right-hand side in assignment statement.");
			return make_bad_stmt(f, token, f->cursor[0]);
		}
		return make_assign_stmt(f, token, lhs, rhs);
	} break;

	case Token_Colon: // Declare
		return parse_decl(f, lhs);
	}

	if (lhs_count > 1) {
		ast_file_err(f, token, "Expected 1 expression");
		return make_bad_stmt(f, token, f->cursor[0]);
	}

	token = f->cursor[0];
	switch (token.kind) {
	case Token_Increment:
	case Token_Decrement:
		if (f->curr_proc == NULL) {
			ast_file_err(f, f->cursor[0], "You cannot use a simple statement in the file scope");
			return make_bad_stmt(f, f->cursor[0], f->cursor[0]);
		}
		statement = make_inc_dec_stmt(f, token, lhs[0]);
		next_token(f);
		return statement;
	}

	return make_expr_stmt(f, lhs[0]);
}



AstNode *parse_block_stmt(AstFile *f) {
	if (f->curr_proc == NULL) {
		ast_file_err(f, f->cursor[0], "You cannot use a block statement in the file scope");
		return make_bad_stmt(f, f->cursor[0], f->cursor[0]);
	}
	AstNode *block_stmt = parse_body(f);
	return block_stmt;
}

AstNode *convert_stmt_to_expr(AstFile *f, AstNode *statement, String kind) {
	if (statement == NULL)
		return NULL;

	if (statement->kind == AstNode_ExprStmt)
		return statement->ExprStmt.expr;

	ast_file_err(f, f->cursor[0], "Expected `%.*s`, found a simple statement.", LIT(kind));
	return make_bad_expr(f, f->cursor[0], f->cursor[1]);
}

AstNodeArray parse_identfier_list(AstFile *f) {
	AstNodeArray list = make_ast_node_array(f);

	do {
		gb_array_append(list, parse_identifier(f));
		if (f->cursor[0].kind != Token_Comma ||
		    f->cursor[0].kind == Token_EOF) {
		    break;
		}
		next_token(f);
	} while (true);

	return list;
}



AstNode *parse_type_attempt(AstFile *f) {
	AstNode *type = parse_identifier_or_type(f);
	if (type != NULL) {
		// TODO(bill): Handle?
	}
	return type;
}

AstNode *parse_type(AstFile *f) {
	AstNode *type = parse_type_attempt(f);
	if (type == NULL) {
		Token token = f->cursor[0];
		ast_file_err(f, token, "Expected a type");
		next_token(f);
		return make_bad_expr(f, token, f->cursor[0]);
	}
	return type;
}


Token parse_procedure_signature(AstFile *f,
                                AstNodeArray *params, AstNodeArray *results);

AstNode *parse_proc_type(AstFile *f) {
	AstNodeArray params = NULL;
	AstNodeArray results = NULL;

	Token proc_token = parse_procedure_signature(f, &params, &results);

	return make_proc_type(f, proc_token, params, results);
}

AstNode *parse_field_decl(AstFile *f) {
	b32 is_using = false;
	if (allow_token(f, Token_using)) {
		is_using = true;
	}

	AstNodeArray names = parse_lhs_expr_list(f);
	if (gb_array_count(names) == 0) {
		ast_file_err(f, f->cursor[0], "Empty field declaration");
	}

	if (gb_array_count(names) > 1 && is_using) {
		ast_file_err(f, f->cursor[0], "Cannot apply `using` to more than one of the same type");
		is_using = false;
	}


	expect_token(f, Token_Colon);

	AstNode *type = NULL;
	if (f->cursor[0].kind == Token_Ellipsis) {
		Token ellipsis = f->cursor[0];
		next_token(f);
		type = parse_type_attempt(f);
		if (type == NULL) {
			ast_file_err(f, f->cursor[0], "variadic parameter is missing a type after `..`");
			type = make_bad_expr(f, ellipsis, f->cursor[0]);
		} else {
			if (gb_array_count(names) > 1) {
				ast_file_err(f, f->cursor[0], "mutliple variadic parameters, only  `..`");
			} else {
				type = make_ellipsis(f, ellipsis, type);
			}
		}
	} else {
		type = parse_type_attempt(f);
	}

	if (type == NULL) {
		ast_file_err(f, f->cursor[0], "Expected a type for this field declaration");
	}

	AstNode *field = make_field(f, names, type, is_using);
	return field;
}

AstNodeArray parse_parameter_list(AstFile *f) {
	AstNodeArray params = make_ast_node_array(f);
	while (f->cursor[0].kind == Token_Identifier ||
	       f->cursor[0].kind == Token_using) {
		AstNode *field = parse_field_decl(f);
		gb_array_append(params, field);
		if (f->cursor[0].kind != Token_Comma) {
			break;
		}
		next_token(f);
	}

	return params;
}


AstNodeArray parse_struct_params(AstFile *f, isize *decl_count_, b32 using_allowed) {
	AstNodeArray decls = make_ast_node_array(f);
	isize decl_count = 0;

	while (f->cursor[0].kind == Token_Identifier ||
	       f->cursor[0].kind == Token_using) {
		b32 is_using = false;
		if (allow_token(f, Token_using)) {
			is_using = true;
		}
		AstNodeArray names = parse_lhs_expr_list(f);
		if (gb_array_count(names) == 0) {
			ast_file_err(f, f->cursor[0], "Empty field declaration");
		}

		if (!using_allowed && is_using) {
			ast_file_err(f, f->cursor[0], "Cannot apply `using` to members of a union");
			is_using = false;
		}
		if (gb_array_count(names) > 1 && is_using) {
			ast_file_err(f, f->cursor[0], "Cannot apply `using` to more than one of the same type");
		}

		AstNode *decl = NULL;

		if (f->cursor[0].kind == Token_Colon) {
			decl = parse_decl(f, names);

			if (decl->kind == AstNode_ProcDecl) {
				ast_file_err(f, f->cursor[0], "Procedure declarations are not allowed within a structure");
				decl = make_bad_decl(f, ast_node_token(names[0]), f->cursor[0]);
			}
		} else {
			ast_file_err(f, f->cursor[0], "Illegal structure field");
			decl = make_bad_decl(f, ast_node_token(names[0]), f->cursor[0]);
		}

		expect_semicolon_after_stmt(f, decl);

		if (decl != NULL && is_ast_node_decl(decl)) {
			gb_array_append(decls, decl);
			if (decl->kind == AstNode_VarDecl) {
				decl->VarDecl.is_using = is_using && using_allowed;

				if (decl->VarDecl.kind == Declaration_Mutable) {
					if (gb_array_count(decl->VarDecl.values) > 0) {
						ast_file_err(f, f->cursor[0], "Default variable assignments within a structure will be ignored (at the moment)");
					}
				}

			} else {
				decl_count += 1;
			}
		}
	}

	if (decl_count_) *decl_count_ = decl_count;

	return decls;
}

AstNode *parse_identifier_or_type(AstFile *f, u32 flags) {
	switch (f->cursor[0].kind) {
	case Token_volatile:
		next_token(f);
		return parse_identifier_or_type(f, flags | TypeFlag_volatile);

	case Token_atomic:
		next_token(f);
		return parse_identifier_or_type(f, flags | TypeFlag_atomic);

	case Token_Identifier: {
		AstNode *e = parse_identifier(f);
		while (f->cursor[0].kind == Token_Period) {
			Token token = f->cursor[0];
			next_token(f);
			AstNode *sel = parse_identifier(f);
			e = make_selector_expr(f, token, e, sel);
		}
		if (f->cursor[0].kind == Token_OpenParen) {
			// HACK NOTE(bill): For type_of_val(expr)
			e = parse_call_expr(f, e);
		}
		e->type_flags = flags;
		return e;
	}

	case Token_Pointer: {
		AstNode *e = make_pointer_type(f, expect_token(f, Token_Pointer), parse_type(f));
		e->type_flags = flags;
		return e;
	}

	case Token_OpenBracket: {
		f->expr_level++;
		Token token = expect_token(f, Token_OpenBracket);
		AstNode *count_expr = NULL;

		if (f->cursor[0].kind == Token_Ellipsis) {
			count_expr = make_ellipsis(f, f->cursor[0], NULL);
			next_token(f);
		} else if (f->cursor[0].kind != Token_CloseBracket) {
			count_expr = parse_expr(f, false);
		}
		expect_token(f, Token_CloseBracket);
		f->expr_level--;
		AstNode *e = make_array_type(f, token, count_expr, parse_type(f));
		e->type_flags = flags;
		return e;
	}

	case Token_OpenBrace: {
		f->expr_level++;
		Token token = expect_token(f, Token_OpenBrace);
		AstNode *count_expr = parse_expr(f, false);
		expect_token(f, Token_CloseBrace);
		f->expr_level--;
		AstNode *e = make_vector_type(f, token, count_expr, parse_type(f));
		e->type_flags = flags;
		return e;
	}

	case Token_struct: {
		Token token = expect_token(f, Token_struct);
		b32 is_packed = false;
		b32 is_ordered = false;
		while (allow_token(f, Token_Hash)) {
			Token tag = expect_token(f, Token_Identifier);
			if (are_strings_equal(tag.string, make_string("packed"))) {
				is_packed = true;
			} else if (are_strings_equal(tag.string, make_string("ordered"))) {
				is_ordered = true;
			}  else {
				ast_file_err(f, tag, "Expected a `#packed` or `#ordered` tag");
			}
		}

		if (is_packed && is_ordered) {
			ast_file_err(f, token, "`#ordered` is not needed with `#packed` which implies ordering");
		}

		Token open = expect_token(f, Token_OpenBrace);
		isize decl_count = 0;
		AstNodeArray decls = parse_struct_params(f, &decl_count, true);
		Token close = expect_token(f, Token_CloseBrace);

		AstNode *e = make_struct_type(f, token, decls, decl_count, is_packed, is_ordered);
		e->type_flags = flags;
		return e;
	} break;

	case Token_union: {
		Token token = expect_token(f, Token_union);
		Token open = expect_token(f, Token_OpenBrace);
		isize decl_count = 0;
		AstNodeArray decls = parse_struct_params(f, &decl_count, false);
		Token close = expect_token(f, Token_CloseBrace);

		AstNode *e = make_union_type(f, token, decls, decl_count);
		e->type_flags = flags;
		return e;
	}

	case Token_raw_union: {
		Token token = expect_token(f, Token_raw_union);
		Token open = expect_token(f, Token_OpenBrace);
		isize decl_count = 0;
		AstNodeArray decls = parse_struct_params(f, &decl_count, true);
		Token close = expect_token(f, Token_CloseBrace);

		AstNode *e = make_raw_union_type(f, token, decls, decl_count);
		e->type_flags = flags;
		return e;
	}

	case Token_enum: {
		Token token = expect_token(f, Token_enum);
		AstNode *base_type = NULL;
		Token open, close;

		if (f->cursor[0].kind != Token_OpenBrace) {
			base_type = parse_type(f);
		}

		AstNodeArray fields = make_ast_node_array(f);

		open  = expect_token(f, Token_OpenBrace);

		while (f->cursor[0].kind != Token_CloseBrace &&
		       f->cursor[0].kind != Token_EOF) {
			AstNode *name = parse_identifier(f);
			AstNode *value = NULL;
			Token eq = empty_token;
			if (f->cursor[0].kind == Token_Eq) {
				eq = expect_token(f, Token_Eq);
				value = parse_value(f);
			}
			AstNode *field = make_field_value(f, name, value, eq);
			gb_array_append(fields, field);
			if (f->cursor[0].kind != Token_Comma) {
				break;
			}
			next_token(f);
		}

		close = expect_token(f, Token_CloseBrace);

		AstNode *e = make_enum_type(f, token, base_type, fields);
		e->type_flags = flags;
		return e;
	}

	case Token_proc: {
		AstNode *curr_proc = f->curr_proc;
		AstNode *type = parse_proc_type(f);
		f->curr_proc = type;
		f->curr_proc = curr_proc;
		return type;
	}


	case Token_OpenParen: {
		// NOTE(bill): Skip the paren expression
		AstNode *type;
		Token open, close;
		open = expect_token(f, Token_OpenParen);
		type = parse_type(f);
		close = expect_token(f, Token_CloseParen);
		AstNode *e = make_paren_expr(f, type, open, close);
		e->type_flags = flags;
		return e;
	}

	// TODO(bill): Why is this even allowed? Is this a parsing error?
	case Token_Colon:
		break;

	case Token_Eq:
		if (f->cursor[-1].kind == Token_Colon)
			break;
		// fallthrough
	default:
		ast_file_err(f, f->cursor[0],
		             "Expected a type after `%.*s`, got `%.*s`", LIT(f->cursor[-1].string), LIT(f->cursor[0].string));
		break;
	}

	return NULL;
}


AstNodeArray parse_results(AstFile *f) {
	AstNodeArray results = make_ast_node_array(f);
	if (allow_token(f, Token_ArrowRight)) {
		if (f->cursor[0].kind == Token_OpenParen) {
			expect_token(f, Token_OpenParen);
			while (f->cursor[0].kind != Token_CloseParen &&
			       f->cursor[0].kind != Token_EOF) {
				gb_array_append(results, parse_type(f));
				if (f->cursor[0].kind != Token_Comma) {
					break;
				}
				next_token(f);
			}
			expect_token(f, Token_CloseParen);

			return results;
		}

		gb_array_append(results, parse_type(f));
		return results;
	}
	return results;
}

Token parse_procedure_signature(AstFile *f,
                               AstNodeArray *params,
                               AstNodeArray *results) {
	Token proc_token = expect_token(f, Token_proc);
	expect_token(f, Token_OpenParen);
	*params = parse_parameter_list(f);
	expect_token(f, Token_CloseParen);
	*results = parse_results(f);
	return proc_token;
}

AstNode *parse_body(AstFile *f) {
	AstNodeArray stmts = NULL;
	Token open, close;
	open = expect_token(f, Token_OpenBrace);
	stmts = parse_stmt_list(f);
	close = expect_token(f, Token_CloseBrace);

	return make_block_stmt(f, stmts, open, close);
}



AstNode *parse_proc_decl(AstFile *f, Token proc_token, AstNode *name) {
	AstNodeArray params = NULL;
	AstNodeArray results = NULL;

	parse_procedure_signature(f, &params, &results);
	AstNode *proc_type = make_proc_type(f, proc_token, params, results);

	AstNode *body = NULL;
	u64 tags = 0;
	String foreign_name = {};

	parse_proc_tags(f, &tags, &foreign_name);

	AstNode *curr_proc = f->curr_proc;
	f->curr_proc = proc_type;
	defer (f->curr_proc = curr_proc);

	if (f->cursor[0].kind == Token_OpenBrace) {
		if ((tags & ProcTag_foreign) != 0) {
			ast_file_err(f, f->cursor[0], "A procedure tagged as `#foreign` cannot have a body");
		}
		body = parse_body(f);
	}

	return make_proc_decl(f, name, proc_type, body, tags, foreign_name);
}

AstNode *parse_decl(AstFile *f, AstNodeArray names) {
	AstNodeArray values = NULL;
	AstNode *type = NULL;

	gb_for_array(i, names) {
		AstNode *name = names[i];
		if (name->kind == AstNode_Ident) {
			String n = name->Ident.string;
			// NOTE(bill): Check for reserved identifiers
			if (are_strings_equal(n, make_string("context"))) {
				ast_file_err(f, ast_node_token(name), "`context` is a reserved identifier");
				break;
			}
		}
	}

	if (allow_token(f, Token_Colon)) {
		if (!allow_token(f, Token_type)) {
			type = parse_identifier_or_type(f);
		}
	} else if (f->cursor[0].kind != Token_Eq && f->cursor[0].kind != Token_Semicolon) {
		ast_file_err(f, f->cursor[0], "Expected type separator `:` or `=`");
	}

	DeclKind declaration_kind = Declaration_Mutable;

	if (f->cursor[0].kind == Token_Eq ||
	    f->cursor[0].kind == Token_Colon) {
		if (f->cursor[0].kind == Token_Colon)
			declaration_kind = Declaration_Immutable;
		next_token(f);

		if (f->cursor[0].kind == Token_type ||
		    f->cursor[0].kind == Token_struct ||
		    f->cursor[0].kind == Token_enum ||
		    f->cursor[0].kind == Token_union ||
		    f->cursor[0].kind == Token_raw_union) {
			Token token = f->cursor[0];
			if (token.kind == Token_type) {
				next_token(f);
			}
			if (gb_array_count(names) != 1) {
				ast_file_err(f, ast_node_token(names[0]), "You can only declare one type at a time");
				return make_bad_decl(f, names[0]->Ident, token);
			}

			if (type != NULL) {
				ast_file_err(f, f->cursor[-1], "Expected either `type` or nothing between : and :");
				// NOTE(bill): Do not fail though
			}

			AstNode *type = parse_type(f);
			return make_type_decl(f, token, names[0], type);
		} else if (f->cursor[0].kind == Token_proc &&
		    declaration_kind == Declaration_Immutable) {
		    // NOTE(bill): Procedure declarations
			Token proc_token = f->cursor[0];
			AstNode *name = names[0];
			if (gb_array_count(names) != 1) {
				ast_file_err(f, proc_token, "You can only declare one procedure at a time");
				return make_bad_decl(f, name->Ident, proc_token);
			}

			AstNode *proc_decl = parse_proc_decl(f, proc_token, name);
			return proc_decl;

		} else {
			values = parse_rhs_expr_list(f);
			if (gb_array_count(values) > gb_array_count(names)) {
				ast_file_err(f, f->cursor[0], "Too many values on the right hand side of the declaration");
			} else if (gb_array_count(values) < gb_array_count(names) &&
			           declaration_kind == Declaration_Immutable) {
				ast_file_err(f, f->cursor[0], "All constant declarations must be defined");
			} else if (gb_array_count(values) == 0) {
				ast_file_err(f, f->cursor[0], "Expected an expression for this declaration");
			}
		}
	}

	if (declaration_kind == Declaration_Mutable) {
		if (type == NULL && gb_array_count(values) == 0) {
			ast_file_err(f, f->cursor[0], "Missing variable type or initialization");
			return make_bad_decl(f, f->cursor[0], f->cursor[0]);
		}
	} else if (declaration_kind == Declaration_Immutable) {
		if (type == NULL && gb_array_count(values) == 0 && gb_array_count(names) > 0) {
			ast_file_err(f, f->cursor[0], "Missing constant value");
			return make_bad_decl(f, f->cursor[0], f->cursor[0]);
		}
	} else {
		Token begin = f->cursor[0];
		ast_file_err(f, begin, "Unknown type of variable declaration");
		fix_advance_to_next_stmt(f);
		return make_bad_decl(f, begin, f->cursor[0]);
	}

	if (values == NULL) {
		values = make_ast_node_array(f);
	}

	return make_var_decl(f, declaration_kind, names, type, values);
}


AstNode *parse_if_stmt(AstFile *f) {
	if (f->curr_proc == NULL) {
		ast_file_err(f, f->cursor[0], "You cannot use an if statement in the file scope");
		return make_bad_stmt(f, f->cursor[0], f->cursor[0]);
	}

	Token token = expect_token(f, Token_if);
	AstNode *init = NULL;
	AstNode *cond = NULL;
	AstNode *body = NULL;
	AstNode *else_stmt = NULL;

	isize prev_level = f->expr_level;
	f->expr_level = -1;


	if (allow_token(f, Token_Semicolon)) {
		cond = parse_expr(f, false);
	} else {
		init = parse_simple_stmt(f);
		if (allow_token(f, Token_Semicolon)) {
			cond = parse_expr(f, false);
		} else {
			cond = convert_stmt_to_expr(f, init, make_string("boolean expression"));
			init = NULL;
		}
	}

	f->expr_level = prev_level;

	if (cond == NULL) {
		ast_file_err(f, f->cursor[0], "Expected condition for if statement");
	}

	body = parse_block_stmt(f);

	if (allow_token(f, Token_else)) {
		switch (f->cursor[0].kind) {
		case Token_if:
			else_stmt = parse_if_stmt(f);
			break;
		case Token_OpenBrace:
			else_stmt = parse_block_stmt(f);
			break;
		default:
			ast_file_err(f, f->cursor[0], "Expected if statement block statement");
			else_stmt = make_bad_stmt(f, f->cursor[0], f->cursor[1]);
			break;
		}
	}

	return make_if_stmt(f, token, init, cond, body, else_stmt);
}

AstNode *parse_return_stmt(AstFile *f) {
	if (f->curr_proc == NULL) {
		ast_file_err(f, f->cursor[0], "You cannot use a return statement in the file scope");
		return make_bad_stmt(f, f->cursor[0], f->cursor[0]);
	}

	Token token = expect_token(f, Token_return);
	AstNodeArray results = make_ast_node_array(f);

	if (f->cursor[0].kind != Token_Semicolon && f->cursor[0].kind != Token_CloseBrace &&
	    f->cursor[0].pos.line == token.pos.line) {
		results = parse_rhs_expr_list(f);
	}
	if (f->cursor[0].kind != Token_CloseBrace) {
		expect_semicolon_after_stmt(f, results ? results[0] : NULL);
	}

	return make_return_stmt(f, token, results);
}

AstNode *parse_for_stmt(AstFile *f) {
	if (f->curr_proc == NULL) {
		ast_file_err(f, f->cursor[0], "You cannot use a for statement in the file scope");
		return make_bad_stmt(f, f->cursor[0], f->cursor[0]);
	}

	Token token = expect_token(f, Token_for);

	AstNode *init = NULL;
	AstNode *cond = NULL;
	AstNode *end  = NULL;
	AstNode *body = NULL;

	if (f->cursor[0].kind != Token_OpenBrace) {
		isize prev_level = f->expr_level;
		f->expr_level = -1;
		if (f->cursor[0].kind != Token_Semicolon) {
			cond = parse_simple_stmt(f);
			if (is_ast_node_complex_stmt(cond)) {
				ast_file_err(f, f->cursor[0],
				             "You are not allowed that type of statement in a for statement, it is too complex!");
			}
		}

		if (allow_token(f, Token_Semicolon)) {
			init = cond;
			cond = NULL;
			if (f->cursor[0].kind != Token_Semicolon) {
				cond = parse_simple_stmt(f);
			}
			expect_token(f, Token_Semicolon);
			if (f->cursor[0].kind != Token_OpenBrace) {
				end = parse_simple_stmt(f);
			}
		}
		f->expr_level = prev_level;
	}
	body = parse_block_stmt(f);

	cond = convert_stmt_to_expr(f, cond, make_string("boolean expression"));

	return make_for_stmt(f, token, init, cond, end, body);
}

AstNode *parse_case_clause(AstFile *f) {
	Token token = f->cursor[0];
	AstNodeArray list = make_ast_node_array(f);
	if (allow_token(f, Token_case)) {
		list = parse_rhs_expr_list(f);
	} else {
		expect_token(f, Token_default);
	}
	expect_token(f, Token_Colon); // TODO(bill): Is this the best syntax?
	AstNodeArray stmts = parse_stmt_list(f);

	return make_case_clause(f, token, list, stmts);
}


AstNode *parse_type_case_clause(AstFile *f) {
	Token token = f->cursor[0];
	AstNodeArray clause = make_ast_node_array(f);
	if (allow_token(f, Token_case)) {
		gb_array_append(clause, parse_expr(f, false));
	} else {
		expect_token(f, Token_default);
	}
	expect_token(f, Token_Colon); // TODO(bill): Is this the best syntax?
	AstNodeArray stmts = parse_stmt_list(f);

	return make_case_clause(f, token, clause, stmts);
}


AstNode *parse_match_stmt(AstFile *f) {
	if (f->curr_proc == NULL) {
		ast_file_err(f, f->cursor[0], "You cannot use a match statement in the file scope");
		return make_bad_stmt(f, f->cursor[0], f->cursor[0]);
	}

	Token token = expect_token(f, Token_match);
	AstNode *init = NULL;
	AstNode *tag = NULL;
	AstNode *body = NULL;
	Token open, close;



	if (allow_token(f, Token_type)) {
		isize prev_level = f->expr_level;
		f->expr_level = -1;

		AstNode *var = parse_identifier(f);
		expect_token(f, Token_Colon);
		tag = parse_simple_stmt(f);

		f->expr_level = prev_level;

		open = expect_token(f, Token_OpenBrace);
		AstNodeArray list = make_ast_node_array(f);

		while (f->cursor[0].kind == Token_case ||
		       f->cursor[0].kind == Token_default) {
			gb_array_append(list, parse_type_case_clause(f));
		}

		close = expect_token(f, Token_CloseBrace);
		body = make_block_stmt(f, list, open, close);

		tag = convert_stmt_to_expr(f, tag, make_string("type match expression"));
		return make_type_match_stmt(f, token, tag, var, body);
	} else {
		if (f->cursor[0].kind != Token_OpenBrace) {
			isize prev_level = f->expr_level;
			f->expr_level = -1;
			if (f->cursor[0].kind != Token_Semicolon) {
				tag = parse_simple_stmt(f);
			}
			if (allow_token(f, Token_Semicolon)) {
				init = tag;
				tag = NULL;
				if (f->cursor[0].kind != Token_OpenBrace) {
					tag = parse_simple_stmt(f);
				}
			}

			f->expr_level = prev_level;
		}

		open = expect_token(f, Token_OpenBrace);
		AstNodeArray list = make_ast_node_array(f);

		while (f->cursor[0].kind == Token_case ||
		       f->cursor[0].kind == Token_default) {
			gb_array_append(list, parse_case_clause(f));
		}

		close = expect_token(f, Token_CloseBrace);

		body = make_block_stmt(f, list, open, close);

		tag = convert_stmt_to_expr(f, tag, make_string("match expression"));
		return make_match_stmt(f, token, init, tag, body);
	}
}


AstNode *parse_defer_stmt(AstFile *f) {
	if (f->curr_proc == NULL) {
		ast_file_err(f, f->cursor[0], "You cannot use a defer statement in the file scope");
		return make_bad_stmt(f, f->cursor[0], f->cursor[0]);
	}

	Token token = expect_token(f, Token_defer);
	AstNode *statement = parse_stmt(f);
	switch (statement->kind) {
	case AstNode_EmptyStmt:
		ast_file_err(f, token, "Empty statement after defer (e.g. `;`)");
		break;
	case AstNode_DeferStmt:
		ast_file_err(f, token, "You cannot defer a defer statement");
		break;
	case AstNode_ReturnStmt:
		ast_file_err(f, token, "You cannot a return statement");
		break;
	}

	return make_defer_stmt(f, token, statement);
}

AstNode *parse_asm_stmt(AstFile *f) {
	Token token = expect_token(f, Token_asm);
	b32 is_volatile = false;
	if (allow_token(f, Token_volatile)) {
		is_volatile = true;
	}
	Token open, close, code_string;
	open = expect_token(f, Token_OpenBrace);
	code_string = expect_token(f, Token_String);
	AstNode *output_list = NULL;
	AstNode *input_list = NULL;
	AstNode *clobber_list = NULL;
	isize output_count = 0;
	isize input_count = 0;
	isize clobber_count = 0;

	// TODO(bill): Finish asm statement and determine syntax

	// if (f->cursor[0].kind != Token_CloseBrace) {
		// expect_token(f, Token_Colon);
	// }

	close = expect_token(f, Token_CloseBrace);

	return make_asm_stmt(f, token, is_volatile, open, close, code_string,
	                     output_list, input_list, clobber_list,
	                     output_count, input_count, clobber_count);

}



AstNode *parse_stmt(AstFile *f) {
	AstNode *s = NULL;
	Token token = f->cursor[0];
	switch (token.kind) {
	// Operands
	case Token_Identifier:
	case Token_Integer:
	case Token_Float:
	case Token_Rune:
	case Token_String:
	case Token_OpenParen:
	case Token_proc:
	// Unary Operators
	case Token_Add:
	case Token_Sub:
	case Token_Xor:
	case Token_Not:
		s = parse_simple_stmt(f);
		expect_semicolon_after_stmt(f, s);
		return s;

	// TODO(bill): other keywords
	case Token_if:     return parse_if_stmt(f);
	case Token_return: return parse_return_stmt(f);
	case Token_for:    return parse_for_stmt(f);
	case Token_match:  return parse_match_stmt(f);
	case Token_defer:  return parse_defer_stmt(f);
	case Token_asm:    return parse_asm_stmt(f);

	case Token_break:
	case Token_continue:
	case Token_fallthrough:
		next_token(f);
		s = make_branch_stmt(f, token);
		expect_semicolon_after_stmt(f, s);
		return s;


	case Token_using: {
		AstNode *node = NULL;

		next_token(f);
		node = parse_stmt(f);

		b32 valid = false;

		switch (node->kind) {
		case AstNode_ExprStmt: {
			AstNode *e = unparen_expr(node->ExprStmt.expr);
			while (e->kind == AstNode_SelectorExpr) {
				e = unparen_expr(e->SelectorExpr.selector);
			}
			if (e->kind == AstNode_Ident) {
				valid = true;
			}
		} break;
		case AstNode_VarDecl:
			if (node->VarDecl.kind == Declaration_Mutable) {
				valid = true;
			}
			break;
		}

		if (!valid) {
			ast_file_err(f, token, "Illegal use of `using` statement.");
			return make_bad_stmt(f, token, f->cursor[0]);
		}


		return make_using_stmt(f, token, node);
	} break;

	case Token_Hash: {
		s = parse_tag_stmt(f, NULL);
		String tag = s->TagStmt.name.string;
		if (are_strings_equal(tag, make_string("global_scope"))) {
			if (f->curr_proc == NULL) {
				f->is_global_scope = true;
				return make_empty_stmt(f, f->cursor[0]);
			}
			ast_file_err(f, token, "You cannot use #global_scope within a procedure. This must be done at the file scope.");
			return make_bad_decl(f, token, f->cursor[0]);
		} else if (are_strings_equal(tag, make_string("import"))) {
			// TODO(bill): better error messages
			Token file_path = expect_token(f, Token_String);
			Token as = expect_token(f, Token_as);
			Token import_name = expect_token(f, Token_Identifier);

			if (f->curr_proc == NULL) {
				return make_import_decl(f, s->TagStmt.token, file_path, import_name);
			}
			ast_file_err(f, token, "You cannot use #import within a procedure. This must be done at the file scope.");
			return make_bad_decl(f, token, file_path);
		} else if (are_strings_equal(tag, make_string("foreign_system_library"))) {
			Token file_path = expect_token(f, Token_String);
			if (f->curr_proc == NULL) {
				return make_foreign_system_library(f, s->TagStmt.token, file_path);
			}
			ast_file_err(f, token, "You cannot use #foreign_system_library within a procedure. This must be done at the file scope.");
			return make_bad_decl(f, token, file_path);
		} else if (are_strings_equal(tag, make_string("thread_local"))) {
			AstNode *var_decl = parse_simple_stmt(f);
			if (var_decl->kind != AstNode_VarDecl ||
			    var_decl->VarDecl.kind != Declaration_Mutable) {
				ast_file_err(f, token, "#thread_local may only be applied to variable declarations");
				return make_bad_decl(f, token, ast_node_token(var_decl));
			}
			if (f->curr_proc != NULL) {
				ast_file_err(f, token, "#thread_local is only allowed at the file scope.");
				return make_bad_decl(f, token, ast_node_token(var_decl));
			}
			var_decl->VarDecl.tags |= VarDeclTag_thread_local;
			return var_decl;
		} else if (are_strings_equal(tag, make_string("bounds_check"))) {
			s = parse_stmt(f);
			s->stmt_state_flags |= StmtStateFlag_bounds_check;
			if ((s->stmt_state_flags & StmtStateFlag_no_bounds_check) != 0) {
				ast_file_err(f, token, "#bounds_check and #no_bounds_check cannot be applied together");
			}
			return s;
		} else if (are_strings_equal(tag, make_string("no_bounds_check"))) {
			s = parse_stmt(f);
			s->stmt_state_flags |= StmtStateFlag_no_bounds_check;
			if ((s->stmt_state_flags & StmtStateFlag_bounds_check) != 0) {
				ast_file_err(f, token, "#bounds_check and #no_bounds_check cannot be applied together");
			}
			return s;
		}


		s->TagStmt.stmt = parse_stmt(f); // TODO(bill): Find out why this doesn't work as an argument
		return s;
	} break;

	case Token_OpenBrace: return parse_block_stmt(f);

	case Token_Semicolon:
		s = make_empty_stmt(f, token);
		next_token(f);
		return s;
	}

	ast_file_err(f, token,
	             "Expected a statement, got `%.*s`",
	             LIT(token_strings[token.kind]));
	fix_advance_to_next_stmt(f);
	return make_bad_stmt(f, token, f->cursor[0]);
}

AstNodeArray parse_stmt_list(AstFile *f) {
	AstNodeArray list = make_ast_node_array(f);

	while (f->cursor[0].kind != Token_case &&
	       f->cursor[0].kind != Token_default &&
	       f->cursor[0].kind != Token_CloseBrace &&
	       f->cursor[0].kind != Token_EOF) {
		AstNode *stmt = parse_stmt(f);
		if (stmt && stmt->kind != AstNode_EmptyStmt) {
			gb_array_append(list, stmt);
		}
	}

	return list;
}



ParseFileError init_ast_file(AstFile *f, String fullpath) {
	if (!string_has_extension(fullpath, make_string("odin"))) {
		gb_printf_err("Only `.odin` files are allowed\n");
		return ParseFile_WrongExtension;
	}
	TokenizerInitError err = init_tokenizer(&f->tokenizer, fullpath);
	if (err == TokenizerInit_None) {
		gb_array_init(f->tokens, gb_heap_allocator());
		for (;;) {
			Token token = tokenizer_get_token(&f->tokenizer);
			if (token.kind == Token_Invalid)
				return ParseFile_InvalidToken;
			gb_array_append(f->tokens, token);

			if (token.kind == Token_EOF)
				break;
		}

		f->cursor = &f->tokens[0];

		// NOTE(bill): Is this big enough or too small?
		isize arena_size = gb_size_of(AstNode);
		arena_size *= 2*gb_array_count(f->tokens);
		gb_arena_init_from_allocator(&f->arena, gb_heap_allocator(), arena_size);

		f->curr_proc = NULL;

		return ParseFile_None;
	}

	switch (err) {
	case TokenizerInit_NotExists:
		return ParseFile_NotFound;
	case TokenizerInit_Permission:
		return ParseFile_Permission;
	case TokenizerInit_Empty:
		return ParseFile_EmptyFile;
	}

	return ParseFile_InvalidFile;
}

void destroy_ast_file(AstFile *f) {
	gb_arena_free(&f->arena);
	gb_array_free(f->tokens);
	gb_free(gb_heap_allocator(), f->tokenizer.fullpath.text);
	destroy_tokenizer(&f->tokenizer);
}

b32 init_parser(Parser *p) {
	gb_array_init(p->files, gb_heap_allocator());
	gb_array_init(p->imports, gb_heap_allocator());
	gb_array_init(p->libraries, gb_heap_allocator());
	gb_array_init(p->system_libraries, gb_heap_allocator());
	return true;
}

void destroy_parser(Parser *p) {
	// TODO(bill): Fix memory leak
	gb_for_array(i, p->files) {
		destroy_ast_file(&p->files[i]);
	}
#if 1
	gb_for_array(i, p->imports) {
		// gb_free(gb_heap_allocator(), p->imports[i].text);
	}
#endif
	gb_array_free(p->files);
	gb_array_free(p->imports);
	gb_array_free(p->libraries);
	gb_array_free(p->system_libraries);
}

// NOTE(bill): Returns true if it's added
b32 try_add_import_path(Parser *p, String path, TokenPos pos) {
	gb_for_array(i, p->imports) {
		String import = p->imports[i].path;
		if (are_strings_equal(import, path)) {
			return false;
		}
	}

	ImportedFile item;
	item.path = path;
	item.pos = pos;
	gb_array_append(p->imports, item);
	return true;
}

// NOTE(bill): Returns true if it's added
b32 try_add_foreign_system_library_path(Parser *p, String import_file) {
	gb_for_array(i, p->system_libraries) {
		String import = p->system_libraries[i];
		if (are_strings_equal(import, import_file)) {
			return false;
		}
	}
	gb_array_append(p->system_libraries, import_file);
	return true;
}

gb_global Rune illegal_import_runes[] = {
	'"', '\'', '`', ' ',
	'\\', // NOTE(bill): Disallow windows style filepaths
	'!', '$', '%', '^', '&', '*', '(', ')', '=', '+',
	'[', ']', '{', '}',
	';', ':', '#',
	'|', ',',  '<', '>', '?',
};

b32 is_import_path_valid(String path) {
	if (path.len > 0) {
		u8 *start = path.text;
		u8 *end = path.text + path.len;
		u8 *curr = start;
		Rune r = -1;
		while (curr < end) {
			isize width = 1;
			r = curr[0];
			if (r >= 0x80) {
				width = gb_utf8_decode(curr, end-curr, &r);
				if (r == GB_RUNE_INVALID && width == 1)
					return false;
				else if (r == GB_RUNE_BOM && curr-start > 0)
					return false;
			}

			for (isize i = 0; i < gb_count_of(illegal_import_runes); i++) {
				if (r == illegal_import_runes[i])
					return false;
			}

			curr += width;
		}

		return true;
	}
	return false;
}


void parse_file(Parser *p, AstFile *f) {
	String filepath = f->tokenizer.fullpath;
	String base_dir = filepath;
	for (isize i = filepath.len-1; i >= 0; i--) {
		if (base_dir.text[i] == GB_PATH_SEPARATOR)
			break;
		base_dir.len--;
	}

	f->decls = parse_stmt_list(f);

	gb_for_array(i, f->decls) {
		AstNode *node = f->decls[i];
		if (!is_ast_node_decl(node) &&
		    node->kind != AstNode_BadStmt &&
		    node->kind != AstNode_EmptyStmt) {
			// NOTE(bill): Sanity check
			ast_file_err(f, ast_node_token(node), "Only declarations are allowed at file scope");
		} else {
			if (node->kind == AstNode_ImportDecl) {
				auto *id = &node->ImportDecl;
				String file_str = id->relpath.string;

				if (!is_import_path_valid(file_str)) {
					ast_file_err(f, ast_node_token(node), "Invalid `load` path");
					continue;
				}

				isize str_len = base_dir.len+file_str.len;
				u8 *str = gb_alloc_array(gb_heap_allocator(), u8, str_len+1);
				defer (gb_free(gb_heap_allocator(), str));

				gb_memcopy(str, base_dir.text, base_dir.len);
				gb_memcopy(str+base_dir.len, file_str.text, file_str.len);
				str[str_len] = '\0';
				// HACK(bill): memory leak
				char *path_str = gb_path_get_full_name(gb_heap_allocator(), cast(char *)str);
				String import_file = make_string(path_str);

				id->fullpath = import_file;
				if (!try_add_import_path(p, import_file, ast_node_token(node).pos)) {
					// gb_free(gb_heap_allocator(), import_file.text);
				}
			} else if (node->kind == AstNode_ForeignSystemLibrary) {
				auto *id = &node->ForeignSystemLibrary;
				String file_str = id->filepath.string;

				if (!is_import_path_valid(file_str)) {
					ast_file_err(f, ast_node_token(node), "Invalid `foreign_system_library` path");
					continue;
				}

				try_add_foreign_system_library_path(p, file_str);
			}
		}
	}
}


ParseFileError parse_files(Parser *p, char *init_filename) {
	char *fullpath_str = gb_path_get_full_name(gb_heap_allocator(), init_filename);
	String init_fullpath = make_string(fullpath_str);
	TokenPos init_pos = {};
	ImportedFile init_imported_file = {init_fullpath, init_pos};
	gb_array_append(p->imports, init_imported_file);
	p->init_fullpath = init_fullpath;

	gb_for_array(i, p->imports) {
		String import_path = p->imports[i].path;
		TokenPos pos = p->imports[i].pos;
		AstFile file = {};
		ParseFileError err = init_ast_file(&file, import_path);
		if (err != ParseFile_None) {
			if (pos.line != 0) {
				gb_printf_err("%.*s(%td:%td) ", LIT(pos.file), pos.line, pos.column);
			}
			gb_printf_err("Failed to parse file: %.*s\n", LIT(import_path));
			switch (err) {
			case ParseFile_WrongExtension:
				gb_printf_err("\tInvalid file extension\n");
				break;
			case ParseFile_InvalidFile:
				gb_printf_err("\tInvalid file\n");
				break;
			case ParseFile_EmptyFile:
				gb_printf_err("\tFile is empty\n");
				break;
			case ParseFile_Permission:
				gb_printf_err("\tFile permissions problem\n");
				break;
			case ParseFile_NotFound:
				gb_printf_err("\tFile cannot be found\n");
				break;
			case ParseFile_InvalidToken:
				gb_printf_err("\tInvalid token found in file\n");
				break;
			}
			return err;
		}
		parse_file(p, &file);
		gb_array_append(p->files, file);
		p->total_token_count += gb_array_count(file.tokens);
	}


	return ParseFile_None;
}