typedef struct Expr Expr;
typedef struct Note Note;
typedef struct Stmt_If Stmt_If;
typedef struct Typespec Typespec;
typedef struct Decl_Enum_Child Decl_Enum_Child;
typedef struct Expr_Compound_Field Expr_Compound_Field;

typedef struct AST AST;
typedef struct AST_Parent AST_Parent;

//-----------------------------------------------------------------------------
// Expressions
//-----------------------------------------------------------------------------
typedef enum Expr_Sizeof_Kind{
  SIZEOF_Expr,
  SIZEOF_Type,
}Expr_Sizeof_Kind;

typedef enum Expr_Kind{
  EK_None,
  EK_Int,
  EK_String,
  EK_Identifier,
  EK_Compound,
  EK_Paren, 
  EK_PostfixUnary, 
  EK_Unary, 
  EK_Binary, 
  EK_Ternary,
  EK_Cast,
  EK_Field,
  EK_Call, 
  EK_Index,
  EK_SizeType,
  EK_SizeExpr,
} Expr_Kind;

typedef enum Expr_Compound_Kind{
  COMPOUND_None,
  COMPOUND_Default,
  COMPOUND_Named,
  COMPOUND_Index,
}Expr_Compound_Kind;

struct Expr_Compound_Field{
  Expr_Compound_Field *next;
  Expr_Compound_Kind kind;
  Token *pos;
  Expr *init;
  union{
    Expr *index;
    Intern_String name;
  };
};

struct Expr {
  Expr_Kind kind;
  Token *token;
  Expr  *next;
  union {
    U64 int_val;
    Intern_String intern_val;
    double float_val;
    struct {
      Expr *expr;
    } paren;
    struct {
      Typespec *typespec;
      Expr* expr;
    } cast;
    struct{
      Intern_String name;
      Expr *expr;
    }field;
    
    struct{
      Typespec *typespec;
      Expr_Compound_Field *first;
      Expr_Compound_Field *last;
    }compound;
    
    struct {
      Expr *atom;
      Expr_Compound_Field *first;
      Expr_Compound_Field *last;
    } call;
    struct{
      
    }arg;
    struct {
      Expr *atom;
      Expr *index;
    } index;
    
    struct {
      Token_Kind op;
      Expr* expr;
    } unary;
    struct {
      Token_Kind op;
      Expr *expr;
    } postfix_unary;
    struct {
      Token_Kind op;
      Expr* left;
      Expr* right;
    } binary;
    struct {
      Expr* cond;
      Expr* on_true;
      Expr* on_false;
    } ternary;
    
    struct{
      Typespec *typespec;
    } size_type;
    
    struct{
      Expr *expr;
    } size_expr;
  };
};

//-----------------------------------------------------------------------------
// Type specifiers
//-----------------------------------------------------------------------------
typedef enum Typespec_Kind{
  TS_None,
  TS_Name,
  TS_Pointer,
  TS_Array,
  TS_Function,
  TS_NamedArgument,
}Typespec_Kind;

struct Typespec{
  Typespec *next;
  Typespec_Kind kind;
  Token *pos;
  union{
    Typespec *base;
    Intern_String name;
    struct{
      Intern_String name;
      Typespec *base;
    }named;
    struct{
      Typespec *first;
      Typespec *last;
      Typespec *ret;
    }func;
    struct{
      Typespec *base;
      Expr     *size;
    }arr;
  };
};

//-----------------------------------------------------------------------------
// Abstract Syntax Tree, declarations, statements all in one
//-----------------------------------------------------------------------------
typedef enum AST_Kind:U32{
  AST_None,
  AST_Decl_Enum_Child,
  AST_Decl_Var,
  AST_Decl_Const,
  AST_Decl_Typedef,
  AST_Decl_Func_Arg,
  AST_Decl_Variable,
  AST_Stmt_ElseIf,
  AST_Stmt_Else,
  AST_Stmt_Init,
  AST_Stmt_Expr,
  AST_Stmt_Assign,
  AST_Stmt_Return,
  AST_Stmt_For, 
  AST_Stmt_Defer,
  
  AST_Decl_Struct, // First Parent, First Struct
  AST_Decl_SubStruct,
  AST_Decl_SubUnion,
  AST_Decl_Union, //                Last Struct
  AST_Decl_Enum,
  AST_Decl_Func, 
  AST_Note,
  AST_Note_List,
  AST_Stmt_Block,
  AST_Stmt_If,
  AST_Stmt_Decl,
  AST_Program,// Last Parent
  AST_FirstParent = AST_Decl_Struct,
  AST_LastParent = AST_Program,
  AST_FirstStruct = AST_Decl_Struct,
  AST_LastStruct = AST_Decl_Union,
}AST_Kind;

typedef enum AST_Flags{
  AST_Flags_None,
  AST_Flags_Ordered = 1
}AST_Flags;

//-----------------------------------------------------------------------------
// Inheritence like macro helpers
//-----------------------------------------------------------------------------
// AST        - 48 Bytes 
// AST_Parent - 64 Bytes 
#define AST_FIELDS AST_Kind kind; AST_Flags flags; AST *next, *prev; AST_Parent *notes; AST_Parent *parent; Token *pos
#define AST_PARENT_FIELDS AST *first, *last
#define AST_UNION union{ struct{ AST_FIELDS; }; AST ast; }
#define AST_PARENT_UNION union{ struct{ AST_FIELDS; AST_PARENT_FIELDS; }; AST_Parent child; }

//-----------------------------------------------------------------------------
// Base classes
//-----------------------------------------------------------------------------
struct AST{AST_FIELDS;};
typedef struct AST_Parent{
  AST_UNION;
  AST_PARENT_FIELDS;
} AST_Parent;

//-----------------------------------------------------------------------------
// Declarations
//-----------------------------------------------------------------------------
typedef AST_Parent Note_List;
typedef AST_Parent Program;

typedef struct Note{
  AST_PARENT_UNION;
  Intern_String name;
  Expr *expr;
}Note;

typedef struct Decl_Struct{
  AST_PARENT_UNION;
  Intern_String name;
}Decl_Struct;

typedef struct Decl_Func_Arg{
  AST_UNION;
  Intern_String name;
  Typespec *typespec;
}Decl_Func_Arg;

typedef struct Decl_Enum_Child{
  AST_UNION;
  Intern_String name;
  Expr *expr;
}Decl_Enum_Child;

typedef struct Decl_Enum{
  AST_PARENT_UNION;
  Typespec *typespec;
  Intern_String name;
}Decl_Enum;

typedef AST_Parent Stmt_Block;
typedef struct Decl_Func{
  AST_PARENT_UNION;
  Intern_String name;
  Typespec *ret;
  Stmt_Block *body;
  B32 is_incomplete;
}Decl_Func;

typedef struct Decl_Typedef{
  AST_PARENT_UNION;
  Typespec *typespec;
  Intern_String name;
}Decl_Typedef;

typedef struct Decl_Var{
  AST_PARENT_UNION;
  Typespec *typespec;
  Intern_String name;
  Expr *expr;
}Decl_Var;

typedef struct Decl_Const{
  AST_PARENT_UNION;
  Typespec *typespec;
  Intern_String name;
  Expr *expr;
}Decl_Const;

//-----------------------------------------------------------------------------
// Statements
//-----------------------------------------------------------------------------
typedef Stmt_If Stmt_If;
struct Stmt_If{
  AST_PARENT_UNION;
  Expr        *condition;
  Stmt_Block  *body;
};

typedef struct Stmt_ElseIf{
  AST_UNION;
  Expr *condition;
  Stmt_Block *body;
}Stmt_ElseIf;

typedef struct Stmt_Else{
  AST_UNION;
  Stmt_Block *body;
}Stmt_Else;

typedef struct Stmt_Return{
  AST_UNION;
  Expr *expr;
} Stmt_Return;

typedef struct Stmt_Init{
  AST_UNION;
  Intern_String name;
  Typespec *typespec;
  Expr *expr;
}Stmt_Init;

typedef struct Stmt_Assign{
  AST_UNION;
  Token_Kind op;
  Expr *left;
  Expr *right;
}Stmt_Assign;

typedef struct Stmt_Expr{
  AST_UNION;
  Expr *expr;
}Stmt_Expr;

typedef struct Stmt_Defer{
  AST_UNION;
  Stmt_Block *body;
}Stmt_Defer;

typedef struct Stmt_For{
  AST_UNION;
  AST *on_begin;
  Expr*condition;
  AST *on_iter;
  Stmt_Block *body;
}Stmt_For;

//-----------------------------------------------------------------------------
// Expression constructors
//-----------------------------------------------------------------------------
function Expr *
expr_new(Arena *p, Expr_Kind kind, Token *token){
  Expr *expr = arena_push_struct(p, Expr);
  expr->kind = kind;
  expr->token = token;
  return expr;
}

function Expr *
expr_int(Arena *p, Token *token){
  assert(token->kind == TK_Integer);
  Expr *expr = expr_new(p, EK_Int, token);
  expr->int_val = token->int_val;
  return expr;
}

function Expr *
expr_str(Arena *p, Token *token){
  assert(token->kind == TK_StringLit);
  Expr *expr = expr_new(p, EK_String, token);
  expr->intern_val = token->intern_val;
  return expr;
}

function Expr *
expr_identifier(Arena *p, Token *token){
  assert(token->kind == TK_Identifier);
  Expr *expr = expr_new(p, EK_Identifier, token);
  expr->intern_val = token->intern_val;
  return expr;
}

function Expr *
expr_field(Arena *p, Token *token, Expr *inexpr){
  assert(token->kind == TK_Identifier);
  Expr *expr = expr_new(p, EK_Field, token);
  expr->field.expr = inexpr;
  expr->field.name = token->intern_val;
  return expr;
}

function Expr *
expr_paren(Arena *p, Token *token, Expr *inexpr){
  Expr *expr = expr_new(p, EK_Paren, token);
  expr->paren.expr = inexpr;
  return expr;
}

function Expr *
expr_postfix_unary(Arena *p, Token *op, Expr *exp){
  Expr *expr = expr_new(p, EK_PostfixUnary, op);
  expr->unary.op = op->kind;
  expr->unary.expr = exp;
  return expr;
}

function Expr *
expr_unary(Arena *p, Token *op, Expr *exp){
  Expr *expr = expr_new(p, EK_Unary, op);
  expr->unary.op = op->kind;
  expr->unary.expr = exp;
  return expr;
}

function Expr *
expr_binary(Arena *p, Token *op, Expr *left, Expr *right){
  Expr *expr = expr_new(p, EK_Binary, op);
  expr->binary.op = op->kind;
  expr->binary.left = left;
  expr->binary.right = right;
  return expr;
}

function Expr *
expr_ternary(Arena *p, Token *op, Expr *cond, Expr *on_true, Expr *on_false){
  Expr *expr = expr_new(p, EK_Ternary, op);
  expr->ternary.cond = cond;
  expr->ternary.on_true = on_true;
  expr->ternary.on_false = on_false;
  return expr;
}

function Expr *
expr_call(Arena *p, Token *token, Expr *atom){
  Expr *expr = expr_new(p, EK_Call, token);
  expr->call.atom = atom;
  return expr;
}

function Expr *
expr_index(Arena *p, Token *token, Expr *atom, Expr *index){
  Expr *expr = expr_new(p, EK_Index, token);
  expr->index.atom = atom;
  expr->index.index = index;
  return expr;
}

function Expr *
expr_cast(Arena *p, Token *token, Typespec *type, Expr *exp){
  Expr *expr = expr_new(p, EK_Cast, token);
  expr->cast.typespec = type;
  expr->cast.expr = exp;
  return expr;
}

function Expr *
expr_size_type(Arena *p, Token *token, Typespec *type){
  Expr *expr = expr_new(p, EK_SizeType, token);
  expr->size_type.typespec = type;
  return expr;
}

function Expr *
expr_sizeof_expr(Arena *p, Token *token, Expr *in_expr){
  Expr *expr = expr_new(p, EK_SizeExpr, token);
  expr->size_expr.expr = in_expr;
  return expr;
}

function Expr *
expr_compound(Arena *arena, Token *pos, Typespec *typespec){
  Expr *result = expr_new(arena, EK_Compound, pos);
  result->compound.typespec = typespec;
  return result;
}

function Expr_Compound_Field *
expr_compound_new(Arena *arena, Expr_Compound_Kind kind, Token *pos, Expr *init){
  Expr_Compound_Field *result = arena_push_struct(arena, Expr_Compound_Field);
  result->kind = kind;
  result->pos = pos;
  result->init = init;
  return result;
}

function Expr_Compound_Field *
expr_compound_default(Arena *arena, Token *pos, Expr *init){
  Expr_Compound_Field *result = expr_compound_new(arena, COMPOUND_Default, pos, init);
  return result;
}

function Expr_Compound_Field *
expr_compound_named(Arena *arena, Token *pos, Intern_String name, Expr *init){
  Expr_Compound_Field *result = expr_compound_new(arena, COMPOUND_Named, pos, init);
  result->name = name;
  return result;
}

function Expr_Compound_Field *
expr_compound_index(Arena *arena, Token *pos, Expr *index, Expr *init){
  Expr_Compound_Field *result = expr_compound_new(arena, COMPOUND_Index, pos, init);
  result->index = index;
  return result;
}

function void
expr_call_push(Expr *list, Expr_Compound_Field *field){
  SLLQueuePush(list->call.first, list->call.last, field);
}

function void
expr_compound_push(Expr *list, Expr_Compound_Field *field){
  SLLQueuePush(list->compound.first, list->compound.last, field);
}

//-----------------------------------------------------------------------------
// Type specifier constructors
//-----------------------------------------------------------------------------
function Typespec *
typespec_new(Arena *p, Typespec_Kind kind, Token *pos){
  Typespec *result = arena_push_struct(p, Typespec);
  result->kind = kind;
  result->pos = pos;
  return result;
}

function Typespec *
typespec_name(Arena *p, Token *pos, Intern_String name){
  Typespec *result = typespec_new(p, TS_Name, pos);
  result->name = name;
  return result;
}

function Typespec *
typespec_pointer(Arena *p, Token *pos, Typespec *base){
  Typespec *result = typespec_new(p, TS_Pointer, pos);
  result->base = base;
  return result;
}

function Typespec *
typespec_array(Arena *p, Token *pos, Typespec *base, Expr *size){
  Typespec *result = typespec_new(p, TS_Array, pos);
  result->arr.base = base;
  result->arr.size = size;
  return result;
}

function Typespec *
typespec_function(Arena *p, Token *pos, Typespec *ret){
  Typespec *result = typespec_new(p, TS_Function, pos);
  result->func.ret = ret;
  return result;
}

function Typespec *
typespec_named_argument(Arena *arena, Token *pos, Typespec *typespec, Intern_String name){
  Typespec *result = typespec_new(arena, TS_NamedArgument, pos);
  result->named.base = typespec;
  result->named.name = name;
  return result;
}

function void
typespec_function_push(Typespec *func, Typespec *arg){
  SLLQueuePush(func->func.first, func->func.last, arg);
}

//-----------------------------------------------------------------------------
// Double linked list
//-----------------------------------------------------------------------------

function void 
ast_remove(AST *node){
  AST_Parent *l = node->parent;
  assert(l);
  if (l->first==l->last){
    assert(node==l->last);
    l->first=l->last=0;
  }
  else if (l->last==node){
    l->last=l->last->prev;
    l->last->next=0;
  }
  else if (l->first==node){
    l->first=l->first->next;
    l->first->prev=0;
  }
  else {
    node->prev->next=node->next;
    node->next->prev=node->prev;
  }
  node->parent=0;
  node->prev=0;
  node->next=0;
}

function void 
ast_push_last(AST_Parent *l, AST *node){
  if (l->first==0){
    l->first=l->last=node;
    node->prev=0;
    node->next=0;
  }
  else {
    l->last->next=node;
    node->prev=l->last;
    node->next=0;
    l->last=node;
  }
  node->parent=l;
}

function void 
ast_push_first(AST_Parent *l, AST *node){
  if(l->first == 0){
    l->first = l->last = node;
    node->prev = 0;
    node->next = 0;
  }
  else {
    node->next = l->first;
    l->first->prev = node;
    node->prev = 0;
    l->first = node;
  }
  node->parent = l;
}

function void
ast_push_after(AST *in_list, AST *node){
  AST_Parent *parent = in_list->parent;
  assert(parent);
  assert(parent->first && parent->last);
  
  node->prev = in_list;
  if(in_list == parent->last){
    in_list->next = node;
    parent->last = node;
  }
  else {
    node->next = in_list->next;
    in_list->next = node;
    node->next->prev = node;
  }
  node->parent=parent;
}

function void
ast_push_before(AST *in_list, AST *node){
  AST_Parent *parent = in_list->parent;
  assert(parent);
  assert(parent->first && parent->last);
  
  node->next = in_list;
  if(parent->first == in_list){
    in_list->prev = node;
    parent->first = node;
  }
  else{
    node->prev = in_list->prev;
    in_list->prev = node;
    node->prev->next = node;
  }
  node->parent = parent;
}

//-----------------------------------------------------------------------------
// AST Constructors
//-----------------------------------------------------------------------------
#define ast_parent_new(arena, T, pos) (T *)ast__parent_new(arena, sizeof(T), AST_##T, pos)
#define ast_new(arena, T, pos) (T *)ast__new(arena, sizeof(T), AST_##T, pos)

function B32
ast_kind_is_parent(AST_Kind kind){
  B32 result = kind >= AST_FirstParent && kind <= AST_LastParent;
  return result;
}

function B32
ast_kind_is_struct(AST_Kind kind){
  B32 result = kind >= AST_FirstStruct && kind <= AST_LastStruct;
  return result;
}

function AST *
ast__new(Arena *p, SizeU size, AST_Kind kind, Token *pos){
  assert(!ast_kind_is_parent(kind));
  AST *result = arena_push_size(p, size);
  result->pos  = pos;
  result->kind = kind;
  return result;
}

function AST_Parent *
ast__parent_new(Arena *p, SizeU size, AST_Kind kind, Token *pos){
  assert(ast_kind_is_parent(kind));
  AST_Parent *result = arena_push_size(p, size);
  result->pos  = pos;
  result->kind = kind;
  return result;
}

//-----------------------------------------------------------------------------
// Notes
//-----------------------------------------------------------------------------

function Note *
note_push_new(Arena *p, AST_Parent *parent, Token *pos, Intern_String name, Expr *expr){
  Note *result = ast_parent_new(p, Note, pos);
  result->name = name;
  result->expr = expr;
  ast_push_last(parent, (AST *)result);
  return result;
}

function Note_List *
note_list(Arena *p, Token *pos){
  Note_List *result = ast_parent_new(p, Note_List, pos);
  return result;
}

#define ast_push_copy(a,p,T) arena_push_copy(a, p, sizeof(T))
function AST *
ast_shallow_copy(Arena *a, AST *ast){
  AST *result = 0;
  switch(ast->kind){
    case AST_Note_List: {
      result = ast_push_copy(a, ast, Note_List);
    } break;
    default: invalid_codepath;
  }
  return result;
}

//-----------------------------------------------------------------------------
// Declarations
//-----------------------------------------------------------------------------
function Decl_Struct *
decl_struct(Arena *p, AST_Kind kind, Token *pos, Intern_String name){
  assert(ast_kind_is_struct(kind));
  Decl_Struct *result = ast_parent_new(p, Decl_Struct, pos);
  result->name = name;
  return result;
}

function Decl_Typedef *
decl_typedef(Arena *p, Token *pos, Intern_String name, Typespec *type){
  Decl_Typedef *result = ast_new(p, Decl_Typedef, pos);
  result->typespec = type;
  result->name = name;
  return result;
}

function Decl_Const *
decl_const(Arena *arena, Token *pos, Intern_String name, Expr *expr, Typespec *typespec){
  Decl_Const *result = ast_new(arena, Decl_Const, pos);
  result->expr = expr;
  result->name = name;
  result->typespec = typespec;
  return result;
}

function Decl_Enum *
decl_enum(Arena *p, Token *pos, Intern_String name, Typespec *typespec){
  Decl_Enum *result = ast_parent_new(p, Decl_Enum, pos);
  result->name = name;
  result->typespec = typespec;
  return result;
}

function Decl_Var *
decl_variable(Arena *arena, Token *pos, Intern_String name, Expr *expr, Typespec *typespec, Note_List *notes){
  Decl_Var *result = ast_new(arena, Decl_Var, pos);
  result->expr = expr;
  result->name = name;
  result->typespec = typespec;
  result->notes = notes;
  return result;
}

function Decl_Func *
decl_function(Arena *p, Token *pos, Intern_String name, Typespec *ret){
  Decl_Func *result = ast_parent_new(p, Decl_Func, pos);
  result->ret = ret;
  result->name = name;
  return result;
}

function Decl_Func_Arg *
decl_func_arg(Arena *arena, Token *pos, Intern_String name, Typespec *type){
  Decl_Func_Arg *result = ast_new(arena, Decl_Func_Arg, pos);
  result->name = name;
  result->typespec = type;
  return result;
}

function Decl_Enum_Child *
decl_enum_child(Arena *p, Token *pos, Intern_String name, Expr *expr, Note_List *note){
  Decl_Enum_Child *result = ast_new(p, Decl_Enum_Child, pos);
  result->name = name;
  result->expr = expr;
  result->notes = (AST_Parent *)note;
  return result;
}

function void
decl_func_push(Arena *p, Decl_Func *parent, Token *pos, Intern_String name, Typespec *type){
  assert(parent->kind == AST_Decl_Func);
  Decl_Func_Arg *func_arg = decl_func_arg(p, pos, name, type);
  ast_push_last((AST_Parent *)parent, (AST *)func_arg);
}

function void
decl_enum_push(Arena *p, Decl_Enum *parent, Token *pos, Intern_String name, Expr *expr, Note_List *notes){
  assert(parent->kind == AST_Decl_Enum);
  Decl_Enum_Child *child = decl_enum_child(p, pos, name, expr, notes);
  ast_push_last((AST_Parent *)parent, (AST *)child);
}

function void
decl_struct_push(Decl_Struct *parent, AST *child){
  assert(ast_kind_is_struct(parent->kind));
  ast_push_last((AST_Parent *)parent, child);
}

function Program *
ast_program(Arena *arena, Token *token){
  Program *result = ast_parent_new(arena, Program, token);
  return result;
}

function void
ast_program_push(AST_Parent *parent, AST *child){
  assert(parent->kind == AST_Program);
  ast_push_last((AST_Parent *)parent, child);
}

//-----------------------------------------------------------------------------
// Statements
//-----------------------------------------------------------------------------
function Stmt_Block *
stmt_block(Arena *arena, Token *pos){
  Stmt_Block *result = ast_parent_new(arena, Stmt_Block, pos);
  return result;
}

function Stmt_If *
stmt_if(Arena *arena, Token *pos, Expr *condition){
  Stmt_If *result = ast_parent_new(arena, Stmt_If, pos);
  result->condition = condition;
  result->body = stmt_block(arena, pos);
  return result;
}

function Stmt_ElseIf *
stmt_else_if_push(Arena *arena, Stmt_If *parent, Token *pos, Expr *condition){
  Stmt_ElseIf *result = ast_new(arena, Stmt_ElseIf, pos);
  result->condition   = condition;
  result->body        = stmt_block(arena, pos);
  ast_push_last((AST_Parent *)parent, (AST *)result);
  return result;
}

function Stmt_Else *
stmt_else_push(Arena *arena, Stmt_If *parent, Token *pos){
  Stmt_Else *result = ast_new(arena, Stmt_Else, pos);
  result->body      = stmt_block(arena, pos);
  ast_push_last((AST_Parent *)parent, (AST *)result);
  return result;
}

function Stmt_Init *
stmt_init(Arena *arena, Token *pos, Intern_String name, Typespec *typespec, Expr *expr){
  Stmt_Init *result = ast_new(arena, Stmt_Init, pos);
  result->typespec = typespec;
  result->expr = expr;
  result->name = name;
  return result;
}

function Stmt_Assign *
stmt_assign(Arena *arena, Token *pos, Token_Kind op, Expr *left, Expr *right){
  Stmt_Assign *result = ast_new(arena, Stmt_Assign, pos);
  result->op = op;
  result->left = left;
  result->right = right;
  return result;
}

function Stmt_Expr *
stmt_expr(Arena *arena, Token *pos, Expr *expr){
  Stmt_Expr *result = ast_new(arena, Stmt_Expr, pos);
  result->expr = expr;
  return result;
}

function Stmt_Return *
stmt_return(Arena *arena, Token *pos, Expr *expr){
  Stmt_Return *result = ast_new(arena, Stmt_Return, pos);
  result->expr = expr;
  return result;
}

function Stmt_For *
stmt_for(Arena *arena, Token *pos, Token *pos_block, AST *on_begin, Expr *condition, AST *on_iter){
  Stmt_For *result = ast_new(arena, Stmt_For, pos);
  result->on_iter   = on_iter;
  result->on_begin  = on_begin;
  result->condition = condition;
  result->body      = stmt_block(arena, pos_block);
  return result;
}

function Stmt_Defer *
stmt_defer(Arena *arena, Token *pos){
  Stmt_Defer *result = ast_new(arena, Stmt_Defer, pos);
  result->body = stmt_block(arena, pos);
  return result;
}

//-----------------------------------------------------------------------------
// Test stuff
//-----------------------------------------------------------------------------
function void
list_print(AST_Parent *decls){
  printf("\n");
  printf("next:");
  for(AST *n = decls->first; n; n=n->next){
    printf("%d", n->kind);
  }
  printf("prev:");
  for(AST *n = decls->last; n; n=n->prev){
    printf("%d", n->kind);
  }
  printf("parent:");
  for(AST *n = decls->first; n; n=n->next){
    printf("%d", n->parent->kind);
  }
}

function void
ast_test(){
  printf("\nAST_Size = %u", (U32)sizeof(AST));
  printf("\nAST_Parent_Size = %u", (U32)sizeof(AST_Parent));
  printf("\nAST_Struct_Size = %u", (U32)sizeof(Decl_Struct));
  printf("\nAST_Func_Size = %u", (U32)sizeof(Decl_Func));
  
  AST_Parent parent = {0};
  AST decls[16] = {0};
  parent.kind = 0;
  for(int i = 0; i < buff_cap(decls); i++){
    decls[i].kind = i+1;
  }
  
  ast_push_last(&parent, decls);
  ast_push_last(&parent, decls+1);
  ast_push_last(&parent, decls+2);
  //ast_push_before(decls, decls+3);
  //ast_push_before(decls, decls+4);
  //ast_push_after(decls, decls+5);
  //ast_push_after(decls+5, decls+6);
  
  list_print(&parent);
  /* 
    ast_remove(decls);
    ast_remove(decls+1);
    ast_remove(decls+2);
    ast_remove(decls+3);
    ast_remove(decls+4);
    ast_remove(decls+5);
    ast_remove(decls+6);
    assert(parent.first == 0);
    assert(parent.last  == 0);
   */
}