import "mem.hff";
import "util.hff";
import "vec.hff";
import "map.hff";
import "cffc.hff";

///////////
// Lexer //
///////////

fn chr(P *Parser) int {
   let c int #?;
   switch P.peekchr {
   case Some pc;
      c = pc;
      P.peekchr = :None;
   case None;
      c = fgetc(P.fp);
   }
   
   ++P.curloc.idx;
   ++P.curloc.col;
   if c == '\n' {
      P.curloc.col = 1;
      ++P.curloc.line;
   }
   if c == EOF {
      P.eof = #t;
   }
   return c;
}

fn chrpeek(P *Parser) int {
   switch P.peekchr {
   case Some c; return c;
   }
   let c = fgetc(P.fp);
   if c == EOF {
      P.eof = #t;
   }
   P.peekchr = :Some(c);
   return c;
}

fn chrmatch(P *Parser, c int) bool {
   if chrpeek(P) == c {
      chr(P);
      return #t;
   }
   return #f;
}

fn isspace(c u8) bool {
   switch c {
   case ' ',  '\t', '\n', '\r', '\v', '\f';
        return #t;
   }
   return #f;
}

fn isdigit(c u8) bool {
   return c >= '0' and c <= '9';
}

fn isxdigit(c u8) bool {
   return isdigit(c)
       or (c >= 'A' and c <= 'F')
       or (c >= 'a' and c <= 'f');
}

fn isalpha(c u8) bool {
   return (c >= 'a' and c <= 'z')
       or (c >= 'A' and c <= 'Z');
}

fn issep(c u8) bool {
   if isspace(c) {
      return #t;
   }
   switch (c) {
   case '(', ')', '[', ']', '{', '}', '.', ',',
        ';', '?', '+', '-', '*', '/', '&', '|',
        '^', '~', '=', '\'', '"', '<', '>', ':',
        '@', '#', '\\', '`';
      return #t;
   }
   return #f;
}

fn ishsep(c u8) bool {
   if isspace(c) {
      return #t;
   }
   switch (c) {
   case '(', ')', '[', ']', '{',
        '}', '.', ',', ';', '"';
      return #t;
   }
   return #f;
}

fn readtilsep(P *Parser, buf [#]u8, dot bool) int {
   let i = 0,
       c u8 #?;
   while (!issep(c = chrpeek(P))) or (dot and c == '.') {
      chr(P);
      if i >= buf.#len - 1 {
         return -1;
      }
      buf[i++] = c;
   }
   buf[i++] = 0;
   return i;
}

fn readtilhsep(P *Parser, buf [#]u8, dot bool) int {
   let i = 0,
       c u8 #?,
       pred = &ishsep;
   while (!pred(c = chrpeek(P))) or (dot and c == '.') {
      chr(P);
      if !issep(c) {
         pred = &issep;
      }
      if i >= buf.#len - 1 {
         return -1;
      }
      buf[i++] = c;
   }
   buf[i++] = 0;
   return i;
}

fn eatspaces(P *Parser) void {
   for ;;chr(P) {
      if !isspace(chrpeek(P)) {
         break;
      }
   }
}

// !sorted
extern static keyword2str [NUM_KEYWORDS]*const u8 = {
   "and", "as", "break", "case", "const",
   "continue", "def", "defmacro", "do",
   "else", "enum", "extern", "fn",
   "for", "if", "import", "let",
   "or", "return", "sizeof", "static",
   "struct", "switch", "typedef", "typeof",
   "union", "while",
};

fn str2keyword(s *const u8) int {
   let i = 0zs,
       j = keyword2str.#len - 1;
   while i <= j {
      let k = (j + i) / 2;
      let cmp = strcmp(keyword2str[k], s);
      if cmp == 0 {
         return k;
      } else if cmp < 0 {
         i = k + 1;
      } else {
         j = k - 1;
      }
   }
   return -1;
}

fn xdigit2num(c u8) int {
   switch {
   case isdigit(c); return c - '0';
   case c >= 'a' and c <= 'f'; return (c - 'a') + 10;
   case c >= 'A' and c <= 'F'; return (c - 'A') + 10;
   }
   return -1;
}

fn readnumber(s *const u8) Option<Tok> {
   let c u8 #?,
       acc = 0u64,
       accf = 0.0f64,
       fmul = 0.1,
       base = 10,
       flt = #f,
       nused = 0,
       suffix *const u8 = #null;

   for let i = 0; (c = s[i]) != 0; ++i {
      if i == 0 and c == '0' {
         --nused;
      }
      if i == 1 and tolower(c) == 'x' {
         base = 16;
         continue;
      }
      if !flt and c == '.' and base == 10 {
         flt = #t;
         accf = acc;
         continue;
      }
      if nused > 0 and c == '_' { continue; }
      if (base == 16 and !isxdigit(c))
       or (base != 16 and (c < '0' or c > ('0' + base) - 1)) {
         suffix = s + i;
      }

      ++nused;
      if flt {
         accf = accf + ((c - '0') * fmul);
         fmul *= 0.1;
      } else {
         acc = (acc * base) + xdigit2num(c);
      }
   }

   let tok = Tok {};
   if flt {
      tok.t = :flo;
      tok.u.flo = accf;
      
      switch {
      case suffix == #null;        tok.ty = ty_f64;
      case strcieq(suffix,   "f"); tok.ty = ty_f32;
      case strcieq(suffix, "f32"); tok.ty = ty_f32;
      case strcieq(suffix, "f64"); tok.ty = ty_f64;
      case else; return :None;
      }
      
      return :Some(tok);
   } else {
      tok.t = :int;
      tok.u.uint = acc;

      fn ty4intX(i u64) *const Type {
         if i < 1u64 << ((g_targ.intsize * 8) - 1) {
            return ty_int;
         }
         if i < 1u64 << 31 {
            return ty_i32;
         }
         if i < 1u64 << 63 {
            return ty_i64;
         }
         return ty_u64;
      }

      fn ty4uintX(i u64) *const Type {
         if i < 1u64 << (g_targ.intsize * 8) {
            return ty_uint;
         }
         if i < 1u64 << 32 {
            return ty_u32;
         }
         return ty_u64;
      }
      
      switch {
      case suffix == #null;        tok.ty = ty4intX(tok.u.uint);
      case strcieq(suffix,   "u"); tok.ty = ty4uintX(tok.u.uint);
      case strcieq(suffix,  "u8"); tok.ty = ty_u8;
      case strcieq(suffix,  "i8"); tok.ty = ty_i8;
      case strcieq(suffix, "u16"); tok.ty = ty_u16;
      case strcieq(suffix, "i16"); tok.ty = ty_i16;
      case strcieq(suffix, "u32"); tok.ty = ty_u32;
      case strcieq(suffix, "i32"); tok.ty = ty_i32;
      case strcieq(suffix, "u64"); tok.ty = ty_u64;
      case strcieq(suffix, "i64"); tok.ty = ty_i64;
      case strcieq(suffix,   "z"); tok.ty = ty_usize;
      case strcieq(suffix,  "zs"); tok.ty = ty_isize;
      case strcieq(suffix,   "p"); tok.ty = ty_uptrint;
      case strcieq(suffix,  "ps"); tok.ty = ty_iptrint;
      case else; return :None;
      }

      return :Some(tok);
   }
}

def MAX_MACROEXPAND_ITER = 100;

fn lex(P *Parser) Tok {
   let c int #?;
   let tok Tok = {};

   switch P.peektok {
   case Some pt;
      P.peektok = :None;
      return pt;
   }

   if P.expanno > MAX_MACROEXPAND_ITER {
      fatal(P, P.curloc, "maximum number of nested macro expansions reached (infinite recursion?)");
   }
   if P.curexpan {
      let ep = P.curexpan;
      if ep.idx == ep.toks.#len {
         // end macro expansion
         --P.expanno;
         free(ep.args.#ptr);
         P.curexpan = ep.prev;
         P.peektok = ep.peektok;
         free(ep);
         return lex(P);
      }
      tok = ep.toks[ep.idx++];
      // expand macro arg?
      if tok.t == :macident {
         for let ep = P.curexpan; ep; ep = ep.prev {
            foreach(arg, i, ep.args) {
               if streq(tok.u.ident, arg.name) {
                  ++P.expanno;
                  P.curexpan = memcpy(xmalloc(sizeof Expan), &Expan {
                     P.curexpan, {}, arg.toks,
                  }, sizeof Expan);
                  return lex(P);
               }
            }
         }
      } else if tok.t == '#FIL' or tok.t == '#LIN' {
         let ep *Expan #?;
         for ep = P.curexpan; ep.prev; ep = ep.prev { }
         if tok.t == '#FIL' {
            return { :str, tok.loc, .u: { .str: spanz(fileid2path(ep.loc.fileid)) }};
         } else {
            return { :int, tok.loc, .u: { .int: ep.loc.line }};
         }
      }
      return tok;
   }

   eatspaces(P);
   tok.loc = (P.tokloc = P.curloc);
   if isdigit(c = chrpeek(P)) {
      let s [80]u8 = {};
      if readtilsep(P, s[0::], #t) < 0 {
         fatal(P, tok.loc, "bad number literal");
      }
      switch readnumber(s) {
      case None;
         fatal(P, tok.loc, "bad number literal %qs", s);
      case Some tok;
         tok.loc = P.tokloc;
         return tok;
      }
   }
   if isalpha(c) or c == '_' or c == '$' or c > 0x7F {
      let s [120]u8;
      if readtilsep(P, s[0::], #f) < 0 {
         fatal(P, tok.loc, "identifier too long");
      }
      let kw = str2keyword(s);
      if kw >= 0 {
         tok.t = kw;
         tok.u.ident = keyword2str[kw];
      } else if (c == '$') {
         tok.t = :gensym;
         tok.u.ident = internstr(&s[1]);
      } else {
         tok.t = :ident;
         tok.u.ident = internstr(s);
      }
      return tok;
   }
   if c == '#' {
      let s [100]u8 = {};
      if readtilhsep(P, s[0::], #f) < 0 {
         fatal(P, P.tokloc, "invalid #keyword");
      }
      switch {
      case streq(s, "#") and chrpeek(P) == '{';
         chr(P);
         let bal = 1;
         while bal != 0 {
            switch lex(P).t {
            case '{'; ++bal;
            case '}'; --bal;
            case :eof; fatal(P, tok.loc, "unterminated comment");
            }
         }
         return lex(P);
      case streq(s, "#");
         tok.t = '#';
      case streq(s, "#t") or streq(s, "#f");
         tok.t = :bool;
         tok.u.bool = s[1] == 't';
      case streq(s, "#null");
         tok.t = :null;
      case streq(s, "##");
         tok.t = '##';
      case streq(s, "#len");
         tok.t = '#len';
      case streq(s, "#tag");
         tok.t = '#tag';
      case streq(s, "#?");
         tok.t = '#?';
      case s[0] == '#' and s[1] == '\'';
         tok.t = :label;
         tok.u.str = spanz(internstr(s));
      case else
         fatal(P, P.tokloc, "invalid #keyword `%s'", s);
      }
      return tok;
   }
   if c == '"' or c == '\'' {
      chr(P);
      let delim = c,
          str Vec<u8> = {},
          c u8 #?,
          i = 0z;
      while (c = chr(P)) != delim {
         if c == 0 or c == '\n' {
            fatal(P, P.tokloc, "unterminated %s literal",
                  delim == '"' ? "string" : "character");
         }
         if c != '\\' {
            str->push(c);
            continue;
         }
         switch ((c = chr(P))) {
         case 0, '\n';
            fatal(P, P.tokloc, "unterminated %s literal",
                  delim == '"' ? "string" : "character");
         case '\''; str->push('\''); case '\\'; str->push('\\');
         case  '"'; str->push('"');  case  'n'; str->push('\n');
         case  'r'; str->push('\r'); case  't'; str->push('\t');
         case  'v'; str->push('\v'); case  'f'; str->push('\f');
         case  '0'; str->push('\0');
         case 'x';
            let x0 = xdigit2num(chr(P)),
                x1 = xdigit2num(chr(P));
            if x0 < 0 or x1 < 0 {
               fatal(P, P.tokloc, "not a hex byte escape sequence");
            }
            str->push((x0 << 4) | x1);            
         case else
            fatal(P, P.tokloc, "unknown escape sequence '\\%c'", c);
         }
      }

      if delim == '"' {
         tok.t = :str;
         tok.u.str = str->move(P.alloc);
      } else {
         tok.t = :chr;
         if str.len == 0 {
            fatal(P, P.tokloc, "empty char literal");
         } else if str.len > 8 {
            fatal(P, P.tokloc, "too long multichar literal %qs", str.dat);
         }
         tok.u.uint = 0;
         vec_each(c0, i, str) {
            tok.u.uint = (tok.u.uint << 8) | c0;   
         }
      }
      return tok;
   }
   switch c = chr(P) {
   case '(', ')', '[', ']', '{',
        '}', ',', ';', '~';
      tok.t = c;
      return tok;
   case '?';
      if chrmatch(P, '?') { tok.t = '??'; }
      else                { tok.t = '?'; }
      return tok;
   case '.';
      if chrmatch(P, '.') {
         if chrmatch(P, '.') { tok.t = '...'; }
         else { tok.t = '..'; }
      } else { tok.t = '.'; }
      return tok;
   case '*';
      if chrmatch(P, '=') { tok.t = '*='; }
      else                { tok.t = '*'; }
      return tok;
   case '/';
      if chrmatch(P, '=') { tok.t = '/='; }
      else if chrmatch(P, '/') {
         while (c = chr(P)) != 0 and c != '\n' { }
         return lex(P);
      }
      else { tok.t = '/'; }
      return tok;
   case '%';
      if chrmatch(P, '=') { tok.t = '%='; }
      else                { tok.t = '%'; }
      return tok;
   case '+';
      if chrmatch(P, '=')      { tok.t = '+='; }
      else if chrmatch(P, '+') { tok.t = '++'; }
      else                     { tok.t = '+'; }
      return tok;
   case '-';
      if chrmatch(P, '=')      { tok.t = '-='; }
      else if chrmatch(P, '-') { tok.t = '--'; }
      else if chrmatch(P, '>') { tok.t = '->'; }
      else                     { tok.t = '-'; }
      return tok;
   case '&';
      if chrmatch(P, '=') { tok.t = '&='; }
      else                { tok.t = '&'; }
      return tok;
   case '|';
      if chrmatch(P, '=') { tok.t = '|='; }
      else                { tok.t = '|'; }
      return tok;
   case '^';
      if chrmatch(P, '=') { tok.t = '^='; }
      else                { tok.t = '^'; }
      return tok;
   case ':';
      if chrmatch(P, ':') { tok.t = '::'; }
      else                { tok.t = ':'; }
      return tok;
   case '=';
      if chrmatch(P, '=') { tok.t = '=='; }
      else                { tok.t = '='; }
      return tok;
   case '!';
      if chrmatch(P, '=') { tok.t = '!='; }
      else                { tok.t = '!'; }
      return tok;
   case '<';
      if chrmatch(P, '=') { tok.t = '<='; }
      else if chrmatch(P, '<') {
         if chrmatch(P, '=') { tok.t = '<<='; }
         else                { tok.t = '<<'; }
      } else { tok.t = '<'; }
      return tok;
   case '>';
      if chrmatch(P, '=') { tok.t = '>='; }
      else if chrmatch(P, '>') {
         if chrmatch(P, '=') { tok.t = '>>='; }
         else                { tok.t = '>>'; }
      } else { tok.t = '>'; }
      return tok;
   case EOF, 0;
      tok.t = :eof;
      return tok;
   }
   fatal(P, tok.loc, "stray %qc in program", c);
}

fn lexpeek(P *Parser) Tok {
   switch P.peektok {
   case Some t; return t;
   }
   let tok = lex(P);
   P.peektok = :Some(tok);
   return tok;
}

fn lexmatch(P *Parser, tokp *Tok, t TokT) bool {
   let tok = lexpeek(P);
   if tokp {
      *tokp = tok;
   }
   if tok.t == t {
      lex(P);
      return #t;
   }
   return #f;
}

fn lexexpects(P *Parser, t TokT, what *const u8) Tok {
   let tok = Tok {};
   if !lexmatch(P, &tok, t) {
      if what {
         fatal(P, tok.loc, "expected %s (near %qT)", what, tok);
      } else {
         fatal(P, tok.loc, "expected %qk (near %qT)", t, tok);
      }
   }
   return tok;
}
defmacro lexexpect(P, t) [lexexpects(P, t, #null)]

////////////
// Parser //
////////////

static primenv *Env = {};

fn pushenv(P *Parser, env *Env) void {
   assert(P.curenv == envparent(env), "pushenv");
   P.curenv = env;
}

fn popenv(P *Parser) void {
   P.curenv = envparent(P.curenv);
   assert(P.curenv != #null, "popenv");
}

fn finddecl(P *Parser, name *const u8) *Decl {
   let p = envfind(primenv, name);
   return p ?? envfind(P.curenv, name);
}

fn finddecl_noparent(P *Parser, name *const u8) *Decl {
   let p = envfind(primenv, name);
   return p ?? envfind_noparent(P.curenv, name);
}

fn putdecl(P *Parser, eloc Loc, decl Decl) *Decl {
   if envfind(primenv, decl.name) {
      fatal(P, eloc, "cannot shadow primitive `%s'", decl.name);
   }
   let d0 *const Decl;
   let d = envput(P.curenv, decl, &d0);
   if d == #null {
      fatal(P, eloc, "attempt to redefine `%s' (previously defined at %l)", decl.name, d0.loc);
   }
   return d;
}

///////////////////
// Types Parsing //
///////////////////

fn parseexpr(P *Parser) Expr;
fn parsetype(P *Parser) *const Type;
typedef DeclYielder *fn(*Decl, *void) void;
fn parsedecls(P *Parser, yield DeclYielder, yarg *void, toplevel bool) void;

fn parseenum(P *Parser, name *const u8, lax bool) *const Type {
   lexexpect(P, '{');
   let iota = 0i64;
   let max = iota;
   let vals Vec<EnumVal> = {};
   while !lexmatch(P, #null, '}') {
      let name = lexexpects(P, :ident, "variant name").u.ident;
      if lexmatch(P, #null, '=') {
         let ex = parseexpr(P);
         if !fold(&ex) or !ex.ty->is(:Int) {
            err(P, ex.loc, "expected constant integer expression");
         }
         iota = ex.u.IntLit.i;
      }
      vals->push({
         name,
         iota++,
      });
      if !lexmatch(P, #null, ',') {
         lexexpect(P, '}');
         break;
      }
   }
   let intty *const Type =
      max < 1u64 << ((g_targ.intsize * 8) - 1) ? ty_int
    : max < 1u64 << 31 ? ty_i32
    : ty_i64;
   static id int = 0;
   return interntype({ .u: :Enum { intty, name, lax, id++, vals->move(P.alloc) }});
}

fn isdecltokt(t TokT) bool {
   switch t {
   case :kw_fn, :kw_static, :kw_def, :kw_defmacro, :kw_struct, :kw_union, :kw_enum,
        :kw_extern;
      return #t;
   }
   return #f;
}

fn parseagg(P *Parser, kind AggKind, name *const u8, retdecl **Decl) *const Type {
   let loc = P.tokloc;
   let tok Tok #?;
   static id int = 0;
   let decl *Decl = name ? finddecl_noparent(P, name) : #null;
   if decl {
      switch decl.u {
      case Ty ty; if !ty->is(:Agg) or !ty.u.Agg.fwd { decl = #null; }
      }
   }
   let ty = decl ? decl.u.Ty : interntype({ .u: :Agg { kind, name, id++ }});
   let ty = as(*Type)ty;
   let agg = &ty.u.Agg;

   if name != #null {
      agg.fwd = #t;
      if decl == #null {
         decl = putdecl(P, loc, { name, loc, .u: :Ty(ty)});
         if retdecl {
            *retdecl = decl;
         }
      }
   }
   if !lexmatch(P, &tok, ';') {
      agg.fwd = #f;
      lexexpect(P, '{');
      let size = 0, align = 1;
      let flds Vec<AggField> = {};
      let havedecls = #f;
      while !lexmatch(P, #null, '}') {
         if isdecltokt(lexpeek(P).t) {
            havedecls = #t;
            break;
         }
         let off = size;
         let name = lexexpects(P, :ident, "field name").u.ident;
         let type = parsetype(P);
         if type {
            off = ALIGNUP(off, type.align);
            align = MAX(align, type.align);
            size = kind == :Struct ? off + type.size
                                   : MAX(size, type.size);
         }
         flds->push({ name, type, off });

         if !lexmatch(P, #null, ',') {
            lexexpect(P, '}');
            break;
         }
      }
      ty.size = size;
      ty.align = align; 
      agg.flds = flds.dat[0::flds.len];
      if havedecls {
         agg.decls = mkenv(P.curenv, P.alloc);
         pushenv(P, agg.decls);
         while !lexmatch(P, #null, '}') {
            parsedecls(P, #null, #null, #{toplevel} #f);
         }
         popenv(P);
      }
   }
   return ty;
}

fn findaggfield(ty *const Type, name *const u8) *AggField {
   foreach_ptr(fld, i, ty.u.Agg.flds) {
      if streq(fld.name, name) {
         return fld;
      }
   }
   return #null;
}

fn xident2type(P *Parser, eloc Loc, name *const u8) *const Type {
   let decl = finddecl(P, name);
   if decl == #null {
      fatal(P, eloc, "`%s' is not defined", name);
   }
   if decl.u.#tag != :Ty {
      fatal(P, eloc, "`%s' is not a type", name);
   }
   return decl.u.Ty;
}

fn parsefnparams(P *Parser, variadic *bool, paramnames *Vec<*const u8>, paramtys *Vec<*const Type>) void {
   lexexpect(P, '(');
   let tok Tok #?;
   *variadic = #t;
   while !lexmatch(P, &tok, ')') {
      if lexmatch(P, #null, '...') {
         *variadic = #t;
         lexmatch(P, #null, ',');
         lexexpect(P, ')');
         break;
      }
      let name *const u8 = #null;
      let type *const Type #?;
      if lexmatch(P, &tok, :ident) {
         let tok2 Tok #?;
         if (tok2 = lexpeek(P)).t == ',' or tok2.t == ')' {
            type = xident2type(P, tok.loc, tok.u.ident);
         } else {
            name = tok.u.ident;
            type = parsetype(P);
         }
      } else {
         type = parsetype(P);
      }
      if paramnames {
         paramnames->push(name);
      }
      paramtys->push(type);
      if !lexmatch(P, &tok, ',') {
         lexexpect(P, ')');
         break;
      }
   }
}

fn parsefntype(P *Parser) *const Type {
   let variadic = #f;
   let paramtys Vec<*const Type> = {};
   parsefnparams(P, &variadic, #null, &paramtys);
   let ret = parsetype(P);
   return interntype({ .u: :Fn {
      paramtys->move(P.alloc),
      variadic,
      ret,
   }});
}

fn parsetype(P *Parser) *const Type {
   let tok Tok = {};
   switch {
   case lexmatch(P, &tok, :kw_const);
      return constify(parsetype(P));

   case lexmatch(P, &tok, '*');
      return mkptrtype(parsetype(P));

   case lexmatch(P, &tok, '[');
      let len = -1i64;
      if lexmatch(P, &tok, '#') {
         lexexpect(P, ']');
         return mkslicetype(parsetype(P));
      } else if !lexmatch(P, &tok, ']') {
         let ex = parseexpr(P);
         lexexpect(P, ']');
         if !fold(&ex) or ex.u.#tag != :IntLit or ex.u.IntLit.i < 0 {
            fatal(P, ex.loc, "expected constant non-negative integer expression for array length");
         }
         len = ex.u.IntLit.i;
      }
      let child = parsetype(P);
      return mkarrtype(len, #f, child);

   case lexmatch(P, &tok, :ident);
      return xident2type(P, tok.loc, tok.u.ident);

   case lexmatch(P, &tok, :kw_typeof);
      lexexpect(P, '(');
      let ex = parseexpr(P);
      lexexpect(P, ')');
      return ex.ty;


   case lexmatch(P, &tok, :kw_fn);
      return parsefntype(P);

   case else;
      fatal(P, tok.loc, "expected type (near %qT)", tok);
   }
}

/////////////////////////
// Expressions Parsing //
/////////////////////////

fn typematchestarg(targ *const Type, ty *const Type) bool {
   if targ == ty {
      return #t;
   }
   if typeof2(targ, ty) == #null {
      return #f;
   }
   if targ->is(:Ptr) or ty->is(:Ptr) {
      if !targ.u.Ptr.konst and ty.u.Ptr.konst {
         return #f;
      }
   }
   return #t;
}

fn exprdup(alloc *Allocator, ex Expr) *Expr {
   return memcpy(alloc->alloc(sizeof(ex)), &ex, sizeof(ex));
}

fn islvalue(ex Expr) bool {
   switch ex.u {
   case Symbol decl;
      return decl.u.#tag == :Let or decl.u.#tag == :Static;
   case UnOp u;
      return u.op == :deref;
   case Index;
      return #t;
   case Dot;
      return #t;
   }
   return #f;
}

fn parseaggini(P *Parser, ty *const Type) Expr {
   let loc = P.tokloc;
   let tok Tok #?;
   let flds Vec<*const AggField> = {};
   let exs Vec<Expr> = {};
   let iota = 0;
   while !lexmatch(P, &tok, '}') {
      let fld *AggField #?;
      let ex Expr #?;
      if lexmatch(P, &tok, '.') {
         fld = findaggfield(ty, (tok = lexexpects(P, :ident, "field name")).u.ident);
         lexexpect(P, ':');
         if fld == #null {
            fatal(P, tok.loc, "%t has no such field %qT", ty, tok);
         }
         iota = (fld - ty.u.Agg.flds.#ptr) + 1;
      } else {
         if iota >= ty.u.Agg.flds.#len {
            fatal(P, P.tokloc, "excess elements in struct initializer");
         }
         fld = &ty.u.Agg.flds[iota++];
      }
      P.targty = fld.ty;
      ex = parseexpr(P);
      flds->push(fld);
      exs->push(ex);
      if !lexmatch(P, &tok, ',') {
         lexexpects(P, '}', "`,' or `}'");
         break;
      }
   }
   return { loc, ty, :AggIni { flds->move(P.alloc), exs->move(P.alloc) }};
}

fn parsearrini(P *Parser, ty *const Type) Expr {
   let loc = P.tokloc;
   let tok Tok #?;
   let idxs Vec<u32> = {};
   let exs Vec<Expr> = {};
   let iota = 0;
   let maxn = 0;
   while !lexmatch(P, &tok, '}') {
      P.targty = ty.u.Arr.child;
      let ex Expr #?;
      if lexmatch(P, #null, '[') {
         let iex = parseexpr(P);
         lexexpect(P, ']');
         lexexpect(P, '=');
         if !fold(&iex) or iex.u.#tag != :IntLit {
            fatal(P, iex.loc, "expected integer constant expression for array index");
         }
         iota = iex.u.IntLit.i;
         if iota < 0 or (ty.u.Arr.length < 0 ? #f : iota >= ty.u.Arr.length) {
            fatal(P, iex.loc, "index out of bounds");
         }
         ex = parseexpr(P);
      } else {
         ex = parseexpr(P);
      }
      idxs->push(iota++);
      exs->push(ex);
      maxn = MAX(maxn, iota);
      
      if !lexmatch(P, &tok, ',') {
         lexexpects(P, '}', "`,' or `}'");
         break;
      }
   }
   return { loc, ty, :ArrIni { idxs->move(P.alloc), exs->move(P.alloc), maxn }};
}


fn mergetoktrees(alloc *Allocator, src *[#]Tok, n int) [#]Tok {
   let total = 0z;
   for let i = 0; i < n; ++i {
      total += src[i].#len;
      if i > 0 {
         ++total;
      }
   }
   let d *Tok = alloc->alloc(total * sizeof Tok);
   let len = 0;
   for let i = 0; i < n; ++i {
      if i > 0 {
         d[len++] = { ',' };
      }
      memcpy(d + len, src[i].#ptr, src[i].#len * sizeof Tok);
      len += src[i].#len;
   }
   assert(len == total, "mergetoktrees");
   return d[0::len];
}

fn parseexpandmacro(P *Parser, mac *Macro) void {
   let tok Tok #?;
   let expan Expan = {};
   let args Vec<[#]Tok> = {};
   let c MacroCase #?;
   let loc = P.tokloc;
   let mname = container_of(mac, Decl, u.Macro).name;
   lexexpect(P, '(');
   
   while !lexmatch(P, &tok, ')') {
      let pabal = 0, // ( ) parens balance
          bkbal = 0, // [ ] brackets
          bcbal = 0; // { } braces
      let eloc = tok.loc;
      let toks Vec<Tok> = {};
      #'arg for ;; {
         tok = lex(P);
         switch tok.t {
         case '['; ++bkbal; case ']'; --bkbal;
         case '{'; ++bcbal; case '}'; --bcbal;
         case '('; ++pabal;
         case ')';
            if --pabal < 0 {
               break #'arg;
            }
         case ',';
            if pabal == 0 and bkbal == 0 and bcbal == 0 {
               break #'arg;
            }
         case :eof;
            fatal(P, eloc, "unterminated macro `%s' invocation", mname);
         }
         toks->push(tok);
      }

      args->push(toks->move(P.alloc));
      if tok.t != ',' {
         assert(tok.t == ')', "ok");
         break;
      }
   }
   let matches = #f, bodyarg = #f;
   if lexpeek(P).t == '{' {
      foreach(cas, _, mac.cs) {
         c = cas;
         if args.len == c.params.#len - 1 and c.bodyarg {
            bodyarg = #t;
            break;
         }
      }
      if bodyarg {
         let bal = 0;
         let eloc = tok.loc;
         let toks Vec<Tok> = {};
         do {
            tok = lex(P);
            switch tok.t {
            case '{'; ++bal; case '}'; --bal; 
            case :eof;
               fatal(P, eloc, "unterminated macro `%s' invokation", mname);
            }
         toks->push(tok);
         } while bal != 0;
         args->push(toks->move(P.alloc));
         matches = #t;
      }
   }
   if !bodyarg {
      foreach(cas, _, mac.cs) {
         c = cas;
         if !c.variadic and args.len == c.params.#len {
            matches = #t;
            break;
         } else if c.variadic and args.len >= c.params.#len - 1 {
            let n = args.len - (c.params.#len - 1);
            if n == 0 {
               args->push({});
            } else {
               let arg = mergetoktrees(P.alloc, args.dat + (c.params.#len - 1), n);
               args.dat[c.params.#len - 1] = arg;
            }
            matches = #t;
            break;
         }
      }
   }
   if !matches {
      fatal(P, tok.loc, "no match for invoking macro `%s' with %d arguments", mname, args.len);
   }
   let expanargs *ExpanArg = xcalloc(c.params.#len, sizeof ExpanArg);
   foreach(param, i, c.params) {
      expanargs[i].name = param;
      expanargs[i].toks = args.dat[i];
   }
   args->clear();
   expan.prev = P.curexpan;
   expan.loc = loc;
   expan.name = mname;
   expan.args = expanargs[0::c.params.#len];
   expan.peektok = P.peektok;
   P.peektok = :None;
   expan.toks = c.body;
   ++P.expanno;
   P.curexpan = memcpy(xmalloc(sizeof Expan), &expan, sizeof Expan);
   
}

fn parseblock0(P *Parser) [#]Stmt;

fn pexprimary(P *Parser) Expr {
   let tok Tok = lex(P);
   let ex Expr #?;
   switch tok.t {
   case :int, :chr;
      ex = { tok.loc, tok.ty, .u: :IntLit { tok.u.int }};

   case :flo;
      ex = { tok.loc, tok.ty, .u: :FloLit(tok.u.flo) };

   case :bool;
      ex = { tok.loc, ty_bool, .u: :BoolLit(tok.u.bool) };

   case :null;
      ex = { tok.loc, ty_voidptr, .u: :NullLit };

   case :str;
      let ty = mkarrtype(tok.u.str.#len + 1, #t, ty_u8);
      ex = { tok.loc, ty, .u: :StrLit(tok.u.str) };

   case :ident;
      let ident = tok.u.ident;
      let decl = finddecl(P, ident);
      if decl == #null {
         fatal(P, tok.loc, "%qT is not defined", tok);
      }
      while #t {
         switch decl.u {
         case Fn f;
            ex = { tok.loc, f.ty, .u: :Symbol(decl) };
         case Let var;
            ex = { tok.loc, var.ty, .u: :Symbol(decl) };
         case Static var;
            ex = { tok.loc, var.ty, .u: :Symbol(decl) };
         case Def dex;
            dex.loc = tok.loc;
            ex = dex; 
         case Macro *mac;
            parseexpandmacro(P, mac);
            ex = parseexpr(P);
         case Ty ty;
            if (tok = lexpeek(P)).t != ':' and tok.t != '{' {
               fatal(P, tok.loc, "expected `:' or `{' after type name");
            }
            if tok.t == ':' and ty->is(:Agg) and ty.u.Agg.kind != :EUnion {
               lex(P);
               let name = (tok = lexexpect(P, :ident)).u.ident;
               decl = envfind_noparent(ty.u.Agg.decls, name);
               if decl == #null {
                  fatal(P, tok.loc, "%t has no such decl %qT", ty, tok);
               }
               continue;
            } else if !ty->is(:Agg) and !ty->is(:Enum) {
               fatal(P, tok.loc, "type is not aggregate or enum");
            } else {
               P.targty = ty;
               return parseexpr(P);
            }
         }
         break;
      }
   case :kw_sizeof;
      let ty *const Type #?;
      if lexmatch(P, &tok, '(') {
         let ex = parseexpr(P);
         lexexpect(P, ')');
         ty = ex.ty;
      } else {
         ty = parsetype(P);
      }
      if !completetype(ty) {
         err(P, tok.loc, "sizeof incomplete type (%t)", ty);
      }
      ex = { tok.loc, ty_usize, :IntLit { ty.size }};

   case '(';
      if lexmatch(P, &tok, :kw_do) {
         let st = parseblock0(P);
         lexexpect(P, ')');
         if st.#len == 0 or st[st.#len - 1].u.#tag != :Expr {
            ex = { tok.loc, ty_void, :Stmt(st) };
         } else {
            ex = { tok.loc, st[st.#len - 1].u.Expr.ty, :Stmt(st) };
         }
      } else {
         ex = parseexpr(P);
         lexexpect(P, ')');
      }

   case ':';
      if P.targty == #null {
         fatal(P, tok.loc, "cannot infer type for variant");
      }
      let ty = P.targty;
      if ty->is(:Enum) {
         let name = (tok = lexexpects(P, :ident, "variant name")).u.ident;
         let i i64 #?;
         #'search do {
            foreach(val, _, ty.u.Enum.vals) {
               if streq(val.name, name) {
                  i = val.i;
                  break #'search;
               }
            }
            fatal(P, tok.loc, "%t has no such variant %qT", ty, tok);
         } while #f;
         ex = { tok.loc, ty, :EnumIni { name, i }};
      } else if ty->is(:Agg) and ty.u.Agg.kind == :EUnion {
         assert(#f, "NYI");
      } else {
         fatal(P, tok.loc, "cannot infer type for variant");
      }

   case '{';
      if P.targty == #null {
         fatal(P, tok.loc, "cannot infer type for initializer");
      }
      let ty = P.targty;
      P.targty = #null;
      if lexmatch(P, #null, '}') {
         ex = { tok.loc, ty, .u: :ZeroIni };
      } else {
         if ty->is(:Agg) {
            ex = parseaggini(P, ty);
         } else if ty->is(:Arr) {
            ex = parsearrini(P, ty);
         } else {
            fatal(P, tok.loc, "excess elements in initializer");
         }
      }
   case else;
      fatal(P, tok.loc, "expected expression (near %qT)", tok);
   }
   P.targty = #null;
   return ex;
}

fn pexpostfix(P *Parser) Expr {
   let tok Tok = {};
   let ex = pexprimary(P);
   for ;; {
      switch {
      case lexmatch(P, &tok, '(');
         let lhs = exprdup(P.alloc, ex),
             ty = lhs.ty->is(:Ptr) ? lhs.ty.u.Ptr : lhs.ty;
         if !ty->is(:Fn) {
            fatal(P, lhs.loc, "not callable (%t)", lhs.ty);
         }
         let Fn = &ty.u.Fn;
         let args Vec<Expr> = {};
         let params = Fn.params;
         let param = &params[0];
         while !lexmatch(P, #null, ')') {
            let ex = parseexpr(P);
            args->push(ex);
            if args.len >= params.#len and !Fn.variadic {
               fatal(P, ex.loc, "too many args (%z, expected %z)", args.len, params.#len);
            }
            if args.len < params.#len and !typematchestarg(*param, ex.ty) {
               err(P, ex.loc, "function call argument type mismatch (%t, expected %t)",
                   ex.ty, *param);
            }
            param++;
            if !lexmatch(P, #null, ',') {
               lexexpect(P, ')');
               break;
            }
         }
         if args.len < Fn.params.#len {
            err(P, lhs.loc, "too few args (%z, expected %z)", args.len, Fn.params.#len);
         }
         ex = { tok.loc, .ty: Fn.ret, .u: :Call { lhs, args->move(P.alloc) }};         
      
      case lexmatch(P, &tok, '[');
         let lhs = exprdup(P.alloc, ex),
             rhs = exprdup(P.alloc, parseexpr(P));
         if !lhs.ty->is(:Ptr) and !lhs.ty->is(:Arr) and !lhs.ty->is(:Slice) {
            fatal(P, lhs.loc, "indexee is not array or pointer type (%t)", lhs.ty);
         }
         if !rhs.ty->is(:Int) {
            err(P, lhs.loc, "index expression type is not integral (%t)", rhs.ty);
         }

         if lexmatch(P, #null, '::') {
            let end *Expr #?;
            if !lexmatch(P, #null, ']') {
               end = exprdup(P.alloc, parseexpr(P));
               if !end.ty->is(:Int) {
                  err(P, lhs.loc, "slice range end expression type is not integral (%t)", end.ty);
               }
               lexexpect(P, ']');
            } else if lhs.ty->is(:Arr) {
               end = exprdup(P.alloc, { tok.loc, ty_usize, .u: :IntLit{lhs.ty.u.Arr.length} });
            } else {
               fatal(P, tok.loc, "missing end of slice range");
            }
            ex = { tok.loc, mkslicetype(childtype(lhs.ty)), .u: :Slice { lhs, rhs, end }};
         } else {
            lexexpect(P, ']');
            ex = { tok.loc, childtype(lhs.ty), .u: :Index { lhs, rhs }};
         }
      case lexmatch(P, &tok, '++') or lexmatch(P, &tok, '--');
         if !isnumtype(ex.ty) and !ex.ty->is(:Ptr) {
            fatal(P, ex.loc, "invalid operand to unary operator %qT (%t)", tok, ex.ty);
         }
         if !islvalue(ex) {
            err(P, ex.loc, "left operand to prefix %qT operator is not lvalue", tok);
         }
         if ex.ty.konst {
            err(P, ex.loc, "left operand to prefix %qT operator is const", tok);
         }
         ex = {
            tok.loc, ex.ty, .u: :UnOp {
               tok.t == '++' ? :postinc : :postdec, exprdup(P.alloc, ex)
            }
         };
      case lexmatch(P, &tok, '.');
         switch {
         case lexmatch(P, &tok, :ident);
            let name = tok.u.ident;
            let ty = ex.ty;
            if ty->is(:Ptr) {
               ty = ty.u.Ptr;
            }
            if !ty->is(:Agg) {
               fatal(P, tok.loc, "left-hand-side is not an aggregate (%t)", ty);
            }
            let konst = ty.konst;
            ty = unconstify(ty);
            let agg = &ty.u.Agg;
            let fld *AggField = #null;
            foreach(f, i, agg.flds) {
               if streq(name, f.name) {
                  fld = &agg.flds[i];
                  break;
               }
            }
            if fld == #null {
               fatal(P, tok.loc, "%t has no such field %qT", ty, tok);
            }
            if fld.ty == #null {
               fatal(P, tok.loc, "field %qT has no type", tok);
            }
            ex = { tok.loc, konst ? constify(fld.ty) : fld.ty, :Dot { exprdup(P.alloc, ex), fld }};

         case lexmatch(P, &tok, '#ptr');
            let ty = ex.ty;
            if ty->is(:Ptr) {
               ty = ty.u.Ptr;
            }
            switch ty.u {
            case Slice;
               ex = { tok.loc, ty_usize, :SPtr(exprdup(P.alloc, ex)) };
            case else;
               fatal(P, ex.loc, "invalid operand to `#len' (%t)", ex.ty);
            }
         case lexmatch(P, &tok, '#len');
            let ty = ex.ty;
            if ty->is(:Ptr) {
               ty = ty.u.Ptr;
            }
            switch ty.u {
            case Arr arr;
               assert(arr.length >= 0, "arr len");
               ex = { tok.loc, ty_usize, :IntLit { arr.length }};
            case Slice;
               ex = { tok.loc, ty_usize, :SLen(exprdup(P.alloc, ex)) };
            case else;
               fatal(P, ex.loc, "invalid operand to `#len' (%t)", ex.ty);
            }
         // case lexmatch(P, &tok, '#tag');

         case else;
            lexexpects(P, :ident, "field name");
         }

      case lexmatch(P, &tok, '->');
         let name = (tok = lexexpects(P, :ident, "method name")).u.ident;
         let ty = ex.ty;
         if ty->is(:Ptr) {
            ty = ty.u.Ptr;
         }
         if !ty->is(:Agg) {
            fatal(P, tok.loc, "left-hand-side is not an aggregate (%t)", ty);
         }
         let agg = &ty.u.Agg;
         let decl = envfind_noparent(agg.decls, name);
         if decl == #null {
            fatal(P, tok.loc, "%t has no such method %qT", ty, tok);
         }
         lexexpect(P, '(');
         switch decl.u {
         case Fn f;
            let Fn = &f.ty.u.Fn;
            if Fn.params.#len == 0 {
               fatal(P, tok.loc, "function takes no arguments");
            }
            let args Vec<Expr> = {};
            args->push(ex);
            while !lexmatch(P, #null, ')') {
               args->push(parseexpr(P));
               if args.len > Fn.params.#len and !Fn.variadic {
                  fatal(P, args->last().loc, "too many args (%z, expected %z)", args.len, Fn.params.#len);
               }
               if !lexmatch(P, #null, ',') {
                  lexexpect(P, ')');
                  break;
               }
            }
            if args.len < Fn.params.#len {
               err(P, ex.loc, "too few args (%z, expected %z)", args.len, Fn.params.#len);
            }
            let met Expr = { tok.loc, f.ty, :Symbol(decl) };
            ex = { tok.loc, .ty: Fn.ret, .u: :Call { exprdup(P.alloc, met), args->move(P.alloc) }};         

         case else;
            fatal(P, tok.loc, "cannot call `->%s': not a function or macro", name);
         }

      case else;
         break;
      }
   }
   return ex;
}

fn pexprefix(P *Parser) Expr {
   let tok Tok #?;
   switch {
   case lexmatch(P, &tok, '-') or lexmatch(P, &tok, '~');
      let ex = pexprefix(P);
      let ty = typeof2(ex.ty, ty_int);
      if ty == #null {
         fatal(P, ex.loc, "invalid operand to unary operator %qT (%t)", tok, ex.ty);
      }
      if !ty->is(:Int) and tok.t == '~' {
         fatal(P, ex.loc, "invalid operand to unary operator %qT (%t)", tok, ex.ty);
      }
      return {
         tok.loc, ty, .u: :UnOp {
            tok.t == '-' ? :neg : :compl, exprdup(P.alloc, ex)
         }
      };
   case lexmatch(P, &tok, '++') or lexmatch(P, &tok, '--');
      let ex = pexprefix(P);
      if !isnumtype(ex.ty) and !ex.ty->is(:Ptr) {
         fatal(P, ex.loc, "invalid operand to unary operator %qT (%t)", tok, ex.ty);
      }
      if !islvalue(ex) {
         err(P, ex.loc, "left operand to prefix %qT operator is not lvalue", tok);
      }
      if ex.ty.konst {
         err(P, ex.loc, "left operand to prefix %qT operator is const", tok);
      }
      return {
         tok.loc, ex.ty, .u: :UnOp {
            tok.t == '++' ? :preinc : :predec, exprdup(P.alloc, ex)
         }
      };
   case lexmatch(P, &tok, '!');
      let ex = pexprefix(P);
      if !ex.ty->is(:Bool) {
         err(P, ex.loc, "invalid operand to unary operator %qT (%t)", tok, ex.ty);
      }
      return { tok.loc, ty_bool, .u: :UnOp { :not, exprdup(P.alloc, ex) }};

   case lexmatch(P, &tok, '*');
      let ex = pexprefix(P);
      if !ex.ty->is(:Ptr) {
         fatal(P, ex.loc, "invalid operand to dereference, not pointer (%t)", ex.ty);
      }
      let child = ex.ty.u.Ptr;
      if !completetype(child) and !child->is(:Fn) {
         fatal(P, ex.loc, "invalid operand to dereference, incomplete (%t)", ex.ty);
      }
      return { tok.loc, child, .u: :UnOp { :deref, exprdup(P.alloc, ex) }};

   case lexmatch(P, &tok, '&');
      let ex = pexprefix(P);
      let ty2 = interntype({ g_targ.ptrsize, .u: :Ptr(ex.ty) });
      if !islvalue(ex) and !(ex.u.#tag == :Symbol and ex.u.Symbol.u.#tag == :Fn)
       and !(ex.u.#tag == :ZeroIni or ex.u.#tag == :AggIni or ex.u.#tag == :ArrIni) {
         err(P, ex.loc, "invalid operand to `&': not an lvalue");
      }
      return { tok.loc, ty2, .u: :UnOp { :addrof, exprdup(P.alloc, ex) }};

   case lexmatch(P, &tok, :kw_as);
      let loc = tok.loc;
      lexexpect(P, '(');
      let ty = parsetype(P);
      lexexpect(P, ')');
      let ex = pexprefix(P);
      // TODO check valid cast
      return { loc, ty, :Cast(exprdup(P.alloc, ex)) };
   }
   return pexpostfix(P);
}

fn pexbitarith(P *Parser) Expr {
   enum Kind { None, IntFlo, Int, StrLit }
   fn peeksop(P *Parser, tokp *Tok) Kind {
      let tok = lexpeek(P);
      if tokp { *tokp = tok; }
      switch tok.t {
      case '+', '-', '*', '/';
         return :IntFlo;
      case '%', '&', '|', '^', '<<', '>>';
         return :Int;
      case '##';
         return :StrLit;
      }
      return :None;
   }

   let ex = pexprefix(P);
   let tok Tok = {};
   let okind = peeksop(P, &tok);
   if okind == :None {
      return ex;
   }
   let tokt = tok.t;
   while lexmatch(P, &tok, tokt) {
      let rhs = pexprefix(P);
      let ty = typeof2(ex.ty, rhs.ty);
      switch {
      case ty == #null and tokt == '+'
       and ((ex.ty->is(:Int) and rhs.ty->is(:Ptr)) or (rhs.ty->is(:Int) and ex.ty->is(:Ptr)));
         ty = ex.ty->is(:Ptr) ? ex.ty : rhs.ty;
      case ty == #null and tokt == '-' and rhs.ty->is(:Int) and ex.ty->is(:Ptr);
         ty = ex.ty->is(:Ptr) ? ex.ty : rhs.ty;
      case ty == #null;
         fatal(P, tok.loc, "invalid operands %t and %t to binary operator %k", ex.ty, rhs.ty, tokt);
      case tokt == '-' and ex.ty->is(:Ptr) and rhs.ty->is(:Ptr);
         ty = ty_isize;
      case okind == :Int and ty->is(:Flo);
         err(P, tok.loc, "invalid operands %t and %t to binary operator %k", ex.ty, rhs.ty, tokt);
      case okind != :StrLit and !isnumtype(ty);
         fatal(P, tok.loc, "invalid operands %t and %t to binary operator %k", ex.ty, rhs.ty, tokt);
      }
      ex = { tok.loc, ty, .u: :BinOp { tokt, exprdup(P.alloc, ex), exprdup(P.alloc, rhs) }};
   }
   return ex;
}

fn pexcmp(P *Parser) Expr {
   fn matchcmpop(P *Parser, tokp *Tok) bool {
      let tok = lexpeek(P);
      if tokp {
         *tokp = tok;
      }
      switch tok.t {
      case '==', '<=', '>=', '<', '>', '!=';
         lex(P);
         return #t;
      }
      return #f;
   }

   let ex = pexbitarith(P);
   let tok Tok = {};
   if matchcmpop(P, &tok) {
      let rhs = pexbitarith(P);
      if typeof2(ex.ty, rhs.ty) == #null {
         fatal(P, tok.loc, "incompatible operands %t and %t to binary operator %qT",
               ex.ty, rhs.ty, tok);
      }
      let ty = typeof2(ex.ty, rhs.ty);
      if tok.t != '==' and tok.t != '!=' {
         if !isnumtype(ty) and !ty->is(:Ptr) {
            fatal(P, tok.loc, "invalid non-numeric operands %t and %t to relational operator %qT",
                  ex.ty, rhs.ty, tok);
         }
         if ty->is(:Int) and ty != ty_int and ex.ty.u.Int.sgn != rhs.ty.u.Int.sgn {
            warn(P, tok.loc, "comparing integers of different signedness (%t and %t)", ex.ty, rhs.ty);
         }
      }

      ex = {
         tok.loc, ty_bool, .u: :BinOp {
            tok.t, exprdup(P.alloc, ex), exprdup(P.alloc, rhs)
         }
      };
   }
   return ex;
}

fn pexlog(P *Parser) Expr {
   let ex = pexcmp(P);
   let tok Tok = lexpeek(P);
   let tokt = lexpeek(P).t;
   if tokt != :kw_and and tokt != :kw_or and tokt != '??' {
      return ex;
   }
   while lexmatch(P, &tok, tokt) {
      let rhs = pexcmp(P);
      if tokt == '??' {
         let ty = typeof2(ex.ty, rhs.ty);
         if !ex.ty->is(:Ptr) or !rhs.ty->is(:Ptr) or ty == #null {
            fatal(P, tok.loc, "invalid operands %t and %t to binary operator %k",
                  ex.ty, rhs.ty, tok.t);
         }
         ex = {
            tok.loc, ty, .u: :BinOp { '??', exprdup(P.alloc, ex), exprdup(P.alloc, rhs) }
         };
      } else {
         if !ex.ty->is(:Bool) or !rhs.ty->is(:Bool) {
            fatal(P, tok.loc, "invalid operands %t and %t to binary operator %k",
                  ex.ty, rhs.ty, tok.t);
         }
         ex = {
            tok.loc, ty_bool, .u: :BinOp {
               tokt == :kw_and ? 'and' : 'or' , exprdup(P.alloc, ex), exprdup(P.alloc, rhs)
            }
         };
      }
   }
   return ex;
}

fn pexcond(P *Parser) Expr {
   let tok Tok = {};
   let ex = pexlog(P);
   if (lexmatch(P, &tok, '?')) {
      let ex2 = parseexpr(P);
      if !ex.ty->is(:Bool) and !ex.ty->is(:Ptr) {
         fatal(P, ex.loc, "invalid test operand to conditional operator (%t)", ex.ty);
      }
      lexexpect(P, ':');
      let ex3 = pexcond(P);
      let ty = typeof2(ex2.ty, ex3.ty);
      if ty == #null {
         fatal(P, tok.loc, "conditional operator branches have incompatible types %t and %t",
               ex2.ty, ex3.ty);
      }
      ex = {
         tok.loc, ty, .u: :Cond {
            exprdup(P.alloc, ex), exprdup(P.alloc, ex2), exprdup(P.alloc, ex3)
         }
      };
   }
   return ex;
}

fn pexassign(P *Parser) Expr {
   enum Kind { None, Set, IntFlo, Int }
   fn matchop(P *Parser, tokp *Tok) Kind {
      let tok = lexpeek(P);
      if tokp {
         *tokp = tok;
      }
      switch tok.t {
      case '=';
         lex(P);
         return :Set;
      case '+=', '-=', '*=', '/=';
         lex(P);
         return :IntFlo;
      case '%=', '&=', '|=', '^=', '<<=', '>>=';
         lex(P);
         return :Int;
      }
      return :None;
   }

   let tok Tok = {};
   let ex = pexcond(P);
   let okind = matchop(P, &tok);
   if okind == :None {
      return ex;
   }
   let rhs = pexcond(P);
   switch {
   case !islvalue(ex);
      err(P, ex.loc, "left operand to assignment is not lvalue");
   case (typeof2(ex.ty, rhs.ty) == #null)
     and !((ex.ty->is(:Ptr) and rhs.ty->is(:Int)
               and (tok.t == '+=' or tok.t == '-=')));
      err(P, ex.loc,
            "operands %t and %t to assignment operator %qT have incompatible types",
            ex.ty, rhs.ty, tok);
   case ex.ty.konst;
      err(P, ex.loc, "left operand to assignment is const");
   }

   return { tok.loc, ex.ty, .u: :BinOp { tok.t, exprdup(P.alloc, ex), exprdup(P.alloc, rhs) }};
}

fn parseexpr(P *Parser) Expr {
   return pexassign(P);
}

////////////////////////
// Statements Parsing //
////////////////////////

fn stmtdup(alloc *Allocator, st Stmt) *Stmt {
   return memcpy(alloc->alloc(sizeof(st)), &st, sizeof(st));
}

typedef StmtYielder *fn(Stmt, *void) void;
fn parseblock(P *Parser) [#]Stmt;
fn parsevardecl(P *Parser, toplevel bool, externp bool, letp bool, DeclYielder, *void) void;

fn pstlet(P *Parser, yield StmtYielder, yarg *void) void {
   struct Arg {
      P *Parser,
      yield StmtYielder,
      yarg *void,
   }
   fn varyield(decl *Decl, arg *void) void {
      let a *Arg = arg;
      a.yield({ decl.loc, :Decl(decl) }, a.yarg);
   }
   parsevardecl(P, #{toplevel?} #f, #{extern?} #f, #{let?} #t, &varyield, &Arg { P, yield, yarg });
}

fn pstif(P *Parser) Stmt {
   let loc = P.tokloc;
   let test = parseexpr(P);
   if !test.ty->is(:Bool) and !test.ty->is(:Ptr) {
      err(P, test.loc, "if condition must be bool or pointer (%t)", test.ty);
   }
   lexexpect(P, '{');
   let t = parseblock(P);
   if lexmatch(P, #null, :kw_else) {
      if lexmatch(P, #null, :kw_if) {
         let f = stmtdup(P.alloc, pstif(P));
         return { loc, :If { test, t, f[0::1] }};
      } else {
         lexexpect(P, '{');
         let f = parseblock(P);
         return { loc, :If { test, t, f }};
      }
   }
   return { loc, :If { test, t }};
}

fn pstreturn(P *Parser) Stmt {
   let loc = P.tokloc;
   if P.curfn == #null {
      fatal(P, loc, "return outside function");
   }
   let retty = P.curfn.ty.u.Fn.ret;
   if lexmatch(P, #null, ';') {
      if retty != ty_void {
         err(P, loc, "return with no value in function returning %t", retty);
      }
      return { loc, :Return{} };
   } else {
      let ex = parseexpr(P);
      lexexpect(P, ';');
      if !typematchestarg(retty, ex.ty) {
         err(P, ex.loc, "incompatible type in return statement (%t, expected %t)",
             ex.ty, retty);
      }
      return { loc, :Return(:Some(ex)) };
   }
}

fn pstwhile(P *Parser) Stmt {
   let loc = P.tokloc;
   let test = parseexpr(P);
   if !test.ty->is(:Bool) and !test.ty->is(:Ptr) {
      err(P, test.loc, "while condition must be bool or pointer (%t)", test.ty);
   }
   lexexpect(P, '{');
   let t [#]Stmt #?;
   with_tmpchange(P.curloop, ++P.loopid,
      t = parseblock(P);
   )
   return { loc, :While { test, t, P.loopid }};
}

fn pstfor(P *Parser) Stmt {
   let loc = P.tokloc;
   let ini [#]Stmt = {};
   let test Expr #?;
   let next = Option<Expr>:None;
   if lexmatch(P, #null, :kw_let) {
      let sts Vec<Stmt> = {};
      fn yieldlet(st Stmt, arg *void) void {
         let sts *Vec<Stmt> = arg;
         sts->push(st);
      }
      pstlet(P, &yieldlet, &sts);
      ini = sts->move(P.alloc);
   } else if lexmatch(P, #null, ';') {
      // pass
   } else {
      let ex = parseexpr(P);
      ini = stmtdup(P.alloc, { ex.loc, :Expr(ex) })[0::1];
   }

   if lexmatch(P, #null, ';') {
      // for (...; ; ...;) -> for (...; #t; ...;)
      test = { P.tokloc, ty_bool, :BoolLit(#t) };
   } else {
      test = parseexpr(P);
      lexexpect(P, ';');
   }
   if !test.ty->is(:Bool) and !test.ty->is(:Ptr) {
      err(P, test.loc, "for condition must be bool or pointer (%t)", test.ty);
   }
   if !lexmatch(P, #null, '{') {
      next = :Some(parseexpr(P));
      lexexpect(P, '{');
   }
   let body [#]Stmt #?;
   with_tmpchange(P.curloop, ++P.loopid,
      body = parseblock(P);
   )
   return { loc, :For { ini, test, next, body, P.loopid }};
}

fn pstiswitch(P *Parser, loc Loc, ex Expr) Stmt {
   let tok Tok #?;
   let cs Vec<ISwitchCase> = {};
   let f [#]Stmt = {};
   let elsep = #f;
   while !lexmatch(P, &tok, '}') {
      lexexpect(P, :kw_case);
      if lexmatch(P, &tok, :kw_else) {
         if elsep {
            err(P, tok.loc, "duplicate else case");
         }
         elsep = #t;
         f = parseblock0(P);
         continue;
      }
      let es Vec<Expr> = {};
      do {
         let e = parseexpr(P);
         if !fold(&e) {
            err(P, e.loc, "expected compile-time expression");
         }
         if !typematchestarg(ex.ty, e.ty) {
            err(P, e.loc, "bad case expression (%t, expected %t)", e.ty, ex.ty);
         }
         es->push(e);
         if !lexmatch(P, #null, ',') {
            lexexpect(P, ';');
            break;
         }
      } while !lexmatch(P, #null, ';');
      cs->push({ es->move(P.alloc), parseblock0(P) });
   }

   return { loc, :ISwitch { ex, cs->move(P.alloc), f }};
}

fn pstswitch(P *Parser) Stmt {
   let loc = P.tokloc;
   let tok Tok #?;
   if lexmatch(P, &tok, '{') {
   } else {
      let ex = parseexpr(P);
      lexexpect(P, '{');
      if ex.ty->is(:Int) or ex.ty->is(:Enum) {
         return pstiswitch(P, loc, ex);
      } else if ex.ty->is(:Agg) and ex.ty.u.Agg.kind == :EUnion {
      } else {
         fatal(P, tok.loc, "invalid switch test expression type (%t)", ex.ty);
      }
   }
}

fn parsestmts(P *Parser, yield StmtYielder, yarg *void) void {
   let tok Tok = {};
   switch {
   case lexmatch(P, &tok, '{');
      return yield({
         tok.loc, .u: :Block(parseblock(P))
      }, yarg);

   case lexmatch(P, &tok, :kw_let);
      return pstlet(P, yield, yarg);

   case lexmatch(P, &tok, :kw_if);
      return yield(pstif(P), yarg);

   case lexmatch(P, &tok, :kw_return);
      return yield(pstreturn(P), yarg);

   case lexmatch(P, &tok, :kw_while);
      return yield(pstwhile(P), yarg);

   case lexmatch(P, &tok, :kw_for);
      return yield(pstfor(P), yarg);

   case lexmatch(P, &tok, :kw_break);
      if P.curloop == 0 {
         err(P, tok.loc, "break outside loop");
      }
      lexexpect(P, ';');
      return yield({ tok.loc, :Break(P.curloop) }, yarg);

   case lexmatch(P, &tok, :kw_continue);
      if P.curloop == 0 {
         err(P, tok.loc, "continue outside loop");
      }
      lexexpect(P, ';');
      return yield({ tok.loc, :Continue(P.curloop) }, yarg);

   case lexmatch(P, &tok, :kw_switch);
      return yield(pstswitch(P), yarg);

   case isdecltokt(tok.t);
      struct Arg {
         P *Parser,
         yield StmtYielder,
         yarg *void,
      }
      fn declyield(decl *Decl, arg *void) void {
         let a *Arg = arg;
         a.yield({ decl.loc, :Decl(decl) }, a.yarg);
      }
      parsedecls(P, &declyield, &Arg { P, yield, yarg }, #{toplevel?} #f);

   case else;
      if (tok = lexpeek(P)).t == :ident {
         let decl = finddecl(P, tok.u.ident);
         if decl != #null and decl.u.#tag == :Macro {
            lex(P);
            parseexpandmacro(P, &decl.u.Macro);
            return parsestmts(P, yield, yarg);
         }
      }
      let ex = parseexpr(P);
      lexexpect(P, ';');
      return yield({ tok.loc, .u: :Expr(ex) }, yarg); 
   }
}

fn parseblock0(P *Parser) [#]Stmt {
   let sts Vec<Stmt> = {};
   let tok Tok = {};
   let env = mkenv(P.curenv, P.alloc);
   pushenv(P, env);
   while (tok = lexpeek(P)).t != '}' and tok.t != :kw_case and tok.t != ')' {
      if lexmatch(P, #null, ';') { continue; }
      fn pushstmt(st Stmt, arg *void) void {
         let sts *Vec<Stmt> = arg;
         sts->push(st);
      }
      parsestmts(P, &pushstmt, &sts);
   }
   popenv(P);
   envfree(env);
   return sts->move(P.alloc);
}

fn parseblock(P *Parser) [#]Stmt {
   let b = parseblock0(P);
   lexexpect(P, '}');
   return b;
}

///////////////////
// Decls Parsing //
///////////////////

fn parsevardecl(P *Parser, toplevel bool, externp bool, letp bool, yield DeclYielder, yarg *void) void {
   let tok Tok #?;
   do {
      let konst = lexmatch(P, #null, :kw_const),
          tok = lexexpect(P, :ident),
          name = tok.u.ident,
          ini Option<Expr> #?,
          ty *const Type = #null,
          fwd = #f;

      if lexmatch(P, #null, '=') {
         ini = :Some(parseexpr(P));
         ty = unconstify(ini.Some.ty);
      } else {
         ty = parsetype(P);

         if lexmatch(P, #null, '=') {
            P.targty = ty;
            ini = :Some(parseexpr(P));
         } else if lexmatch(P, #null, '#?') {
            ini = :None;
         } else {
            ini = :None;
            fwd = #t;
         }
      }

      if ty->is(:Arr) and ty.u.Arr.length < 0 and !ini->empty() and ini.Some.u.#tag == :ZeroIni {
         ty = mkarrtype(0, #f, ty.u.Arr.child);
      }

      if ty->is(:Arr) and ty.u.Arr.length < 0 and !ini->empty() and ini.Some.u.#tag == :ArrIni {
         ty = mkarrtype(ini.Some.u.ArrIni.maxn, #f, ty.u.Arr.child);
      }

      if !completetype(ty) and !fwd {
         err(P, tok.loc, "incomplete type in initializer (%t)", ty);
      }

      if !ini->empty() and !typematchestarg(ty, ini.Some.ty) {
         err(P, ini.Some.loc, "incompatible initializer (%t, expected %t)", ini.Some.ty, ty);
      }
      if konst {
         ty = constify(ty);
      }

      let decl Decl = { name, tok.loc, externp, :Let { ty, ini, fwd, 0 } };
      if !letp {
         decl.u.#tag = :Static;
      }
      yield(putdecl(P, tok.loc, decl), yarg);

      if !lexmatch(P, &tok, ',') {
         lexexpects(P, ';', "`,' or `;'");
         break;
      }
   } while !lexmatch(P, &tok, ';');
}

fn parsefn(P *Parser, externp bool, name *const u8) *Decl {
   let decl Decl = {
      name,
      P.tokloc,
      externp,
      .u: :Fn {}
   };

   let Fn = &decl.u.Fn,
       paramnames Vec<*const u8> = {},
       paramtys Vec<*const Type> = {};

   let loc = P.tokloc;
   parsefnparams(P, &Fn.variadic, &paramnames, &paramtys);
   Fn.paramnames = paramnames->move(P.alloc);
   let retty = parsetype(P);
   Fn.ty = interntype({ .size: 0, .align: 1, .u: :Fn {
      paramtys->move(P.alloc), Fn.variadic, retty
   }});
   static id int = 0;
   Fn.id = ++id;
   let decl = putdecl(P, loc, decl);
   
   if !lexmatch(P, #null, '{') {
      lexexpects(P, ';', "';' or '{'");
      return decl;
   }

   with_tmpchange(P.alloc, &Allocator { &Arena {}, &Arena:allocf },
      with_tmpchange(P.curfn, Fn,
         let env = mkenv(P.curenv, P.alloc);
         pushenv(P, env);
         foreach(name, i, Fn.paramnames) {
            if name {
               putdecl(P, loc, { name, loc, .u: :Let {
                  Fn.ty.u.Fn.params[i], :None, #f, Fn.id,
               }});
            }
         }
         Fn.body = :Some(parseblock(P));
         popenv(P);
         envfree(env);
         (as(*Arena)P.alloc.a)->destroy();
      );
   );
   return decl;
}

fn doimport(P *Parser, path *const u8) [#]Decl {
   struct Entry {
      decls [#]Decl,
      wip bool,
   }
   static seen Map<*const u8, Entry, struct {
      fn hash(s *const u8) u32 { return fnv1a_s(FNV1A_INI, s); }
      fn eq(a *const u8, b *const u8) bool { return streq(a, b); }
   }> = {};
   // imports are cached based on their realpath

   fn getbasedir(path *const u8) *const u8 {
      static res [PATH_MAX]u8 = {};
      let i isize #?;
      for i = strlen(path); i > 0 and path[i] != '/'; --i { }
      if i == 0 {
         return ".";
      }
      memcpy(res, path, i);
      res[i] = 0;
      return res;
   }
   let basedir = getbasedir(P.curfile);
   let path2 [PATH_MAX]u8 #?;
   let _rpath [PATH_MAX]u8 #?;
   snprintf(path2, sizeof(path2) - 1, "%s/%s", basedir, path);
   let rpath *const u8 = realpath(path2, _rpath);
   if rpath == #null {
      fatal(P, P.tokloc, "import %qs: %s", path, strerror(errno));
   }
   let d0 = seen->get(rpath);
   if d0 != #null {
      return d0.decls;
   }
   rpath = strcpy(malloc(strlen(rpath) + 1), rpath);
   let P2 Parser #?;
   parser_init(&P2, rpath);
   P2.is_header = #t;
   let e = seen->put(rpath, { {}, #t });
   let decls = parse(&P2);

   *e = { decls, #f };
   return decls; 
}

fn parsemacro(P *Parser, name *const u8) *Decl {
   fn parsemacrocase(P *Parser) MacroCase {
      let tok Tok #?;
      let c MacroCase = {};
      let params Vec<*const u8> = {};
      let body Vec<Tok> = {};
      static gensymid int = 0;
      struct Gensyms {
         next *Gensyms,
         name *const u8,
         tok Tok,
      };
      let gensyms *Gensyms = #null;
      lexexpect(P, '(');
      while !lexmatch(P, &tok, ')') {
         if lexmatch(P, &tok, '...') {
            params->push(lexexpects(P, :ident, "parameter name").u.ident);      
            c.variadic = #t;
            lexmatch(P, &tok, ',');
            lexexpect(P, ')');
            break;
         } else if lexmatch(P, &tok, '&') {
            params->push(lexexpects(P, :ident, "parameter name").u.ident);      
            c.bodyarg = #t;
            lexmatch(P, &tok, ',');
            lexexpect(P, ')');
            break;
         } else {
            params->push(lexexpects(P, :ident, "parameter name").u.ident);      
            if !lexmatch(P, &tok, ',') {
               lexexpect(P, ')');
               break;
            }
         }
      }
      let eloc = tok.loc;
      lexexpect(P, '[');

      let bal = 1;
      while bal != 0 {
         tok = lex(P);
         switch tok.t {
         case '['; ++bal;
         case ']'; --bal;
         case :eof;
            fatal(P, eloc, "unterminated macro definition");
         }
         if tok.t == :ident {
            vec_each(par, _, params) {
               if streq(par, tok.u.ident) {
                  tok.t = :macident;
               }
            }
         } else if tok.t == :gensym {
            let gs *Gensyms #?;
            let found = #f;
            for gs = gensyms; gs; gs = gs.next {
               if streq(gs.name, tok.u.ident) {
                  tok = gs.tok;
                  found = #t;
                  break;
               }
            }
            if !found {
               gs = xcalloc(1, sizeof(*gs));
               gs.name = tok.u.ident;
               gs.tok.t = :ident;
               gs.tok.loc = tok.loc;
               let s [300]u8 = {};
               snprintf(s, sizeof(s) - 1, "#<gensym %s %d>", tok.u.ident, gensymid++); 
               gs.tok.u.ident = internstr(s);
               tok = gs.tok;
               gs.next = gensyms;
               gensyms = gs;
            }
         }
         body->push(tok);
      }
      body->pop();

      for let gs = gensyms, next *Gensyms #?; gs; gs = next {
         next = gs.next;
         free(gs);
      }
      
      c.params = params->move(P.alloc);
      c.body = body->move(P.alloc);
      return c;
   }

   let loc = P.tokloc;
   let tok Tok #?;
   let cs Vec<MacroCase> = {};
   if lexpeek(P).t == '(' {
      cs->push(parsemacrocase(P));
   } else {
      lexexpect(P, '{');
      while !lexmatch(P, &tok, '}') {
         cs->push(parsemacrocase(P));      
         if !lexmatch(P, &tok, ',') {
            lexexpect(P, '}');
            break;
         }
      }
   }

   return putdecl(P, loc, { name, loc, .u: :Macro { cs->move(P.alloc) }});
}

fn parsedecls(P *Parser, yield DeclYielder, yarg *void, toplevel bool) void {
   let tok = Tok { .loc: P.tokloc },
       decl *Decl = {},
       externp = #f,
       name *const u8 = #null;

   if lexmatch(P, &tok, :kw_extern) {
      externp = #t;
      if (tok = lexpeek(P)).t != :kw_fn and tok.t != :kw_static {
         err(P, tok.loc, "expected `fn' or `static' after `extern'");
      }
   }

   switch {
   case lexmatch(P, &tok, :kw_fn);
      let name = lexmatch(P, &tok, :ident) ? tok.u.ident : #null;
      decl = parsefn(P, externp, name);

   case lexmatch(P, &tok, :kw_import);
      let path = (tok = lexexpects(P, :str, "import path")).u.str.#ptr;
      let decls = doimport(P, path);
      foreach(decl, _, decls) {
         let decl = putdecl(P, tok.loc, decl);
         if yield {
            yield(decl, yarg);
         }
      }
      lexexpect(P, ';');      
      return;

   case lexmatch(P, &tok, :kw_enum);
      if lexmatch(P, &tok, :kw_union) {
         let name = lexexpect(P, :ident).u.ident;
         parseagg(P, :EUnion, name, &decl);
      } else {
         let name = lexexpect(P, :ident).u.ident;
         let loc = P.tokloc;
         let ty = parseenum(P, name, #{lax} #f);
         decl = putdecl(P, loc, { name, loc, .u: :Ty(ty) });
      }

   case lexmatch(P, &tok, :kw_struct);
      let name = lexexpect(P, :ident).u.ident;
      parseagg(P, :Struct, name, &decl);

   case lexmatch(P, &tok, :kw_union);
      let name = lexexpect(P, :ident).u.ident;
      parseagg(P, :Union, name, &decl);

   case lexmatch(P, &tok, :kw_static);
      struct Arg {
         P *Parser,
         externp bool,
         toplevel bool,
         yield DeclYielder,
         yarg *void,
      }
      fn varyield(decl *Decl, arg *void) void {
         let a *Arg = arg;
         let Var = decl.u.Static;
         if !a.toplevel and !a.externp and Var.fwd {
            err(a.P, decl.loc, "static variable inside function cannot be forward-declared");
         }
         if !a.toplevel and a.externp and !Var.fwd {
            err(a.P, decl.loc, "extern variable inside function cannot be initialized");
         }
         if a.P.is_header and a.externp and !Var.fwd {
            err(a.P, decl.loc, "extern variable inside header cannot be initialized");
         }
         if a.yield {
            a.yield(decl, a.yarg);
         }
      }
      parsevardecl(P, toplevel, externp, #{let?} #t, &varyield, &Arg { P, externp, toplevel, yield, yarg });
      return;

   case lexmatch(P, &tok, :kw_def);
      do {
         let tok = lexexpect(P, :ident),
             name = tok.u.ident,
             ini Expr #?,
             ty *const Type = #null;

         if lexmatch(P, #null, '=') {
            ini = parseexpr(P);
            ty = unconstify(ini.ty);
         } else {
            ty = parsetype(P);
            lexexpect(P, '=');
            ini = parseexpr(P);
         }
         if !typematchestarg(ty, ini.ty) {
            err(P, ini.loc, "incompatible initializer (%t, expected %t)", ini.ty, ty);
         }
         fold(&ini);
         yield(putdecl(P, tok.loc, {
            name, tok.loc, .u: :Def(ini)
         }), yarg);
         if !lexmatch(P, &tok, ',') {
            lexexpects(P, ';', "`,' or `;'");
            break;
         }
      } while !lexmatch(P, &tok, ';');
      return;
   
   case lexmatch(P, &tok, :kw_defmacro);
      let name = lexexpects(P, :ident, "macro name").u.ident;
      decl = parsemacro(P, name);

   case else;
      fatal(P, tok.loc, "expected declaration (near %qT)", tok);
   }
    
   if yield != #null and decl != #null {
      yield(decl, yarg);
   }
}

extern fn parse(P *Parser) [#]Decl {
   let aralloc = Arena {};
   let alloc = Allocator { &aralloc, &Arena:allocf, #null };
   let decls Vec<Decl> = {};
   P.alloc = &alloc;
   P.curenv = mkenv(#null, P.alloc);
   if primenv == #null {
      primenv = mkenv(#null, P.alloc);
      putprimtypes(primenv);
   }

   while !P.eof {
      fn yield(decl *Decl, arg *void) void {
         let decls *Vec<Decl> = arg;
         decls->push(*decl);
      }
      parsedecls(P, &yield, &decls, #{toplevel} #t);
      if lexmatch(P, #null, :eof) {
         break;
      }
   }

   envfree(P.curenv);
   aralloc->destroy();
   return decls.dat[0::decls.len];
}

extern fn parser_init(P *Parser, path *const u8) void {
   assert(NUM_KEYWORDS - 1 < '!', "2manykw");
   *P = {};
   P.curfile = path;
   if (P.fp = fopen(path, "r")) == #null {
      perror(path);
      exit(1);
   }
   P.tokloc = (P.curloc = { addfilepath(path), 0, 1, 1 });
   P.peekchr = :None;
}