First public release

2 files changed, 1418 insertions, 0 deletions

diff --git a/parser/parser.go b/parser/parser.go
new file mode 100644
index 0000000..65007b7
--- /dev/null
+++ b/parser/parser.go
@@ -0,0 +1,1168 @@
+package parser
+
+import (
+	"fmt"
+	"strconv"
+
+	"usebox.net/lang/ast"
+	"usebox.net/lang/errors"
+	"usebox.net/lang/tokens"
+)
+
+// XXX: duplicated
+const runtime = "<rt>"
+
+type Env struct {
+	env    map[string]ast.Type
+	parent *Env
+}
+
+func NewEnv(parent *Env) *Env {
+	return &Env{make(map[string]ast.Type), parent}
+}
+
+func (e *Env) Get(key string, local bool) (ast.Type, bool) {
+	if v, ok := e.env[key]; ok {
+		return v, true
+	}
+	if !local && e.parent != nil {
+		return e.parent.Get(key, local)
+	}
+	return ast.TypeNone, false
+}
+
+func (e *Env) Set(key string, typ ast.Type) *Env {
+	n := e
+	if _, ok := e.Get(key, false); ok {
+		n = NewEnv(e)
+	}
+	n.env[key] = typ
+	return n
+}
+
+type Parser struct {
+	tokens      []tokens.Token
+	pos         int
+	env         *Env
+	structs     map[string]*Env
+	currFuncRet *ast.Type
+	currLoop    bool
+}
+
+func NewParser(builtIns map[string]ast.Type) Parser {
+	global := NewEnv(nil)
+	for k, v := range builtIns {
+		// not shadowing any value
+		global.Set(k, v)
+	}
+
+	return Parser{env: global, structs: make(map[string]*Env)}
+}
+
+func (p *Parser) Parse(tokens []tokens.Token) ([]ast.Expr, error) {
+	var errs []error
+	var exprs []ast.Expr
+
+	p.tokens = tokens
+	p.pos = 0
+
+	for !p.end() {
+		expr, err := p.statement()
+		if err != nil {
+			errs = append(errs, err)
+			p.recover()
+			continue
+		}
+		exprs = append(exprs, expr)
+	}
+
+	if len(errs) > 0 {
+		return nil, errors.ErrorList{Errors: errs}
+	}
+
+	return exprs, nil
+}
+
+func (p *Parser) recover() {
+	p.next()
+
+	for !p.end() {
+		if p.prev().Id == tokens.Semicolon {
+			return
+		}
+		if p.match([]tokens.TokenId{tokens.Def, tokens.Var, tokens.Const, tokens.If, tokens.Return, tokens.For}) {
+			p.back()
+			return
+		}
+
+		p.next()
+	}
+}
+
+func (p *Parser) next() tokens.Token {
+	if !p.end() {
+		p.pos++
+		return p.prev()
+	}
+	return p.curr()
+}
+
+func (p *Parser) back() {
+	if p.pos != 0 {
+		p.pos--
+	}
+}
+
+func (p *Parser) prev() tokens.Token {
+	return p.tokens[p.pos-1]
+}
+
+func (p *Parser) curr() tokens.Token {
+	return p.tokens[p.pos]
+}
+
+func (p *Parser) end() bool {
+	return p.curr().Id == tokens.Eof
+}
+
+func (p *Parser) check(id tokens.TokenId) bool {
+	if p.end() {
+		return false
+	}
+	return p.curr().Id == id
+}
+
+func (p *Parser) match(ids []tokens.TokenId) bool {
+	for _, t := range ids {
+		if p.check(t) {
+			p.next()
+			return true
+		}
+	}
+	return false
+}
+
+func (p *Parser) statement() (ast.Expr, error) {
+	if p.match([]tokens.TokenId{tokens.Var, tokens.Const}) {
+		return p.declaration()
+	}
+
+	if p.check(tokens.Break) {
+		p.next()
+		return p.breakStmt()
+	}
+
+	if p.check(tokens.Continue) {
+		p.next()
+		return p.continueStmt()
+	}
+
+	if p.check(tokens.Return) {
+		p.next()
+		return p.returnStmt()
+	}
+
+	if p.check(tokens.For) {
+		p.next()
+		return p.forStmt()
+	}
+
+	if p.check(tokens.If) {
+		return p.ifElse()
+	}
+
+	if p.check(tokens.LBrace) {
+		return p.block()
+	}
+
+	if p.check(tokens.Def) {
+		p.next()
+		return p.definition()
+	}
+
+	expr, err := p.expr()
+	if err != nil {
+		return nil, err
+	}
+	if p.next().Id != tokens.Semicolon {
+		return nil, errors.NewError(errors.ExpectedSemicolon, p.prev().Loc, "';' expected after expression")
+	}
+	return expr, nil
+}
+
+func (p *Parser) expr() (ast.Expr, error) {
+	return p.assign()
+}
+
+func (p *Parser) typ() (*ast.Type, error) {
+	if p.check(tokens.LBracket) {
+		tok := p.next()
+
+		size, err := p.primary()
+		if err != nil {
+			return nil, err
+		}
+
+		if p.next().Id != tokens.RBracket {
+			return nil, errors.NewError(errors.ExpectedRBracket, p.prev().Loc, "']' expected in array definition")
+		}
+
+		typ, err := p.typ()
+		if err != nil {
+			return nil, err
+		}
+
+		if typ.Value.Id == tokens.TArray {
+			return nil, errors.NewError(errors.InvalidType, p.prev().Loc, "invalid array type", typ.String())
+		}
+
+		if size.Resolve().Compare(&ast.TypeNumber) {
+			if v, ok := size.(ast.Literal); ok {
+				tok.Id = tokens.TArray
+				intval := int(v.Numval)
+				return &ast.Type{Value: tok, Ret: typ, Len: &intval}, nil
+			}
+		}
+
+		return nil, errors.NewError(errors.InvalidValue, p.prev().Loc, "invalid value for array size")
+	}
+
+	if !p.match([]tokens.TokenId{tokens.TNumber, tokens.TBool, tokens.TString, tokens.TFunc, tokens.Ident}) {
+		return nil, errors.NewError(errors.ExpectedType, p.curr().Loc, "expected type")
+	}
+	typ := p.prev()
+
+	if typ.Id == tokens.Ident {
+		typ, ok := p.env.Get(typ.Value, false)
+		if !ok || typ.Value.Id != tokens.TStruct {
+			return nil, errors.NewError(errors.ExpectedType, p.curr().Loc, "expected type")
+		}
+		if typ.Inst {
+			return nil, errors.NewError(errors.ExpectedType, p.curr().Loc, "expected type found instance of", typ.String())
+		}
+		// this is an instance of the struct
+		typ.Inst = true
+		return &typ, nil
+	}
+
+	if typ.Id != tokens.TFunc {
+		return &ast.Type{Value: typ}, nil
+	}
+
+	if p.next().Id != tokens.LParen {
+		return nil, errors.NewError(errors.ExpectedLParen, p.prev().Loc, "'(' expected in function type")
+	}
+
+	params := make([]ast.Type, 0, 16)
+	for !p.check(tokens.RParen) {
+		typ, err := p.typ()
+		if err != nil {
+			return nil, err
+		}
+
+		params = append(params, *typ)
+		if !p.check(tokens.Comma) {
+			break
+		}
+		p.next()
+	}
+	p.next()
+
+	var ret *ast.Type
+	if !p.check(tokens.Semicolon) && !p.check(tokens.Assign) && !p.check(tokens.RParen) && !p.check(tokens.LBrace) {
+		if typ, err := p.typ(); err != nil {
+			return nil, err
+		} else {
+			ret = typ
+		}
+	}
+
+	return &ast.Type{Value: typ, Params: params, Ret: ret}, nil
+}
+
+func (p *Parser) definition() (ast.Expr, error) {
+	name := p.next()
+	if name.Id != tokens.Ident {
+		return nil, errors.NewError(errors.ExpectedIdent, name.Loc, "expected identifier")
+	}
+
+	if p.check(tokens.LBrace) {
+		return p.strctDecl(name)
+	}
+
+	return p.funcDecl(name)
+}
+
+func (p *Parser) strctDecl(name tokens.Token) (ast.Expr, error) {
+	if v, ok := p.env.Get(name.Value, true); ok {
+		loc := v.Value.Loc.String()
+		if v.Value.Loc.File == "" {
+			loc = runtime
+		}
+		return nil, errors.NewError(errors.AlreadyDeclared, name.Loc, "struct", name.String(), "already declared in", loc)
+	}
+
+	p.env = p.env.Set(name.Value, *ast.NewStructType(name))
+	pEnv := p.env
+	sEnv := NewEnv(pEnv)
+	p.env = sEnv
+
+	expr, err := p.strctBlock()
+	if err != nil {
+		return nil, err
+	}
+
+	if len(sEnv.env) == 0 {
+		return nil, errors.NewError(errors.InvalidValue, name.Loc, "empty struct")
+	}
+
+	p.structs[name.Value] = sEnv
+	p.env = pEnv
+
+	return ast.Struct{Name: name, Body: expr.(ast.Block)}, nil
+}
+
+func (p *Parser) funcDecl(name tokens.Token) (ast.Expr, error) {
+	if p.next().Id != tokens.LParen {
+		return nil, errors.NewError(errors.ExpectedLParen, p.prev().Loc, "'(' expected in function declaration")
+	}
+
+	params := make([]ast.Var, 0, 16)
+	paramTypes := make([]ast.Type, 0, 16)
+	seen := map[string]tokens.Location{}
+	for !p.check(tokens.RParen) {
+		pname := p.next()
+		if pname.Id != tokens.Ident {
+			return nil, errors.NewError(errors.ExpectedIdent, pname.Loc, "expected parameter name")
+		}
+
+		typ, err := p.typ()
+		if err != nil {
+			return nil, err
+		}
+
+		if prev, ok := seen[pname.Value]; ok {
+			return nil, errors.NewError(errors.AlreadyDeclared, pname.Loc, "parameter", pname.String(), "already declared in", prev.String())
+		}
+		seen[pname.Value] = pname.Loc
+
+		params = append(params, ast.Var{Name: pname, Type: *typ})
+		paramTypes = append(paramTypes, *typ)
+		if !p.check(tokens.Comma) {
+			break
+		}
+		p.next()
+	}
+	p.next()
+
+	var ret *ast.Type
+	if !p.check(tokens.LBrace) {
+		if typ, err := p.typ(); err != nil {
+			return nil, err
+		} else {
+			ret = typ
+		}
+	}
+
+	if v, ok := p.env.Get(name.Value, true); ok {
+		loc := v.Value.Loc.String()
+		if v.Value.Loc.File == "" {
+			loc = runtime
+		}
+		return nil, errors.NewError(errors.AlreadyDeclared, name.Loc, "function", name.String(), "already declared in", loc)
+	}
+	p.env = p.env.Set(name.Value, *ast.NewFuncType(name, paramTypes, ret))
+
+	oldFuncRet := p.currFuncRet
+	if ret != nil {
+		p.currFuncRet = ret
+	} else {
+		p.currFuncRet = &ast.TypeNone
+	}
+	defer func() {
+		p.currFuncRet = oldFuncRet
+	}()
+
+	for _, v := range params {
+		p.env = p.env.Set(v.Name.Value, v.Type)
+	}
+
+	expr, err := p.block()
+	if err != nil {
+		return nil, err
+	}
+
+	// return checks?
+	return ast.Func{Name: name, Params: params, Ret: ret, Body: expr.(ast.Block)}, nil
+}
+
+func (p *Parser) exprList() (ast.Expr, error) {
+	if p.check(tokens.LBracket) {
+		p.next()
+		vals := make([]ast.Expr, 0, 16)
+		if !p.check(tokens.RBracket) {
+			var prev ast.Expr
+			for {
+				val, err := p.expr()
+				if err != nil {
+					return nil, err
+				}
+				if prev != nil && !prev.Resolve().Compare(val.Resolve()) {
+					return nil, errors.NewError(errors.TypeMismatch, p.prev().Loc, "type mismatch in expression list: found", val.Resolve().String(), "expected", prev.Resolve().String())
+				}
+				prev = val
+
+				vals = append(vals, val)
+				if !p.check(tokens.Comma) {
+					break
+				}
+				p.next()
+			}
+			if !p.check(tokens.RBracket) {
+				return nil, errors.NewError(errors.ExpectedRBracket, p.prev().Loc, "']' expected to end expression list")
+			}
+		}
+		p.next()
+		if len(vals) == 0 {
+			return nil, errors.NewError(errors.InvalidValue, p.prev().Loc, "empty expression list")
+		}
+
+		return ast.ExprList{Exprs: vals}, nil
+	}
+
+	return p.expr()
+}
+
+func (p *Parser) decl(con bool) (ast.Expr, error) {
+	name := p.next()
+	if name.Id != tokens.Ident {
+		return nil, errors.NewError(errors.ExpectedIdent, name.Loc, "expected identifier")
+	}
+
+	typ, err := p.typ()
+	if err != nil {
+		return nil, err
+	}
+
+	if typ.Value.Id == tokens.TStruct {
+		if _, ok := p.structs[typ.Value.Value]; !ok {
+			return nil, errors.NewError(errors.RecursiveStruct, p.curr().Loc, "recursive definition of", typ.String())
+		}
+	}
+
+	var initv ast.Expr
+	if p.check(tokens.Assign) {
+		p.next()
+		var err error
+		initv, err = p.exprList()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if p.next().Id != tokens.Semicolon {
+		return nil, errors.NewError(errors.ExpectedSemicolon, p.prev().Loc, "';' expected after expression")
+	}
+
+	if v, ok := p.env.Get(name.Value, true); ok {
+		loc := v.Value.Loc.String()
+		if v.Value.Loc.File == "" {
+			loc = runtime
+		}
+		return nil, errors.NewError(errors.AlreadyDeclared, name.Loc, name.String(), "already declared in", loc)
+	}
+
+	if initv != nil {
+		if v, ok := initv.(ast.ExprList); ok {
+			if typ.Value.Id != tokens.TArray {
+				return nil, errors.NewError(errors.InvalidValue, name.Loc, "expression list to initialize a type", typ.String())
+			}
+			if *typ.Len != len(v.Exprs) {
+				return nil, errors.NewError(errors.InvalidValue, name.Loc, "invalid number of elements in expression list to initialize a type", typ.String())
+			}
+			if !typ.Ret.Compare(initv.Resolve()) {
+				return nil, errors.NewError(errors.TypeMismatch, name.Loc, "type mismatch expected list of", typ.Ret.String(), "found", initv.Resolve().String())
+			}
+		} else if !typ.Compare(initv.Resolve()) {
+			return nil, errors.NewError(errors.TypeMismatch, name.Loc, "type mismatch expected", typ.String(), "found", initv.Resolve().String())
+		}
+		if initv.Resolve().Value.Id == tokens.TArray || initv.Resolve().Value.Id == tokens.TStruct {
+			if !con && initv.Resolve().ResolveConst() {
+				return nil, errors.NewError(errors.TypeMismatch, name.Loc, "variable cannot be used as referece to constant")
+			}
+			typ.Ref = true
+		}
+	}
+	if typ.Value.Id == tokens.TStruct {
+		// it is an instance
+		p.structs[name.Value] = p.structs[typ.Value.Value]
+		typ.Inst = true
+	}
+	if con {
+		if initv == nil {
+			return nil, errors.NewError(errors.ExpectedAssign, name.Loc, "expected assignation in constant declaration")
+		}
+		if typ.Value.Id == tokens.TArray {
+			// allow changing reference but not the values of the array
+			typ.Ret.Const = true
+		} else {
+			typ.Const = true
+		}
+	}
+
+	p.env = p.env.Set(name.Value, *typ)
+	return ast.Var{Name: name, Type: *typ, Initv: initv}, nil
+}
+
+func (p *Parser) declaration() (ast.Expr, error) {
+	if p.prev().Id == tokens.Const {
+		return p.decl(true)
+	}
+	return p.decl(false)
+}
+
+func (p *Parser) continueStmt() (ast.Expr, error) {
+	if p.next().Id != tokens.Semicolon {
+		return nil, errors.NewError(errors.ExpectedSemicolon, p.prev().Loc, "';' expected after expression")
+	}
+
+	if !p.currLoop {
+		return nil, errors.NewError(errors.InvalidOperation, p.curr().Loc, "continue without loop")
+	}
+
+	return ast.Continue{Loc: p.curr().Loc}, nil
+}
+
+func (p *Parser) breakStmt() (ast.Expr, error) {
+	if p.next().Id != tokens.Semicolon {
+		return nil, errors.NewError(errors.ExpectedSemicolon, p.prev().Loc, "';' expected after expression")
+	}
+
+	if !p.currLoop {
+		return nil, errors.NewError(errors.InvalidOperation, p.curr().Loc, "break without loop")
+	}
+
+	return ast.Break{Loc: p.curr().Loc}, nil
+}
+
+func (p *Parser) returnStmt() (ast.Expr, error) {
+	if p.currFuncRet == nil {
+		return nil, errors.NewError(errors.InvalidOperation, p.prev().Loc, "return without function call")
+	}
+
+	var isError bool
+	if p.check(tokens.TagE) {
+		p.next()
+		isError = true
+	}
+
+	if p.check(tokens.Semicolon) {
+		p.next()
+		if p.currFuncRet.Value.Id != tokens.None {
+			return nil, errors.NewError(errors.TypeMismatch, p.prev().Loc, "type mismatch in return value, expected", p.currFuncRet.String())
+		}
+		return ast.Return{Loc: p.curr().Loc, Error: isError}, nil
+	}
+
+	expr, err := p.expr()
+	if err != nil {
+		return nil, err
+	}
+
+	if p.next().Id != tokens.Semicolon {
+		return nil, errors.NewError(errors.ExpectedSemicolon, p.prev().Loc, "';' expected after expression")
+	}
+
+	exprRet := expr.Resolve()
+	if exprRet == nil {
+		exprRet = &ast.TypeNone
+	} else {
+		if exprRet.Value.Id == tokens.TArray || exprRet.Value.Id == tokens.TStruct {
+			if v, ok := expr.(ast.Variable); ok {
+				if val, ok := p.env.Get(v.Name.Value, true); ok && !val.Ref {
+					return nil, errors.NewError(errors.InvalidOperation, p.prev().Loc, "returning a local value of type", exprRet.String())
+				}
+			}
+		}
+	}
+
+	if !p.currFuncRet.Compare(exprRet) {
+		return nil, errors.NewError(errors.TypeMismatch, p.prev().Loc, "type mismatch in return value, expected", p.currFuncRet.String(), "found", exprRet.String())
+	}
+
+	return ast.Return{Value: expr, Loc: p.prev().Loc, Error: isError}, nil
+}
+
+func (p *Parser) forBody() (ast.Expr, error) {
+	oldCurrLoop := p.currLoop
+	p.currLoop = true
+	defer func() {
+		p.currLoop = oldCurrLoop
+	}()
+
+	return p.block()
+}
+
+func (p *Parser) forStmt() (ast.Expr, error) {
+	var expr ast.Expr
+	var err error
+
+	if !p.check(tokens.LBrace) {
+		if p.check(tokens.Ident) {
+			ident := p.next()
+			if p.check(tokens.In) {
+				p.next()
+				expr, err = p.expr()
+				if err != nil {
+					return nil, err
+				}
+				if expr.Resolve().Value.Id != tokens.TArray {
+					return nil, errors.NewError(errors.TypeMismatch, p.next().Loc, "expected array in for-in statement found", expr.Resolve().String())
+				}
+
+				pEnv := p.env
+				p.env = NewEnv(pEnv)
+				defer func() {
+					p.env = pEnv
+				}()
+				p.env = p.env.Set(ident.Value, *expr.Resolve().Ret)
+
+				stmts, err := p.forBody()
+				if err != nil {
+					return nil, err
+				}
+				return ast.ForIn{Name: ident, Expr: expr, Stmts: stmts}, nil
+			}
+			p.back()
+		}
+
+		expr, err = p.expr()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	stmts, err := p.forBody()
+	if err != nil {
+		return nil, err
+	}
+	return ast.For{Cond: expr, Stmts: stmts}, nil
+}
+
+func (p *Parser) ifElse() (ast.Expr, error) {
+	ifTok := p.next()
+	expr, err := p.expr()
+	if err != nil {
+		return nil, err
+	}
+	ifBlock, err := p.block()
+	if err != nil {
+		return nil, err
+	}
+
+	var elseBlock ast.Expr
+	if p.check(tokens.Else) {
+		p.next()
+		elseBlock, err = p.block()
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		elseBlock = ast.Literal{Value: tokens.Token{Id: tokens.None, Loc: ifTok.Loc}}
+	}
+	return ast.IfElse{Cond: expr, True: ifBlock, False: elseBlock}, nil
+}
+
+func (p *Parser) strctBlock() (ast.Expr, error) {
+	definitions := make([]ast.Expr, 0, 256)
+
+	if p.next().Id != tokens.LBrace {
+		return nil, errors.NewError(errors.ExpectedLBrace, p.prev().Loc, "'{' expected to open block")
+	}
+
+	for !p.check(tokens.RBrace) && !p.end() {
+		if p.check(tokens.Def) {
+			p.next()
+			decl, err := p.definition()
+			if err != nil {
+				return nil, err
+			}
+			definitions = append(definitions, decl)
+			continue
+		}
+		if p.match([]tokens.TokenId{tokens.Var, tokens.Const}) {
+			decl, err := p.declaration()
+			if err != nil {
+				return nil, err
+			}
+			definitions = append(definitions, decl)
+			continue
+		}
+		return nil, errors.NewError(errors.ExpectedDefinition, p.next().Loc, "expected definition in a struct block")
+	}
+
+	next := p.next()
+	if next.Id != tokens.RBrace {
+		// MUST be EOF
+		return nil, errors.NewError(errors.ExpectedRBrace, next.Loc, "'}' expected to close block, end of file found")
+	}
+
+	return ast.Block{Stmts: definitions}, nil
+}
+
+func (p *Parser) block() (ast.Expr, error) {
+	pEnv := p.env
+	p.env = NewEnv(pEnv)
+	defer func() {
+		p.env = pEnv
+	}()
+
+	statements := make([]ast.Expr, 0, 256)
+
+	if p.next().Id != tokens.LBrace {
+		return nil, errors.NewError(errors.ExpectedLBrace, p.prev().Loc, "'{' expected to open block")
+	}
+
+	for !p.check(tokens.RBrace) && !p.end() {
+		decl, err := p.statement()
+		if err != nil {
+			return nil, err
+		}
+		statements = append(statements, decl)
+	}
+
+	next := p.next()
+	if next.Id != tokens.RBrace {
+		// MUST be EOF
+		return nil, errors.NewError(errors.ExpectedRBrace, next.Loc, "'}' expected to close block, end of file found")
+	}
+
+	return ast.Block{Stmts: statements}, nil
+}
+
+func (p *Parser) assign() (ast.Expr, error) {
+	expr, err := p.or()
+	if err != nil {
+		return nil, err
+	}
+
+	if p.check(tokens.Assign) {
+		tok := p.next()
+		value, err := p.expr()
+		if err != nil {
+			return nil, err
+		}
+
+		left := expr
+		env := p.env
+
+		if obj, ok := expr.(ast.GetExpr); ok {
+			oType := obj.Object.Resolve()
+			sEnv, ok := p.structs[oType.Value.Value]
+			if !ok {
+				// shouldn't happen
+				return nil, errors.NewError(errors.Unexpected, oType.Value.Loc, "undeclared struct", oType.String())
+			}
+			env = sEnv
+			expr = obj.Expr
+		}
+
+		v, ok := expr.(ast.Variable)
+		if !ok {
+			return nil, errors.NewError(errors.InvalidTarget, tok.Loc, "invalid assignment target")
+		}
+
+		typ, ok := env.Get(v.Name.Value, false)
+		if !ok {
+			return nil, errors.NewError(errors.UndefinedIdent, v.Name.Loc, "undeclared variable", v.String())
+		}
+		if typ.Value.Id == tokens.TArray && v.Index != nil {
+			typ = *typ.Ret
+		}
+		if !typ.Compare(value.Resolve()) {
+			return nil, errors.NewError(errors.InvalidValue, tok.Loc, "invalid value in assignation, expected", typ.String(), "found", value.Resolve().String())
+		}
+		if typ.Value.Id == tokens.TArray || typ.Value.Id == tokens.TStruct {
+			if !typ.Ref {
+				return nil, errors.NewError(errors.TypeMismatch, v.Name.Loc, "variable cannot be converted to a reference", v.String())
+			}
+			if !typ.ResolveConst() && value.Resolve().ResolveConst() {
+				return nil, errors.NewError(errors.TypeMismatch, v.Name.Loc, "variable cannot be used as referece to constant")
+			}
+		}
+		if typ.Const {
+			return nil, errors.NewError(errors.AssignConst, v.Name.Loc, "value cannot be assigned to constant")
+		}
+		return ast.Assign{Left: left, Right: value, Loc: tok.Loc}, nil
+	}
+
+	return expr, nil
+}
+
+func (p *Parser) or() (ast.Expr, error) {
+	expr, err := p.and()
+	if err != nil {
+		return nil, err
+	}
+
+	if p.check(tokens.Or) {
+		op := p.next()
+		right, err := p.and()
+		if err != nil {
+			return nil, err
+		}
+		expr = ast.Binary{Left: expr, Op: op, Right: right, Type: &ast.TypeBool}
+	}
+
+	return expr, nil
+}
+
+func (p *Parser) and() (ast.Expr, error) {
+	expr, err := p.equality()
+	if err != nil {
+		return nil, err
+	}
+
+	if p.check(tokens.And) {
+		op := p.next()
+		right, err := p.equality()
+		if err != nil {
+			return nil, err
+		}
+		expr = ast.Binary{Left: expr, Op: op, Right: right, Type: &ast.TypeBool}
+	}
+
+	return expr, nil
+}
+
+func (p *Parser) equality() (ast.Expr, error) {
+	expr, err := p.comparison()
+	if err != nil {
+		return nil, err
+	}
+
+	for p.match([]tokens.TokenId{tokens.Eq, tokens.Ne}) {
+		op := p.prev()
+		right, err := p.comparison()
+		if err != nil {
+			return nil, err
+		}
+
+		if !expr.Resolve().Compare(right.Resolve()) {
+			return nil, errors.NewError(errors.TypeMismatch, op.Loc, "type mistmach expected", expr.Resolve().String(), "found", right.Resolve().String())
+		}
+
+		expr = ast.Binary{Left: expr, Op: op, Right: right, Type: &ast.TypeBool}
+	}
+
+	return expr, nil
+}
+
+func (p *Parser) comparison() (ast.Expr, error) {
+	expr, err := p.bitterm()
+	if err != nil {
+		return nil, err
+	}
+
+	for p.match([]tokens.TokenId{tokens.Gt, tokens.Ge, tokens.Lt, tokens.Le}) {
+		op := p.prev()
+		right, err := p.bitterm()
+		if err != nil {
+			return nil, err
+		}
+
+		if !expr.Resolve().Compare(&ast.TypeNumber) {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", expr.Resolve().String())
+		}
+		if !right.Resolve().Compare(&ast.TypeNumber) {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", right.Resolve().String())
+		}
+
+		expr = ast.Binary{Left: expr, Op: op, Right: right, Type: &ast.TypeBool}
+	}
+
+	return expr, nil
+}
+
+func (p *Parser) bitterm() (ast.Expr, error) {
+	expr, err := p.term()
+	if err != nil {
+		return nil, err
+	}
+
+	for p.match([]tokens.TokenId{tokens.BitShl, tokens.BitShr, tokens.BitOr, tokens.BitXor}) {
+		op := p.prev()
+		right, err := p.term()
+		if err != nil {
+			return nil, err
+		}
+
+		if !expr.Resolve().Compare(&ast.TypeNumber) {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", expr.Resolve().String())
+		}
+		if !right.Resolve().Compare(&ast.TypeNumber) {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", right.Resolve().String())
+		}
+
+		expr = ast.Binary{Left: expr, Op: op, Right: right}
+	}
+
+	return expr, nil
+}
+
+func (p *Parser) term() (ast.Expr, error) {
+	expr, err := p.bitfactor()
+	if err != nil {
+		return nil, err
+	}
+
+	for p.match([]tokens.TokenId{tokens.Sub, tokens.Add}) {
+		op := p.prev()
+		right, err := p.bitfactor()
+		if err != nil {
+			return nil, err
+		}
+
+		if !expr.Resolve().Compare(&ast.TypeNumber) {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", expr.Resolve().String())
+		}
+		if !right.Resolve().Compare(&ast.TypeNumber) {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", right.Resolve().String())
+		}
+
+		expr = ast.Binary{Left: expr, Op: op, Right: right}
+	}
+
+	return expr, nil
+}
+
+func (p *Parser) bitfactor() (ast.Expr, error) {
+	expr, err := p.factor()
+	if err != nil {
+		return nil, err
+	}
+
+	if p.check(tokens.BitAnd) {
+		op := p.next()
+		right, err := p.factor()
+		if err != nil {
+			return nil, err
+		}
+
+		if !expr.Resolve().Compare(&ast.TypeNumber) {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", expr.Resolve().String())
+		}
+		if !right.Resolve().Compare(&ast.TypeNumber) {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", right.Resolve().String())
+		}
+
+		expr = ast.Binary{Left: expr, Op: op, Right: right}
+	}
+
+	return expr, nil
+}
+
+func (p *Parser) factor() (ast.Expr, error) {
+	expr, err := p.unary()
+	if err != nil {
+		return nil, err
+	}
+
+	for p.match([]tokens.TokenId{tokens.Div, tokens.Mul, tokens.Mod}) {
+		op := p.prev()
+		right, err := p.unary()
+		if err != nil {
+			return nil, err
+		}
+
+		if !expr.Resolve().Compare(&ast.TypeNumber) {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", expr.Resolve().String())
+		}
+		if !right.Resolve().Compare(&ast.TypeNumber) {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", right.Resolve().String())
+		}
+
+		expr = ast.Binary{Left: expr, Op: op, Right: right}
+	}
+
+	return expr, nil
+}
+
+func (p *Parser) unary() (ast.Expr, error) {
+	if p.match([]tokens.TokenId{tokens.TestE, tokens.Not, tokens.Neg, tokens.Sub}) {
+		op := p.prev()
+		right, err := p.unary()
+		if err != nil {
+			return nil, err
+		}
+		if (op.Id == tokens.Sub || op.Id == tokens.Neg) && right.Resolve().Value.Id != tokens.TNumber {
+			return nil, errors.NewError(errors.InvalidOperation, op.Loc, "invalid operation for type", right.Resolve().String())
+		}
+		return ast.Unary{Op: op, Right: right}, nil
+	}
+
+	return p.call()
+}
+
+func (p *Parser) call() (ast.Expr, error) {
+	expr, err := p.primary()
+	if err != nil {
+		return nil, err
+	}
+
+	for {
+		if p.check(tokens.LBracket) {
+			loc := p.next().Loc
+
+			if expr.Resolve().Value.Id != tokens.TArray {
+				return nil, errors.NewError(errors.NotIndexable, loc, "value is not indexable")
+			}
+
+			index, err := p.expr()
+			if err != nil {
+				return nil, err
+			}
+			if !index.Resolve().Compare(&ast.TypeNumber) {
+				return nil, errors.NewError(errors.InvalidValue, p.prev().Loc, "invalid index value")
+			}
+
+			if p.next().Id != tokens.RBracket {
+				return nil, errors.NewError(errors.ExpectedRBracket, p.prev().Loc, "']' expected to close index")
+			}
+
+			switch v := expr.(type) {
+			case ast.Variable:
+				v.Index = index
+				expr = v
+			case ast.GetExpr:
+				val := v.Expr.(ast.Variable)
+				val.Index = index
+				v.Expr = val
+				expr = v
+			default:
+				// shouldn't happen
+				return nil, errors.NewError(errors.Unexpected, loc, "value is not indexable")
+			}
+			continue
+		}
+
+		if p.check(tokens.Dot) {
+			loc := p.next().Loc
+			prop := p.next()
+			if prop.Id != tokens.Ident {
+				return nil, errors.NewError(errors.ExpectedIdent, prop.Loc, "expected identifier")
+			}
+			sType := expr.Resolve()
+			if sType.Value.Id != tokens.TStruct {
+				return nil, errors.NewError(errors.NotStruct, loc, "property get on a non struct value")
+			}
+
+			sEnv, ok := p.structs[sType.Value.Value]
+			if !ok {
+				// shouldn't happen
+				return nil, errors.NewError(errors.Unexpected, sType.Value.Loc, "undeclared struct", sType.String())
+			}
+			pType, ok := sEnv.Get(prop.Value, true)
+			if !ok {
+				return nil, errors.NewError(errors.UndefinedIdent, loc, "property", prop.String(), "not defined in", sType.String())
+			}
+
+			expr = ast.GetExpr{Object: expr, Expr: ast.Variable{Name: prop, Type: pType}}
+			continue
+		}
+
+		if p.check(tokens.LParen) {
+			p.next()
+			args := make([]ast.Expr, 0, 16)
+			if !p.check(tokens.RParen) {
+				for {
+					arg, err := p.expr()
+					if err != nil {
+						return nil, err
+					}
+					args = append(args, arg)
+					if !p.check(tokens.Comma) {
+						break
+					}
+					p.next()
+				}
+				if !p.check(tokens.RParen) {
+					return nil, errors.NewError(errors.ExpectedRParen, p.prev().Loc, "')' expected to end function call")
+				}
+			}
+			typ := expr.Resolve()
+			if typ.Value.Id != tokens.TFunc {
+				return nil, errors.NewError(errors.NotCallable, p.next().Loc, "value is not callable")
+			}
+
+			// mostly for println that doesn't have type checks
+			// and will consume any number of arguments
+			if typ.Params != nil {
+				if len(typ.Params) != len(args) {
+					return nil, errors.NewError(errors.CallError, p.next().Loc, fmt.Sprintf("invalid number of arguments in function call: %d expected %d found", len(typ.Params), len(args)))
+				}
+				for n, arg := range args {
+					if !typ.Params[n].Compare(arg.Resolve()) {
+						return nil, errors.NewError(errors.TypeMismatch, p.next().Loc, fmt.Sprintf("type mismatch in function call argument %d: expected %s found %s", n+1, typ.Params[n].String(), arg.Resolve().String()))
+					}
+				}
+			}
+			expr = ast.Call{Callee: expr, Loc: p.next().Loc, Args: args}
+			continue
+		}
+		break
+	}
+	return expr, nil
+}
+
+func (p *Parser) primary() (ast.Expr, error) {
+	if p.match([]tokens.TokenId{tokens.True, tokens.False}) {
+		return ast.Literal{Value: p.prev(), Type: ast.TypeBool}, nil
+	} else if p.check(tokens.String) {
+		return ast.Literal{Value: p.next(), Type: ast.TypeString}, nil
+	} else if p.check(tokens.Ident) {
+		value := p.next()
+
+		typc, ok := p.env.Get(value.Value, false)
+		if !ok {
+			return nil, errors.NewError(errors.UndefinedIdent, value.Loc, "undeclared variable", value.String())
+		}
+		if typc.Value.Id == tokens.TStruct && !typc.Inst {
+			return nil, errors.NewError(errors.InvalidValue, value.Loc, value.String(), "is not an instance")
+		}
+
+		return ast.Variable{Name: value, Type: typc}, nil
+	} else if p.check(tokens.Char) {
+		value := p.next()
+		value.Id = tokens.Number
+		nval := byte(value.Value[0])
+		return ast.Literal{Value: value, Numval: ast.Number(nval), Type: ast.TypeNumber}, nil
+	} else if p.check(tokens.Number) {
+		value := p.next()
+		nval, err := strconv.ParseInt(value.Value, 0, 64)
+		if err != nil {
+			return nil, errors.Error{
+				Code:    errors.FailedNumeric,
+				Message: fmt.Sprintf("[%s] failed to parse numeric value", value.Loc),
+				Err:     err,
+			}
+		}
+		return ast.Literal{Value: value, Numval: ast.Number(nval), Type: ast.TypeNumber}, nil
+	} else if p.check(tokens.LParen) {
+		p.next()
+		expr, err := p.expr()
+		if err != nil {
+			return nil, err
+		}
+		next := p.next()
+		if next.Id != tokens.RParen {
+			found := fmt.Sprintf("'%v'", next.Value)
+			if next.Id == tokens.Eof {
+				found = "end of file"
+			}
+			return nil, errors.NewError(errors.ExpectedRParen, next.Loc, "')' expected after expression,", found, "found")
+		}
+		return ast.Group{Expr: expr}, nil
+	}
+	return nil, errors.NewError(errors.ExpectedExpr, p.curr().Loc, "expression expected")
+}
diff --git a/parser/parser_test.go b/parser/parser_test.go
new file mode 100644
index 0000000..8e97146
--- /dev/null
+++ b/parser/parser_test.go
@@ -0,0 +1,250 @@
+package parser
+
+import (
+	"strings"
+	"testing"
+
+	"usebox.net/lang/ast"
+	"usebox.net/lang/errors"
+	"usebox.net/lang/tokenizer"
+)
+
+func parse(input string) ([]ast.Expr, error) {
+	tr := tokenizer.NewTokenizer("-", strings.NewReader(input))
+	toks, err := tr.Scan()
+	if err != nil {
+		return nil, err
+	}
+	p := NewParser(nil)
+	return p.Parse(toks)
+}
+
+func expectError(t *testing.T, input string, code errors.ErrCode) {
+	_, errs := parse(input)
+	if errs == nil {
+		t.Errorf("expected error and it didn't happen (input: %s)", input)
+	}
+	el, ok := errs.(errors.ErrorList)
+	if !ok {
+		t.Errorf("error list expected (input: %s)", input)
+	} else if len(el.Errors) == 0 {
+		t.Errorf("error list is empty (input: %s)", input)
+	} else {
+		if first, ok := el.Errors[0].(errors.Error); !ok {
+			t.Errorf("error in error list not an Error (input: %s)", input)
+		} else {
+			if first.Code != code {
+				t.Errorf("error %d expected, got %d -> %s (input: %s)", code, first.Code, first, input)
+			}
+		}
+	}
+}
+
+func TestErrorFailedNumeric(t *testing.T) {
+	expectError(t, "var n number = 18446744073709551616;", errors.FailedNumeric)
+}
+
+func TestErrorExpectedRParen(t *testing.T) {
+	expectError(t, "var n number = (1 + 2 ;", errors.ExpectedRParen)
+}
+
+func TestErrorExpectedExpr(t *testing.T) {
+	expectError(t, ";", errors.ExpectedExpr)
+}
+
+func TestErrorExpectedVarName(t *testing.T) {
+	expectError(t, "var number = 1;", errors.ExpectedIdent)
+	expectError(t, "const false;", errors.ExpectedIdent)
+}
+
+func TestErrorExpectedType(t *testing.T) {
+	expectError(t, "var n = 1;", errors.ExpectedType)
+	expectError(t, "const n = 1;", errors.ExpectedType)
+	expectError(t, "def fn(n) { }", errors.ExpectedType)
+	expectError(t, "def fn() { }\nvar a number = fn();", errors.TypeMismatch)
+}
+
+func TestErrorDeclareUndefined(t *testing.T) {
+	expectError(t, "var a number = a;", errors.UndefinedIdent)
+}
+
+func TestErrorExpectedSemiColon(t *testing.T) {
+	expectError(t, "var n number = 1", errors.ExpectedSemicolon)
+	expectError(t, "1 + 1", errors.ExpectedSemicolon)
+}
+
+func TestErrorExpectedFunc(t *testing.T) {
+	expectError(t, "def ;", errors.ExpectedIdent)
+	expectError(t, "def fn;", errors.ExpectedLParen)
+	expectError(t, "def fn(number);", errors.ExpectedIdent)
+	expectError(t, "def fn(a number, number);", errors.ExpectedIdent)
+	expectError(t, "def fn(a, b);", errors.ExpectedType)
+	expectError(t, "def fn(a bool, b);", errors.ExpectedType)
+	expectError(t, "def fn() id;", errors.ExpectedType)
+	expectError(t, "def fn(a number) id;", errors.ExpectedType)
+	expectError(t, "def fn()", errors.ExpectedType)
+	expectError(t, "def fn() {", errors.ExpectedRBrace)
+	expectError(t, "def fn() number {", errors.ExpectedRBrace)
+	expectError(t, "fn(;", errors.UndefinedIdent)
+	expectError(t, "fn(0;", errors.UndefinedIdent)
+	expectError(t, "fn()", errors.UndefinedIdent)
+	expectError(t, "def fn() bool { return 1; }", errors.TypeMismatch)
+	expectError(t, "def fn() { }\ndef fn() { }", errors.AlreadyDeclared)
+}
+
+func TestErrorReturn(t *testing.T) {
+	expectError(t, "return", errors.InvalidOperation)
+	expectError(t, "return true", errors.InvalidOperation)
+	expectError(t, "def fn() { return }", errors.ExpectedExpr)
+	expectError(t, "def fn() { return true }", errors.ExpectedSemicolon)
+	expectError(t, `
+    def fn() [5]number {
+        var local [5]number;
+        return local;
+    }
+    `, errors.InvalidOperation)
+	expectError(t, `
+    def A { var p number; }
+    def fn() A {
+        var local A;
+        return local;
+    }
+    `, errors.InvalidOperation)
+	expectError(t, `
+    def A { var p number; }
+    var g A;
+    def fn() A {
+        var local A;
+        local = g;
+        return local;
+    }
+    "OK";
+    `, errors.TypeMismatch)
+	expectError(t, `
+    var g [3]bool;
+    def fn() [3]bool {
+        var local [3]bool;
+        local = g;
+        return local;
+    }
+    "OK";
+    `, errors.TypeMismatch)
+	expectError(t, `
+    const a [3]number = [1, 2, 3];
+    var b [3]number = a;
+    `, errors.TypeMismatch)
+	expectError(t, `
+    const a [3]number = [1, 2, 3];
+    var b [3]number;
+    var c [3]number = b;
+    c = a;
+    `, errors.TypeMismatch)
+}
+
+func TestErrorExpectedAssign(t *testing.T) {
+	expectError(t, "a = ", errors.UndefinedIdent)
+	expectError(t, "1 = 1;", errors.InvalidTarget)
+	expectError(t, "const a number = 0; a = 1;", errors.AssignConst)
+	expectError(t, "const a [2]number = [0, 1]; a[0] = 1;", errors.AssignConst)
+	expectError(t, `
+    def fn() { }
+    const a func () = fn;
+    a = fn;
+        `, errors.AssignConst)
+}
+
+func TestErrorLoops(t *testing.T) {
+	expectError(t, "continue;", errors.InvalidOperation)
+	expectError(t, "break;", errors.InvalidOperation)
+}
+
+func TestErrorArray(t *testing.T) {
+	expectError(t, "var a [false]number;", errors.InvalidValue)
+	expectError(t, "var a [1]number = 1;", errors.TypeMismatch)
+	expectError(t, "var a []number = [1, 2, 3];", errors.ExpectedExpr)
+	expectError(t, "var a [2]number; var b [5]number = a;", errors.TypeMismatch)
+}
+
+func TestErrorExprList(t *testing.T) {
+	expectError(t, "var a number = [1];", errors.InvalidValue)
+	expectError(t, "var a [1]number = [];", errors.InvalidValue)
+	expectError(t, "var a [2]number = [1, false];", errors.TypeMismatch)
+	expectError(t, "var a [2]number = [1, 2, 3];", errors.InvalidValue)
+	expectError(t, "var a [1]number = [false];", errors.TypeMismatch)
+	expectError(t, "const a number = [1];", errors.InvalidValue)
+	expectError(t, "const a [1]number = [];", errors.InvalidValue)
+	expectError(t, "const a [2]number = [1, false];", errors.TypeMismatch)
+	expectError(t, "const a [2]number = [1, 2, 3];", errors.InvalidValue)
+	expectError(t, "const a [1]number = [false];", errors.TypeMismatch)
+}
+
+func TestErrorIndex(t *testing.T) {
+	expectError(t, "var a [10]number; a[false];", errors.InvalidValue)
+	expectError(t, "var a [10]number; a[\"bad\"];", errors.InvalidValue)
+	expectError(t, "var i bool; var a [10]number; a[i];", errors.InvalidValue)
+	expectError(t, "def fn() { } var a [10]number; a[fn];", errors.InvalidValue)
+	expectError(t, "def fn() bool { return false; } var a [10]number; a[fn()];", errors.InvalidValue)
+	expectError(t, "false[0];", errors.NotIndexable)
+	expectError(t, "10[0];", errors.NotIndexable)
+	expectError(t, "false[0] = 10;", errors.NotIndexable)
+}
+
+func TestErrorFor(t *testing.T) {
+	expectError(t, "for a { }", errors.UndefinedIdent)
+	expectError(t, "for a != 0 { }", errors.UndefinedIdent)
+	expectError(t, "for a in { }", errors.ExpectedExpr)
+	expectError(t, "for a in a { }", errors.UndefinedIdent)
+	expectError(t, "var a number; for i in a { }", errors.TypeMismatch)
+}
+
+func TestErrorStruct(t *testing.T) {
+	expectError(t, "def A { }", errors.InvalidValue)
+	expectError(t, "var a number; a.b;", errors.NotStruct)
+	expectError(t, "def A { var a number; }\nvar a A; a.1;", errors.ExpectedIdent)
+	expectError(t, "def A { var a number; }\ndef A { }", errors.AlreadyDeclared)
+	expectError(t, "def A { var a A; }", errors.RecursiveStruct)
+	expectError(t, "def A { var a number; }\nvar a A;\na.x;", errors.UndefinedIdent)
+	expectError(t, "def A { var a number; }\nA.a;", errors.InvalidValue)
+	expectError(t, "def A { var a number; }\nvar a number; a = A;", errors.InvalidValue)
+	expectError(t, "def A { var a number; }\nvar a A; var b number = a;", errors.TypeMismatch)
+	expectError(t, "def A { var a number; }\nvar a A; var b a;", errors.ExpectedType)
+	expectError(t, `
+    def A { var a number; }
+    def B { var a number; }
+    var a A;
+    var b B = a;
+        `, errors.TypeMismatch)
+	expectError(t, `
+    def fn() {
+        def A {
+            return;
+        }
+    }
+        `, errors.ExpectedDefinition)
+	expectError(t, `
+    for {
+        def A {
+            break;
+        }
+    }
+        `, errors.ExpectedDefinition)
+	expectError(t, `
+    for {
+        def A {
+            continue;
+        }
+    }
+        `, errors.ExpectedDefinition)
+	expectError(t, `
+    def A {
+        var p number;
+        p = 10;
+    }
+        `, errors.ExpectedDefinition)
+	expectError(t, `
+    def A {
+        var p number;
+        println("error");
+    }
+        `, errors.ExpectedDefinition)
+}