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package expr
import (
"fmt"
"reflect"
)
// Type is a reflect.Type alias.
type Type = reflect.Type
type typesTable map[string]Type
var (
nilType = reflect.TypeOf(nil)
boolType = reflect.TypeOf(true)
numberType = reflect.TypeOf(float64(0))
textType = reflect.TypeOf("")
arrayType = reflect.TypeOf([]interface{}{})
mapType = reflect.TypeOf(map[interface{}]interface{}{})
interfaceType = reflect.TypeOf(new(interface{})).Elem()
)
func (n nilNode) Type(table typesTable) (Type, error) {
return nil, nil
}
func (n identifierNode) Type(table typesTable) (Type, error) {
return textType, nil
}
func (n numberNode) Type(table typesTable) (Type, error) {
return numberType, nil
}
func (n boolNode) Type(table typesTable) (Type, error) {
return boolType, nil
}
func (n textNode) Type(table typesTable) (Type, error) {
return textType, nil
}
func (n nameNode) Type(table typesTable) (Type, error) {
if t, ok := table[n.name]; ok {
return t, nil
}
return nil, fmt.Errorf("unknown name %v", n)
}
func (n unaryNode) Type(table typesTable) (Type, error) {
ntype, err := n.node.Type(table)
if err != nil {
return nil, err
}
switch n.operator {
case "!", "not":
if isBoolType(ntype) || isInterfaceType(ntype) {
return boolType, nil
}
return nil, fmt.Errorf(`invalid operation: %v (mismatched type %v)`, n, ntype)
}
return interfaceType, nil
}
func (n binaryNode) Type(table typesTable) (Type, error) {
var err error
ltype, err := n.left.Type(table)
if err != nil {
return nil, err
}
rtype, err := n.right.Type(table)
if err != nil {
return nil, err
}
switch n.operator {
case "==", "!=":
if isComparable(ltype, rtype) {
return boolType, nil
}
return nil, fmt.Errorf(`invalid operation: %v (mismatched types %v and %v)`, n, ltype, rtype)
case "or", "||", "and", "&&":
if (isBoolType(ltype) || isInterfaceType(ltype)) && (isBoolType(rtype) || isInterfaceType(rtype)) {
return boolType, nil
}
return nil, fmt.Errorf(`invalid operation: %v (mismatched types %v and %v)`, n, ltype, rtype)
case "in", "not in":
if (isStringType(ltype) || isInterfaceType(ltype)) && (isStructType(rtype) || isInterfaceType(rtype)) {
return boolType, nil
}
if isArrayType(rtype) || isMapType(rtype) || isInterfaceType(rtype) {
return boolType, nil
}
return nil, fmt.Errorf(`invalid operation: %v (mismatched types %v and %v)`, n, ltype, rtype)
case "<", ">", ">=", "<=":
if (isNumberType(ltype) || isInterfaceType(ltype)) && (isNumberType(rtype) || isInterfaceType(rtype)) {
return boolType, nil
}
return nil, fmt.Errorf(`invalid operation: %v (mismatched types %v and %v)`, n, ltype, rtype)
case "/", "+", "-", "*", "**", "|", "^", "&", "%":
if (isNumberType(ltype) || isInterfaceType(ltype)) && (isNumberType(rtype) || isInterfaceType(rtype)) {
return numberType, nil
}
return nil, fmt.Errorf(`invalid operation: %v (mismatched types %v and %v)`, n, ltype, rtype)
case "..":
if (isNumberType(ltype) || isInterfaceType(ltype)) && (isNumberType(rtype) || isInterfaceType(rtype)) {
return arrayType, nil
}
return nil, fmt.Errorf(`invalid operation: %v (mismatched types %v and %v)`, n, ltype, rtype)
case "~":
if (isStringType(ltype) || isInterfaceType(ltype)) && (isStringType(rtype) || isInterfaceType(rtype)) {
return textType, nil
}
return nil, fmt.Errorf(`invalid operation: %v (mismatched types %v and %v)`, n, ltype, rtype)
}
return interfaceType, nil
}
func (n matchesNode) Type(table typesTable) (Type, error) {
var err error
ltype, err := n.left.Type(table)
if err != nil {
return nil, err
}
rtype, err := n.right.Type(table)
if err != nil {
return nil, err
}
if (isStringType(ltype) || isInterfaceType(ltype)) && (isStringType(rtype) || isInterfaceType(rtype)) {
return boolType, nil
}
return nil, fmt.Errorf(`invalid operation: %v (mismatched types %v and %v)`, n, ltype, rtype)
}
func (n propertyNode) Type(table typesTable) (Type, error) {
ntype, err := n.node.Type(table)
if err != nil {
return nil, err
}
if t, ok := fieldType(ntype, n.property); ok {
return t, nil
}
return nil, fmt.Errorf("%v undefined (type %v has no field %v)", n, ntype, n.property)
}
func (n indexNode) Type(table typesTable) (Type, error) {
ntype, err := n.node.Type(table)
if err != nil {
return nil, err
}
_, err = n.index.Type(table)
if err != nil {
return nil, err
}
if t, ok := indexType(ntype); ok {
return t, nil
}
return nil, fmt.Errorf("invalid operation: %v (type %v does not support indexing)", n, ntype)
}
func (n methodNode) Type(table typesTable) (Type, error) {
ntype, err := n.node.Type(table)
if err != nil {
return nil, err
}
for _, node := range n.arguments {
_, err := node.Type(table)
if err != nil {
return nil, err
}
}
if t, ok := methodType(ntype, n.method); ok {
if f, ok := funcType(t); ok {
return f, nil
}
}
return nil, fmt.Errorf("%v undefined (type %v has no method %v)", n, ntype, n.method)
}
func (n builtinNode) Type(table typesTable) (Type, error) {
for _, node := range n.arguments {
_, err := node.Type(table)
if err != nil {
return nil, err
}
}
switch n.name {
case "len":
// TODO: Add arguments type checks.
return numberType, nil
}
return nil, fmt.Errorf("%v undefined", n)
}
func (n functionNode) Type(table typesTable) (Type, error) {
for _, node := range n.arguments {
_, err := node.Type(table)
if err != nil {
return nil, err
}
}
if t, ok := table[n.name]; ok {
if f, ok := funcType(t); ok {
return f, nil
}
}
return nil, fmt.Errorf("unknown func %v", n)
}
func (n conditionalNode) Type(table typesTable) (Type, error) {
ctype, err := n.cond.Type(table)
if err != nil {
return nil, err
}
if !isBoolType(ctype) && !isInterfaceType(ctype) {
return nil, fmt.Errorf("non-bool %v (type %v) used as condition", n.cond, ctype)
}
t1, err := n.exp1.Type(table)
if err != nil {
return nil, err
}
t2, err := n.exp2.Type(table)
if err != nil {
return nil, err
}
if t1 == nil && t2 != nil {
return t2, nil
}
if t1 != nil && t2 == nil {
return t1, nil
}
if t1 == nil && t2 == nil {
return nilType, nil
}
if t1.AssignableTo(t2) {
return t1, nil
}
return interfaceType, nil
}
func (n arrayNode) Type(table typesTable) (Type, error) {
for _, node := range n.nodes {
_, err := node.Type(table)
if err != nil {
return nil, err
}
}
return arrayType, nil
}
func (n mapNode) Type(table typesTable) (Type, error) {
for _, node := range n.pairs {
_, err := node.Type(table)
if err != nil {
return nil, err
}
}
return mapType, nil
}
func (n pairNode) Type(table typesTable) (Type, error) {
var err error
_, err = n.key.Type(table)
if err != nil {
return nil, err
}
_, err = n.value.Type(table)
if err != nil {
return nil, err
}
return nil, nil
}
// helper funcs for reflect
func isComparable(l Type, r Type) bool {
l = dereference(l)
r = dereference(r)
if l == nil || r == nil {
return true // It is possible to compare with nil.
}
if isNumberType(l) && isNumberType(r) {
return true
} else if l.Kind() == reflect.Interface {
return true
} else if r.Kind() == reflect.Interface {
return true
} else if l == r {
return true
}
return false
}
func isInterfaceType(t Type) bool {
t = dereference(t)
if t != nil {
switch t.Kind() {
case reflect.Interface:
return true
}
}
return false
}
func isNumberType(t Type) bool {
t = dereference(t)
if t != nil {
switch t.Kind() {
case reflect.Float32, reflect.Float64:
fallthrough
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
fallthrough
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return true
}
}
return false
}
func isBoolType(t Type) bool {
t = dereference(t)
if t != nil {
switch t.Kind() {
case reflect.Bool:
return true
}
}
return false
}
func isStringType(t Type) bool {
t = dereference(t)
if t != nil {
switch t.Kind() {
case reflect.String:
return true
}
}
return false
}
func isArrayType(t Type) bool {
t = dereference(t)
if t != nil {
switch t.Kind() {
case reflect.Slice, reflect.Array:
return true
}
}
return false
}
func isMapType(t Type) bool {
t = dereference(t)
if t != nil {
switch t.Kind() {
case reflect.Map:
return true
}
}
return false
}
func isStructType(t Type) bool {
t = dereference(t)
if t != nil {
switch t.Kind() {
case reflect.Struct:
return true
}
}
return false
}
func fieldType(ntype Type, name string) (Type, bool) {
ntype = dereference(ntype)
if ntype != nil {
switch ntype.Kind() {
case reflect.Interface:
return interfaceType, true
case reflect.Struct:
// First check all struct's fields.
for i := 0; i < ntype.NumField(); i++ {
f := ntype.Field(i)
if !f.Anonymous && f.Name == name {
return f.Type, true
}
}
// Second check fields of embedded structs.
for i := 0; i < ntype.NumField(); i++ {
f := ntype.Field(i)
if f.Anonymous {
if t, ok := fieldType(f.Type, name); ok {
return t, true
}
}
}
case reflect.Map:
return ntype.Elem(), true
}
}
return nil, false
}
func methodType(ntype Type, name string) (Type, bool) {
ntype = dereference(ntype)
if ntype != nil {
switch ntype.Kind() {
case reflect.Interface:
return interfaceType, true
case reflect.Struct:
// First check all struct's methods.
for i := 0; i < ntype.NumMethod(); i++ {
m := ntype.Method(i)
if m.Name == name {
return m.Type, true
}
}
// Second check all struct's fields.
for i := 0; i < ntype.NumField(); i++ {
f := ntype.Field(i)
if !f.Anonymous && f.Name == name {
return f.Type, true
}
}
// Third check fields of embedded structs.
for i := 0; i < ntype.NumField(); i++ {
f := ntype.Field(i)
if f.Anonymous {
if t, ok := methodType(f.Type, name); ok {
return t, true
}
}
}
case reflect.Map:
return ntype.Elem(), true
}
}
return nil, false
}
func indexType(ntype Type) (Type, bool) {
ntype = dereference(ntype)
if ntype == nil {
return nil, false
}
switch ntype.Kind() {
case reflect.Interface:
return interfaceType, true
case reflect.Map, reflect.Array, reflect.Slice:
return ntype.Elem(), true
}
return nil, false
}
func funcType(ntype Type) (Type, bool) {
ntype = dereference(ntype)
if ntype == nil {
return nil, false
}
switch ntype.Kind() {
case reflect.Interface:
return interfaceType, true
case reflect.Func:
if ntype.NumOut() > 0 {
return ntype.Out(0), true
}
return nilType, true
}
return nil, false
}
func dereference(ntype Type) Type {
if ntype == nil {
return nil
}
if ntype.Kind() == reflect.Ptr {
ntype = dereference(ntype.Elem())
}
return ntype
}
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