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util.go
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util.go
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package eval
import (
"reflect"
"regexp"
"strconv"
"strings"
"go/ast"
"go/token"
)
// Equivalent of reflect.New, but unwraps internal Types into their original reflect.Type
func hackedNew(t reflect.Type) reflect.Value {
return reflect.New(unhackType(t))
}
// Get the underlying reflect.Type a hacked type
func unhackType(t reflect.Type) reflect.Type {
switch tt := t.(type) {
case Rune:
return tt.Type
case Byte:
return tt.Type
default:
return t
}
}
// Determine if type from is assignable to type to. From and To must not be ConstTypes
func typeAssignableTo(from, to reflect.Type) bool {
return from.AssignableTo(unhackType(to))
}
// exprAssignableTo(CheckExpr(expr), t), but errors are accumulated and a
// bool value is returned indicating if the expr is assignable to t.
// The bool value will be false if and only if the conversion check
// was reached and failed.
func checkExprAssignableTo(expr ast.Expr, t reflect.Type, env Env) (Expr, bool, []error) {
var errs []error
aexpr, moreErrs := CheckExpr(expr, env)
if moreErrs != nil {
errs = append(errs, moreErrs...)
} else if _, err := expectSingleType(aexpr); err != nil {
errs = append(errs, err)
}
if errs != nil {
return aexpr, true, errs
}
ok, convErrs := exprAssignableTo(aexpr, t)
if convErrs != nil {
errs = append(errs, convErrs...)
}
return aexpr, ok, errs
}
// Determine if the result of from expr is assignable to type to. to must be a vanilla reflect.Type.
// from must have a KnownType() of length 1. Const types that raise overflow and truncation
// errors will still return true, but the errors will be reflected in the []error slice.
func exprAssignableTo(from Expr, to reflect.Type) (bool, []error) {
if len(from.KnownType()) != 1 {
panic("go-eval: assignableTo called with from.KnownType() != 1")
}
fromType := from.KnownType()[0]
// Check that consts can be converted
if c, ok := fromType.(ConstType); ok && from.IsConst() {
// If cv is a valid value, then the types are assignable even if
// other conversion errors, such as overflows, are present.
cv, errs := promoteConstToTyped(c, constValue(from.Const()), to, from)
return reflect.Value(cv).IsValid(), errs
}
return typeAssignableTo(fromType, to), nil
}
func expectSingleType(expr Expr) (reflect.Type, error) {
types := expr.KnownType()
if len(types) == 0 {
return nil, ErrMissingValue{expr}
} else if multivalueOk(expr) {
return types[0], nil
} else if len(types) != 1 {
return nil, ErrMultiInSingleContext{expr}
} else {
return types[0], nil
}
}
// Is op a boolean operator that produces a const bool type.
// Notably absent are LAND(&&) and LOR(||), which result
// in a value of the same type as their operands.
func isBooleanOp(op token.Token) bool {
switch op {
case token.EQL, token.NEQ, token.LEQ, token.GEQ, token.LSS, token.GTR:
return true
default:
return false
}
}
func isOpDefinedOn(op token.Token, t reflect.Type) bool {
if _, ok := t.(ConstNilType); ok {
return false
}
switch t.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
switch op {
case token.ADD, token.SUB, token.MUL, token.QUO,
token.REM, token.AND, token.OR, token.XOR, token.AND_NOT,
token.EQL, token.NEQ,
token.LEQ, token.GEQ, token.LSS, token.GTR:
return true
}
case reflect.Float32, reflect.Float64:
switch op {
case token.ADD, token.SUB, token.MUL, token.QUO,
token.EQL, token.NEQ,
token.LEQ, token.GEQ, token.LSS, token.GTR:
return true
}
case reflect.Complex64, reflect.Complex128:
switch op {
case token.ADD, token.SUB, token.MUL, token.QUO,
token.EQL, token.NEQ:
return true
}
case reflect.Bool:
switch op {
case token.LAND, token.LOR, token.EQL, token.NEQ:
return true
}
case reflect.String:
switch op {
case token.ADD, token.EQL, token.NEQ, token.LEQ, token.GEQ, token.LSS, token.GTR:
return true
}
// This is slighly misleading. slices, funcs and maps are only
// comparable if their paired operand is nil
case reflect.Ptr, reflect.Array, reflect.Interface, reflect.Struct,
reflect.Slice, reflect.Map, reflect.Chan:
return op == token.EQL || op == token.NEQ
}
return false
}
func isUnaryOpDefinedOn(op token.Token, t reflect.Type) bool {
if _, ok := t.(ConstNilType); ok {
return false
}
switch t.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
switch op {
case token.ADD, token.SUB, token.XOR:
return true
}
case reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
switch op {
case token.ADD, token.SUB:
return true
}
case reflect.Bool:
switch op {
case token.NOT:
return true
}
}
return false
}
// FIXME: should also match and handle just a line and no column
var parseError = regexp.MustCompile(`^([0-9]+):([0-9]+): `)
// FormatErrorPos formats source to show the position that a (parse)
// error occurs. When this works, it returns a slice of one or two
// strings: the source line with the error and if it can find a column
// position under that, a line indicating the position where the error
// occurred.
//
// For example, if we have:
// source := `split(os.Args ", )")`
// errmsg := "1:15: expected ')'"
// then PrintErrPos(source, errmsg) returns:
// {
// `split(os.Args ", )")`,
// `-------------^`
// }
//
// If something is wrong parsing the error message or matching it with
// the source, an empty slice is returned.
func FormatErrorPos(source, errmsg string) (cursored [] string) {
matches := parseError.FindStringSubmatch(errmsg)
if len(matches) == 3 {
var err error
var line, column int
if line, err = strconv.Atoi(matches[1]); err != nil {
return cursored
}
if column, err = strconv.Atoi(matches[2]); err != nil {
return cursored
}
sourceLines := strings.Split(source, "\n")
if line > len(sourceLines) {
return cursored
}
errLine := sourceLines[line-1]
cursored = append(cursored, errLine)
if column-1 > len(errLine) || column < 1 {
return cursored
} else if column == 1 {
cursored = append(cursored, "^")
} else {
cursored = append(cursored, strings.Repeat("-", column-1) + "^")
}
}
return cursored
}
// Walk the ast of expressions like (((x))) and return the inner *ParenExpr.
// Returns input Expr if it is not a *ParenExpr
func skipSuperfluousParens(expr Expr) Expr {
if p, ok := expr.(*ParenExpr); ok {
// Remove useless parens from (((x))) expressions
for tmp, ok := p.X.(*ParenExpr); ok; tmp, ok = p.X.(*ParenExpr) {
p = tmp
}
// Remove parens from all expressions where order of evaluation is irrelevant
switch p.X.(type) {
case *BinaryExpr:
return p
default:
return p.X
}
}
return expr
}
// Returns the float type that is half the width of the input complex type
func comprisingFloatType(complexType reflect.Type) reflect.Type {
if complexType == c128 {
return f64
} else {
return f32
}
}
// Evals an expression with a known result type. If the node is an
// untyped constant, it is converted to type t. This function assumes
// the input is successfully type checked, and therefore is undefined
// incorrectly typed inputs.
func evalTypedExpr(expr Expr, t knownType, env Env) (xs []reflect.Value, err error) {
if expr.IsConst() {
x := expr.Const()
if ct, ok := expr.KnownType()[0].(ConstType); ok {
cx, _ := promoteConstToTyped(ct, constValue(x), t[0], expr)
xs = []reflect.Value{reflect.Value(cx)}
} else {
xs = []reflect.Value{x}
}
} else {
xs, err = EvalExpr(expr, env)
}
return xs, err
}
// Type check an integral node. Returns the type checked node, the
// integer value if constant, ok if the node was indeed integral,
// and checkErrs which occur during the type check. It is possible
// that checkErrs will be non-nil yet ok is still true. In this case
// the errors are non-fatal, such as integer truncation.
func checkInteger(expr ast.Expr, env Env) (aexpr Expr, i int, ok bool, checkErrs []error) {
aexpr, checkErrs = CheckExpr(expr, env)
if checkErrs != nil && !aexpr.IsConst() {
return aexpr, 0, false, checkErrs
}
t, err := expectSingleType(aexpr)
if err != nil {
return aexpr, 0, false, append(checkErrs, err)
}
var ii int64
if ct, ok := t.(ConstType); ok {
c, moreErrs := promoteConstToTyped(ct, constValue(aexpr.Const()), intType, aexpr)
if moreErrs != nil {
checkErrs = append(checkErrs, moreErrs...)
}
v := reflect.Value(c)
if v.IsValid() {
ii = v.Int()
} else {
return aexpr, 0, false, checkErrs
}
} else {
switch t.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
if aexpr.IsConst() {
ii = aexpr.Const().Int()
}
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
if aexpr.IsConst() {
ii = int64(aexpr.Const().Uint())
}
default:
return aexpr, 0, false, checkErrs
}
}
return aexpr, int(ii), true, checkErrs
}
// Eval a node and cast it to an int. expr must be a *ConstNumber or integral type
func evalInteger(expr Expr, env Env) (int, error) {
if expr.IsConst() {
x := expr.Const()
if ct, ok := expr.KnownType()[0].(ConstType); ok {
cx, _ := promoteConstToTyped(ct, constValue(x), intType, expr)
return int(reflect.Value(cx).Int()), nil
} else {
panic(dytc("const bool or string evaluated as int"))
}
} else {
xs, err := EvalExpr(expr, env);
if err != nil {
return 0, err
}
x := xs[0]
switch x.Type().Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return int(x.Int()), nil
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return int(x.Uint()), nil
default:
panic(dytc("non-integral type evaluated as int"))
}
}
}
func checkArrayIndex(expr ast.Expr, env Env) (aexpr Expr, i int, ok bool, checkErrs []error) {
aexpr, checkErrs = CheckExpr(expr, env)
if !aexpr.IsConst() {
return aexpr, 0, false, checkErrs
}
t := aexpr.KnownType()[0]
var ii int64
if ct, ok := t.(ConstType); ok {
c, moreErrs := promoteConstToTyped(ct, constValue(aexpr.Const()), intType, aexpr)
if moreErrs != nil {
checkErrs = append(checkErrs, moreErrs...)
}
v := reflect.Value(c)
if v.IsValid() {
ii = v.Int()
} else {
return aexpr, 0, false, checkErrs
}
} else {
switch t.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
ii = aexpr.Const().Int()
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
ii = int64(aexpr.Const().Uint())
default:
return aexpr, 0, false, checkErrs
}
}
// The limit of 2^31-1 is derived from the gc implementation,
// which seems to use this definition whilst type checking.
// The actual definition is the "largest value representable by an int"
return aexpr, int(ii), 0 <= ii && ii <= 0x7fffffff, checkErrs
}
// spec: addressable, that is, either a
// variable,
// pointer indirection,
// or slice indexing operation;
// or a field selector of an addressable struct operand;
// or an array indexing operation of an addressable array.
// As an exception to the addressability requirement, x may also be a (possibly parenthesized) composite literal
func isAddressable(expr Expr) bool {
expr = skipSuperfluousParens(expr)
switch n := expr.(type) {
case *Ident:
return n.source == envVar
case *StarExpr:
return true
case *IndexExpr:
x := n.X
t := x.KnownType()[0]
switch t.Kind() {
case reflect.Slice:
return true
case reflect.Array:
return isAddressable(x)
case reflect.Ptr:
return true
}
case *SelectorExpr:
if n.pkgName != "" {
return isAddressable(n.Sel)
}
x := n.X
t := x.KnownType()[0]
switch t.Kind() {
case reflect.Struct:
return isAddressable(x)
case reflect.Ptr:
return true
}
}
return false
}
func isAddressableOrCompositeLit(expr Expr) bool {
expr = skipSuperfluousParens(expr)
if _, ok := expr.(*CompositeLit); ok {
return true
} else {
return isAddressable(expr)
}
}
func isStaticTypeComparable(t reflect.Type) bool {
switch t.Kind() {
case reflect.Slice, reflect.Map, reflect.Func:
return false
case reflect.Struct:
return isStructComparable(t)
default:
return true
}
}
func isStructComparable(structT reflect.Type) bool {
_, ok := nonComparableField(structT)
return !ok
}
func nonComparableField(structT reflect.Type) (reflect.StructField, bool) {
numField := structT.NumField()
for i := 0; i < numField; i += 1 {
field := structT.Field(i)
if !isStaticTypeComparable(field.Type) {
return field, true
}
}
return reflect.StructField{}, false
}
func attemptBinaryOpConversion(to reflect.Type) bool {
switch to.Kind() {
case reflect.Invalid, reflect.Array, reflect.Chan, reflect.Func, reflect.Interface,
reflect.Map, reflect.Ptr, reflect.Slice, reflect.Struct:
return false
}
return true
}
func comparableToNilOnly(x reflect.Type) bool {
switch x.Kind() {
case reflect.Func, reflect.Map, reflect.Slice:
return true
}
return false
}
func isNillable(t reflect.Type) bool {
switch t.Kind() {
case reflect.Chan, reflect.Func, reflect.Interface,
reflect.Map, reflect.Ptr, reflect.Slice:
return true
}
return false
}
func isUnsignedInt(t reflect.Type) bool {
// All const numeric types can be "truncated" to an unsigned int, and
// therefore for type checking purposes are valid
if ct, ok := t.(ConstType); ok {
return ct.IsNumeric()
}
switch t.Kind() {
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return true
}
return false
}
func isShiftable(t reflect.Type) bool {
switch t.(type) {
case ConstNilType, ConstBoolType, ConstComplexType, ConstStringType:
return false
case ConstIntType, ConstFloatType, ConstRuneType:
return true
default:
switch t.Kind() {
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr,
reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return true
default:
return false
}
}
}
func isBlankIdentifier(blank ast.Expr) bool {
switch x := blank.(type) {
case *ast.ParenExpr:
return isBlankIdentifier(x.X)
case *ast.Ident:
return x.Name == "_"
}
return false
}
func multivalueOk(expr Expr) bool {
switch e := skipSuperfluousParens(expr).(type) {
case *TypeAssertExpr:
return true
case *IndexExpr:
return e.X.KnownType()[0].Kind() == reflect.Map
case *UnaryExpr:
return e.Op == token.ARROW
default:
return false
}
}
func inTopEnv(name string, env Env) bool {
if v := env.Var(name); v.IsValid() {
return true
} else if v := env.Const(name); v.IsValid() {
return true
} else if v := env.Func(name); v.IsValid() {
return true
} else {
return false
}
}
func equal(x, y reflect.Value) (bool, error) {
if t := areDynamicTypesComparable(x, y); t != nil {
return false, PanicUncomparableType{t}
} else {
return x.Interface() == y.Interface(), nil
}
}