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consteval.go
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456 lines (400 loc) · 9.14 KB
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package parser
import (
"fmt"
"math"
"strconv"
"strings"
)
// Evaluate evaluates a constant expression to a concrete value.
// Returns int64 for integer expressions, float64 for float, string for string, bool for bool.
func Evaluate(
expr ConstExpr,
) (any, error) {
switch e := expr.(type) {
case *IntegerLiteral:
return parseIntString(e.Value)
case *FloatLiteral:
return parseFloatString(e.Value)
case *StringLiteralExpr:
return e.Value, nil
case *CharLiteralExpr:
if len(e.Value) == 0 {
return int64(0), nil
}
// The lexer already resolves escape sequences, so e.Value
// contains the actual character byte. Use it directly.
return int64(e.Value[0]), nil
case *BoolLiteral:
return e.Value, nil
case *NullLiteral:
return nil, nil
case *UnaryExpr:
return evaluateUnary(e)
case *BinaryExpr:
return evaluateBinaryLazy(e)
case *TernaryExpr:
return evaluateTernary(e)
case *IdentExpr:
return nil, fmt.Errorf(
"%s: cannot evaluate identifier %q without symbol table",
e.TokenPos, e.Name,
)
default:
return nil, fmt.Errorf("unsupported expression type %T", expr)
}
}
func evaluateUnary(
e *UnaryExpr,
) (any, error) {
val, err := Evaluate(e.Operand)
if err != nil {
return nil, err
}
switch e.Op {
case TokenMinus:
switch v := val.(type) {
case int64:
return -v, nil
case float64:
return -v, nil
default:
return nil, fmt.Errorf("%s: unary minus on non-numeric type %T", e.TokenPos, val)
}
case TokenPlus:
switch v := val.(type) {
case int64:
return v, nil
case float64:
return v, nil
default:
return nil, fmt.Errorf("%s: unary plus on non-numeric type %T", e.TokenPos, val)
}
case TokenTilde:
v, ok := val.(int64)
if !ok {
return nil, fmt.Errorf("%s: bitwise NOT on non-integer type %T", e.TokenPos, val)
}
return ^v, nil
case TokenBang:
b, err := toBool(val)
if err != nil {
return nil, fmt.Errorf("%s: logical NOT: %w", e.TokenPos, err)
}
return !b, nil
default:
return nil, fmt.Errorf("%s: unsupported unary operator %s", e.TokenPos, e.Op)
}
}
// evaluateBinaryLazy handles short-circuit evaluation for && and ||,
// then delegates to evaluateBinary for all other operators.
func evaluateBinaryLazy(
e *BinaryExpr,
) (any, error) {
switch e.Op {
case TokenAmpAmp:
left, err := Evaluate(e.Left)
if err != nil {
return nil, err
}
lb, err := toBool(left)
if err != nil {
return nil, fmt.Errorf("%s: logical AND: %w", e.TokenPos, err)
}
if !lb {
return false, nil
}
right, err := Evaluate(e.Right)
if err != nil {
return nil, err
}
rb, err := toBool(right)
if err != nil {
return nil, fmt.Errorf("%s: logical AND: %w", e.TokenPos, err)
}
return rb, nil
case TokenPipePipe:
left, err := Evaluate(e.Left)
if err != nil {
return nil, err
}
lb, err := toBool(left)
if err != nil {
return nil, fmt.Errorf("%s: logical OR: %w", e.TokenPos, err)
}
if lb {
return true, nil
}
right, err := Evaluate(e.Right)
if err != nil {
return nil, err
}
rb, err := toBool(right)
if err != nil {
return nil, fmt.Errorf("%s: logical OR: %w", e.TokenPos, err)
}
return rb, nil
default:
return evaluateBinary(e)
}
}
func evaluateBinary(
e *BinaryExpr,
) (any, error) {
left, err := Evaluate(e.Left)
if err != nil {
return nil, err
}
right, err := Evaluate(e.Right)
if err != nil {
return nil, err
}
// Promote to float if either is float.
leftInt, leftIsInt := left.(int64)
rightInt, rightIsInt := right.(int64)
leftFloat, leftIsFloat := left.(float64)
rightFloat, rightIsFloat := right.(float64)
bothInt := leftIsInt && rightIsInt
eitherFloat := leftIsFloat || rightIsFloat
if leftIsInt && rightIsFloat {
leftFloat = float64(leftInt)
eitherFloat = true
}
if leftIsFloat && rightIsInt {
rightFloat = float64(rightInt)
eitherFloat = true
}
if leftIsFloat && rightIsFloat {
eitherFloat = true
}
switch e.Op {
case TokenPlus:
if bothInt {
return leftInt + rightInt, nil
}
if eitherFloat {
return leftFloat + rightFloat, nil
}
// String concatenation.
ls, lok := left.(string)
rs, rok := right.(string)
if lok && rok {
return ls + rs, nil
}
case TokenMinus:
if bothInt {
return leftInt - rightInt, nil
}
if eitherFloat {
return leftFloat - rightFloat, nil
}
case TokenStar:
if bothInt {
return leftInt * rightInt, nil
}
if eitherFloat {
return leftFloat * rightFloat, nil
}
case TokenSlash:
if bothInt {
if rightInt == 0 {
return nil, fmt.Errorf("%s: division by zero", e.TokenPos)
}
return leftInt / rightInt, nil
}
if eitherFloat {
return leftFloat / rightFloat, nil
}
case TokenPercent:
if bothInt {
if rightInt == 0 {
return nil, fmt.Errorf("%s: modulo by zero", e.TokenPos)
}
return leftInt % rightInt, nil
}
if eitherFloat {
return math.Mod(leftFloat, rightFloat), nil
}
case TokenAmp:
if bothInt {
return leftInt & rightInt, nil
}
case TokenPipe:
if bothInt {
return leftInt | rightInt, nil
}
case TokenCaret:
if bothInt {
return leftInt ^ rightInt, nil
}
case TokenLShift:
if bothInt {
if rightInt < 0 || rightInt > 63 {
return int64(0), nil
}
return leftInt << uint(rightInt), nil
}
case TokenRShift:
if bothInt {
if rightInt < 0 || rightInt > 63 {
return int64(0), nil
}
return leftInt >> uint(rightInt), nil
}
case TokenEqEq:
return evalEquality(left, right, leftFloat, rightFloat, bothInt, eitherFloat, leftInt, rightInt), nil
case TokenBangEq:
return !evalEquality(left, right, leftFloat, rightFloat, bothInt, eitherFloat, leftInt, rightInt), nil
case TokenLAngle:
if bothInt {
return leftInt < rightInt, nil
}
if eitherFloat {
return leftFloat < rightFloat, nil
}
case TokenRAngle:
if bothInt {
return leftInt > rightInt, nil
}
if eitherFloat {
return leftFloat > rightFloat, nil
}
case TokenLessEq:
if bothInt {
return leftInt <= rightInt, nil
}
if eitherFloat {
return leftFloat <= rightFloat, nil
}
case TokenGreaterEq:
if bothInt {
return leftInt >= rightInt, nil
}
if eitherFloat {
return leftFloat >= rightFloat, nil
}
}
return nil, fmt.Errorf(
"%s: unsupported binary operation %s on types %T and %T",
e.TokenPos, e.Op, left, right,
)
}
func evalEquality(
left any,
right any,
leftFloat float64,
rightFloat float64,
bothInt bool,
eitherFloat bool,
leftInt int64,
rightInt int64,
) bool {
if bothInt {
return leftInt == rightInt
}
if eitherFloat {
return leftFloat == rightFloat
}
return left == right
}
func evaluateTernary(
e *TernaryExpr,
) (any, error) {
cond, err := Evaluate(e.Cond)
if err != nil {
return nil, err
}
b, err := toBool(cond)
if err != nil {
return nil, fmt.Errorf("%s: ternary condition: %w", e.TokenPos, err)
}
if b {
return Evaluate(e.Then)
}
return Evaluate(e.Else)
}
func toBool(
v any,
) (bool, error) {
switch val := v.(type) {
case bool:
return val, nil
case int64:
return val != 0, nil
case float64:
return val != 0, nil
default:
return false, fmt.Errorf("cannot convert %T to bool", v)
}
}
// aidlIntSuffixes lists AIDL typed integer suffixes to strip during parsing.
// These include unsigned (u8, u16, u32, u64) and signed (i8, i16, i32, i64)
// suffixes. Longer suffixes are listed first so they match before shorter
// ones.
var aidlIntSuffixes = []string{
"u64", "u32", "u16", "u8",
"i64", "i32", "i16", "i8",
}
// parseIntString parses an integer literal string (decimal, hex, octal, binary)
// with optional L/l or AIDL typed integer suffixes (u8, u32, i64, etc.).
func parseIntString(
s string,
) (int64, error) {
// Strip AIDL typed integer suffixes (e.g. 42u8, 0xFFi32).
for _, suffix := range aidlIntSuffixes {
if strings.HasSuffix(s, suffix) {
s = s[:len(s)-len(suffix)]
break
}
}
// Strip long suffix (at most one 'L' or 'l').
s = strings.TrimSuffix(strings.TrimSuffix(s, "L"), "l")
if s == "" {
return 0, fmt.Errorf("empty integer literal")
}
// Hex.
if strings.HasPrefix(s, "0x") || strings.HasPrefix(s, "0X") {
v, err := strconv.ParseInt(s[2:], 16, 64)
if err != nil {
// Try unsigned parse for large hex values.
uv, uerr := strconv.ParseUint(s[2:], 16, 64)
if uerr != nil {
return 0, fmt.Errorf("invalid hex literal %q: %w", s, err)
}
return int64(uv), nil
}
return v, nil
}
// Binary.
if strings.HasPrefix(s, "0b") || strings.HasPrefix(s, "0B") {
v, err := strconv.ParseInt(s[2:], 2, 64)
if err != nil {
return 0, fmt.Errorf("invalid binary literal %q: %w", s, err)
}
return v, nil
}
// Octal: starts with 0 and has more digits.
if len(s) > 1 && s[0] == '0' && s[1] >= '0' && s[1] <= '7' {
v, err := strconv.ParseInt(s[1:], 8, 64)
if err != nil {
return 0, fmt.Errorf("invalid octal literal %q: %w", s, err)
}
return v, nil
}
// Decimal.
v, err := strconv.ParseInt(s, 10, 64)
if err != nil {
return 0, fmt.Errorf("invalid integer literal %q: %w", s, err)
}
return v, nil
}
func parseFloatString(
s string,
) (float64, error) {
// Strip float/double suffix.
s = strings.TrimRight(s, "fFdD")
v, err := strconv.ParseFloat(s, 64)
if err != nil {
return 0, fmt.Errorf("invalid float literal %q: %w", s, err)
}
return v, nil
}