swc/crates/swc_ecma_parser/tests/tsc/ambientEnumDeclaration1.ts

// In ambient enum declarations, all values specified in enum member declarations must be classified as constant enum expressions.

declare enum E {
    a = 10,
    b = 10 + 1,
    c = b,
    d = (c) + 1,
    e = 10 << 2 * 8,
}