Interface ConfigValueFunc

interface ConfigValueFunc {
    (envVarName): undefined | string;
    (envVarName, defaultOrRequired): string;
    (envVarName, validator): undefined | string;
    (envVarName, required, validator): string;
    (envVarName, defaultValue, validator): string;
    (envVarName, t): undefined | string;
    (envVarName, t, defaultOrRequired): string;
    (envVarName, t, validator): undefined | string;
    (envVarName, t, required, validator): string;
    (envVarName, t, defaultValue, validator): string;
    (envVarName, t): undefined | number | `::ERROR::${string}`;
    (envVarName, t, defaultOrRequired): number | `::ERROR::${string}`;
    (envVarName, t, validator): number | `::ERROR::${string}`;
    (envVarName, t, required, validator): number | `::ERROR::${string}`;
    (envVarName, t, defaultValue, validator): number | `::ERROR::${string}`;
    (envVarName, t): undefined | boolean | `::ERROR::${string}`;
    (envVarName, t, defaultOrRequired): boolean | `::ERROR::${string}`;
    (envVarName, t, validator): undefined | boolean | `::ERROR::${string}`;
    (envVarName, t, required, validator): boolean | `::ERROR::${string}`;
    (envVarName, t, defaultValue, validator): boolean | `::ERROR::${string}`;
    <T>(envVarName, t): undefined | `::ERROR::${string}` | T;
    <T>(envVarName, t, defaultOrRequired): `::ERROR::${string}` | T;
    <T>(envVarName, t, validator): undefined | `::ERROR::${string}` | T;
    <T>(envVarName, t, required, validator): `::ERROR::${string}` | T;
    <T>(envVarName, t, defaultValue, validator): `::ERROR::${string}` | T;
}