oxc-project/oxc · error · OxcDiagnostic

Do not use `new Array(singleArgument)`.

Error message

Do not use `new Array(singleArgument)`.

What it means

Raised by unicorn/no-new-array when `new Array(singleArgument)` is used with exactly one argument, because the semantics are ambiguous: a number sets the length, any other value becomes the sole element. The faulting input is the single-argument `new Array()` call at the labeled span.

Source

Thrown at crates/oxc_linter/src/rules/unicorn/no_new_array.rs:17

use oxc_ast::{
    AstKind,
    ast::{Argument, Expression},
};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::{GetSpan, Span};

use crate::{
    AstNode, ast_util,
    context::LintContext,
    fixer::{RuleFix, RuleFixer},
    rule::Rule,
};

fn no_new_array_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Do not use `new Array(singleArgument)`.")
        .with_help(r"It's not clear whether the argument is meant to be the length of the array or the only element. If the argument is the array's length, consider using `Array.from({ length: n })`. If the argument is the only element, use `[element]`.").with_label(span)
}

#[derive(Debug, Default, Clone)]
pub struct NoNewArray;

declare_oxc_lint!(
    /// ### What it does
    ///
    /// Disallow `new Array()`.
    ///
    /// ### Why is this bad?
    ///
    /// When using the `Array` constructor with one argument, it's not clear whether the argument is meant to be the length of the array or the only element.
    ///
    /// ### Examples
    ///
    /// Examples of **incorrect** code for this rule:

View on GitHub (pinned to e1e7af627c)

Solutions

1. If the argument is the length, use `Array.from({ length: n })`
2. If it is the only element, use an array literal `[value]`

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/unicorn/no_new_array.rs:17 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/382fc32a8684cd4f. Report an issue: GitHub.