oxc-project/oxc · error · OxcDiagnostic

Do not use 'new' for side effects.

Error message

Do not use 'new' for side effects.

What it means

Lint diagnostic from eslint/no-new: a NewExpression statement's result is discarded (not assigned or compared). Constructing for side effects suggests the type is being abused; the allocation is wasted and the convention is considered an error-prone pattern.

Source

Thrown at crates/oxc_linter/src/rules/eslint/no_new.rs:10

use oxc_ast::AstKind;
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_semantic::AstNode;
use oxc_span::{GetSpan, Span};

use crate::{ast_util::outermost_paren_parent, context::LintContext, rule::Rule};

fn no_new_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Do not use 'new' for side effects.")
        .with_help("Assign the result of 'new' to a variable or compare it to a reference.")
        .with_label(span)
}

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

declare_oxc_lint!(
    /// ### What it does
    ///
    /// Disallow new operators outside of assignments or comparisons.
    ///
    /// ### Why is this bad?
    ///
    /// Calling new without assigning or comparing it the reference is thrown away and in many
    /// cases the constructor can be replaced with a function.
    ///
    /// ### Examples

View on GitHub (pinned to e1e7af627c)

Solutions

1. Assign the constructed instance to a variable
2. Compare the result to a reference if existence is what matters
3. Move the side effect into an explicit method call on an existing object

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/eslint/no_new.rs:10 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/452cb51677be5902. Report an issue: GitHub.