oxc-project/oxc · error · OxcDiagnostic

Unexpected duplicate `super()`.

Error message

Unexpected duplicate `super()`.

What it means

The duplicate_super variant of constructor-super (crates/oxc_linter/src/rules/eslint/constructor_super.rs:32). It reports a second super() call reachable after an earlier one on the same execution path; the engine itself rejects this with 'Super constructor may only be called once'. The diagnostic carries two labels: the duplicate site ('This path may call super() after it was already called.') and the span of the first call ('`super()` was first called here.').

Source

Thrown at crates/oxc_linter/src/rules/eslint/constructor_super.rs:33

use oxc_semantic::NodeId;
use oxc_span::{GetSpan, Span};

use crate::{AstNode, context::LintContext, rule::Rule};

fn missing_super_all(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Expected to call `super()`.")
        .with_help("Add a `super()` call to the constructor")
        .with_label(span)
}

fn missing_super_some(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Lacked a call of `super()` in some code paths.")
        .with_help("Ensure `super()` is called in all code paths")
        .with_label(span)
}

fn duplicate_super(span: Span, first_super_span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Unexpected duplicate `super()`.")
        .with_help("Remove the duplicate `super()` call")
        .with_labels([
            span.primary_label("This path may call `super()` after it was already called."),
            first_super_span.label("`super()` was first called here."),
        ])
}

#[derive(Clone, Copy)]
struct SuperClassContext {
    span: Span,
    label: &'static str,
}

fn bad_super(span: Span, super_class_context: Option<SuperClassContext>) -> OxcDiagnostic {
    let mut labels = vec![span.primary_label("This `super()` call is invalid here.")];
    if let Some(context) = super_class_context {
        labels.push(context.span.label(context.label));
    }

View on GitHub (pinned to e1e7af627c)

Solutions

1. Delete the later duplicate super() call.
2. Keep exactly one super() as the first statement and pass all required arguments to it.

Example fix

// before
constructor() {
  super();
  if (cond) super();
}

// after
constructor() {
  super();
}

// .oxlintrc.json
{
  "rules": {
    "constructor-super": "error"
  }
}

When it happens

Trigger: super() appearing twice sequentially, or an unconditional super() followed by another reachable super() (e.g. inside an if or loop) in a derived-class constructor.

Common situations: Copy-paste merges of two constructors each containing super(); refactoring that moves super() into a branch while leaving the original call.

Related errors

• Expected to call `super()`.
• Lacked a call of `super()` in some code paths.
• Unexpected `super()` because `super` is not a constructor.
• Redundant super call in constructor
• Expected method{method_name_str} to have this.

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/392cc5d4c96082d6. Report an issue: GitHub.