oxc-project/oxc · error · OxcDiagnostic

This overload can be combined with another overload into one

Error message

This overload can be combined with another overload into one signature taking `{type1} | {type2}`.

What it means

Raised by typescript/unified_signatures when two overloads of a function/method differ only in that one accepts type A and the other type B at the same parameter position, so they can be merged into a single signature accepting `A | B`. At the throw site the redundant overload increases API surface and maintenance cost; report_failure builds the message with the two type names and multi-label span pointing at both overload signatures. unified_signatures_diagnostic is the generic constructor used for all rule findings.

Source

Thrown at crates/oxc_linter/src/rules/typescript/unified_signatures.rs:30

};
use oxc_diagnostics::{LabeledSpan, OxcDiagnostic};
use oxc_macros::declare_oxc_lint;
use oxc_span::{GetSpan, Span};
use rustc_hash::{FxHashMap, FxHashSet};
use schemars::JsonSchema;
use serde::{Deserialize, Serialize};

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

fn unified_signatures_diagnostic<L: Into<LabeledSpan>, T: IntoIterator<Item = L>>(
    message: String,
    labels: T,
) -> OxcDiagnostic {
    OxcDiagnostic::warn(message).with_labels(labels)
}

#[derive(Debug, Default, Clone, Deserialize, Serialize, JsonSchema)]
#[serde(default, rename_all = "camelCase", deny_unknown_fields)]
pub struct UnifiedSignaturesOptions {
    /// Whether to ignore parameter name differences when comparing signatures. If `false`, signatures
    /// will not be considered unifiable if they have parameters in the same position with different
    /// names, even if the parameter types are the same.
    ignore_differently_named_parameters: bool,
    /// Whether to ignore JSDoc differences when comparing signatures. If `false`, signatures will not
    /// be considered unifiable if the closest leading block comments for the signatures are different,
    /// even if the signatures themselves are identical.
    #[serde(rename = "ignoreOverloadsWithDifferentJSDoc")]
    ignore_overloads_with_different_jsdoc: bool,
}

#[derive(Debug, Default, Clone, Deserialize, Serialize)]
pub struct UnifiedSignatures(UnifiedSignaturesOptions);

View on GitHub (pinned to e1e7af627c)

Solutions

1. Combine the two overloads into one signature using a union type for the differing parameter.

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/typescript/unified_signatures.rs:30 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/bd72802e557621f4. Report an issue: GitHub.