Misleading error message "'{}' and 'number' have no overlap"

🔎 Search Terms

empty object type, unintentional comparison

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about object types and structural typing

⏯ Playground Link

https://www.typescriptlang.org/play/?noUncheckedIndexedAccess=true&target=99&ts=5.8.0-dev.20241124#code/JYMwBAFA3gvmC8iwAYCUZZA

💻 Code

if ({} === 0) {}

🙁 Actual behavior

TS 2367: "This comparison appears to be unintentional because the types '{}' and 'number' have no overlap."

🙂 Expected behavior

TS 2367: "This comparison appears to be unintentional because the types 'object' and 'number' have no overlap."

Additional information about the issue

the type {} and number do have overlap; number is a subset of {}.

declare const n: number;
// allowed!
const emptyObjectType: {} = n;

TS is correct to report an error, but it should give a technically correct reason for the error.

Analogous (very contrived) examples can be made for similar coincidentally-including-primitive types, like

// This comparison appears to be unintentional because the types '{ toFixed(): string; toPrecision(): string; }' and 'number' have no overlap.
if ({ toFixed(): string { return "" }; toPrecision(): string { return "" }} === 0) {}

// yet this is allowed
const numbery: { toFixed(): string; toPrecision(): string; } = 0;

Stems from discord discussion beginning here: https://discord.com/channels/508357248330760243/508357638677856287/1310419206260654081

Closely related to discussion regarding https://github.com/microsoft/TypeScript/issues/60582

まず、リンクされた TypeScript Playground の再現コードを実行し、診断 TS2367 を追跡します。報告された '{}' と 'number' という文言を、期待される 'object' と 'number' という文言と比較し、次に、示されている比較のカバレッジを追加または更新して、関連する例でも診断が正しいままであることを確認します。