Define 'tagName' values in Element interfaces to prevent misleading type acceptance.

Bug Report

🔎 Search Terms

• HTML Element Interfaces
• Element tagName
• Element Interfaces
• Incorrect element types accepted

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about Element interfaces

⏯ Playground Link

Playground link with relevant code

💻 Code

// Elements can be assigned to variables of other element types because of interface overlaps being sufficient.
let element: HTMLSpanElement = document.createElement("div");

// If the interfaces included the appropriate 'tagName' property this could be avoided...
let spanElement: HTMLSpanElement & { tagName: "SPAN" } = document.createElement("div") as HTMLDivElement & { tagName: "DIV" };

🙁 Actual behavior

e.g. 'HTMLDivElement' instance can be assigned to variables of type 'HTMLSpanElement'.

🙂 Expected behavior

This should fail the type checking to avoid accidentally assigning elements of an incorrect type.

リンクされた TypeScript Playground の再現例から始め、関連する HTML Element インターフェース、特に HTMLSpanElement と HTMLDivElement の tagName を調べます。HTMLDivElement が HTMLSpanElement として受け入れられなくなり、示されている tagName の交差の挙動が正確に表現されたままであれば完了です。