Class method assigned to a variable has incorrect inferred type

[olehmisar]

Bug Report

🔎 Search Terms

class method function assignment variable this bind

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ

⏯ Playground Link

Playground link with relevant code

💻 Code

class User {
    name: string | undefined
    setName(name: string) {
        this.name = name
    }
}

const user = new User()
const setNameFunction = user.setName
setNameFunction('bob')

🙁 Actual behavior

• the type of setNameFunction is inferred to be (name: string) => void
• code compiled successfully
• runtime execution failed: Cannot set properties of undefined (setting 'name')

🙂 Expected behavior

• the type of setNameFunction should be inferred to be (this: User, name: string) => void
• code should not compile because setNameFunction('bob') will fail in runtime

[whzx5byb]

See #7968 and #6739

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.