function that takes generic with no constraint can call function with type constraint with invalid type

[DetachHead]

Bug Report

🔎 Search Terms

Generic no constraint call function with no constraint

🕗 Version & Regression Information

4.3.0-dev-20210504

⏯ Playground Link

https://www.typescriptlang.org/play?ts=4.3.0-dev.20210506#code/GYVwdgxgLglg9mABAIwIYCcA8AVRBTADyjzABMBnRAbwG0BrPATwC5Fyp0YwBzAXVdRhGAXwB8ACgBuqADYg8rbAEpqAKEQbE0uXgB0AC1TkA8gHcwABXRwADnnRRG4gOTA4cZ0tXDVq0JFgERDc4HAlteUUlKnVNNCxscNl5FQB6VLA4fHRrdAAafEkSRCh9OBBufURcUjg8cjBnKEQAW1QoCCrSvEQIBHZ0VC4ob1948XBSPGAuPFI01L6cvGgZRmzc8lZJ6dnSRBhKTOajchhuMFRkGR6oLOw-dwmyXbA5hcyNuHzgoZlKdqIdDgWAtPBAA

💻 Code

function bar<T extends {[key: string]: any}>(value: T) {
    value.hasOwnProperty('foo')
}

function foo<T>(value: T){
    bar<T>(value) //no error, even though T doesn't match the constraint
}

bar(undefined) //correctly errors: undefined is not assignable to T
foo(undefined) //no error, fails at runtime

🙁 Actual behavior

No compile error when calling bar with a type that doesn't match the bounds of T

🙂 Expected behavior

Compile error

[MartinJohns]

This sounds somewhat like #31006.

[RyanCavanaugh]

This would be a pretty noisy breaking change for likely not much upside, but we can discuss

[DetachHead]

this seems to be fixed as of 4.8

function bar<T extends {[key: string]: any}>(value: T) {
    value.hasOwnProperty('foo')
}

function foo<T>(value: T){
    bar<T>(value) //error in 4.8
}