typescript/no-non-null-asserted-nullish-coalescing Restriction
What it does
Disallow non-null assertions in the left operand of a nullish coalescing operator.
Why is this bad?
The ?? nullish coalescing runtime operator allows providing a default value when dealing with null or undefined. Using a ! non-null assertion type operator in the left operand of a nullish coalescing operator is redundant, and likely a sign of programmer error or confusion over the two operators.
Example
ts
foo! ?? bar;
let x: string;
x! ?? "";