Assertion call in optional chain should not narrow variable

TypeScript Version: 4.1.3

Search Terms: assert optional call

Expected behavior:

No narrowing of v.
Maybe an error indicating that assertion calls don't work with optional chaining.

Actual behavior:

Assertion call narrows v. If strictNullChecks is enabled, it works as expected.

Related Issues:

Code

// @strictNullChecks: false
declare const obj: {
  assert?(v: any): asserts v;
}

declare const v: boolean;
obj.assert?.(v);
v; // should not be narrowed to 'true'

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "moduleResolution": 2,
    "target": "ES2017",
    "jsx": "React",
    "module": "ESNext"
  }
}

Playground Link: Provided

Start with the provided Playground Link and reproduce the optional assertion-call example with strictNullChecks disabled, comparing the observed narrowing with the expected behavior. Trace the compiler's control-flow narrowing for optional calls; done means v is not narrowed after obj.assert?.(v), or the unsupported combination is diagnosed.