`any` appears to shortcircut structural type checking

TypeScript Version: 3.5.0-dev.20190507

Search Terms:
any, unsound, extends, never

Code

// I detect if F is `any` by checking if F extends `never`.
// (F extends never ? true : false) produces `true|false` for `F = any`
// and `false` or `never` for everything else.
type Decider<F> = {
	prop: (F extends never ? true : false) extends false ? "isNotAny" : "isAny";
};

let foo!: Decider<string>;
let bar: Decider<any> = foo;

let fooProp: "isNotAny" = foo.prop;
let barProp: "isAny" = bar.prop;

Expected behavior:
Either bar.prop should have the type "isAny"|"isNotAny" or foo should not be assignable to bar.

Actual behavior:
foo is assignable to bar and bar.prop has the type "isAny" which is incompatible with foo.prop's "isNotAny".

Playground Link: link

Start by reproducing the TypeScript 3.5.0-dev.20190507 example in the linked Playground and verify the reported assignability and inferred property types. Trace the type-checker behavior for conditional types involving any, never, and structural assignability; done means the example follows one of the stated expected behaviors without breaking the corresponding type-system rules.