`Exclude<Exclude<T, null>, undefined>` is not assignable to `Exclude<T, null | undefined>` and vice versa

<!-- 🚨 STOP 🚨 𝗦𝗧𝗢𝗣 🚨 𝑺𝑻𝑶𝑷 🚨 Half of all issues filed here are duplicates, answered in the FAQ, or not appropriate for the bug tracker. Even if you think you've found a *bug*, please read the FAQ first, especially the Common "Bugs" That Aren't Bugs section! Please help us by doing the following steps before logging an issue: * Search: https://github.com/Microsoft/TypeScript/search?type=Issues * Read the FAQ: https://github.com/Microsoft/TypeScript/wiki/FAQ Please fill in the *entire* template below. --> **TypeScript Version:** Nightly <!-- Search terms you tried before logging this (so others can find this issue more easily) --> **Search Terms:** typescript nullness inference **Expected behavior:** They should be assignable to each other. **Actual behavior:** They are not considered assignable to each other. ``` Type 'Exclude<Exclude<T, null>, undefined>' is not assignable to type 'Exclude<T, null | undefined>'. Type 'Exclude<T, null>' is not assignable to type 'Exclude<T, null | undefined>'. Type 'T' is not assignable to type 'Exclude<T, null | undefined>'.(2322) ``` and ``` Type 'Exclude<T, null | undefined>' is not assignable to type 'Exclude<Exclude<T, null>, undefined>'. Type 'T' is not assignable to type 'Exclude<Exclude<T, null>, undefined>'.(2322) ``` <!-- Did you find other bugs that looked similar? --> **Related Issues:** N/A **Code** ```ts export function f<T>(v: Exclude<Exclude<T, null>, undefined>) { const w: Exclude<T, null | undefined> = v; } export function g<T>(v: Exclude<T, null | undefined>) { const w: Exclude<Exclude<T, null>, undefined> = v; } ``` <details><summary><b>Output</b></summary> ```ts export function f(v) { const w = v; } export function g(v) { const w = v; } ``` </details> <details><summary><b>Compiler Options</b></summary> ```json { "compilerOptions": { "noImplicitAny": true, "strictNullChecks": true, "strictFunctionTypes": true, "strictPropertyInitialization": true, "stri…