Debug Failure when emitting declaration for unresolved type constraints

[HerringtonDarkholme]

TypeScript Version: nightly, --declaration

Code

// @declaration
type A<T extends Unknown> = {}

Expected behavior:
Report Cannot find name 'Unknown'

Actual behavior:

Debug Failure. This is unknown parent for type parameter.

N.B. the actual bug is much more subtle. I encounter this when a type alias is bound by a type imported from a library. The actual bug is a compiler crash.

[HerringtonDarkholme]

The actual reproduction is here. https://github.com/HerringtonDarkholme/av-ts/tree/ts-crash.
git clone and npm install and npm run compile should reproduce.
The last commit introduces compiler crashes.

Error is Cannot read property 'flags' of undefined at getTargetSymbol.

[HerringtonDarkholme]

Together with #12291, all bugs are related to declaration emitting. Maybe we can just skip declaration emitting if there is error in compiling? Since code failed to compile will hardly produce valid declaration.