Non-conformance error due to error in a `typealias`'s aliasee clause

IDE: Visual Studio X/Fire
Version: (develop)
Target (If relevant): OSX
If a type declares conformance to a protocol and has a typealias declaring an alias matching one of the protocol’s associated types, if the typealias has an error, the non-conformance error implies the typealias does not exist.

Expected Behavior:
The non-conformance error should reference the typealias (“did you mean …”, etc.)
Actual Behavior:
see below.

protocol P {
  associatedtype A

struct S: P { // E582 Associated type "A" from protocol "P<A>" was not set
  typealias A = DoesNotExist // E28 Unknown type "DoesNotExist"
  // OR this?:
  // typealias A // E1 assign expected, got closing bracket

Thanks, logged as bugs://82832