[SR-4469] Code completion for ambiguous types that must be qualified

[rxwei]

Previous ID	SR-4469
Radar	None
Original Reporter	@rxwei
Type	Improvement

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | CodeCompletion | |Labels | Improvement | |Assignee | None | |Priority | Medium | md5: 403e74e4b6c440616789b7924617f04e

Issue Description:

/// module ModuleA:
struct Foo {}

/// module ModuleB:
struct Foo {}

/// module C:
import A
import B
/// From this point, any use of Foo type must be qualified
protocol Fruit {
    associatedtype T
    func bar() -> T
}
struct Apple : Fruit {
    typealias T = ModuleB.Foo

    /// Use code completion for `func bar` here in Xcode...
    /// Completion result, unqualified
    func bar() -> Foo
    /// Diagnostics keep saying 'cannot match `() -> Foo` with `() -> Foo`' and 'does not conform to protocol Fruit'
}

I would expect code completion to use the qualified name since 1. typealias declaration is already qualified by the programmer 2. `Foo` must be qualified

[belkadan]

cc @nkcsgexi