[SR-10253] Type checker takes a very long time for tuple array

[tkrajacic]

Previous ID	SR-10253
Radar	None
Original Reporter	@tkrajacic
Type	Bug

Attachment: Download

Environment

Xcode 10.2, macOS 10.14.4 (18E226), Swift 5

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, Performance, TypeChecker
Assignee	None
Priority	Medium

md5: 837d8a515bbce96883d9d71a5c26b581

Issue Description:

This code takes between 15 and 25❗ seconds to type-check in the production app.

lazy var data: [(timespan: TimeInterval, caption: String)] = {
        
    return [
            (timespan: 0, caption: L10n.atDueDate),
            (timespan: 5 * kMinute, caption: L10n.xMinutesBefore(5)),
            (timespan: 15 * kMinute, caption: L10n.xMinutesBefore(15)),
            (timespan: 30 * kMinute, caption: L10n.xMinutesBefore(30)),
            (timespan: kHour, caption: L10n.oneHourBefore),
            (timespan: 2 * kHour, caption: L10n.xHoursBefore(2)),
            (timespan: kDay, caption: L10n.oneDayBefore),
            (timespan: 2 * kDay, caption: L10n.xDaysBefore(2)),
            (timespan: 7 * kDay, caption: L10n.oneWeekBefore),
    ]
}()

A simplified test-project is attached.

Of course it is easy to mitigate by just using a simple struct.

[belkadan]

cc @xedin