[SR-8046] [Source Compat] Sourcery: error: the compiler is unable to type-check this expression in reasonable time

[clackary]

Previous ID	SR-8046
Radar	rdar://problem/41278626
Original Reporter	@clackary
Type	Bug

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 1 | |Component/s | Compiler | |Labels | Bug, 4.2Regression, SourceCompatibility, TypeChecker | |Assignee | None | |Priority | Medium | md5: dc5b781e77d3d7f4381be55dda71f39b

Issue Description:

To reproduce:

1. Install latest GM/Beta Xcode
2. $ git clone git@github.com:apple/swift-source-compat-suite.git
3. $ cd swift-source-compat-suite
   To build Swift from scratch before testing:
4. $ ./reproduce.py master --project-path Sourcery
   Or if you've already built Swift:
5. $ ./reproduce.py master --project-path Sourcery --swiftc path/to/swiftc

See Build #1990.

/Users/buildnode/jenkins/workspace-private/swift-master-source-compat-suite/project_cache/Sourcery/.build/checkouts/StencilSwiftKit.git--3849885744839706587/Sources/SwiftIdentifier.swift:16:55: error: the compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions
private let headRanges: [CountableClosedRange<Int>] = [
                                                      ^

[clackary]

@swift-ci create