[SR-8004] Many SourceKit-related crashes with modified stdlib

[dabrahams]

Previous ID	SR-8004
Radar	rdar://problem/41149730
Original Reporter	@dabrahams
Type	Bug

Attachment: Download

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | CodeCompletion | |Labels | Bug | |Assignee | None | |Priority | Medium | md5: 7520e03628d586f9538461057c3f158e

Issue Description:

If you check out https://github.com/dabrahams/swift/commit/3858fc83258b2397230a729f5633088f43ffe874 and build the validation tests with

build-script --skip-build-ios-device --skip-build-tvos-device --skip-build-compiler-rt --debug-swift-stdlib --skip-build-benchmarks --release --swift-stdlib-assertions --swift-stdlib-build-type=Debug --lit-args=-v --validation-test

the following will crash:

IDE/complete_loop.swift (10 of 11182) SourceKit/CodeComplete/complete_cache.swift (12 of 11182) SourceKit/CodeComplete/complete_custom.swift (14 of 11182) IDE/complete_expr_postfix_begin.swift (16 of 11182) SourceKit/DocSupport/doc_stdlib.swift (17 of 11182) SourceKit/CursorInfo/cursor_stdlib.swift (18 of 11182) SourceKit/DocSupport/doc_clang_module.swift (20 of 11182) IDE/complete_stmt_controlling_expr.swift (24 of 11182) IDE/complete_at_top_level.swift (29 of 11182)

A complete testing log is attached.

[dabrahams]

@swift-ci create