[SwiftParser] Diagnose missing 'in' after closure signature #370

Job	Run time
Test / macOS (Xcode ${{ matrix.xcode_version }} - ${{ matrix.os_version }} - ${{ matrix.arch }})	0s
Run tests using swift-syntax-dev-utils (Windows)	39m 56s
Run tests using swift-syntax-dev-utils (Linux)	23m 46s
Validate generated code	4m 5s
Test / Static Linux Swift SDK Build (${{ matrix.swift_version }} - ${{ matrix.os_version }})	0s
Test / Linux (5.9 - jammy)	4m 5s
Test / Linux (nightly-main - jammy)	5m 24s
Test / Swift SDK for Wasm Build (nightly-main - jammy)	2m 57s
Test / Linux (6.1 - jammy)	4m 19s
Test / Swift SDK for Wasm Build (nightly-6.2 - jammy)	2m 51s
Test / Linux (5.10 - jammy)	3m 59s
Test / Linux (nightly-6.2 - jammy)	5m 16s
Test / Swift SDK for Wasm Build (6.2 - jammy)	2m 5s
Test / Linux (6.2 - jammy)	4m 54s
Test / Embedded Swift SDK for Wasm Build (${{ matrix.swift_version }} - ${{ matrix.os_version }})	0s
Test / Windows (6.0 - windows-2022)	12m 46s
Test / Linux (6.0 - jammy)	4m 22s
Test / Windows (5.9 - windows-2022)	21m 57s
Test / Windows (6.1 - windows-2022)	13m 21s
Test / Windows (nightly-6.2 - windows-2022)	16m 19s
Test / Windows (nightly - windows-2022)	16m 16s
Test / Windows (6.2 - windows-2022)	15m 3s
Soundness / Unacceptable language check	4s
Soundness / Broken symlinks check	5s
Soundness / Shell check	52s
Soundness / Format check	58s
Soundness / YAML lint check	6s
Soundness / Python lint check	8s
Soundness / Documentation check	4m 37s
Soundness / License headers check	14s
Soundness / API breakage check	0s
	3h 30m 45s

Provide feedback