Update the CLanguageStandard and CXXLanguageStandard enums

[benrimmington]

Generate the enum cases by preprocessing the LangStandards.def file.

Motivation:

Follow-up to: #2716

Modifications:

• Add enum cases for C17/C18, C2x, and C++20.
• Deprecate enum cases for C++1z.
• Remove enum cases for C++2a (which aren't in release/5.3 yet).
• Update the raw string value for C94 (bug fix).

Result:

• New documentation comments.
• New cases for the latest C/C++ language standards.

[benrimmington]

The enum cases were generated with:

https://gist.github.com/benrimmington/3ca4f22389186766c060d99f05784c1a

1. In commit 642834d (using shouldGroupByPrefix = false), the two C++1z cases were manually moved, to preserve the existing order.

2. In commit 1d57496 (using shouldGroupByPrefix = true), library evolution and the synthesized Encodable conformance should allow enum cases to be re-ordered, if readability is improved.

The new C17/C18 modes don't seem to differ from C11, but the guiding principle of the SE-0181 review was "supporting all of the non-deprecated GCC/Clang modes".

For the deprecated C++1z modes, is the introduced: 4 correct?

Cc: @ddunbar

[abertelrud]

@swift-ci please smoke test

[abertelrud]

First, thanks for this clean-up!

Several of the enum cases have the same comments. From the .def file it looks as if they are synonyms... should it perhaps be noted in the comments that this is intentional (that it's a synonym?).

[abertelrud]

Looks as if the self-hosted Linux test fails because of package-collection related unit tests:

20:42:01 Test Case 'GitHubPackageMetadataProviderTests.testAPILimit' started at 2020-12-02 04:41:33.814
20:42:01 
/home/buildnode/jenkins/workspace/swift-package-manager-self-hosted-Linux-smoke-test/branch-main/swiftpm/Tests/PackageCollectionsTests/GitHubPackageMetadataProviderTests.swift:217: error: GitHubPackageMetadataProviderTests.testAPILimit : XCTAssertEqual failed: ("Optional(PackageCollections.GitHubPackageMetadataProvider.Errors.invalidResponse(https://api.github.com/repos/octocat/Hello-World, "Empty body"))") is not equal to ("Optional(PackageCollections.GitHubPackageMetadataProvider.Errors.apiLimitsExceeded(https://api.github.com/repos/octocat/Hello-World, 5))") - 
20:42:01 
/home/buildnode/jenkins/workspace/swift-package-manager-self-hosted-Linux-smoke-test/branch-main/swiftpm/Tests/PackageCollectionsTests/GitHubPackageMetadataProviderTests.swift:217: error: GitHubPackageMetadataProviderTests.testAPILimit : XCTAssertEqual failed: ("Optional(PackageCollections.GitHubPackageMetadataProvider.Errors.invalidResponse(https://api.github.com/repos/octocat/Hello-World, "Empty body"))") is not equal to ("Optional(PackageCollections.GitHubPackageMetadataProvider.Errors.apiLimitsExceeded(https://api.github.com/repos/octocat/Hello-World, 5))") - 
20:42:01 
/home/buildnode/jenkins/workspace/swift-package-manager-self-hosted-Linux-smoke-test/branch-main/swiftpm/Tests/PackageCollectionsTests/GitHubPackageMetadataProviderTests.swift:217: error: GitHubPackageMetadataProviderTests.testAPILimit : XCTAssertEqual failed: ("Optional(PackageCollections.GitHubPackageMetadataProvider.Errors.invalidResponse(https://api.github.com/repos/octocat/Hello-World, "Empty body"))") is not equal to ("Optional(PackageCollections.GitHubPackageMetadataProvider.Errors.apiLimitsExceeded(https://api.github.com/repos/octocat/Hello-World, 5))") - 

@tomerd or @yim-lee Do these look familiar to you?

[tomerd]

@tomerd or @yim-lee Do these look familiar to you?

hmm, I did run into this once before but thought I fixed it - this seems like a flaky test. re-run the tests and see if this goes away. if so, I will need to come back to fix this test

[abertelrud]

@swift-ci please smoke test

[abertelrud]

Thanks @benrimmington! It does look as if one of the unit test failures is related:

02:06:19 Test Case '-[PackageLoadingTests.PackageDescription4LoadingTests testLanguageStandards]' started.
02:06:19 
/Users/buildnode/jenkins/workspace/swift-package-manager-PR-osx-smoke-test/branch-main/swiftpm/Tests/PackageLoadingTests/PD4LoadingTests.swift:325: error: -[PackageLoadingTests.PackageDescription4LoadingTests testLanguageStandards] : XCTAssertEqual failed: ("Optional("iso9899:199409")") is not equal to ("Optional("iso9899:1994")")

[benrimmington]

@abertelrud I've updated the test assertion and documentation comments, and squashed the commits.

I didn't see the test failure locally, because it only gets as far as the guard statement.

https://github.com/apple/swift-package-manager/blob/c68fd5b22b51da157a93eaaa4aaa0e4d90bc38d9/Tests/PackageLoadingTests/PD4LoadingTests.swift#L308-L309

[abertelrud]

@swift-ci please smoke test

[abertelrud]

Great, thanks!

[abertelrud]

@swift-ci please smoke test