Code completion: Stop suggesting old-style protocol metatype syntax in Swift 6 mode

[AnthonyLatsis]

In Swift 6 mode, [.]Protocol¹ is no longer a valid suggestion. Per SE-0335, we should suggest two distinct [.]Type¹ completions for a plain protocol/composition — one aiming at any P.Type and another aiming at (any P).Type — that also insert a missing any prefix, and parenthesize the acted-upon existential in the second case.

Test case (should not succeed):

// RUN: %empty-directory(%t)
// RUN: %target-swift-ide-test -batch-code-completion -source-filename %s -filecheck %raw-FileCheck -completion-output-dir %t -swift-version 6

protocol P {}

let _: P#^COMPLETE1?check=META^#
let _: any P#^COMPLETE2?check=META^#
let _: (any P)#^COMPLETE3?check=META^#

// META: Keyword/None: .Protocol[#(any P).Type#]; name=Protocol

Environment

• Swift 5.9-dev (c1d5118)

Footnotes

1. [x] means x is optional ↩ ↩²

[Rajveer100]

@AnthonyLatsis
Could you give me a brief insight on this?

[AnthonyLatsis]

@Rajveer100 After updating the description, I am no longer positive this can be qualified as a beginner-friendly issue, but here is some tips:

• Code completion can be tested using the swift-ide-test executable found in the same place as swift-frontend (see test/IDE for example invocations).
• In code completion mode, this executable searches for code completion tokens spelled #^TOKEN_NAME^#.
• The places the Protocol completion is suggested are CompletionLookup::getPostfixKeywordCompletions and CompletionLookup::getTypeCompletions.

[AnthonyLatsis]

@ahoppen @rintaro Please review the good first issue status.

[ahoppen]

Yes, I agree that this could be a good first issue.