Snippet slicing does not handle multiline string literals correctly

[tayloraswift]

Description

a snippet slice directive must be a line comment of the form // snippet.*. unfortunately, DocC seems to be incorrectly interpreting the contents of a multiline string literal as slice comments. for example, the following snippet

// snippet.hide
import Snippets_Example

// snippet.show
let _:String = """
Only this part of the code will be shown.

// snippet.hide

Snippet markers inside multiline string literals are ignored.

// snippet.show
"""

ought to display the entire multiline string literal, but instead i get this:

Checklist

• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue.

Expected Behavior

DocC should leave the contents of the string literal alone.

Actual behavior

DocC is interpreting comment-like substrings inside the literal as if they were actual comment tokens, and performing cuts in those locations.

this can cause serious corruption of the contents, for example:

// snippet.hide
import Snippets_Example

// snippet.show
// snippet.hide
let _:String = """
Only this part of the code will be shown.

// snippet.show

Snippet markers inside multiline string literals are ignored.

"""

will produce unbalanced string literal delimiters.

Steps To Reproduce

No response

Swift-DocC Version Information

Plugin version 1.3.0

Swift Compiler Version Information

Swift version 5.10 (swift-5.10-RELEASE)
Target: x86_64-unknown-linux-gnu