[SR-10011] Raw string with 1 double quote give compiler error about multi line strings

[swift-ci]

Previous ID	SR-10011
Radar	None
Original Reporter	MrLotU (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Attachment: Download

Environment

Swift 5.0 Snapshot from February 26, 2019

swift --version && uname -a output:

Apple Swift version 5.0-dev (LLVM 3207a50965, Clang 72dde1b133, Swift fa5d493110) Target: x86_64-apple-darwin18.2.0
Darwin LotU-MacBook-Pro.local 18.2.0 Darwin Kernel Version 18.2.0: Thu Dec 20 20:46:53 PST 2018; root:xnu-4903.241.1~1/RELEASE_X86_64 x86_64 

Platform: MacOS

Additional Detail from JIRA

Votes	1
Component/s	Compiler
Labels	Bug, Parser, StarterBug
Assignee	maustinstar (JIRA)
Priority	Medium

md5: 149b5f8191cb3508a0fd3fbf217154b8

Issue Description:

With the new raw strings in Swift 5, double quotes (") don't have to be escaped anymore (")

However, if I wanted a string containing just " an error will occur.
The code would look like this:

let str = #"""#

where I'd get the following compiler errors:

Multi-line string literal content must begin on a new line
// AND
Unterminated string literal

If you need any more info, feel free to ping me 🙂

[belkadan]

cc @rintaro, @johnno1962

[rintaro]

Currently, the Lexer eagerly eats #""" as the start of multiline text. To fix this, we have to handle this specially.
I'm going to mark this as StarterBug because this issue is not critical, and fix will be almost pure addition to the `Lexer.cpp`.
The fix will be something like:
Here https://github.com/apple/swift/blob/791b81f9/lib/Parse/Lexer.cpp#L1845-L1848

if (Multiline string starts with non-newline character) {
    if (The starting quote starts with '#'*n &&
        There is '"' followed by '#'*n *on the same line*) {
       // Treat it as a single line string literal.
    }
}

[swift-ci]

Comment by Michael Verges (JIRA)

I'd like to take this on as my first bug if that is okay. I think I have it working thanks to @rintaro's guidance. I'll spend some more time making sure everything works.

[swift-ci]

Comment by Michael Verges (JIRA)

Please check out this PR to resolve this:

#23115

[swift-ci]

Comment by Michael Verges (JIRA)

#34414