C++ : Trailing return types in function declaration result in illegal language match

Describe the issue/behavior that seems buggy

hljs.highlightAuto does not work on the following example, while hljs.highlightElement does.

Sample Code or Instructions to Reproduce

hljs.highlightAuto("auto main() -> int {\n    auto i = 42; // test\n    return i;\n}", [ 'cpp' ]) 

// result :
{
  "language": "cpp",
  "value": "auto main() -> int {\n    auto i = 42; // test\n    return i;\n}",
  "illegal": true,
  "relevance": 0,
  "_illegalBy": {
    "message": "Illegal lexeme \"-\" for mode \"function\"",
    "index": 11,
    "context": "auto main() -> int {\n    auto i = 42; // test\n    return i;\n}",
    "mode": {},
    "resultSoFar": ""
  },
 ...
}

This issue seems to be related to the arrow -> (feature name : trailing return type), which is legal in post-modern C++.

See the documentation of function declaration, section (2) (C++11), here on cppreference :

• https://en.cppreference.com/w/cpp/language/function

Expected behavior

• Consistency between highlightAuto and highlightElement behaviors
• Proper modern and post-modern C++ synthaxes match & detection

[joshgoebel]

PR welcome… we’re going to change the auto-detect stuff a lot in v12… and remove it from our test suite… it’s just too flakey and not great in any case… so changes like this will be trivial then - if you make it now you might have to fight with auto-detect getting a bunch of things wrong that now incorrectly flag as C++. But anyone is welcome to make a PR and we’l see. 😃

[GuillaumeDua]

Correct. 👍