Cannot handle C++14 generalized lambda captures when using with ccls

[finalpatch]

example code:

#include <string>
#include <iostream>
int main (int argc, char *argv[])
{
    std::string s = "hello";
    auto foo = [s = std::move(s)] {
                   std::cout << s << std::endl;
               };
    foo();
    return 0;
}

when cursor is placed on the s in std::move(s), eglot shows error message in echo area:

error in process filter: Wrong type argument: stringp, [5 14]

[cmm]

I'm seeing this even in plain C lately. Might be specific to ccls?

[joaotavora]

Can you try this with debug-on-error temporarily set to t? Use M-x toggle-debug-on-error. Then paste the backtrace here, please.

[finalpatch]

Debugger entered--Lisp error: (wrong-type-argument stringp [5 14])
  regexp-quote([5 14])
  #f(compiled-function () #<bytecode 0x410c5e85>)()
  eglot--call-with-interface((ParameterInformation (:label) (:documentation)) (:label [5 14]) #f(compiled-function () #<bytecode 0x410c5e85>))
  #f(compiled-function () #<bytecode 0x410c5e09>)()
  eglot--call-with-interface((SignatureInformation (:label) (:documentation :parameters)) (:label "move(_Tp &&__t) -> typename remove_reference<_Tp>:..." :parameters [(:label [5 14])]) #f(compiled-function () #<bytecode 0x410c5e09>))
  eglot--sig-info([(:label "move(_Tp &&__t) -> typename remove_reference<_Tp>:..." :parameters [(:label [5 14])]) (:label "move(_InputIterator __first, _InputIterator __last..." :parameters [(:label [5 27]) (:label [29 50]) (:label [52 76])]) (:label "move(__bit_iterator<_Cp, _IsConst> __first, __bit_..." :parameters [(:label [5 42]) (:label [44 80]) (:label [82 117])])] 0 0)
  #f(compiled-function () #<bytecode 0x4109fda9>)()
  eglot--call-with-interface((SignatureHelp (:signatures) (:activeSignature :activeParameter)) (:signatures [(:label "move(_Tp &&__t) -> typename remove_reference<_Tp>:..." :parameters [(:label [5 14])]) (:label "move(_InputIterator __first, _InputIterator __last..." :parameters [(:label [5 27]) (:label [29 50]) (:label [52 76])]) (:label "move(__bit_iterator<_Cp, _IsConst> __first, __bit_..." :parameters [(:label [5 42]) (:label [44 80]) (:label [82 117])])] :activeSignature 0 :activeParameter 0) #f(compiled-function () #<bytecode 0x4109fda9>))
  #f(compiled-function (jsonrpc-lambda-elem118) #<bytecode 0x41648235>)((:signatures [(:label "move(_Tp &&__t) -> typename remove_reference<_Tp>:..." :parameters [(:label [5 14])]) (:label "move(_InputIterator __first, _InputIterator __last..." :parameters [(:label [5 27]) (:label [29 50]) (:label [52 76])]) (:label "move(__bit_iterator<_Cp, _IsConst> __first, __bit_..." :parameters [(:label [5 42]) (:label [44 80]) (:label [82 117])])] :activeSignature 0 :activeParameter 0))
  jsonrpc-connection-receive(#<eglot-lsp-server eglot-lsp-server-41617440> (:jsonrpc "2.0" :id 339 :result (:signatures [(:label "move(_Tp &&__t) -> typename remove_reference<_Tp>:..." :parameters [(:label [5 14])]) (:label "move(_InputIterator __first, _InputIterator __last..." :parameters [(:label [5 27]) (:label [29 50]) (:label [52 76])]) (:label "move(__bit_iterator<_Cp, _IsConst> __first, __bit_..." :parameters [(:label [5 42]) (:label [44 80]) (:label [82 117])])] :activeSignature 0 :activeParameter 0)))
  jsonrpc--process-filter(#<process EGLOT (Desktop/c++-mode)> "Content-Length: 51\15\n\15\n{\"jsonrpc\":\"2.0\",\"id\":340,\"r...")

[finalpatch]

the last line fully expanded:

  jsonrpc--process-filter(#<process EGLOT (Desktop/c++-mode)> "Content-Length: 51\15\n\15\n{\"jsonrpc\":\"2.0\",\"id\":340,\"result\":{\"contents\":[]}}Content-Length: 38\15\n\15\n{\"jsonrpc\":\"2.0\",\"id\":341,\"result\":[]}Content-Length: 602\15\n\15\n{\"jsonrpc\":\"2.0\",\"id\":339,\"result\":{\"signatures\":[{\"label\":\"move(_Tp &&__t) -> typename remove_reference<_Tp>::type &&\",\"parameters\":[{\"label\":[5,14]}]},{\"label\":\"move(_InputIterator __first, _InputIterator __last, _OutputIterator __result) -> _OutputIterator\",\"parameters\":[{\"label\":[5,27]},{\"label\":[29,50]},{\"label\":[52,76]}]},{\"label\":\"move(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result) -> __bit_iterator<_Cp, false>\",\"parameters\":[{\"label\":[5,42]},{\"label\":[44,80]},{\"label\":[82,117]}]}],\"activeSignature\":0,\"activeParameter\":0}}")

[joaotavora]

Thanks. This is a bug. label used to be a string and now it can be vector of ints. actually this is a bug in ccls since I don't think eglot reported labelOffsetSupport as one of its capabilities. @MaskRay want to fix? Though I don't since it's very hard to support this in Eglot, too.

[MaskRay]

ParameterInformation.label being string was a mistake. My fault was that I thought clients would soon pick up the ParameterInformation.label: [number, number] (LSP 3.14 labelOffsetSupport: true) so I simply dropped ParameterInformation.label: string. I'm travelling and I'll find time to look into this closely.

BTW, the ParameterInformation.label enhancement proposal may be of interests: microsoft/language-server-protocol#640 more clients (eglot) may chime in to make this actually happen.

[joaotavora]

@MaskRay It's not very hard to support this in Eglot, I'll do it later this week if I find the time.

The link you gave me is a long read, I don't have time for it yet.

[joaotavora]

Should be fixed. Everybody test if possible and report back here if it works.

[finalpatch]

I can confirm bug is fixed.

[galeo]

I have reported issue #272 when using eglot with MS python language server.