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#4335·YouCompleteMe

YCM sends inaccurate range to HLS (Haskell Language Server)

Author: Aster89Created Jul 21, 2026Updated Jul 21, 2026

Issue Prelude

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  • I have read and understood YCM's CONTRIBUTING document.
  • I have read and understood YCM's CODE_OF_CONDUCT document.
  • I have read and understood YCM's README, especially the Frequently Asked Questions section.
  • I have searched YCM's issue tracker to find issues similar to the one I'm about to report and couldn't find an answer to my problem. (Example Google search.)
  • If filing a bug report, I have included the output of vim --version.
  • If filing a bug report, I have included the output of :YcmDebugInfo.
  • If filing a bug report, I have attached the contents of the logfiles using the :YcmToggleLogs command.
  • If filing a bug report, I have included which OS (including specific OS version) I am using.
  • If filing a bug report, I have included a minimal test case that reproduces my issue, using vim -Nu /path/to/YCM/vimrc_ycm_minimal, including what I expected to happen and what actually happened.
  • If filing a installation failure report, I have included the entire output of install.py (or cmake/make/ninja) including its invocation
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Issue Details

Provide a clear description of the problem, including the following key questions:

  • What did you do?

Include steps to reproduce here.

  1. vim -Nu /path/to/YCM/ycm_vimrc_minimal;
  2. let g:ycm_log_level = 'debug';
  3. source /the/file/at https://github.com/ycm-core/lsp-examples/blob/master/haskell/snippet.vim;
  4. insert this text:
    haskell
    data Foo = Foo

instance Show Foo where
  5. restart the server and wait for the -Wmissing-methods diagnostic on Show Foo;
  6. call :YcmCompleter FixIt with the cursor on each of the 8 positions in Show Foo;
  7. check the TX lines where YCM sends to HLS the range where the FixIt is reqeusted, e.g. by running this ex command:
    vim
    g/TX:.*},"range":{[^}]\+}[^}]\+}/echo substitute(getline('.'), '.*},\("range":{[^}]\+}[^}]\+}}\).*', '\1', '')`

Include description of a minimal test case, including any actual code required to reproduce the issue.

If you made changes to vimrc_ycm_minimal, pase them here:

no changes
  • What did you expect to happen?

Not sure, but anything "uniform", e.g.:

  1. the 1-character range corresponding to the cursor position, i.e.
    python
    "range":{"end":{"character":10,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":11,"line":2},"start":{"character":10,"line":2}}
"range":{"end":{"character":12,"line":2},"start":{"character":11,"line":2}}
"range":{"end":{"character":13,"line":2},"start":{"character":12,"line":2}}
"range":{ # I don't really know what to expect here, as it's the space in between Show and Foo
"range":{"end":{"character":15,"line":2},"start":{"character":14,"line":2}}
"range":{"end":{"character":16,"line":2},"start":{"character":15,"line":2}}
"range":{"end":{"character":17,"line":2},"start":{"character":16,"line":2}}
  2. the 1-character range corresponding to the first character of the identifier the cursor is currently on (this is what I see happening in C++),
    python
    "range":{"end":{"character":10,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":10,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":10,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":10,"line":2},"start":{"character":9,"line":2}}
"range":{ # I don't really know what to expect here, as it's the space in between Show and Foo
"range":{"end":{"character":15,"line":2},"start":{"character":14,"line":2}}
"range":{"end":{"character":15,"line":2},"start":{"character":14,"line":2}}
"range":{"end":{"character":15,"line":2},"start":{"character":14,"line":2}}
  3. a range corresponding to the whole identifier the cursor is currently on.
    python
    "range":{"end":{"character":13,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":13,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":13,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":13,"line":2},"start":{"character":9,"line":2}}
"range":{ # I don't really know what to expect here, as it's the space in between Show and Foo
"range":{"end":{"character":17,"line":2},"start":{"character":14,"line":2}}
"range":{"end":{"character":17,"line":2},"start":{"character":14,"line":2}}
"range":{"end":{"character":17,"line":2},"start":{"character":14,"line":2}}
  • What actually happened?

It feels like the range agrees with point 2 above, except when the cursor is on the second character of the identifier, in which case the range agrees with 1.

python
"range":{"end":{"character":10,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":11,"line":2},"start":{"character":10,"line":2}}
"range":{"end":{"character":10,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":10,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":10,"line":2},"start":{"character":9,"line":2}}
"range":{"end":{"character":15,"line":2},"start":{"character":14,"line":2}}
"range":{"end":{"character":16,"line":2},"start":{"character":15,"line":2}}
"range":{"end":{"character":15,"line":2},"start":{"character":14,"line":2}}

Diagnostic data

Output of vim --version

VIM - Vi IMproved 9.2 (2026 Feb 14, compiled Jul 18 2026 21:27:05)
Included patches: 1-804
Compiled by Arch Linux
Huge version with GTK3 GUI.  Features included (+) or not (-):
+acl                +float              +netbeans_intg      -tag_any_white
+arabic             +folding            +num64              +tcl/dyn
+autocmd            -footer             +packages           +termguicolors
+autochdir          +fork()             +path_extra         +terminal
-autoservername     +gettext            +perl/dyn           +terminfo
+balloon_eval       -hangul_input       +persistent_undo    +termresponse
+balloon_eval_term  +iconv              +popupwin           +textobjects
+browse             +insert_expand      +postscript         +textprop
++builtin_terms     +ipv6               +printer            +timers
+byte_offset        +job                +profile            +title
+channel            +jumplist           -python             +toolbar
+cindent            +keymap             +python3/dyn        +user_commands
+clientserver       +lambda             +quickfix           +vartabs
+clipboard          +langmap            +reltime            +vertsplit
+clipboard_provider +libcall            +rightleft          +vim9script
+cmdline_compl      +linebreak          +ruby/dyn           +viminfo
+cmdline_hist       +lispindent         +scrollbind         +virtualedit
+cmdline_info       +listcmds           +signs              +visual
+comments           +localmap           +smartindent        +visualextra
+conceal            +lua/dyn            +socketserver       +vreplace
+cryptv             +menu               -sodium             +wayland
+cscope             +mksession          +image              +wayland_clipboard
+cursorbind         +modify_fname       +image_sixel        +wildignore
+cursorshape        +mouse              +image_kitty        +wildmenu
+dialog_con_gui     +mouseshape         -image_gdi          +windows
+diff               +mouse_dec          +image_cairo        +writebackup
+digraphs           +mouse_gpm          -image_gdk          +X11
+dnd                -mouse_jsbterm      +sound              +xattr
-ebcdic             +mouse_netterm      +spell              -xfontset
+emacs_tags         +mouse_sgr          +startuptime        +xim
+eval               -mouse_sysmouse     +statusline         -xpm
+ex_extra           +mouse_urxvt        -sun_workshop       +xsmp_interact
+extra_search       +mouse_xterm        +syntax             +xterm_clipboard
-farsi              +multi_byte         +tabpanel           -xterm_save
+file_in_path       +multi_lang         +tag_binary         
+find_in_path       -mzscheme           -tag_old_static     
   system vimrc file: "/etc/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
 3rd user vimrc file: "~/.config/vim/vimrc"
      user exrc file: "$HOME/.exrc"
  system gvimrc file: "/etc/gvimrc"
    user gvimrc file: "$HOME/.gvimrc"
2nd user gvimrc file: "~/.vim/gvimrc"
3rd user gvimrc file: "~/.config/vim/gvimrc"
       defaults file: "$VIMRUNTIME/defaults.vim"
    system menu file: "$VIMRUNTIME/menu.vim"
  fall-back for $VIM: "/usr/share/vim"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_GTK -I/usr/include/gtk-3.0 -I/usr/include/pango-1.0 -I/usr/include/cloudproviders -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/glycin-2 -I/usr/include/at-spi2-atk/2.0 -I/usr/include/at-spi-2.0 -I/usr/include/atk-1.0 -I/usr/include/dbus-1.0 -I/usr/lib/dbus-1.0/include -I/usr/include/fribidi -I/usr/include/pixman-1 -I/usr/include/harfbuzz -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/gio-unix-2.0 -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/libmount -I/usr/include/blkid -I/usr/include/sysprof-6 -march=x86-64 -mtune=generic -O2 -pipe -fno-plt -fexceptions -Wformat -Werror=format-security -fstack-clash-protection -fcf-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -g -ffile-prefix-map=/build/vim/src=/usr/src/debug/vim -flto=auto -D_REENTRANT -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1 
Linking: gcc -Wl,-E -Wl,-rpath,/usr/lib/perl5/5.42/core_perl/CORE -Wl,-O1 -Wl,--sort-common -Wl,--as-needed -Wl,-z,relro -Wl,-z,now -Wl,-z,pack-relative-relocs -flto=auto -L/usr/local/lib -o vim -lgtk-3 -lgdk-3 -lpangocairo-1.0 -lcairo-gobject -lgdk_pixbuf-2.0 -latk-1.0 -lpango-1.0 -lcairo -lharfbuzz -lgio-2.0 -lgobject-2.0 -lglib-2.0 -lz -lSM -lICE -lXt -lX11 -lwayland-client -lm -lXdmcp -lSM -lICE -lm -ltinfo -lnsl -lcanberra -lacl -lattr -lgpm -L/usr/lib -ltclstub8.6 -ldl -lz -lpthread -lm

Output of YcmDebugInfo

Printing YouCompleteMe debug information...                                                                                                                                         
-- Resolve completions: Up front
-- Client logfile: /tmp/ycm_e1gzwzpw.log
-- Server Python interpreter: /usr/bin/python3
-- Server Python version: 3.14.6
-- Server has Clang support compiled in: False
-- Clang version: None
-- Extra configuration file found and loaded
-- Extra configuration path: /home/enrico/.ycm_extra_conf.py
-- GenericLSP completer debug information:
--   haskell-language-serverCompleter running
--   haskell-language-serverCompleter process ID: 580901
--   haskell-language-serverCompleter executable: ['/home/enrico/.ghcup/bin/haskell-language-server-wrapper', '--lsp']
--   haskell-language-serverCompleter logfiles:
--     /tmp/haskell_language_servercompleter_stderrcb1unx_2.log
--   haskell-language-serverCompleter Server State: Initialized
--   haskell-language-serverCompleter Project Directory: /home/enrico/haskell-language-server
--   haskell-language-serverCompleter Open Workspaces: {'/home/enrico/haskell-language-server'}
--   haskell-language-serverCompleter Settings: {
--   "haskell": {
--     "plugin": {
--       "case-split": {
--         "globalOn": true
--       },
--       "hlint": {
--         "globalOn": false
--       },
--       "rename": {
--         "config": {
--           "crossModule": true
--         }
--       }
--     },
--     "sessionLoading": "multipleComponents"
--   }
-- }
-- Server running at: http://127.0.0.1:52107
-- Server process ID: 580894
-- Server logfiles:
--   /tmp/ycmd_52107_stdout_6qfmdilc.log
--   /tmp/ycmd_52107_stderr_1jt82okb.log
-- Semantic highlighting supported: True
-- Virtual text supported: True
-- Popup windows supported: True

Output of YcmDiags

uffa.hs|3 col 10 warning| • No explicit implementation for either ‘showsPrec’ or ‘show’ • In the instance declaration for ‘Show Foo’ [GHC-06201]

Output of git rev-parse HEAD in YouCompleteMe installation directory

f8fbc1ddf440b0b34ac23bcd7b7d8d14a7fb80e6

Contents of YCM, ycmd and completion engine logfiles

Reproduce the issue with vim -Nu /path/to/YCM/vimrc_ycm_minimal, which enabled debug logging and other useful diagnostics. Include a link to a gist containing all of the log files listed by :YcmToggleLogs.

ycmd stderr (from the first TX message that feels wrong, otherwise it's too large for Gist to accept it): https://gist.github.com/Aster89/922b40abe1e1203a5e743bfa46163501

ycm complete log: https://gist.github.com/Aster89/c191f8b1d6fb7aad32525b6e11544670

HLS log: https://gist.github.com/Aster89/c65cc38e7670a4d773c7ccde0f283727

OS version, distribution, etc.

Up-to-date ArchLinux

Output of build/install commands

Include link to a gist containing the invocation and entire output of install.py if reporting an installation issue.

Source: ycm-core/YouCompleteMe

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