Error: SPIR-V requires location for user input/output

[no-more-secrets]

I have a GLSL fragment shader that the OpenGL drivers compile fine, but glslls gives errors like the following:

#version 330 core
...
flat out int frag_type;     ■ 'location' : SPIR-V requires location for user input/output

i.e., on all of the inputs in my fragment shader (and the outputs in my vertex shader) I get those error messages about SPIR-V that I don't understand. Am I doing something wrong in how I'm running glslls?

Setup: I'm using Neovim with builtin LSP client + nvim-lspconfig with default setup settings to run glslls.

[no-more-secrets]

I also tried passing the --target-env=opengl flag, but it doesn't seem to help.

[mixnam]

@no-more-secrets I created draft PR, that solved this problem for me.
But I don't have exp in c++, and might did smth wrong. Anyway I would appreciate if you tried to test my fixes and provided some feedback if fixes work for you as well.

lsp setup

require 'lspconfig'.glslls.setup {
    cmd = { 'glslls', '--stdin', '--target-env', 'opengl' },
}

[no-more-secrets]

@mixnam Thanks, I built your branch and it works for me and fixes the problem! Hopefully it will get merged @svenstaro