completions for re-exported functions

[nolanderc]

closes #423

I encountered this bug while using https://github.com/ziglibs/zgl, which has many types that look like the following:

pub const VertexArray = enum(UInt) {
    invalid = 0,
    _,

    pub const create = gl.createVertexArray;
    pub const delete = gl.deleteVertexArray;
    pub const gen = gl.genVertexArray;
    pub const bind = gl.bindVertexArray;
    pub const enableVertexAttribute = gl.enableVertexArrayAttrib;
    pub const disableVertexAttribute = gl.disableVertexArrayAttrib;

    pub const attribFormat = gl.vertexArrayAttribFormat;
    pub const attribIFormat = gl.vertexArrayAttribIFormat;
    pub const attribLFormat = gl.vertexArrayAttribLFormat;

    pub const attribBinding = gl.vertexArrayAttribBinding;

    pub const vertexBuffer = gl.vertexArrayVertexBuffer;
    pub const elementBuffer = gl.vertexArrayElementBuffer;
};

Previously, there were no completions for any of the re-exported functions. But with this patch we yield completions for all re-exported functions which accept the container (VertexArray in the case above) as their first argument.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a4c568d) 75.22% compared to head (5cc8cfa) 75.55%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1656      +/-   ##
==========================================
+ Coverage   75.22%   75.55%   +0.33%     
==========================================
  Files          33       33              
  Lines        9054     9067      +13     
==========================================
+ Hits         6811     6851      +40     
+ Misses       2243     2216      -27     

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