[cfe-dev] [RFC][PATCH] Implementation for completion in call context for C++

[Francisco Lopes]

Hi,

I've improved completion in call context to work with C++'s templates,
member functions, et al.

Notice: an important aspect of this implementation is that I've took freedom
to change the previous behavior for completion in call context at all.

As can be seen, in lib/Sema/SemaCodeComplete.cpp this comment:

  // When we're code-completing for a call, we fall back to ordinary
  // name code-completion whenever we can't produce specific
  // results. We may want to revisit this strategy in the future,
  // e.g., by merging the two kinds of results.

was changed to this:

  // When we're code-completing for a call, we DON'T fall back to ordinary
  // name code-completion whenever we can't produce specific
  // results. This will do "parameter completion" solely.
  // I think "parameter completion" is not a good classification, since this
  // is useful solely for providing hints and not code-completing.

The rationale behind this change is:
  - The former comment shows that completion in call context is still not
    in a definite state, open to discussion.
  - I firmly believe this new behavior is for good. In call context, 99% of
    the time, code authoring tools will be interested in information about
the
    prototype and arguments solely, not in all possible kinds of expressions
    that can fit as an argument. This behavior turns the interface slower
than
    necessary to have almost no benefit.
    So I believe that completion in call context just after '(' and ','
should
    work similarly as for member access: only provide what's of interest,
which
    parametric information (function prototypes, current argument, parameter
    types, etc.).

Despite this, I should be able revert to the former behavior in the change
set
without much trouble, in case there's no agreement on this, while still
providing the new set of completions.

The following is a video that covers the new behavior, so that's easy to see
what got changed. It's based on the test set that's part of the patch:

  https://vimeo.com/115990512

The change set can be browsed here:

  https://github.com/oblitum/clang/tree/improved_argument_hints

The Subversion compatible patch:

  https://gist.github.com/oblitum/d24d7d2f9c6ee5cdcea1

This got started for YouCompleteMe:

  https://github.com/Valloric/YouCompleteMe/pull/1300

TODO:
  Functors (classes that overload operator()), Constructors, ...

(I've already obtained commit access)

Att,
Francisco Lopes

PS: I'm actively looking for a job, remote or relocation, any help very much
    appreciated!
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