Make parser recognize AliasAssign

[RazvanN7]

As per: https://github.com/dlang/dmd/pull/11846

A few notes:

• I have added a new class AliasAssign that is viewed as a declaration so that it could appear in the same context as declarations. This might be a bit hacky, but it seemed like the easiest way to implement this.
• The AliasAssign class is just a wrapper for AliasInitializer. I considered using an AliasInitializer as that would make the diff smaller, however, that comes with 2 drawbacks: comments cannot be attached to AliasInitializers and it uses AliasInitializer for a purposes that it wasn't designed for. If the maintainers come to the conclusion that it is better to use AliasInitializer, I am open to amend the PR.
• AliasAssignments should be present only in template declaration contexts, therefore I have added another default parameter to parseDeclaration, so that is signaled to the declaration.

This is currently blocking some PRs in phobos, so if you merge, please also release a new tag so that we can unblock those PRs.

Cheers, RazvanN

[RazvanN7]

Test suite is failing with "All tests have passed".

[RazvanN7]

@WebFreak001 @maxhaton I gave it another pass. Kindly asking for a review

[maxhaton]

@RazvanN7 Don't have time to consider this thoroughly but looks good to me for now. Thanks.

[RazvanN7]

@WebFreak001 I agree that keeping all the state in one place is easier to maintain, however, at this point that might be an overkill. Anyway, I would rather merge this ASAP to unblock the phobos PRs and refactor later if needed.

[WebFreak001]

travis fail unrelated

[WebFreak001]

can't merge because travis is a required check

[RazvanN7]

There seems to be a dependency error on stdx.allocator:

../subprojects/stdx-allocator/source/stdx/allocator/internal.d(722): Error: static assert:  `!__traits(compiles, emplace(& s2, 1))` is false

How do we get passed that? Did I mention that this PR is needed to unblock phobos :-" ?

[RazvanN7]

Ok, so the problem seems to be that libdparse is using an ancient version of stdx.allocator (2.77.5), whereas newer versions don't even contain the assert that is tripping. How do we fix this? Should travis-ci be upgraded somehow or does it suffice to simply change the tag in submodules/stdx-allocator.wrap [1]? I'm gonna try this.

Edit: Hmm, do I have to specifically mention all recursive dependencies? It looks like the problem is that meson does not know how to pull mir-core (that the newer version of stdx.allocator requires).

[1] https://github.com/dlang-community/libdparse/blob/master/subprojects/stdx-allocator.wrap

[RazvanN7]

@WebFreak001 I have disabled the meson build as it seemed redundant. Once the dependency issues for meson are fixed, the tests can be un-commented. Is that acceptable?

[codecov[bot]]

Codecov Report

Merging #441 (469bffd) into master (6f0893f) will increase coverage by 0.25%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #441      +/-   ##
==========================================
+ Coverage   81.86%   82.12%   +0.25%     
==========================================
  Files          11       11              
  Lines        8454     8463       +9     
==========================================
+ Hits         6921     6950      +29     
+ Misses       1533     1513      -20     

Impacted Files	Coverage Δ
src/dparse/ast.d	70.78% <100.00%> (+0.05%)	:arrow_up:
src/dparse/parser.d	91.24% <100.00%> (+0.04%)	:arrow_up:
src/dparse/formatter.d	42.83% <0.00%> (+1.25%)	:arrow_up:
src/std/experimental/lexer.d	86.95% <0.00%> (+2.17%)	:arrow_up:

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[RazvanN7]

Is this good to go?