Added support for "use" keyword in closures

[sergeyklay]

Example of supported forms:

An empty closure with "use" keyword

namespace Example;
class Closure
{
    public function callback()
    {
        var abc = 42;
        return function () use (abc) { };
    }
}

A closure with "use" keyword and body

namespace Example;
class Closure
{
    public function callback()
    {
        var abc = 42;
        return function () use (&abc) {
            var r;
            let r = abc;
            let abc = null;
            return r;
        };
    }
}

A closure with params, "use" keyword and empty body

namespace Example;
class Closure
{
    public function callback()
    {
        var abc = 42;
        return function (one, two, three) use (abc) { };
    }
}

A closure with params, with "use" keyword and non empty body

namespace Example;
class Closure
{
    public function callback()
    {
        var abc = 42;
        return function (one, two, three) use (const & abc) {
            return [
                one,
                two,
                three,
                abc
            ];
        };
    }
}

A complex example with "use" keyword

class Closure
{
    public function callback(const resource &fp, const string filter, array &debug)
    {
        var line, cb;
        let line = fgets(fp);

        let cb = function (array matches) use ( & debug, const filter ) {
            let debug += [matches];
            if (matches[0] !== filter) {
                return strtolower(matches[0]);
            }

            return matches[0];
        };

        return preg_replace_callback("|<p>\s*\w|", cb, line);
    }
}

---

Refs:

• [NFR]Support use keyword in Closures zephir#1848
• Closure issue [$25] zephir#888

/cc @phalcon/zephir-team

[codecov]

Codecov Report

Merging #69 into development will increase coverage by 3.31%.
The diff coverage is 82%.

@@               Coverage Diff               @@
##           development      #69      +/-   ##
===============================================
+ Coverage        32.34%   35.66%   +3.31%     
===============================================
  Files                5        5              
  Lines             4399     4436      +37     
===============================================
+ Hits              1423     1582     +159     
+ Misses            2976     2854     -122

Impacted Files	Coverage Δ
parser/parser.h	44.25% <100%> (+2.72%)	⬆️
parser/zephir.lemon	16.13% <76.31%> (+4.05%)	⬆️
parser/scanner.re	50.09% <0%> (+2.91%)	⬆️
parser/scanner.c	39.51% <0%> (+3.44%)	⬆️

---

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[Jurigag]

As far as i know we currently don't support references, does it mean that in related zephir issue we gonna implement it as well?

[sergeyklay]

@Jurigag It is a possibility for my future plans.

n.b. The language scanner and parser have supported this syntactic structure since the very first days. So I don't introduced a brand new grammar