Add type assertions of the functions in src/composer.jl.

[Paalon]

Original title: Refactor src/composer.jl

• Add type assertions for all function arguments.
• Remove redundant new lines.
• Remove return at the end of the function.
• Add new lines to decrease the number of characters per line.

[codecov]

Codecov Report

Attention: Patch coverage is 77.27273% with 5 lines in your changes missing coverage. Please review.

Project coverage is 86.29%. Comparing base (844ad27) to head (372ce95).
Report is 5 commits behind head on master.

❗ Current head 372ce95 differs from pull request most recent head 14f1c4e

Please upload reports for the commit 14f1c4e to get more accurate results.

Files	Patch %	Lines
src/composer.jl	77.27%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #153      +/-   ##
==========================================
- Coverage   86.59%   86.29%   -0.31%     
==========================================
  Files          12       12              
  Lines        1626     1583      -43     
==========================================
- Hits         1408     1366      -42     
+ Misses        218      217       -1     

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[Paalon]

I formatted to my favorite style:

• 4 spaces for 1 indent
• if it's possible, the maximum number of characters per line is 92
• no return at the end of function
• if insert new lines in the arguments, split every arguments
• if use if ... else ... end or open(...) do io ... end in a function definition, such functions should use function f(...) ... end syntax and not should use f(...) = ... syntax.
• if a function definition is a simple value, use f(...) = ... syntax.
• empty lines between top-level variables is 1
• no space between default parameter: f(fruit=apple)
• in type union with Nothing, place Nothing at second: Union{T, Nothing}

but it is not absolute.

[Paalon]

I split this PR to type assertions and style formatting.

[Paalon]

Now, this PR only includes type assertions.

[kescobo]

I'm certainly not against this in principle, but is there a compelling need for it? It does not (typically) improve speed, and in this case I think the argument names are pretty clear, so annotating them with types doesn't add much clarity.

I don't feel stongly, just something to consider.

[GunnarFarneback]

It definitely won't make a difference to speed, but it adds a small amount of clarity and gives a faster error if you make a mistake when making code changes, so I think it's an improvement.

[Paalon]

I think this can be safely merged. @kescobo Can you merge this?