Add EmptyableToPtr

[senago]

Closes #310

[samber]

Hi @senago and thanks for this first contribution.

In order to match other helper names, i would rename zero to empty.

Also, about converting a zero value to nil, to recreate a nullable type, i think you should check samber/mo and mo.EmptyableToOption

[codecov-commenter]

Codecov Report

Base: 99.28% // Head: 99.29% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (69ed2a6) compared to base (0ae2307).
Patch coverage: 100.00% of modified lines in pull request are covered.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #311   +/-   ##
=======================================
  Coverage   99.28%   99.29%           
=======================================
  Files          15       15           
  Lines        1971     1977    +6     
=======================================
+ Hits         1957     1963    +6     
  Misses         13       13           
  Partials        1        1           

Flag	Coverage Δ
unittests	99.29% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
type_manipulation.go	100.00% <100.00%> (ø)

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[senago]

Thank you for the review! Indeed, looks like here it's better to resort to reflect to cover more cases. Renamed the function to EmptyableToPtr for consistency with both lo and mo.

[vikstrous2]

I'm really curious now what's the difference between an equality check and reflection? Is slices one of them?

[senago]

Equality check is enabled for comparable types

// comparable is an interface that is implemented by all comparable types
// (booleans, numbers, strings, pointers, channels, arrays of comparable types,
// structs whose fields are all comparable types).

So, the point was to support other commonly used types - maps, slices of uncomparable types, errors, etc.