use TS type guards over : boolean in type check functions (R.is, R.is[X])

[KiaraGrouwstra]

We now have e.g. is(ctor: any, val: any): boolean;, which the TS docs tell us we can further strengthen using type guards. Let's do that. :)

Edit: on second thought, I don't think at the type level we get enough information to better type the other is functions, beside the generic one...

[TylerYang]

Could sombody take a look at this mr, please? I just meet a use case that might need to merge this mr,

function grepSomethingRecursively(grepPatterns: String | String[]) {
    if (R.is(Array, grepPatterns)) {
        R.forEach(doSomething, grepPatterns) 
        //throw exception: argument of type 'string | string[]' is not assignable to parameter of type 'string[]'.
    } else {
        ...
    }
}

R.forEach is required to take array as its parameters.
And with running R.is the type of grepPatterns cannot be inferred by the checker. So it throws an exception.

In contrast, the lodash works fine due to the definition.

[TylerYang]

Hi @tycho01 ,I just copy your mr and try to run with this function, it throws the exception also.

//throw exception: argument of type 'string | string[]' is not assignable to parameter of type 'string[]'.

[KiaraGrouwstra]

@TylerYang: thanks for reporting this! I just merged in your use-case as a new test and implemented a fix.

[TylerYang]

NP : )