add missing docs and tests for #59603 parse/tryparse

[cmcaine]

No description provided.

[jakobnissen]

We can use this PR to address the bugs that was introduced in my commit:

function parse_char(::Type{T}, c::AbstractChar, base::Integer, throw::Bool) where {T <: Real}
    a::UInt8 = (base <= 36 ? 10 : 36)
    (2 <= base <= 62) || _invalid_base(base)
    base = base % UInt8
    u = reinterpret(UInt32, Char(c)::Char)
    cp = u > 0x7a000000 ? 0xff : (cp >> 24) % UInt8
    d = UInt8('0') ≤ cp ≤ UInt8('9') ? cp - UInt8('0') :
        UInt8('A') ≤ cp ≤ UInt8('Z') ? cp - UInt8('A') + UInt8(10) :
        UInt8('a') ≤ cp ≤ UInt8('z') ? cp - UInt8('a') + a :
        0xff
    d < base || (throw ? _invalid_digit(base, c) : return nothing)
    convert(T, d)::T
end

[jakobnissen]

This solves two bugs:

• Most importantly, parse(Int, typemax(Char)) now behaves properly
• I don't think parse(Complex, '3') should work. The user should specify e.g. Complex{Int}. This should be handled by a distinct method since complex parsing is more... complex 🥁

[LilithHafner]

Yes