Int64#parse* method docs should declare what exceptions they throw

[trinarytree]

Int64#parse{Hex, Int, Radix} apparently throw FormatException.
this should be declared in their docs so that callers can narrow a surrounding try-catch
to just the correct exception type.

[rakudrama]

It would be easier to use and more efficient to provide tryParse methods that return null if the input is malformed.

[vsmenon]

This is from package:fixnum? @trinarytree - can you please file there:

https://github.com/dart-lang/fixnum

?

[trinarytree]

i only intended this issue to be about fixing the docs, so the following will be slightly off topic:

if one were to redesign the interface, it should probably work like int.parse or double.parse.
unfortunately, those don't work exactly like each other.

• int.parse has has an optional named param named onError.
• double.parse has an optional positional param named onError.
  a named param is probably better because these will often be used with anonymous function expressions. e.g.

double.parse('e10', (_) => 1.23)

is less readable than

int.parse('e10', onError: (_) => 123)

if redesigning the interface is seriously on the table, let's spin off a separate issue.

[trinarytree]

i moved this issue to dart-lang/core#153