Align catch with switch syntax

[Andrew-Hanlon]

The existing catch block is already patterny with type handling and when conditions.

It would be great if the catch block had alignment with the switch expression and statement syntaxes.

Example of a few proposed syntaxes:

try { ... }
catch(Exception ex)
{                    
    case OperationCanceledException c when c.CancellationToken != token :
        throw;

    case OperationCanceledException _ :
    case InvalidOperationException  _ when state == knownState :
        return;
                    
    default:
        Log(ex);
        throw;
}


try { ... }
catch
{
    OperationCanceledException c when c.CancellationToken != token => throw;
    OperationCanceledException _                                   => return;
    InvalidOperationException  _ when state == knownState          => return;
    _                                                              => throw;
}

Or

try { ... }
catch (OperationCanceledException c) when (c.CancellationToken != token) => throw;
catch (InvalidOperationException _)  when (state == knownState)          => return;
catch (OperationCanceledException _)                                     => return;
catch (Exception _)                                                      => throw;

This would be an addition, not a change - and I believe would not have any issue with backward compatibility or interoperability with the existing syntax.

Importantly in both syntaxes the block contents (each case) would be equivalent to writing a set of catch(ExType ex) when (condition) {...} blocks. Thereby, if the default case is omitted, then standard catch fall-through is followed.

While there is zero criticality to this proposal, it would nicely unify the language syntax - and IMHO looks sleek.

(One half of this proposal was raised already in #2688)

[Joe4evr]

I don't see how this proposal concerning writing exception handlers is in any way related to 2568 which is about XML docs.

[Andrew-Hanlon]

@Joe4evr Sorry typo in issue number. Corrected.