Improving error messages when we cannot deconvert a type.

[krisajenkins]

When you send a message to a DerivedActor, we convert the message to the receiver's type. If the message sending fails, we deconvert it to show you which message failed. However, if the deconversion fails, you get a very terse error message:

PANIC: Failed to deconvert message to from type

Obviously that provides very little diagnostic information. This change greatly improves the error to something like:

PANIC: Failed to deconvert message from klite::queries::query_watcher::QueryWatcherMessage to klite::connection_manager::ClientResponse when sending back to: Actor { name: Some("current_subscribers.sql"), id: Local(8) }

Now you know exactly which kind of message was sent to whom, and which TryFrom instance you need to fix.

(NOTE: These errors should be very rare. TryFrom should be implemented properly. But when very rare errors happen that's exactly when you need very good error messages.)

[slawlor]

can you run clippy and update the PR? Thanks!

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Please upload report for BASE (main@7f12788). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
ractor/src/actor/derived_actor.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #366   +/-   ##
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  Coverage        ?   82.28%           
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  Files           ?       70           
  Lines           ?    12765           
  Branches        ?        0           
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  Hits            ?    10504           
  Misses          ?     2261           
  Partials        ?        0           

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[krisajenkins]

I've just taken a look at the clippy warnings, and it doesn't look like they're related to this change. They're about using the newer-style inline variable names in format strings:

error: variables can be used directly in the `format!` string
Error:    --> ractor/src/errors.rs:243:31
    |
243 |             Self::Spawn(s) => write!(f, "Spawn({:?})", s),
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^

I can fix those if you'd like, but it might belong in a different PR?

[slawlor]

Yeah please just lint the whole project. It's the typical flow even if it is touching some other code to keep the lib up to date. Thanks!