Add Encoder.at

[Lasering]

Closes #1536

[travisbrown]

Thanks, looks good to me, but do you mind adding a test here?

[Lasering]

Added. Not sure if data should have a more complicated type.

[Lasering]

Class Codec no longer compiles because it inherits final member at from both Encoder and Decoder, and JVM does not have reification so we cannot overload a method with different return types.

How do you want to solve this problem? Rename Encoder.at to something else? Suggestions:

• enclosed
• inside
• atField
• atObject

[travisbrown]

Oh, right. Another alternative would be to add an implicit x: Dummy argument. Let's see if other people have preferences.

[Lasering]

👍 on the dummy implicit.

[Lasering]

@travisbrown have you reached a decision on whether to use a different name or a dummy implicit? Meanwhile I changed my opinion. I think using a different, carefully chosen name is simpler and conveys the programmers objective better.

[Lasering]

@travisbrown implemented the DummyImplicit

[Lasering]

The approach of DummyImplicit fails if we want to implement an at for Codec (which would just return a Codec.from(this.at(field), this.at(field)))