Attribute.Custom.render() is stripping comment line chars //

[crisidev]

I am facing a weird issue with the Attribute class:

I am trying to render a Custom attribute before structures and enums and if there is a comment line rendered just after my call to Attribute.Custom.render(), the // is eaten away.

I have tracked it down to this line of code: https://github.com/awslabs/smithy-rs/blob/15e1b3425f56ff2606121e99dff11de38424c744/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/rustlang/RustTypes.kt#L377

If I change the line from writer.raw("#$bang[$annotation]") to writer.rust("##$bang[$annotation]") it start rendering as I would expect, but I am not sure of the implications of changing this line of code.

[crisidev]

@david-perez pointed out it'd fail if bang or annotation contains # but it looks like it shouldn't be possible: https://doc.rust-lang.org/reference/attributes.html

[rcoh]

so the relevant difference here is that raw uses writeInline and rust uses write. docs then uses newlinePrefix to set ///.

So when the writer isn't on a newline, that get suppressed. Let me see if I can make a fix