Redundant to_s warning

[sardaukar]

Maybe I'm making a mistake here, but I have a class with a to_s method defined, and when I write

puts "#{@cpu.pc.hex_p}\t#{instr}"

I get

0x00	#<Zaratite::Instruction:0x7fd655d34f80>

and with

puts "#{@cpu.pc.hex_p}\t#{instr.to_s}"

I get

0x00	LD SP, $fffe [0x31 0xfffe]

But ameba gives me

[W] Lint/RedundantStringCoercion: Redundant use of `Object#to_s` in interpolation
> puts "#{@cpu.pc.hex_p}\t#{instr.to_s}"

which makes sense but why is the behavior different with the to_s inside the interpolation ? Using Crystal 0.35.1

[Blacksmoke16]

Copying this over from Gitter:

Be sure to define to_s(io : IO) : Nil and not to_s : String, then write the content to io. The latter works when you explicitly call it, but when you remove it and let interpolation handle it; it's calling a different overload. So tl;dr this isn't a bug. However, might be worth adding a sentence/another error if you define the wrong to_s overload?

\cc @veelenga

[sardaukar]

Yep, forgot to close here. Thanks!

[veelenga]

Thanks guys.

However, might be worth adding a sentence/another error if you define the wrong to_s overload?

Yeah, already thought about it. Same for to_json/to_yaml.