Refactor Host and related traits into a new traits module

This is a draft implementation of RustAudio#294. I'll leave this open for
feedback and potentially better trait naming suggestions or better
solutions in general!

cc @ishitatsuyuki

examples/beep.rs

@@ -1,7 +1,7 @@
 extern crate cpal;
 extern crate failure;
 
-use cpal::{Device, EventLoop, Host};
+use cpal::traits::{DeviceTrait, EventLoopTrait, HostTrait};
 
 fn main() -> Result<(), failure::Error> {
     let host = cpal::default_host();

examples/enumerate.rs

@@ -1,7 +1,7 @@
 extern crate cpal;
 extern crate failure;
 
-use cpal::{Device, Host};
+use cpal::traits::{DeviceTrait, HostTrait};
 
 fn main() -> Result<(), failure::Error> {
     println!("Supported hosts:\n  {:?}", cpal::ALL_HOSTS);

examples/feedback.rs

@@ -9,7 +9,7 @@
 extern crate cpal;
 extern crate failure;
 
-use cpal::{Device, EventLoop, Host};
+use cpal::traits::{DeviceTrait, EventLoopTrait, HostTrait};
 
 const LATENCY_MS: f32 = 150.0;
 

examples/record_wav.rs

@@ -6,7 +6,7 @@ extern crate cpal;
 extern crate failure;
 extern crate hound;
 
-use cpal::{Device, EventLoop, Host};
+use cpal::traits::{DeviceTrait, EventLoopTrait, HostTrait};
 
 fn main() -> Result<(), failure::Error> {
     // Use the default host for working with audio devices.

src/host/alsa/mod.rs

@@ -7,12 +7,9 @@ use ChannelCount;
 use BackendSpecificError;
 use BuildStreamError;
 use DefaultFormatError;
-use Device as DeviceTrait;
 use DeviceNameError;
 use DevicesError;
-use EventLoop as EventLoopTrait;
 use Format;
-use Host as HostTrait;
 use PauseStreamError;
 use PlayStreamError;
 use SampleFormat;
@@ -21,10 +18,10 @@ use SupportedFormatsError;
 use StreamData;
 use StreamDataResult;
 use StreamError;
-use StreamId as StreamIdTrait;
 use SupportedFormat;
 use UnknownTypeInputBuffer;
 use UnknownTypeOutputBuffer;
+use traits::{DeviceTrait, EventLoopTrait, HostTrait, StreamIdTrait};
 
 use std::{cmp, ffi, mem, ptr};
 use std::sync::Mutex;

src/host/coreaudio/mod.rs

@@ -5,23 +5,20 @@ use ChannelCount;
 use BackendSpecificError;
 use BuildStreamError;
 use DefaultFormatError;
-use Device as DeviceTrait;
 use DeviceNameError;
 use DevicesError;
-use EventLoop as EventLoopTrait;
 use Format;
-use Host as HostTrait;
 use PauseStreamError;
 use PlayStreamError;
 use SupportedFormatsError;
 use SampleFormat;
 use SampleRate;
 use StreamData;
 use StreamDataResult;
-use StreamId as StreamIdTrait;
 use SupportedFormat;
 use UnknownTypeInputBuffer;
 use UnknownTypeOutputBuffer;
+use traits::{DeviceTrait, EventLoopTrait, HostTrait, StreamIdTrait};
 
 use std::ffi::CStr;
 use std::fmt;

src/host/emscripten/mod.rs

@@ -10,20 +10,17 @@ use stdweb::web::set_timeout;
 
 use BuildStreamError;
 use DefaultFormatError;
-use Device as DeviceTrait;
 use DeviceNameError;
 use DevicesError;
-use EventLoop as EventLoopTrait;
 use Format;
-use Host as HostTrait;
 use PauseStreamError;
 use PlayStreamError;
 use SupportedFormatsError;
 use StreamData;
 use StreamDataResult;
-use StreamId as StreamIdTrait;
 use SupportedFormat;
 use UnknownTypeOutputBuffer;
+use traits::{DeviceTrait, EventLoopTrait, HostTrait, StreamIdTrait};
 
 /// The default emscripten host type.
 #[derive(Debug)]

src/host/null/mod.rs

@@ -2,18 +2,15 @@
 
 use BuildStreamError;
 use DefaultFormatError;
-use Device as DeviceTrait;
 use DevicesError;
 use DeviceNameError;
-use EventLoop as EventLoopTrait;
 use Format;
-use Host as HostTrait;
 use PauseStreamError;
 use PlayStreamError;
 use StreamDataResult;
 use SupportedFormatsError;
-use StreamId as StreamIdTrait;
 use SupportedFormat;
+use traits::{DeviceTrait, EventLoopTrait, HostTrait, StreamIdTrait};
 
 #[derive(Default)]
 pub struct Devices;

src/host/wasapi/mod.rs

@@ -3,19 +3,16 @@ extern crate winapi;
 use BackendSpecificError;
 use BuildStreamError;
 use DefaultFormatError;
-use Device as DeviceTrait;
 use DeviceNameError;
 use DevicesError;
-use EventLoop as EventLoopTrait;
 use Format;
-use Host as HostTrait;
 use PlayStreamError;
 use PauseStreamError;
 use StreamDataResult;
-use StreamId as StreamIdTrait;
 use SupportedFormatsError;
 use self::winapi::um::winnt::HRESULT;
 use std::io::Error as IoError;
+use traits::{DeviceTrait, EventLoopTrait, HostTrait, StreamIdTrait};
 pub use self::device::{Device, Devices, SupportedInputFormats, SupportedOutputFormats, default_input_device, default_output_device};
 pub use self::stream::{EventLoop, StreamId};