chore(hal,core): use core::{error::Error,format} instead of std

This allows `wgpu-hal` to be used in `no_std` environments, except that
currently, only the `noop` backend supports `no_std`.
In the future, `cfg(all(gles, webgl))` should also be `no_std`, but that
requires further work.

Co-Authored_by: Kevin Reid <kpreid@switchb.org>

wgpu-core/src/device/mod.rs

@@ -303,7 +303,7 @@ impl fmt::Display for DeviceMismatch {
     }
 }
 
-impl std::error::Error for DeviceMismatch {}
+impl core::error::Error for DeviceMismatch {}
 
 #[derive(Clone, Debug, Error)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]

wgpu-core/src/error.rs

@@ -1,6 +1,5 @@
 use alloc::{boxed::Box, string::String, sync::Arc, vec::Vec};
-use core::fmt;
-use std::error::Error; // TODO(https://github.com/gfx-rs/wgpu/issues/6826): use core::error after MSRV bump
+use core::{error::Error, fmt};
 
 use thiserror::Error;
 

wgpu-hal/src/auxil/renderdoc.rs

@@ -1,6 +1,7 @@
 //! RenderDoc integration - <https://renderdoc.org/>
 #![cfg_attr(not(any(feature = "gles", feature = "vulkan")), allow(dead_code))]
 
+use alloc::format;
 use alloc::string::String;
 use core::{ffi, ptr};
 

wgpu-hal/src/lib.rs

@@ -240,8 +240,9 @@
 
 extern crate alloc;
 extern crate wgpu_types as wgt;
-// TODO(https://github.com/gfx-rs/wgpu/issues/6826): disable std except on noop and gles-WebGL.
-// Requires Rust 1.81 for core::error::Error.
+// Each of these backends needs `std` in some fashion; usually `std::thread` functions.
+// TODO(https://github.com/gfx-rs/wgpu/issues/6826): gles-WebGL backend should be made no-std
+#[cfg(any(dx12, gles, metal, vulkan))]
 #[macro_use]
 extern crate std;
 
@@ -290,12 +291,12 @@ use alloc::boxed::Box;
 use alloc::{borrow::Cow, string::String, sync::Arc, vec::Vec};
 use core::{
     borrow::Borrow,
+    error::Error,
     fmt,
     num::NonZeroU32,
     ops::{Range, RangeInclusive},
     ptr::NonNull,
 };
-use std::error::Error; // TODO(https://github.com/gfx-rs/wgpu/issues/6826): use core::error after MSRV bump
 
 use bitflags::bitflags;
 use parking_lot::Mutex;

wgpu/src/api/surface.rs

@@ -1,6 +1,5 @@
 use alloc::{boxed::Box, string::String, vec, vec::Vec};
-use core::fmt;
-use std::error; // TODO(https://github.com/gfx-rs/wgpu/issues/6826): use core::error after MSRV bump
+use core::{error, fmt};
 
 use parking_lot::Mutex;
 use raw_window_handle::{HasDisplayHandle, HasWindowHandle};

wgpu/src/api/surface_texture.rs

@@ -1,5 +1,4 @@
-use core::fmt;
-use std::error; // TODO(https://github.com/gfx-rs/wgpu/issues/6826): use core::error after MSRV bump
+use core::{error, fmt};
 use std::thread;
 
 use crate::*;