Meaningful changes from aggressive-clippy

I do want to enable a few specific lints, yet aggressive-clippy as a whole
isn't worthwhile.

common/std-shims/src/io.rs

@@ -53,10 +53,7 @@ mod shims {
 
   impl Read for &[u8] {
     fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
-      let mut read = buf.len();
-      if self.len() < buf.len() {
-        read = self.len();
-      }
+      let read = buf.len().min(self.len());
       buf[.. read].copy_from_slice(&self[.. read]);
       *self = &self[read ..];
       Ok(read)

common/std-shims/src/lib.rs

@@ -2,33 +2,12 @@
 #![doc = include_str!("../README.md")]
 #![cfg_attr(not(feature = "std"), no_std)]
 
-#[cfg(not(feature = "std"))]
-#[allow(unused_imports)]
-#[doc(hidden)]
-#[macro_use]
 pub extern crate alloc;
 
 pub mod sync;
 pub mod collections;
 pub mod io;
 
-pub mod vec {
-  #[cfg(not(feature = "std"))]
-  pub use alloc::vec::*;
-  #[cfg(feature = "std")]
-  pub use std::vec::*;
-}
-
-pub mod str {
-  #[cfg(not(feature = "std"))]
-  pub use alloc::str::*;
-  #[cfg(feature = "std")]
-  pub use std::str::*;
-}
-
-pub mod string {
-  #[cfg(not(feature = "std"))]
-  pub use alloc::string::*;
-  #[cfg(feature = "std")]
-  pub use std::string::*;
-}
+pub use alloc::vec;
+pub use alloc::str;
+pub use alloc::string;

common/std-shims/src/sync.rs

@@ -1,4 +1,5 @@
 pub use core::sync::*;
+pub use alloc::sync::*;
 
 mod mutex_shim {
   #[cfg(feature = "std")]
@@ -57,7 +58,7 @@ mod oncelock_shim {
       let mut lock = self.0.lock();
       if !*lock {
         unsafe {
-          (core::ptr::addr_of!(self.1) as *mut Option<_>).write_unaligned(Some(f()));
+          core::ptr::addr_of!(self.1).cast_mut().write_unaligned(Some(f()));
         }
       }
       *lock = true;