Rollup merge of #147386 - cyrgani:proc-macro-cleanup-2, r=petrochenkov

some more `proc_macro` cleanups

Several smaller cleanups to `proc_macro`. Commits 1 and 3 seem pretty trivial to me, commit 2 might be worth it or not.

Followup to #147166.

Author: matthiaskrgr

library/proc_macro/src/bridge/arena.rs

@@ -7,7 +7,7 @@
 use std::cell::{Cell, RefCell};
 use std::mem::MaybeUninit;
 use std::ops::Range;
-use std::{cmp, ptr, slice, str};
+use std::{cmp, ptr, slice};
 
 // The arenas start with PAGE-sized chunks, and then each new chunk is twice as
 // big as its predecessor, up until we reach HUGE_PAGE-sized chunks, whereupon
@@ -90,14 +90,13 @@ impl Arena {
             return &mut [];
         }
 
-        loop {
-            if let Some(a) = self.alloc_raw_without_grow(bytes) {
-                break a;
-            }
-            // No free space left. Allocate a new chunk to satisfy the request.
-            // On failure the grow will panic or abort.
-            self.grow(bytes);
+        if let Some(a) = self.alloc_raw_without_grow(bytes) {
+            return a;
         }
+        // No free space left. Allocate a new chunk to satisfy the request.
+        // On failure the grow will panic or abort.
+        self.grow(bytes);
+        self.alloc_raw_without_grow(bytes).unwrap()
     }
 
     #[allow(clippy::mut_from_ref)] // arena allocator

library/proc_macro/src/bridge/mod.rs

@@ -143,7 +143,7 @@ mod symbol;
 
 use buffer::Buffer;
 pub use rpc::PanicMessage;
-use rpc::{Decode, DecodeMut, Encode, Reader, Writer};
+use rpc::{DecodeMut, Encode, Reader, Writer};
 
 /// Configuration for establishing an active connection between a server and a
 /// client.  The server creates the bridge config (`run_server` in `server.rs`),

library/proc_macro/src/bridge/rpc.rs

@@ -3,7 +3,6 @@
 use std::any::Any;
 use std::io::Write;
 use std::num::NonZero;
-use std::str;
 
 pub(super) type Writer = super::buffer::Buffer;
 
@@ -13,10 +12,6 @@ pub(super) trait Encode<S>: Sized {
 
 pub(super) type Reader<'a> = &'a [u8];
 
-pub(super) trait Decode<'a, 's, S>: Sized {
-    fn decode(r: &mut Reader<'a>, s: &'s S) -> Self;
-}
-
 pub(super) trait DecodeMut<'a, 's, S>: Sized {
     fn decode(r: &mut Reader<'a>, s: &'s mut S) -> Self;
 }
@@ -31,7 +26,7 @@ macro_rules! rpc_encode_decode {
 
         impl<S> DecodeMut<'_, '_, S> for $ty {
             fn decode(r: &mut Reader<'_>, _: &mut S) -> Self {
-                const N: usize = ::std::mem::size_of::<$ty>();
+                const N: usize = size_of::<$ty>();
 
                 let mut bytes = [0; N];
                 bytes.copy_from_slice(&r[..N]);

library/proc_macro/src/bridge/server.rs

@@ -40,10 +40,10 @@ macro_rules! define_server_handles {
                 }
             }
 
-            impl<'s, S: Types> Decode<'_, 's, HandleStore<MarkedTypes<S>>>
+            impl<'s, S: Types> DecodeMut<'_, 's, HandleStore<MarkedTypes<S>>>
                 for &'s Marked<S::$oty, client::$oty>
             {
-                fn decode(r: &mut Reader<'_>, s: &'s HandleStore<MarkedTypes<S>>) -> Self {
+                fn decode(r: &mut Reader<'_>, s: &'s mut HandleStore<MarkedTypes<S>>) -> Self {
                     &s.$oty[handle::Handle::decode(r, &mut ())]
                 }
             }

library/proc_macro/src/bridge/symbol.rs

@@ -11,7 +11,6 @@
 
 use std::cell::RefCell;
 use std::num::NonZero;
-use std::str;
 
 use super::*;