Auto merge of #97004 - nnethercote:proc-macro-tweaks, r=eddyb

Proc macro tweaks

Various improvements I spotted while looking through the proc macro code.

r? `@eddyb`

compiler/rustc_builtin_macros/src/proc_macro_harness.rs

@@ -22,21 +22,16 @@ struct ProcMacroDerive {
     attrs: Vec<Symbol>,
 }
 
-enum ProcMacroDefType {
-    Attr,
-    Bang,
-}
-
 struct ProcMacroDef {
     id: NodeId,
     function_name: Ident,
     span: Span,
-    def_type: ProcMacroDefType,
 }
 
 enum ProcMacro {
     Derive(ProcMacroDerive),
-    Def(ProcMacroDef),
+    Attr(ProcMacroDef),
+    Bang(ProcMacroDef),
 }
 
 struct CollectProcMacros<'a> {
@@ -128,11 +123,10 @@ impl<'a> CollectProcMacros<'a> {
 
     fn collect_attr_proc_macro(&mut self, item: &'a ast::Item) {
         if self.in_root && item.vis.kind.is_pub() {
-            self.macros.push(ProcMacro::Def(ProcMacroDef {
+            self.macros.push(ProcMacro::Attr(ProcMacroDef {
                 id: item.id,
                 span: item.span,
                 function_name: item.ident,
-                def_type: ProcMacroDefType::Attr,
             }));
         } else {
             let msg = if !self.in_root {
@@ -147,11 +141,10 @@ impl<'a> CollectProcMacros<'a> {
 
     fn collect_bang_proc_macro(&mut self, item: &'a ast::Item) {
         if self.in_root && item.vis.kind.is_pub() {
-            self.macros.push(ProcMacro::Def(ProcMacroDef {
+            self.macros.push(ProcMacro::Bang(ProcMacroDef {
                 id: item.id,
                 span: item.span,
                 function_name: item.ident,
-                def_type: ProcMacroDefType::Bang,
             }));
         } else {
             let msg = if !self.in_root {
@@ -308,6 +301,17 @@ fn mk_decls(cx: &mut ExtCtxt<'_>, macros: &[ProcMacro]) -> P<ast::Item> {
         let proc_macro_ty_method_path = |cx: &ExtCtxt<'_>, method| {
             cx.expr_path(cx.path(span, vec![proc_macro, bridge, client, proc_macro_ty, method]))
         };
+        let attr_or_bang = |cx: &mut ExtCtxt<'_>, ca: &ProcMacroDef, ident| {
+            cx.resolver.declare_proc_macro(ca.id);
+            cx.expr_call(
+                span,
+                proc_macro_ty_method_path(cx, ident),
+                vec![
+                    cx.expr_str(ca.span, ca.function_name.name),
+                    local_path(cx, ca.span, ca.function_name),
+                ],
+            )
+        };
         macros
             .iter()
             .map(|m| match m {
@@ -329,22 +333,8 @@ fn mk_decls(cx: &mut ExtCtxt<'_>, macros: &[ProcMacro]) -> P<ast::Item> {
                         ],
                     )
                 }
-                ProcMacro::Def(ca) => {
-                    cx.resolver.declare_proc_macro(ca.id);
-                    let ident = match ca.def_type {
-                        ProcMacroDefType::Attr => attr,
-                        ProcMacroDefType::Bang => bang,
-                    };
-
-                    cx.expr_call(
-                        span,
-                        proc_macro_ty_method_path(cx, ident),
-                        vec![
-                            cx.expr_str(ca.span, ca.function_name.name),
-                            local_path(cx, ca.span, ca.function_name),
-                        ],
-                    )
-                }
+                ProcMacro::Attr(ca) => attr_or_bang(cx, &ca, attr),
+                ProcMacro::Bang(ca) => attr_or_bang(cx, &ca, bang),
             })
             .collect()
     };

compiler/rustc_expand/src/base.rs

@@ -266,7 +266,7 @@ where
     }
 }
 
-pub trait ProcMacro {
+pub trait BangProcMacro {
     fn expand<'cx>(
         &self,
         ecx: &'cx mut ExtCtxt<'_>,
@@ -275,7 +275,7 @@ pub trait ProcMacro {
     ) -> Result<TokenStream, ErrorGuaranteed>;
 }
 
-impl<F> ProcMacro for F
+impl<F> BangProcMacro for F
 where
     F: Fn(TokenStream) -> TokenStream,
 {
@@ -640,7 +640,7 @@ pub enum SyntaxExtensionKind {
     /// A token-based function-like macro.
     Bang(
         /// An expander with signature TokenStream -> TokenStream.
-        Box<dyn ProcMacro + sync::Sync + sync::Send>,
+        Box<dyn BangProcMacro + sync::Sync + sync::Send>,
     ),
 
     /// An AST-based function-like macro.

compiler/rustc_expand/src/proc_macro.rs

@@ -17,7 +17,7 @@ pub struct BangProcMacro {
     pub client: pm::bridge::client::Client<fn(pm::TokenStream) -> pm::TokenStream>,
 }
 
-impl base::ProcMacro for BangProcMacro {
+impl base::BangProcMacro for BangProcMacro {
     fn expand<'cx>(
         &self,
         ecx: &'cx mut ExtCtxt<'_>,
@@ -72,11 +72,11 @@ impl base::AttrProcMacro for AttrProcMacro {
     }
 }
 
-pub struct ProcMacroDerive {
+pub struct DeriveProcMacro {
     pub client: pm::bridge::client::Client<fn(pm::TokenStream) -> pm::TokenStream>,
 }
 
-impl MultiItemModifier for ProcMacroDerive {
+impl MultiItemModifier for DeriveProcMacro {
     fn expand(
         &self,
         ecx: &mut ExtCtxt<'_>,

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -11,7 +11,7 @@ use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{Lock, LockGuard, Lrc, OnceCell};
 use rustc_data_structures::unhash::UnhashMap;
 use rustc_expand::base::{SyntaxExtension, SyntaxExtensionKind};
-use rustc_expand::proc_macro::{AttrProcMacro, BangProcMacro, ProcMacroDerive};
+use rustc_expand::proc_macro::{AttrProcMacro, BangProcMacro, DeriveProcMacro};
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIndex, CRATE_DEF_INDEX, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathData, DefPathHash};
@@ -837,7 +837,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
                     attributes.iter().cloned().map(Symbol::intern).collect::<Vec<_>>();
                 (
                     trait_name,
-                    SyntaxExtensionKind::Derive(Box::new(ProcMacroDerive { client })),
+                    SyntaxExtensionKind::Derive(Box::new(DeriveProcMacro { client })),
                     helper_attrs,
                 )
             }

library/proc_macro/src/bridge/buffer.rs

@@ -6,37 +6,37 @@ use std::ops::{Deref, DerefMut};
 use std::slice;
 
 #[repr(C)]
-pub struct Buffer<T: Copy> {
-    data: *mut T,
+pub struct Buffer {
+    data: *mut u8,
     len: usize,
     capacity: usize,
-    reserve: extern "C" fn(Buffer<T>, usize) -> Buffer<T>,
-    drop: extern "C" fn(Buffer<T>),
+    reserve: extern "C" fn(Buffer, usize) -> Buffer,
+    drop: extern "C" fn(Buffer),
 }
 
-unsafe impl<T: Copy + Sync> Sync for Buffer<T> {}
-unsafe impl<T: Copy + Send> Send for Buffer<T> {}
+unsafe impl Sync for Buffer {}
+unsafe impl Send for Buffer {}
 
-impl<T: Copy> Default for Buffer<T> {
+impl Default for Buffer {
     fn default() -> Self {
         Self::from(vec![])
     }
 }
 
-impl<T: Copy> Deref for Buffer<T> {
-    type Target = [T];
-    fn deref(&self) -> &[T] {
-        unsafe { slice::from_raw_parts(self.data as *const T, self.len) }
+impl Deref for Buffer {
+    type Target = [u8];
+    fn deref(&self) -> &[u8] {
+        unsafe { slice::from_raw_parts(self.data as *const u8, self.len) }
     }
 }
 
-impl<T: Copy> DerefMut for Buffer<T> {
-    fn deref_mut(&mut self) -> &mut [T] {
+impl DerefMut for Buffer {
+    fn deref_mut(&mut self) -> &mut [u8] {
         unsafe { slice::from_raw_parts_mut(self.data, self.len) }
     }
 }
 
-impl<T: Copy> Buffer<T> {
+impl Buffer {
     pub(super) fn new() -> Self {
         Self::default()
     }
@@ -53,7 +53,7 @@ impl<T: Copy> Buffer<T> {
     // because in the case of small arrays, codegen can be more efficient
     // (avoiding a memmove call). With extend_from_slice, LLVM at least
     // currently is not able to make that optimization.
-    pub(super) fn extend_from_array<const N: usize>(&mut self, xs: &[T; N]) {
+    pub(super) fn extend_from_array<const N: usize>(&mut self, xs: &[u8; N]) {
         if xs.len() > (self.capacity - self.len) {
             let b = self.take();
             *self = (b.reserve)(b, xs.len());
@@ -64,7 +64,7 @@ impl<T: Copy> Buffer<T> {
         }
     }
 
-    pub(super) fn extend_from_slice(&mut self, xs: &[T]) {
+    pub(super) fn extend_from_slice(&mut self, xs: &[u8]) {
         if xs.len() > (self.capacity - self.len) {
             let b = self.take();
             *self = (b.reserve)(b, xs.len());
@@ -75,7 +75,7 @@ impl<T: Copy> Buffer<T> {
         }
     }
 
-    pub(super) fn push(&mut self, v: T) {
+    pub(super) fn push(&mut self, v: u8) {
         // The code here is taken from Vec::push, and we know that reserve()
         // will panic if we're exceeding isize::MAX bytes and so there's no need
         // to check for overflow.
@@ -90,7 +90,7 @@ impl<T: Copy> Buffer<T> {
     }
 }
 
-impl Write for Buffer<u8> {
+impl Write for Buffer {
     fn write(&mut self, xs: &[u8]) -> io::Result<usize> {
         self.extend_from_slice(xs);
         Ok(xs.len())
@@ -106,35 +106,35 @@ impl Write for Buffer<u8> {
     }
 }
 
-impl<T: Copy> Drop for Buffer<T> {
+impl Drop for Buffer {
     fn drop(&mut self) {
         let b = self.take();
         (b.drop)(b);
     }
 }
 
-impl<T: Copy> From<Vec<T>> for Buffer<T> {
-    fn from(mut v: Vec<T>) -> Self {
+impl From<Vec<u8>> for Buffer {
+    fn from(mut v: Vec<u8>) -> Self {
         let (data, len, capacity) = (v.as_mut_ptr(), v.len(), v.capacity());
         mem::forget(v);
 
         // This utility function is nested in here because it can *only*
         // be safely called on `Buffer`s created by *this* `proc_macro`.
-        fn to_vec<T: Copy>(b: Buffer<T>) -> Vec<T> {
+        fn to_vec(b: Buffer) -> Vec<u8> {
             unsafe {
                 let Buffer { data, len, capacity, .. } = b;
                 mem::forget(b);
                 Vec::from_raw_parts(data, len, capacity)
             }
         }
 
-        extern "C" fn reserve<T: Copy>(b: Buffer<T>, additional: usize) -> Buffer<T> {
+        extern "C" fn reserve(b: Buffer, additional: usize) -> Buffer {
             let mut v = to_vec(b);
             v.reserve(additional);
             Buffer::from(v)
         }
 
-        extern "C" fn drop<T: Copy>(b: Buffer<T>) {
+        extern "C" fn drop(b: Buffer) {
             mem::drop(to_vec(b));
         }