Rollup merge of #77560 - rschoon:fix-litkind-rc-bytebuf, r=lcnr

Fix LitKind's byte buffer to use refcounted slice

While working on adding a new lint for clippy (see https://github.com/rust-lang/rust-clippy/pull/6044) for avoiding shared ownership of "mutable buffer" types (such as using `Rc<Vec<T>>` instead of `Rc<[T]>`), I noticed a type exported from rustc_ast and used by clippy gets caught by the lint. This PR fixes the exported type.

This PR includes the actual change to clippy too, but I will open a PR directly against clippy for that part (although it will currently fail to build there).

compiler/rustc_ast/src/ast.rs

@@ -1606,7 +1606,7 @@ pub enum LitKind {
     /// A string literal (`"foo"`).
     Str(Symbol, StrStyle),
     /// A byte string (`b"foo"`).
-    ByteStr(Lrc<Vec<u8>>),
+    ByteStr(Lrc<[u8]>),
     /// A byte char (`b'f'`).
     Byte(u8),
     /// A character literal (`'a'`).

compiler/rustc_ast/src/util/literal.rs

@@ -4,7 +4,6 @@ use crate::ast::{self, Lit, LitKind};
 use crate::token::{self, Token};
 use crate::tokenstream::TokenTree;
 
-use rustc_data_structures::sync::Lrc;
 use rustc_lexer::unescape::{unescape_byte, unescape_char};
 use rustc_lexer::unescape::{unescape_byte_literal, unescape_literal, Mode};
 use rustc_span::symbol::{kw, sym, Symbol};
@@ -108,7 +107,7 @@ impl LitKind {
                 });
                 error?;
                 buf.shrink_to_fit();
-                LitKind::ByteStr(Lrc::new(buf))
+                LitKind::ByteStr(buf.into())
             }
             token::ByteStrRaw(_) => {
                 let s = symbol.as_str();
@@ -128,7 +127,7 @@ impl LitKind {
                     symbol.to_string().into_bytes()
                 };
 
-                LitKind::ByteStr(Lrc::new(bytes))
+                LitKind::ByteStr(bytes.into())
             }
             token::Err => LitKind::Err(symbol),
         })

compiler/rustc_builtin_macros/src/source_util.rs

@@ -13,8 +13,6 @@ use rustc_span::{self, Pos, Span};
 use smallvec::SmallVec;
 use std::rc::Rc;
 
-use rustc_data_structures::sync::Lrc;
-
 // These macros all relate to the file system; they either return
 // the column/row/filename of the expression, or they include
 // a given file into the current one.
@@ -216,7 +214,7 @@ pub fn expand_include_bytes(
         }
     };
     match cx.source_map().load_binary_file(&file) {
-        Ok(bytes) => base::MacEager::expr(cx.expr_lit(sp, ast::LitKind::ByteStr(Lrc::new(bytes)))),
+        Ok(bytes) => base::MacEager::expr(cx.expr_lit(sp, ast::LitKind::ByteStr(bytes.into()))),
         Err(e) => {
             cx.span_err(sp, &format!("couldn't read {}: {}", file.display(), e));
             DummyResult::any(sp)

compiler/rustc_mir_build/src/thir/constant.rs

@@ -31,7 +31,7 @@ crate fn lit_to_const<'tcx>(
         (ast::LitKind::ByteStr(data), ty::Ref(_, inner_ty, _))
             if matches!(inner_ty.kind(), ty::Slice(_)) =>
         {
-            let allocation = Allocation::from_byte_aligned_bytes(data as &Vec<u8>);
+            let allocation = Allocation::from_byte_aligned_bytes(data as &[u8]);
             let allocation = tcx.intern_const_alloc(allocation);
             ConstValue::Slice { data: allocation, start: 0, end: data.len() }
         }

src/tools/clippy/clippy_lints/src/consts.rs

@@ -155,7 +155,7 @@ pub fn lit_to_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
     match *lit {
         LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
         LitKind::Byte(b) => Constant::Int(u128::from(b)),
-        LitKind::ByteStr(ref s) => Constant::Binary(Lrc::from(s.as_slice())),
+        LitKind::ByteStr(ref s) => Constant::Binary(Lrc::clone(s)),
         LitKind::Char(c) => Constant::Char(c),
         LitKind::Int(n, _) => Constant::Int(n),
         LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {