Rollup merge of #99358 - compiler-errors:issue-99325, r=oli-obk

Allow `ValTree::try_to_raw_bytes` on `u8` array

Fixes #99325

cc `@b-naber` I think who touched this last in 705d818

Author: GuillaumeGomez

compiler/rustc_middle/src/ty/consts/valtree.rs

@@ -80,31 +80,25 @@ impl<'tcx> ValTree<'tcx> {
     }
 
     /// Get the values inside the ValTree as a slice of bytes. This only works for
-    /// constants with types &str and &[u8].
+    /// constants with types &str, &[u8], or [u8; _].
     pub fn try_to_raw_bytes(self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<&'tcx [u8]> {
         match ty.kind() {
             ty::Ref(_, inner_ty, _) => match inner_ty.kind() {
-                ty::Str => {
-                    let leafs = self
-                        .unwrap_branch()
-                        .into_iter()
-                        .map(|v| v.unwrap_leaf().try_to_u8().unwrap());
-
-                    return Some(tcx.arena.alloc_from_iter(leafs));
-                }
-                ty::Slice(slice_ty) if *slice_ty == tcx.types.u8 => {
-                    let leafs = self
-                        .unwrap_branch()
-                        .into_iter()
-                        .map(|v| v.unwrap_leaf().try_to_u8().unwrap());
-
-                    return Some(tcx.arena.alloc_from_iter(leafs));
-                }
-                _ => {}
+                // `&str` can be interpreted as raw bytes
+                ty::Str => {}
+                // `&[u8]` can be interpreted as raw bytes
+                ty::Slice(slice_ty) if *slice_ty == tcx.types.u8 => {}
+                // other `&_` can't be interpreted as raw bytes
+                _ => return None,
             },
-            _ => {}
+            // `[u8; N]` can be interpreted as raw bytes
+            ty::Array(array_ty, _) if *array_ty == tcx.types.u8 => {}
+            // Otherwise, type cannot be interpreted as raw bytes
+            _ => return None,
         }
 
-        None
+        Some(tcx.arena.alloc_from_iter(
+            self.unwrap_branch().into_iter().map(|v| v.unwrap_leaf().try_to_u8().unwrap()),
+        ))
     }
 }

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1452,7 +1452,7 @@ pub trait PrettyPrinter<'tcx>:
                 }
             },
             (ty::ValTree::Branch(_), ty::Array(t, _)) if *t == u8_type => {
-                let bytes = valtree.try_to_raw_bytes(self.tcx(), *t).unwrap_or_else(|| {
+                let bytes = valtree.try_to_raw_bytes(self.tcx(), ty).unwrap_or_else(|| {
                     bug!("expected to convert valtree to raw bytes for type {:?}", t)
                 });
                 p!("*");

src/test/mir-opt/issue-99325.rs

@@ -0,0 +1,12 @@
+#![feature(adt_const_params)]
+#![allow(incomplete_features)]
+
+pub fn function_with_bytes<const BYTES: &'static [u8; 4]>() -> &'static [u8] {
+    BYTES
+}
+
+// EMIT_MIR issue_99325.main.mir_map.0.mir
+pub fn main() {
+    assert_eq!(function_with_bytes::<b"AAAA">(), &[0x41, 0x41, 0x41, 0x41]);
+    assert_eq!(function_with_bytes::<{ &[0x41, 0x41, 0x41, 0x41] }>(), b"AAAA");
+}