Remove box_alloc from Machine trait.

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -152,7 +152,7 @@ pub enum StackPopCleanup {
     /// `ret` stores the block we jump to on a normal return, while `unwind`
     /// stores the block used for cleanup during unwinding.
     Goto { ret: Option<mir::BasicBlock>, unwind: StackPopUnwind },
-    /// Just do nothing: Used by Main and for the `box_alloc` hook in miri.
+    /// Just do nothing: Used by Main and for TLS hooks in miri.
     /// `cleanup` says whether locals are deallocated. Static computation
     /// wants them leaked to intern what they need (and just throw away
     /// the entire `ecx` when it is done).

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -208,12 +208,6 @@ pub trait Machine<'mir, 'tcx>: Sized {
         right: &ImmTy<'tcx, Self::PointerTag>,
     ) -> InterpResult<'tcx, (Scalar<Self::PointerTag>, bool, Ty<'tcx>)>;
 
-    /// Heap allocations via the `box` keyword.
-    fn box_alloc(
-        ecx: &mut InterpCx<'mir, 'tcx, Self>,
-        dest: &PlaceTy<'tcx, Self::PointerTag>,
-    ) -> InterpResult<'tcx>;
-
     /// Called to read the specified `local` from the `frame`.
     /// Since reading a ZST is not actually accessing memory or locals, this is never invoked
     /// for ZST reads.