From 933de407f6d794b652d9120d618425f6a7b73514 Mon Sep 17 00:00:00 2001
From: Faith Ekstrand <faith.ekstrand@collabora.com>
Date: Thu, 7 May 2026 15:41:35 -0400
Subject: [PATCH] nak: Don't use the proc macro to implement auto-boxing of ops

We can do this with a generic trait implementation as long as we have
something on it to keep it from recursing on Box<T>.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41410>
---
 src/nouveau/compiler/nak/ir.rs      | 10 ++++++++
 src/nouveau/compiler/nak/ir_proc.rs | 38 -----------------------------
 2 files changed, 10 insertions(+), 38 deletions(-)

diff --git a/src/nouveau/compiler/nak/ir.rs b/src/nouveau/compiler/nak/ir.rs
index cb056f3332a..29c9a5cb93a 100644
--- a/src/nouveau/compiler/nak/ir.rs
+++ b/src/nouveau/compiler/nak/ir.rs
@@ -8256,6 +8256,16 @@ const _: () = {
     debug_assert!(size_of::<Op>() == 16);
 };
 
+// The DisplayOp constraint exists to keep the type system from recursing
+impl<T: DisplayOp> From<T> for Op
+where
+    Box<T>: Into<Op>,
+{
+    fn from(op: T) -> Self {
+        Box::new(op).into()
+    }
+}
+
 impl Op {
     pub fn is_branch(&self) -> bool {
         matches!(
diff --git a/src/nouveau/compiler/nak/ir_proc.rs b/src/nouveau/compiler/nak/ir_proc.rs
index 371aafd8bd7..34ca9253bc5 100644
--- a/src/nouveau/compiler/nak/ir_proc.rs
+++ b/src/nouveau/compiler/nak/ir_proc.rs
@@ -145,32 +145,6 @@ pub fn enum_derive_display_op(input: TokenStream) -> TokenStream {
     }
 }
 
-fn into_box_inner_type<'a>(from_type: &'a syn::Type) -> Option<&'a syn::Type> {
-    let last = match from_type {
-        Type::Path(TypePath { path, .. }) => path.segments.last()?,
-        _ => return None,
-    };
-
-    if last.ident != "Box" {
-        return None;
-    }
-
-    let PathArguments::AngleBracketed(AngleBracketedGenericArguments {
-        args,
-        ..
-    }) = &last.arguments
-    else {
-        panic!("Expected Box<T> (with angle brackets)");
-    };
-
-    for arg in args {
-        if let GenericArgument::Type(inner_type) = arg {
-            return Some(inner_type);
-        }
-    }
-    panic!("Expected Box to use a type argument");
-}
-
 #[proc_macro_derive(FromVariants)]
 pub fn derive_from_variants(input: TokenStream) -> TokenStream {
     let DeriveInput { ident, data, .. } = parse_macro_input!(input);
@@ -198,18 +172,6 @@ pub fn derive_from_variants(input: TokenStream) -> TokenStream {
             };
 
             impls.extend(quote);
-
-            if let Some(inner_type) = into_box_inner_type(from_type) {
-                let quote = quote! {
-                    impl From<#inner_type> for #enum_type {
-                        fn from(value: #inner_type) -> Self {
-                            From::from(Box::new(value))
-                        }
-                    }
-                };
-
-                impls.extend(quote);
-            }
         }
     }