Rollup merge of #114082 - ericmarkmartin:smir-nullary-op, r=spastorino

add stable NullaryOp

r? `@spastorino`

compiler/rustc_smir/src/rustc_smir/mod.rs

@@ -156,7 +156,9 @@ fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
                 ops.0.stable(tables),
                 ops.1.stable(tables),
             ),
-            NullaryOp(_, _) => todo!(),
+            NullaryOp(null_op, ty) => {
+                stable_mir::mir::Rvalue::NullaryOp(null_op.stable(tables), tables.intern_ty(*ty))
+            }
             UnaryOp(un_op, op) => {
                 stable_mir::mir::Rvalue::UnaryOp(un_op.stable(tables), op.stable(tables))
             }

compiler/rustc_smir/src/stable_mir/mir/body.rs

@@ -218,6 +218,9 @@ pub enum Rvalue {
     /// nature of this operation?
     ThreadLocalRef(stable_mir::CrateItem),
 
+    /// Computes a value as described by the operation.
+    NullaryOp(NullOp, Ty),
+
     /// Exactly like `BinaryOp`, but less operands.
     ///
     /// Also does two's-complement arithmetic. Negation requires a signed integer or a float;