chore: add assertion to catch regressions

compiler/noirc_evaluator/src/ssa/acir_gen/acir_ir/acir_variable.rs

@@ -1514,7 +1514,7 @@ impl AcirContext {
             }
             Ok(())
         }
-        
+
         // This is a hack to ensure that if we're compiling a brillig entrypoint function then
         // we don't also add a number of range constraints.
         if !unsafe_return_values {

compiler/noirc_evaluator/src/ssa/acir_gen/acir_ir/generated_acir.rs

@@ -74,6 +74,10 @@ impl GeneratedAcir {
         }
     }
 
+    pub(crate) fn opcodes(&self) -> &[AcirOpcode] {
+        &self.opcodes
+    }
+
     pub(crate) fn take_opcodes(&mut self) -> Vec<AcirOpcode> {
         std::mem::take(&mut self.opcodes)
     }

compiler/noirc_evaluator/src/ssa/acir_gen/mod.rs

@@ -281,7 +281,16 @@ impl Context {
         for acir_var in output_vars {
             self.acir_context.return_var(acir_var)?;
         }
-        Ok(self.acir_context.finish(witness_inputs, Vec::new()))
+
+        let generated_acir = self.acir_context.finish(witness_inputs, Vec::new());
+
+        assert_eq!(
+            generated_acir.opcodes().len(),
+            1,
+            "Unconstrained programs should only generate a single opcode but multiple were emitted"
+        );
+
+        Ok(generated_acir)
     }
 
     /// Adds and binds `AcirVar`s for each numeric block parameter or block parameter array element.