improve specificity of MemoryAlreadySet error message

Author: morganthomas

crates/lean_compiler/src/lib.rs

@@ -24,8 +24,9 @@ pub fn compile_program(program: String) -> Bytecode {
     // for (loc, name) in function_locations.iter() {
     //     println!("{name}: {loc}");
     // }
-    // println!("\n\nCompiled Program:\n\n{compiled}");
-    compile_to_low_level_bytecode(intermediate_bytecode, program, function_locations).unwrap()
+    let compiled = compile_to_low_level_bytecode(intermediate_bytecode, program, function_locations).unwrap();
+    println!("\n\nCompiled Program:\n\n{compiled}");
+    compiled
 }
 
 pub fn compile_and_run(

crates/lean_prover/tests/test_zkvm.rs

@@ -125,6 +125,6 @@ fn test_zk_vm_helper(program_str: &str, (public_input, private_input): (&[F], &[
     );
     let proof_time = time.elapsed();
     verify_execution(&bytecode, public_input, proof_data, whir_config_builder()).unwrap();
-    println!("{}", summary);
+    println!("{summary}");
     println!("Proof time: {:.3} s", proof_time.as_secs_f32());
 }

crates/lean_vm/src/diagnostics/error.rs

@@ -9,8 +9,12 @@ pub enum RunnerError {
     #[error("Out of memory")]
     OutOfMemory,
 
-    #[error("Memory already set")]
-    MemoryAlreadySet,
+    #[error("Memory already set: m[{address}] = {prev_value} != {new_value}")]
+    MemoryAlreadySet {
+        address: usize,
+        prev_value: F,
+        new_value: F,
+    },
 
     #[error("Not a pointer")]
     NotAPointer,

crates/lean_vm/src/execution/memory.rs

@@ -41,7 +41,11 @@ impl Memory {
         }
         if let Some(existing) = &mut self.0[index] {
             if *existing != value {
-                return Err(RunnerError::MemoryAlreadySet);
+                return Err(RunnerError::MemoryAlreadySet {
+                    address: index,
+                    prev_value: *existing,
+                    new_value: value,
+                });
             }
         } else {
             self.0[index] = Some(value);

crates/lean_vm/src/execution/tests.rs

@@ -25,7 +25,14 @@ fn test_memory_already_set_error() {
     memory.set(0, F::ONE).unwrap();
 
     // Setting different value should fail
-    assert!(matches!(memory.set(0, F::ZERO), Err(RunnerError::MemoryAlreadySet)));
+    assert!(matches!(
+        memory.set(0, F::ZERO),
+        Err(RunnerError::MemoryAlreadySet {
+            address: 0,
+            prev_value: F::ONE,
+            new_value: F::ZERO,
+        })
+    ));
 }
 
 #[test]