Add annotate_snippets for better parsing errors (#477)

Adds nicer errors for Podlang code, using the `annotate_snippets` crate, the same crate used by the Rust compiler to generate contextual errors. This prints a short snippet of the code containing the error within the error message, highlighting the part that needs to be fixed.

It also includes a change to the `load_module` function, changing a `Vec` function argument to a slice.

Author: robknight

Cargo.toml

@@ -42,6 +42,7 @@ serde_arrays = "0.2.0"
 sha2 = { version = "0.10.9" }
 rand_chacha = "0.3.1"
 good_lp = { version = "1.8", default-features = false, features = ["microlp"] }
+annotate-snippets = "0.11"
 
 # Uncomment for debugging with https://github.com/ed255/plonky2/ at branch `feat/debug`.  The repo directory needs to be checked out next to the pod2 repo directory.
 # [patch."https://github.com/0xPARC/plonky2"]

examples/main_pod_points.rs

@@ -88,7 +88,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         game_pk = game_pk,
     );
     println!("# custom predicate batch:{}", input);
-    let module = load_module(&input, "points_module", &params, vec![])?;
+    let module = load_module(&input, "points_module", &params, &[])?;
     let batch = module.batch.clone();
     let points_pred = batch.predicate_ref_by_name("points").unwrap();
     let over_9000_pred = batch.predicate_ref_by_name("over_9000").unwrap();

src/backends/plonky2/mainpod/mod.rs

@@ -1175,7 +1175,7 @@ pub mod tests {
             "#,
             "test",
             &params,
-            vec![],
+            &[],
         )
         .unwrap();
         let batch = module.batch.clone();

src/examples/custom.rs

@@ -30,7 +30,7 @@ pub fn eth_dos_batch(params: &Params) -> Result<Arc<CustomPredicateBatch>> {
             eth_dos_ind(src, dst, distance)
         )
         "#;
-    let module = load_module(input, "eth_dos", params, vec![]).expect("lang parse");
+    let module = load_module(input, "eth_dos", params, &[]).expect("lang parse");
     let batch = module.batch.clone();
     println!("a.0. {}", batch.predicates()[0]);
     println!("a.1. {}", batch.predicates()[1]);

src/frontend/mod.rs

@@ -1381,7 +1381,7 @@ pub mod tests {
             Equal(b, 5)
         )
         "#;
-        let module = load_module(input, "test", &params, vec![]).unwrap();
+        let module = load_module(input, "test", &params, &[]).unwrap();
         let batch = module.batch.clone();
         let pred_test = batch.predicate_ref_by_name("Test").unwrap();
 
@@ -1430,7 +1430,7 @@ pub mod tests {
             c(6, 3)
         )
         "#;
-        let module = load_module(input, "test", &params, vec![]).unwrap();
+        let module = load_module(input, "test", &params, &[]).unwrap();
         let batch = module.batch.clone();
         let pred_test = batch.predicate_ref_by_name("Test").unwrap();
 
@@ -1452,7 +1452,7 @@ pub mod tests {
             c(6, 3)
         )
         "#;
-        let module = load_module(input, "test", &params, vec![]).unwrap();
+        let module = load_module(input, "test", &params, &[]).unwrap();
         let batch = module.batch.clone();
         let pred_test = batch.predicate_ref_by_name("Test").unwrap();
 
@@ -1491,7 +1491,7 @@ pub mod tests {
         "#;
 
         // Parse and batch the predicate (this handles splitting internally)
-        let module = load_module(input, "test", &params, vec![])?;
+        let module = load_module(input, "test", &params, &[])?;
 
         // Verify it was split
         assert!(module.split_chains.contains_key("large_pred"));

src/frontend/multi_pod/mod.rs

@@ -763,7 +763,7 @@ mod tests {
             "#,
             "test",
             &params,
-            vec![],
+            &[],
         )
         .expect("load module");
         let batch = &module.batch;
@@ -1492,7 +1492,7 @@ mod tests {
             "#,
             "test",
             &params,
-            vec![],
+            &[],
         )
         .expect("load module");
         let batch = &module.batch;
@@ -1621,7 +1621,7 @@ mod tests {
             "#,
             "test",
             &params,
-            vec![],
+            &[],
         )
         .expect("load module");
         let batch = &module.batch;