feat: Bring back restriction on printing slices and add one on mutabl…

…e refs

Even though the printing support is there, neither of them can be passed from
ACIR into Brillig. So the restriction is for consistency and to be able to
provide a better error message to users.

compiler/noirc_frontend/src/monomorphization/mod.rs

@@ -1029,6 +1029,16 @@ impl<'interner> Monomorphizer<'interner> {
     }
 
     fn append_printable_type_info_inner(typ: &Type, arguments: &mut Vec<ast::Expression>) {
+        // Disallow printing slices and mutable references for consistency,
+        // since they cannot be passed from ACIR into Brillig
+        if let HirType::Array(size, _) = typ {
+            if let HirType::NotConstant = **size {
+                unreachable!("println does not support slices. Convert the slice to an array before passing it to println");
+            }
+        } else if matches!(typ, HirType::MutableReference(_)) {
+            unreachable!("println does not support mutable references.");
+        }
+
         let printable_type: PrintableType = typ.into();
         let abi_as_string = serde_json::to_string(&printable_type)
             .expect("ICE: expected PrintableType to serialize");

test_programs/execution_success/debug_logs/src/main.nr

@@ -59,8 +59,6 @@ fn main(x: Field, y: pub Field) {
     let closured_lambda = |x| x + one;
     std::println(f"closured_lambda: {closured_lambda}, sentinel: {sentinel}");
     std::println(closured_lambda);
-
-    types_printable_in_brillig_only();
 }
 
 fn string_identity(string: fmtstr<14, (Field, Field)>) -> fmtstr<14, (Field, Field)> {
@@ -101,21 +99,3 @@ fn regression_2906() {
     dep::std::println(f"array_five_vals: {array_five_vals}, label_five_vals: {label_five_vals}");
 }
 
-unconstrained fn types_printable_in_brillig_only() {
-    let mut a_tuple = (1,2,3);
-    let mut tuple_mut_ref = &mut a_tuple;
-    let sentinel: u32 = 8888;
-    std::println(f"tuple_mut_ref: {tuple_mut_ref}, sentinel: {sentinel}");
-    std::println(tuple_mut_ref);
-
-    let mut a_vector: Vec<Field> = Vec::new();
-    a_vector.push(10);
-    a_vector.push(20);
-    a_vector.push(30);
-    std::println(f"a_vector: {a_vector}, sentinel: {sentinel}");
-    std::println(a_vector);
-
-    let vec_slice = a_vector.slice;
-    std::println(f"vec_slice: {vec_slice}, sentinel: {sentinel}");
-    std::println(vec_slice);
-}