Add extra error when compile-time integer is out of bounds of array

Author: VonTum

src/instantiation/final_checks.rs

@@ -0,0 +1,53 @@
+//! After instantiation, we preform a few final checks of each module.
+
+use num::BigInt;
+
+use crate::{typing::concrete_type::ConcreteType, value::Value};
+
+use super::{InstantiationContext, RealWireDataSource, RealWirePathElem};
+impl InstantiationContext<'_, '_> {
+    fn check_array_accesses_in(&self, path: &[RealWirePathElem], mut arr_typ: &ConcreteType) {
+        for elem in path {
+            match elem {
+                RealWirePathElem::ArrayAccess { span, idx_wire } => {
+                    let ConcreteType::Array(arr) = arr_typ else {
+                        break;
+                    }; // May still contain unknowns
+                    let ConcreteType::Value(Value::Integer(arr_sz)) = &arr.1 else {
+                        break;
+                    }; // May still contain unknowns
+                    arr_typ = &arr.0;
+
+                    let idx_wire_wire = &self.wires[*idx_wire];
+                    if let RealWireDataSource::Constant { value } = &idx_wire_wire.source {
+                        // Constant access into array! We can check.
+                        let integer_value = value.unwrap_integer();
+                        if integer_value >= arr_sz || integer_value < &BigInt::ZERO {
+                            self.errors
+                                .error(span.inner_span(), format!("Index out of bounds. Array is of size {arr_sz}, but the index is {integer_value}."));
+                        }
+                    }
+                }
+            }
+        }
+    }
+    pub fn check_array_accesses(&self) {
+        for (_id, w) in &self.wires {
+            match &w.source {
+                RealWireDataSource::Select { root, path } => {
+                    let from = &self.wires[*root];
+                    self.check_array_accesses_in(path, &from.typ);
+                }
+                RealWireDataSource::Multiplexer {
+                    is_state: _,
+                    sources,
+                } => {
+                    for s in sources {
+                        self.check_array_accesses_in(&s.to_path, &w.typ);
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+}

src/instantiation/mod.rs

@@ -1,5 +1,6 @@
 mod concrete_typecheck;
 mod execute;
+mod final_checks;
 mod unique_names;
 
 use unique_names::UniqueNames;
@@ -419,5 +420,8 @@ fn perform_instantiation(
     println!("Latency Counting {}", md.link_info.name);
     context.compute_latencies();
 
+    println!("Checking array accesses {}", md.link_info.name);
+    context.check_array_accesses();
+
     context.extract()
 }