feat(acir): Handle dynamic array operations for nested slices (#3187)

Co-authored-by: Tom French <tom@tomfren.ch>
Co-authored-by: Tom French <15848336+TomAFrench@users.noreply.github.com>
Co-authored-by: jfecher <jake@aztecprotocol.com>

compiler/noirc_evaluator/src/ssa/ir/types.rs

@@ -79,6 +79,18 @@ impl Type {
         }
     }
 
+    pub(crate) fn contains_slice_element(&self) -> bool {
+        match self {
+            Type::Array(elements, _) => {
+                elements.iter().any(|element| element.contains_slice_element())
+            }
+            Type::Slice(_) => true,
+            Type::Numeric(_) => false,
+            Type::Reference => false,
+            Type::Function => false,
+        }
+    }
+
     /// Returns the flattened size of a Type
     pub(crate) fn flattened_size(&self) -> usize {
         let mut size = 0;

compiler/noirc_evaluator/src/ssa/opt/flatten_cfg/value_merger.rs

@@ -194,15 +194,16 @@ impl<'a> ValueMerger<'a> {
 
         for i in 0..len {
             for (element_index, element_type) in element_types.iter().enumerate() {
-                let index_value = ((i * element_types.len() + element_index) as u128).into();
+                let index_usize = i * element_types.len() + element_index;
+                let index_value = (index_usize as u128).into();
                 let index = self.dfg.make_constant(index_value, Type::field());
 
                 let typevars = Some(vec![element_type.clone()]);
 
                 let mut get_element = |array, typevars, len| {
                     // The smaller slice is filled with placeholder data. Codegen for slice accesses must
                     // include checks against the dynamic slice length so that this placeholder data is not incorrectly accessed.
-                    if len <= index_value.to_u128() as usize {
+                    if len <= index_usize {
                         self.make_slice_dummy_data(element_type)
                     } else {
                         let get = Instruction::ArrayGet { array, index };
@@ -239,6 +240,11 @@ impl<'a> ValueMerger<'a> {
             Value::Instruction { instruction: instruction_id, .. } => {
                 let instruction = &self.dfg[*instruction_id];
                 match instruction {
+                    // TODO(#3188): A slice can be the result of an ArrayGet when it is the
+                    // fetched from a slice of slices or as a struct field.
+                    // However, we need to incorporate nested slice support in flattening
+                    // in order for this to be valid
+                    // Instruction::ArrayGet { array, .. } => {}
                     Instruction::ArraySet { array, .. } => {
                         let array = *array;
                         let len = self.get_slice_length(array);
@@ -323,7 +329,9 @@ impl<'a> ValueMerger<'a> {
                 self.dfg.make_array(array, typ.clone())
             }
             Type::Slice(_) => {
-                unreachable!("ICE: Slices of slice is unsupported")
+                // TODO(#3188): Need to update flattening to use true user facing length of slices
+                // to accurately construct dummy data
+                unreachable!("ICE: Cannot return a slice of slices from an if expression")
             }
             Type::Reference => {
                 unreachable!("ICE: Merging references is unsupported")

tooling/nargo_cli/tests/execution_success/nested_array_dynamic/src/main.nr

@@ -30,7 +30,7 @@ fn main(mut x : [Foo; 4], y : pub Field) {
     } else {
         x[y].a = 100;
     }
-    assert(x[y].a == 50);
+    assert(x[3].a == 50);
 
     if y == 2 {
         x[y - 1].b = [50, 51, 52];

tooling/nargo_cli/tests/execution_success/regression_mem_op_predicate/src/main.nr

@@ -1,8 +1,8 @@
 fn main(mut x: [u32; 5], idx: Field) {
   // We should not hit out of bounds here as we have a predicate
   // that should not be hit
-    if idx as u32 < 3 {
+  if idx as u32 < 3 {
     x[idx] = 10;
-    }
-    assert(x[4] == 111);
+  }
+  assert(x[4] == 111);
 }

tooling/nargo_cli/tests/execution_success/slice_struct_field/Nargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "slice_struct_field"
+type = "bin"
+authors = [""]
+
+[dependencies]

tooling/nargo_cli/tests/execution_success/slice_struct_field/Prover.toml

@@ -0,0 +1 @@
+y = "3"

tooling/nargo_cli/tests/execution_success/slice_struct_field/src/main.nr

@@ -0,0 +1,125 @@
+struct FooParent {
+    parent_arr: [Field; 3],
+    foos: [Foo],
+}
+
+struct Bar {
+    inner: [Field; 3],
+}
+
+struct Foo {
+    a: Field,
+    b: [Field],
+    bar: Bar,
+}
+
+fn main(y : pub Field) {
+    let mut b_one = [2, 3, 20];
+    b_one = b_one.push_back(20);
+    // let b_one = Vec::from_slice([2, 3, 20]);
+    let foo_one = Foo { a: 1, b: b_one, bar: Bar { inner: [100, 101, 102] } };
+    let mut b_two = [5, 6, 21];
+    b_two = b_two.push_back(21);
+    // let b_two = Vec::from_slice([5, 6, 21]);
+    let foo_two = Foo { a: 4, b: b_two, bar: Bar { inner: [103, 104, 105] } };
+    let foo_three = Foo { a: 7, b: [8, 9, 22], bar: Bar { inner: [106, 107, 108] } };
+    let foo_four = Foo { a: 10, b: [11, 12, 23], bar: Bar { inner: [109, 110, 111] } };
+
+    let mut x = [foo_one, foo_two];
+    x = x.push_back(foo_three);
+    x = x.push_back(foo_four);
+
+    assert(x[y - 3].a == 1);
+    let struct_slice = x[y - 3].b;
+    for i in 0..4 {
+        assert(struct_slice[i] == b_one[i]);
+    }
+
+    assert(x[y - 2].a == 4);
+    let struct_slice = x[y - 2].b;
+    for i in 0..4 {
+        assert(struct_slice[i] == b_two[i]);
+    }
+
+    assert(x[y - 1].a == 7);
+    let struct_slice = x[y - 1].b;
+    assert(struct_slice[0] == 8);
+    assert(struct_slice[1] == 9);
+    assert(struct_slice[2] == 22);
+
+    assert(x[y].a == 10);
+    let struct_slice = x[y].b;
+    assert(struct_slice[0] == 11);
+    assert(struct_slice[1] == 12);
+    assert(struct_slice[2] == 23);
+    assert(x[y].bar.inner == [109, 110, 111]);
+
+    // TODO: Enable merging nested slices 
+    // if y != 2 {
+    //     x[y].a = 50;
+    // } else {
+    //     x[y].a = 100;
+    // }
+    // assert(x[3].a == 50);
+
+    // if y == 2 {
+    //     x[y - 1].b = [50, 51, 52];
+    // } else {
+    //     x[y - 1].b = [100, 101, 102];
+    // }
+    // assert(x[2].b[0] == 100);
+    // assert(x[2].b[1] == 101);
+    // assert(x[2].b[2] == 102);
+
+    assert(x[y - 3].bar.inner == [100, 101, 102]);
+    assert(x[y - 2].bar.inner == [103, 104, 105]);
+    assert(x[y - 1].bar.inner == [106, 107, 108]);
+    assert(x[y].bar.inner == [109, 110, 111]);
+
+    let q = x.push_back(foo_four);
+    let foo_parent_one = FooParent { parent_arr: [0, 1, 2], foos: x };
+    let foo_parent_two = FooParent { parent_arr: [3, 4, 5], foos: q };
+    let mut foo_parents = [foo_parent_one];
+    foo_parents = foo_parents.push_back(foo_parent_two);
+
+    // TODO: Merging nested slices is broken
+    // if y == 2 {
+    //     foo_parents[y - 2].foos[y - 1].b[y - 1] = 5000;
+    // } else {
+    //     foo_parents[y - 2].foos[y - 1].b[y - 1] = 1000;
+    // }
+    assert(foo_parents[y - 2].foos[y - 1].a == 7);
+    foo_parents[y - 2].foos[y - 1].a = 50;
+    assert(foo_parents[y - 2].foos[y - 1].a == 50);
+
+    assert(foo_parents[y - 2].foos[y - 2].b[y - 1] == 21);
+    foo_parents[y - 2].foos[y - 2].b[y - 1] = 5000;
+    assert(foo_parents[y - 2].foos[y - 2].b[y - 1] == 5000);
+
+    let b_array = foo_parents[y - 2].foos[y - 3].b;
+    assert(b_array[0] == 2);
+    assert(b_array[1] == 3);
+    assert(b_array[2] == 20);
+    assert(b_array[3] == 20);
+
+    let b_array = foo_parents[y - 2].foos[y - 2].b;
+    assert(b_array[0] == 5);
+    assert(b_array[1] == 6);
+    assert(b_array[2] == 5000);
+    assert(b_array[3] == 21);
+
+    let b_array = foo_parents[y - 2].foos[y - 1].b;
+    assert(b_array[0] == 8);
+    assert(b_array[1] == 9);
+    assert(b_array[2] == 22);
+
+    // Fixed by #3410
+    // let b_array = foo_parents[y - 2].foos[y].b;
+    // assert(b_array[0] == 11);
+    // assert(b_array[1] == 12);
+    // assert(b_array[2] == 23);
+
+    // assert(foo_parents[y - 2].foos[y - 3].bar.inner == [100, 101, 102]);
+    // assert(foo_parents[y - 2].foos[y - 2].bar.inner == [103, 104, 105]);
+    // assert(foo_parents[y - 2].foos[y - 1].bar.inner == [106, 107, 108]);
+}