fix: Implement slices of structs (#2150)

* Implement slices of structs

* Add missed function call

* Use element_size in element_size

crates/nargo_cli/tests/test_data/slices/src/main.nr

@@ -42,5 +42,39 @@ fn main(x : Field, y : pub Field) {
     assert(removed_elem == 2);
     assert(remove_slice[3] == 3);
     assert(remove_slice.len() == 4);
+
+    regression_2083();
 }
 
+// Ensure that slices of struct/tuple values work.
+fn regression_2083() {
+    let y = [(1, 2)];
+    let y = y.push_back((3, 4)); // [(1, 2), (3, 4)]
+    let y = y.push_back((5, 6)); // [(1, 2), (3, 4), (5, 6)]
+    assert(y[2].1 == 6);
+
+    let y = y.push_front((10, 11)); // [(10, 11), (1, 2), (3, 4), (5, 6)]
+    let y = y.push_front((12, 13)); // [(12, 13), (10, 11), (1, 2), (3, 4), (5, 6)]
+
+    assert(y[1].0 == 10);
+
+    let y = y.insert(1, (55, 56)); // [(12, 13), (55, 56), (10, 11), (1, 2), (3, 4), (5, 6)]
+    assert(y[0].1 == 13);
+    assert(y[1].1 == 56);
+    assert(y[2].0 == 10);
+
+    let (y, x) = y.remove(2); // [(12, 13), (55, 56), (1, 2), (3, 4), (5, 6)]
+    assert(y[2].0 == 1);
+    assert(x.0 == 10);
+    assert(x.1 == 11);
+
+    let (x, y) = y.pop_front(); // [(55, 56), (1, 2), (3, 4), (5, 6)]
+    assert(y[0].0 == 55);
+    assert(x.0 == 12);
+    assert(x.1 == 13);
+
+    let (y, x) = y.pop_back(); // [(55, 56), (1, 2), (3, 4)]
+    assert(y.len() == 3);
+    assert(x.0 == 5);
+    assert(x.1 == 6);
+}

crates/noirc_evaluator/src/ssa/ir/dfg.rs

@@ -369,7 +369,7 @@ impl DataFlowGraph {
     /// Otherwise, this returns None.
     pub(crate) fn get_array_constant(&self, value: ValueId) -> Option<(im::Vector<ValueId>, Type)> {
         match &self.values[self.resolve(value)] {
-            // Vectors are shared, so cloning them is cheap
+            // Arrays are shared, so cloning them is cheap
             Value::Array { array, typ } => Some((array.clone(), typ.clone())),
             _ => None,
         }

crates/noirc_evaluator/src/ssa/ir/instruction/call.rs

@@ -1,4 +1,4 @@
-use std::rc::Rc;
+use std::{collections::VecDeque, rc::Rc};
 
 use acvm::{acir::BlackBoxFunc, BlackBoxResolutionError, FieldElement};
 use iter_extended::vecmap;
@@ -53,22 +53,22 @@ pub(super) fn simplify_call(
         }
         Intrinsic::ArrayLen => {
             let slice = dfg.get_array_constant(arguments[0]);
-            if let Some((slice, _)) = slice {
-                SimplifyResult::SimplifiedTo(
-                    dfg.make_constant((slice.len() as u128).into(), Type::field()),
-                )
+            if let Some((slice, typ)) = slice {
+                let length = FieldElement::from((slice.len() / typ.element_size()) as u128);
+                SimplifyResult::SimplifiedTo(dfg.make_constant(length, Type::field()))
             } else if let Some(length) = dfg.try_get_array_length(arguments[0]) {
-                SimplifyResult::SimplifiedTo(
-                    dfg.make_constant((length as u128).into(), Type::field()),
-                )
+                let length = FieldElement::from(length as u128);
+                SimplifyResult::SimplifiedTo(dfg.make_constant(length, Type::field()))
             } else {
                 SimplifyResult::None
             }
         }
         Intrinsic::SlicePushBack => {
             let slice = dfg.get_array_constant(arguments[0]);
-            if let (Some((mut slice, element_type)), elem) = (slice, arguments[1]) {
-                slice.push_back(elem);
+            if let Some((mut slice, element_type)) = slice {
+                for elem in &arguments[1..] {
+                    slice.push_back(*elem);
+                }
                 let new_slice = dfg.make_array(slice, element_type);
                 SimplifyResult::SimplifiedTo(new_slice)
             } else {
@@ -77,8 +77,10 @@ pub(super) fn simplify_call(
         }
         Intrinsic::SlicePushFront => {
             let slice = dfg.get_array_constant(arguments[0]);
-            if let (Some((mut slice, element_type)), elem) = (slice, arguments[1]) {
-                slice.push_front(elem);
+            if let Some((mut slice, element_type)) = slice {
+                for elem in arguments[1..].iter().rev() {
+                    slice.push_front(*elem);
+                }
                 let new_slice = dfg.make_array(slice, element_type);
                 SimplifyResult::SimplifiedTo(new_slice)
             } else {
@@ -87,34 +89,58 @@ pub(super) fn simplify_call(
         }
         Intrinsic::SlicePopBack => {
             let slice = dfg.get_array_constant(arguments[0]);
-            if let Some((mut slice, element_type)) = slice {
-                let elem =
-                    slice.pop_back().expect("There are no elements in this slice to be removed");
-                let new_slice = dfg.make_array(slice, element_type);
-                SimplifyResult::SimplifiedToMultiple(vec![new_slice, elem])
+            if let Some((mut slice, typ)) = slice {
+                let element_count = typ.element_size();
+                let mut results = VecDeque::with_capacity(element_count + 1);
+
+                // We must pop multiple elements in the case of a slice of tuples
+                for _ in 0..element_count {
+                    let elem = slice
+                        .pop_back()
+                        .expect("There are no elements in this slice to be removed");
+                    results.push_front(elem);
+                }
+
+                let new_slice = dfg.make_array(slice, typ);
+                results.push_front(new_slice);
+
+                SimplifyResult::SimplifiedToMultiple(results.into())
             } else {
                 SimplifyResult::None
             }
         }
         Intrinsic::SlicePopFront => {
             let slice = dfg.get_array_constant(arguments[0]);
-            if let Some((mut slice, element_type)) = slice {
-                let elem =
-                    slice.pop_front().expect("There are no elements in this slice to be removed");
-                let new_slice = dfg.make_array(slice, element_type);
-                SimplifyResult::SimplifiedToMultiple(vec![elem, new_slice])
+            if let Some((mut slice, typ)) = slice {
+                let element_count = typ.element_size();
+
+                // We must pop multiple elements in the case of a slice of tuples
+                let mut results = vecmap(0..element_count, |_| {
+                    slice.pop_front().expect("There are no elements in this slice to be removed")
+                });
+
+                let new_slice = dfg.make_array(slice, typ);
+
+                // The slice is the last item returned for pop_front
+                results.push(new_slice);
+                SimplifyResult::SimplifiedToMultiple(results)
             } else {
                 SimplifyResult::None
             }
         }
         Intrinsic::SliceInsert => {
             let slice = dfg.get_array_constant(arguments[0]);
             let index = dfg.get_numeric_constant(arguments[1]);
-            if let (Some((mut slice, element_type)), Some(index), value) =
-                (slice, index, arguments[2])
-            {
-                slice.insert(index.to_u128() as usize, value);
-                let new_slice = dfg.make_array(slice, element_type);
+            if let (Some((mut slice, typ)), Some(index)) = (slice, index) {
+                let elements = &arguments[2..];
+                let mut index = index.to_u128() as usize * elements.len();
+
+                for elem in &arguments[2..] {
+                    slice.insert(index, *elem);
+                    index += 1;
+                }
+
+                let new_slice = dfg.make_array(slice, typ);
                 SimplifyResult::SimplifiedTo(new_slice)
             } else {
                 SimplifyResult::None
@@ -123,10 +149,18 @@ pub(super) fn simplify_call(
         Intrinsic::SliceRemove => {
             let slice = dfg.get_array_constant(arguments[0]);
             let index = dfg.get_numeric_constant(arguments[1]);
-            if let (Some((mut slice, element_type)), Some(index)) = (slice, index) {
-                let removed_elem = slice.remove(index.to_u128() as usize);
-                let new_slice = dfg.make_array(slice, element_type);
-                SimplifyResult::SimplifiedToMultiple(vec![new_slice, removed_elem])
+            if let (Some((mut slice, typ)), Some(index)) = (slice, index) {
+                let element_count = typ.element_size();
+                let mut results = Vec::with_capacity(element_count + 1);
+                let index = index.to_u128() as usize * element_count;
+
+                for _ in 0..element_count {
+                    results.push(slice.remove(index));
+                }
+
+                let new_slice = dfg.make_array(slice, typ);
+                results.insert(0, new_slice);
+                SimplifyResult::SimplifiedToMultiple(results)
             } else {
                 SimplifyResult::None
             }

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

@@ -61,6 +61,17 @@ impl Type {
     pub(crate) fn field() -> Type {
         Type::Numeric(NumericType::NativeField)
     }
+
+    /// Returns the size of the element type for this array/slice.
+    /// The size of a type is defined as representing how many Fields are needed
+    /// to represent the type. This is 1 for every primitive type, and is the number of fields
+    /// for any flattened tuple type.
+    pub(crate) fn element_size(&self) -> usize {
+        match self {
+            Type::Array(elements, _) | Type::Slice(elements) => elements.len(),
+            other => panic!("element_size: Expected array or slice, found {other}"),
+        }
+    }
 }
 
 /// Composite Types are essentially flattened struct or tuple types.

crates/noirc_evaluator/src/ssa/ssa_gen/context.rs

@@ -641,10 +641,8 @@ impl<'a> FunctionContext<'a> {
     }
 
     fn element_size(&self, array: ValueId) -> FieldElement {
-        match self.builder.type_of_value(array) {
-            Type::Array(elements, _) | Type::Slice(elements) => (elements.len() as u128).into(),
-            t => panic!("Uncaught type error: tried to take element size of non-array type {t}"),
-        }
+        let size = self.builder.type_of_value(array).element_size();
+        FieldElement::from(size as u128)
     }
 
     /// Given an lhs containing only references, create a store instruction to store each value of