feat: add set and set_unchecked methods to Vec and BoundedVec (…

…noir-lang#5241)

# Description

## Problem\*

Resolves <!-- Link to GitHub Issue -->

## Summary\*

This PR exposes `set` and `set_unchecked` methods to `BoundedVec` which
allow writing to individual indices in the array without having to
access `self.storage` directly.

I've also documented the expected behaviour for the get and set
operations.


## Additional Context



## Documentation\*

Check one:
- [ ] No documentation needed.
- [x] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

docs/docs/noir/standard_library/containers/boundedvec.md

@@ -59,7 +59,7 @@ but for now make sure to use type annotations when using bounded vectors. Otherw
 ### get
 
 ```rust
-pub fn get(mut self: Self, index: u64) -> T {
+pub fn get(self, index: u64) -> T {
 ```
 
 Retrieves an element from the vector at the given index, starting from zero.
@@ -80,7 +80,7 @@ fn foo<N>(v: BoundedVec<u32, N>) {
 ### get_unchecked
 
 ```rust
-pub fn get_unchecked(mut self: Self, index: u64) -> T {
+pub fn get_unchecked(self, index: u64) -> T {
 ```
 
 Retrieves an element from the vector at the given index, starting from zero, without
@@ -93,6 +93,42 @@ Example:
 
 #include_code get_unchecked_example test_programs/noir_test_success/bounded_vec/src/main.nr rust
 
+### set
+
+```rust
+pub fn set(&mut self: Self, index: u64, value: T) {
+```
+
+Writes an element to the vector at the given index, starting from zero.
+
+If the given index is equal to or greater than the length of the vector, this will issue a constraint failure.
+
+Example:
+
+```rust
+fn foo<N>(v: BoundedVec<u32, N>) {
+    let first = v.get(0);
+    assert(first != 42);
+    v.set(0, 42);
+    let new_first = v.get(0);
+    assert(new_first == 42);
+}
+```
+
+### set_unchecked
+
+```rust
+pub fn set_unchecked(&mut self: Self, index: u64, value: T) -> T {
+```
+
+Writes an element to the vector at the given index, starting from zero, without performing a bounds check.
+
+Since this function does not perform a bounds check on length before accessing the element, it is unsafe! Use at your own risk!
+
+Example:
+
+#include_code set_unchecked_example test_programs/noir_test_success/bounded_vec/src/main.nr rust
+
 
 ### push
 

docs/docs/noir/standard_library/containers/vec.mdx

@@ -84,6 +84,25 @@ let vector: Vec<Field> = Vec::from_slice(&[10, 20, 30]);
 assert(vector.get(1) == 20);
 ```
 
+### set
+
+```rust
+pub fn set(&mut self: Self, index: u64, value: T) {
+```
+
+Writes an element to the vector at the given index, starting from zero.
+
+Panics if the index points beyond the vector's end.
+
+Example:
+
+```rust
+let vector: Vec<Field> = Vec::from_slice(&[10, 20, 30]);
+assert(vector.get(1) == 20);
+vector.set(1, 42);
+assert(vector.get(1) == 42);
+```
+
 ### push
 
 Adds a new element to the vector's end, returning a new vector with a length one greater than the original unmodified vector.

noir_stdlib/src/collections/bounded_vec.nr

@@ -11,15 +11,35 @@ impl<T, MaxLen> BoundedVec<T, MaxLen> {
         BoundedVec { storage: [zeroed; MaxLen], len: 0 }
     }
 
-    pub fn get(mut self: Self, index: u32) -> T {
+    /// Get an element from the vector at the given index.
+    /// Panics if the given index points beyond the end of the vector (`self.len()`).
+    pub fn get(self, index: u32) -> T {
         assert(index < self.len);
-        self.storage[index]
+        self.get_unchecked(index)
     }
 
-    pub fn get_unchecked(mut self: Self, index: u32) -> T {
+    /// Get an element from the vector at the given index.
+    /// Responds with undefined data for `index` where `self.len < index < self.max_len()`.
+    pub fn get_unchecked(self, index: u32) -> T {
         self.storage[index]
     }
 
+    /// Write an element to the vector at the given index.
+    /// Panics if the given index points beyond the end of the vector (`self.len()`).
+    pub fn set(&mut self, index: u32, value: T) {
+        assert(index < self.len, "Attempted to write past end of BoundedVec");
+        self.set_unchecked(index, value)
+    }
+
+    /// Write an element to the vector at the given index.
+    /// Does not check whether the passed `index` is a valid index within the vector.
+    ///
+    /// Silently writes past the end of the vector for `index` where `self.len < index < self.max_len()`
+    /// Panics if the given index points beyond the maximum length of the vector (`self.max_len()`).
+    pub fn set_unchecked(&mut self, index: u32, value: T) {
+        self.storage[index] = value;
+    }
+
     pub fn push(&mut self, elem: T) {
         assert(self.len < MaxLen, "push out of bounds");
 
@@ -142,6 +162,39 @@ mod bounded_vec_tests {
         assert(bounded_vec1 != bounded_vec2);
     }
 
+    mod set {
+        use crate::collections::bounded_vec::BoundedVec;
+
+        #[test]
+        fn set_updates_values_properly() {
+            let mut vec = BoundedVec::from_array([0, 0, 0, 0, 0]);
+
+            vec.set(0, 42);
+            assert_eq(vec.storage, [42, 0, 0, 0, 0]);
+
+            vec.set(1, 43);
+            assert_eq(vec.storage, [42, 43, 0, 0, 0]);
+
+            vec.set(2, 44);
+            assert_eq(vec.storage, [42, 43, 44, 0, 0]);
+
+            vec.set(1, 10);
+            assert_eq(vec.storage, [42, 10, 44, 0, 0]);
+
+            vec.set(0, 0);
+            assert_eq(vec.storage, [0, 10, 44, 0, 0]);
+        }
+
+        #[test(should_fail_with = "Attempted to write past end of BoundedVec")]
+        fn panics_when_writing_elements_past_end_of_vec() {
+            let mut vec: BoundedVec<Field, 5> = BoundedVec::new();
+            vec.set(0, 42);
+
+            // Need to use println to avoid DIE removing the write operation.
+            crate::println(vec.get(0));
+        }
+    }
+
     mod from_array {
         use crate::collections::bounded_vec::BoundedVec;
 

noir_stdlib/src/collections/vec.nr

@@ -21,6 +21,12 @@ impl<T> Vec<T> {
         self.slice[index]
     }
 
+    /// Write an element to the vector at the given index.
+    /// Panics if the given index points beyond the end of the vector (`self.len()`).
+    pub fn set(&mut self, index: u32, value: T) {
+        self.slice[index] = value;
+    }
+
     /// Push a new element to the end of the vector, returning a
     /// new vector with a length one greater than the
     /// original unmodified vector.
@@ -57,3 +63,36 @@ impl<T> Vec<T> {
         self.slice.len()
     }
 }
+
+mod tests {
+    use crate::collections::vec::Vec;
+
+    #[test]
+    fn set_updates_values_properly() {
+        let mut vec = Vec { slice: &[0, 0, 0, 0, 0] };
+
+        vec.set(0, 42);
+        assert_eq(vec.slice, &[42, 0, 0, 0, 0]);
+
+        vec.set(1, 43);
+        assert_eq(vec.slice, &[42, 43, 0, 0, 0]);
+
+        vec.set(2, 44);
+        assert_eq(vec.slice, &[42, 43, 44, 0, 0]);
+
+        vec.set(1, 10);
+        assert_eq(vec.slice, &[42, 10, 44, 0, 0]);
+
+        vec.set(0, 0);
+        assert_eq(vec.slice, &[0, 10, 44, 0, 0]);
+    }
+
+    #[test(should_fail)]
+    fn panics_when_writing_elements_past_end_of_vec() {
+        let mut vec = Vec::new();
+        vec.set(0, 42);
+
+        // Need to use println to avoid DIE removing the write operation.
+        crate::println(vec.get(0));
+    }
+}

test_programs/noir_test_success/bounded_vec/src/main.nr

@@ -63,6 +63,33 @@ fn sum_of_first_three<N>(v: BoundedVec<u32, N>) -> u32 {
 }
 // docs:end:get_unchecked_example
 
+#[test(should_fail)]
+// docs:start:set_unchecked_example
+fn set_unchecked_example() {
+    let mut vec: BoundedVec<u32, 5> = BoundedVec::new();
+    vec.extend_from_array([1, 2]);
+
+    // Here we're safely writing within the valid range of `vec`
+    // `vec` now has the value [42, 2]
+    vec.set_unchecked(0, 42);
+
+    // We can then safely read this value back out of `vec`.
+    // Notice that we use the checked version of `get` which would prevent reading unsafe values.
+    assert_eq(vec.get(0), 42);
+
+    // We've now written past the end of `vec`.
+    // As this index is still within the maximum potential length of `v`,
+    // it won't cause a constraint failure. 
+    vec.set_unchecked(2, 42);
+    println(vec);
+
+    // This will write past the end of the maximum potential length of `vec`,
+    // it will then trigger a constraint failure.
+    vec.set_unchecked(5, 42);
+    println(vec);
+}
+// docs:end:set_unchecked_example
+
 #[test(should_fail_with = "push out of bounds")]
 fn push_docs_example() {
     // docs:start:bounded-vec-push-example

tooling/nargo_cli/tests/stdlib-tests.rs

@@ -1,6 +1,8 @@
+use std::io::Write;
 use std::{collections::BTreeMap, path::PathBuf};
 
 use acvm::blackbox_solver::StubbedBlackBoxSolver;
+use fm::FileManager;
 use noirc_driver::{check_crate, file_manager_with_stdlib, CompileOptions};
 use noirc_frontend::hir::FunctionNameMatch;
 
@@ -9,6 +11,7 @@ use nargo::{
     package::{Package, PackageType},
     parse_all, prepare_package,
 };
+use termcolor::{Color, ColorChoice, ColorSpec, StandardStream, WriteColor};
 
 #[test]
 fn run_stdlib_tests() {
@@ -23,7 +26,7 @@ fn run_stdlib_tests() {
         root_dir: PathBuf::from("."),
         package_type: PackageType::Binary,
         entry_path: PathBuf::from("main.nr"),
-        name: "dummy".parse().unwrap(),
+        name: "stdlib".parse().unwrap(),
         dependencies: BTreeMap::new(),
     };
 
@@ -58,5 +61,85 @@ fn run_stdlib_tests() {
         .collect();
 
     assert!(!test_report.is_empty(), "Could not find any tests within the stdlib");
+    display_test_report(&file_manager, &dummy_package, &CompileOptions::default(), &test_report);
     assert!(test_report.iter().all(|(_, status)| !status.failed()));
 }
+
+// This code is copied from `src/cli/test_cmd.rs`.
+// This should be abstracted into a proper test runner at some point.
+fn display_test_report(
+    file_manager: &FileManager,
+    package: &Package,
+    compile_options: &CompileOptions,
+    test_report: &[(String, TestStatus)],
+) {
+    let writer = StandardStream::stderr(ColorChoice::Always);
+    let mut writer = writer.lock();
+
+    for (test_name, test_status) in test_report {
+        write!(writer, "[{}] Testing {test_name}... ", package.name)
+            .expect("Failed to write to stderr");
+        writer.flush().expect("Failed to flush writer");
+
+        match &test_status {
+            TestStatus::Pass { .. } => {
+                writer
+                    .set_color(ColorSpec::new().set_fg(Some(Color::Green)))
+                    .expect("Failed to set color");
+                writeln!(writer, "ok").expect("Failed to write to stderr");
+            }
+            TestStatus::Fail { message, error_diagnostic } => {
+                writer
+                    .set_color(ColorSpec::new().set_fg(Some(Color::Red)))
+                    .expect("Failed to set color");
+                writeln!(writer, "FAIL\n{message}\n").expect("Failed to write to stderr");
+                if let Some(diag) = error_diagnostic {
+                    noirc_errors::reporter::report_all(
+                        file_manager.as_file_map(),
+                        &[diag.clone()],
+                        compile_options.deny_warnings,
+                        compile_options.silence_warnings,
+                    );
+                }
+            }
+            TestStatus::CompileError(err) => {
+                noirc_errors::reporter::report_all(
+                    file_manager.as_file_map(),
+                    &[err.clone()],
+                    compile_options.deny_warnings,
+                    compile_options.silence_warnings,
+                );
+            }
+        }
+        writer.reset().expect("Failed to reset writer");
+    }
+
+    write!(writer, "[{}] ", package.name).expect("Failed to write to stderr");
+
+    let count_all = test_report.len();
+    let count_failed = test_report.iter().filter(|(_, status)| status.failed()).count();
+    let plural = if count_all == 1 { "" } else { "s" };
+    if count_failed == 0 {
+        writer.set_color(ColorSpec::new().set_fg(Some(Color::Green))).expect("Failed to set color");
+        write!(writer, "{count_all} test{plural} passed").expect("Failed to write to stderr");
+        writer.reset().expect("Failed to reset writer");
+        writeln!(writer).expect("Failed to write to stderr");
+    } else {
+        let count_passed = count_all - count_failed;
+        let plural_failed = if count_failed == 1 { "" } else { "s" };
+        let plural_passed = if count_passed == 1 { "" } else { "s" };
+
+        if count_passed != 0 {
+            writer
+                .set_color(ColorSpec::new().set_fg(Some(Color::Green)))
+                .expect("Failed to set color");
+            write!(writer, "{count_passed} test{plural_passed} passed, ",)
+                .expect("Failed to write to stderr");
+        }
+
+        writer.set_color(ColorSpec::new().set_fg(Some(Color::Red))).expect("Failed to set color");
+        writeln!(writer, "{count_failed} test{plural_failed} failed")
+            .expect("Failed to write to stderr");
+        writer.reset().expect("Failed to reset writer");
+    }
+}