fix cargo lock

Cargo.lock

@@ -1824,12 +1824,12 @@ checksum = "624a8340c38c1b80fd549087862da4ba43e08858af025b236e509b6649fc13d5"
 
 [[package]]
 name = "openssl"
-version = "0.10.30"
+version = "0.10.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8d575eff3665419f9b83678ff2815858ad9d11567e082f5ac1814baba4e2bcb4"
+checksum = "8d008f51b1acffa0d3450a68606e6a51c123012edaacb0f4e1426bd978869187"
 dependencies = [
  "bitflags",
- "cfg-if 0.1.10",
+ "cfg-if 1.0.0",
  "foreign-types",
  "lazy_static",
  "libc",
@@ -3119,9 +3119,9 @@ dependencies = [
 
 [[package]]
 name = "vcpkg"
-version = "0.2.10"
+version = "0.2.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6454029bf181f092ad1b853286f23e2c507d8e8194d01d92da4a55c274a5508c"
+checksum = "b00bca6106a5e23f3eee943593759b7fcddb00554332e856d990c893966879fb"
 
 [[package]]
 name = "vec_map"

compiler/src/statement/assign/assignee.rs

@@ -34,7 +34,13 @@ impl<F: Field + PrimeField, G: GroupType<F>> ConstrainedProgram<F, G> {
         // Check that assignee exists and is mutable
         Ok(match self.get_mut(name) {
             Some(value) => match value {
-                ConstrainedValue::Mutable(mutable_value) => mutable_value,
+                ConstrainedValue::Mutable(mutable_value) => {
+                    // Get the mutable value.
+                    mutable_value.get_inner_mut();
+
+                    // Return the mutable value.
+                    mutable_value
+                }
                 _ => return Err(StatementError::immutable_assign(name.to_owned(), span.to_owned())),
             },
             None => return Err(StatementError::undefined_variable(name.to_owned(), span.to_owned())),

compiler/tests/mutability/mod.rs

@@ -136,3 +136,11 @@ fn test_function_input_mut() {
 
     assert_satisfied(program);
 }
+
+#[test]
+fn test_swap() {
+    let program_string = include_str!("swap.leo");
+    let program = parse_program(program_string).unwrap();
+
+    assert_satisfied(program);
+}

compiler/tests/mutability/swap.leo

@@ -0,0 +1,20 @@
+// Swap two elements of an array.
+function swap(mut a: [u32; 2], i: u32, j: u32) -> [u32; 2] {
+    let t = a[i];
+    a[i] = a[j];
+    a[j] = t;
+    return a
+}
+
+function main() {
+    let mut arr: [u32; 2] = [0, 1];
+    let expected: [u32; 2] = [1, 0];
+
+    // Do swap.
+    let actual = swap(arr, 0, 1);
+
+    // Check result.
+    for i in 0..2 {
+        console.assert(expected[i] == actual[i]);
+    }
+}

grammar/src/leo.pest

@@ -444,8 +444,8 @@ input_tuple = _{ "(" ~ NEWLINE* ~ (input ~ ("," ~ NEWLINE* ~ input)* ~ ","?)? ~
 // Declared in imports/import.rs
 import = { "import " ~ package ~ LINE_END}
 
-
-package_name = @{ ((ASCII_ALPHA_LOWER | ASCII_DIGIT) ~ ( "-" ~ (ASCII_ALPHA_LOWER | ASCII_DIGIT))*)+ }
+// Declared in imports/package_name.rs
+package_name = @{ (ASCII_ALPHA_LOWER | ASCII_DIGIT)+ ~ ( "-" ~ (ASCII_ALPHA_LOWER | ASCII_DIGIT)+)* }
 
 // Declared in imports/package.rs
 package = { package_name ~ "." ~ package_access }