fix: Require for all foldable functions to use distinct return

compiler/noirc_evaluator/src/ssa/acir_gen/mod.rs

@@ -282,7 +282,7 @@
         brillig: &Brillig,
     ) -> Result<(Vec<GeneratedAcir>, Vec<BrilligBytecode>), RuntimeError> {
         let mut acirs = Vec::new();
         // TODO: can we parallelise this?
         let mut shared_context = SharedContext::default();
         for function in self.functions.values() {
             let context = Context::new(&mut shared_context);
@@ -327,13 +327,9 @@
             bytecode: brillig.byte_code,
         });
 
-        // TODO: check whether doing this for a single circuit's return witnesses is correct.
-        // We probably need it for all foldable circuits, as any circuit being folded is essentially an entry point. However, I do not know how that
-        // plays a part when we potentially want not inlined functions normally as part of the compiler.
-        // Also at the moment we specify Distinctness as part of the ABI exclusively rather than the function itself
-        // so this will need to be updated.
-        let main_func_acir = &mut acirs[0];
-        generate_distinct_return_witnesses(main_func_acir);
+        for acir in acirs.iter_mut() {
+            generate_distinct_return_witnesses(acir);
+        }
 
         Ok((acirs, brillig))
     }
@@ -2664,9 +2660,9 @@
     #[test]
     #[should_panic]
     fn basic_calls_no_predicates() {
+        basic_call_with_outputs_assert(InlineType::NoPredicates);
         call_output_as_next_call_input(InlineType::NoPredicates);
         basic_nested_call(InlineType::NoPredicates);
-        basic_call_with_outputs_assert(InlineType::NoPredicates);
     }
 
     #[test]
@@ -2909,9 +2905,10 @@
 
         let func_with_nested_call_acir = &acir_functions[1];
         let func_with_nested_call_opcodes = func_with_nested_call_acir.opcodes();
+
         assert_eq!(
             func_with_nested_call_opcodes.len(),
-            2,
+            3,
             "Should have an expression and a call to a nested `foo`"
         );
         // Should call foo f2

test_programs/execution_success/fold_distinct_return/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "fold_distinct_return"
+type = "bin"
+authors = [""]
+compiler_version = ">=0.28.0"
+
+[dependencies]

test_programs/execution_success/fold_distinct_return/Prover.toml

@@ -0,0 +1,2 @@
+x = "5"
+y = "10"

test_programs/execution_success/fold_distinct_return/src/main.nr

@@ -0,0 +1,10 @@
+fn main(x: u32, y: pub u32) {
+    let new_field = new_field_in_array([x, y, 3]);
+    assert(new_field[0] == 25);
+}
+
+#[fold]
+fn new_field_in_array(mut input: [u32; 3]) -> [u32; 3] {
+    input[0] = input[0] + 20;
+    input
+}

tooling/debugger/ignored-tests.txt

@@ -20,4 +20,5 @@ fold_numeric_generic_poseidon
 no_predicates_basic
 no_predicates_numeric_generic_poseidon
 regression_4709
+fold_distinct_return
 fold_fibonacci