diff --git a/compiler/noirc_evaluator/src/ssa/opt/array_set.rs b/compiler/noirc_evaluator/src/ssa/opt/array_set.rs
index e7f69f87da8..865a1e31eb3 100644
--- a/compiler/noirc_evaluator/src/ssa/opt/array_set.rs
+++ b/compiler/noirc_evaluator/src/ssa/opt/array_set.rs
@@ -28,17 +28,21 @@ impl Ssa {
 
 impl Function {
     pub(crate) fn array_set_optimization(&mut self) {
+        if matches!(self.runtime(), RuntimeType::Brillig(_)) {
+            // Brillig is supposed to use refcounting to decide whether to mutate an array;
+            // array mutation was only meant for ACIR. We could use it with Brillig as well,
+            // but then some of the optimizations that we can do in ACIR around shared
+            // references have to be skipped, which makes it more cumbersome.
+            return;
+        }
+
         let reachable_blocks = self.reachable_blocks();
 
         if !self.runtime().is_entry_point() {
             assert_eq!(reachable_blocks.len(), 1, "Expected there to be 1 block remaining in Acir function for array_set optimization");
         }
 
-        let mut context = Context::new(
-            &self.dfg,
-            self.parameters(),
-            matches!(self.runtime(), RuntimeType::Brillig(_)),
-        );
+        let mut context = Context::new(&self.dfg);
 
         for block in reachable_blocks.iter() {
             context.analyze_last_uses(*block);
@@ -53,8 +57,6 @@ impl Function {
 
 struct Context<'f> {
     dfg: &'f DataFlowGraph,
-    function_parameters: &'f [ValueId],
-    is_brillig_runtime: bool,
     array_to_last_use: HashMap<ValueId, InstructionId>,
     instructions_that_can_be_made_mutable: HashSet<InstructionId>,
     // Mapping of an array that comes from a load and whether the address
@@ -64,15 +66,9 @@ struct Context<'f> {
 }
 
 impl<'f> Context<'f> {
-    fn new(
-        dfg: &'f DataFlowGraph,
-        function_parameters: &'f [ValueId],
-        is_brillig_runtime: bool,
-    ) -> Self {
+    fn new(dfg: &'f DataFlowGraph) -> Self {
         Context {
             dfg,
-            function_parameters,
-            is_brillig_runtime,
             array_to_last_use: HashMap::default(),
             instructions_that_can_be_made_mutable: HashSet::default(),
             arrays_from_load: HashMap::default(),
@@ -94,21 +90,12 @@ impl<'f> Context<'f> {
                         self.instructions_that_can_be_made_mutable.remove(&existing);
                     }
                 }
-                Instruction::ArraySet { array, value, .. } => {
+                Instruction::ArraySet { array, .. } => {
                     let array = self.dfg.resolve(*array);
 
                     if let Some(existing) = self.array_to_last_use.insert(array, *instruction_id) {
                         self.instructions_that_can_be_made_mutable.remove(&existing);
                     }
-                    if self.is_brillig_runtime {
-                        let value = self.dfg.resolve(*value);
-
-                        if let Some(existing) = self.inner_nested_arrays.get(&value) {
-                            self.instructions_that_can_be_made_mutable.remove(existing);
-                        }
-                        let result = self.dfg.instruction_results(*instruction_id)[0];
-                        self.inner_nested_arrays.insert(result, *instruction_id);
-                    }
 
                     // If the array we are setting does not come from a load we can safely mark it mutable.
                     // If the array comes from a load we may potentially being mutating an array at a reference
@@ -128,17 +115,13 @@ impl<'f> Context<'f> {
                         }
                     });
 
-                    // We cannot safely mutate slices that are inputs to the function, as they might be shared with the caller.
-                    // NB checking the block parameters is not enough, as we might have jumped into a parameterless blocks inside the function.
-                    let is_function_param = self.function_parameters.contains(&array);
-
                     let can_mutate = if let Some(is_from_param) = self.arrays_from_load.get(&array)
                     {
                         // If the array was loaded from a reference parameter, we cannot
                         // safely mark that array mutable as it may be shared by another value.
                         !is_from_param && is_return_block
                     } else {
-                        !is_array_in_terminator && !is_function_param
+                        !is_array_in_terminator
                     };
 
                     if can_mutate {
diff --git a/compiler/noirc_evaluator/src/ssa/opt/mod.rs b/compiler/noirc_evaluator/src/ssa/opt/mod.rs
index 5576b494570..098f62bceba 100644
--- a/compiler/noirc_evaluator/src/ssa/opt/mod.rs
+++ b/compiler/noirc_evaluator/src/ssa/opt/mod.rs
@@ -44,7 +44,7 @@ pub(crate) fn assert_normalized_ssa_equals(mut ssa: super::Ssa, expected: &str)
     let expected = trim_leading_whitespace_from_lines(expected);
 
     if ssa != expected {
-        println!("Got:\n~~~\n{}\n~~~\nExpected:\n~~~\n{}\n~~~", ssa, expected);
-        similar_asserts::assert_eq!(ssa, expected);
+        println!("Expected:\n~~~\n{expected}\n~~~\nGot:\n~~~\n{ssa}\n~~~");
+        similar_asserts::assert_eq!(expected, ssa);
     }
 }
diff --git a/compiler/noirc_evaluator/src/ssa/parser/tests.rs b/compiler/noirc_evaluator/src/ssa/parser/tests.rs
index 3ed6be57b5e..9205353151e 100644
--- a/compiler/noirc_evaluator/src/ssa/parser/tests.rs
+++ b/compiler/noirc_evaluator/src/ssa/parser/tests.rs
@@ -425,3 +425,14 @@ fn test_slice() {
         ";
     assert_ssa_roundtrip(src);
 }
+
+#[test]
+fn test_negative() {
+    let src = "
+        acir(inline) fn main f0 {
+          b0():
+            return Field -1
+        }
+        ";
+    assert_ssa_roundtrip(src);
+}
diff --git a/compiler/noirc_frontend/src/elaborator/comptime.rs b/compiler/noirc_frontend/src/elaborator/comptime.rs
index 279adc331ea..a27e2bf0163 100644
--- a/compiler/noirc_frontend/src/elaborator/comptime.rs
+++ b/compiler/noirc_frontend/src/elaborator/comptime.rs
@@ -452,7 +452,14 @@ impl<'context> Elaborator<'context> {
             }
             ItemKind::Impl(r#impl) => {
                 let module = self.module_id();
-                dc_mod::collect_impl(self.interner, generated_items, r#impl, self.file, module);
+                dc_mod::collect_impl(
+                    self.interner,
+                    generated_items,
+                    r#impl,
+                    self.file,
+                    module,
+                    &mut self.errors,
+                );
             }
 
             ItemKind::ModuleDecl(_)
diff --git a/compiler/noirc_frontend/src/hir/comptime/interpreter/builtin.rs b/compiler/noirc_frontend/src/hir/comptime/interpreter/builtin.rs
index 8a6c46ca50c..80c1ee217c2 100644
--- a/compiler/noirc_frontend/src/hir/comptime/interpreter/builtin.rs
+++ b/compiler/noirc_frontend/src/hir/comptime/interpreter/builtin.rs
@@ -42,7 +42,7 @@ use crate::{
 };
 
 use self::builtin_helpers::{eq_item, get_array, get_ctstring, get_str, get_u8, hash_item, lex};
-use super::Interpreter;
+use super::{foreign, Interpreter};
 
 pub(crate) mod builtin_helpers;
 
@@ -57,6 +57,7 @@ impl<'local, 'context> Interpreter<'local, 'context> {
         let interner = &mut self.elaborator.interner;
         let call_stack = &self.elaborator.interpreter_call_stack;
         match name {
+            "apply_range_constraint" => foreign::apply_range_constraint(arguments, location),
             "array_as_str_unchecked" => array_as_str_unchecked(interner, arguments, location),
             "array_len" => array_len(interner, arguments, location),
             "assert_constant" => Ok(Value::Bool(true)),
diff --git a/compiler/noirc_frontend/src/hir/comptime/interpreter/foreign.rs b/compiler/noirc_frontend/src/hir/comptime/interpreter/foreign.rs
index d1ab6a1dabd..3de72969cab 100644
--- a/compiler/noirc_frontend/src/hir/comptime/interpreter/foreign.rs
+++ b/compiler/noirc_frontend/src/hir/comptime/interpreter/foreign.rs
@@ -1,4 +1,6 @@
-use acvm::blackbox_solver::BlackBoxFunctionSolver;
+use acvm::{
+    acir::BlackBoxFunc, blackbox_solver::BlackBoxFunctionSolver, AcirField, BlackBoxResolutionError,
+};
 use bn254_blackbox_solver::Bn254BlackBoxSolver;
 use im::Vector;
 use iter_extended::try_vecmap;
@@ -29,6 +31,28 @@ pub(super) fn call_foreign(
     }
 }
 
+pub(super) fn apply_range_constraint(
+    arguments: Vec<(Value, Location)>,
+    location: Location,
+) -> IResult<Value> {
+    let (value, num_bits) = check_two_arguments(arguments, location)?;
+
+    let input = get_field(value)?;
+    let num_bits = get_u32(num_bits)?;
+
+    if input.num_bits() < num_bits {
+        Ok(Value::Unit)
+    } else {
+        Err(InterpreterError::BlackBoxError(
+            BlackBoxResolutionError::Failed(
+                BlackBoxFunc::RANGE,
+                "value exceeds range check bounds".to_owned(),
+            ),
+            location,
+        ))
+    }
+}
+
 // poseidon2_permutation<let N: u32>(_input: [Field; N], _state_length: u32) -> [Field; N]
 fn poseidon2_permutation(
     interner: &mut NodeInterner,
diff --git a/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs b/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
index a373441b4e0..bae57daae15 100644
--- a/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
@@ -97,9 +97,9 @@ pub fn collect_defs(
 
     errors.extend(collector.collect_functions(context, ast.functions, crate_id));
 
-    collector.collect_trait_impls(context, ast.trait_impls, crate_id);
+    errors.extend(collector.collect_trait_impls(context, ast.trait_impls, crate_id));
 
-    collector.collect_impls(context, ast.impls, crate_id);
+    errors.extend(collector.collect_impls(context, ast.impls, crate_id));
 
     collector.collect_attributes(
         ast.inner_attributes,
@@ -163,7 +163,13 @@ impl<'a> ModCollector<'a> {
         errors
     }
 
-    fn collect_impls(&mut self, context: &mut Context, impls: Vec<TypeImpl>, krate: CrateId) {
+    fn collect_impls(
+        &mut self,
+        context: &mut Context,
+        impls: Vec<TypeImpl>,
+        krate: CrateId,
+    ) -> Vec<(CompilationError, FileId)> {
+        let mut errors = Vec::new();
         let module_id = ModuleId { krate, local_id: self.module_id };
 
         for r#impl in impls {
@@ -173,8 +179,11 @@ impl<'a> ModCollector<'a> {
                 r#impl,
                 self.file_id,
                 module_id,
+                &mut errors,
             );
         }
+
+        errors
     }
 
     fn collect_trait_impls(
@@ -182,7 +191,9 @@ impl<'a> ModCollector<'a> {
         context: &mut Context,
         impls: Vec<NoirTraitImpl>,
         krate: CrateId,
-    ) {
+    ) -> Vec<(CompilationError, FileId)> {
+        let mut errors = Vec::new();
+
         for mut trait_impl in impls {
             let trait_name = trait_impl.trait_name.clone();
 
@@ -198,6 +209,13 @@ impl<'a> ModCollector<'a> {
             let module = ModuleId { krate, local_id: self.module_id };
 
             for (_, func_id, noir_function) in &mut unresolved_functions.functions {
+                if noir_function.def.attributes.is_test_function() {
+                    let error = DefCollectorErrorKind::TestOnAssociatedFunction {
+                        span: noir_function.name_ident().span(),
+                    };
+                    errors.push((error.into(), self.file_id));
+                }
+
                 let location = Location::new(noir_function.def.span, self.file_id);
                 context.def_interner.push_function(*func_id, &noir_function.def, module, location);
             }
@@ -224,6 +242,8 @@ impl<'a> ModCollector<'a> {
 
             self.def_collector.items.trait_impls.push(unresolved_trait_impl);
         }
+
+        errors
     }
 
     fn collect_functions(
@@ -1051,6 +1071,7 @@ pub fn collect_impl(
     r#impl: TypeImpl,
     file_id: FileId,
     module_id: ModuleId,
+    errors: &mut Vec<(CompilationError, FileId)>,
 ) {
     let mut unresolved_functions =
         UnresolvedFunctions { file_id, functions: Vec::new(), trait_id: None, self_type: None };
@@ -1058,6 +1079,15 @@ pub fn collect_impl(
     for (method, _) in r#impl.methods {
         let doc_comments = method.doc_comments;
         let mut method = method.item;
+
+        if method.def.attributes.is_test_function() {
+            let error = DefCollectorErrorKind::TestOnAssociatedFunction {
+                span: method.name_ident().span(),
+            };
+            errors.push((error.into(), file_id));
+            continue;
+        }
+
         let func_id = interner.push_empty_fn();
         method.def.where_clause.extend(r#impl.where_clause.clone());
         let location = Location::new(method.span(), file_id);
diff --git a/compiler/noirc_frontend/src/hir/def_collector/errors.rs b/compiler/noirc_frontend/src/hir/def_collector/errors.rs
index d72f493092d..c08b4ff2062 100644
--- a/compiler/noirc_frontend/src/hir/def_collector/errors.rs
+++ b/compiler/noirc_frontend/src/hir/def_collector/errors.rs
@@ -82,6 +82,8 @@ pub enum DefCollectorErrorKind {
     },
     #[error("{0}")]
     UnsupportedNumericGenericType(#[from] UnsupportedNumericGenericType),
+    #[error("The `#[test]` attribute may only be used on a non-associated function")]
+    TestOnAssociatedFunction { span: Span },
 }
 
 impl DefCollectorErrorKind {
@@ -291,6 +293,12 @@ impl<'a> From<&'a DefCollectorErrorKind> for Diagnostic {
                 diag
             }
             DefCollectorErrorKind::UnsupportedNumericGenericType(err) => err.into(),
+            DefCollectorErrorKind::TestOnAssociatedFunction { span } => Diagnostic::simple_error(
+                "The `#[test]` attribute is disallowed on `impl` methods".into(),
+                String::new(),
+                *span,
+            ),
+
         }
     }
 }
diff --git a/compiler/noirc_frontend/src/tests.rs b/compiler/noirc_frontend/src/tests.rs
index b709436cccc..23f134cc2a3 100644
--- a/compiler/noirc_frontend/src/tests.rs
+++ b/compiler/noirc_frontend/src/tests.rs
@@ -3692,3 +3692,51 @@ fn allows_struct_with_generic_infix_type_as_main_input_3() {
     "#;
     assert_no_errors(src);
 }
+
+#[test]
+fn disallows_test_attribute_on_impl_method() {
+    let src = r#"
+    pub struct Foo {}
+    impl Foo {
+        #[test]
+        fn foo() {}
+    }
+
+    fn main() {}
+    "#;
+    let errors = get_program_errors(src);
+    assert_eq!(errors.len(), 1);
+
+    assert!(matches!(
+        errors[0].0,
+        CompilationError::DefinitionError(DefCollectorErrorKind::TestOnAssociatedFunction {
+            span: _
+        })
+    ));
+}
+
+#[test]
+fn disallows_test_attribute_on_trait_impl_method() {
+    let src = r#"
+    pub trait Trait {
+        fn foo() {}
+    }
+
+    pub struct Foo {}
+    impl Trait for Foo {
+        #[test]
+        fn foo() {}
+    }
+
+    fn main() {}
+    "#;
+    let errors = get_program_errors(src);
+    assert_eq!(errors.len(), 1);
+
+    assert!(matches!(
+        errors[0].0,
+        CompilationError::DefinitionError(DefCollectorErrorKind::TestOnAssociatedFunction {
+            span: _
+        })
+    ));
+}
diff --git a/test_programs/compile_failure/comptime_apply_failing_range_constraint/Nargo.toml b/test_programs/compile_failure/comptime_apply_failing_range_constraint/Nargo.toml
new file mode 100644
index 00000000000..e14cfeae5d6
--- /dev/null
+++ b/test_programs/compile_failure/comptime_apply_failing_range_constraint/Nargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "comptime_apply_failing_range_constraint"
+type = "bin"
+authors = [""]
+
+[dependencies]
diff --git a/test_programs/compile_failure/comptime_apply_failing_range_constraint/src/main.nr b/test_programs/compile_failure/comptime_apply_failing_range_constraint/src/main.nr
new file mode 100644
index 00000000000..752f13a2e51
--- /dev/null
+++ b/test_programs/compile_failure/comptime_apply_failing_range_constraint/src/main.nr
@@ -0,0 +1,5 @@
+fn main() {
+    comptime {
+        256.assert_max_bit_size::<8>()
+    }
+}
diff --git a/test_programs/compile_success_empty/comptime_apply_range_constraint/Nargo.toml b/test_programs/compile_success_empty/comptime_apply_range_constraint/Nargo.toml
new file mode 100644
index 00000000000..84d16060440
--- /dev/null
+++ b/test_programs/compile_success_empty/comptime_apply_range_constraint/Nargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "comptime_apply_range_constraint"
+type = "bin"
+authors = [""]
+
+[dependencies]
diff --git a/test_programs/compile_success_empty/comptime_apply_range_constraint/src/main.nr b/test_programs/compile_success_empty/comptime_apply_range_constraint/src/main.nr
new file mode 100644
index 00000000000..ff5e0ba9511
--- /dev/null
+++ b/test_programs/compile_success_empty/comptime_apply_range_constraint/src/main.nr
@@ -0,0 +1,5 @@
+fn main() {
+    comptime {
+        2.assert_max_bit_size::<8>()
+    }
+}