fix: allow range checks to be performed within the comptime intepreter (

#6514)

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)),

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,

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]

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>()
+    }
+}

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]

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>()
+    }
+}