feat: add FunctionDefinition methods is_unconstrained and `set_un…

…constrained` (#5962)

…constrained`

# Description

## Problem

Resolves #5954

## Summary



## 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.

compiler/noirc_frontend/src/hir/comptime/interpreter/builtin.rs

@@ -106,6 +106,9 @@ impl<'local, 'context> Interpreter<'local, 'context> {
             "function_def_has_named_attribute" => {
                 function_def_has_named_attribute(interner, arguments, location)
             }
+            "function_def_is_unconstrained" => {
+                function_def_is_unconstrained(interner, arguments, location)
+            }
             "function_def_module" => function_def_module(interner, arguments, location),
             "function_def_name" => function_def_name(interner, arguments, location),
             "function_def_parameters" => function_def_parameters(interner, arguments, location),
@@ -118,6 +121,9 @@ impl<'local, 'context> Interpreter<'local, 'context> {
             "function_def_set_return_public" => {
                 function_def_set_return_public(self, arguments, location)
             }
+            "function_def_set_unconstrained" => {
+                function_def_set_unconstrained(self, arguments, location)
+            }
             "module_add_item" => module_add_item(self, arguments, location),
             "module_functions" => module_functions(self, arguments, location),
             "module_has_named_attribute" => module_has_named_attribute(self, arguments, location),
@@ -1927,6 +1933,18 @@ fn function_def_has_named_attribute(
     Ok(Value::Bool(has_named_attribute(&name, attributes, location)))
 }
 
+// fn is_unconstrained(self) -> bool
+fn function_def_is_unconstrained(
+    interner: &NodeInterner,
+    arguments: Vec<(Value, Location)>,
+    location: Location,
+) -> IResult<Value> {
+    let self_argument = check_one_argument(arguments, location)?;
+    let func_id = get_function_def(self_argument)?;
+    let is_unconstrained = interner.function_modifiers(&func_id).is_unconstrained;
+    Ok(Value::Bool(is_unconstrained))
+}
+
 // fn module(self) -> Module
 fn function_def_module(
     interner: &NodeInterner,
@@ -2124,6 +2142,25 @@ fn function_def_set_return_public(
     Ok(Value::Unit)
 }
 
+// fn set_unconstrained(self, value: bool)
+fn function_def_set_unconstrained(
+    interpreter: &mut Interpreter,
+    arguments: Vec<(Value, Location)>,
+    location: Location,
+) -> IResult<Value> {
+    let (self_argument, unconstrained) = check_two_arguments(arguments, location)?;
+
+    let func_id = get_function_def(self_argument)?;
+    check_function_not_yet_resolved(interpreter, func_id, location)?;
+
+    let unconstrained = get_bool(unconstrained)?;
+
+    let modifiers = interpreter.elaborator.interner.function_modifiers_mut(&func_id);
+    modifiers.is_unconstrained = unconstrained;
+
+    Ok(Value::Unit)
+}
+
 // fn add_item(self, item: Quoted)
 fn module_add_item(
     interpreter: &mut Interpreter,

docs/docs/noir/standard_library/meta/function_def.md

@@ -29,6 +29,12 @@ This means any functions called at compile-time are invalid targets for this met
 
 Returns true if this function has a custom attribute with the given name.
 
+### is_unconstrained
+
+#include_code is_unconstrained noir_stdlib/src/meta/function_def.nr rust
+
+Returns true if this function is unconstrained.
+
 ### module
 
 #include_code module noir_stdlib/src/meta/function_def.nr rust
@@ -86,4 +92,12 @@ This means any functions called at compile-time are invalid targets for this met
 
 Mutates the function's return visibility to public (if `true` is given) or private (if `false` is given). 
 This is only valid on functions in the current crate which have not yet been resolved. 
+This means any functions called at compile-time are invalid targets for this method.
+
+### set_unconstrained
+
+#include_code set_unconstrained noir_stdlib/src/meta/function_def.nr rust
+
+Mutates the function to be unconstrained (if `true` is given) or not (if `false` is given).
+This is only valid on functions in the current crate which have not yet been resolved. 
 This means any functions called at compile-time are invalid targets for this method.

noir_stdlib/src/meta/function_def.nr

@@ -14,6 +14,11 @@ impl FunctionDefinition {
     fn has_named_attribute(self, name: Quoted) -> bool {}
     // docs:end:has_named_attribute
 
+    #[builtin(function_def_is_unconstrained)]
+    // docs:start:is_unconstrained
+    fn is_unconstrained(self) -> bool {}
+    // docs:end:is_unconstrained
+
     #[builtin(function_def_module)]
     // docs:start:module
     fn module(self) -> Module {}
@@ -53,4 +58,9 @@ impl FunctionDefinition {
     // docs:start:set_return_public
     fn set_return_public(self, public: bool) {}
     // docs:end:set_return_public
+
+    #[builtin(function_def_set_unconstrained)]
+    // docs:start:set_unconstrained
+    fn set_unconstrained(self, value: bool) {}
+    // docs:end:set_unconstrained
 }

test_programs/compile_success_empty/comptime_function_definition/src/main.nr

@@ -76,5 +76,13 @@ mod foo {
 
     fn attr(f: FunctionDefinition) {
         assert_eq(f.module().name(), quote { foo });
+
+        assert(!f.is_unconstrained());
+
+        f.set_unconstrained(true);
+        assert(f.is_unconstrained());
+
+        f.set_unconstrained(false);
+        assert(!f.is_unconstrained());
     }
 }