feat: show backtrace on comptime assertion failures (#5842)

# Description

## Problem

Resolves #5828

## Summary

`CustomDiagnostic` didn't have a `call_stack` property because so far
this wasn't needed. I only added it for `FailingConstraint`, which is,
_I think_, the only case where a backtrace might be needed. In all other
cases (for example "wrong number of arguments" it might be clear why
it's failing without needing a backtrace).

Here's an example output:

```
error: Assertion failed
   ┌─ std/option.nr:33:16
   │
33 │         assert(self._is_some);
   │                -------------
   │
   ┌─ src/main.nr:8:9
   │
 8 │         foo();
   │         -----
   │
   ┌─ src/other.nr:2:5
   │
 2 │     bar();
   │     -----
   ·
 7 │     let _ = expr.as_integer().unwrap();
   │             --------------------------
   │

Aborting due to 1 previous error
```

## Additional Context

None.

## Documentation

Check one:
- [x] No documentation needed.
- [ ] 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.

aztec_macros/Cargo.toml

@@ -18,5 +18,6 @@ noirc_frontend.workspace = true
 noirc_errors.workspace = true
 iter-extended.workspace = true
 convert_case = "0.6.0"
+im.workspace = true
 regex = "1.10"
 tiny-keccak = { version = "2.0.0", features = ["keccak"] }

compiler/noirc_errors/src/reporter.rs

@@ -46,7 +46,7 @@ impl CustomDiagnostic {
     ) -> CustomDiagnostic {
         CustomDiagnostic {
             message: primary_message,
-            secondaries: vec![CustomLabel::new(secondary_message, secondary_span)],
+            secondaries: vec![CustomLabel::new(secondary_message, secondary_span, None)],
             notes: Vec::new(),
             kind,
         }
@@ -98,7 +98,7 @@ impl CustomDiagnostic {
     ) -> CustomDiagnostic {
         CustomDiagnostic {
             message: primary_message,
-            secondaries: vec![CustomLabel::new(secondary_message, secondary_span)],
+            secondaries: vec![CustomLabel::new(secondary_message, secondary_span, None)],
             notes: Vec::new(),
             kind: DiagnosticKind::Bug,
         }
@@ -113,7 +113,11 @@ impl CustomDiagnostic {
     }
 
     pub fn add_secondary(&mut self, message: String, span: Span) {
-        self.secondaries.push(CustomLabel::new(message, span));
+        self.secondaries.push(CustomLabel::new(message, span, None));
+    }
+
+    pub fn add_secondary_with_file(&mut self, message: String, span: Span, file: fm::FileId) {
+        self.secondaries.push(CustomLabel::new(message, span, Some(file)));
     }
 
     pub fn is_error(&self) -> bool {
@@ -153,11 +157,12 @@ impl std::fmt::Display for CustomDiagnostic {
 pub struct CustomLabel {
     pub message: String,
     pub span: Span,
+    pub file: Option<fm::FileId>,
 }
 
 impl CustomLabel {
-    fn new(message: String, span: Span) -> CustomLabel {
-        CustomLabel { message, span }
+    fn new(message: String, span: Span, file: Option<fm::FileId>) -> CustomLabel {
+        CustomLabel { message, span, file }
     }
 }
 
@@ -234,7 +239,8 @@ fn convert_diagnostic(
             .map(|sl| {
                 let start_span = sl.span.start() as usize;
                 let end_span = sl.span.end() as usize;
-                Label::secondary(file_id, start_span..end_span).with_message(&sl.message)
+                let file = sl.file.unwrap_or(file_id);
+                Label::secondary(file, start_span..end_span).with_message(&sl.message)
             })
             .collect()
     } else {

compiler/noirc_frontend/src/elaborator/comptime.rs

@@ -46,6 +46,7 @@ impl<'context> Elaborator<'context> {
             self.crate_id,
             self.debug_comptime_in_file,
             self.enable_arithmetic_generics,
+            self.interpreter_call_stack.clone(),
         );
 
         elaborator.function_context.push(FunctionContext::default());

compiler/noirc_frontend/src/elaborator/mod.rs

@@ -168,6 +168,8 @@ pub struct Elaborator<'context> {
 
     /// Temporary flag to enable the experimental arithmetic generics feature
     enable_arithmetic_generics: bool,
+
+    pub(crate) interpreter_call_stack: im::Vector<Location>,
 }
 
 #[derive(Default)]
@@ -191,6 +193,7 @@ impl<'context> Elaborator<'context> {
         crate_id: CrateId,
         debug_comptime_in_file: Option<FileId>,
         enable_arithmetic_generics: bool,
+        interpreter_call_stack: im::Vector<Location>,
     ) -> Self {
         Self {
             scopes: ScopeForest::default(),
@@ -214,6 +217,7 @@ impl<'context> Elaborator<'context> {
             unresolved_globals: BTreeMap::new(),
             enable_arithmetic_generics,
             current_trait: None,
+            interpreter_call_stack,
         }
     }
 
@@ -229,6 +233,7 @@ impl<'context> Elaborator<'context> {
             crate_id,
             debug_comptime_in_file,
             enable_arithmetic_generics,
+            im::Vector::new(),
         )
     }
 

compiler/noirc_frontend/src/hir/comptime/errors.rs

@@ -56,6 +56,7 @@ pub enum InterpreterError {
     FailingConstraint {
         message: Option<String>,
         location: Location,
+        call_stack: im::Vector<Location>,
     },
     NoMethodFound {
         name: String,
@@ -353,12 +354,20 @@ impl<'a> From<&'a InterpreterError> for CustomDiagnostic {
                 let msg = format!("Expected a `bool` but found `{typ}`");
                 CustomDiagnostic::simple_error(msg, String::new(), location.span)
             }
-            InterpreterError::FailingConstraint { message, location } => {
+            InterpreterError::FailingConstraint { message, location, call_stack } => {
                 let (primary, secondary) = match message {
                     Some(msg) => (msg.clone(), "Assertion failed".into()),
                     None => ("Assertion failed".into(), String::new()),
                 };
-                CustomDiagnostic::simple_error(primary, secondary, location.span)
+                let mut diagnostic =
+                    CustomDiagnostic::simple_error(primary, secondary, location.span);
+
+                // Only take at most 3 frames starting from the top of the stack to avoid producing too much output
+                for frame in call_stack.iter().rev().take(3) {
+                    diagnostic.add_secondary_with_file("".to_string(), frame.span, frame.file);
+                }
+
+                diagnostic
             }
             InterpreterError::NoMethodFound { name, typ, location } => {
                 let msg = format!("No method named `{name}` found for type `{typ}`");

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

@@ -70,7 +70,8 @@ impl<'local, 'interner> Interpreter<'local, 'interner> {
         current_function: Option<FuncId>,
     ) -> Self {
         let bound_generics = Vec::new();
-        Self { elaborator, crate_id, current_function, bound_generics, in_loop: false }
+        let in_loop = false;
+        Self { elaborator, crate_id, current_function, bound_generics, in_loop }
     }
 
     pub(crate) fn call_function(
@@ -99,8 +100,11 @@ impl<'local, 'interner> Interpreter<'local, 'interner> {
         }
 
         self.remember_bindings(&instantiation_bindings, &impl_bindings);
+        self.elaborator.interpreter_call_stack.push_back(location);
+
         let result = self.call_function_inner(function, arguments, location);
 
+        self.elaborator.interpreter_call_stack.pop_back();
         undo_instantiation_bindings(impl_bindings);
         undo_instantiation_bindings(instantiation_bindings);
         self.rebind_generics_from_previous_function();
@@ -1462,7 +1466,8 @@ impl<'local, 'interner> Interpreter<'local, 'interner> {
                 let message = constrain.2.and_then(|expr| self.evaluate(expr).ok());
                 let message =
                     message.map(|value| value.display(self.elaborator.interner).to_string());
-                Err(InterpreterError::FailingConstraint { location, message })
+                let call_stack = self.elaborator.interpreter_call_stack.clone();
+                Err(InterpreterError::FailingConstraint { location, message, call_stack })
             }
             value => {
                 let location = self.elaborator.interner.expr_location(&constrain.0);

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

@@ -48,6 +48,7 @@ impl<'local, 'context> Interpreter<'local, 'context> {
         location: Location,
     ) -> IResult<Value> {
         let interner = &mut self.elaborator.interner;
+        let call_stack = &self.elaborator.interpreter_call_stack;
         match name {
             "array_as_str_unchecked" => array_as_str_unchecked(interner, arguments, location),
             "array_len" => array_len(interner, arguments, location),
@@ -110,11 +111,11 @@ impl<'local, 'context> Interpreter<'local, 'context> {
             "quoted_as_type" => quoted_as_type(self, arguments, location),
             "quoted_eq" => quoted_eq(arguments, location),
             "slice_insert" => slice_insert(interner, arguments, location),
-            "slice_pop_back" => slice_pop_back(interner, arguments, location),
-            "slice_pop_front" => slice_pop_front(interner, arguments, location),
+            "slice_pop_back" => slice_pop_back(interner, arguments, location, call_stack),
+            "slice_pop_front" => slice_pop_front(interner, arguments, location, call_stack),
             "slice_push_back" => slice_push_back(interner, arguments, location),
             "slice_push_front" => slice_push_front(interner, arguments, location),
-            "slice_remove" => slice_remove(interner, arguments, location),
+            "slice_remove" => slice_remove(interner, arguments, location, call_stack),
             "struct_def_as_type" => struct_def_as_type(interner, arguments, location),
             "struct_def_fields" => struct_def_fields(interner, arguments, location),
             "struct_def_generics" => struct_def_generics(interner, arguments, location),
@@ -154,8 +155,16 @@ impl<'local, 'context> Interpreter<'local, 'context> {
     }
 }
 
-fn failing_constraint<T>(message: impl Into<String>, location: Location) -> IResult<T> {
-    Err(InterpreterError::FailingConstraint { message: Some(message.into()), location })
+fn failing_constraint<T>(
+    message: impl Into<String>,
+    location: Location,
+    call_stack: &im::Vector<Location>,
+) -> IResult<T> {
+    Err(InterpreterError::FailingConstraint {
+        message: Some(message.into()),
+        location,
+        call_stack: call_stack.clone(),
+    })
 }
 
 fn array_len(
@@ -287,22 +296,23 @@ fn slice_remove(
     interner: &mut NodeInterner,
     arguments: Vec<(Value, Location)>,
     location: Location,
+    call_stack: &im::Vector<Location>,
 ) -> IResult<Value> {
     let (slice, index) = check_two_arguments(arguments, location)?;
 
     let (mut values, typ) = get_slice(interner, slice)?;
     let index = get_u32(index)? as usize;
 
     if values.is_empty() {
-        return failing_constraint("slice_remove called on empty slice", location);
+        return failing_constraint("slice_remove called on empty slice", location, call_stack);
     }
 
     if index >= values.len() {
         let message = format!(
             "slice_remove: index {index} is out of bounds for a slice of length {}",
             values.len()
         );
-        return failing_constraint(message, location);
+        return failing_constraint(message, location, call_stack);
     }
 
     let element = values.remove(index);
@@ -325,27 +335,29 @@ fn slice_pop_front(
     interner: &mut NodeInterner,
     arguments: Vec<(Value, Location)>,
     location: Location,
+    call_stack: &im::Vector<Location>,
 ) -> IResult<Value> {
     let argument = check_one_argument(arguments, location)?;
 
     let (mut values, typ) = get_slice(interner, argument)?;
     match values.pop_front() {
         Some(element) => Ok(Value::Tuple(vec![element, Value::Slice(values, typ)])),
-        None => failing_constraint("slice_pop_front called on empty slice", location),
+        None => failing_constraint("slice_pop_front called on empty slice", location, call_stack),
     }
 }
 
 fn slice_pop_back(
     interner: &mut NodeInterner,
     arguments: Vec<(Value, Location)>,
     location: Location,
+    call_stack: &im::Vector<Location>,
 ) -> IResult<Value> {
     let argument = check_one_argument(arguments, location)?;
 
     let (mut values, typ) = get_slice(interner, argument)?;
     match values.pop_back() {
         Some(element) => Ok(Value::Tuple(vec![Value::Slice(values, typ), element])),
-        None => failing_constraint("slice_pop_back called on empty slice", location),
+        None => failing_constraint("slice_pop_back called on empty slice", location, call_stack),
     }
 }