fix!: Include kind in StructDefinition::generics and fix derivation of Eq in structs with numeric generics

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

@@ -185,7 +185,9 @@ impl<'local, 'context> Interpreter<'local, 'context> {
             "struct_def_fields_as_written" => {
                 struct_def_fields_as_written(interner, arguments, location)
             }
-            "struct_def_generics" => struct_def_generics(interner, arguments, location),
+            "struct_def_generics" => {
+                struct_def_generics(interner, arguments, return_type, location)
+            }
             "struct_def_has_named_attribute" => {
                 struct_def_has_named_attribute(interner, arguments, location)
             }
@@ -445,22 +447,50 @@ fn struct_def_as_type(
     Ok(Value::Type(Type::Struct(struct_def_rc, generics)))
 }
 
-/// fn generics(self) -> [Type]
+/// fn generics(self) -> [(Type, Option<Type>)]
 fn struct_def_generics(
     interner: &NodeInterner,
     arguments: Vec<(Value, Location)>,
+    return_type: Type,
     location: Location,
 ) -> IResult<Value> {
     let argument = check_one_argument(arguments, location)?;
     let struct_id = get_struct(argument)?;
     let struct_def = interner.get_struct(struct_id);
     let struct_def = struct_def.borrow();
 
-    let generics =
-        struct_def.generics.iter().map(|generic| Value::Type(generic.clone().as_named_generic()));
+    let expected = Type::Slice(Box::new(Type::Tuple(vec![
+        Type::Quoted(QuotedType::Type),
+        interner.next_type_variable(), // Option
+    ])));
+
+    let actual = return_type.clone();
+
+    let slice_item_type = match return_type {
+        Type::Slice(item_type) => *item_type,
+        _ => return Err(InterpreterError::TypeMismatch { expected, actual, location }),
+    };
+
+    let option_typ = match &slice_item_type {
+        Type::Tuple(types) if types.len() == 2 => types[1].clone(),
+        _ => return Err(InterpreterError::TypeMismatch { expected, actual, location }),
+    };
+
+    let generics: IResult<_> = struct_def
+        .generics
+        .iter()
+        .map(|generic| -> IResult<Value> {
+            let generic_as_named = generic.clone().as_named_generic();
+            let numeric_type = match generic_as_named.kind() {
+                Kind::Numeric(numeric_type) => Some(Value::Type(*numeric_type)),
+                _ => None,
+            };
+            let numeric_type = option(option_typ.clone(), numeric_type, location.span)?;
+            Ok(Value::Tuple(vec![Value::Type(generic_as_named), numeric_type]))
+        })
+        .collect();
 
-    let typ = Type::Slice(Box::new(Type::Quoted(QuotedType::Type)));
-    Ok(Value::Slice(generics.collect(), typ))
+    Ok(Value::Slice(generics?, slice_item_type))
 }
 
 fn struct_def_hash(arguments: Vec<(Value, Location)>, location: Location) -> IResult<Value> {

noir_stdlib/src/meta/mod.nr

@@ -97,8 +97,28 @@ pub comptime fn make_trait_impl<Env1, Env2>(
 ) -> Quoted {
     // docs:end:make_trait_impl
     let typ = s.as_type();
-    let impl_generics = s.generics().map(|g| quote { $g }).join(quote {,});
-    let where_clause = s.generics().map(|name| quote { $name: $trait_name }).join(quote {,});
+    // Urgh, if we emit he type directly, the compiler fails to match it with the type in impl generics.
+    let typ = f"{typ}".quoted_contents();
+
+    let mut impl_generics = &[];
+    let mut where_clause = &[];
+    for g in s.generics() {
+        let (typ, numeric_type) = g;
+        // Urgh again, if we emit the type directly, since <let T: u32> expects T to be an ident, will fail parsing
+        let typ = f"{typ}".quoted_contents();
+
+        if numeric_type.is_some() {
+            let numeric_type = numeric_type.unwrap_unchecked();
+            // Numeric generics expect the name to be an ident, not a type
+            impl_generics = impl_generics.push_back(quote { let $typ : $numeric_type });
+        } else {
+            impl_generics = impl_generics.push_back(quote { $typ });
+            where_clause = where_clause.push_back(quote { $typ: $trait_name });
+        }
+    }
+
+    let impl_generics = impl_generics.join(quote {, });
+    let where_clause = where_clause.join(quote {, });
 
     // `for_each_field(field1) $join_fields_with for_each_field(field2) $join_fields_with ...`
     let fields = s.fields_as_written().map(|f: (Quoted, Type)| {

noir_stdlib/src/meta/struct_def.nr

@@ -1,3 +1,5 @@
+use crate::option::Option;
+
 impl StructDefinition {
     #[builtin(struct_def_add_attribute)]
     // docs:start:add_attribute
@@ -21,10 +23,11 @@ impl StructDefinition {
     pub comptime fn has_named_attribute<let N: u32>(self, name: str<N>) -> bool {}
     // docs:end:has_named_attribute
 
-    /// Return each generic on this struct.
+    /// Return (type, option<type>) pairs of each generic in this struct definition.
+    /// If a generic is numeric, the second element of the pair will contain the numeric type.
     #[builtin(struct_def_generics)]
     // docs:start:generics
-    pub comptime fn generics(self) -> [Type] {}
+    pub comptime fn generics(self) -> [(Type, Option<Type>)] {}
     // docs:end:generics
 
     /// Returns (name, type) pairs of each field in this struct.

test_programs/compile_success_empty/comptime_struct_definition/src/main.nr

@@ -39,7 +39,9 @@ mod foo {
 
         let generics = s.generics();
         assert_eq(generics.len(), 1);
-        assert_eq(generics[0], new_generic);
+        let (typ, numeric) = generics[0];
+        assert_eq(typ, new_generic);
+        assert(numeric.is_none());
     }
     // docs:end:add-generic-example
 }

test_programs/compile_success_empty/eq_derivation_with_numeric_generics/Nargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "eq_derivation_with_numeric_generics"
+type = "bin"
+authors = [""]
+
+[dependencies]

test_programs/compile_success_empty/eq_derivation_with_numeric_generics/src/main.nr

@@ -0,0 +1,12 @@
+#[derive(Eq)]
+struct Foo<let T: u32> {
+    a: [Field; T],
+    b: u32,
+}
+
+fn main() {
+    let foo = Foo { a: [0; 10], b: 27 };
+    let bar = Foo { a: [0; 10], b: 28 };
+    assert(foo != bar);
+}
+