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fix: serde and packable on empty #18584

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Merged
benesjan merged 1 commit into from
Nov 25, 2025
Merged

fix: serde and packable on empty #18584

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75 changes: 60 additions & 15 deletions noir-projects/noir-protocol-circuits/crates/types/src/meta/mod.nr
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Original file line number Diff line number Diff line change
Expand Up @@ -228,14 +228,20 @@ pub(crate) comptime fn derive_deserialize(s: TypeDefinition) -> Quoted {
let generics_declarations = get_generics_declarations(s);
let where_deserialize_clause = get_where_trait_clause(s, quote {Deserialize});

// The following will give us <type_of_struct_member_1 as Deserialize>::N + <type_of_struct_member_2 as Deserialize>::N + ...
let right_hand_side_of_definition_of_n = params
.map(|(_, param_type, _): (Quoted, Type, Quoted)| {
quote {
// The following will give us:
// <type_of_struct_member_1 as Deserialize>::N + <type_of_struct_member_2 as Deserialize>::N + ...
// (or 0 if the struct has no members)
let right_hand_side_of_definition_of_n = if params.len() > 0 {
params
.map(|(_, param_type, _): (Quoted, Type, Quoted)| {
quote {
<$param_type as $crate::traits::Deserialize>::N
}
})
.join(quote {+});
})
.join(quote {+})
} else {
quote {0}
};

// For structs containing a single member, we can enhance performance by directly deserializing the input array,
// bypassing the need for loop-based array construction. While this optimization yields significant benefits in
Expand Down Expand Up @@ -269,11 +275,15 @@ pub(crate) comptime fn derive_deserialize(s: TypeDefinition) -> Quoted {

Self { $struct_members }
}
} else {
} else if params.len() == 1 {
let param_name = params[0].0;
quote {
Self { $param_name: $crate::traits::Deserialize::deserialize(serialized) }
}
} else {
quote {
Self {}
}
};

quote {
Expand Down Expand Up @@ -365,14 +375,20 @@ pub comptime fn derive_packable(s: TypeDefinition) -> Quoted {
let generics_declarations = get_generics_declarations(s);
let where_packable_clause = get_where_trait_clause(s, quote {Packable});

// The following will give us <type_of_struct_member_1 as Packable>::N + <type_of_struct_member_2 as Packable>::N + ...
let right_hand_side_of_definition_of_n = params
.map(|(_, param_type, _): (Quoted, Type, Quoted)| {
quote {
// The following will give us:
// <type_of_struct_member_1 as Packable>::N + <type_of_struct_member_2 as Packable>::N + ...
// (or 0 if the struct has no members)
let right_hand_side_of_definition_of_n = if params.len() > 0 {
params
.map(|(_, param_type, _): (Quoted, Type, Quoted)| {
quote {
<$param_type as $crate::traits::Packable>::N
}
})
.join(quote {+});
})
.join(quote {+})
} else {
quote {0}
};

// For structs containing a single member, we can enhance performance by directly returning the packed member,
// bypassing the need for loop-based array construction. While this optimization yields significant benefits in
Expand Down Expand Up @@ -404,11 +420,15 @@ pub comptime fn derive_packable(s: TypeDefinition) -> Quoted {

result
}
} else {
} else if params.len() == 1 {
let param_name = params[0].0;
quote {
$crate::traits::Packable::pack(self.$param_name)
}
} else {
quote {
[0; Self::N]
}
};

// For structs containing a single member, we can enhance performance by directly unpacking the input array,
Expand Down Expand Up @@ -443,11 +463,15 @@ pub comptime fn derive_packable(s: TypeDefinition) -> Quoted {
$unpacking_of_struct_members
Self { $struct_members }
}
} else {
} else if params.len() == 1 {
let param_name = params[0].0;
quote {
Self { $param_name: $crate::traits::Packable::unpack(packed) }
}
} else {
quote {
Self {}
}
};

quote {
Expand All @@ -472,6 +496,9 @@ pub comptime fn derive_packable(s: TypeDefinition) -> Quoted {
mod test {
use crate::traits::{Deserialize, Packable, Serialize};

#[derive(Deserialize, Eq, Packable, Serialize)]
pub struct Empty {}

#[derive(Deserialize, Eq, Packable, Serialize)]
pub struct Smol {
a: Field,
Expand All @@ -498,6 +525,24 @@ mod test {
pub length: u32,
}

#[test]
fn serde_on_empty() {
let original = Empty {};
let serialized = original.serialize();
assert_eq(serialized, [], "Serialized does not match empty array");
let deserialized = Empty::deserialize(serialized);
assert_eq(deserialized, original, "Deserialized does not match original");
}

#[test]
fn packable_on_empty() {
let original = Empty {};
let packed = original.pack();
assert_eq(packed, [], "Packed does not match empty array");
let unpacked = Empty::unpack(packed);
assert_eq(unpacked, original, "Unpacked does not match original");
}

#[test]
fn serde_on_smol() {
let smol = Smol { a: 1, b: 2 };
Expand Down
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