Switch from HashSet to BTreeSet for reproducibility

CHANGELOG.md

@@ -8,6 +8,7 @@
 - **[FIX]** Fix misleading error for value-type mismatches in validators (see [#241](https://github.com/greyblake/nutype/issues/241)).
 - **[FIX]** Improve rust-analyzer resilience: when `#[nutype(...)]` arguments fail to parse (e.g. while still being typed), emit a best-effort type skeleton alongside the error so the newtype stays resolvable and downstream completions keep working (see [#178](https://github.com/greyblake/nutype/issues/178)).
 - **[FIX]** Correct the validation error `Display` message for float newtypes: `less` now reads "The value must be less than ..." and `less_or_equal` reads "The value must be less or equal to ..." (the two were previously swapped). Integer and decimal were already correct.
+- **[FIX]** Macro expansion is now reproducible: traits were collected into a `HashSet`, whose iteration order varies between expansions, so the order of derives and generated impls in the emitted code was nondeterministic. Traits are now kept in a `BTreeSet` and emitted in a stable order.
 - **[INTERNAL]** Consolidate the integer, float and decimal backends onto a shared numeric code-generation and validation layer (`common/generate/numeric.rs` and shared helpers in `common/validate.rs`), removing a large amount of duplicated code. No change to generated code or public API.
 
 ### v0.7.0 - 2026-04-25

nutype_macros/src/any/generate/mod.rs

@@ -1,7 +1,7 @@
 mod error;
 mod traits;
 
-use std::collections::HashSet;
+use alloc::collections::BTreeSet;
 
 use proc_macro2::TokenStream;
 use quote::quote;
@@ -122,7 +122,7 @@ impl GenerateNewtype for AnyNewtype {
         type_name: &TypeName,
         generics: &Generics,
         inner_type: &Self::InnerType,
-        traits: HashSet<Self::TypedTrait>,
+        traits: BTreeSet<Self::TypedTrait>,
         unsafe_traits: &[SpannedDeriveUnsafeTrait],
         maybe_default_value: Option<syn::Expr>,
         guard: &AnyGuard,
@@ -148,7 +148,7 @@ impl GenerateNewtype for AnyNewtype {
         _inner_type: &Self::InnerType,
         maybe_default_value: &Option<syn::Expr>,
         guard: &Guard<Self::Sanitizer, Self::Validator>,
-        _traits: &HashSet<Self::TypedTrait>,
+        _traits: &BTreeSet<Self::TypedTrait>,
     ) -> TokenStream {
         let test_valid_default_value = gen_test_should_have_valid_default_value(
             type_name,

nutype_macros/src/any/generate/traits/mod.rs

@@ -1,9 +1,9 @@
 pub mod arbitrary;
 pub mod into_iter;
 
+use alloc::collections::BTreeSet;
 use proc_macro2::TokenStream;
 use quote::{ToTokens, quote};
-use std::collections::HashSet;
 
 use crate::{
     any::models::{AnyDeriveTrait, AnyGuard, AnyInnerType},
@@ -128,7 +128,7 @@ pub fn gen_traits(
     type_name: &TypeName,
     generics: &syn::Generics,
     inner_type: &AnyInnerType,
-    traits: HashSet<AnyDeriveTrait>,
+    traits: BTreeSet<AnyDeriveTrait>,
     unsafe_traits: &[SpannedDeriveUnsafeTrait],
     maybe_default_value: Option<syn::Expr>,
     guard: &AnyGuard,

nutype_macros/src/any/models.rs

@@ -24,7 +24,9 @@ pub enum AnyValidator {
 
 pub type SpannedAnyValidator = SpannedItem<AnyValidator>;
 
-#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
+// Note that the order in which the variants are declared here is the order
+// in which traits are derived and implemented in the generated code.
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash, PartialOrd, Ord)]
 pub enum AnyDeriveTrait {
     // Standard
     Debug,

nutype_macros/src/common/generate/mod.rs

@@ -6,8 +6,8 @@ pub mod parse_error;
 pub mod tests;
 pub mod traits;
 
+use alloc::collections::BTreeSet;
 use core::hash::Hash;
-use std::collections::HashSet;
 
 use self::traits::GeneratedTraits;
 
@@ -220,7 +220,7 @@ pub trait GenerateNewtype {
         type_name: &TypeName,
         generics: &Generics,
         inner_type: &Self::InnerType,
-        traits: HashSet<Self::TypedTrait>,
+        traits: BTreeSet<Self::TypedTrait>,
         unsafe_traits: &[SpannedDeriveUnsafeTrait],
         maybe_default_value: Option<syn::Expr>,
         guard: &Guard<Self::Sanitizer, Self::Validator>,
@@ -539,7 +539,7 @@ pub trait GenerateNewtype {
         inner_type: &Self::InnerType,
         maybe_default_value: &Option<syn::Expr>,
         guard: &Guard<Self::Sanitizer, Self::Validator>,
-        traits: &HashSet<Self::TypedTrait>,
+        traits: &BTreeSet<Self::TypedTrait>,
     ) -> TokenStream;
 }
 
@@ -548,7 +548,7 @@ pub trait GenerateNewtype {
 /// because nutype weaves the custom functions into its own generated impls.
 fn validate_serde_customization<TypedTrait: TypeTrait>(
     serde_customization: &SerdeCustomization,
-    traits: &HashSet<TypedTrait>,
+    traits: &BTreeSet<TypedTrait>,
     conditional_derives: &[ConditionalDeriveGroup<TypedTrait>],
 ) -> Result<(), syn::Error> {
     let has_serialize = traits.iter().any(|t| t.is_serde_serialize())

nutype_macros/src/common/generate/traits.rs

@@ -1,5 +1,4 @@
-use core::hash::Hash;
-use std::collections::HashSet;
+use alloc::collections::BTreeSet;
 
 use proc_macro2::TokenStream;
 use quote::{ToTokens, quote};
@@ -47,7 +46,7 @@ pub struct GeneratableTraits<TransparentTrait, IrregularTrait> {
 }
 
 pub fn split_into_generatable_traits<InputTrait, TransparentTrait, IrregularTrait>(
-    input_traits: HashSet<InputTrait>,
+    input_traits: BTreeSet<InputTrait>,
 ) -> GeneratableTraits<TransparentTrait, IrregularTrait>
 where
     GeneratableTrait<TransparentTrait, IrregularTrait>: From<InputTrait>,
@@ -109,7 +108,7 @@ pub fn process_conditional_derives<InputTrait, TransparentTrait, IrregularTrait>
     gen_impl_traits: impl Fn(Vec<IrregularTrait>) -> Result<TokenStream, syn::Error>,
 ) -> Result<ConditionalTraits, syn::Error>
 where
-    InputTrait: Eq + Hash + Clone,
+    InputTrait: Ord + Clone,
     TransparentTrait: ToTokens,
     IrregularTrait: HasGeneratedParseError,
     GeneratableTrait<TransparentTrait, IrregularTrait>: From<InputTrait>,
@@ -121,7 +120,7 @@ where
     for group in conditional_derives {
         let pred = &group.predicate;
 
-        let cond_traits: HashSet<InputTrait> = group.typed_traits.iter().cloned().collect();
+        let cond_traits: BTreeSet<InputTrait> = group.typed_traits.iter().cloned().collect();
         let GeneratableTraits {
             transparent_traits: cond_transparent,
             irregular_traits: cond_irregular,

nutype_macros/src/common/models.rs

@@ -1,8 +1,8 @@
 mod error_type_path;
 
+use alloc::collections::BTreeSet;
 use core::{fmt::Debug, ops::Add};
 use kinded::Kinded;
-use std::collections::HashSet;
 use syn::Generics;
 
 use proc_macro2::{Span, TokenStream};
@@ -493,7 +493,7 @@ pub struct CfgAttrEntry {
 /// and conditional derive entries.
 pub struct ValidatedDerives<TypedTrait> {
     /// Typed traits from unconditional `derive(...)`.
-    pub unconditional: HashSet<TypedTrait>,
+    pub unconditional: BTreeSet<TypedTrait>,
 
     /// Typed traits from `cfg_attr(...)` entries, grouped by predicate.
     pub conditional: Vec<ValidatedCfgAttrDerives<TypedTrait>>,
@@ -696,7 +696,7 @@ impl ToTokens for ConstructorVisibility {
 pub struct GenerateParams<IT, Trait, Guard> {
     pub inner_type: IT,
     pub doc_attrs: Vec<Attribute>,
-    pub traits: HashSet<Trait>,
+    pub traits: BTreeSet<Trait>,
     pub unsafe_traits: Vec<SpannedDeriveUnsafeTrait>,
     pub vis: syn::Visibility,
     pub type_name: TypeName,

nutype_macros/src/common/parse/meta.rs

@@ -14,7 +14,7 @@ use crate::{
 };
 
 pub fn parse_meta(token_stream: TokenStream) -> Result<Meta, syn::Error> {
-    let input: DeriveInput = syn::parse(token_stream.into())?;
+    let input: DeriveInput = syn::parse2(token_stream)?;
 
     let input_span = input.span();
     let DeriveInput {

nutype_macros/src/common/validate.rs

@@ -1,4 +1,4 @@
-use core::hash::Hash;
+use alloc::collections::BTreeSet;
 use kinded::Kinded;
 use proc_macro2::Span;
 use std::collections::HashSet;
@@ -282,7 +282,7 @@ pub fn validate_all_derive_traits<TypedTrait>(
     convert: impl Fn(DeriveTrait, bool, Span) -> Result<TypedTrait, syn::Error>,
 ) -> Result<ValidatedDerives<TypedTrait>, syn::Error>
 where
-    TypedTrait: Eq + Hash + TypeTrait,
+    TypedTrait: Ord + TypeTrait,
 {
     // 0. Check for unconditional-vs-conditional duplicates
     check_cfg_attr_no_duplicates(&derive_traits, cfg_attr_entries)?;
@@ -302,7 +302,7 @@ where
     let unconditional = derive_traits
         .iter()
         .map(|st| convert(st.item, has_validation, st.span))
-        .collect::<Result<HashSet<_>, _>>()?;
+        .collect::<Result<BTreeSet<_>, _>>()?;
 
     // 4. Convert conditional traits (same conversion, per entry)
     let conditional = cfg_attr_entries

nutype_macros/src/decimal/generate/mod.rs

@@ -1,6 +1,6 @@
 pub mod traits;
 
-use std::collections::HashSet;
+use alloc::collections::BTreeSet;
 
 use proc_macro2::TokenStream;
 use quote::{ToTokens, quote};
@@ -70,7 +70,7 @@ where
         type_name: &TypeName,
         generics: &Generics,
         inner_type: &Self::InnerType,
-        traits: HashSet<Self::TypedTrait>,
+        traits: BTreeSet<Self::TypedTrait>,
         unsafe_traits: &[SpannedDeriveUnsafeTrait],
         maybe_default_value: Option<syn::Expr>,
         guard: &DecimalGuard<T>,
@@ -96,7 +96,7 @@ where
         _inner_type: &Self::InnerType,
         maybe_default_value: &Option<syn::Expr>,
         guard: &Guard<Self::Sanitizer, Self::Validator>,
-        _traits: &HashSet<Self::TypedTrait>,
+        _traits: &BTreeSet<Self::TypedTrait>,
     ) -> TokenStream {
         let test_lower_vs_upper = guard.standard_validators().and_then(|validators| {
             gen_test_should_have_consistent_lower_and_upper_boundaries(type_name, validators)

nutype_macros/src/decimal/generate/traits/mod.rs

@@ -1,6 +1,6 @@
 mod arbitrary;
 
-use std::collections::HashSet;
+use alloc::collections::BTreeSet;
 
 use proc_macro2::TokenStream;
 use quote::{ToTokens, quote};
@@ -28,7 +28,7 @@ pub fn gen_traits<T: ToTokens>(
     type_name: &TypeName,
     generics: &Generics,
     inner_type: &DecimalInnerType,
-    traits: HashSet<DecimalDeriveTrait>,
+    traits: BTreeSet<DecimalDeriveTrait>,
     unsafe_traits: &[SpannedDeriveUnsafeTrait],
     maybe_default_value: Option<syn::Expr>,
     guard: &DecimalGuard<T>,

nutype_macros/src/decimal/models.rs

@@ -153,7 +153,10 @@ pub type SpannedDecimalValidator<T> = SpannedItem<DecimalValidator<T>>;
 // * no `ValuableValuable` (`rust_decimal::Decimal` does not implement `Valuable`),
 // * `ArbitraryArbitrary` is supported (requires the user to enable
 //   `rust_decimal/rust-fuzz`).
-#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
+//
+// Note that the order in which the variants are declared here is the order
+// in which traits are derived and implemented in the generated code.
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash, PartialOrd, Ord)]
 pub enum DecimalDeriveTrait {
     // Standard
     Debug,