Use BTreeSet for stable ordering of type params.

Signed-off-by: Toralf Wittner <tw@dtex.org>

Author: twittner

minicbor-derive/src/blacklist.rs

@@ -1,14 +1,14 @@
-use std::collections::HashSet;
+use std::collections::BTreeSet;
 use std::ops::Deref;
 
 use crate::{collect_type_params, is_phantom_data, Mode};
 use crate::{attrs::CustomCodec, fields::Fields};
 
-pub(crate) struct Blacklist(HashSet<syn::Ident>);
+pub(crate) struct Blacklist(BTreeSet<syn::Ident>);
 
 impl Blacklist {
     pub(crate) fn empty() -> Self {
-        Self(HashSet::new())
+        Self(BTreeSet::new())
     }
 
     /// Generate a blacklist of type parameters that should not have bounds attached.
@@ -105,14 +105,14 @@ impl Blacklist {
     }
 }
 
-impl From<Blacklist> for HashSet<syn::Ident> {
+impl From<Blacklist> for BTreeSet<syn::Ident> {
     fn from(b: Blacklist) -> Self {
         b.0
     }
 }
 
 impl Deref for Blacklist {
-    type Target = HashSet<syn::Ident>;
+    type Target = BTreeSet<syn::Ident>;
 
     fn deref(&self) -> &Self::Target {
         &self.0

minicbor-derive/src/cbor_len.rs

@@ -1,4 +1,4 @@
-use std::collections::HashSet;
+use std::collections::BTreeSet;
 
 use quote::{quote, ToTokens};
 use syn::spanned::Spanned;
@@ -97,7 +97,7 @@ fn on_enum(inp: &mut syn::DeriveInput) -> syn::Result<proc_macro2::TokenStream>
     for ((var, idx), attrs) in data.variants.iter().zip(variants.indices.iter()).zip(&variants.attrs) {
         let fields = Fields::try_from(var.ident.span(), var.fields.iter(), &[attrs, &enum_attrs])?;
         blacklist_len.merge(&fields, &inp.generics, Blacklist::full(Mode::Length, &fields, &inp.generics));
-        blacklist_enc.add(HashSet::from(blacklist_is_nil_params(&inp.generics, &fields)));
+        blacklist_enc.add(BTreeSet::from(blacklist_is_nil_params(&inp.generics, &fields)));
         let con      = &var.ident;
         let encoding = attrs.encoding().unwrap_or(enum_encoding);
         let tag      = on_tag(attrs);

minicbor-derive/src/decode.rs

@@ -1,4 +1,4 @@
-use std::collections::HashSet;
+use std::collections::BTreeSet;
 
 use quote::quote;
 use syn::spanned::Spanned;
@@ -53,7 +53,7 @@ fn on_struct(inp: &mut syn::DeriveInput) -> syn::Result<proc_macro2::TokenStream
     add_bound_to_type_params(Mode::Decode, bound, params, &blacklist, fields.fields().attributes());
 
     // Collect type parameters which require a `Default` bound.
-    let default_types: HashSet<syn::Ident> =
+    let default_types: BTreeSet<syn::Ident> =
         collect_type_params(&inp.generics, fields.fields().chain(fields.skipped()).filter(|f| {
             f.attrs.default() || f.attrs.skip() || f.attrs.skip_if_codec()
         }));
@@ -151,7 +151,7 @@ fn on_enum(inp: &mut syn::DeriveInput) -> syn::Result<proc_macro2::TokenStream>
     let mut decode_blacklist = Blacklist::empty();
     let mut field_attrs = Vec::new();
     let mut default_blacklist = Blacklist::empty();
-    let mut defaults = HashSet::new();
+    let mut defaults = BTreeSet::new();
     let mut default_attrs = Vec::new();
     let mut lifetime = gen_lifetime();
     let mut rows = Vec::new();

minicbor-derive/src/lib.rs

@@ -540,7 +540,7 @@ pub(crate) mod lifetimes;
 pub(crate) mod variants;
 pub(crate) mod blacklist;
 
-use std::collections::HashSet;
+use std::collections::BTreeSet;
 
 /// Derive the `minicbor::Decode` trait for a struct or enum.
 ///
@@ -681,15 +681,15 @@ fn is_decode_bound(bound: &syn::TypeParamBound) -> bool {
 }
 
 /// Traverse all field types and collect all type parameters along the way.
-fn collect_type_params<'a, I>(all: &syn::Generics, fields: I) -> HashSet<syn::Ident>
+fn collect_type_params<'a, I>(all: &syn::Generics, fields: I) -> BTreeSet<syn::Ident>
 where
     I: Iterator<Item = &'a fields::Field>
 {
     use syn::visit::Visit;
 
     struct Collector {
-        all: HashSet<syn::Ident>,
-        found: HashSet<syn::Ident>
+        all: BTreeSet<syn::Ident>,
+        found: BTreeSet<syn::Ident>
     }
 
     impl<'a> Visit<'a> for Collector {
@@ -706,7 +706,7 @@ where
 
     let mut c = Collector {
         all: all.type_params().map(|tp| tp.ident.clone()).collect(),
-        found: HashSet::new()
+        found: BTreeSet::new()
     };
 
     for f in fields {
@@ -720,7 +720,7 @@ fn add_bound_to_type_params<'a, I, A>
     ( mode: Mode
     , bound: syn::TypeParamBound
     , params: I
-    , blacklist: &HashSet<syn::Ident>
+    , blacklist: &BTreeSet<syn::Ident>
     , attrs: A
     )
 where