From e1cef3462fd87b93cf1576803f993c149c8510c9 Mon Sep 17 00:00:00 2001
From: Roland Fredenhagen <dev@modprog.de>
Date: Fri, 1 Sep 2023 14:45:53 +0200
Subject: [PATCH] fixup! Add `TryFrom` to convert repr to enum

cleanup
---
 impl/src/parsing.rs  |  4 ++--
 impl/src/try_from.rs |  7 +++++--
 tests/try_from.rs    | 41 +++++++++++++++++++++++++++++++++--------
 3 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/impl/src/parsing.rs b/impl/src/parsing.rs
index 42b66376..dfbd21e0 100644
--- a/impl/src/parsing.rs
+++ b/impl/src/parsing.rs
@@ -245,8 +245,8 @@ pub fn seq<const N: usize>(
     move |c| {
         parsers
             .iter_mut()
-            .fold(Some((TokenStream::new(), c)), |out, parser| {
-                let (mut out, mut c) = out?;
+            .try_fold((TokenStream::new(), c), |out, parser| {
+                let (mut out, mut c) = out;
                 let (stream, cursor) = parser(c)?;
                 out.extend(stream);
                 c = cursor;
diff --git a/impl/src/try_from.rs b/impl/src/try_from.rs
index 809863e7..d4b85c19 100644
--- a/impl/src/try_from.rs
+++ b/impl/src/try_from.rs
@@ -92,7 +92,7 @@ impl<'a> Expansion<'a> {
 
         let repr = &self.repr.0;
 
-        let mut last_discriminant = quote!(0);
+        let mut last_discriminant = quote! {0};
         let mut inc = 0usize;
         let (consts, (discriminants, variants)): (
             Vec<Ident>,
@@ -115,7 +115,10 @@ impl<'a> Expansion<'a> {
                         let inc = Literal::usize_unsuffixed(inc);
                         fields.is_empty().then_some((
                             format_ident!("__DISCRIMINANT_{ident}"),
-                            (quote!(#last_discriminant + #inc), quote!(#ident #fields)),
+                            (
+                                quote! {#last_discriminant + #inc},
+                                quote! {#ident #fields},
+                            ),
                         ))
                     };
                     inc += 1;
diff --git a/tests/try_from.rs b/tests/try_from.rs
index afe8e341..5e032c88 100644
--- a/tests/try_from.rs
+++ b/tests/try_from.rs
@@ -7,17 +7,42 @@ use derive_more::TryFrom;
 #[repr(i16)]
 enum Enum {
     A,
-    Discriminant = 5,
-    Field(usize),
-    Empty {},
-    FieldWithDiscriminant(u8, i64) = -14,
-    EmptyTuple(),
+    B = -21,
+    C,
+    D,
 }
 
 #[test]
 fn test() {
     assert_eq!(Enum::A, Enum::try_from(0).unwrap());
-    assert_eq!(Enum::Discriminant, Enum::try_from(5).unwrap());
-    assert_eq!(Enum::Empty {}, Enum::try_from(7).unwrap());
-    assert_eq!(Enum::EmptyTuple(), Enum::try_from(-13).unwrap());
+    assert_eq!(Enum::B, Enum::try_from(-21).unwrap());
+    assert_eq!(Enum::C, Enum::try_from(-20).unwrap());
+    assert_eq!(Enum::D, Enum::try_from(-19).unwrap());
+    assert!(Enum::try_from(-1).is_err());
+}
+
+#[rustversion::since(1.66)]
+mod discriminants_on_enum_with_fields {
+    use super::*;
+
+    #[derive(TryFrom, Clone, Copy, Debug, Eq, PartialEq)]
+    #[repr(i16)]
+    enum Enum {
+        A,
+        Discriminant = 5,
+        Field(usize),
+        Empty {},
+        FieldWithDiscriminant(u8, i64) = -14,
+        EmptyTuple(),
+    }
+
+    #[test]
+    fn test() {
+        assert_eq!(Enum::A, Enum::try_from(0).unwrap());
+        assert_eq!(Enum::Discriminant, Enum::try_from(5).unwrap());
+        assert!(Enum::try_from(6).is_err());
+        assert_eq!(Enum::Empty {}, Enum::try_from(7).unwrap());
+        assert!(Enum::try_from(-14).is_err());
+        assert_eq!(Enum::EmptyTuple(), Enum::try_from(-13).unwrap());
+    }
 }