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Added the ability to use #[default] and added Default in the derive trait #3

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Merged
merged 5 commits into from
Nov 21, 2023
Merged

Added the ability to use #[default] and added Default in the derive trait #3

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ef630f7
added default
Nov 18, 2023
f656468
Forgot the commas last time
Nov 18, 2023
117c5e9
Made defaults work and added tests
Nov 18, 2023
dc94440
Move check_for_defaults call to make triples immut
Nov 21, 2023
4ec558f
Suppress unused variable warning
Nov 21, 2023
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24 changes: 23 additions & 1 deletion src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -187,6 +187,25 @@ fn concat<T>(mut v1: Vec<T>, mut v2: Vec<T>) -> Vec<T> {
v1
}

fn check_for_default(triples: &mut Vec<(TokenStream, Ident, TokenTree)>) {
let mut default_position: Option<usize> = None;
for (attributes, _variant_name, variant_value) in triples.into_iter() {
if attributes.to_string().contains("default") {
if default_position.is_some() {
// error!("Multiple variants marked as default");
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Did you mean to get rid of this if statement? I'm not 100% sure, but I would assume that derive(Default) itself will trigger an error if it sees multiple defaults.

Also it looks like we don't actually need to do anything with the default variant, so you probably don't need the default_position variable.

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So, um, it kinda triggers a error

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@math4tots math4tots Nov 21, 2023 •
edited
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Got it. Looks like someone opened a pr to fix the error message here in response to the issue you opened.

Still, I suppose I'd prefer it if we propagated the error, because even after that pr lands, I'm assuming it might take a little while for that fix to be in a release.

Also, I just realized, as you probably noticed, we can't just use the error! macro here because your function doesn't return a TokenStream. I think the "correct" thing to do here would be to return Result<(), String> from check_for_default and check for an error when you call it, then call error! from there.

}
default_position = Some(variant_value.to_string().parse::<usize>().unwrap());
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You could do a return here instead. And if you do, you won't need to do if !default_position.is_some() below.

}
}
if !default_position.is_some() {
// No default specified, so we'll just use the first variant
triples[0].0.extend(vec![
punct_token('#'),
bracket_token(vec![ident_token("default")]).into(),
]);
}
}

#[proc_macro]
pub fn primitive_enum(tokens: TokenStream) -> TokenStream {
let mut iter = tokens.into_iter();
Expand Down Expand Up @@ -302,6 +321,7 @@ pub fn primitive_enum(tokens: TokenStream) -> TokenStream {
offset += 1;
triples.push((variant_attributes, variant_name, value));
}
check_for_default(&mut triples); // make sure there's a default, if the user didn't specify one
triples
};

Expand All @@ -322,7 +342,6 @@ pub fn primitive_enum(tokens: TokenStream) -> TokenStream {
ident_token("repr"),
paren_token(repr_type.clone()),
]));

// #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
out.push(punct_token('#'));
out.push(bracket_token(vec![
Expand All @@ -339,8 +358,11 @@ pub fn primitive_enum(tokens: TokenStream) -> TokenStream {
ident_token("Eq"),
punct_token(','),
ident_token("Hash"),
punct_token(','),
ident_token("Default"),
]),
]));

out.push(ident_token("pub"));
out.push(ident_token("enum"));
out.push(TokenTree::Ident(enum_identifier.clone()));
Expand Down
18 changes: 18 additions & 0 deletions tests/sample.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -196,4 +196,22 @@ mod tests {
assert_eq!(MarkerType::from_name("Markerboxes"), Some(MarkerType::Markerboxes));
assert_eq!(MarkerType::from_name("Markerpitlane"), Some(MarkerType::Markerpitlane));
}

primitive_enum! { MarkerType2 u32 ;
A, // 0
B, // 1
C, // 2
D, // 3
E, // 4
#[default]
F, // 5
G, // 6
}

#[test]
fn test_enum_default() {
assert_eq!(MarkerType2::default(), MarkerType2::F);
assert_eq!(MarkerType2::from(0), Some(MarkerType2::A));
assert_eq!(MyEnum::default(), MyEnum::A);
}
}