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Add checks to guard against overflow in iterator methods. #76

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Nov 17, 2019
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Add checks to guard against overflow in iterator methods. #76

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6 changes: 4 additions & 2 deletions strum_macros/src/macros/enum_iter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -83,12 +83,14 @@ pub fn enum_iter_inner(ast: &syn::DeriveInput) -> TokenStream {
#(#arms),*
};

self.idx += 1;
if self.idx < #variant_count {
self.idx += 1;
}
output
}

fn size_hint(&self) -> (usize, Option<usize>) {
let t = #variant_count - self.idx;
let t = if self.idx >= #variant_count { 0 } else { #variant_count - self.idx };
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Looks like this is unnecessary given that the above guarantees this will never underflow.

Additionally, this property is FusedIterator (which is not a requirement for Iterator, and it's the responsibility of the caller to stop calling it). If we choose to have it, then we should also signify that we have it by implementing FusedIterator.

(t, Some(t))
}
}
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3 changes: 3 additions & 0 deletions strum_tests/tests/enum_iter.rs
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Expand Up @@ -63,6 +63,9 @@ fn len_test() {
i.next();

assert_eq!(0, i.len());
i.next();

assert_eq!(0, i.size_hint().1.unwrap());
}

#[test]
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