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Make Ord and PartialOrd opt-out in newtype_index #94404

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merged 1 commit into from
Mar 4, 2022
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Make Ord and PartialOrd opt-out in newtype_index #94404

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70 changes: 46 additions & 24 deletions compiler/rustc_macros/src/newtype.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ mod kw {
syn::custom_keyword!(MAX);
syn::custom_keyword!(ENCODABLE);
syn::custom_keyword!(custom);
syn::custom_keyword!(ORD_IMPL);
}

#[derive(Debug)]
Expand Down Expand Up @@ -42,6 +43,7 @@ impl Parse for Newtype {
let mut max = None;
let mut consts = Vec::new();
let mut encodable = true;
let mut ord = true;

// Parse an optional trailing comma
let try_comma = || -> Result<()> {
Expand Down Expand Up @@ -99,13 +101,20 @@ impl Parse for Newtype {
encodable = false;
continue;
}
if body.lookahead1().peek(kw::ORD_IMPL) {
body.parse::<kw::ORD_IMPL>()?;
body.parse::<Token![=]>()?;
body.parse::<kw::custom>()?;
ord = false;
continue;
}

// We've parsed everything that the user provided, so we're done
if body.is_empty() {
break;
}

// Otherwise, we are parsng a user-defined constant
// Otherwise, we are parsing a user-defined constant
let const_attrs = body.call(Attribute::parse_outer)?;
body.parse::<Token![const]>()?;
let const_name: Ident = body.parse()?;
Expand Down Expand Up @@ -137,6 +146,40 @@ impl Parse for Newtype {
quote! {}
};

if ord {
derive_paths.push(parse_quote!(Ord));
derive_paths.push(parse_quote!(PartialOrd));
}

let step = if ord {
quote! {
impl ::std::iter::Step for #name {
#[inline]
fn steps_between(start: &Self, end: &Self) -> Option<usize> {
<usize as ::std::iter::Step>::steps_between(
&Self::index(*start),
&Self::index(*end),
)
}

#[inline]
fn forward_checked(start: Self, u: usize) -> Option<Self> {
Self::index(start).checked_add(u).map(Self::from_usize)
}

#[inline]
fn backward_checked(start: Self, u: usize) -> Option<Self> {
Self::index(start).checked_sub(u).map(Self::from_usize)
}
}

// Safety: The implementation of `Step` upholds all invariants.
unsafe impl ::std::iter::TrustedStep for #name {}
}
} else {
quote! {}
};

let debug_impl = match debug_format {
DebugFormat::Custom => quote! {},
DebugFormat::Format(format) => {
Expand All @@ -152,7 +195,7 @@ impl Parse for Newtype {

Ok(Self(quote! {
#(#attrs)*
#[derive(Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, #(#derive_paths),*)]
#[derive(Clone, Copy, PartialEq, Eq, Hash, #(#derive_paths),*)]
#[rustc_layout_scalar_valid_range_end(#max)]
#vis struct #name {
private: u32,
Expand Down Expand Up @@ -247,28 +290,7 @@ impl Parse for Newtype {
}
}

impl ::std::iter::Step for #name {
#[inline]
fn steps_between(start: &Self, end: &Self) -> Option<usize> {
<usize as ::std::iter::Step>::steps_between(
&Self::index(*start),
&Self::index(*end),
)
}

#[inline]
fn forward_checked(start: Self, u: usize) -> Option<Self> {
Self::index(start).checked_add(u).map(Self::from_usize)
}

#[inline]
fn backward_checked(start: Self, u: usize) -> Option<Self> {
Self::index(start).checked_sub(u).map(Self::from_usize)
}
}

// Safety: The implementation of `Step` upholds all invariants.
unsafe impl ::std::iter::TrustedStep for #name {}
#step

impl From<#name> for u32 {
#[inline]
Expand Down