Make LonghandId just be the discriminants of PropertyDeclaration 🐉🐲

This relies on the fact that `#[repr(u16)]` on enums ensure the discriminant will
be the very first field of the enum value. This has always been the case, but it
has been formally defined only since https://github.com/rust-lang/rfcs/pull/2195.

https://bugzilla.mozilla.org/show_bug.cgi?id=1428285
This commit is contained in:
Anthony Ramine 2018-02-05 20:44:30 +01:00
parent 1ec5164900
commit 42ea822edf

View file

@ -203,6 +203,8 @@ pub mod animated_properties {
}
<%
from itertools import groupby
variants = []
for property in data.longhands:
if property.predefined_type and not property.is_vector and not property.is_gecko_size_type_hack:
@ -216,7 +218,33 @@ pub mod animated_properties {
"type": ty,
"doc": "`" + property.name + "`",
})
variants += [
groups = {}
keyfunc = lambda x: x["type"]
sortkeys = {}
for ty, group in groupby(sorted(variants, key=keyfunc), keyfunc):
group = [v["name"] for v in group]
groups[ty] = group
for v in group:
if len(group) == 1:
sortkeys[v] = (1, v, "")
else:
sortkeys[v] = (len(group), ty, v)
variants.sort(key=lambda x: sortkeys[x["name"]])
# It is extremely important to sort the `data.longhands` array here so
# that it is in the same order as `variants`, for `LonghandId` and
# `PropertyDeclarationId` to coincide.
data.longhands.sort(key=lambda x: sortkeys[x.camel_case])
%>
// WARNING: It is *really* important for the variants of `LonghandId`
// and `PropertyDeclaration` to be defined in the exact same order,
// with the exception of `CSSWideKeyword`, `WithVariables` and `Custom`,
// which don't exist in `LonghandId`.
<%
extra = [
{
"name": "CSSWideKeyword",
"type": "WideKeywordDeclaration",
@ -233,6 +261,9 @@ pub mod animated_properties {
"doc": "A custom property declaration.",
},
]
for v in extra:
variants.append(v)
groups[v["type"]] = [v["name"]]
%>
/// Servo's representation for a property declaration.
@ -246,15 +277,6 @@ pub enum PropertyDeclaration {
% endfor
}
<%
from itertools import groupby
groups = {}
keyfunc = lambda x: x["type"]
for ty, group in groupby(sorted(variants, key=keyfunc), keyfunc):
groups[ty] = list(group)
%>
impl Clone for PropertyDeclaration {
#[inline]
fn clone(&self) -> Self {
@ -269,11 +291,11 @@ impl Clone for PropertyDeclaration {
match *self {
% for ty, variants in groups.iteritems():
% if len(variants) == 1:
${variants[0]["name"]}(ref value) => {
${variants[0]["name"]}(value.clone())
${variants[0]}(ref value) => {
${variants[0]}(value.clone())
}
% else:
${" | ".join("{}(ref value)".format(v["name"]) for v in variants)} => {
${" | ".join("{}(ref value)".format(v) for v in variants)} => {
unsafe {
let mut out = ManuallyDrop::new(mem::uninitialized());
ptr::write(
@ -376,7 +398,7 @@ impl<'a> Iterator for LonghandIdSetIterator<'a> {
return None;
}
let id: LonghandId = unsafe { mem::transmute(self.cur as ${"u16" if product == "gecko" else "u8"}) };
let id: LonghandId = unsafe { mem::transmute(self.cur as u16) };
self.cur += 1;
if self.longhands.contains(id) {
@ -583,6 +605,7 @@ bitflags! {
/// An identifier for a given longhand property.
#[derive(Clone, Copy, Eq, Hash, MallocSizeOf, PartialEq)]
#[repr(u16)]
pub enum LonghandId {
% for i, property in enumerate(data.longhands):
/// ${property.name}
@ -1623,23 +1646,16 @@ impl PropertyDeclaration {
}
_ => {}
}
let longhand_id = match *self {
// This is just fine because PropertyDeclarationId and LonghandId
// have corresponding discriminants.
let id = unsafe { *(self as *const _ as *const LonghandId) };
debug_assert_eq!(id, match *self {
% for property in data.longhands:
PropertyDeclaration::${property.camel_case}(..) => {
LonghandId::${property.camel_case}
}
PropertyDeclaration::${property.camel_case}(..) => LonghandId::${property.camel_case},
% endfor
PropertyDeclaration::CSSWideKeyword(..) |
PropertyDeclaration::WithVariables(..) |
PropertyDeclaration::Custom(..) => {
debug_assert!(false, "unreachable");
// This value is never used, but having an expression of the same "shape"
// as for other variants helps the optimizer compile this `match` expression
// to a lookup table.
LonghandId::BackgroundColor
}
};
PropertyDeclarationId::Longhand(longhand_id)
_ => id,
});
PropertyDeclarationId::Longhand(id)
}
fn with_variables_from_shorthand(&self, shorthand: ShorthandId) -> Option< &str> {