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Merge build_enum_match_tuple into expand_enum_method_body.

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Because the latter just calls the former.

The commit also updates some details in a comment.
This commit is contained in:
Nicholas Nethercote 2022-06-22 15:26:47 +10:00
parent 00207ead61
commit e7396685a1
1 changed files with 20 additions and 52 deletions
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72
compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
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@ -1126,75 +1126,43 @@ impl<'a> MethodDef<'a> {
/// A1,
/// A2(i32)
/// }
///
/// // is equivalent to
///
/// impl PartialEq for A {
/// ```
/// is equivalent to:
/// ```
/// impl ::core::cmp::PartialEq for A {
/// #[inline]
/// fn eq(&self, other: &A) -> bool {
/// use A::*;
/// match (&*self, &*other) {
/// (&A1, &A1) => true,
/// (&A2(ref self_0),
/// &A2(ref __arg_1_0)) => (*self_0).eq(&(*__arg_1_0)),
/// _ => {
/// let __self_vi = match *self { A1 => 0, A2(..) => 1 };
/// let __arg_1_vi = match *other { A1 => 0, A2(..) => 1 };
/// false
/// {
/// let __self_vi = ::core::intrinsics::discriminant_value(&*self);
/// let __arg_1_vi = ::core::intrinsics::discriminant_value(&*other);
/// if true && __self_vi == __arg_1_vi {
/// match (&*self, &*other) {
/// (&A::A2(ref __self_0), &A::A2(ref __arg_1_0)) =>
/// (*__self_0) == (*__arg_1_0),
/// _ => true,
/// }
/// } else {
/// false // catch-all handler
/// }
/// }
/// }
/// }
/// ```
///
/// (Of course `__self_vi` and `__arg_1_vi` are unused for
/// `PartialEq`, and those subcomputations will hopefully be removed
/// as their results are unused. The point of `__self_vi` and
/// `__arg_1_vi` is for `PartialOrd`; see #15503.)
fn expand_enum_method_body<'b>(
&self,
cx: &mut ExtCtxt<'_>,
trait_: &TraitDef<'b>,
enum_def: &'b EnumDef,
type_ident: Ident,
self_args: Vec<P<Expr>>,
nonself_args: &[P<Expr>],
) -> P<Expr> {
self.build_enum_match_tuple(cx, trait_, enum_def, type_ident, self_args, nonself_args)
}
/// Creates a match for a tuple of all `self_args`, where either all
/// variants match, or it falls into a catch-all for when one variant
/// does not match.
///
/// There are N + 1 cases because is a case for each of the N
/// variants where all of the variants match, and one catch-all for
/// when one does not match.
///
/// As an optimization we generate code which checks whether all variants
/// match first which makes llvm see that C-like enums can be compiled into
/// a simple equality check (for PartialEq).
///
/// The catch-all handler is provided access the variant index values
/// for each of the self-args, carried in precomputed variables.
/// ```{.text}
/// let __self0_vi = std::intrinsics::discriminant_value(&self);
/// let __self1_vi = std::intrinsics::discriminant_value(&arg1);
/// let __self2_vi = std::intrinsics::discriminant_value(&arg2);
///
/// if __self0_vi == __self1_vi && __self0_vi == __self2_vi && ... {
/// match (...) {
/// (Variant1, Variant1, ...) => Body1
/// (Variant2, Variant2, ...) => Body2,
/// ...
/// _ => ::core::intrinsics::unreachable()
/// }
/// }
/// else {
/// ... // catch-all remainder can inspect above variant index values.
/// }
/// ```
fn build_enum_match_tuple<'b>(
fn expand_enum_method_body<'b>(
&self,
cx: &mut ExtCtxt<'_>,
trait_: &TraitDef<'b>,