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simplify inject_impl_of_structural_trait #115891

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Sep 18, 2023
Merged

simplify inject_impl_of_structural_trait #115891

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17 changes: 14 additions & 3 deletions compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,20 @@ pub fn expand_deriving_eq(
is_const: bool,
) {
let span = cx.with_def_site_ctxt(span);

let structural_trait_def = TraitDef {
span,
path: path_std!(marker::StructuralEq),
skip_path_as_bound: true, // crucial!
needs_copy_as_bound_if_packed: false,
additional_bounds: Vec::new(),
supports_unions: true,
methods: Vec::new(),
associated_types: Vec::new(),
is_const: false,
};
structural_trait_def.expand(cx, mitem, item, push);

let trait_def = TraitDef {
span,
path: path_std!(cmp::Eq),
Expand All @@ -44,9 +58,6 @@ pub fn expand_deriving_eq(
associated_types: Vec::new(),
is_const,
};

super::inject_impl_of_structural_trait(cx, span, item, path_std!(marker::StructuralEq), push);

trait_def.expand_ext(cx, mitem, item, push, true)
}

Expand Down
19 changes: 13 additions & 6 deletions compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -72,13 +72,20 @@ pub fn expand_deriving_partial_eq(
BlockOrExpr::new_expr(expr)
}

super::inject_impl_of_structural_trait(
cx,
let structural_trait_def = TraitDef {
span,
item,
path_std!(marker::StructuralPartialEq),
push,
);
path: path_std!(marker::StructuralPartialEq),
skip_path_as_bound: true, // crucial!
needs_copy_as_bound_if_packed: false,
additional_bounds: Vec::new(),
// We really don't support unions, but that's already checked by the impl generated below;
// a second check here would lead to redundant error messages.
supports_unions: true,
methods: Vec::new(),
associated_types: Vec::new(),
is_const: false,
};
structural_trait_def.expand(cx, mitem, item, push);

// No need to generate `ne`, the default suffices, and not generating it is
// faster.
Expand Down
22 changes: 13 additions & 9 deletions compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -711,7 +711,9 @@ impl<'a> TraitDef<'a> {
.collect();

// Require the current trait.
bounds.push(cx.trait_bound(trait_path.clone(), self.is_const));
if !self.skip_path_as_bound {
bounds.push(cx.trait_bound(trait_path.clone(), self.is_const));
}

// Add a `Copy` bound if required.
if is_packed && self.needs_copy_as_bound_if_packed {
Expand All @@ -722,15 +724,17 @@ impl<'a> TraitDef<'a> {
));
}

let predicate = ast::WhereBoundPredicate {
span: self.span,
bound_generic_params: field_ty_param.bound_generic_params,
bounded_ty: field_ty_param.ty,
bounds,
};
if !bounds.is_empty() {
let predicate = ast::WhereBoundPredicate {
span: self.span,
bound_generic_params: field_ty_param.bound_generic_params,
bounded_ty: field_ty_param.ty,
bounds,
};

let predicate = ast::WherePredicate::BoundPredicate(predicate);
where_clause.predicates.push(predicate);
let predicate = ast::WherePredicate::BoundPredicate(predicate);
where_clause.predicates.push(predicate);
}
}
}
}
Expand Down
98 changes: 2 additions & 96 deletions compiler/rustc_builtin_macros/src/deriving/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,9 @@

use rustc_ast as ast;
use rustc_ast::ptr::P;
use rustc_ast::{GenericArg, Impl, ItemKind, MetaItem};
use rustc_ast::{GenericArg, MetaItem};
use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, MultiItemModifier};
use rustc_span::symbol::{sym, Ident, Symbol};
use rustc_span::symbol::{sym, Symbol};
use rustc_span::Span;
use thin_vec::{thin_vec, ThinVec};

Expand Down Expand Up @@ -116,100 +116,6 @@ fn call_unreachable(cx: &ExtCtxt<'_>, span: Span) -> P<ast::Expr> {
}))
}

// Injects `impl<...> Structural for ItemType<...> { }`. In particular,
// does *not* add `where T: Structural` for parameters `T` in `...`.
// (That's the main reason we cannot use TraitDef here.)
fn inject_impl_of_structural_trait(
cx: &mut ExtCtxt<'_>,
span: Span,
item: &Annotatable,
structural_path: generic::ty::Path,
push: &mut dyn FnMut(Annotatable),
) {
let Annotatable::Item(item) = item else {
unreachable!();
};

let generics = match &item.kind {
ItemKind::Struct(_, generics) | ItemKind::Enum(_, generics) => generics,
// Do not inject `impl Structural for Union`. (`PartialEq` does not
// support unions, so we will see error downstream.)
ItemKind::Union(..) => return,
_ => unreachable!(),
};

// Create generics param list for where clauses and impl headers
let mut generics = generics.clone();

let ctxt = span.ctxt();

// Create the type of `self`.
//
// in addition, remove defaults from generic params (impls cannot have them).
let self_params: Vec<_> = generics
.params
.iter_mut()
.map(|param| match &mut param.kind {
ast::GenericParamKind::Lifetime => ast::GenericArg::Lifetime(
cx.lifetime(param.ident.span.with_ctxt(ctxt), param.ident),
),
ast::GenericParamKind::Type { default } => {
*default = None;
ast::GenericArg::Type(cx.ty_ident(param.ident.span.with_ctxt(ctxt), param.ident))
}
ast::GenericParamKind::Const { ty: _, kw_span: _, default } => {
*default = None;
ast::GenericArg::Const(
cx.const_ident(param.ident.span.with_ctxt(ctxt), param.ident),
)
}
})
.collect();

let type_ident = item.ident;

let trait_ref = cx.trait_ref(structural_path.to_path(cx, span, type_ident, &generics));
let self_type = cx.ty_path(cx.path_all(span, false, vec![type_ident], self_params));

// It would be nice to also encode constraint `where Self: Eq` (by adding it
// onto `generics` cloned above). Unfortunately, that strategy runs afoul of
// rust-lang/rust#48214. So we perform that additional check in the compiler
// itself, instead of encoding it here.

// Keep the lint and stability attributes of the original item, to control
// how the generated implementation is linted.
let mut attrs = ast::AttrVec::new();
attrs.extend(
item.attrs
.iter()
.filter(|a| {
[sym::allow, sym::warn, sym::deny, sym::forbid, sym::stable, sym::unstable]
.contains(&a.name_or_empty())
})
.cloned(),
);
// Mark as `automatically_derived` to avoid some silly lints.
attrs.push(cx.attr_word(sym::automatically_derived, span));

let newitem = cx.item(
span,
Ident::empty(),
attrs,
ItemKind::Impl(Box::new(Impl {
unsafety: ast::Unsafe::No,
polarity: ast::ImplPolarity::Positive,
defaultness: ast::Defaultness::Final,
constness: ast::Const::No,
generics,
of_trait: Some(trait_ref),
self_ty: self_type,
items: ThinVec::new(),
})),
);

push(Annotatable::Item(newitem));
}

fn assert_ty_bounds(
cx: &mut ExtCtxt<'_>,
stmts: &mut ThinVec<ast::Stmt>,
Expand Down
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