1 files changed, 208 insertions, 0 deletions
diff --git a/compiler/rustc_builtin_macros/src/deriving/mod.rs b/compiler/rustc_builtin_macros/src/deriving/mod.rs
new file mode 100644
index 000000000..c1ca089da
--- /dev/null
+++ b/compiler/rustc_builtin_macros/src/deriving/mod.rs
@@ -0,0 +1,208 @@
+//! The compiler code necessary to implement the `#[derive]` extensions.
+
+use rustc_ast as ast;
+use rustc_ast::ptr::P;
+use rustc_ast::{GenericArg, Impl, ItemKind, MetaItem};
+use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, MultiItemModifier};
+use rustc_span::symbol::{sym, Ident, Symbol};
+use rustc_span::Span;
+
+macro path_local($x:ident) {
+    generic::ty::Path::new_local(sym::$x)
+}
+
+macro pathvec_std($($rest:ident)::+) {{
+    vec![ $( sym::$rest ),+ ]
+}}
+
+macro path_std($($x:tt)*) {
+    generic::ty::Path::new( pathvec_std!( $($x)* ) )
+}
+
+pub mod bounds;
+pub mod clone;
+pub mod debug;
+pub mod decodable;
+pub mod default;
+pub mod encodable;
+pub mod hash;
+
+#[path = "cmp/eq.rs"]
+pub mod eq;
+#[path = "cmp/ord.rs"]
+pub mod ord;
+#[path = "cmp/partial_eq.rs"]
+pub mod partial_eq;
+#[path = "cmp/partial_ord.rs"]
+pub mod partial_ord;
+
+pub mod generic;
+
+pub(crate) struct BuiltinDerive(
+    pub(crate) fn(&mut ExtCtxt<'_>, Span, &MetaItem, &Annotatable, &mut dyn FnMut(Annotatable)),
+);
+
+impl MultiItemModifier for BuiltinDerive {
+    fn expand(
+        &self,
+        ecx: &mut ExtCtxt<'_>,
+        span: Span,
+        meta_item: &MetaItem,
+        item: Annotatable,
+    ) -> ExpandResult<Vec<Annotatable>, Annotatable> {
+        // FIXME: Built-in derives often forget to give spans contexts,
+        // so we are doing it here in a centralized way.
+        let span = ecx.with_def_site_ctxt(span);
+        let mut items = Vec::new();
+        match item {
+            Annotatable::Stmt(stmt) => {
+                if let ast::StmtKind::Item(item) = stmt.into_inner().kind {
+                    (self.0)(ecx, span, meta_item, &Annotatable::Item(item), &mut |a| {
+                        // Cannot use 'ecx.stmt_item' here, because we need to pass 'ecx'
+                        // to the function
+                        items.push(Annotatable::Stmt(P(ast::Stmt {
+                            id: ast::DUMMY_NODE_ID,
+                            kind: ast::StmtKind::Item(a.expect_item()),
+                            span,
+                        })));
+                    });
+                } else {
+                    unreachable!("should have already errored on non-item statement")
+                }
+            }
+            _ => {
+                (self.0)(ecx, span, meta_item, &item, &mut |a| items.push(a));
+            }
+        }
+        ExpandResult::Ready(items)
+    }
+}
+
+/// Constructs an expression that calls an intrinsic
+fn call_intrinsic(
+    cx: &ExtCtxt<'_>,
+    span: Span,
+    intrinsic: Symbol,
+    args: Vec<P<ast::Expr>>,
+) -> P<ast::Expr> {
+    let span = cx.with_def_site_ctxt(span);
+    let path = cx.std_path(&[sym::intrinsics, intrinsic]);
+    cx.expr_call_global(span, path, args)
+}
+
+/// Constructs an expression that calls the `unreachable` intrinsic.
+fn call_unreachable(cx: &ExtCtxt<'_>, span: Span) -> P<ast::Expr> {
+    let span = cx.with_def_site_ctxt(span);
+    let path = cx.std_path(&[sym::intrinsics, sym::unreachable]);
+    let call = cx.expr_call_global(span, path, vec![]);
+
+    cx.expr_block(P(ast::Block {
+        stmts: vec![cx.stmt_expr(call)],
+        id: ast::DUMMY_NODE_ID,
+        rules: ast::BlockCheckMode::Unsafe(ast::CompilerGenerated),
+        span,
+        tokens: None,
+        could_be_bare_literal: false,
+    }))
+}
+
+// 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(ref item) = *item else {
+        unreachable!();
+    };
+
+    let generics = match item.kind {
+        ItemKind::Struct(_, ref generics) | ItemKind::Enum(_, ref 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();
+
+    // 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(span, param.ident))
+            }
+            ast::GenericParamKind::Type { default } => {
+                *default = None;
+                ast::GenericArg::Type(cx.ty_ident(span, param.ident))
+            }
+            ast::GenericParamKind::Const { ty: _, kw_span: _, default } => {
+                *default = None;
+                ast::GenericArg::Const(cx.const_ident(span, 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 = Vec::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(),
+    );
+
+    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: Vec::new(),
+        })),
+    );
+
+    push(Annotatable::Item(newitem));
+}
+
+fn assert_ty_bounds(
+    cx: &mut ExtCtxt<'_>,
+    stmts: &mut Vec<ast::Stmt>,
+    ty: P<ast::Ty>,
+    span: Span,
+    assert_path: &[Symbol],
+) {
+    // Generate statement `let _: assert_path<ty>;`.
+    let span = cx.with_def_site_ctxt(span);
+    let assert_path = cx.path_all(span, true, cx.std_path(assert_path), vec![GenericArg::Type(ty)]);
+    stmts.push(cx.stmt_let_type_only(span, cx.ty_path(assert_path)));
+}