use crate::deriving::generic::ty::*; use crate::deriving::generic::*; use crate::deriving::path_std; use rustc_ast::{self as ast, Generics, ItemKind, MetaItem, VariantData}; use rustc_data_structures::fx::FxHashSet; use rustc_expand::base::{Annotatable, ExtCtxt}; use rustc_span::symbol::{kw, sym, Ident}; use rustc_span::Span; use thin_vec::{thin_vec, ThinVec}; pub fn expand_deriving_clone( cx: &mut ExtCtxt<'_>, span: Span, mitem: &MetaItem, item: &Annotatable, push: &mut dyn FnMut(Annotatable), is_const: bool, ) { // The simple form is `fn clone(&self) -> Self { *self }`, possibly with // some additional `AssertParamIsClone` assertions. // // We can use the simple form if either of the following are true. // - The type derives Copy and there are no generic parameters. (If we // used the simple form with generics, we'd have to bound the generics // with Clone + Copy, and then there'd be no Clone impl at all if the // user fills in something that is Clone but not Copy. After // specialization we can remove this no-generics limitation.) // - The item is a union. (Unions with generic parameters still can derive // Clone because they require Copy for deriving, Clone alone is not // enough. Whether Clone is implemented for fields is irrelevant so we // don't assert it.) let bounds; let substructure; let is_simple; match item { Annotatable::Item(annitem) => match &annitem.kind { ItemKind::Struct(_, Generics { params, .. }) | ItemKind::Enum(_, Generics { params, .. }) => { let container_id = cx.current_expansion.id.expn_data().parent.expect_local(); let has_derive_copy = cx.resolver.has_derive_copy(container_id); if has_derive_copy && !params .iter() .any(|param| matches!(param.kind, ast::GenericParamKind::Type { .. })) { bounds = vec![]; is_simple = true; substructure = combine_substructure(Box::new(|c, s, sub| { cs_clone_simple("Clone", c, s, sub, false) })); } else { bounds = vec![]; is_simple = false; substructure = combine_substructure(Box::new(|c, s, sub| cs_clone("Clone", c, s, sub))); } } ItemKind::Union(..) => { bounds = vec![Path(path_std!(marker::Copy))]; is_simple = true; substructure = combine_substructure(Box::new(|c, s, sub| { cs_clone_simple("Clone", c, s, sub, true) })); } _ => cx.span_bug(span, "`#[derive(Clone)]` on wrong item kind"), }, _ => cx.span_bug(span, "`#[derive(Clone)]` on trait item or impl item"), } let trait_def = TraitDef { span, path: path_std!(clone::Clone), skip_path_as_bound: false, needs_copy_as_bound_if_packed: true, additional_bounds: bounds, supports_unions: true, methods: vec![MethodDef { name: sym::clone, generics: Bounds::empty(), explicit_self: true, nonself_args: Vec::new(), ret_ty: Self_, attributes: thin_vec![cx.attr_word(sym::inline, span)], fieldless_variants_strategy: FieldlessVariantsStrategy::Default, combine_substructure: substructure, }], associated_types: Vec::new(), is_const, }; trait_def.expand_ext(cx, mitem, item, push, is_simple) } fn cs_clone_simple( name: &str, cx: &mut ExtCtxt<'_>, trait_span: Span, substr: &Substructure<'_>, is_union: bool, ) -> BlockOrExpr { let mut stmts = ThinVec::new(); let mut seen_type_names = FxHashSet::default(); let mut process_variant = |variant: &VariantData| { for field in variant.fields() { // This basic redundancy checking only prevents duplication of // assertions like `AssertParamIsClone` where the type is a // simple name. That's enough to get a lot of cases, though. if let Some(name) = field.ty.kind.is_simple_path() && !seen_type_names.insert(name) { // Already produced an assertion for this type. } else { // let _: AssertParamIsClone; super::assert_ty_bounds( cx, &mut stmts, field.ty.clone(), field.span, &[sym::clone, sym::AssertParamIsClone], ); } } }; if is_union { // Just a single assertion for unions, that the union impls `Copy`. // let _: AssertParamIsCopy; let self_ty = cx.ty_path(cx.path_ident(trait_span, Ident::with_dummy_span(kw::SelfUpper))); super::assert_ty_bounds( cx, &mut stmts, self_ty, trait_span, &[sym::clone, sym::AssertParamIsCopy], ); } else { match *substr.fields { StaticStruct(vdata, ..) => { process_variant(vdata); } StaticEnum(enum_def, ..) => { for variant in &enum_def.variants { process_variant(&variant.data); } } _ => cx.span_bug( trait_span, format!("unexpected substructure in simple `derive({name})`"), ), } } BlockOrExpr::new_mixed(stmts, Some(cx.expr_deref(trait_span, cx.expr_self(trait_span)))) } fn cs_clone( name: &str, cx: &mut ExtCtxt<'_>, trait_span: Span, substr: &Substructure<'_>, ) -> BlockOrExpr { let ctor_path; let all_fields; let fn_path = cx.std_path(&[sym::clone, sym::Clone, sym::clone]); let subcall = |cx: &mut ExtCtxt<'_>, field: &FieldInfo| { let args = thin_vec![field.self_expr.clone()]; cx.expr_call_global(field.span, fn_path.clone(), args) }; let vdata; match substr.fields { Struct(vdata_, af) => { ctor_path = cx.path(trait_span, vec![substr.type_ident]); all_fields = af; vdata = *vdata_; } EnumMatching(.., variant, af) => { ctor_path = cx.path(trait_span, vec![substr.type_ident, variant.ident]); all_fields = af; vdata = &variant.data; } EnumTag(..) | AllFieldlessEnum(..) => { cx.span_bug(trait_span, format!("enum tags in `derive({name})`",)) } StaticEnum(..) | StaticStruct(..) => { cx.span_bug(trait_span, format!("associated function in `derive({name})`")) } } let expr = match *vdata { VariantData::Struct(..) => { let fields = all_fields .iter() .map(|field| { let Some(ident) = field.name else { cx.span_bug( trait_span, format!("unnamed field in normal struct in `derive({name})`",), ); }; let call = subcall(cx, field); cx.field_imm(field.span, ident, call) }) .collect::>(); cx.expr_struct(trait_span, ctor_path, fields) } VariantData::Tuple(..) => { let subcalls = all_fields.iter().map(|f| subcall(cx, f)).collect(); let path = cx.expr_path(ctor_path); cx.expr_call(trait_span, path, subcalls) } VariantData::Unit(..) => cx.expr_path(ctor_path), }; BlockOrExpr::new_expr(expr) }