1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
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 = 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(),
    );

    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)));
}