clippy_utils/
check_proc_macro.rs

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
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
//! This module handles checking if the span given is from a proc-macro or not.
//!
//! Proc-macros are capable of setting the span of every token they output to a few possible spans.
//! This includes spans we can detect easily as coming from a proc-macro (e.g. the call site
//! or the def site), and spans we can't easily detect as such (e.g. the span of any token
//! passed into the proc macro). This capability means proc-macros are capable of generating code
//! with a span that looks like it was written by the user, but which should not be linted by clippy
//! as it was generated by an external macro.
//!
//! That brings us to this module. The current approach is to determine a small bit of text which
//! must exist at both the start and the end of an item (e.g. an expression or a path) assuming the
//! code was written, and check if the span contains that text. Note this will only work correctly
//! if the span is not from a `macro_rules` based macro.

use rustc_ast::AttrStyle;
use rustc_ast::ast::{AttrKind, Attribute, IntTy, LitIntType, LitKind, StrStyle, TraitObjectSyntax, UintTy};
use rustc_ast::token::CommentKind;
use rustc_hir::intravisit::FnKind;
use rustc_hir::{
    Block, BlockCheckMode, Body, Closure, Destination, Expr, ExprKind, FieldDef, FnHeader, FnRetTy, HirId, Impl,
    ImplItem, ImplItemKind, IsAuto, Item, ItemKind, Lit, LoopSource, MatchSource, MutTy, Node, Path, QPath, Safety,
    TraitItem, TraitItemKind, Ty, TyKind, UnOp, UnsafeSource, Variant, VariantData, YieldSource,
};
use rustc_lint::{LateContext, LintContext};
use rustc_middle::ty::TyCtxt;
use rustc_session::Session;
use rustc_span::symbol::{Ident, kw};
use rustc_span::{Span, Symbol};
use rustc_target::spec::abi::Abi;

/// The search pattern to look for. Used by `span_matches_pat`
#[derive(Clone)]
pub enum Pat {
    /// A single string.
    Str(&'static str),
    /// Any of the given strings.
    MultiStr(&'static [&'static str]),
    /// Any of the given strings.
    OwnedMultiStr(Vec<String>),
    /// The string representation of the symbol.
    Sym(Symbol),
    /// Any decimal or hexadecimal digit depending on the location.
    Num,
}

/// Checks if the start and the end of the span's text matches the patterns. This will return false
/// if the span crosses multiple files or if source is not available.
fn span_matches_pat(sess: &Session, span: Span, start_pat: Pat, end_pat: Pat) -> bool {
    let pos = sess.source_map().lookup_byte_offset(span.lo());
    let Some(ref src) = pos.sf.src else {
        return false;
    };
    let end = span.hi() - pos.sf.start_pos;
    src.get(pos.pos.0 as usize..end.0 as usize).map_or(false, |s| {
        // Spans can be wrapped in a mixture or parenthesis, whitespace, and trailing commas.
        let start_str = s.trim_start_matches(|c: char| c.is_whitespace() || c == '(');
        let end_str = s.trim_end_matches(|c: char| c.is_whitespace() || c == ')' || c == ',');
        (match start_pat {
            Pat::Str(text) => start_str.starts_with(text),
            Pat::MultiStr(texts) => texts.iter().any(|s| start_str.starts_with(s)),
            Pat::OwnedMultiStr(texts) => texts.iter().any(|s| start_str.starts_with(s)),
            Pat::Sym(sym) => start_str.starts_with(sym.as_str()),
            Pat::Num => start_str.as_bytes().first().map_or(false, u8::is_ascii_digit),
        } && match end_pat {
            Pat::Str(text) => end_str.ends_with(text),
            Pat::MultiStr(texts) => texts.iter().any(|s| start_str.ends_with(s)),
            Pat::OwnedMultiStr(texts) => texts.iter().any(|s| start_str.starts_with(s)),
            Pat::Sym(sym) => end_str.ends_with(sym.as_str()),
            Pat::Num => end_str.as_bytes().last().map_or(false, u8::is_ascii_hexdigit),
        })
    })
}

/// Get the search patterns to use for the given literal
fn lit_search_pat(lit: &LitKind) -> (Pat, Pat) {
    match lit {
        LitKind::Str(_, StrStyle::Cooked) => (Pat::Str("\""), Pat::Str("\"")),
        LitKind::Str(_, StrStyle::Raw(0)) => (Pat::Str("r"), Pat::Str("\"")),
        LitKind::Str(_, StrStyle::Raw(_)) => (Pat::Str("r#"), Pat::Str("#")),
        LitKind::ByteStr(_, StrStyle::Cooked) => (Pat::Str("b\""), Pat::Str("\"")),
        LitKind::ByteStr(_, StrStyle::Raw(0)) => (Pat::Str("br\""), Pat::Str("\"")),
        LitKind::ByteStr(_, StrStyle::Raw(_)) => (Pat::Str("br#\""), Pat::Str("#")),
        LitKind::Byte(_) => (Pat::Str("b'"), Pat::Str("'")),
        LitKind::Char(_) => (Pat::Str("'"), Pat::Str("'")),
        LitKind::Int(_, LitIntType::Signed(IntTy::Isize)) => (Pat::Num, Pat::Str("isize")),
        LitKind::Int(_, LitIntType::Unsigned(UintTy::Usize)) => (Pat::Num, Pat::Str("usize")),
        LitKind::Int(..) => (Pat::Num, Pat::Num),
        LitKind::Float(..) => (Pat::Num, Pat::Str("")),
        LitKind::Bool(true) => (Pat::Str("true"), Pat::Str("true")),
        LitKind::Bool(false) => (Pat::Str("false"), Pat::Str("false")),
        _ => (Pat::Str(""), Pat::Str("")),
    }
}

/// Get the search patterns to use for the given path
fn qpath_search_pat(path: &QPath<'_>) -> (Pat, Pat) {
    match path {
        QPath::Resolved(ty, path) => {
            let start = if ty.is_some() {
                Pat::Str("<")
            } else {
                path.segments.first().map_or(Pat::Str(""), |seg| {
                    if seg.ident.name == kw::PathRoot {
                        Pat::Str("::")
                    } else {
                        Pat::Sym(seg.ident.name)
                    }
                })
            };
            let end = path.segments.last().map_or(Pat::Str(""), |seg| {
                if seg.args.is_some() {
                    Pat::Str(">")
                } else {
                    Pat::Sym(seg.ident.name)
                }
            });
            (start, end)
        },
        QPath::TypeRelative(_, name) => (Pat::Str(""), Pat::Sym(name.ident.name)),
        QPath::LangItem(..) => (Pat::Str(""), Pat::Str("")),
    }
}

fn path_search_pat(path: &Path<'_>) -> (Pat, Pat) {
    let (head, tail) = match path.segments {
        [] => return (Pat::Str(""), Pat::Str("")),
        [p] => (Pat::Sym(p.ident.name), p),
        // QPath::Resolved can have a path that looks like `<Foo as Bar>::baz` where
        // the path (`Bar::baz`) has it's span covering the whole QPath.
        [.., tail] => (Pat::Str(""), tail),
    };
    (
        head,
        if tail.args.is_some() {
            Pat::Str(">")
        } else {
            Pat::Sym(tail.ident.name)
        },
    )
}

/// Get the search patterns to use for the given expression
fn expr_search_pat(tcx: TyCtxt<'_>, e: &Expr<'_>) -> (Pat, Pat) {
    match e.kind {
        ExprKind::ConstBlock(_) => (Pat::Str("const"), Pat::Str("}")),
        // Parenthesis are trimmed from the text before the search patterns are matched.
        // See: `span_matches_pat`
        ExprKind::Tup([]) => (Pat::Str(")"), Pat::Str("(")),
        ExprKind::Unary(UnOp::Deref, e) => (Pat::Str("*"), expr_search_pat(tcx, e).1),
        ExprKind::Unary(UnOp::Not, e) => (Pat::Str("!"), expr_search_pat(tcx, e).1),
        ExprKind::Unary(UnOp::Neg, e) => (Pat::Str("-"), expr_search_pat(tcx, e).1),
        ExprKind::Lit(lit) => lit_search_pat(&lit.node),
        ExprKind::Array(_) | ExprKind::Repeat(..) => (Pat::Str("["), Pat::Str("]")),
        ExprKind::Call(e, []) | ExprKind::MethodCall(_, e, [], _) => (expr_search_pat(tcx, e).0, Pat::Str("(")),
        ExprKind::Call(first, [.., last])
        | ExprKind::MethodCall(_, first, [.., last], _)
        | ExprKind::Binary(_, first, last)
        | ExprKind::Tup([first, .., last])
        | ExprKind::Assign(first, last, _)
        | ExprKind::AssignOp(_, first, last) => (expr_search_pat(tcx, first).0, expr_search_pat(tcx, last).1),
        ExprKind::Tup([e]) | ExprKind::DropTemps(e) => expr_search_pat(tcx, e),
        ExprKind::Cast(e, _) | ExprKind::Type(e, _) => (expr_search_pat(tcx, e).0, Pat::Str("")),
        ExprKind::Let(let_expr) => (Pat::Str("let"), expr_search_pat(tcx, let_expr.init).1),
        ExprKind::If(..) => (Pat::Str("if"), Pat::Str("}")),
        ExprKind::Loop(_, Some(_), _, _) | ExprKind::Block(_, Some(_)) => (Pat::Str("'"), Pat::Str("}")),
        ExprKind::Loop(_, None, LoopSource::Loop, _) => (Pat::Str("loop"), Pat::Str("}")),
        ExprKind::Loop(_, None, LoopSource::While, _) => (Pat::Str("while"), Pat::Str("}")),
        ExprKind::Loop(_, None, LoopSource::ForLoop, _) | ExprKind::Match(_, _, MatchSource::ForLoopDesugar) => {
            (Pat::Str("for"), Pat::Str("}"))
        },
        ExprKind::Match(_, _, MatchSource::Normal) => (Pat::Str("match"), Pat::Str("}")),
        ExprKind::Match(e, _, MatchSource::TryDesugar(_)) => (expr_search_pat(tcx, e).0, Pat::Str("?")),
        ExprKind::Match(e, _, MatchSource::AwaitDesugar) | ExprKind::Yield(e, YieldSource::Await { .. }) => {
            (expr_search_pat(tcx, e).0, Pat::Str("await"))
        },
        ExprKind::Closure(&Closure { body, .. }) => (Pat::Str(""), expr_search_pat(tcx, tcx.hir().body(body).value).1),
        ExprKind::Block(
            Block {
                rules: BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided),
                ..
            },
            None,
        ) => (Pat::Str("unsafe"), Pat::Str("}")),
        ExprKind::Block(_, None) => (Pat::Str("{"), Pat::Str("}")),
        ExprKind::Field(e, name) => (expr_search_pat(tcx, e).0, Pat::Sym(name.name)),
        ExprKind::Index(e, _, _) => (expr_search_pat(tcx, e).0, Pat::Str("]")),
        ExprKind::Path(ref path) => qpath_search_pat(path),
        ExprKind::AddrOf(_, _, e) => (Pat::Str("&"), expr_search_pat(tcx, e).1),
        ExprKind::Break(Destination { label: None, .. }, None) => (Pat::Str("break"), Pat::Str("break")),
        ExprKind::Break(Destination { label: Some(name), .. }, None) => (Pat::Str("break"), Pat::Sym(name.ident.name)),
        ExprKind::Break(_, Some(e)) => (Pat::Str("break"), expr_search_pat(tcx, e).1),
        ExprKind::Continue(Destination { label: None, .. }) => (Pat::Str("continue"), Pat::Str("continue")),
        ExprKind::Continue(Destination { label: Some(name), .. }) => (Pat::Str("continue"), Pat::Sym(name.ident.name)),
        ExprKind::Ret(None) => (Pat::Str("return"), Pat::Str("return")),
        ExprKind::Ret(Some(e)) => (Pat::Str("return"), expr_search_pat(tcx, e).1),
        ExprKind::Struct(path, _, _) => (qpath_search_pat(path).0, Pat::Str("}")),
        ExprKind::Yield(e, YieldSource::Yield) => (Pat::Str("yield"), expr_search_pat(tcx, e).1),
        _ => (Pat::Str(""), Pat::Str("")),
    }
}

fn fn_header_search_pat(header: FnHeader) -> Pat {
    if header.is_async() {
        Pat::Str("async")
    } else if header.is_const() {
        Pat::Str("const")
    } else if header.is_unsafe() {
        Pat::Str("unsafe")
    } else if header.abi != Abi::Rust {
        Pat::Str("extern")
    } else {
        Pat::MultiStr(&["fn", "extern"])
    }
}

fn item_search_pat(item: &Item<'_>) -> (Pat, Pat) {
    let (start_pat, end_pat) = match &item.kind {
        ItemKind::ExternCrate(_) => (Pat::Str("extern"), Pat::Str(";")),
        ItemKind::Static(..) => (Pat::Str("static"), Pat::Str(";")),
        ItemKind::Const(..) => (Pat::Str("const"), Pat::Str(";")),
        ItemKind::Fn(sig, ..) => (fn_header_search_pat(sig.header), Pat::Str("")),
        ItemKind::ForeignMod { .. } => (Pat::Str("extern"), Pat::Str("}")),
        ItemKind::TyAlias(..) | ItemKind::OpaqueTy(_) => (Pat::Str("type"), Pat::Str(";")),
        ItemKind::Enum(..) => (Pat::Str("enum"), Pat::Str("}")),
        ItemKind::Struct(VariantData::Struct { .. }, _) => (Pat::Str("struct"), Pat::Str("}")),
        ItemKind::Struct(..) => (Pat::Str("struct"), Pat::Str(";")),
        ItemKind::Union(..) => (Pat::Str("union"), Pat::Str("}")),
        ItemKind::Trait(_, Safety::Unsafe, ..)
        | ItemKind::Impl(Impl {
            safety: Safety::Unsafe, ..
        }) => (Pat::Str("unsafe"), Pat::Str("}")),
        ItemKind::Trait(IsAuto::Yes, ..) => (Pat::Str("auto"), Pat::Str("}")),
        ItemKind::Trait(..) => (Pat::Str("trait"), Pat::Str("}")),
        ItemKind::Impl(_) => (Pat::Str("impl"), Pat::Str("}")),
        _ => return (Pat::Str(""), Pat::Str("")),
    };
    if item.vis_span.is_empty() {
        (start_pat, end_pat)
    } else {
        (Pat::Str("pub"), end_pat)
    }
}

fn trait_item_search_pat(item: &TraitItem<'_>) -> (Pat, Pat) {
    match &item.kind {
        TraitItemKind::Const(..) => (Pat::Str("const"), Pat::Str(";")),
        TraitItemKind::Type(..) => (Pat::Str("type"), Pat::Str(";")),
        TraitItemKind::Fn(sig, ..) => (fn_header_search_pat(sig.header), Pat::Str("")),
    }
}

fn impl_item_search_pat(item: &ImplItem<'_>) -> (Pat, Pat) {
    let (start_pat, end_pat) = match &item.kind {
        ImplItemKind::Const(..) => (Pat::Str("const"), Pat::Str(";")),
        ImplItemKind::Type(..) => (Pat::Str("type"), Pat::Str(";")),
        ImplItemKind::Fn(sig, ..) => (fn_header_search_pat(sig.header), Pat::Str("")),
    };
    if item.vis_span.is_empty() {
        (start_pat, end_pat)
    } else {
        (Pat::Str("pub"), end_pat)
    }
}

fn field_def_search_pat(def: &FieldDef<'_>) -> (Pat, Pat) {
    if def.vis_span.is_empty() {
        if def.is_positional() {
            (Pat::Str(""), Pat::Str(""))
        } else {
            (Pat::Sym(def.ident.name), Pat::Str(""))
        }
    } else {
        (Pat::Str("pub"), Pat::Str(""))
    }
}

fn variant_search_pat(v: &Variant<'_>) -> (Pat, Pat) {
    match v.data {
        VariantData::Struct { .. } => (Pat::Sym(v.ident.name), Pat::Str("}")),
        VariantData::Tuple(..) => (Pat::Sym(v.ident.name), Pat::Str("")),
        VariantData::Unit(..) => (Pat::Sym(v.ident.name), Pat::Sym(v.ident.name)),
    }
}

fn fn_kind_pat(tcx: TyCtxt<'_>, kind: &FnKind<'_>, body: &Body<'_>, hir_id: HirId) -> (Pat, Pat) {
    let (start_pat, end_pat) = match kind {
        FnKind::ItemFn(.., header) => (fn_header_search_pat(*header), Pat::Str("")),
        FnKind::Method(.., sig) => (fn_header_search_pat(sig.header), Pat::Str("")),
        FnKind::Closure => return (Pat::Str(""), expr_search_pat(tcx, body.value).1),
    };
    let start_pat = match tcx.hir_node(hir_id) {
        Node::Item(Item { vis_span, .. }) | Node::ImplItem(ImplItem { vis_span, .. }) => {
            if vis_span.is_empty() {
                start_pat
            } else {
                Pat::Str("pub")
            }
        },
        Node::TraitItem(_) => start_pat,
        _ => Pat::Str(""),
    };
    (start_pat, end_pat)
}

fn attr_search_pat(attr: &Attribute) -> (Pat, Pat) {
    match attr.kind {
        AttrKind::Normal(..) => {
            if let Some(ident) = attr.ident() {
                // TODO: I feel like it's likely we can use `Cow` instead but this will require quite a bit of
                // refactoring
                // NOTE: This will likely have false positives, like `allow = 1`
                (
                    Pat::OwnedMultiStr(vec![ident.to_string(), "#".to_owned()]),
                    Pat::Str(""),
                )
            } else {
                (Pat::Str("#"), Pat::Str("]"))
            }
        },
        AttrKind::DocComment(_kind @ CommentKind::Line, ..) => {
            if matches!(attr.style, AttrStyle::Outer) {
                (Pat::Str("///"), Pat::Str(""))
            } else {
                (Pat::Str("//!"), Pat::Str(""))
            }
        },
        AttrKind::DocComment(_kind @ CommentKind::Block, ..) => {
            if matches!(attr.style, AttrStyle::Outer) {
                (Pat::Str("/**"), Pat::Str("*/"))
            } else {
                (Pat::Str("/*!"), Pat::Str("*/"))
            }
        },
    }
}

fn ty_search_pat(ty: &Ty<'_>) -> (Pat, Pat) {
    match ty.kind {
        TyKind::Slice(..) | TyKind::Array(..) => (Pat::Str("["), Pat::Str("]")),
        TyKind::Ptr(MutTy { ty, .. }) => (Pat::Str("*"), ty_search_pat(ty).1),
        TyKind::Ref(_, MutTy { ty, .. }) => (Pat::Str("&"), ty_search_pat(ty).1),
        TyKind::BareFn(bare_fn) => (
            if bare_fn.safety == Safety::Unsafe {
                Pat::Str("unsafe")
            } else if bare_fn.abi != Abi::Rust {
                Pat::Str("extern")
            } else {
                Pat::MultiStr(&["fn", "extern"])
            },
            match bare_fn.decl.output {
                FnRetTy::DefaultReturn(_) => {
                    if let [.., ty] = bare_fn.decl.inputs {
                        ty_search_pat(ty).1
                    } else {
                        Pat::Str("(")
                    }
                },
                FnRetTy::Return(ty) => ty_search_pat(ty).1,
            },
        ),
        TyKind::Never => (Pat::Str("!"), Pat::Str("!")),
        // Parenthesis are trimmed from the text before the search patterns are matched.
        // See: `span_matches_pat`
        TyKind::Tup([]) => (Pat::Str(")"), Pat::Str("(")),
        TyKind::Tup([ty]) => ty_search_pat(ty),
        TyKind::Tup([head, .., tail]) => (ty_search_pat(head).0, ty_search_pat(tail).1),
        TyKind::OpaqueDef(..) => (Pat::Str("impl"), Pat::Str("")),
        TyKind::Path(qpath) => qpath_search_pat(&qpath),
        TyKind::Infer => (Pat::Str("_"), Pat::Str("_")),
        TyKind::TraitObject(_, _, TraitObjectSyntax::Dyn) => (Pat::Str("dyn"), Pat::Str("")),
        // NOTE: `TraitObject` is incomplete. It will always return true then.
        _ => (Pat::Str(""), Pat::Str("")),
    }
}

fn ident_search_pat(ident: Ident) -> (Pat, Pat) {
    (Pat::Sym(ident.name), Pat::Sym(ident.name))
}

pub trait WithSearchPat<'cx> {
    type Context: LintContext;
    fn search_pat(&self, cx: &Self::Context) -> (Pat, Pat);
    fn span(&self) -> Span;
}
macro_rules! impl_with_search_pat {
    (($cx_ident:ident: $cx_ty:ident<$cx_lt:lifetime>, $self:tt: $ty:ty) => $fn:ident($($args:tt)*)) => {
        impl<$cx_lt> WithSearchPat<$cx_lt> for $ty {
            type Context = $cx_ty<$cx_lt>;
            fn search_pat(&$self, $cx_ident: &Self::Context) -> (Pat, Pat) {
                $fn($($args)*)
            }
            fn span(&self) -> Span {
                self.span
            }
        }
    };
}
impl_with_search_pat!((cx: LateContext<'tcx>, self: Expr<'tcx>) => expr_search_pat(cx.tcx, self));
impl_with_search_pat!((_cx: LateContext<'tcx>, self: Item<'_>) => item_search_pat(self));
impl_with_search_pat!((_cx: LateContext<'tcx>, self: TraitItem<'_>) => trait_item_search_pat(self));
impl_with_search_pat!((_cx: LateContext<'tcx>, self: ImplItem<'_>) => impl_item_search_pat(self));
impl_with_search_pat!((_cx: LateContext<'tcx>, self: FieldDef<'_>) => field_def_search_pat(self));
impl_with_search_pat!((_cx: LateContext<'tcx>, self: Variant<'_>) => variant_search_pat(self));
impl_with_search_pat!((_cx: LateContext<'tcx>, self: Ty<'_>) => ty_search_pat(self));
impl_with_search_pat!((_cx: LateContext<'tcx>, self: Attribute) => attr_search_pat(self));
impl_with_search_pat!((_cx: LateContext<'tcx>, self: Ident) => ident_search_pat(*self));
impl_with_search_pat!((_cx: LateContext<'tcx>, self: Lit) => lit_search_pat(&self.node));
impl_with_search_pat!((_cx: LateContext<'tcx>, self: Path<'_>) => path_search_pat(self));

impl<'cx> WithSearchPat<'cx> for (&FnKind<'cx>, &Body<'cx>, HirId, Span) {
    type Context = LateContext<'cx>;

    fn search_pat(&self, cx: &Self::Context) -> (Pat, Pat) {
        fn_kind_pat(cx.tcx, self.0, self.1, self.2)
    }

    fn span(&self) -> Span {
        self.3
    }
}

/// Checks if the item likely came from a proc-macro.
///
/// This should be called after `in_external_macro` and the initial pattern matching of the ast as
/// it is significantly slower than both of those.
pub fn is_from_proc_macro<'cx, T: WithSearchPat<'cx>>(cx: &T::Context, item: &T) -> bool {
    let (start_pat, end_pat) = item.search_pat(cx);
    !span_matches_pat(cx.sess(), item.span(), start_pat, end_pat)
}

/// Checks if the span actually refers to a match expression
pub fn is_span_match(cx: &impl LintContext, span: Span) -> bool {
    span_matches_pat(cx.sess(), span, Pat::Str("match"), Pat::Str("}"))
}

/// Checks if the span actually refers to an if expression
pub fn is_span_if(cx: &impl LintContext, span: Span) -> bool {
    span_matches_pat(cx.sess(), span, Pat::Str("if"), Pat::Str("}"))
}