hir_def/hir/
type_ref.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
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
//! HIR for references to types. Paths in these are not yet resolved. They can
//! be directly created from an ast::TypeRef, without further queries.

use core::fmt;
use std::{fmt::Write, ops::Index};

use hir_expand::{
    db::ExpandDatabase,
    name::{AsName, Name},
    AstId, InFile,
};
use intern::{sym, Symbol};
use la_arena::{Arena, ArenaMap, Idx};
use span::Edition;
use stdx::thin_vec::{thin_vec_with_header_struct, EmptyOptimizedThinVec, ThinVec};
use syntax::{
    ast::{self, HasGenericArgs, HasName, IsString},
    AstPtr,
};

use crate::{
    builtin_type::{BuiltinInt, BuiltinType, BuiltinUint},
    hir::Literal,
    lower::LowerCtx,
    path::{GenericArg, Path},
    SyntheticSyntax,
};

#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
pub enum Mutability {
    Shared,
    Mut,
}

impl Mutability {
    pub fn from_mutable(mutable: bool) -> Mutability {
        if mutable {
            Mutability::Mut
        } else {
            Mutability::Shared
        }
    }

    pub fn as_keyword_for_ref(self) -> &'static str {
        match self {
            Mutability::Shared => "",
            Mutability::Mut => "mut ",
        }
    }

    pub fn as_keyword_for_ptr(self) -> &'static str {
        match self {
            Mutability::Shared => "const ",
            Mutability::Mut => "mut ",
        }
    }

    /// Returns `true` if the mutability is [`Mut`].
    ///
    /// [`Mut`]: Mutability::Mut
    #[must_use]
    pub fn is_mut(&self) -> bool {
        matches!(self, Self::Mut)
    }

    /// Returns `true` if the mutability is [`Shared`].
    ///
    /// [`Shared`]: Mutability::Shared
    #[must_use]
    pub fn is_shared(&self) -> bool {
        matches!(self, Self::Shared)
    }
}

#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
pub enum Rawness {
    RawPtr,
    Ref,
}

impl Rawness {
    pub fn from_raw(is_raw: bool) -> Rawness {
        if is_raw {
            Rawness::RawPtr
        } else {
            Rawness::Ref
        }
    }

    pub fn is_raw(&self) -> bool {
        matches!(self, Self::RawPtr)
    }
}

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
/// A `TypeRefId` that is guaranteed to always be `TypeRef::Path`. We use this for things like
/// impl's trait, that are always paths but need to be traced back to source code.
pub struct PathId(TypeRefId);

impl PathId {
    #[inline]
    pub fn from_type_ref_unchecked(type_ref: TypeRefId) -> Self {
        Self(type_ref)
    }

    #[inline]
    pub fn type_ref(self) -> TypeRefId {
        self.0
    }
}

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub struct TraitRef {
    pub path: PathId,
}

impl TraitRef {
    /// Converts an `ast::PathType` to a `hir::TraitRef`.
    pub(crate) fn from_ast(ctx: &mut LowerCtx<'_>, node: ast::Type) -> Option<Self> {
        // FIXME: Use `Path::from_src`
        match &node {
            ast::Type::PathType(path) => path
                .path()
                .and_then(|it| ctx.lower_path(it))
                .map(|path| TraitRef { path: ctx.alloc_path(path, AstPtr::new(&node)) }),
            _ => None,
        }
    }
}

thin_vec_with_header_struct! {
    pub new(pub(crate)) struct FnType, FnTypeHeader {
        pub params: [(Option<Name>, TypeRefId)],
        pub is_varargs: bool,
        pub is_unsafe: bool,
        pub abi: Option<Symbol>; ref,
    }
}

#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub struct ArrayType {
    pub ty: TypeRefId,
    // FIXME: This should be Ast<ConstArg>
    pub len: ConstRef,
}

#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub struct RefType {
    pub ty: TypeRefId,
    pub lifetime: Option<LifetimeRef>,
    pub mutability: Mutability,
}

/// Compare ty::Ty
#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub enum TypeRef {
    Never,
    Placeholder,
    Tuple(EmptyOptimizedThinVec<TypeRefId>),
    Path(Path),
    RawPtr(TypeRefId, Mutability),
    Reference(Box<RefType>),
    Array(Box<ArrayType>),
    Slice(TypeRefId),
    /// A fn pointer. Last element of the vector is the return type.
    Fn(FnType),
    ImplTrait(ThinVec<TypeBound>),
    DynTrait(ThinVec<TypeBound>),
    Macro(AstId<ast::MacroCall>),
    Error,
}

#[cfg(target_arch = "x86_64")]
const _: () = assert!(size_of::<TypeRef>() == 16);

pub type TypeRefId = Idx<TypeRef>;

#[derive(Default, Clone, PartialEq, Eq, Debug, Hash)]
pub struct TypesMap {
    pub(crate) types: Arena<TypeRef>,
}

impl TypesMap {
    pub const EMPTY: &TypesMap = &TypesMap { types: Arena::new() };

    pub(crate) fn shrink_to_fit(&mut self) {
        let TypesMap { types } = self;
        types.shrink_to_fit();
    }
}

impl Index<TypeRefId> for TypesMap {
    type Output = TypeRef;

    #[inline]
    fn index(&self, index: TypeRefId) -> &Self::Output {
        &self.types[index]
    }
}

impl Index<PathId> for TypesMap {
    type Output = Path;

    #[inline]
    fn index(&self, index: PathId) -> &Self::Output {
        let TypeRef::Path(path) = &self[index.type_ref()] else {
            unreachable!("`PathId` always points to `TypeRef::Path`");
        };
        path
    }
}

pub type TypePtr = AstPtr<ast::Type>;
pub type TypeSource = InFile<TypePtr>;

#[derive(Default, Clone, PartialEq, Eq, Debug, Hash)]
pub struct TypesSourceMap {
    pub(crate) types_map_back: ArenaMap<TypeRefId, TypeSource>,
}

impl TypesSourceMap {
    pub const EMPTY: Self = Self { types_map_back: ArenaMap::new() };

    pub fn type_syntax(&self, id: TypeRefId) -> Result<TypeSource, SyntheticSyntax> {
        self.types_map_back.get(id).cloned().ok_or(SyntheticSyntax)
    }

    pub(crate) fn shrink_to_fit(&mut self) {
        let TypesSourceMap { types_map_back } = self;
        types_map_back.shrink_to_fit();
    }
}

#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub struct LifetimeRef {
    pub name: Name,
}

impl LifetimeRef {
    pub(crate) fn new_name(name: Name) -> Self {
        LifetimeRef { name }
    }

    pub(crate) fn new(lifetime: &ast::Lifetime) -> Self {
        LifetimeRef { name: Name::new_lifetime(lifetime) }
    }

    pub fn missing() -> LifetimeRef {
        LifetimeRef { name: Name::missing() }
    }
}

#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub enum TypeBound {
    Path(PathId, TraitBoundModifier),
    ForLifetime(Box<[Name]>, PathId),
    Lifetime(LifetimeRef),
    Use(Box<[UseArgRef]>),
    Error,
}

#[cfg(target_pointer_width = "64")]
const _: [(); 24] = [(); ::std::mem::size_of::<TypeBound>()];

#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub enum UseArgRef {
    Name(Name),
    Lifetime(LifetimeRef),
}

/// A modifier on a bound, currently this is only used for `?Sized`, where the
/// modifier is `Maybe`.
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub enum TraitBoundModifier {
    None,
    Maybe,
}

impl TypeRef {
    /// Converts an `ast::TypeRef` to a `hir::TypeRef`.
    pub fn from_ast(ctx: &mut LowerCtx<'_>, node: ast::Type) -> TypeRefId {
        let ty = match &node {
            ast::Type::ParenType(inner) => return TypeRef::from_ast_opt(ctx, inner.ty()),
            ast::Type::TupleType(inner) => TypeRef::Tuple(EmptyOptimizedThinVec::from_iter(
                Vec::from_iter(inner.fields().map(|it| TypeRef::from_ast(ctx, it))),
            )),
            ast::Type::NeverType(..) => TypeRef::Never,
            ast::Type::PathType(inner) => {
                // FIXME: Use `Path::from_src`
                inner
                    .path()
                    .and_then(|it| ctx.lower_path(it))
                    .map(TypeRef::Path)
                    .unwrap_or(TypeRef::Error)
            }
            ast::Type::PtrType(inner) => {
                let inner_ty = TypeRef::from_ast_opt(ctx, inner.ty());
                let mutability = Mutability::from_mutable(inner.mut_token().is_some());
                TypeRef::RawPtr(inner_ty, mutability)
            }
            ast::Type::ArrayType(inner) => {
                let len = ConstRef::from_const_arg(ctx, inner.const_arg());
                TypeRef::Array(Box::new(ArrayType {
                    ty: TypeRef::from_ast_opt(ctx, inner.ty()),
                    len,
                }))
            }
            ast::Type::SliceType(inner) => TypeRef::Slice(TypeRef::from_ast_opt(ctx, inner.ty())),
            ast::Type::RefType(inner) => {
                let inner_ty = TypeRef::from_ast_opt(ctx, inner.ty());
                let lifetime = inner.lifetime().map(|lt| LifetimeRef::new(&lt));
                let mutability = Mutability::from_mutable(inner.mut_token().is_some());
                TypeRef::Reference(Box::new(RefType { ty: inner_ty, lifetime, mutability }))
            }
            ast::Type::InferType(_inner) => TypeRef::Placeholder,
            ast::Type::FnPtrType(inner) => {
                let ret_ty = inner
                    .ret_type()
                    .and_then(|rt| rt.ty())
                    .map(|it| TypeRef::from_ast(ctx, it))
                    .unwrap_or_else(|| ctx.alloc_type_ref_desugared(TypeRef::unit()));
                let mut is_varargs = false;
                let mut params = if let Some(pl) = inner.param_list() {
                    if let Some(param) = pl.params().last() {
                        is_varargs = param.dotdotdot_token().is_some();
                    }

                    pl.params()
                        .map(|it| {
                            let type_ref = TypeRef::from_ast_opt(ctx, it.ty());
                            let name = match it.pat() {
                                Some(ast::Pat::IdentPat(it)) => Some(
                                    it.name().map(|nr| nr.as_name()).unwrap_or_else(Name::missing),
                                ),
                                _ => None,
                            };
                            (name, type_ref)
                        })
                        .collect()
                } else {
                    Vec::with_capacity(1)
                };
                fn lower_abi(abi: ast::Abi) -> Symbol {
                    match abi.abi_string() {
                        Some(tok) => Symbol::intern(tok.text_without_quotes()),
                        // `extern` default to be `extern "C"`.
                        _ => sym::C.clone(),
                    }
                }

                let abi = inner.abi().map(lower_abi);
                params.push((None, ret_ty));
                TypeRef::Fn(FnType::new(is_varargs, inner.unsafe_token().is_some(), abi, params))
            }
            // for types are close enough for our purposes to the inner type for now...
            ast::Type::ForType(inner) => return TypeRef::from_ast_opt(ctx, inner.ty()),
            ast::Type::ImplTraitType(inner) => {
                if ctx.outer_impl_trait() {
                    // Disallow nested impl traits
                    TypeRef::Error
                } else {
                    ctx.with_outer_impl_trait_scope(true, |ctx| {
                        TypeRef::ImplTrait(type_bounds_from_ast(ctx, inner.type_bound_list()))
                    })
                }
            }
            ast::Type::DynTraitType(inner) => {
                TypeRef::DynTrait(type_bounds_from_ast(ctx, inner.type_bound_list()))
            }
            ast::Type::MacroType(mt) => match mt.macro_call() {
                Some(mc) => TypeRef::Macro(ctx.ast_id(&mc)),
                None => TypeRef::Error,
            },
        };
        ctx.alloc_type_ref(ty, AstPtr::new(&node))
    }

    pub(crate) fn from_ast_opt(ctx: &mut LowerCtx<'_>, node: Option<ast::Type>) -> TypeRefId {
        match node {
            Some(node) => TypeRef::from_ast(ctx, node),
            None => ctx.alloc_error_type(),
        }
    }

    pub(crate) fn unit() -> TypeRef {
        TypeRef::Tuple(EmptyOptimizedThinVec::empty())
    }

    pub fn walk(this: TypeRefId, map: &TypesMap, f: &mut impl FnMut(&TypeRef)) {
        go(this, f, map);

        fn go(type_ref: TypeRefId, f: &mut impl FnMut(&TypeRef), map: &TypesMap) {
            let type_ref = &map[type_ref];
            f(type_ref);
            match type_ref {
                TypeRef::Fn(fn_) => {
                    fn_.params().iter().for_each(|&(_, param_type)| go(param_type, f, map))
                }
                TypeRef::Tuple(types) => types.iter().for_each(|&t| go(t, f, map)),
                TypeRef::RawPtr(type_ref, _) | TypeRef::Slice(type_ref) => go(*type_ref, f, map),
                TypeRef::Reference(it) => go(it.ty, f, map),
                TypeRef::Array(it) => go(it.ty, f, map),
                TypeRef::ImplTrait(bounds) | TypeRef::DynTrait(bounds) => {
                    for bound in bounds {
                        match bound {
                            &TypeBound::Path(path, _) | &TypeBound::ForLifetime(_, path) => {
                                go_path(&map[path], f, map)
                            }
                            TypeBound::Lifetime(_) | TypeBound::Error | TypeBound::Use(_) => (),
                        }
                    }
                }
                TypeRef::Path(path) => go_path(path, f, map),
                TypeRef::Never | TypeRef::Placeholder | TypeRef::Macro(_) | TypeRef::Error => {}
            };
        }

        fn go_path(path: &Path, f: &mut impl FnMut(&TypeRef), map: &TypesMap) {
            if let Some(type_ref) = path.type_anchor() {
                go(type_ref, f, map);
            }
            for segment in path.segments().iter() {
                if let Some(args_and_bindings) = segment.args_and_bindings {
                    for arg in args_and_bindings.args.iter() {
                        match arg {
                            GenericArg::Type(type_ref) => {
                                go(*type_ref, f, map);
                            }
                            GenericArg::Const(_) | GenericArg::Lifetime(_) => {}
                        }
                    }
                    for binding in args_and_bindings.bindings.iter() {
                        if let Some(type_ref) = binding.type_ref {
                            go(type_ref, f, map);
                        }
                        for bound in binding.bounds.iter() {
                            match bound {
                                &TypeBound::Path(path, _) | &TypeBound::ForLifetime(_, path) => {
                                    go_path(&map[path], f, map)
                                }
                                TypeBound::Lifetime(_) | TypeBound::Error | TypeBound::Use(_) => (),
                            }
                        }
                    }
                }
            }
        }
    }
}

pub(crate) fn type_bounds_from_ast(
    lower_ctx: &mut LowerCtx<'_>,
    type_bounds_opt: Option<ast::TypeBoundList>,
) -> ThinVec<TypeBound> {
    if let Some(type_bounds) = type_bounds_opt {
        ThinVec::from_iter(Vec::from_iter(
            type_bounds.bounds().map(|it| TypeBound::from_ast(lower_ctx, it)),
        ))
    } else {
        ThinVec::from_iter([])
    }
}

impl TypeBound {
    pub(crate) fn from_ast(ctx: &mut LowerCtx<'_>, node: ast::TypeBound) -> Self {
        let mut lower_path_type = |path_type: &ast::PathType| ctx.lower_path(path_type.path()?);

        match node.kind() {
            ast::TypeBoundKind::PathType(path_type) => {
                let m = match node.question_mark_token() {
                    Some(_) => TraitBoundModifier::Maybe,
                    None => TraitBoundModifier::None,
                };
                lower_path_type(&path_type)
                    .map(|p| {
                        TypeBound::Path(ctx.alloc_path(p, AstPtr::new(&path_type).upcast()), m)
                    })
                    .unwrap_or(TypeBound::Error)
            }
            ast::TypeBoundKind::ForType(for_type) => {
                let lt_refs = match for_type.generic_param_list() {
                    Some(gpl) => gpl
                        .lifetime_params()
                        .flat_map(|lp| lp.lifetime().map(|lt| Name::new_lifetime(&lt)))
                        .collect(),
                    None => Box::default(),
                };
                let path = for_type.ty().and_then(|ty| match &ty {
                    ast::Type::PathType(path_type) => lower_path_type(path_type).map(|p| (p, ty)),
                    _ => None,
                });
                match path {
                    Some((p, ty)) => {
                        TypeBound::ForLifetime(lt_refs, ctx.alloc_path(p, AstPtr::new(&ty)))
                    }
                    None => TypeBound::Error,
                }
            }
            ast::TypeBoundKind::Use(gal) => TypeBound::Use(
                gal.use_bound_generic_args()
                    .map(|p| match p {
                        ast::UseBoundGenericArg::Lifetime(l) => {
                            UseArgRef::Lifetime(LifetimeRef::new(&l))
                        }
                        ast::UseBoundGenericArg::NameRef(n) => UseArgRef::Name(n.as_name()),
                    })
                    .collect(),
            ),
            ast::TypeBoundKind::Lifetime(lifetime) => {
                TypeBound::Lifetime(LifetimeRef::new(&lifetime))
            }
        }
    }

    pub fn as_path<'a>(&self, map: &'a TypesMap) -> Option<(&'a Path, TraitBoundModifier)> {
        match self {
            &TypeBound::Path(p, m) => Some((&map[p], m)),
            &TypeBound::ForLifetime(_, p) => Some((&map[p], TraitBoundModifier::None)),
            TypeBound::Lifetime(_) | TypeBound::Error | TypeBound::Use(_) => None,
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum ConstRef {
    Scalar(Box<LiteralConstRef>),
    Path(Name),
    Complex(AstId<ast::ConstArg>),
}

impl ConstRef {
    pub(crate) fn from_const_arg(lower_ctx: &LowerCtx<'_>, arg: Option<ast::ConstArg>) -> Self {
        if let Some(arg) = arg {
            if let Some(expr) = arg.expr() {
                return Self::from_expr(expr, Some(lower_ctx.ast_id(&arg)));
            }
        }
        Self::Scalar(Box::new(LiteralConstRef::Unknown))
    }

    pub(crate) fn from_const_param(
        lower_ctx: &LowerCtx<'_>,
        param: &ast::ConstParam,
    ) -> Option<Self> {
        param.default_val().map(|default| Self::from_const_arg(lower_ctx, Some(default)))
    }

    pub fn display<'a>(
        &'a self,
        db: &'a dyn ExpandDatabase,
        edition: Edition,
    ) -> impl fmt::Display + 'a {
        struct Display<'a>(&'a dyn ExpandDatabase, &'a ConstRef, Edition);
        impl fmt::Display for Display<'_> {
            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                match self.1 {
                    ConstRef::Scalar(s) => s.fmt(f),
                    ConstRef::Path(n) => n.display(self.0, self.2).fmt(f),
                    ConstRef::Complex(_) => f.write_str("{const}"),
                }
            }
        }
        Display(db, self, edition)
    }

    // We special case literals and single identifiers, to speed up things.
    fn from_expr(expr: ast::Expr, ast_id: Option<AstId<ast::ConstArg>>) -> Self {
        fn is_path_ident(p: &ast::PathExpr) -> bool {
            let Some(path) = p.path() else {
                return false;
            };
            if path.coloncolon_token().is_some() {
                return false;
            }
            if let Some(s) = path.segment() {
                if s.coloncolon_token().is_some() || s.generic_arg_list().is_some() {
                    return false;
                }
            }
            true
        }
        match expr {
            ast::Expr::PathExpr(p) if is_path_ident(&p) => {
                match p.path().and_then(|it| it.segment()).and_then(|it| it.name_ref()) {
                    Some(it) => Self::Path(it.as_name()),
                    None => Self::Scalar(Box::new(LiteralConstRef::Unknown)),
                }
            }
            ast::Expr::Literal(literal) => Self::Scalar(Box::new(match literal.kind() {
                ast::LiteralKind::IntNumber(num) => {
                    num.value().map(LiteralConstRef::UInt).unwrap_or(LiteralConstRef::Unknown)
                }
                ast::LiteralKind::Char(c) => {
                    c.value().map(LiteralConstRef::Char).unwrap_or(LiteralConstRef::Unknown)
                }
                ast::LiteralKind::Bool(f) => LiteralConstRef::Bool(f),
                _ => LiteralConstRef::Unknown,
            })),
            _ => {
                if let Some(ast_id) = ast_id {
                    Self::Complex(ast_id)
                } else {
                    Self::Scalar(Box::new(LiteralConstRef::Unknown))
                }
            }
        }
    }
}

/// A literal constant value
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum LiteralConstRef {
    Int(i128),
    UInt(u128),
    Bool(bool),
    Char(char),

    /// Case of an unknown value that rustc might know but we don't
    // FIXME: this is a hack to get around chalk not being able to represent unevaluatable
    // constants
    // https://github.com/rust-lang/rust-analyzer/pull/8813#issuecomment-840679177
    // https://rust-lang.zulipchat.com/#narrow/stream/144729-wg-traits/topic/Handling.20non.20evaluatable.20constants'.20equality/near/238386348
    Unknown,
}

impl LiteralConstRef {
    pub fn builtin_type(&self) -> BuiltinType {
        match self {
            LiteralConstRef::UInt(_) | LiteralConstRef::Unknown => {
                BuiltinType::Uint(BuiltinUint::U128)
            }
            LiteralConstRef::Int(_) => BuiltinType::Int(BuiltinInt::I128),
            LiteralConstRef::Char(_) => BuiltinType::Char,
            LiteralConstRef::Bool(_) => BuiltinType::Bool,
        }
    }
}

impl From<Literal> for LiteralConstRef {
    fn from(literal: Literal) -> Self {
        match literal {
            Literal::Char(c) => Self::Char(c),
            Literal::Bool(flag) => Self::Bool(flag),
            Literal::Int(num, _) => Self::Int(num),
            Literal::Uint(num, _) => Self::UInt(num),
            _ => Self::Unknown,
        }
    }
}

impl std::fmt::Display for LiteralConstRef {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
        match self {
            LiteralConstRef::Int(num) => num.fmt(f),
            LiteralConstRef::UInt(num) => num.fmt(f),
            LiteralConstRef::Bool(flag) => flag.fmt(f),
            LiteralConstRef::Char(c) => write!(f, "'{c}'"),
            LiteralConstRef::Unknown => f.write_char('_'),
        }
    }
}