clippy_utils/
consts.rs

1//! A simple const eval API, for use on arbitrary HIR expressions.
2//!
3//! This cannot use rustc's const eval, aka miri, as arbitrary HIR expressions cannot be lowered to
4//! executable MIR bodies, so we have to do this instead.
5#![expect(clippy::float_cmp)]
6
7use crate::res::MaybeDef;
8use crate::source::{SpanRangeExt, walk_span_to_context};
9use crate::{clip, is_direct_expn_of, sext, sym, unsext};
10
11use rustc_abi::Size;
12use rustc_apfloat::Float;
13use rustc_apfloat::ieee::{Half, Quad};
14use rustc_ast::ast::{LitFloatType, LitKind};
15use rustc_hir::def::{DefKind, Res};
16use rustc_hir::{BinOpKind, Block, ConstBlock, Expr, ExprKind, HirId, PatExpr, PatExprKind, QPath, TyKind, UnOp};
17use rustc_lexer::{FrontmatterAllowed, tokenize};
18use rustc_lint::LateContext;
19use rustc_middle::mir::ConstValue;
20use rustc_middle::mir::interpret::{Scalar, alloc_range};
21use rustc_middle::ty::{self, FloatTy, IntTy, ScalarInt, Ty, TyCtxt, TypeckResults, UintTy};
22use rustc_middle::{bug, mir, span_bug};
23use rustc_span::{Symbol, SyntaxContext};
24use std::cell::Cell;
25use std::cmp::Ordering;
26use std::hash::{Hash, Hasher};
27use std::iter;
28
29/// A `LitKind`-like enum to fold constant `Expr`s into.
30#[derive(Debug, Clone)]
31pub enum Constant {
32    Adt(ConstValue),
33    /// A `String` (e.g., "abc").
34    Str(String),
35    /// A binary string (e.g., `b"abc"`).
36    Binary(Vec<u8>),
37    /// A single `char` (e.g., `'a'`).
38    Char(char),
39    /// An integer's bit representation.
40    Int(u128),
41    /// An `f16` bitcast to a `u16`.
42    // FIXME(f16_f128): use `f16` once builtins are available on all host tools platforms.
43    F16(u16),
44    /// An `f32`.
45    F32(f32),
46    /// An `f64`.
47    F64(f64),
48    /// An `f128` bitcast to a `u128`.
49    // FIXME(f16_f128): use `f128` once builtins are available on all host tools platforms.
50    F128(u128),
51    /// `true` or `false`.
52    Bool(bool),
53    /// An array of constants.
54    Vec(Vec<Self>),
55    /// Also an array, but with only one constant, repeated N times.
56    Repeat(Box<Self>, u64),
57    /// A tuple of constants.
58    Tuple(Vec<Self>),
59    /// A raw pointer.
60    RawPtr(u128),
61    /// A reference
62    Ref(Box<Self>),
63    /// A literal with syntax error.
64    Err,
65}
66
67trait IntTypeBounds: Sized {
68    type Output: PartialOrd;
69
70    fn min_max(self) -> Option<(Self::Output, Self::Output)>;
71    fn bits(self) -> Self::Output;
72    fn ensure_fits(self, val: Self::Output) -> Option<Self::Output> {
73        let (min, max) = self.min_max()?;
74        (min <= val && val <= max).then_some(val)
75    }
76}
77impl IntTypeBounds for UintTy {
78    type Output = u128;
79    fn min_max(self) -> Option<(Self::Output, Self::Output)> {
80        Some(match self {
81            UintTy::U8 => (u8::MIN.into(), u8::MAX.into()),
82            UintTy::U16 => (u16::MIN.into(), u16::MAX.into()),
83            UintTy::U32 => (u32::MIN.into(), u32::MAX.into()),
84            UintTy::U64 => (u64::MIN.into(), u64::MAX.into()),
85            UintTy::U128 => (u128::MIN, u128::MAX),
86            UintTy::Usize => (usize::MIN.try_into().ok()?, usize::MAX.try_into().ok()?),
87        })
88    }
89    fn bits(self) -> Self::Output {
90        match self {
91            UintTy::U8 => 8,
92            UintTy::U16 => 16,
93            UintTy::U32 => 32,
94            UintTy::U64 => 64,
95            UintTy::U128 => 128,
96            UintTy::Usize => usize::BITS.into(),
97        }
98    }
99}
100impl IntTypeBounds for IntTy {
101    type Output = i128;
102    fn min_max(self) -> Option<(Self::Output, Self::Output)> {
103        Some(match self {
104            IntTy::I8 => (i8::MIN.into(), i8::MAX.into()),
105            IntTy::I16 => (i16::MIN.into(), i16::MAX.into()),
106            IntTy::I32 => (i32::MIN.into(), i32::MAX.into()),
107            IntTy::I64 => (i64::MIN.into(), i64::MAX.into()),
108            IntTy::I128 => (i128::MIN, i128::MAX),
109            IntTy::Isize => (isize::MIN.try_into().ok()?, isize::MAX.try_into().ok()?),
110        })
111    }
112    fn bits(self) -> Self::Output {
113        match self {
114            IntTy::I8 => 8,
115            IntTy::I16 => 16,
116            IntTy::I32 => 32,
117            IntTy::I64 => 64,
118            IntTy::I128 => 128,
119            IntTy::Isize => isize::BITS.into(),
120        }
121    }
122}
123
124impl PartialEq for Constant {
125    fn eq(&self, other: &Self) -> bool {
126        match (self, other) {
127            (Self::Str(ls), Self::Str(rs)) => ls == rs,
128            (Self::Binary(l), Self::Binary(r)) => l == r,
129            (&Self::Char(l), &Self::Char(r)) => l == r,
130            (&Self::Int(l), &Self::Int(r)) => l == r,
131            (&Self::F64(l), &Self::F64(r)) => {
132                // `to_bits` is required to catch non-matching `0.0` and `-0.0`.
133                l.to_bits() == r.to_bits() && !l.is_nan()
134            },
135            (&Self::F32(l), &Self::F32(r)) => {
136                // `to_bits` is required to catch non-matching `0.0` and `-0.0`.
137                l.to_bits() == r.to_bits() && !l.is_nan()
138            },
139            (&Self::Bool(l), &Self::Bool(r)) => l == r,
140            (&Self::Vec(ref l), &Self::Vec(ref r)) | (&Self::Tuple(ref l), &Self::Tuple(ref r)) => l == r,
141            (Self::Repeat(lv, ls), Self::Repeat(rv, rs)) => ls == rs && lv == rv,
142            (Self::Ref(lb), Self::Ref(rb)) => *lb == *rb,
143            // TODO: are there inter-type equalities?
144            _ => false,
145        }
146    }
147}
148
149impl Hash for Constant {
150    fn hash<H>(&self, state: &mut H)
151    where
152        H: Hasher,
153    {
154        std::mem::discriminant(self).hash(state);
155        match *self {
156            Self::Adt(ref elem) => {
157                elem.hash(state);
158            },
159            Self::Str(ref s) => {
160                s.hash(state);
161            },
162            Self::Binary(ref b) => {
163                b.hash(state);
164            },
165            Self::Char(c) => {
166                c.hash(state);
167            },
168            Self::Int(i) => {
169                i.hash(state);
170            },
171            Self::F16(f) => {
172                // FIXME(f16_f128): once conversions to/from `f128` are available on all platforms,
173                f.hash(state);
174            },
175            Self::F32(f) => {
176                f64::from(f).to_bits().hash(state);
177            },
178            Self::F64(f) => {
179                f.to_bits().hash(state);
180            },
181            Self::F128(f) => {
182                f.hash(state);
183            },
184            Self::Bool(b) => {
185                b.hash(state);
186            },
187            Self::Vec(ref v) | Self::Tuple(ref v) => {
188                v.hash(state);
189            },
190            Self::Repeat(ref c, l) => {
191                c.hash(state);
192                l.hash(state);
193            },
194            Self::RawPtr(u) => {
195                u.hash(state);
196            },
197            Self::Ref(ref r) => {
198                r.hash(state);
199            },
200            Self::Err => {},
201        }
202    }
203}
204
205impl Constant {
206    pub fn partial_cmp(tcx: TyCtxt<'_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option<Ordering> {
207        match (left, right) {
208            (Self::Str(ls), Self::Str(rs)) => Some(ls.cmp(rs)),
209            (Self::Char(l), Self::Char(r)) => Some(l.cmp(r)),
210            (&Self::Int(l), &Self::Int(r)) => match *cmp_type.kind() {
211                ty::Int(int_ty) => Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty))),
212                ty::Uint(_) => Some(l.cmp(&r)),
213                _ => bug!("Not an int type"),
214            },
215            (&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r),
216            (&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r),
217            (Self::Bool(l), Self::Bool(r)) => Some(l.cmp(r)),
218            (Self::Tuple(l), Self::Tuple(r)) if l.len() == r.len() => match *cmp_type.kind() {
219                ty::Tuple(tys) if tys.len() == l.len() => l
220                    .iter()
221                    .zip(r)
222                    .zip(tys)
223                    .map(|((li, ri), cmp_type)| Self::partial_cmp(tcx, cmp_type, li, ri))
224                    .find(|r| r.is_none_or(|o| o != Ordering::Equal))
225                    .unwrap_or_else(|| Some(l.len().cmp(&r.len()))),
226                _ => None,
227            },
228            (Self::Vec(l), Self::Vec(r)) => {
229                let cmp_type = cmp_type.builtin_index()?;
230                iter::zip(l, r)
231                    .map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri))
232                    .find(|r| r.is_none_or(|o| o != Ordering::Equal))
233                    .unwrap_or_else(|| Some(l.len().cmp(&r.len())))
234            },
235            (Self::Repeat(lv, ls), Self::Repeat(rv, rs)) => {
236                match Self::partial_cmp(
237                    tcx,
238                    match *cmp_type.kind() {
239                        ty::Array(ty, _) => ty,
240                        _ => return None,
241                    },
242                    lv,
243                    rv,
244                ) {
245                    Some(Ordering::Equal) => Some(ls.cmp(rs)),
246                    x => x,
247                }
248            },
249            (Self::Ref(lb), Self::Ref(rb)) => Self::partial_cmp(
250                tcx,
251                match *cmp_type.kind() {
252                    ty::Ref(_, ty, _) => ty,
253                    _ => return None,
254                },
255                lb,
256                rb,
257            ),
258            // TODO: are there any useful inter-type orderings?
259            _ => None,
260        }
261    }
262
263    /// Returns the integer value or `None` if `self` or `val_type` is not integer type.
264    pub fn int_value(&self, tcx: TyCtxt<'_>, val_type: Ty<'_>) -> Option<FullInt> {
265        if let Constant::Int(const_int) = *self {
266            match *val_type.kind() {
267                ty::Int(ity) => Some(FullInt::S(sext(tcx, const_int, ity))),
268                ty::Uint(_) => Some(FullInt::U(const_int)),
269                _ => None,
270            }
271        } else {
272            None
273        }
274    }
275
276    #[must_use]
277    pub fn peel_refs(mut self) -> Self {
278        while let Constant::Ref(r) = self {
279            self = *r;
280        }
281        self
282    }
283
284    fn parse_f16(s: &str) -> Self {
285        let f: Half = s.parse().unwrap();
286        Self::F16(f.to_bits().try_into().unwrap())
287    }
288
289    fn parse_f128(s: &str) -> Self {
290        let f: Quad = s.parse().unwrap();
291        Self::F128(f.to_bits())
292    }
293
294    pub fn new_numeric_min<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<Self> {
295        match *ty.kind() {
296            ty::Uint(_) => Some(Self::Int(0)),
297            ty::Int(ty) => {
298                let val = match ty.normalize(tcx.sess.target.pointer_width) {
299                    IntTy::I8 => i128::from(i8::MIN),
300                    IntTy::I16 => i128::from(i16::MIN),
301                    IntTy::I32 => i128::from(i32::MIN),
302                    IntTy::I64 => i128::from(i64::MIN),
303                    IntTy::I128 => i128::MIN,
304                    IntTy::Isize => return None,
305                };
306                Some(Self::Int(val.cast_unsigned()))
307            },
308            ty::Char => Some(Self::Char(char::MIN)),
309            ty::Float(FloatTy::F32) => Some(Self::F32(f32::NEG_INFINITY)),
310            ty::Float(FloatTy::F64) => Some(Self::F64(f64::NEG_INFINITY)),
311            _ => None,
312        }
313    }
314
315    pub fn new_numeric_max<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<Self> {
316        match *ty.kind() {
317            ty::Uint(ty) => Some(Self::Int(match ty.normalize(tcx.sess.target.pointer_width) {
318                UintTy::U8 => u128::from(u8::MAX),
319                UintTy::U16 => u128::from(u16::MAX),
320                UintTy::U32 => u128::from(u32::MAX),
321                UintTy::U64 => u128::from(u64::MAX),
322                UintTy::U128 => u128::MAX,
323                UintTy::Usize => return None,
324            })),
325            ty::Int(ty) => {
326                let val = match ty.normalize(tcx.sess.target.pointer_width) {
327                    IntTy::I8 => i128::from(i8::MAX),
328                    IntTy::I16 => i128::from(i16::MAX),
329                    IntTy::I32 => i128::from(i32::MAX),
330                    IntTy::I64 => i128::from(i64::MAX),
331                    IntTy::I128 => i128::MAX,
332                    IntTy::Isize => return None,
333                };
334                Some(Self::Int(val.cast_unsigned()))
335            },
336            ty::Char => Some(Self::Char(char::MAX)),
337            ty::Float(FloatTy::F32) => Some(Self::F32(f32::INFINITY)),
338            ty::Float(FloatTy::F64) => Some(Self::F64(f64::INFINITY)),
339            _ => None,
340        }
341    }
342
343    pub fn is_numeric_min<'tcx>(&self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
344        match (self, ty.kind()) {
345            (&Self::Int(x), &ty::Uint(_)) => x == 0,
346            (&Self::Int(x), &ty::Int(ty)) => {
347                let limit = match ty.normalize(tcx.sess.target.pointer_width) {
348                    IntTy::I8 => i128::from(i8::MIN),
349                    IntTy::I16 => i128::from(i16::MIN),
350                    IntTy::I32 => i128::from(i32::MIN),
351                    IntTy::I64 => i128::from(i64::MIN),
352                    IntTy::I128 => i128::MIN,
353                    IntTy::Isize => return false,
354                };
355                x.cast_signed() == limit
356            },
357            (&Self::Char(x), &ty::Char) => x == char::MIN,
358            (&Self::F32(x), &ty::Float(FloatTy::F32)) => x == f32::NEG_INFINITY,
359            (&Self::F64(x), &ty::Float(FloatTy::F64)) => x == f64::NEG_INFINITY,
360            _ => false,
361        }
362    }
363
364    pub fn is_numeric_max<'tcx>(&self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
365        match (self, ty.kind()) {
366            (&Self::Int(x), &ty::Uint(ty)) => {
367                let limit = match ty.normalize(tcx.sess.target.pointer_width) {
368                    UintTy::U8 => u128::from(u8::MAX),
369                    UintTy::U16 => u128::from(u16::MAX),
370                    UintTy::U32 => u128::from(u32::MAX),
371                    UintTy::U64 => u128::from(u64::MAX),
372                    UintTy::U128 => u128::MAX,
373                    UintTy::Usize => return false,
374                };
375                x == limit
376            },
377            (&Self::Int(x), &ty::Int(ty)) => {
378                let limit = match ty.normalize(tcx.sess.target.pointer_width) {
379                    IntTy::I8 => i128::from(i8::MAX),
380                    IntTy::I16 => i128::from(i16::MAX),
381                    IntTy::I32 => i128::from(i32::MAX),
382                    IntTy::I64 => i128::from(i64::MAX),
383                    IntTy::I128 => i128::MAX,
384                    IntTy::Isize => return false,
385                };
386                x.cast_signed() == limit
387            },
388            (&Self::Char(x), &ty::Char) => x == char::MAX,
389            (&Self::F32(x), &ty::Float(FloatTy::F32)) => x == f32::INFINITY,
390            (&Self::F64(x), &ty::Float(FloatTy::F64)) => x == f64::INFINITY,
391            _ => false,
392        }
393    }
394
395    pub fn is_pos_infinity(&self) -> bool {
396        match *self {
397            // FIXME(f16_f128): add f16 and f128 when constants are available
398            Constant::F32(x) => x == f32::INFINITY,
399            Constant::F64(x) => x == f64::INFINITY,
400            _ => false,
401        }
402    }
403
404    pub fn is_neg_infinity(&self) -> bool {
405        match *self {
406            // FIXME(f16_f128): add f16 and f128 when constants are available
407            Constant::F32(x) => x == f32::NEG_INFINITY,
408            Constant::F64(x) => x == f64::NEG_INFINITY,
409            _ => false,
410        }
411    }
412}
413
414/// Parses a `LitKind` to a `Constant`.
415pub fn lit_to_mir_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
416    match *lit {
417        LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
418        LitKind::Byte(b) => Constant::Int(u128::from(b)),
419        LitKind::ByteStr(ref s, _) | LitKind::CStr(ref s, _) => Constant::Binary(s.as_byte_str().to_vec()),
420        LitKind::Char(c) => Constant::Char(c),
421        LitKind::Int(n, _) => Constant::Int(n.get()),
422        LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
423            // FIXME(f16_f128): just use `parse()` directly when available for `f16`/`f128`
424            FloatTy::F16 => Constant::parse_f16(is.as_str()),
425            FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
426            FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
427            FloatTy::F128 => Constant::parse_f128(is.as_str()),
428        },
429        LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() {
430            ty::Float(FloatTy::F16) => Constant::parse_f16(is.as_str()),
431            ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
432            ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
433            ty::Float(FloatTy::F128) => Constant::parse_f128(is.as_str()),
434            _ => bug!(),
435        },
436        LitKind::Bool(b) => Constant::Bool(b),
437        LitKind::Err(_) => Constant::Err,
438    }
439}
440
441/// The source of a constant value.
442#[derive(Clone, Copy)]
443pub enum ConstantSource {
444    /// The value is determined solely from the expression.
445    Local,
446    /// The value is dependent on another definition that may change independently from the local
447    /// expression.
448    NonLocal,
449}
450impl ConstantSource {
451    pub fn is_local(self) -> bool {
452        matches!(self, Self::Local)
453    }
454}
455
456#[derive(Copy, Clone, Debug, Eq)]
457pub enum FullInt {
458    S(i128),
459    U(u128),
460}
461
462impl PartialEq for FullInt {
463    fn eq(&self, other: &Self) -> bool {
464        self.cmp(other) == Ordering::Equal
465    }
466}
467
468impl PartialOrd for FullInt {
469    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
470        Some(self.cmp(other))
471    }
472}
473
474impl Ord for FullInt {
475    fn cmp(&self, other: &Self) -> Ordering {
476        use FullInt::{S, U};
477
478        fn cmp_s_u(s: i128, u: u128) -> Ordering {
479            u128::try_from(s).map_or(Ordering::Less, |x| x.cmp(&u))
480        }
481
482        match (*self, *other) {
483            (S(s), S(o)) => s.cmp(&o),
484            (U(s), U(o)) => s.cmp(&o),
485            (S(s), U(o)) => cmp_s_u(s, o),
486            (U(s), S(o)) => cmp_s_u(o, s).reverse(),
487        }
488    }
489}
490
491/// The context required to evaluate a constant expression.
492///
493/// This is currently limited to constant folding and reading the value of named constants.
494///
495/// See the module level documentation for some context.
496pub struct ConstEvalCtxt<'tcx> {
497    tcx: TyCtxt<'tcx>,
498    typing_env: ty::TypingEnv<'tcx>,
499    typeck: &'tcx TypeckResults<'tcx>,
500    source: Cell<ConstantSource>,
501    ctxt: Cell<SyntaxContext>,
502}
503
504impl<'tcx> ConstEvalCtxt<'tcx> {
505    /// Creates the evaluation context from the lint context. This requires the lint context to be
506    /// in a body (i.e. `cx.enclosing_body.is_some()`).
507    pub fn new(cx: &LateContext<'tcx>) -> Self {
508        Self {
509            tcx: cx.tcx,
510            typing_env: cx.typing_env(),
511            typeck: cx.typeck_results(),
512            source: Cell::new(ConstantSource::Local),
513            ctxt: Cell::new(SyntaxContext::root()),
514        }
515    }
516
517    /// Creates an evaluation context.
518    pub fn with_env(tcx: TyCtxt<'tcx>, typing_env: ty::TypingEnv<'tcx>, typeck: &'tcx TypeckResults<'tcx>) -> Self {
519        Self {
520            tcx,
521            typing_env,
522            typeck,
523            source: Cell::new(ConstantSource::Local),
524            ctxt: Cell::new(SyntaxContext::root()),
525        }
526    }
527
528    /// Attempts to evaluate the expression and returns both the value and whether it's dependant on
529    /// other items.
530    pub fn eval_with_source(&self, e: &Expr<'_>, ctxt: SyntaxContext) -> Option<(Constant, ConstantSource)> {
531        self.source.set(ConstantSource::Local);
532        self.ctxt.set(ctxt);
533        self.expr(e).map(|c| (c, self.source.get()))
534    }
535
536    /// Attempts to evaluate the expression.
537    pub fn eval(&self, e: &Expr<'_>) -> Option<Constant> {
538        self.expr(e)
539    }
540
541    /// Attempts to evaluate the expression without accessing other items.
542    ///
543    /// The context argument is the context used to view the evaluated expression. e.g. when
544    /// evaluating the argument in `f(m!(1))` the context of the call expression should be used.
545    /// This is need so the const evaluator can see the `m` macro and marke the evaluation as
546    /// non-local independant of what the macro expands to.
547    pub fn eval_local(&self, e: &Expr<'_>, ctxt: SyntaxContext) -> Option<Constant> {
548        match self.eval_with_source(e, ctxt) {
549            Some((x, ConstantSource::Local)) => Some(x),
550            _ => None,
551        }
552    }
553
554    /// Attempts to evaluate the expression as an integer without accessing other items.
555    ///
556    /// The context argument is the context used to view the evaluated expression. e.g. when
557    /// evaluating the argument in `f(m!(1))` the context of the call expression should be used.
558    /// This is need so the const evaluator can see the `m` macro and marke the evaluation as
559    /// non-local independant of what the macro expands to.
560    pub fn eval_full_int(&self, e: &Expr<'_>, ctxt: SyntaxContext) -> Option<FullInt> {
561        match self.eval_with_source(e, ctxt) {
562            Some((x, ConstantSource::Local)) => x.int_value(self.tcx, self.typeck.expr_ty(e)),
563            _ => None,
564        }
565    }
566
567    pub fn eval_pat_expr(&self, pat_expr: &PatExpr<'_>) -> Option<Constant> {
568        match &pat_expr.kind {
569            PatExprKind::Lit { lit, negated } => {
570                let ty = self.typeck.node_type_opt(pat_expr.hir_id);
571                let val = lit_to_mir_constant(&lit.node, ty);
572                if *negated {
573                    self.constant_negate(&val, ty?)
574                } else {
575                    Some(val)
576                }
577            },
578            PatExprKind::ConstBlock(ConstBlock { body, .. }) => self.expr(self.tcx.hir_body(*body).value),
579            PatExprKind::Path(qpath) => self.qpath(qpath, pat_expr.hir_id),
580        }
581    }
582
583    fn check_ctxt(&self, ctxt: SyntaxContext) {
584        if self.ctxt.get() != ctxt {
585            self.source.set(ConstantSource::NonLocal);
586        }
587    }
588
589    fn qpath(&self, qpath: &QPath<'_>, hir_id: HirId) -> Option<Constant> {
590        self.fetch_path(qpath, hir_id)
591            .and_then(|c| mir_to_const(self.tcx, c, self.typeck.node_type(hir_id)))
592    }
593
594    /// Simple constant folding: Insert an expression, get a constant or none.
595    fn expr(&self, e: &Expr<'_>) -> Option<Constant> {
596        self.check_ctxt(e.span.ctxt());
597        match e.kind {
598            ExprKind::ConstBlock(ConstBlock { body, .. }) => self.expr(self.tcx.hir_body(body).value),
599            ExprKind::DropTemps(e) => self.expr(e),
600            ExprKind::Path(ref qpath) => self.qpath(qpath, e.hir_id),
601            ExprKind::Block(block, _) => {
602                self.check_ctxt(block.span.ctxt());
603                self.block(block)
604            },
605            ExprKind::Lit(lit) => {
606                self.check_ctxt(lit.span.ctxt());
607                Some(lit_to_mir_constant(&lit.node, self.typeck.expr_ty_opt(e)))
608            },
609            ExprKind::Array(vec) => self.multi(vec).map(Constant::Vec),
610            ExprKind::Tup(tup) => self.multi(tup).map(Constant::Tuple),
611            ExprKind::Repeat(value, _) => {
612                let n = match self.typeck.expr_ty(e).kind() {
613                    ty::Array(_, n) => n.try_to_target_usize(self.tcx)?,
614                    _ => span_bug!(e.span, "typeck error"),
615                };
616                self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
617            },
618            ExprKind::Unary(op, operand) => self.expr(operand).and_then(|o| match op {
619                UnOp::Not => self.constant_not(&o, self.typeck.expr_ty(e)),
620                UnOp::Neg => self.constant_negate(&o, self.typeck.expr_ty(e)),
621                UnOp::Deref => Some(if let Constant::Ref(r) = o { *r } else { o }),
622            }),
623            ExprKind::If(cond, then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
624            ExprKind::Binary(op, left, right) => {
625                self.check_ctxt(e.span.ctxt());
626                self.binop(op.node, left, right)
627            },
628            ExprKind::Call(callee, []) => {
629                // We only handle a few const functions for now.
630                if let ExprKind::Path(qpath) = &callee.kind
631                    && let Some(did) = self.typeck.qpath_res(qpath, callee.hir_id).opt_def_id()
632                {
633                    match self.tcx.get_diagnostic_name(did) {
634                        Some(sym::i8_legacy_fn_max_value) => Some(Constant::Int(i8::MAX as u128)),
635                        Some(sym::i16_legacy_fn_max_value) => Some(Constant::Int(i16::MAX as u128)),
636                        Some(sym::i32_legacy_fn_max_value) => Some(Constant::Int(i32::MAX as u128)),
637                        Some(sym::i64_legacy_fn_max_value) => Some(Constant::Int(i64::MAX as u128)),
638                        Some(sym::i128_legacy_fn_max_value) => Some(Constant::Int(i128::MAX as u128)),
639                        _ => None,
640                    }
641                } else {
642                    None
643                }
644            },
645            ExprKind::Index(arr, index, _) => self.index(arr, index),
646            ExprKind::AddrOf(_, _, inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
647            ExprKind::Field(base, ref field)
648                if let base_ty = self.typeck.expr_ty(base)
649                    && match self.typeck.expr_adjustments(base) {
650                        [] => true,
651                        [.., a] => a.target == base_ty,
652                    }
653                    && let Some(Constant::Adt(constant)) = self.expr(base)
654                    && let ty::Adt(adt_def, _) = *base_ty.kind()
655                    && adt_def.is_struct()
656                    && let Some((desired_field, ty)) =
657                        field_of_struct(adt_def, self.tcx, constant, base_ty, field.name) =>
658            {
659                self.check_ctxt(field.span.ctxt());
660                mir_to_const(self.tcx, desired_field, ty)
661            },
662            _ => None,
663        }
664    }
665
666    /// Simple constant folding to determine if an expression is an empty slice, str, array, …
667    /// `None` will be returned if the constness cannot be determined, or if the resolution
668    /// leaves the local crate.
669    pub fn eval_is_empty(&self, e: &Expr<'_>) -> Option<bool> {
670        match e.kind {
671            ExprKind::ConstBlock(ConstBlock { body, .. }) => self.eval_is_empty(self.tcx.hir_body(body).value),
672            ExprKind::DropTemps(e) => self.eval_is_empty(e),
673            ExprKind::Lit(lit) => {
674                if is_direct_expn_of(e.span, sym::cfg).is_some() {
675                    None
676                } else {
677                    match &lit.node {
678                        LitKind::Str(is, _) => Some(is.is_empty()),
679                        LitKind::ByteStr(s, _) | LitKind::CStr(s, _) => Some(s.as_byte_str().is_empty()),
680                        _ => None,
681                    }
682                }
683            },
684            ExprKind::Array(vec) => self.multi(vec).map(|v| v.is_empty()),
685            ExprKind::Repeat(..) => {
686                if let ty::Array(_, n) = self.typeck.expr_ty(e).kind() {
687                    Some(n.try_to_target_usize(self.tcx)? == 0)
688                } else {
689                    span_bug!(e.span, "typeck error");
690                }
691            },
692            _ => None,
693        }
694    }
695
696    #[expect(clippy::cast_possible_wrap)]
697    fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
698        use self::Constant::{Bool, Int};
699        match *o {
700            Bool(b) => Some(Bool(!b)),
701            Int(value) => {
702                let value = !value;
703                match *ty.kind() {
704                    ty::Int(ity) => Some(Int(unsext(self.tcx, value as i128, ity))),
705                    ty::Uint(ity) => Some(Int(clip(self.tcx, value, ity))),
706                    _ => None,
707                }
708            },
709            _ => None,
710        }
711    }
712
713    fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
714        use self::Constant::{F32, F64, Int};
715        match *o {
716            Int(value) => {
717                let ty::Int(ity) = *ty.kind() else { return None };
718                let (min, _) = ity.min_max()?;
719                // sign extend
720                let value = sext(self.tcx, value, ity);
721
722                // Applying unary - to the most negative value of any signed integer type panics.
723                if value == min {
724                    return None;
725                }
726
727                let value = value.checked_neg()?;
728                // clear unused bits
729                Some(Int(unsext(self.tcx, value, ity)))
730            },
731            F32(f) => Some(F32(-f)),
732            F64(f) => Some(F64(-f)),
733            _ => None,
734        }
735    }
736
737    /// Create `Some(Vec![..])` of all constants, unless there is any
738    /// non-constant part.
739    fn multi(&self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
740        vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
741    }
742
743    /// Lookup a possibly constant expression from an `ExprKind::Path` and apply a function on it.
744    #[expect(clippy::too_many_lines)]
745    fn fetch_path(&self, qpath: &QPath<'_>, id: HirId) -> Option<ConstValue> {
746        // Resolve the path to a constant and check if that constant is known to
747        // not change based on the target.
748        //
749        // This should be replaced with an attribute at some point.
750        let did = match *qpath {
751            QPath::Resolved(None, path)
752                if path.span.ctxt() == self.ctxt.get()
753                    && path.segments.iter().all(|s| self.ctxt.get() == s.ident.span.ctxt())
754                    && let Res::Def(DefKind::Const, did) = path.res
755                    && (matches!(
756                        self.tcx.get_diagnostic_name(did),
757                        Some(
758                            sym::f32_legacy_const_digits
759                                | sym::f32_legacy_const_epsilon
760                                | sym::f32_legacy_const_infinity
761                                | sym::f32_legacy_const_mantissa_dig
762                                | sym::f32_legacy_const_max
763                                | sym::f32_legacy_const_max_10_exp
764                                | sym::f32_legacy_const_max_exp
765                                | sym::f32_legacy_const_min
766                                | sym::f32_legacy_const_min_10_exp
767                                | sym::f32_legacy_const_min_exp
768                                | sym::f32_legacy_const_min_positive
769                                | sym::f32_legacy_const_nan
770                                | sym::f32_legacy_const_neg_infinity
771                                | sym::f32_legacy_const_radix
772                                | sym::f64_legacy_const_digits
773                                | sym::f64_legacy_const_epsilon
774                                | sym::f64_legacy_const_infinity
775                                | sym::f64_legacy_const_mantissa_dig
776                                | sym::f64_legacy_const_max
777                                | sym::f64_legacy_const_max_10_exp
778                                | sym::f64_legacy_const_max_exp
779                                | sym::f64_legacy_const_min
780                                | sym::f64_legacy_const_min_10_exp
781                                | sym::f64_legacy_const_min_exp
782                                | sym::f64_legacy_const_min_positive
783                                | sym::f64_legacy_const_nan
784                                | sym::f64_legacy_const_neg_infinity
785                                | sym::f64_legacy_const_radix
786                                | sym::u8_legacy_const_min
787                                | sym::u16_legacy_const_min
788                                | sym::u32_legacy_const_min
789                                | sym::u64_legacy_const_min
790                                | sym::u128_legacy_const_min
791                                | sym::usize_legacy_const_min
792                                | sym::u8_legacy_const_max
793                                | sym::u16_legacy_const_max
794                                | sym::u32_legacy_const_max
795                                | sym::u64_legacy_const_max
796                                | sym::u128_legacy_const_max
797                                | sym::i8_legacy_const_min
798                                | sym::i16_legacy_const_min
799                                | sym::i32_legacy_const_min
800                                | sym::i64_legacy_const_min
801                                | sym::i128_legacy_const_min
802                                | sym::i8_legacy_const_max
803                                | sym::i16_legacy_const_max
804                                | sym::i32_legacy_const_max
805                                | sym::i64_legacy_const_max
806                                | sym::i128_legacy_const_max
807                        )
808                    ) || self.tcx.opt_parent(did).is_some_and(|parent| {
809                        parent.is_diag_item(&self.tcx, sym::f16_consts_mod)
810                            || parent.is_diag_item(&self.tcx, sym::f32_consts_mod)
811                            || parent.is_diag_item(&self.tcx, sym::f64_consts_mod)
812                            || parent.is_diag_item(&self.tcx, sym::f128_consts_mod)
813                    })) =>
814            {
815                did
816            },
817            QPath::TypeRelative(ty, const_name)
818                if let TyKind::Path(QPath::Resolved(None, ty_path)) = ty.kind
819                    && let [.., ty_name] = ty_path.segments
820                    && (matches!(
821                        ty_name.ident.name,
822                        sym::i8
823                            | sym::i16
824                            | sym::i32
825                            | sym::i64
826                            | sym::i128
827                            | sym::u8
828                            | sym::u16
829                            | sym::u32
830                            | sym::u64
831                            | sym::u128
832                            | sym::f32
833                            | sym::f64
834                            | sym::char
835                    ) || (ty_name.ident.name == sym::usize && const_name.ident.name == sym::MIN))
836                    && const_name.ident.span.ctxt() == self.ctxt.get()
837                    && ty.span.ctxt() == self.ctxt.get()
838                    && ty_name.ident.span.ctxt() == self.ctxt.get()
839                    && matches!(ty_path.res, Res::PrimTy(_))
840                    && let Some((DefKind::AssocConst, did)) = self.typeck.type_dependent_def(id) =>
841            {
842                did
843            },
844            _ if let Res::Def(DefKind::Const | DefKind::AssocConst, did) = self.typeck.qpath_res(qpath, id) => {
845                self.source.set(ConstantSource::NonLocal);
846                did
847            },
848            _ => return None,
849        };
850
851        self.tcx
852            .const_eval_resolve(
853                self.typing_env,
854                mir::UnevaluatedConst::new(did, self.typeck.node_args(id)),
855                qpath.span(),
856            )
857            .ok()
858    }
859
860    fn index(&self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
861        let lhs = self.expr(lhs);
862        let index = self.expr(index);
863
864        match (lhs, index) {
865            (Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec.get(index as usize) {
866                Some(Constant::F16(x)) => Some(Constant::F16(*x)),
867                Some(Constant::F32(x)) => Some(Constant::F32(*x)),
868                Some(Constant::F64(x)) => Some(Constant::F64(*x)),
869                Some(Constant::F128(x)) => Some(Constant::F128(*x)),
870                _ => None,
871            },
872            (Some(Constant::Vec(vec)), _) => {
873                if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
874                    match vec.first() {
875                        Some(Constant::F16(x)) => Some(Constant::F16(*x)),
876                        Some(Constant::F32(x)) => Some(Constant::F32(*x)),
877                        Some(Constant::F64(x)) => Some(Constant::F64(*x)),
878                        Some(Constant::F128(x)) => Some(Constant::F128(*x)),
879                        _ => None,
880                    }
881                } else {
882                    None
883                }
884            },
885            _ => None,
886        }
887    }
888
889    /// A block can only yield a constant if it has exactly one constant expression.
890    fn block(&self, block: &Block<'_>) -> Option<Constant> {
891        if block.stmts.is_empty()
892            && let Some(expr) = block.expr
893        {
894            // Try to detect any `cfg`ed statements or empty macro expansions.
895            let span = block.span.data();
896            if span.ctxt == SyntaxContext::root() {
897                if let Some(expr_span) = walk_span_to_context(expr.span, span.ctxt)
898                    && let expr_lo = expr_span.lo()
899                    && expr_lo >= span.lo
900                    && let Some(src) = (span.lo..expr_lo).get_source_range(&self.tcx)
901                    && let Some(src) = src.as_str()
902                {
903                    use rustc_lexer::TokenKind::{BlockComment, LineComment, OpenBrace, Semi, Whitespace};
904                    if !tokenize(src, FrontmatterAllowed::No)
905                        .map(|t| t.kind)
906                        .filter(|t| !matches!(t, Whitespace | LineComment { .. } | BlockComment { .. } | Semi))
907                        .eq([OpenBrace])
908                    {
909                        self.source.set(ConstantSource::NonLocal);
910                    }
911                } else {
912                    // Unable to access the source. Assume a non-local dependency.
913                    self.source.set(ConstantSource::NonLocal);
914                }
915            }
916
917            self.expr(expr)
918        } else {
919            None
920        }
921    }
922
923    fn ifthenelse(&self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
924        if let Some(Constant::Bool(b)) = self.expr(cond) {
925            if b {
926                self.expr(then)
927            } else {
928                otherwise.as_ref().and_then(|expr| self.expr(expr))
929            }
930        } else {
931            None
932        }
933    }
934
935    fn binop(&self, op: BinOpKind, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
936        let l = self.expr(left)?;
937        let r = self.expr(right);
938        match (l, r) {
939            (Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck.expr_ty_opt(left)?.kind() {
940                ty::Int(ity) => {
941                    let (ty_min_value, _) = ity.min_max()?;
942                    let bits = ity.bits();
943                    let l = sext(self.tcx, l, ity);
944                    let r = sext(self.tcx, r, ity);
945
946                    // Using / or %, where the left-hand argument is the smallest integer of a signed integer type and
947                    // the right-hand argument is -1 always panics, even with overflow-checks disabled
948                    if let BinOpKind::Div | BinOpKind::Rem = op
949                        && l == ty_min_value
950                        && r == -1
951                    {
952                        return None;
953                    }
954
955                    let zext = |n: i128| Constant::Int(unsext(self.tcx, n, ity));
956                    match op {
957                        // When +, * or binary - create a value greater than the maximum value, or less than
958                        // the minimum value that can be stored, it panics.
959                        BinOpKind::Add => l.checked_add(r).and_then(|n| ity.ensure_fits(n)).map(zext),
960                        BinOpKind::Sub => l.checked_sub(r).and_then(|n| ity.ensure_fits(n)).map(zext),
961                        BinOpKind::Mul => l.checked_mul(r).and_then(|n| ity.ensure_fits(n)).map(zext),
962                        BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
963                        BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
964                        // Using << or >> where the right-hand argument is greater than or equal to the number of bits
965                        // in the type of the left-hand argument, or is negative panics.
966                        BinOpKind::Shr if r < bits && !r.is_negative() => l.checked_shr(r.try_into().ok()?).map(zext),
967                        BinOpKind::Shl if r < bits && !r.is_negative() => l.checked_shl(r.try_into().ok()?).map(zext),
968                        BinOpKind::BitXor => Some(zext(l ^ r)),
969                        BinOpKind::BitOr => Some(zext(l | r)),
970                        BinOpKind::BitAnd => Some(zext(l & r)),
971                        // FIXME: f32/f64 currently consider `0.0` and `-0.0` as different.
972                        BinOpKind::Eq => Some(Constant::Bool(l == r)),
973                        BinOpKind::Ne => Some(Constant::Bool(l != r)),
974                        BinOpKind::Lt => Some(Constant::Bool(l < r)),
975                        BinOpKind::Le => Some(Constant::Bool(l <= r)),
976                        BinOpKind::Ge => Some(Constant::Bool(l >= r)),
977                        BinOpKind::Gt => Some(Constant::Bool(l > r)),
978                        _ => None,
979                    }
980                },
981                ty::Uint(ity) => {
982                    let bits = ity.bits();
983
984                    match op {
985                        BinOpKind::Add => l.checked_add(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
986                        BinOpKind::Sub => l.checked_sub(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
987                        BinOpKind::Mul => l.checked_mul(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
988                        BinOpKind::Div => l.checked_div(r).map(Constant::Int),
989                        BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
990                        BinOpKind::Shr if r < bits => l.checked_shr(r.try_into().ok()?).map(Constant::Int),
991                        BinOpKind::Shl if r < bits => l.checked_shl(r.try_into().ok()?).map(Constant::Int),
992                        BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
993                        BinOpKind::BitOr => Some(Constant::Int(l | r)),
994                        BinOpKind::BitAnd => Some(Constant::Int(l & r)),
995                        BinOpKind::Eq => Some(Constant::Bool(l == r)),
996                        BinOpKind::Ne => Some(Constant::Bool(l != r)),
997                        BinOpKind::Lt => Some(Constant::Bool(l < r)),
998                        BinOpKind::Le => Some(Constant::Bool(l <= r)),
999                        BinOpKind::Ge => Some(Constant::Bool(l >= r)),
1000                        BinOpKind::Gt => Some(Constant::Bool(l > r)),
1001                        _ => None,
1002                    }
1003                },
1004                _ => None,
1005            },
1006            // FIXME(f16_f128): add these types when binary operations are available on all platforms
1007            (Constant::F32(l), Some(Constant::F32(r))) => match op {
1008                BinOpKind::Add => Some(Constant::F32(l + r)),
1009                BinOpKind::Sub => Some(Constant::F32(l - r)),
1010                BinOpKind::Mul => Some(Constant::F32(l * r)),
1011                BinOpKind::Div => Some(Constant::F32(l / r)),
1012                BinOpKind::Rem => Some(Constant::F32(l % r)),
1013                BinOpKind::Eq => Some(Constant::Bool(l == r)),
1014                BinOpKind::Ne => Some(Constant::Bool(l != r)),
1015                BinOpKind::Lt => Some(Constant::Bool(l < r)),
1016                BinOpKind::Le => Some(Constant::Bool(l <= r)),
1017                BinOpKind::Ge => Some(Constant::Bool(l >= r)),
1018                BinOpKind::Gt => Some(Constant::Bool(l > r)),
1019                _ => None,
1020            },
1021            (Constant::F64(l), Some(Constant::F64(r))) => match op {
1022                BinOpKind::Add => Some(Constant::F64(l + r)),
1023                BinOpKind::Sub => Some(Constant::F64(l - r)),
1024                BinOpKind::Mul => Some(Constant::F64(l * r)),
1025                BinOpKind::Div => Some(Constant::F64(l / r)),
1026                BinOpKind::Rem => Some(Constant::F64(l % r)),
1027                BinOpKind::Eq => Some(Constant::Bool(l == r)),
1028                BinOpKind::Ne => Some(Constant::Bool(l != r)),
1029                BinOpKind::Lt => Some(Constant::Bool(l < r)),
1030                BinOpKind::Le => Some(Constant::Bool(l <= r)),
1031                BinOpKind::Ge => Some(Constant::Bool(l >= r)),
1032                BinOpKind::Gt => Some(Constant::Bool(l > r)),
1033                _ => None,
1034            },
1035            (l, r) => match (op, l, r) {
1036                (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
1037                (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
1038                (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
1039                    Some(r)
1040                },
1041                (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
1042                (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
1043                (BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
1044                _ => None,
1045            },
1046        }
1047    }
1048}
1049
1050pub fn mir_to_const<'tcx>(tcx: TyCtxt<'tcx>, val: ConstValue, ty: Ty<'tcx>) -> Option<Constant> {
1051    match (val, ty.kind()) {
1052        (_, &ty::Adt(adt_def, _)) if adt_def.is_struct() => Some(Constant::Adt(val)),
1053        (ConstValue::Scalar(Scalar::Int(int)), _) => match ty.kind() {
1054            ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
1055            ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.to_bits(int.size()))),
1056            ty::Float(FloatTy::F16) => Some(Constant::F16(int.into())),
1057            ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(int.into()))),
1058            ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(int.into()))),
1059            ty::Float(FloatTy::F128) => Some(Constant::F128(int.into())),
1060            ty::RawPtr(_, _) => Some(Constant::RawPtr(int.to_bits(int.size()))),
1061            _ => None,
1062        },
1063        (_, ty::Ref(_, inner_ty, _)) if matches!(inner_ty.kind(), ty::Str) => {
1064            let data = val.try_get_slice_bytes_for_diagnostics(tcx)?;
1065            String::from_utf8(data.to_owned()).ok().map(Constant::Str)
1066        },
1067        (ConstValue::Indirect { alloc_id, offset }, ty::Array(sub_type, len)) => {
1068            let alloc = tcx.global_alloc(alloc_id).unwrap_memory().inner();
1069            let len = len.try_to_target_usize(tcx)?;
1070            let ty::Float(flt) = sub_type.kind() else {
1071                return None;
1072            };
1073            let size = Size::from_bits(flt.bit_width());
1074            let mut res = Vec::new();
1075            for idx in 0..len {
1076                let range = alloc_range(offset + size * idx, size);
1077                let val = alloc.read_scalar(&tcx, range, /* read_provenance */ false).ok()?;
1078                res.push(match flt {
1079                    FloatTy::F16 => Constant::F16(val.to_u16().discard_err()?),
1080                    FloatTy::F32 => Constant::F32(f32::from_bits(val.to_u32().discard_err()?)),
1081                    FloatTy::F64 => Constant::F64(f64::from_bits(val.to_u64().discard_err()?)),
1082                    FloatTy::F128 => Constant::F128(val.to_u128().discard_err()?),
1083                });
1084            }
1085            Some(Constant::Vec(res))
1086        },
1087        _ => None,
1088    }
1089}
1090
1091fn field_of_struct<'tcx>(
1092    adt_def: ty::AdtDef<'tcx>,
1093    tcx: TyCtxt<'tcx>,
1094    value: ConstValue,
1095    ty: Ty<'tcx>,
1096    field: Symbol,
1097) -> Option<(ConstValue, Ty<'tcx>)> {
1098    if let Some(dc) = tcx.try_destructure_mir_constant_for_user_output(value, ty)
1099        && let Some(dc_variant) = dc.variant
1100        && let Some(variant) = adt_def.variants().get(dc_variant)
1101        && let Some(field_idx) = variant.fields.iter().position(|el| el.name == field)
1102    {
1103        dc.fields.get(field_idx).copied()
1104    } else {
1105        None
1106    }
1107}
1108
1109/// If `expr` evaluates to an integer constant, return its value.
1110///
1111/// The context argument is the context used to view the evaluated expression. e.g. when evaluating
1112/// the argument in `f(m!(1))` the context of the call expression should be used. This is need so
1113/// the const evaluator can see the `m` macro and marke the evaluation as non-local independant of
1114/// what the macro expands to.
1115pub fn integer_const(cx: &LateContext<'_>, expr: &Expr<'_>, ctxt: SyntaxContext) -> Option<u128> {
1116    if let Some(Constant::Int(value)) = ConstEvalCtxt::new(cx).eval_local(expr, ctxt) {
1117        Some(value)
1118    } else {
1119        None
1120    }
1121}
1122
1123/// Check if `expr` evaluates to an integer constant of 0.
1124///
1125/// The context argument is the context used to view the evaluated expression. e.g. when evaluating
1126/// the argument in `f(m!(1))` the context of the call expression should be used. This is need so
1127/// the const evaluator can see the `m` macro and marke the evaluation as non-local independant of
1128/// what the macro expands to.
1129#[inline]
1130pub fn is_zero_integer_const(cx: &LateContext<'_>, expr: &Expr<'_>, ctxt: SyntaxContext) -> bool {
1131    integer_const(cx, expr, ctxt) == Some(0)
1132}
clippy_utils/consts.rs

clippy_utils/
consts.rs
