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#![allow(clippy::float_cmp)]
6
7use crate::source::{SpanRangeExt, walk_span_to_context};
8use crate::{clip, is_direct_expn_of, paths, sext, sym, unsext};
9
10use rustc_abi::Size;
11use rustc_apfloat::Float;
12use rustc_apfloat::ieee::{Half, Quad};
13use rustc_ast::ast::{LitFloatType, LitKind};
14use rustc_hir::def::{DefKind, Res};
15use rustc_hir::{BinOpKind, Block, ConstBlock, Expr, ExprKind, HirId, PatExpr, PatExprKind, QPath, TyKind, UnOp};
16use rustc_lexer::{FrontmatterAllowed, tokenize};
17use rustc_lint::LateContext;
18use rustc_middle::mir::ConstValue;
19use rustc_middle::mir::interpret::{Scalar, alloc_range};
20use rustc_middle::ty::{self, FloatTy, IntTy, ScalarInt, Ty, TyCtxt, TypeckResults, UintTy};
21use rustc_middle::{bug, mir, span_bug};
22use rustc_span::{Symbol, SyntaxContext};
23use std::cell::Cell;
24use std::cmp::Ordering;
25use std::hash::{Hash, Hasher};
26use std::iter;
27
28/// A `LitKind`-like enum to fold constant `Expr`s into.
29#[derive(Debug, Clone)]
30pub enum Constant {
31    Adt(ConstValue),
32    /// A `String` (e.g., "abc").
33    Str(String),
34    /// A binary string (e.g., `b"abc"`).
35    Binary(Vec<u8>),
36    /// A single `char` (e.g., `'a'`).
37    Char(char),
38    /// An integer's bit representation.
39    Int(u128),
40    /// An `f16` bitcast to a `u16`.
41    // FIXME(f16_f128): use `f16` once builtins are available on all host tools platforms.
42    F16(u16),
43    /// An `f32`.
44    F32(f32),
45    /// An `f64`.
46    F64(f64),
47    /// An `f128` bitcast to a `u128`.
48    // FIXME(f16_f128): use `f128` once builtins are available on all host tools platforms.
49    F128(u128),
50    /// `true` or `false`.
51    Bool(bool),
52    /// An array of constants.
53    Vec(Vec<Constant>),
54    /// Also an array, but with only one constant, repeated N times.
55    Repeat(Box<Constant>, u64),
56    /// A tuple of constants.
57    Tuple(Vec<Constant>),
58    /// A raw pointer.
59    RawPtr(u128),
60    /// A reference
61    Ref(Box<Constant>),
62    /// A literal with syntax error.
63    Err,
64}
65
66trait IntTypeBounds: Sized {
67    type Output: PartialOrd;
68
69    fn min_max(self) -> Option<(Self::Output, Self::Output)>;
70    fn bits(self) -> Self::Output;
71    fn ensure_fits(self, val: Self::Output) -> Option<Self::Output> {
72        let (min, max) = self.min_max()?;
73        (min <= val && val <= max).then_some(val)
74    }
75}
76impl IntTypeBounds for UintTy {
77    type Output = u128;
78    fn min_max(self) -> Option<(Self::Output, Self::Output)> {
79        Some(match self {
80            UintTy::U8 => (u8::MIN.into(), u8::MAX.into()),
81            UintTy::U16 => (u16::MIN.into(), u16::MAX.into()),
82            UintTy::U32 => (u32::MIN.into(), u32::MAX.into()),
83            UintTy::U64 => (u64::MIN.into(), u64::MAX.into()),
84            UintTy::U128 => (u128::MIN, u128::MAX),
85            UintTy::Usize => (usize::MIN.try_into().ok()?, usize::MAX.try_into().ok()?),
86        })
87    }
88    fn bits(self) -> Self::Output {
89        match self {
90            UintTy::U8 => 8,
91            UintTy::U16 => 16,
92            UintTy::U32 => 32,
93            UintTy::U64 => 64,
94            UintTy::U128 => 128,
95            UintTy::Usize => usize::BITS.into(),
96        }
97    }
98}
99impl IntTypeBounds for IntTy {
100    type Output = i128;
101    fn min_max(self) -> Option<(Self::Output, Self::Output)> {
102        Some(match self {
103            IntTy::I8 => (i8::MIN.into(), i8::MAX.into()),
104            IntTy::I16 => (i16::MIN.into(), i16::MAX.into()),
105            IntTy::I32 => (i32::MIN.into(), i32::MAX.into()),
106            IntTy::I64 => (i64::MIN.into(), i64::MAX.into()),
107            IntTy::I128 => (i128::MIN, i128::MAX),
108            IntTy::Isize => (isize::MIN.try_into().ok()?, isize::MAX.try_into().ok()?),
109        })
110    }
111    fn bits(self) -> Self::Output {
112        match self {
113            IntTy::I8 => 8,
114            IntTy::I16 => 16,
115            IntTy::I32 => 32,
116            IntTy::I64 => 64,
117            IntTy::I128 => 128,
118            IntTy::Isize => isize::BITS.into(),
119        }
120    }
121}
122
123impl PartialEq for Constant {
124    fn eq(&self, other: &Self) -> bool {
125        match (self, other) {
126            (Self::Str(ls), Self::Str(rs)) => ls == rs,
127            (Self::Binary(l), Self::Binary(r)) => l == r,
128            (&Self::Char(l), &Self::Char(r)) => l == r,
129            (&Self::Int(l), &Self::Int(r)) => l == r,
130            (&Self::F64(l), &Self::F64(r)) => {
131                // `to_bits` is required to catch non-matching `0.0` and `-0.0`.
132                l.to_bits() == r.to_bits() && !l.is_nan()
133            },
134            (&Self::F32(l), &Self::F32(r)) => {
135                // `to_bits` is required to catch non-matching `0.0` and `-0.0`.
136                l.to_bits() == r.to_bits() && !l.is_nan()
137            },
138            (&Self::Bool(l), &Self::Bool(r)) => l == r,
139            (&Self::Vec(ref l), &Self::Vec(ref r)) | (&Self::Tuple(ref l), &Self::Tuple(ref r)) => l == r,
140            (Self::Repeat(lv, ls), Self::Repeat(rv, rs)) => ls == rs && lv == rv,
141            (Self::Ref(lb), Self::Ref(rb)) => *lb == *rb,
142            // TODO: are there inter-type equalities?
143            _ => false,
144        }
145    }
146}
147
148impl Hash for Constant {
149    fn hash<H>(&self, state: &mut H)
150    where
151        H: Hasher,
152    {
153        std::mem::discriminant(self).hash(state);
154        match *self {
155            Self::Adt(ref elem) => {
156                elem.hash(state);
157            },
158            Self::Str(ref s) => {
159                s.hash(state);
160            },
161            Self::Binary(ref b) => {
162                b.hash(state);
163            },
164            Self::Char(c) => {
165                c.hash(state);
166            },
167            Self::Int(i) => {
168                i.hash(state);
169            },
170            Self::F16(f) => {
171                // FIXME(f16_f128): once conversions to/from `f128` are available on all platforms,
172                f.hash(state);
173            },
174            Self::F32(f) => {
175                f64::from(f).to_bits().hash(state);
176            },
177            Self::F64(f) => {
178                f.to_bits().hash(state);
179            },
180            Self::F128(f) => {
181                f.hash(state);
182            },
183            Self::Bool(b) => {
184                b.hash(state);
185            },
186            Self::Vec(ref v) | Self::Tuple(ref v) => {
187                v.hash(state);
188            },
189            Self::Repeat(ref c, l) => {
190                c.hash(state);
191                l.hash(state);
192            },
193            Self::RawPtr(u) => {
194                u.hash(state);
195            },
196            Self::Ref(ref r) => {
197                r.hash(state);
198            },
199            Self::Err => {},
200        }
201    }
202}
203
204impl Constant {
205    pub fn partial_cmp(tcx: TyCtxt<'_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option<Ordering> {
206        match (left, right) {
207            (Self::Str(ls), Self::Str(rs)) => Some(ls.cmp(rs)),
208            (Self::Char(l), Self::Char(r)) => Some(l.cmp(r)),
209            (&Self::Int(l), &Self::Int(r)) => match *cmp_type.kind() {
210                ty::Int(int_ty) => Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty))),
211                ty::Uint(_) => Some(l.cmp(&r)),
212                _ => bug!("Not an int type"),
213            },
214            (&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r),
215            (&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r),
216            (Self::Bool(l), Self::Bool(r)) => Some(l.cmp(r)),
217            (Self::Tuple(l), Self::Tuple(r)) if l.len() == r.len() => match *cmp_type.kind() {
218                ty::Tuple(tys) if tys.len() == l.len() => l
219                    .iter()
220                    .zip(r)
221                    .zip(tys)
222                    .map(|((li, ri), cmp_type)| Self::partial_cmp(tcx, cmp_type, li, ri))
223                    .find(|r| r.is_none_or(|o| o != Ordering::Equal))
224                    .unwrap_or_else(|| Some(l.len().cmp(&r.len()))),
225                _ => None,
226            },
227            (Self::Vec(l), Self::Vec(r)) => {
228                let cmp_type = cmp_type.builtin_index()?;
229                iter::zip(l, r)
230                    .map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri))
231                    .find(|r| r.is_none_or(|o| o != Ordering::Equal))
232                    .unwrap_or_else(|| Some(l.len().cmp(&r.len())))
233            },
234            (Self::Repeat(lv, ls), Self::Repeat(rv, rs)) => {
235                match Self::partial_cmp(
236                    tcx,
237                    match *cmp_type.kind() {
238                        ty::Array(ty, _) => ty,
239                        _ => return None,
240                    },
241                    lv,
242                    rv,
243                ) {
244                    Some(Ordering::Equal) => Some(ls.cmp(rs)),
245                    x => x,
246                }
247            },
248            (Self::Ref(lb), Self::Ref(rb)) => Self::partial_cmp(
249                tcx,
250                match *cmp_type.kind() {
251                    ty::Ref(_, ty, _) => ty,
252                    _ => return None,
253                },
254                lb,
255                rb,
256            ),
257            // TODO: are there any useful inter-type orderings?
258            _ => None,
259        }
260    }
261
262    /// Returns the integer value or `None` if `self` or `val_type` is not integer type.
263    pub fn int_value(&self, tcx: TyCtxt<'_>, val_type: Ty<'_>) -> Option<FullInt> {
264        if let Constant::Int(const_int) = *self {
265            match *val_type.kind() {
266                ty::Int(ity) => Some(FullInt::S(sext(tcx, const_int, ity))),
267                ty::Uint(_) => Some(FullInt::U(const_int)),
268                _ => None,
269            }
270        } else {
271            None
272        }
273    }
274
275    #[must_use]
276    pub fn peel_refs(mut self) -> Self {
277        while let Constant::Ref(r) = self {
278            self = *r;
279        }
280        self
281    }
282
283    fn parse_f16(s: &str) -> Self {
284        let f: Half = s.parse().unwrap();
285        Self::F16(f.to_bits().try_into().unwrap())
286    }
287
288    fn parse_f128(s: &str) -> Self {
289        let f: Quad = s.parse().unwrap();
290        Self::F128(f.to_bits())
291    }
292
293    pub fn new_numeric_min<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<Self> {
294        match *ty.kind() {
295            ty::Uint(_) => Some(Self::Int(0)),
296            ty::Int(ty) => {
297                let val = match ty.normalize(tcx.sess.target.pointer_width) {
298                    IntTy::I8 => i128::from(i8::MIN),
299                    IntTy::I16 => i128::from(i16::MIN),
300                    IntTy::I32 => i128::from(i32::MIN),
301                    IntTy::I64 => i128::from(i64::MIN),
302                    IntTy::I128 => i128::MIN,
303                    IntTy::Isize => return None,
304                };
305                Some(Self::Int(val.cast_unsigned()))
306            },
307            ty::Char => Some(Self::Char(char::MIN)),
308            ty::Float(FloatTy::F32) => Some(Self::F32(f32::NEG_INFINITY)),
309            ty::Float(FloatTy::F64) => Some(Self::F64(f64::NEG_INFINITY)),
310            _ => None,
311        }
312    }
313
314    pub fn new_numeric_max<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<Self> {
315        match *ty.kind() {
316            ty::Uint(ty) => Some(Self::Int(match ty.normalize(tcx.sess.target.pointer_width) {
317                UintTy::U8 => u128::from(u8::MAX),
318                UintTy::U16 => u128::from(u16::MAX),
319                UintTy::U32 => u128::from(u32::MAX),
320                UintTy::U64 => u128::from(u64::MAX),
321                UintTy::U128 => u128::MAX,
322                UintTy::Usize => return None,
323            })),
324            ty::Int(ty) => {
325                let val = match ty.normalize(tcx.sess.target.pointer_width) {
326                    IntTy::I8 => i128::from(i8::MAX),
327                    IntTy::I16 => i128::from(i16::MAX),
328                    IntTy::I32 => i128::from(i32::MAX),
329                    IntTy::I64 => i128::from(i64::MAX),
330                    IntTy::I128 => i128::MAX,
331                    IntTy::Isize => return None,
332                };
333                Some(Self::Int(val.cast_unsigned()))
334            },
335            ty::Char => Some(Self::Char(char::MAX)),
336            ty::Float(FloatTy::F32) => Some(Self::F32(f32::INFINITY)),
337            ty::Float(FloatTy::F64) => Some(Self::F64(f64::INFINITY)),
338            _ => None,
339        }
340    }
341
342    pub fn is_numeric_min<'tcx>(&self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
343        match (self, ty.kind()) {
344            (&Self::Int(x), &ty::Uint(_)) => x == 0,
345            (&Self::Int(x), &ty::Int(ty)) => {
346                let limit = match ty.normalize(tcx.sess.target.pointer_width) {
347                    IntTy::I8 => i128::from(i8::MIN),
348                    IntTy::I16 => i128::from(i16::MIN),
349                    IntTy::I32 => i128::from(i32::MIN),
350                    IntTy::I64 => i128::from(i64::MIN),
351                    IntTy::I128 => i128::MIN,
352                    IntTy::Isize => return false,
353                };
354                x.cast_signed() == limit
355            },
356            (&Self::Char(x), &ty::Char) => x == char::MIN,
357            (&Self::F32(x), &ty::Float(FloatTy::F32)) => x == f32::NEG_INFINITY,
358            (&Self::F64(x), &ty::Float(FloatTy::F64)) => x == f64::NEG_INFINITY,
359            _ => false,
360        }
361    }
362
363    pub fn is_numeric_max<'tcx>(&self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
364        match (self, ty.kind()) {
365            (&Self::Int(x), &ty::Uint(ty)) => {
366                let limit = match ty.normalize(tcx.sess.target.pointer_width) {
367                    UintTy::U8 => u128::from(u8::MAX),
368                    UintTy::U16 => u128::from(u16::MAX),
369                    UintTy::U32 => u128::from(u32::MAX),
370                    UintTy::U64 => u128::from(u64::MAX),
371                    UintTy::U128 => u128::MAX,
372                    UintTy::Usize => return false,
373                };
374                x == limit
375            },
376            (&Self::Int(x), &ty::Int(ty)) => {
377                let limit = match ty.normalize(tcx.sess.target.pointer_width) {
378                    IntTy::I8 => i128::from(i8::MAX),
379                    IntTy::I16 => i128::from(i16::MAX),
380                    IntTy::I32 => i128::from(i32::MAX),
381                    IntTy::I64 => i128::from(i64::MAX),
382                    IntTy::I128 => i128::MAX,
383                    IntTy::Isize => return false,
384                };
385                x.cast_signed() == limit
386            },
387            (&Self::Char(x), &ty::Char) => x == char::MAX,
388            (&Self::F32(x), &ty::Float(FloatTy::F32)) => x == f32::INFINITY,
389            (&Self::F64(x), &ty::Float(FloatTy::F64)) => x == f64::INFINITY,
390            _ => false,
391        }
392    }
393
394    pub fn is_pos_infinity(&self) -> bool {
395        match *self {
396            // FIXME(f16_f128): add f16 and f128 when constants are available
397            Constant::F32(x) => x == f32::INFINITY,
398            Constant::F64(x) => x == f64::INFINITY,
399            _ => false,
400        }
401    }
402
403    pub fn is_neg_infinity(&self) -> bool {
404        match *self {
405            // FIXME(f16_f128): add f16 and f128 when constants are available
406            Constant::F32(x) => x == f32::NEG_INFINITY,
407            Constant::F64(x) => x == f64::NEG_INFINITY,
408            _ => false,
409        }
410    }
411}
412
413/// Parses a `LitKind` to a `Constant`.
414pub fn lit_to_mir_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
415    match *lit {
416        LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
417        LitKind::Byte(b) => Constant::Int(u128::from(b)),
418        LitKind::ByteStr(ref s, _) | LitKind::CStr(ref s, _) => Constant::Binary(s.as_byte_str().to_vec()),
419        LitKind::Char(c) => Constant::Char(c),
420        LitKind::Int(n, _) => Constant::Int(n.get()),
421        LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
422            // FIXME(f16_f128): just use `parse()` directly when available for `f16`/`f128`
423            FloatTy::F16 => Constant::parse_f16(is.as_str()),
424            FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
425            FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
426            FloatTy::F128 => Constant::parse_f128(is.as_str()),
427        },
428        LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() {
429            ty::Float(FloatTy::F16) => Constant::parse_f16(is.as_str()),
430            ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
431            ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
432            ty::Float(FloatTy::F128) => Constant::parse_f128(is.as_str()),
433            _ => bug!(),
434        },
435        LitKind::Bool(b) => Constant::Bool(b),
436        LitKind::Err(_) => Constant::Err,
437    }
438}
439
440/// The source of a constant value.
441#[derive(Clone, Copy)]
442pub enum ConstantSource {
443    /// The value is determined solely from the expression.
444    Local,
445    /// The value is dependent on another definition that may change independently from the local
446    /// expression.
447    NonLocal,
448}
449impl ConstantSource {
450    pub fn is_local(self) -> bool {
451        matches!(self, Self::Local)
452    }
453}
454
455#[derive(Copy, Clone, Debug, Eq)]
456pub enum FullInt {
457    S(i128),
458    U(u128),
459}
460
461impl PartialEq for FullInt {
462    fn eq(&self, other: &Self) -> bool {
463        self.cmp(other) == Ordering::Equal
464    }
465}
466
467impl PartialOrd for FullInt {
468    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
469        Some(self.cmp(other))
470    }
471}
472
473impl Ord for FullInt {
474    fn cmp(&self, other: &Self) -> Ordering {
475        use FullInt::{S, U};
476
477        fn cmp_s_u(s: i128, u: u128) -> Ordering {
478            u128::try_from(s).map_or(Ordering::Less, |x| x.cmp(&u))
479        }
480
481        match (*self, *other) {
482            (S(s), S(o)) => s.cmp(&o),
483            (U(s), U(o)) => s.cmp(&o),
484            (S(s), U(o)) => cmp_s_u(s, o),
485            (U(s), S(o)) => cmp_s_u(o, s).reverse(),
486        }
487    }
488}
489
490/// The context required to evaluate a constant expression.
491///
492/// This is currently limited to constant folding and reading the value of named constants.
493///
494/// See the module level documentation for some context.
495pub struct ConstEvalCtxt<'tcx> {
496    tcx: TyCtxt<'tcx>,
497    typing_env: ty::TypingEnv<'tcx>,
498    typeck: &'tcx TypeckResults<'tcx>,
499    source: Cell<ConstantSource>,
500    ctxt: Cell<SyntaxContext>,
501}
502
503impl<'tcx> ConstEvalCtxt<'tcx> {
504    /// Creates the evaluation context from the lint context. This requires the lint context to be
505    /// in a body (i.e. `cx.enclosing_body.is_some()`).
506    pub fn new(cx: &LateContext<'tcx>) -> Self {
507        Self {
508            tcx: cx.tcx,
509            typing_env: cx.typing_env(),
510            typeck: cx.typeck_results(),
511            source: Cell::new(ConstantSource::Local),
512            ctxt: Cell::new(SyntaxContext::root()),
513        }
514    }
515
516    /// Creates an evaluation context.
517    pub fn with_env(tcx: TyCtxt<'tcx>, typing_env: ty::TypingEnv<'tcx>, typeck: &'tcx TypeckResults<'tcx>) -> Self {
518        Self {
519            tcx,
520            typing_env,
521            typeck,
522            source: Cell::new(ConstantSource::Local),
523            ctxt: Cell::new(SyntaxContext::root()),
524        }
525    }
526
527    /// Attempts to evaluate the expression and returns both the value and whether it's dependant on
528    /// other items.
529    pub fn eval_with_source(&self, e: &Expr<'_>, ctxt: SyntaxContext) -> Option<(Constant, ConstantSource)> {
530        self.source.set(ConstantSource::Local);
531        self.ctxt.set(ctxt);
532        self.expr(e).map(|c| (c, self.source.get()))
533    }
534
535    /// Attempts to evaluate the expression.
536    pub fn eval(&self, e: &Expr<'_>) -> Option<Constant> {
537        self.expr(e)
538    }
539
540    /// Attempts to evaluate the expression without accessing other items.
541    ///
542    /// The context argument is the context used to view the evaluated expression. e.g. when
543    /// evaluating the argument in `f(m!(1))` the context of the call expression should be used.
544    /// This is need so the const evaluator can see the `m` macro and marke the evaluation as
545    /// non-local independant of what the macro expands to.
546    pub fn eval_local(&self, e: &Expr<'_>, ctxt: SyntaxContext) -> Option<Constant> {
547        match self.eval_with_source(e, ctxt) {
548            Some((x, ConstantSource::Local)) => Some(x),
549            _ => None,
550        }
551    }
552
553    /// Attempts to evaluate the expression as an integer without accessing other items.
554    ///
555    /// The context argument is the context used to view the evaluated expression. e.g. when
556    /// evaluating the argument in `f(m!(1))` the context of the call expression should be used.
557    /// This is need so the const evaluator can see the `m` macro and marke the evaluation as
558    /// non-local independant of what the macro expands to.
559    pub fn eval_full_int(&self, e: &Expr<'_>, ctxt: SyntaxContext) -> Option<FullInt> {
560        match self.eval_with_source(e, ctxt) {
561            Some((x, ConstantSource::Local)) => x.int_value(self.tcx, self.typeck.expr_ty(e)),
562            _ => None,
563        }
564    }
565
566    pub fn eval_pat_expr(&self, pat_expr: &PatExpr<'_>) -> Option<Constant> {
567        match &pat_expr.kind {
568            PatExprKind::Lit { lit, negated } => {
569                let ty = self.typeck.node_type_opt(pat_expr.hir_id);
570                let val = lit_to_mir_constant(&lit.node, ty);
571                if *negated {
572                    self.constant_negate(&val, ty?)
573                } else {
574                    Some(val)
575                }
576            },
577            PatExprKind::ConstBlock(ConstBlock { body, .. }) => self.expr(self.tcx.hir_body(*body).value),
578            PatExprKind::Path(qpath) => self.qpath(qpath, pat_expr.hir_id),
579        }
580    }
581
582    fn check_ctxt(&self, ctxt: SyntaxContext) {
583        if self.ctxt.get() != ctxt {
584            self.source.set(ConstantSource::NonLocal);
585        }
586    }
587
588    fn qpath(&self, qpath: &QPath<'_>, hir_id: HirId) -> Option<Constant> {
589        self.fetch_path(qpath, hir_id)
590            .and_then(|c| mir_to_const(self.tcx, c, self.typeck.node_type(hir_id)))
591    }
592
593    /// Simple constant folding: Insert an expression, get a constant or none.
594    fn expr(&self, e: &Expr<'_>) -> Option<Constant> {
595        self.check_ctxt(e.span.ctxt());
596        match e.kind {
597            ExprKind::ConstBlock(ConstBlock { body, .. }) => self.expr(self.tcx.hir_body(body).value),
598            ExprKind::DropTemps(e) => self.expr(e),
599            ExprKind::Path(ref qpath) => self.qpath(qpath, e.hir_id),
600            ExprKind::Block(block, _) => {
601                self.check_ctxt(block.span.ctxt());
602                self.block(block)
603            },
604            ExprKind::Lit(lit) => {
605                self.check_ctxt(lit.span.ctxt());
606                Some(lit_to_mir_constant(&lit.node, self.typeck.expr_ty_opt(e)))
607            },
608            ExprKind::Array(vec) => self.multi(vec).map(Constant::Vec),
609            ExprKind::Tup(tup) => self.multi(tup).map(Constant::Tuple),
610            ExprKind::Repeat(value, _) => {
611                let n = match self.typeck.expr_ty(e).kind() {
612                    ty::Array(_, n) => n.try_to_target_usize(self.tcx)?,
613                    _ => span_bug!(e.span, "typeck error"),
614                };
615                self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
616            },
617            ExprKind::Unary(op, operand) => self.expr(operand).and_then(|o| match op {
618                UnOp::Not => self.constant_not(&o, self.typeck.expr_ty(e)),
619                UnOp::Neg => self.constant_negate(&o, self.typeck.expr_ty(e)),
620                UnOp::Deref => Some(if let Constant::Ref(r) = o { *r } else { o }),
621            }),
622            ExprKind::If(cond, then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
623            ExprKind::Binary(op, left, right) => {
624                self.check_ctxt(e.span.ctxt());
625                self.binop(op.node, left, right)
626            },
627            ExprKind::Call(callee, []) => {
628                // We only handle a few const functions for now.
629                if let ExprKind::Path(qpath) = &callee.kind
630                    && let Some(did) = self.typeck.qpath_res(qpath, callee.hir_id).opt_def_id()
631                {
632                    match self.tcx.get_diagnostic_name(did) {
633                        Some(sym::i8_legacy_fn_max_value) => Some(Constant::Int(i8::MAX as u128)),
634                        Some(sym::i16_legacy_fn_max_value) => Some(Constant::Int(i16::MAX as u128)),
635                        Some(sym::i32_legacy_fn_max_value) => Some(Constant::Int(i32::MAX as u128)),
636                        Some(sym::i64_legacy_fn_max_value) => Some(Constant::Int(i64::MAX as u128)),
637                        Some(sym::i128_legacy_fn_max_value) => Some(Constant::Int(i128::MAX as u128)),
638                        _ => None,
639                    }
640                } else {
641                    None
642                }
643            },
644            ExprKind::Index(arr, index, _) => self.index(arr, index),
645            ExprKind::AddrOf(_, _, inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
646            ExprKind::Field(base, ref field)
647                if let base_ty = self.typeck.expr_ty(base)
648                    && match self.typeck.expr_adjustments(base) {
649                        [] => true,
650                        [.., a] => a.target == base_ty,
651                    }
652                    && let Some(Constant::Adt(constant)) = self.expr(base)
653                    && let ty::Adt(adt_def, _) = *base_ty.kind()
654                    && adt_def.is_struct()
655                    && let Some((desired_field, ty)) =
656                        field_of_struct(adt_def, self.tcx, constant, base_ty, field.name) =>
657            {
658                self.check_ctxt(field.span.ctxt());
659                mir_to_const(self.tcx, desired_field, ty)
660            },
661            _ => None,
662        }
663    }
664
665    /// Simple constant folding to determine if an expression is an empty slice, str, array, …
666    /// `None` will be returned if the constness cannot be determined, or if the resolution
667    /// leaves the local crate.
668    pub fn eval_is_empty(&self, e: &Expr<'_>) -> Option<bool> {
669        match e.kind {
670            ExprKind::ConstBlock(ConstBlock { body, .. }) => self.eval_is_empty(self.tcx.hir_body(body).value),
671            ExprKind::DropTemps(e) => self.eval_is_empty(e),
672            ExprKind::Lit(lit) => {
673                if is_direct_expn_of(e.span, sym::cfg).is_some() {
674                    None
675                } else {
676                    match &lit.node {
677                        LitKind::Str(is, _) => Some(is.is_empty()),
678                        LitKind::ByteStr(s, _) | LitKind::CStr(s, _) => Some(s.as_byte_str().is_empty()),
679                        _ => None,
680                    }
681                }
682            },
683            ExprKind::Array(vec) => self.multi(vec).map(|v| v.is_empty()),
684            ExprKind::Repeat(..) => {
685                if let ty::Array(_, n) = self.typeck.expr_ty(e).kind() {
686                    Some(n.try_to_target_usize(self.tcx)? == 0)
687                } else {
688                    span_bug!(e.span, "typeck error");
689                }
690            },
691            _ => None,
692        }
693    }
694
695    #[expect(clippy::cast_possible_wrap)]
696    fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
697        use self::Constant::{Bool, Int};
698        match *o {
699            Bool(b) => Some(Bool(!b)),
700            Int(value) => {
701                let value = !value;
702                match *ty.kind() {
703                    ty::Int(ity) => Some(Int(unsext(self.tcx, value as i128, ity))),
704                    ty::Uint(ity) => Some(Int(clip(self.tcx, value, ity))),
705                    _ => None,
706                }
707            },
708            _ => None,
709        }
710    }
711
712    fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
713        use self::Constant::{F32, F64, Int};
714        match *o {
715            Int(value) => {
716                let ty::Int(ity) = *ty.kind() else { return None };
717                let (min, _) = ity.min_max()?;
718                // sign extend
719                let value = sext(self.tcx, value, ity);
720
721                // Applying unary - to the most negative value of any signed integer type panics.
722                if value == min {
723                    return None;
724                }
725
726                let value = value.checked_neg()?;
727                // clear unused bits
728                Some(Int(unsext(self.tcx, value, ity)))
729            },
730            F32(f) => Some(F32(-f)),
731            F64(f) => Some(F64(-f)),
732            _ => None,
733        }
734    }
735
736    /// Create `Some(Vec![..])` of all constants, unless there is any
737    /// non-constant part.
738    fn multi(&self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
739        vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
740    }
741
742    /// Lookup a possibly constant expression from an `ExprKind::Path` and apply a function on it.
743    #[expect(clippy::too_many_lines)]
744    fn fetch_path(&self, qpath: &QPath<'_>, id: HirId) -> Option<ConstValue> {
745        // Resolve the path to a constant and check if that constant is known to
746        // not change based on the target.
747        //
748        // This should be replaced with an attribute at some point.
749        let did = match *qpath {
750            QPath::Resolved(None, path)
751                if path.span.ctxt() == self.ctxt.get()
752                    && path.segments.iter().all(|s| self.ctxt.get() == s.ident.span.ctxt())
753                    && let Res::Def(DefKind::Const, did) = path.res
754                    && (matches!(
755                        self.tcx.get_diagnostic_name(did),
756                        Some(
757                            sym::f32_legacy_const_digits
758                                | sym::f32_legacy_const_epsilon
759                                | sym::f32_legacy_const_infinity
760                                | sym::f32_legacy_const_mantissa_dig
761                                | sym::f32_legacy_const_max
762                                | sym::f32_legacy_const_max_10_exp
763                                | sym::f32_legacy_const_max_exp
764                                | sym::f32_legacy_const_min
765                                | sym::f32_legacy_const_min_10_exp
766                                | sym::f32_legacy_const_min_exp
767                                | sym::f32_legacy_const_min_positive
768                                | sym::f32_legacy_const_nan
769                                | sym::f32_legacy_const_neg_infinity
770                                | sym::f32_legacy_const_radix
771                                | sym::f64_legacy_const_digits
772                                | sym::f64_legacy_const_epsilon
773                                | sym::f64_legacy_const_infinity
774                                | sym::f64_legacy_const_mantissa_dig
775                                | sym::f64_legacy_const_max
776                                | sym::f64_legacy_const_max_10_exp
777                                | sym::f64_legacy_const_max_exp
778                                | sym::f64_legacy_const_min
779                                | sym::f64_legacy_const_min_10_exp
780                                | sym::f64_legacy_const_min_exp
781                                | sym::f64_legacy_const_min_positive
782                                | sym::f64_legacy_const_nan
783                                | sym::f64_legacy_const_neg_infinity
784                                | sym::f64_legacy_const_radix
785                                | sym::u8_legacy_const_min
786                                | sym::u16_legacy_const_min
787                                | sym::u32_legacy_const_min
788                                | sym::u64_legacy_const_min
789                                | sym::u128_legacy_const_min
790                                | sym::usize_legacy_const_min
791                                | sym::u8_legacy_const_max
792                                | sym::u16_legacy_const_max
793                                | sym::u32_legacy_const_max
794                                | sym::u64_legacy_const_max
795                                | sym::u128_legacy_const_max
796                                | sym::i8_legacy_const_min
797                                | sym::i16_legacy_const_min
798                                | sym::i32_legacy_const_min
799                                | sym::i64_legacy_const_min
800                                | sym::i128_legacy_const_min
801                                | sym::i8_legacy_const_max
802                                | sym::i16_legacy_const_max
803                                | sym::i32_legacy_const_max
804                                | sym::i64_legacy_const_max
805                                | sym::i128_legacy_const_max
806                        )
807                    ) || self.tcx.opt_parent(did).is_some_and(|parent| {
808                        paths::F16_CONSTS.matches(&self.tcx, parent)
809                            || paths::F32_CONSTS.matches(&self.tcx, parent)
810                            || paths::F64_CONSTS.matches(&self.tcx, parent)
811                            || paths::F128_CONSTS.matches(&self.tcx, parent)
812                    })) =>
813            {
814                did
815            },
816            QPath::TypeRelative(ty, const_name)
817                if let TyKind::Path(QPath::Resolved(None, ty_path)) = ty.kind
818                    && let [.., ty_name] = ty_path.segments
819                    && (matches!(
820                        ty_name.ident.name,
821                        sym::i8
822                            | sym::i16
823                            | sym::i32
824                            | sym::i64
825                            | sym::i128
826                            | sym::u8
827                            | sym::u16
828                            | sym::u32
829                            | sym::u64
830                            | sym::u128
831                            | sym::f32
832                            | sym::f64
833                            | sym::char
834                    ) || (ty_name.ident.name == sym::usize && const_name.ident.name == sym::MIN))
835                    && const_name.ident.span.ctxt() == self.ctxt.get()
836                    && ty.span.ctxt() == self.ctxt.get()
837                    && ty_name.ident.span.ctxt() == self.ctxt.get()
838                    && matches!(ty_path.res, Res::PrimTy(_))
839                    && let Some((DefKind::AssocConst, did)) = self.typeck.type_dependent_def(id) =>
840            {
841                did
842            },
843            _ if let Res::Def(DefKind::Const | DefKind::AssocConst, did) = self.typeck.qpath_res(qpath, id) => {
844                self.source.set(ConstantSource::NonLocal);
845                did
846            },
847            _ => return None,
848        };
849
850        self.tcx
851            .const_eval_resolve(
852                self.typing_env,
853                mir::UnevaluatedConst::new(did, self.typeck.node_args(id)),
854                qpath.span(),
855            )
856            .ok()
857    }
858
859    fn index(&self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
860        let lhs = self.expr(lhs);
861        let index = self.expr(index);
862
863        match (lhs, index) {
864            (Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec.get(index as usize) {
865                Some(Constant::F16(x)) => Some(Constant::F16(*x)),
866                Some(Constant::F32(x)) => Some(Constant::F32(*x)),
867                Some(Constant::F64(x)) => Some(Constant::F64(*x)),
868                Some(Constant::F128(x)) => Some(Constant::F128(*x)),
869                _ => None,
870            },
871            (Some(Constant::Vec(vec)), _) => {
872                if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
873                    match vec.first() {
874                        Some(Constant::F16(x)) => Some(Constant::F16(*x)),
875                        Some(Constant::F32(x)) => Some(Constant::F32(*x)),
876                        Some(Constant::F64(x)) => Some(Constant::F64(*x)),
877                        Some(Constant::F128(x)) => Some(Constant::F128(*x)),
878                        _ => None,
879                    }
880                } else {
881                    None
882                }
883            },
884            _ => None,
885        }
886    }
887
888    /// A block can only yield a constant if it has exactly one constant expression.
889    fn block(&self, block: &Block<'_>) -> Option<Constant> {
890        if block.stmts.is_empty()
891            && let Some(expr) = block.expr
892        {
893            // Try to detect any `cfg`ed statements or empty macro expansions.
894            let span = block.span.data();
895            if span.ctxt == SyntaxContext::root() {
896                if let Some(expr_span) = walk_span_to_context(expr.span, span.ctxt)
897                    && let expr_lo = expr_span.lo()
898                    && expr_lo >= span.lo
899                    && let Some(src) = (span.lo..expr_lo).get_source_range(&self.tcx)
900                    && let Some(src) = src.as_str()
901                {
902                    use rustc_lexer::TokenKind::{BlockComment, LineComment, OpenBrace, Semi, Whitespace};
903                    if !tokenize(src, FrontmatterAllowed::No)
904                        .map(|t| t.kind)
905                        .filter(|t| !matches!(t, Whitespace | LineComment { .. } | BlockComment { .. } | Semi))
906                        .eq([OpenBrace])
907                    {
908                        self.source.set(ConstantSource::NonLocal);
909                    }
910                } else {
911                    // Unable to access the source. Assume a non-local dependency.
912                    self.source.set(ConstantSource::NonLocal);
913                }
914            }
915
916            self.expr(expr)
917        } else {
918            None
919        }
920    }
921
922    fn ifthenelse(&self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
923        if let Some(Constant::Bool(b)) = self.expr(cond) {
924            if b {
925                self.expr(then)
926            } else {
927                otherwise.as_ref().and_then(|expr| self.expr(expr))
928            }
929        } else {
930            None
931        }
932    }
933
934    fn binop(&self, op: BinOpKind, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
935        let l = self.expr(left)?;
936        let r = self.expr(right);
937        match (l, r) {
938            (Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck.expr_ty_opt(left)?.kind() {
939                ty::Int(ity) => {
940                    let (ty_min_value, _) = ity.min_max()?;
941                    let bits = ity.bits();
942                    let l = sext(self.tcx, l, ity);
943                    let r = sext(self.tcx, r, ity);
944
945                    // Using / or %, where the left-hand argument is the smallest integer of a signed integer type and
946                    // the right-hand argument is -1 always panics, even with overflow-checks disabled
947                    if let BinOpKind::Div | BinOpKind::Rem = op
948                        && l == ty_min_value
949                        && r == -1
950                    {
951                        return None;
952                    }
953
954                    let zext = |n: i128| Constant::Int(unsext(self.tcx, n, ity));
955                    match op {
956                        // When +, * or binary - create a value greater than the maximum value, or less than
957                        // the minimum value that can be stored, it panics.
958                        BinOpKind::Add => l.checked_add(r).and_then(|n| ity.ensure_fits(n)).map(zext),
959                        BinOpKind::Sub => l.checked_sub(r).and_then(|n| ity.ensure_fits(n)).map(zext),
960                        BinOpKind::Mul => l.checked_mul(r).and_then(|n| ity.ensure_fits(n)).map(zext),
961                        BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
962                        BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
963                        // Using << or >> where the right-hand argument is greater than or equal to the number of bits
964                        // in the type of the left-hand argument, or is negative panics.
965                        BinOpKind::Shr if r < bits && !r.is_negative() => l.checked_shr(r.try_into().ok()?).map(zext),
966                        BinOpKind::Shl if r < bits && !r.is_negative() => l.checked_shl(r.try_into().ok()?).map(zext),
967                        BinOpKind::BitXor => Some(zext(l ^ r)),
968                        BinOpKind::BitOr => Some(zext(l | r)),
969                        BinOpKind::BitAnd => Some(zext(l & r)),
970                        // FIXME: f32/f64 currently consider `0.0` and `-0.0` as different.
971                        BinOpKind::Eq => Some(Constant::Bool(l == r)),
972                        BinOpKind::Ne => Some(Constant::Bool(l != r)),
973                        BinOpKind::Lt => Some(Constant::Bool(l < r)),
974                        BinOpKind::Le => Some(Constant::Bool(l <= r)),
975                        BinOpKind::Ge => Some(Constant::Bool(l >= r)),
976                        BinOpKind::Gt => Some(Constant::Bool(l > r)),
977                        _ => None,
978                    }
979                },
980                ty::Uint(ity) => {
981                    let bits = ity.bits();
982
983                    match op {
984                        BinOpKind::Add => l.checked_add(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
985                        BinOpKind::Sub => l.checked_sub(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
986                        BinOpKind::Mul => l.checked_mul(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
987                        BinOpKind::Div => l.checked_div(r).map(Constant::Int),
988                        BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
989                        BinOpKind::Shr if r < bits => l.checked_shr(r.try_into().ok()?).map(Constant::Int),
990                        BinOpKind::Shl if r < bits => l.checked_shl(r.try_into().ok()?).map(Constant::Int),
991                        BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
992                        BinOpKind::BitOr => Some(Constant::Int(l | r)),
993                        BinOpKind::BitAnd => Some(Constant::Int(l & r)),
994                        BinOpKind::Eq => Some(Constant::Bool(l == r)),
995                        BinOpKind::Ne => Some(Constant::Bool(l != r)),
996                        BinOpKind::Lt => Some(Constant::Bool(l < r)),
997                        BinOpKind::Le => Some(Constant::Bool(l <= r)),
998                        BinOpKind::Ge => Some(Constant::Bool(l >= r)),
999                        BinOpKind::Gt => Some(Constant::Bool(l > r)),
1000                        _ => None,
1001                    }
1002                },
1003                _ => None,
1004            },
1005            // FIXME(f16_f128): add these types when binary operations are available on all platforms
1006            (Constant::F32(l), Some(Constant::F32(r))) => match op {
1007                BinOpKind::Add => Some(Constant::F32(l + r)),
1008                BinOpKind::Sub => Some(Constant::F32(l - r)),
1009                BinOpKind::Mul => Some(Constant::F32(l * r)),
1010                BinOpKind::Div => Some(Constant::F32(l / r)),
1011                BinOpKind::Rem => Some(Constant::F32(l % r)),
1012                BinOpKind::Eq => Some(Constant::Bool(l == r)),
1013                BinOpKind::Ne => Some(Constant::Bool(l != r)),
1014                BinOpKind::Lt => Some(Constant::Bool(l < r)),
1015                BinOpKind::Le => Some(Constant::Bool(l <= r)),
1016                BinOpKind::Ge => Some(Constant::Bool(l >= r)),
1017                BinOpKind::Gt => Some(Constant::Bool(l > r)),
1018                _ => None,
1019            },
1020            (Constant::F64(l), Some(Constant::F64(r))) => match op {
1021                BinOpKind::Add => Some(Constant::F64(l + r)),
1022                BinOpKind::Sub => Some(Constant::F64(l - r)),
1023                BinOpKind::Mul => Some(Constant::F64(l * r)),
1024                BinOpKind::Div => Some(Constant::F64(l / r)),
1025                BinOpKind::Rem => Some(Constant::F64(l % r)),
1026                BinOpKind::Eq => Some(Constant::Bool(l == r)),
1027                BinOpKind::Ne => Some(Constant::Bool(l != r)),
1028                BinOpKind::Lt => Some(Constant::Bool(l < r)),
1029                BinOpKind::Le => Some(Constant::Bool(l <= r)),
1030                BinOpKind::Ge => Some(Constant::Bool(l >= r)),
1031                BinOpKind::Gt => Some(Constant::Bool(l > r)),
1032                _ => None,
1033            },
1034            (l, r) => match (op, l, r) {
1035                (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
1036                (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
1037                (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
1038                    Some(r)
1039                },
1040                (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
1041                (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
1042                (BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
1043                _ => None,
1044            },
1045        }
1046    }
1047}
1048
1049pub fn mir_to_const<'tcx>(tcx: TyCtxt<'tcx>, val: ConstValue, ty: Ty<'tcx>) -> Option<Constant> {
1050    match (val, ty.kind()) {
1051        (_, &ty::Adt(adt_def, _)) if adt_def.is_struct() => Some(Constant::Adt(val)),
1052        (ConstValue::Scalar(Scalar::Int(int)), _) => match ty.kind() {
1053            ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
1054            ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.to_bits(int.size()))),
1055            ty::Float(FloatTy::F16) => Some(Constant::F16(int.into())),
1056            ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(int.into()))),
1057            ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(int.into()))),
1058            ty::Float(FloatTy::F128) => Some(Constant::F128(int.into())),
1059            ty::RawPtr(_, _) => Some(Constant::RawPtr(int.to_bits(int.size()))),
1060            _ => None,
1061        },
1062        (_, ty::Ref(_, inner_ty, _)) if matches!(inner_ty.kind(), ty::Str) => {
1063            let data = val.try_get_slice_bytes_for_diagnostics(tcx)?;
1064            String::from_utf8(data.to_owned()).ok().map(Constant::Str)
1065        },
1066        (ConstValue::Indirect { alloc_id, offset }, ty::Array(sub_type, len)) => {
1067            let alloc = tcx.global_alloc(alloc_id).unwrap_memory().inner();
1068            let len = len.try_to_target_usize(tcx)?;
1069            let ty::Float(flt) = sub_type.kind() else {
1070                return None;
1071            };
1072            let size = Size::from_bits(flt.bit_width());
1073            let mut res = Vec::new();
1074            for idx in 0..len {
1075                let range = alloc_range(offset + size * idx, size);
1076                let val = alloc.read_scalar(&tcx, range, /* read_provenance */ false).ok()?;
1077                res.push(match flt {
1078                    FloatTy::F16 => Constant::F16(val.to_u16().discard_err()?),
1079                    FloatTy::F32 => Constant::F32(f32::from_bits(val.to_u32().discard_err()?)),
1080                    FloatTy::F64 => Constant::F64(f64::from_bits(val.to_u64().discard_err()?)),
1081                    FloatTy::F128 => Constant::F128(val.to_u128().discard_err()?),
1082                });
1083            }
1084            Some(Constant::Vec(res))
1085        },
1086        _ => None,
1087    }
1088}
1089
1090fn field_of_struct<'tcx>(
1091    adt_def: ty::AdtDef<'tcx>,
1092    tcx: TyCtxt<'tcx>,
1093    value: ConstValue,
1094    ty: Ty<'tcx>,
1095    field: Symbol,
1096) -> Option<(ConstValue, Ty<'tcx>)> {
1097    if let Some(dc) = tcx.try_destructure_mir_constant_for_user_output(value, ty)
1098        && let Some(dc_variant) = dc.variant
1099        && let Some(variant) = adt_def.variants().get(dc_variant)
1100        && let Some(field_idx) = variant.fields.iter().position(|el| el.name == field)
1101    {
1102        dc.fields.get(field_idx).copied()
1103    } else {
1104        None
1105    }
1106}
1107
1108/// If `expr` evaluates to an integer constant, return its value.
1109///
1110/// The context argument is the context used to view the evaluated expression. e.g. when evaluating
1111/// the argument in `f(m!(1))` the context of the call expression should be used. This is need so
1112/// the const evaluator can see the `m` macro and marke the evaluation as non-local independant of
1113/// what the macro expands to.
1114pub fn integer_const(cx: &LateContext<'_>, expr: &Expr<'_>, ctxt: SyntaxContext) -> Option<u128> {
1115    if let Some(Constant::Int(value)) = ConstEvalCtxt::new(cx).eval_local(expr, ctxt) {
1116        Some(value)
1117    } else {
1118        None
1119    }
1120}
1121
1122/// Check if `expr` evaluates to an integer constant of 0.
1123///
1124/// The context argument is the context used to view the evaluated expression. e.g. when evaluating
1125/// the argument in `f(m!(1))` the context of the call expression should be used. This is need so
1126/// the const evaluator can see the `m` macro and marke the evaluation as non-local independant of
1127/// what the macro expands to.
1128#[inline]
1129pub fn is_zero_integer_const(cx: &LateContext<'_>, expr: &Expr<'_>, ctxt: SyntaxContext) -> bool {
1130    integer_const(cx, expr, ctxt) == Some(0)
1131}
clippy_utils/consts.rs

clippy_utils/
consts.rs
