src/tools/clippy/clippy_utils/src/consts.rs

   1 #![allow(clippy::float_cmp)]
   2
   3 use crate::{clip, is_direct_expn_of, sext, unsext};
   4 use if_chain::if_chain;
   5 use rustc_ast::ast::{self, LitFloatType, LitKind};
   6 use rustc_data_structures::sync::Lrc;
   7 use rustc_hir::def::{DefKind, Res};
   8 use rustc_hir::{BinOp, BinOpKind, Block, Expr, ExprKind, HirId, Item, ItemKind, Node, QPath, UnOp};
   9 use rustc_lint::LateContext;
  10 use rustc_middle::mir;
  11 use rustc_middle::mir::interpret::Scalar;
  12 use rustc_middle::ty::SubstsRef;
  13 use rustc_middle::ty::{self, EarlyBinder, FloatTy, ScalarInt, Ty, TyCtxt};
  14 use rustc_middle::{bug, span_bug};
  15 use rustc_span::symbol::Symbol;
  16 use std::cmp::Ordering::{self, Equal};
  17 use std::hash::{Hash, Hasher};
  18 use std::iter;
  19
  20 /// A `LitKind`-like enum to fold constant `Expr`s into.
  21 #[derive(Debug, Clone)]
  22 pub enum Constant {
  23     /// A `String` (e.g., "abc").
  24     Str(String),
  25     /// A binary string (e.g., `b"abc"`).
  26     Binary(Lrc<[u8]>),
  27     /// A single `char` (e.g., `'a'`).
  28     Char(char),
  29     /// An integer's bit representation.
  30     Int(u128),
  31     /// An `f32`.
  32     F32(f32),
  33     /// An `f64`.
  34     F64(f64),
  35     /// `true` or `false`.
  36     Bool(bool),
  37     /// An array of constants.
  38     Vec(Vec<Constant>),
  39     /// Also an array, but with only one constant, repeated N times.
  40     Repeat(Box<Constant>, u64),
  41     /// A tuple of constants.
  42     Tuple(Vec<Constant>),
  43     /// A raw pointer.
  44     RawPtr(u128),
  45     /// A reference
  46     Ref(Box<Constant>),
  47     /// A literal with syntax error.
  48     Err,
  49 }
  50
  51 impl PartialEq for Constant {
  52     fn eq(&self, other: &Self) -> bool {
  53         match (self, other) {
  54             (Self::Str(ls), Self::Str(rs)) => ls == rs,
  55             (Self::Binary(l), Self::Binary(r)) => l == r,
  56             (&Self::Char(l), &Self::Char(r)) => l == r,
  57             (&Self::Int(l), &Self::Int(r)) => l == r,
  58             (&Self::F64(l), &Self::F64(r)) => {
  59                 // We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have
  60                 // `Fw32 == Fw64`, so don’t compare them.
  61                 // `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs.
  62                 l.to_bits() == r.to_bits()
  63             },
  64             (&Self::F32(l), &Self::F32(r)) => {
  65                 // We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have
  66                 // `Fw32 == Fw64`, so don’t compare them.
  67                 // `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs.
  68                 f64::from(l).to_bits() == f64::from(r).to_bits()
  69             },
  70             (&Self::Bool(l), &Self::Bool(r)) => l == r,
  71             (&Self::Vec(ref l), &Self::Vec(ref r)) | (&Self::Tuple(ref l), &Self::Tuple(ref r)) => l == r,
  72             (Self::Repeat(lv, ls), Self::Repeat(rv, rs)) => ls == rs && lv == rv,
  73             (Self::Ref(lb), Self::Ref(rb)) => *lb == *rb,
  74             // TODO: are there inter-type equalities?
  75             _ => false,
  76         }
  77     }
  78 }
  79
  80 impl Hash for Constant {
  81     fn hash<H>(&self, state: &mut H)
  82     where
  83         H: Hasher,
  84     {
  85         std::mem::discriminant(self).hash(state);
  86         match *self {
  87             Self::Str(ref s) => {
  88                 s.hash(state);
  89             },
  90             Self::Binary(ref b) => {
  91                 b.hash(state);
  92             },
  93             Self::Char(c) => {
  94                 c.hash(state);
  95             },
  96             Self::Int(i) => {
  97                 i.hash(state);
  98             },
  99             Self::F32(f) => {
 100                 f64::from(f).to_bits().hash(state);
 101             },
 102             Self::F64(f) => {
 103                 f.to_bits().hash(state);
 104             },
 105             Self::Bool(b) => {
 106                 b.hash(state);
 107             },
 108             Self::Vec(ref v) | Self::Tuple(ref v) => {
 109                 v.hash(state);
 110             },
 111             Self::Repeat(ref c, l) => {
 112                 c.hash(state);
 113                 l.hash(state);
 114             },
 115             Self::RawPtr(u) => {
 116                 u.hash(state);
 117             },
 118             Self::Ref(ref r) => {
 119                 r.hash(state);
 120             },
 121             Self::Err => {},
 122         }
 123     }
 124 }
 125
 126 impl Constant {
 127     pub fn partial_cmp(tcx: TyCtxt<'_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option<Ordering> {
 128         match (left, right) {
 129             (Self::Str(ls), Self::Str(rs)) => Some(ls.cmp(rs)),
 130             (Self::Char(l), Self::Char(r)) => Some(l.cmp(r)),
 131             (&Self::Int(l), &Self::Int(r)) => match *cmp_type.kind() {
 132                 ty::Int(int_ty) => Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty))),
 133                 ty::Uint(_) => Some(l.cmp(&r)),
 134                 _ => bug!("Not an int type"),
 135             },
 136             (&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r),
 137             (&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r),
 138             (Self::Bool(l), Self::Bool(r)) => Some(l.cmp(r)),
 139             (Self::Tuple(l), Self::Tuple(r)) if l.len() == r.len() => match *cmp_type.kind() {
 140                 ty::Tuple(tys) if tys.len() == l.len() => l
 141                     .iter()
 142                     .zip(r)
 143                     .zip(tys)
 144                     .map(|((li, ri), cmp_type)| Self::partial_cmp(tcx, cmp_type, li, ri))
 145                     .find(|r| r.map_or(true, |o| o != Ordering::Equal))
 146                     .unwrap_or_else(|| Some(l.len().cmp(&r.len()))),
 147                 _ => None,
 148             },
 149             (Self::Vec(l), Self::Vec(r)) => {
 150                 let (ty::Array(cmp_type, _) | ty::Slice(cmp_type)) = *cmp_type.kind() else {
 151                     return None
 152                 };
 153                 iter::zip(l, r)
 154                     .map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri))
 155                     .find(|r| r.map_or(true, |o| o != Ordering::Equal))
 156                     .unwrap_or_else(|| Some(l.len().cmp(&r.len())))
 157             },
 158             (Self::Repeat(lv, ls), Self::Repeat(rv, rs)) => {
 159                 match Self::partial_cmp(
 160                     tcx,
 161                     match *cmp_type.kind() {
 162                         ty::Array(ty, _) => ty,
 163                         _ => return None,
 164                     },
 165                     lv,
 166                     rv,
 167                 ) {
 168                     Some(Equal) => Some(ls.cmp(rs)),
 169                     x => x,
 170                 }
 171             },
 172             (Self::Ref(lb), Self::Ref(rb)) => Self::partial_cmp(
 173                 tcx,
 174                 match *cmp_type.kind() {
 175                     ty::Ref(_, ty, _) => ty,
 176                     _ => return None,
 177                 },
 178                 lb,
 179                 rb,
 180             ),
 181             // TODO: are there any useful inter-type orderings?
 182             _ => None,
 183         }
 184     }
 185
 186     /// Returns the integer value or `None` if `self` or `val_type` is not integer type.
 187     pub fn int_value(&self, cx: &LateContext<'_>, val_type: Ty<'_>) -> Option<FullInt> {
 188         if let Constant::Int(const_int) = *self {
 189             match *val_type.kind() {
 190                 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
 191                 ty::Uint(_) => Some(FullInt::U(const_int)),
 192                 _ => None,
 193             }
 194         } else {
 195             None
 196         }
 197     }
 198
 199     #[must_use]
 200     pub fn peel_refs(mut self) -> Self {
 201         while let Constant::Ref(r) = self {
 202             self = *r;
 203         }
 204         self
 205     }
 206 }
 207
 208 /// Parses a `LitKind` to a `Constant`.
 209 pub fn lit_to_mir_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
 210     match *lit {
 211         LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
 212         LitKind::Byte(b) => Constant::Int(u128::from(b)),
 213         LitKind::ByteStr(ref s, _) => Constant::Binary(Lrc::clone(s)),
 214         LitKind::Char(c) => Constant::Char(c),
 215         LitKind::Int(n, _) => Constant::Int(n),
 216         LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
 217             ast::FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
 218             ast::FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
 219         },
 220         LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() {
 221             ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
 222             ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
 223             _ => bug!(),
 224         },
 225         LitKind::Bool(b) => Constant::Bool(b),
 226         LitKind::Err => Constant::Err,
 227     }
 228 }
 229
 230 pub fn constant<'tcx>(
 231     lcx: &LateContext<'tcx>,
 232     typeck_results: &ty::TypeckResults<'tcx>,
 233     e: &Expr<'_>,
 234 ) -> Option<(Constant, bool)> {
 235     let mut cx = ConstEvalLateContext {
 236         lcx,
 237         typeck_results,
 238         param_env: lcx.param_env,
 239         needed_resolution: false,
 240         substs: lcx.tcx.intern_substs(&[]),
 241     };
 242     cx.expr(e).map(|cst| (cst, cx.needed_resolution))
 243 }
 244
 245 pub fn constant_simple<'tcx>(
 246     lcx: &LateContext<'tcx>,
 247     typeck_results: &ty::TypeckResults<'tcx>,
 248     e: &Expr<'_>,
 249 ) -> Option<Constant> {
 250     constant(lcx, typeck_results, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
 251 }
 252
 253 pub fn constant_full_int<'tcx>(
 254     lcx: &LateContext<'tcx>,
 255     typeck_results: &ty::TypeckResults<'tcx>,
 256     e: &Expr<'_>,
 257 ) -> Option<FullInt> {
 258     constant_simple(lcx, typeck_results, e)?.int_value(lcx, typeck_results.expr_ty(e))
 259 }
 260
 261 #[derive(Copy, Clone, Debug, Eq)]
 262 pub enum FullInt {
 263     S(i128),
 264     U(u128),
 265 }
 266
 267 impl PartialEq for FullInt {
 268     #[must_use]
 269     fn eq(&self, other: &Self) -> bool {
 270         self.cmp(other) == Ordering::Equal
 271     }
 272 }
 273
 274 impl PartialOrd for FullInt {
 275     #[must_use]
 276     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
 277         Some(self.cmp(other))
 278     }
 279 }
 280
 281 impl Ord for FullInt {
 282     #[must_use]
 283     fn cmp(&self, other: &Self) -> Ordering {
 284         use FullInt::{S, U};
 285
 286         fn cmp_s_u(s: i128, u: u128) -> Ordering {
 287             u128::try_from(s).map_or(Ordering::Less, |x| x.cmp(&u))
 288         }
 289
 290         match (*self, *other) {
 291             (S(s), S(o)) => s.cmp(&o),
 292             (U(s), U(o)) => s.cmp(&o),
 293             (S(s), U(o)) => cmp_s_u(s, o),
 294             (U(s), S(o)) => cmp_s_u(o, s).reverse(),
 295         }
 296     }
 297 }
 298
 299 /// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckResults`.
 300 pub fn constant_context<'a, 'tcx>(
 301     lcx: &'a LateContext<'tcx>,
 302     typeck_results: &'a ty::TypeckResults<'tcx>,
 303 ) -> ConstEvalLateContext<'a, 'tcx> {
 304     ConstEvalLateContext {
 305         lcx,
 306         typeck_results,
 307         param_env: lcx.param_env,
 308         needed_resolution: false,
 309         substs: lcx.tcx.intern_substs(&[]),
 310     }
 311 }
 312
 313 pub struct ConstEvalLateContext<'a, 'tcx> {
 314     lcx: &'a LateContext<'tcx>,
 315     typeck_results: &'a ty::TypeckResults<'tcx>,
 316     param_env: ty::ParamEnv<'tcx>,
 317     needed_resolution: bool,
 318     substs: SubstsRef<'tcx>,
 319 }
 320
 321 impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
 322     /// Simple constant folding: Insert an expression, get a constant or none.
 323     pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
 324         match e.kind {
 325             ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.typeck_results.expr_ty(e)),
 326             ExprKind::Block(block, _) => self.block(block),
 327             ExprKind::Lit(ref lit) => {
 328                 if is_direct_expn_of(e.span, "cfg").is_some() {
 329                     None
 330                 } else {
 331                     Some(lit_to_mir_constant(&lit.node, self.typeck_results.expr_ty_opt(e)))
 332                 }
 333             },
 334             ExprKind::Array(vec) => self.multi(vec).map(Constant::Vec),
 335             ExprKind::Tup(tup) => self.multi(tup).map(Constant::Tuple),
 336             ExprKind::Repeat(value, _) => {
 337                 let n = match self.typeck_results.expr_ty(e).kind() {
 338                     ty::Array(_, n) => n.try_eval_usize(self.lcx.tcx, self.lcx.param_env)?,
 339                     _ => span_bug!(e.span, "typeck error"),
 340                 };
 341                 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
 342             },
 343             ExprKind::Unary(op, operand) => self.expr(operand).and_then(|o| match op {
 344                 UnOp::Not => self.constant_not(&o, self.typeck_results.expr_ty(e)),
 345                 UnOp::Neg => self.constant_negate(&o, self.typeck_results.expr_ty(e)),
 346                 UnOp::Deref => Some(if let Constant::Ref(r) = o { *r } else { o }),
 347             }),
 348             ExprKind::If(cond, then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
 349             ExprKind::Binary(op, left, right) => self.binop(op, left, right),
 350             ExprKind::Call(callee, args) => {
 351                 // We only handle a few const functions for now.
 352                 if_chain! {
 353                     if args.is_empty();
 354                     if let ExprKind::Path(qpath) = &callee.kind;
 355                     let res = self.typeck_results.qpath_res(qpath, callee.hir_id);
 356                     if let Some(def_id) = res.opt_def_id();
 357                     let def_path = self.lcx.get_def_path(def_id);
 358                     let def_path: Vec<&str> = def_path.iter().take(4).map(Symbol::as_str).collect();
 359                     if let ["core", "num", int_impl, "max_value"] = *def_path;
 360                     then {
 361                         let value = match int_impl {
 362                             "<impl i8>" => i8::MAX as u128,
 363                             "<impl i16>" => i16::MAX as u128,
 364                             "<impl i32>" => i32::MAX as u128,
 365                             "<impl i64>" => i64::MAX as u128,
 366                             "<impl i128>" => i128::MAX as u128,
 367                             _ => return None,
 368                         };
 369                         Some(Constant::Int(value))
 370                     } else {
 371                         None
 372                     }
 373                 }
 374             },
 375             ExprKind::Index(arr, index) => self.index(arr, index),
 376             ExprKind::AddrOf(_, _, inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
 377             // TODO: add other expressions.
 378             _ => None,
 379         }
 380     }
 381
 382     #[expect(clippy::cast_possible_wrap)]
 383     fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
 384         use self::Constant::{Bool, Int};
 385         match *o {
 386             Bool(b) => Some(Bool(!b)),
 387             Int(value) => {
 388                 let value = !value;
 389                 match *ty.kind() {
 390                     ty::Int(ity) => Some(Int(unsext(self.lcx.tcx, value as i128, ity))),
 391                     ty::Uint(ity) => Some(Int(clip(self.lcx.tcx, value, ity))),
 392                     _ => None,
 393                 }
 394             },
 395             _ => None,
 396         }
 397     }
 398
 399     fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
 400         use self::Constant::{Int, F32, F64};
 401         match *o {
 402             Int(value) => {
 403                 let ty::Int(ity) = *ty.kind() else { return None };
 404                 // sign extend
 405                 let value = sext(self.lcx.tcx, value, ity);
 406                 let value = value.checked_neg()?;
 407                 // clear unused bits
 408                 Some(Int(unsext(self.lcx.tcx, value, ity)))
 409             },
 410             F32(f) => Some(F32(-f)),
 411             F64(f) => Some(F64(-f)),
 412             _ => None,
 413         }
 414     }
 415
 416     /// Create `Some(Vec![..])` of all constants, unless there is any
 417     /// non-constant part.
 418     fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
 419         vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
 420     }
 421
 422     /// Lookup a possibly constant expression from an `ExprKind::Path`.
 423     fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'tcx>) -> Option<Constant> {
 424         let res = self.typeck_results.qpath_res(qpath, id);
 425         match res {
 426             Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
 427                 // Check if this constant is based on `cfg!(..)`,
 428                 // which is NOT constant for our purposes.
 429                 if let Some(node) = self.lcx.tcx.hir().get_if_local(def_id) &&
 430                 let Node::Item(&Item {
 431                     kind: ItemKind::Const(_, body_id),
 432                     ..
 433                 }) = node &&
 434                 let Node::Expr(&Expr {
 435                     kind: ExprKind::Lit(_),
 436                     span,
 437                     ..
 438                 }) = self.lcx.tcx.hir().get(body_id.hir_id) &&
 439                 is_direct_expn_of(span, "cfg").is_some() {
 440                     return None;
 441                 }
 442
 443                 let substs = self.typeck_results.node_substs(id);
 444                 let substs = if self.substs.is_empty() {
 445                     substs
 446                 } else {
 447                     EarlyBinder(substs).subst(self.lcx.tcx, self.substs)
 448                 };
 449
 450                 let result = self
 451                     .lcx
 452                     .tcx
 453                     .const_eval_resolve(
 454                         self.param_env,
 455                         mir::UnevaluatedConst::new(ty::WithOptConstParam::unknown(def_id), substs),
 456                         None,
 457                     )
 458                     .ok()
 459                     .map(|val| rustc_middle::mir::ConstantKind::from_value(val, ty))?;
 460                 let result = miri_to_const(self.lcx.tcx, result);
 461                 if result.is_some() {
 462                     self.needed_resolution = true;
 463                 }
 464                 result
 465             },
 466             // FIXME: cover all usable cases.
 467             _ => None,
 468         }
 469     }
 470
 471     fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
 472         let lhs = self.expr(lhs);
 473         let index = self.expr(index);
 474
 475         match (lhs, index) {
 476             (Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec.get(index as usize) {
 477                 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
 478                 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
 479                 _ => None,
 480             },
 481             (Some(Constant::Vec(vec)), _) => {
 482                 if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
 483                     match vec.get(0) {
 484                         Some(Constant::F32(x)) => Some(Constant::F32(*x)),
 485                         Some(Constant::F64(x)) => Some(Constant::F64(*x)),
 486                         _ => None,
 487                     }
 488                 } else {
 489                     None
 490                 }
 491             },
 492             _ => None,
 493         }
 494     }
 495
 496     /// A block can only yield a constant if it only has one constant expression.
 497     fn block(&mut self, block: &Block<'_>) -> Option<Constant> {
 498         if block.stmts.is_empty() {
 499             block.expr.as_ref().and_then(|b| self.expr(b))
 500         } else {
 501             None
 502         }
 503     }
 504
 505     fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
 506         if let Some(Constant::Bool(b)) = self.expr(cond) {
 507             if b {
 508                 self.expr(then)
 509             } else {
 510                 otherwise.as_ref().and_then(|expr| self.expr(expr))
 511             }
 512         } else {
 513             None
 514         }
 515     }
 516
 517     fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
 518         let l = self.expr(left)?;
 519         let r = self.expr(right);
 520         match (l, r) {
 521             (Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck_results.expr_ty_opt(left)?.kind() {
 522                 ty::Int(ity) => {
 523                     let l = sext(self.lcx.tcx, l, ity);
 524                     let r = sext(self.lcx.tcx, r, ity);
 525                     let zext = |n: i128| Constant::Int(unsext(self.lcx.tcx, n, ity));
 526                     match op.node {
 527                         BinOpKind::Add => l.checked_add(r).map(zext),
 528                         BinOpKind::Sub => l.checked_sub(r).map(zext),
 529                         BinOpKind::Mul => l.checked_mul(r).map(zext),
 530                         BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
 531                         BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
 532                         BinOpKind::Shr => l.checked_shr(r.try_into().ok()?).map(zext),
 533                         BinOpKind::Shl => l.checked_shl(r.try_into().ok()?).map(zext),
 534                         BinOpKind::BitXor => Some(zext(l ^ r)),
 535                         BinOpKind::BitOr => Some(zext(l | r)),
 536                         BinOpKind::BitAnd => Some(zext(l & r)),
 537                         BinOpKind::Eq => Some(Constant::Bool(l == r)),
 538                         BinOpKind::Ne => Some(Constant::Bool(l != r)),
 539                         BinOpKind::Lt => Some(Constant::Bool(l < r)),
 540                         BinOpKind::Le => Some(Constant::Bool(l <= r)),
 541                         BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 542                         BinOpKind::Gt => Some(Constant::Bool(l > r)),
 543                         _ => None,
 544                     }
 545                 },
 546                 ty::Uint(_) => match op.node {
 547                     BinOpKind::Add => l.checked_add(r).map(Constant::Int),
 548                     BinOpKind::Sub => l.checked_sub(r).map(Constant::Int),
 549                     BinOpKind::Mul => l.checked_mul(r).map(Constant::Int),
 550                     BinOpKind::Div => l.checked_div(r).map(Constant::Int),
 551                     BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
 552                     BinOpKind::Shr => l.checked_shr(r.try_into().ok()?).map(Constant::Int),
 553                     BinOpKind::Shl => l.checked_shl(r.try_into().ok()?).map(Constant::Int),
 554                     BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
 555                     BinOpKind::BitOr => Some(Constant::Int(l | r)),
 556                     BinOpKind::BitAnd => Some(Constant::Int(l & r)),
 557                     BinOpKind::Eq => Some(Constant::Bool(l == r)),
 558                     BinOpKind::Ne => Some(Constant::Bool(l != r)),
 559                     BinOpKind::Lt => Some(Constant::Bool(l < r)),
 560                     BinOpKind::Le => Some(Constant::Bool(l <= r)),
 561                     BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 562                     BinOpKind::Gt => Some(Constant::Bool(l > r)),
 563                     _ => None,
 564                 },
 565                 _ => None,
 566             },
 567             (Constant::F32(l), Some(Constant::F32(r))) => match op.node {
 568                 BinOpKind::Add => Some(Constant::F32(l + r)),
 569                 BinOpKind::Sub => Some(Constant::F32(l - r)),
 570                 BinOpKind::Mul => Some(Constant::F32(l * r)),
 571                 BinOpKind::Div => Some(Constant::F32(l / r)),
 572                 BinOpKind::Rem => Some(Constant::F32(l % r)),
 573                 BinOpKind::Eq => Some(Constant::Bool(l == r)),
 574                 BinOpKind::Ne => Some(Constant::Bool(l != r)),
 575                 BinOpKind::Lt => Some(Constant::Bool(l < r)),
 576                 BinOpKind::Le => Some(Constant::Bool(l <= r)),
 577                 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 578                 BinOpKind::Gt => Some(Constant::Bool(l > r)),
 579                 _ => None,
 580             },
 581             (Constant::F64(l), Some(Constant::F64(r))) => match op.node {
 582                 BinOpKind::Add => Some(Constant::F64(l + r)),
 583                 BinOpKind::Sub => Some(Constant::F64(l - r)),
 584                 BinOpKind::Mul => Some(Constant::F64(l * r)),
 585                 BinOpKind::Div => Some(Constant::F64(l / r)),
 586                 BinOpKind::Rem => Some(Constant::F64(l % r)),
 587                 BinOpKind::Eq => Some(Constant::Bool(l == r)),
 588                 BinOpKind::Ne => Some(Constant::Bool(l != r)),
 589                 BinOpKind::Lt => Some(Constant::Bool(l < r)),
 590                 BinOpKind::Le => Some(Constant::Bool(l <= r)),
 591                 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 592                 BinOpKind::Gt => Some(Constant::Bool(l > r)),
 593                 _ => None,
 594             },
 595             (l, r) => match (op.node, l, r) {
 596                 (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
 597                 (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
 598                 (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
 599                     Some(r)
 600                 },
 601                 (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
 602                 (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
 603                 (BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
 604                 _ => None,
 605             },
 606         }
 607     }
 608 }
 609
 610 pub fn miri_to_const<'tcx>(tcx: TyCtxt<'tcx>, result: mir::ConstantKind<'tcx>) -> Option<Constant> {
 611     use rustc_middle::mir::interpret::ConstValue;
 612     match result {
 613         mir::ConstantKind::Val(ConstValue::Scalar(Scalar::Int(int)), _) => {
 614             match result.ty().kind() {
 615                 ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
 616                 ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.assert_bits(int.size()))),
 617                 ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
 618                     int.try_into().expect("invalid f32 bit representation"),
 619                 ))),
 620                 ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
 621                     int.try_into().expect("invalid f64 bit representation"),
 622                 ))),
 623                 ty::RawPtr(type_and_mut) => {
 624                     if let ty::Uint(_) = type_and_mut.ty.kind() {
 625                         return Some(Constant::RawPtr(int.assert_bits(int.size())));
 626                     }
 627                     None
 628                 },
 629                 // FIXME: implement other conversions.
 630                 _ => None,
 631             }
 632         },
 633         mir::ConstantKind::Val(ConstValue::Slice { data, start, end }, _) => match result.ty().kind() {
 634             ty::Ref(_, tam, _) => match tam.kind() {
 635                 ty::Str => String::from_utf8(
 636                     data.inner()
 637                         .inspect_with_uninit_and_ptr_outside_interpreter(start..end)
 638                         .to_owned(),
 639                 )
 640                 .ok()
 641                 .map(Constant::Str),
 642                 _ => None,
 643             },
 644             _ => None,
 645         },
 646         mir::ConstantKind::Val(ConstValue::ByRef { alloc, offset: _ }, _) => match result.ty().kind() {
 647             ty::Array(sub_type, len) => match sub_type.kind() {
 648                 ty::Float(FloatTy::F32) => match len.kind().try_to_machine_usize(tcx) {
 649                     Some(len) => alloc
 650                         .inner()
 651                         .inspect_with_uninit_and_ptr_outside_interpreter(0..(4 * usize::try_from(len).unwrap()))
 652                         .to_owned()
 653                         .array_chunks::<4>()
 654                         .map(|&chunk| Some(Constant::F32(f32::from_le_bytes(chunk))))
 655                         .collect::<Option<Vec<Constant>>>()
 656                         .map(Constant::Vec),
 657                     _ => None,
 658                 },
 659                 ty::Float(FloatTy::F64) => match len.kind().try_to_machine_usize(tcx) {
 660                     Some(len) => alloc
 661                         .inner()
 662                         .inspect_with_uninit_and_ptr_outside_interpreter(0..(8 * usize::try_from(len).unwrap()))
 663                         .to_owned()
 664                         .array_chunks::<8>()
 665                         .map(|&chunk| Some(Constant::F64(f64::from_le_bytes(chunk))))
 666                         .collect::<Option<Vec<Constant>>>()
 667                         .map(Constant::Vec),
 668                     _ => None,
 669                 },
 670                 // FIXME: implement other array type conversions.
 671                 _ => None,
 672             },
 673             _ => None,
 674         },
 675         // FIXME: implement other conversions.
 676         _ => None,
 677     }
 678 }