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, QPath, UnOp};
   9 use rustc_lint::LateContext;
  10 use rustc_middle::mir::interpret::Scalar;
  11 use rustc_middle::ty::subst::{Subst, SubstsRef};
  12 use rustc_middle::ty::{self, FloatTy, ScalarInt, Ty, TyCtxt};
  13 use rustc_middle::{bug, span_bug};
  14 use rustc_span::symbol::Symbol;
  15 use std::cmp::Ordering::{self, Equal};
  16 use std::convert::TryInto;
  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(Symbol),
  49 }
  50
  51 impl PartialEq for Constant {
  52     fn eq(&self, other: &Self) -> bool {
  53         match (self, other) {
  54             (&Self::Str(ref ls), &Self::Str(ref rs)) => ls == rs,
  55             (&Self::Binary(ref l), &Self::Binary(ref 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(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => ls == rs && lv == rv,
  73             (&Self::Ref(ref lb), &Self::Ref(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(ref s) => {
 122                 s.hash(state);
 123             },
 124         }
 125     }
 126 }
 127
 128 impl Constant {
 129     pub fn partial_cmp(tcx: TyCtxt<'_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option<Ordering> {
 130         match (left, right) {
 131             (&Self::Str(ref ls), &Self::Str(ref rs)) => Some(ls.cmp(rs)),
 132             (&Self::Char(ref l), &Self::Char(ref r)) => Some(l.cmp(r)),
 133             (&Self::Int(l), &Self::Int(r)) => {
 134                 if let ty::Int(int_ty) = *cmp_type.kind() {
 135                     Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty)))
 136                 } else {
 137                     Some(l.cmp(&r))
 138                 }
 139             },
 140             (&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r),
 141             (&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r),
 142             (&Self::Bool(ref l), &Self::Bool(ref r)) => Some(l.cmp(r)),
 143             (&Self::Tuple(ref l), &Self::Tuple(ref r)) | (&Self::Vec(ref l), &Self::Vec(ref r)) => iter::zip(l, r)
 144                 .map(|(li, ri)| 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             (&Self::Repeat(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => {
 148                 match Self::partial_cmp(tcx, cmp_type, lv, rv) {
 149                     Some(Equal) => Some(ls.cmp(rs)),
 150                     x => x,
 151                 }
 152             },
 153             (&Self::Ref(ref lb), &Self::Ref(ref rb)) => Self::partial_cmp(tcx, cmp_type, lb, rb),
 154             // TODO: are there any useful inter-type orderings?
 155             _ => None,
 156         }
 157     }
 158
 159     /// Returns the integer value or `None` if `self` or `val_type` is not integer type.
 160     pub fn int_value(&self, cx: &LateContext<'_>, val_type: Ty<'_>) -> Option<FullInt> {
 161         if let Constant::Int(const_int) = *self {
 162             match *val_type.kind() {
 163                 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
 164                 ty::Uint(_) => Some(FullInt::U(const_int)),
 165                 _ => None,
 166             }
 167         } else {
 168             None
 169         }
 170     }
 171 }
 172
 173 /// Parses a `LitKind` to a `Constant`.
 174 pub fn lit_to_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
 175     match *lit {
 176         LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
 177         LitKind::Byte(b) => Constant::Int(u128::from(b)),
 178         LitKind::ByteStr(ref s) => Constant::Binary(Lrc::clone(s)),
 179         LitKind::Char(c) => Constant::Char(c),
 180         LitKind::Int(n, _) => Constant::Int(n),
 181         LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
 182             ast::FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
 183             ast::FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
 184         },
 185         LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() {
 186             ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
 187             ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
 188             _ => bug!(),
 189         },
 190         LitKind::Bool(b) => Constant::Bool(b),
 191         LitKind::Err(s) => Constant::Err(s),
 192     }
 193 }
 194
 195 pub fn constant<'tcx>(
 196     lcx: &LateContext<'tcx>,
 197     typeck_results: &ty::TypeckResults<'tcx>,
 198     e: &Expr<'_>,
 199 ) -> Option<(Constant, bool)> {
 200     let mut cx = ConstEvalLateContext {
 201         lcx,
 202         typeck_results,
 203         param_env: lcx.param_env,
 204         needed_resolution: false,
 205         substs: lcx.tcx.intern_substs(&[]),
 206     };
 207     cx.expr(e).map(|cst| (cst, cx.needed_resolution))
 208 }
 209
 210 pub fn constant_simple<'tcx>(
 211     lcx: &LateContext<'tcx>,
 212     typeck_results: &ty::TypeckResults<'tcx>,
 213     e: &Expr<'_>,
 214 ) -> Option<Constant> {
 215     constant(lcx, typeck_results, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
 216 }
 217
 218 pub fn constant_full_int(
 219     lcx: &LateContext<'tcx>,
 220     typeck_results: &ty::TypeckResults<'tcx>,
 221     e: &Expr<'_>,
 222 ) -> Option<FullInt> {
 223     constant_simple(lcx, typeck_results, e)?.int_value(lcx, typeck_results.expr_ty(e))
 224 }
 225
 226 #[derive(Copy, Clone, Debug, Eq)]
 227 pub enum FullInt {
 228     S(i128),
 229     U(u128),
 230 }
 231
 232 impl PartialEq for FullInt {
 233     #[must_use]
 234     fn eq(&self, other: &Self) -> bool {
 235         self.cmp(other) == Ordering::Equal
 236     }
 237 }
 238
 239 impl PartialOrd for FullInt {
 240     #[must_use]
 241     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
 242         Some(self.cmp(other))
 243     }
 244 }
 245
 246 impl Ord for FullInt {
 247     #[must_use]
 248     fn cmp(&self, other: &Self) -> Ordering {
 249         use FullInt::{S, U};
 250
 251         fn cmp_s_u(s: i128, u: u128) -> Ordering {
 252             u128::try_from(s).map_or(Ordering::Less, |x| x.cmp(&u))
 253         }
 254
 255         match (*self, *other) {
 256             (S(s), S(o)) => s.cmp(&o),
 257             (U(s), U(o)) => s.cmp(&o),
 258             (S(s), U(o)) => cmp_s_u(s, o),
 259             (U(s), S(o)) => cmp_s_u(o, s).reverse(),
 260         }
 261     }
 262 }
 263
 264 /// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckResults`.
 265 pub fn constant_context<'a, 'tcx>(
 266     lcx: &'a LateContext<'tcx>,
 267     typeck_results: &'a ty::TypeckResults<'tcx>,
 268 ) -> ConstEvalLateContext<'a, 'tcx> {
 269     ConstEvalLateContext {
 270         lcx,
 271         typeck_results,
 272         param_env: lcx.param_env,
 273         needed_resolution: false,
 274         substs: lcx.tcx.intern_substs(&[]),
 275     }
 276 }
 277
 278 pub struct ConstEvalLateContext<'a, 'tcx> {
 279     lcx: &'a LateContext<'tcx>,
 280     typeck_results: &'a ty::TypeckResults<'tcx>,
 281     param_env: ty::ParamEnv<'tcx>,
 282     needed_resolution: bool,
 283     substs: SubstsRef<'tcx>,
 284 }
 285
 286 impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
 287     /// Simple constant folding: Insert an expression, get a constant or none.
 288     pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
 289         match e.kind {
 290             ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.typeck_results.expr_ty(e)),
 291             ExprKind::Block(block, _) => self.block(block),
 292             ExprKind::Lit(ref lit) => {
 293                 if is_direct_expn_of(e.span, "cfg").is_some() {
 294                     None
 295                 } else {
 296                     Some(lit_to_constant(&lit.node, self.typeck_results.expr_ty_opt(e)))
 297                 }
 298             },
 299             ExprKind::Array(vec) => self.multi(vec).map(Constant::Vec),
 300             ExprKind::Tup(tup) => self.multi(tup).map(Constant::Tuple),
 301             ExprKind::Repeat(value, _) => {
 302                 let n = match self.typeck_results.expr_ty(e).kind() {
 303                     ty::Array(_, n) => n.try_eval_usize(self.lcx.tcx, self.lcx.param_env)?,
 304                     _ => span_bug!(e.span, "typeck error"),
 305                 };
 306                 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
 307             },
 308             ExprKind::Unary(op, operand) => self.expr(operand).and_then(|o| match op {
 309                 UnOp::Not => self.constant_not(&o, self.typeck_results.expr_ty(e)),
 310                 UnOp::Neg => self.constant_negate(&o, self.typeck_results.expr_ty(e)),
 311                 UnOp::Deref => Some(if let Constant::Ref(r) = o { *r } else { o }),
 312             }),
 313             ExprKind::If(cond, then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
 314             ExprKind::Binary(op, left, right) => self.binop(op, left, right),
 315             ExprKind::Call(callee, args) => {
 316                 // We only handle a few const functions for now.
 317                 if_chain! {
 318                     if args.is_empty();
 319                     if let ExprKind::Path(qpath) = &callee.kind;
 320                     let res = self.typeck_results.qpath_res(qpath, callee.hir_id);
 321                     if let Some(def_id) = res.opt_def_id();
 322                     let def_path: Vec<_> = self.lcx.get_def_path(def_id).into_iter().map(Symbol::as_str).collect();
 323                     let def_path: Vec<&str> = def_path.iter().take(4).map(|s| &**s).collect();
 324                     if let ["core", "num", int_impl, "max_value"] = *def_path;
 325                     then {
 326                        let value = match int_impl {
 327                            "<impl i8>" => i8::MAX as u128,
 328                            "<impl i16>" => i16::MAX as u128,
 329                            "<impl i32>" => i32::MAX as u128,
 330                            "<impl i64>" => i64::MAX as u128,
 331                            "<impl i128>" => i128::MAX as u128,
 332                            _ => return None,
 333                        };
 334                        Some(Constant::Int(value))
 335                     }
 336                     else {
 337                         None
 338                     }
 339                 }
 340             },
 341             ExprKind::Index(arr, index) => self.index(arr, index),
 342             ExprKind::AddrOf(_, _, inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
 343             // TODO: add other expressions.
 344             _ => None,
 345         }
 346     }
 347
 348     #[allow(clippy::cast_possible_wrap)]
 349     fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
 350         use self::Constant::{Bool, Int};
 351         match *o {
 352             Bool(b) => Some(Bool(!b)),
 353             Int(value) => {
 354                 let value = !value;
 355                 match *ty.kind() {
 356                     ty::Int(ity) => Some(Int(unsext(self.lcx.tcx, value as i128, ity))),
 357                     ty::Uint(ity) => Some(Int(clip(self.lcx.tcx, value, ity))),
 358                     _ => None,
 359                 }
 360             },
 361             _ => None,
 362         }
 363     }
 364
 365     fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
 366         use self::Constant::{Int, F32, F64};
 367         match *o {
 368             Int(value) => {
 369                 let ity = match *ty.kind() {
 370                     ty::Int(ity) => ity,
 371                     _ => return None,
 372                 };
 373                 // sign extend
 374                 let value = sext(self.lcx.tcx, value, ity);
 375                 let value = value.checked_neg()?;
 376                 // clear unused bits
 377                 Some(Int(unsext(self.lcx.tcx, value, ity)))
 378             },
 379             F32(f) => Some(F32(-f)),
 380             F64(f) => Some(F64(-f)),
 381             _ => None,
 382         }
 383     }
 384
 385     /// Create `Some(Vec![..])` of all constants, unless there is any
 386     /// non-constant part.
 387     fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
 388         vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
 389     }
 390
 391     /// Lookup a possibly constant expression from an `ExprKind::Path`.
 392     fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'tcx>) -> Option<Constant> {
 393         let res = self.typeck_results.qpath_res(qpath, id);
 394         match res {
 395             Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
 396                 let substs = self.typeck_results.node_substs(id);
 397                 let substs = if self.substs.is_empty() {
 398                     substs
 399                 } else {
 400                     substs.subst(self.lcx.tcx, self.substs)
 401                 };
 402
 403                 let result = self
 404                     .lcx
 405                     .tcx
 406                     .const_eval_resolve(
 407                         self.param_env,
 408                         ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs),
 409                         None,
 410                     )
 411                     .ok()
 412                     .map(|val| rustc_middle::ty::Const::from_value(self.lcx.tcx, val, ty))?;
 413                 let result = miri_to_const(result);
 414                 if result.is_some() {
 415                     self.needed_resolution = true;
 416                 }
 417                 result
 418             },
 419             // FIXME: cover all usable cases.
 420             _ => None,
 421         }
 422     }
 423
 424     fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
 425         let lhs = self.expr(lhs);
 426         let index = self.expr(index);
 427
 428         match (lhs, index) {
 429             (Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec.get(index as usize) {
 430                 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
 431                 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
 432                 _ => None,
 433             },
 434             (Some(Constant::Vec(vec)), _) => {
 435                 if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
 436                     match vec.get(0) {
 437                         Some(Constant::F32(x)) => Some(Constant::F32(*x)),
 438                         Some(Constant::F64(x)) => Some(Constant::F64(*x)),
 439                         _ => None,
 440                     }
 441                 } else {
 442                     None
 443                 }
 444             },
 445             _ => None,
 446         }
 447     }
 448
 449     /// A block can only yield a constant if it only has one constant expression.
 450     fn block(&mut self, block: &Block<'_>) -> Option<Constant> {
 451         if block.stmts.is_empty() {
 452             block.expr.as_ref().and_then(|b| self.expr(b))
 453         } else {
 454             None
 455         }
 456     }
 457
 458     fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
 459         if let Some(Constant::Bool(b)) = self.expr(cond) {
 460             if b {
 461                 self.expr(&*then)
 462             } else {
 463                 otherwise.as_ref().and_then(|expr| self.expr(expr))
 464             }
 465         } else {
 466             None
 467         }
 468     }
 469
 470     fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
 471         let l = self.expr(left)?;
 472         let r = self.expr(right);
 473         match (l, r) {
 474             (Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck_results.expr_ty_opt(left)?.kind() {
 475                 ty::Int(ity) => {
 476                     let l = sext(self.lcx.tcx, l, ity);
 477                     let r = sext(self.lcx.tcx, r, ity);
 478                     let zext = |n: i128| Constant::Int(unsext(self.lcx.tcx, n, ity));
 479                     match op.node {
 480                         BinOpKind::Add => l.checked_add(r).map(zext),
 481                         BinOpKind::Sub => l.checked_sub(r).map(zext),
 482                         BinOpKind::Mul => l.checked_mul(r).map(zext),
 483                         BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
 484                         BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
 485                         BinOpKind::Shr => l.checked_shr(r.try_into().expect("invalid shift")).map(zext),
 486                         BinOpKind::Shl => l.checked_shl(r.try_into().expect("invalid shift")).map(zext),
 487                         BinOpKind::BitXor => Some(zext(l ^ r)),
 488                         BinOpKind::BitOr => Some(zext(l | r)),
 489                         BinOpKind::BitAnd => Some(zext(l & r)),
 490                         BinOpKind::Eq => Some(Constant::Bool(l == r)),
 491                         BinOpKind::Ne => Some(Constant::Bool(l != r)),
 492                         BinOpKind::Lt => Some(Constant::Bool(l < r)),
 493                         BinOpKind::Le => Some(Constant::Bool(l <= r)),
 494                         BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 495                         BinOpKind::Gt => Some(Constant::Bool(l > r)),
 496                         _ => None,
 497                     }
 498                 },
 499                 ty::Uint(_) => match op.node {
 500                     BinOpKind::Add => l.checked_add(r).map(Constant::Int),
 501                     BinOpKind::Sub => l.checked_sub(r).map(Constant::Int),
 502                     BinOpKind::Mul => l.checked_mul(r).map(Constant::Int),
 503                     BinOpKind::Div => l.checked_div(r).map(Constant::Int),
 504                     BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
 505                     BinOpKind::Shr => l.checked_shr(r.try_into().expect("shift too large")).map(Constant::Int),
 506                     BinOpKind::Shl => l.checked_shl(r.try_into().expect("shift too large")).map(Constant::Int),
 507                     BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
 508                     BinOpKind::BitOr => Some(Constant::Int(l | r)),
 509                     BinOpKind::BitAnd => Some(Constant::Int(l & r)),
 510                     BinOpKind::Eq => Some(Constant::Bool(l == r)),
 511                     BinOpKind::Ne => Some(Constant::Bool(l != r)),
 512                     BinOpKind::Lt => Some(Constant::Bool(l < r)),
 513                     BinOpKind::Le => Some(Constant::Bool(l <= r)),
 514                     BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 515                     BinOpKind::Gt => Some(Constant::Bool(l > r)),
 516                     _ => None,
 517                 },
 518                 _ => None,
 519             },
 520             (Constant::F32(l), Some(Constant::F32(r))) => match op.node {
 521                 BinOpKind::Add => Some(Constant::F32(l + r)),
 522                 BinOpKind::Sub => Some(Constant::F32(l - r)),
 523                 BinOpKind::Mul => Some(Constant::F32(l * r)),
 524                 BinOpKind::Div => Some(Constant::F32(l / r)),
 525                 BinOpKind::Rem => Some(Constant::F32(l % r)),
 526                 BinOpKind::Eq => Some(Constant::Bool(l == r)),
 527                 BinOpKind::Ne => Some(Constant::Bool(l != r)),
 528                 BinOpKind::Lt => Some(Constant::Bool(l < r)),
 529                 BinOpKind::Le => Some(Constant::Bool(l <= r)),
 530                 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 531                 BinOpKind::Gt => Some(Constant::Bool(l > r)),
 532                 _ => None,
 533             },
 534             (Constant::F64(l), Some(Constant::F64(r))) => match op.node {
 535                 BinOpKind::Add => Some(Constant::F64(l + r)),
 536                 BinOpKind::Sub => Some(Constant::F64(l - r)),
 537                 BinOpKind::Mul => Some(Constant::F64(l * r)),
 538                 BinOpKind::Div => Some(Constant::F64(l / r)),
 539                 BinOpKind::Rem => Some(Constant::F64(l % r)),
 540                 BinOpKind::Eq => Some(Constant::Bool(l == r)),
 541                 BinOpKind::Ne => Some(Constant::Bool(l != r)),
 542                 BinOpKind::Lt => Some(Constant::Bool(l < r)),
 543                 BinOpKind::Le => Some(Constant::Bool(l <= r)),
 544                 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 545                 BinOpKind::Gt => Some(Constant::Bool(l > r)),
 546                 _ => None,
 547             },
 548             (l, r) => match (op.node, l, r) {
 549                 (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
 550                 (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
 551                 (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
 552                     Some(r)
 553                 },
 554                 (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
 555                 (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
 556                 (BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
 557                 _ => None,
 558             },
 559         }
 560     }
 561 }
 562
 563 pub fn miri_to_const(result: &ty::Const<'_>) -> Option<Constant> {
 564     use rustc_middle::mir::interpret::ConstValue;
 565     match result.val {
 566         ty::ConstKind::Value(ConstValue::Scalar(Scalar::Int(int))) => {
 567             match result.ty.kind() {
 568                 ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
 569                 ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.assert_bits(int.size()))),
 570                 ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
 571                     int.try_into().expect("invalid f32 bit representation"),
 572                 ))),
 573                 ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
 574                     int.try_into().expect("invalid f64 bit representation"),
 575                 ))),
 576                 ty::RawPtr(type_and_mut) => {
 577                     if let ty::Uint(_) = type_and_mut.ty.kind() {
 578                         return Some(Constant::RawPtr(int.assert_bits(int.size())));
 579                     }
 580                     None
 581                 },
 582                 // FIXME: implement other conversions.
 583                 _ => None,
 584             }
 585         },
 586         ty::ConstKind::Value(ConstValue::Slice { data, start, end }) => match result.ty.kind() {
 587             ty::Ref(_, tam, _) => match tam.kind() {
 588                 ty::Str => String::from_utf8(
 589                     data.inspect_with_uninit_and_ptr_outside_interpreter(start..end)
 590                         .to_owned(),
 591                 )
 592                 .ok()
 593                 .map(Constant::Str),
 594                 _ => None,
 595             },
 596             _ => None,
 597         },
 598         ty::ConstKind::Value(ConstValue::ByRef { alloc, offset: _ }) => match result.ty.kind() {
 599             ty::Array(sub_type, len) => match sub_type.kind() {
 600                 ty::Float(FloatTy::F32) => match miri_to_const(len) {
 601                     Some(Constant::Int(len)) => alloc
 602                         .inspect_with_uninit_and_ptr_outside_interpreter(0..(4 * len as usize))
 603                         .to_owned()
 604                         .chunks(4)
 605                         .map(|chunk| {
 606                             Some(Constant::F32(f32::from_le_bytes(
 607                                 chunk.try_into().expect("this shouldn't happen"),
 608                             )))
 609                         })
 610                         .collect::<Option<Vec<Constant>>>()
 611                         .map(Constant::Vec),
 612                     _ => None,
 613                 },
 614                 ty::Float(FloatTy::F64) => match miri_to_const(len) {
 615                     Some(Constant::Int(len)) => alloc
 616                         .inspect_with_uninit_and_ptr_outside_interpreter(0..(8 * len as usize))
 617                         .to_owned()
 618                         .chunks(8)
 619                         .map(|chunk| {
 620                             Some(Constant::F64(f64::from_le_bytes(
 621                                 chunk.try_into().expect("this shouldn't happen"),
 622                             )))
 623                         })
 624                         .collect::<Option<Vec<Constant>>>()
 625                         .map(Constant::Vec),
 626                     _ => None,
 627                 },
 628                 // FIXME: implement other array type conversions.
 629                 _ => None,
 630             },
 631             _ => None,
 632         },
 633         // FIXME: implement other conversions.
 634         _ => None,
 635     }
 636 }