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