clippy_utils/src/consts.rs

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