src/tools/clippy/clippy_lints/src/consts.rs

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