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