src/tools/clippy/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, Item, ItemKind, Node, QPath, UnOp};
   9 use rustc_lint::LateContext;
  10 use rustc_middle::mir;
  11 use rustc_middle::mir::interpret::Scalar;
  12 use rustc_middle::ty::subst::{Subst, SubstsRef};
  13 use rustc_middle::ty::{self, EarlyBinder, FloatTy, ScalarInt, Ty, TyCtxt};
  14 use rustc_middle::{bug, span_bug};
  15 use rustc_span::symbol::Symbol;
  16 use std::cmp::Ordering::{self, Equal};
  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)) => match *cmp_type.kind() {
 134                 ty::Int(int_ty) => Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty))),
 135                 ty::Uint(_) => Some(l.cmp(&r)),
 136                 _ => bug!("Not an int type"),
 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)) => iter::zip(l, r)
 142                 .map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri))
 143                 .find(|r| r.map_or(true, |o| o != Ordering::Equal))
 144                 .unwrap_or_else(|| Some(l.len().cmp(&r.len()))),
 145             (&Self::Repeat(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => {
 146                 match Self::partial_cmp(tcx, cmp_type, lv, rv) {
 147                     Some(Equal) => Some(ls.cmp(rs)),
 148                     x => x,
 149                 }
 150             },
 151             (&Self::Ref(ref lb), &Self::Ref(ref rb)) => Self::partial_cmp(tcx, cmp_type, lb, rb),
 152             // TODO: are there any useful inter-type orderings?
 153             _ => None,
 154         }
 155     }
 156
 157     /// Returns the integer value or `None` if `self` or `val_type` is not integer type.
 158     pub fn int_value(&self, cx: &LateContext<'_>, val_type: Ty<'_>) -> Option<FullInt> {
 159         if let Constant::Int(const_int) = *self {
 160             match *val_type.kind() {
 161                 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
 162                 ty::Uint(_) => Some(FullInt::U(const_int)),
 163                 _ => None,
 164             }
 165         } else {
 166             None
 167         }
 168     }
 169
 170     #[must_use]
 171     pub fn peel_refs(mut self) -> Self {
 172         while let Constant::Ref(r) = self {
 173             self = *r;
 174         }
 175         self
 176     }
 177 }
 178
 179 /// Parses a `LitKind` to a `Constant`.
 180 pub fn lit_to_mir_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
 181     match *lit {
 182         LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
 183         LitKind::Byte(b) => Constant::Int(u128::from(b)),
 184         LitKind::ByteStr(ref s) => Constant::Binary(Lrc::clone(s)),
 185         LitKind::Char(c) => Constant::Char(c),
 186         LitKind::Int(n, _) => Constant::Int(n),
 187         LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
 188             ast::FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
 189             ast::FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
 190         },
 191         LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() {
 192             ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
 193             ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
 194             _ => bug!(),
 195         },
 196         LitKind::Bool(b) => Constant::Bool(b),
 197         LitKind::Err(s) => Constant::Err(s),
 198     }
 199 }
 200
 201 pub fn constant<'tcx>(
 202     lcx: &LateContext<'tcx>,
 203     typeck_results: &ty::TypeckResults<'tcx>,
 204     e: &Expr<'_>,
 205 ) -> Option<(Constant, bool)> {
 206     let mut cx = ConstEvalLateContext {
 207         lcx,
 208         typeck_results,
 209         param_env: lcx.param_env,
 210         needed_resolution: false,
 211         substs: lcx.tcx.intern_substs(&[]),
 212     };
 213     cx.expr(e).map(|cst| (cst, cx.needed_resolution))
 214 }
 215
 216 pub fn constant_simple<'tcx>(
 217     lcx: &LateContext<'tcx>,
 218     typeck_results: &ty::TypeckResults<'tcx>,
 219     e: &Expr<'_>,
 220 ) -> Option<Constant> {
 221     constant(lcx, typeck_results, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
 222 }
 223
 224 pub fn constant_full_int<'tcx>(
 225     lcx: &LateContext<'tcx>,
 226     typeck_results: &ty::TypeckResults<'tcx>,
 227     e: &Expr<'_>,
 228 ) -> Option<FullInt> {
 229     constant_simple(lcx, typeck_results, e)?.int_value(lcx, typeck_results.expr_ty(e))
 230 }
 231
 232 #[derive(Copy, Clone, Debug, Eq)]
 233 pub enum FullInt {
 234     S(i128),
 235     U(u128),
 236 }
 237
 238 impl PartialEq for FullInt {
 239     #[must_use]
 240     fn eq(&self, other: &Self) -> bool {
 241         self.cmp(other) == Ordering::Equal
 242     }
 243 }
 244
 245 impl PartialOrd for FullInt {
 246     #[must_use]
 247     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
 248         Some(self.cmp(other))
 249     }
 250 }
 251
 252 impl Ord for FullInt {
 253     #[must_use]
 254     fn cmp(&self, other: &Self) -> Ordering {
 255         use FullInt::{S, U};
 256
 257         fn cmp_s_u(s: i128, u: u128) -> Ordering {
 258             u128::try_from(s).map_or(Ordering::Less, |x| x.cmp(&u))
 259         }
 260
 261         match (*self, *other) {
 262             (S(s), S(o)) => s.cmp(&o),
 263             (U(s), U(o)) => s.cmp(&o),
 264             (S(s), U(o)) => cmp_s_u(s, o),
 265             (U(s), S(o)) => cmp_s_u(o, s).reverse(),
 266         }
 267     }
 268 }
 269
 270 /// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckResults`.
 271 pub fn constant_context<'a, 'tcx>(
 272     lcx: &'a LateContext<'tcx>,
 273     typeck_results: &'a ty::TypeckResults<'tcx>,
 274 ) -> ConstEvalLateContext<'a, 'tcx> {
 275     ConstEvalLateContext {
 276         lcx,
 277         typeck_results,
 278         param_env: lcx.param_env,
 279         needed_resolution: false,
 280         substs: lcx.tcx.intern_substs(&[]),
 281     }
 282 }
 283
 284 pub struct ConstEvalLateContext<'a, 'tcx> {
 285     lcx: &'a LateContext<'tcx>,
 286     typeck_results: &'a ty::TypeckResults<'tcx>,
 287     param_env: ty::ParamEnv<'tcx>,
 288     needed_resolution: bool,
 289     substs: SubstsRef<'tcx>,
 290 }
 291
 292 impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
 293     /// Simple constant folding: Insert an expression, get a constant or none.
 294     pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
 295         match e.kind {
 296             ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.typeck_results.expr_ty(e)),
 297             ExprKind::Block(block, _) => self.block(block),
 298             ExprKind::Lit(ref lit) => {
 299                 if is_direct_expn_of(e.span, "cfg").is_some() {
 300                     None
 301                 } else {
 302                     Some(lit_to_mir_constant(&lit.node, self.typeck_results.expr_ty_opt(e)))
 303                 }
 304             },
 305             ExprKind::Array(vec) => self.multi(vec).map(Constant::Vec),
 306             ExprKind::Tup(tup) => self.multi(tup).map(Constant::Tuple),
 307             ExprKind::Repeat(value, _) => {
 308                 let n = match self.typeck_results.expr_ty(e).kind() {
 309                     ty::Array(_, n) => n.try_eval_usize(self.lcx.tcx, self.lcx.param_env)?,
 310                     _ => span_bug!(e.span, "typeck error"),
 311                 };
 312                 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
 313             },
 314             ExprKind::Unary(op, operand) => self.expr(operand).and_then(|o| match op {
 315                 UnOp::Not => self.constant_not(&o, self.typeck_results.expr_ty(e)),
 316                 UnOp::Neg => self.constant_negate(&o, self.typeck_results.expr_ty(e)),
 317                 UnOp::Deref => Some(if let Constant::Ref(r) = o { *r } else { o }),
 318             }),
 319             ExprKind::If(cond, then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
 320             ExprKind::Binary(op, left, right) => self.binop(op, left, right),
 321             ExprKind::Call(callee, args) => {
 322                 // We only handle a few const functions for now.
 323                 if_chain! {
 324                     if args.is_empty();
 325                     if let ExprKind::Path(qpath) = &callee.kind;
 326                     let res = self.typeck_results.qpath_res(qpath, callee.hir_id);
 327                     if let Some(def_id) = res.opt_def_id();
 328                     let def_path = self.lcx.get_def_path(def_id);
 329                     let def_path: Vec<&str> = def_path.iter().take(4).map(Symbol::as_str).collect();
 330                     if let ["core", "num", int_impl, "max_value"] = *def_path;
 331                     then {
 332                         let value = match int_impl {
 333                             "<impl i8>" => i8::MAX as u128,
 334                             "<impl i16>" => i16::MAX as u128,
 335                             "<impl i32>" => i32::MAX as u128,
 336                             "<impl i64>" => i64::MAX as u128,
 337                             "<impl i128>" => i128::MAX as u128,
 338                             _ => return None,
 339                         };
 340                         Some(Constant::Int(value))
 341                     } else {
 342                         None
 343                     }
 344                 }
 345             },
 346             ExprKind::Index(arr, index) => self.index(arr, index),
 347             ExprKind::AddrOf(_, _, inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
 348             // TODO: add other expressions.
 349             _ => None,
 350         }
 351     }
 352
 353     #[expect(clippy::cast_possible_wrap)]
 354     fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
 355         use self::Constant::{Bool, Int};
 356         match *o {
 357             Bool(b) => Some(Bool(!b)),
 358             Int(value) => {
 359                 let value = !value;
 360                 match *ty.kind() {
 361                     ty::Int(ity) => Some(Int(unsext(self.lcx.tcx, value as i128, ity))),
 362                     ty::Uint(ity) => Some(Int(clip(self.lcx.tcx, value, ity))),
 363                     _ => None,
 364                 }
 365             },
 366             _ => None,
 367         }
 368     }
 369
 370     fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
 371         use self::Constant::{Int, F32, F64};
 372         match *o {
 373             Int(value) => {
 374                 let ity = match *ty.kind() {
 375                     ty::Int(ity) => ity,
 376                     _ => return None,
 377                 };
 378                 // sign extend
 379                 let value = sext(self.lcx.tcx, value, ity);
 380                 let value = value.checked_neg()?;
 381                 // clear unused bits
 382                 Some(Int(unsext(self.lcx.tcx, value, ity)))
 383             },
 384             F32(f) => Some(F32(-f)),
 385             F64(f) => Some(F64(-f)),
 386             _ => None,
 387         }
 388     }
 389
 390     /// Create `Some(Vec![..])` of all constants, unless there is any
 391     /// non-constant part.
 392     fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
 393         vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
 394     }
 395
 396     /// Lookup a possibly constant expression from an `ExprKind::Path`.
 397     fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'tcx>) -> Option<Constant> {
 398         let res = self.typeck_results.qpath_res(qpath, id);
 399         match res {
 400             Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
 401                 // Check if this constant is based on `cfg!(..)`,
 402                 // which is NOT constant for our purposes.
 403                 if let Some(node) = self.lcx.tcx.hir().get_if_local(def_id) &&
 404                 let Node::Item(&Item {
 405                     kind: ItemKind::Const(_, body_id),
 406                     ..
 407                 }) = node &&
 408                 let Node::Expr(&Expr {
 409                     kind: ExprKind::Lit(_),
 410                     span,
 411                     ..
 412                 }) = self.lcx.tcx.hir().get(body_id.hir_id) &&
 413                 is_direct_expn_of(span, "cfg").is_some() {
 414                     return None;
 415                 }
 416
 417                 let substs = self.typeck_results.node_substs(id);
 418                 let substs = if self.substs.is_empty() {
 419                     substs
 420                 } else {
 421                     EarlyBinder(substs).subst(self.lcx.tcx, self.substs)
 422                 };
 423
 424                 let result = self
 425                     .lcx
 426                     .tcx
 427                     .const_eval_resolve(
 428                         self.param_env,
 429                         ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs),
 430                         None,
 431                     )
 432                     .ok()
 433                     .map(|val| rustc_middle::mir::ConstantKind::from_value(val, ty))?;
 434                 let result = miri_to_const(self.lcx.tcx, result);
 435                 if result.is_some() {
 436                     self.needed_resolution = true;
 437                 }
 438                 result
 439             },
 440             // FIXME: cover all usable cases.
 441             _ => None,
 442         }
 443     }
 444
 445     fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
 446         let lhs = self.expr(lhs);
 447         let index = self.expr(index);
 448
 449         match (lhs, index) {
 450             (Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec.get(index as usize) {
 451                 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
 452                 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
 453                 _ => None,
 454             },
 455             (Some(Constant::Vec(vec)), _) => {
 456                 if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
 457                     match vec.get(0) {
 458                         Some(Constant::F32(x)) => Some(Constant::F32(*x)),
 459                         Some(Constant::F64(x)) => Some(Constant::F64(*x)),
 460                         _ => None,
 461                     }
 462                 } else {
 463                     None
 464                 }
 465             },
 466             _ => None,
 467         }
 468     }
 469
 470     /// A block can only yield a constant if it only has one constant expression.
 471     fn block(&mut self, block: &Block<'_>) -> Option<Constant> {
 472         if block.stmts.is_empty() {
 473             block.expr.as_ref().and_then(|b| self.expr(b))
 474         } else {
 475             None
 476         }
 477     }
 478
 479     fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
 480         if let Some(Constant::Bool(b)) = self.expr(cond) {
 481             if b {
 482                 self.expr(then)
 483             } else {
 484                 otherwise.as_ref().and_then(|expr| self.expr(expr))
 485             }
 486         } else {
 487             None
 488         }
 489     }
 490
 491     fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
 492         let l = self.expr(left)?;
 493         let r = self.expr(right);
 494         match (l, r) {
 495             (Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck_results.expr_ty_opt(left)?.kind() {
 496                 ty::Int(ity) => {
 497                     let l = sext(self.lcx.tcx, l, ity);
 498                     let r = sext(self.lcx.tcx, r, ity);
 499                     let zext = |n: i128| Constant::Int(unsext(self.lcx.tcx, n, ity));
 500                     match op.node {
 501                         BinOpKind::Add => l.checked_add(r).map(zext),
 502                         BinOpKind::Sub => l.checked_sub(r).map(zext),
 503                         BinOpKind::Mul => l.checked_mul(r).map(zext),
 504                         BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
 505                         BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
 506                         BinOpKind::Shr => l.checked_shr(r.try_into().expect("invalid shift")).map(zext),
 507                         BinOpKind::Shl => l.checked_shl(r.try_into().expect("invalid shift")).map(zext),
 508                         BinOpKind::BitXor => Some(zext(l ^ r)),
 509                         BinOpKind::BitOr => Some(zext(l | r)),
 510                         BinOpKind::BitAnd => Some(zext(l & r)),
 511                         BinOpKind::Eq => Some(Constant::Bool(l == r)),
 512                         BinOpKind::Ne => Some(Constant::Bool(l != r)),
 513                         BinOpKind::Lt => Some(Constant::Bool(l < r)),
 514                         BinOpKind::Le => Some(Constant::Bool(l <= r)),
 515                         BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 516                         BinOpKind::Gt => Some(Constant::Bool(l > r)),
 517                         _ => None,
 518                     }
 519                 },
 520                 ty::Uint(_) => match op.node {
 521                     BinOpKind::Add => l.checked_add(r).map(Constant::Int),
 522                     BinOpKind::Sub => l.checked_sub(r).map(Constant::Int),
 523                     BinOpKind::Mul => l.checked_mul(r).map(Constant::Int),
 524                     BinOpKind::Div => l.checked_div(r).map(Constant::Int),
 525                     BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
 526                     BinOpKind::Shr => l.checked_shr(r.try_into().expect("shift too large")).map(Constant::Int),
 527                     BinOpKind::Shl => l.checked_shl(r.try_into().expect("shift too large")).map(Constant::Int),
 528                     BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
 529                     BinOpKind::BitOr => Some(Constant::Int(l | r)),
 530                     BinOpKind::BitAnd => Some(Constant::Int(l & r)),
 531                     BinOpKind::Eq => Some(Constant::Bool(l == r)),
 532                     BinOpKind::Ne => Some(Constant::Bool(l != r)),
 533                     BinOpKind::Lt => Some(Constant::Bool(l < r)),
 534                     BinOpKind::Le => Some(Constant::Bool(l <= r)),
 535                     BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 536                     BinOpKind::Gt => Some(Constant::Bool(l > r)),
 537                     _ => None,
 538                 },
 539                 _ => None,
 540             },
 541             (Constant::F32(l), Some(Constant::F32(r))) => match op.node {
 542                 BinOpKind::Add => Some(Constant::F32(l + r)),
 543                 BinOpKind::Sub => Some(Constant::F32(l - r)),
 544                 BinOpKind::Mul => Some(Constant::F32(l * r)),
 545                 BinOpKind::Div => Some(Constant::F32(l / r)),
 546                 BinOpKind::Rem => Some(Constant::F32(l % r)),
 547                 BinOpKind::Eq => Some(Constant::Bool(l == r)),
 548                 BinOpKind::Ne => Some(Constant::Bool(l != r)),
 549                 BinOpKind::Lt => Some(Constant::Bool(l < r)),
 550                 BinOpKind::Le => Some(Constant::Bool(l <= r)),
 551                 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 552                 BinOpKind::Gt => Some(Constant::Bool(l > r)),
 553                 _ => None,
 554             },
 555             (Constant::F64(l), Some(Constant::F64(r))) => match op.node {
 556                 BinOpKind::Add => Some(Constant::F64(l + r)),
 557                 BinOpKind::Sub => Some(Constant::F64(l - r)),
 558                 BinOpKind::Mul => Some(Constant::F64(l * r)),
 559                 BinOpKind::Div => Some(Constant::F64(l / r)),
 560                 BinOpKind::Rem => Some(Constant::F64(l % r)),
 561                 BinOpKind::Eq => Some(Constant::Bool(l == r)),
 562                 BinOpKind::Ne => Some(Constant::Bool(l != r)),
 563                 BinOpKind::Lt => Some(Constant::Bool(l < r)),
 564                 BinOpKind::Le => Some(Constant::Bool(l <= r)),
 565                 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 566                 BinOpKind::Gt => Some(Constant::Bool(l > r)),
 567                 _ => None,
 568             },
 569             (l, r) => match (op.node, l, r) {
 570                 (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
 571                 (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
 572                 (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
 573                     Some(r)
 574                 },
 575                 (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
 576                 (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
 577                 (BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
 578                 _ => None,
 579             },
 580         }
 581     }
 582 }
 583
 584 pub fn miri_to_const<'tcx>(tcx: TyCtxt<'tcx>, result: mir::ConstantKind<'tcx>) -> Option<Constant> {
 585     use rustc_middle::mir::interpret::ConstValue;
 586     match result {
 587         mir::ConstantKind::Val(ConstValue::Scalar(Scalar::Int(int)), _) => {
 588             match result.ty().kind() {
 589                 ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
 590                 ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.assert_bits(int.size()))),
 591                 ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
 592                     int.try_into().expect("invalid f32 bit representation"),
 593                 ))),
 594                 ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
 595                     int.try_into().expect("invalid f64 bit representation"),
 596                 ))),
 597                 ty::RawPtr(type_and_mut) => {
 598                     if let ty::Uint(_) = type_and_mut.ty.kind() {
 599                         return Some(Constant::RawPtr(int.assert_bits(int.size())));
 600                     }
 601                     None
 602                 },
 603                 // FIXME: implement other conversions.
 604                 _ => None,
 605             }
 606         },
 607         mir::ConstantKind::Val(ConstValue::Slice { data, start, end }, _) => match result.ty().kind() {
 608             ty::Ref(_, tam, _) => match tam.kind() {
 609                 ty::Str => String::from_utf8(
 610                     data.inner()
 611                         .inspect_with_uninit_and_ptr_outside_interpreter(start..end)
 612                         .to_owned(),
 613                 )
 614                 .ok()
 615                 .map(Constant::Str),
 616                 _ => None,
 617             },
 618             _ => None,
 619         },
 620         mir::ConstantKind::Val(ConstValue::ByRef { alloc, offset: _ }, _) => match result.ty().kind() {
 621             ty::Array(sub_type, len) => match sub_type.kind() {
 622                 ty::Float(FloatTy::F32) => match len.to_valtree().try_to_machine_usize(tcx) {
 623                     Some(len) => alloc
 624                         .inner()
 625                         .inspect_with_uninit_and_ptr_outside_interpreter(0..(4 * usize::try_from(len).unwrap()))
 626                         .to_owned()
 627                         .chunks(4)
 628                         .map(|chunk| {
 629                             Some(Constant::F32(f32::from_le_bytes(
 630                                 chunk.try_into().expect("this shouldn't happen"),
 631                             )))
 632                         })
 633                         .collect::<Option<Vec<Constant>>>()
 634                         .map(Constant::Vec),
 635                     _ => None,
 636                 },
 637                 ty::Float(FloatTy::F64) => match len.to_valtree().try_to_machine_usize(tcx) {
 638                     Some(len) => alloc
 639                         .inner()
 640                         .inspect_with_uninit_and_ptr_outside_interpreter(0..(8 * usize::try_from(len).unwrap()))
 641                         .to_owned()
 642                         .chunks(8)
 643                         .map(|chunk| {
 644                             Some(Constant::F64(f64::from_le_bytes(
 645                                 chunk.try_into().expect("this shouldn't happen"),
 646                             )))
 647                         })
 648                         .collect::<Option<Vec<Constant>>>()
 649                         .map(Constant::Vec),
 650                     _ => None,
 651                 },
 652                 // FIXME: implement other array type conversions.
 653                 _ => None,
 654             },
 655             _ => None,
 656         },
 657         // FIXME: implement other conversions.
 658         _ => None,
 659     }
 660 }