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