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::interpret::Scalar;
  11 use rustc_middle::ty::subst::{Subst, SubstsRef};
  12 use rustc_middle::ty::{self, EarlyBinder, FloatTy, ScalarInt, Ty, TyCtxt};
  13 use rustc_middle::{bug, span_bug};
  14 use rustc_span::symbol::Symbol;
  15 use std::cmp::Ordering::{self, Equal};
  16 use std::hash::{Hash, Hasher};
  17 use std::iter;
  18
  19 /// A `LitKind`-like enum to fold constant `Expr`s into.
  20 #[derive(Debug, Clone)]
  21 pub enum Constant {
  22     /// A `String` (e.g., "abc").
  23     Str(String),
  24     /// A binary string (e.g., `b"abc"`).
  25     Binary(Lrc<[u8]>),
  26     /// A single `char` (e.g., `'a'`).
  27     Char(char),
  28     /// An integer's bit representation.
  29     Int(u128),
  30     /// An `f32`.
  31     F32(f32),
  32     /// An `f64`.
  33     F64(f64),
  34     /// `true` or `false`.
  35     Bool(bool),
  36     /// An array of constants.
  37     Vec(Vec<Constant>),
  38     /// Also an array, but with only one constant, repeated N times.
  39     Repeat(Box<Constant>, u64),
  40     /// A tuple of constants.
  41     Tuple(Vec<Constant>),
  42     /// A raw pointer.
  43     RawPtr(u128),
  44     /// A reference
  45     Ref(Box<Constant>),
  46     /// A literal with syntax error.
  47     Err(Symbol),
  48 }
  49
  50 impl PartialEq for Constant {
  51     fn eq(&self, other: &Self) -> bool {
  52         match (self, other) {
  53             (&Self::Str(ref ls), &Self::Str(ref rs)) => ls == rs,
  54             (&Self::Binary(ref l), &Self::Binary(ref r)) => l == r,
  55             (&Self::Char(l), &Self::Char(r)) => l == r,
  56             (&Self::Int(l), &Self::Int(r)) => l == r,
  57             (&Self::F64(l), &Self::F64(r)) => {
  58                 // We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have
  59                 // `Fw32 == Fw64`, so don’t compare them.
  60                 // `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs.
  61                 l.to_bits() == r.to_bits()
  62             },
  63             (&Self::F32(l), &Self::F32(r)) => {
  64                 // We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have
  65                 // `Fw32 == Fw64`, so don’t compare them.
  66                 // `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs.
  67                 f64::from(l).to_bits() == f64::from(r).to_bits()
  68             },
  69             (&Self::Bool(l), &Self::Bool(r)) => l == r,
  70             (&Self::Vec(ref l), &Self::Vec(ref r)) | (&Self::Tuple(ref l), &Self::Tuple(ref r)) => l == r,
  71             (&Self::Repeat(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => ls == rs && lv == rv,
  72             (&Self::Ref(ref lb), &Self::Ref(ref rb)) => *lb == *rb,
  73             // TODO: are there inter-type equalities?
  74             _ => false,
  75         }
  76     }
  77 }
  78
  79 impl Hash for Constant {
  80     fn hash<H>(&self, state: &mut H)
  81     where
  82         H: Hasher,
  83     {
  84         std::mem::discriminant(self).hash(state);
  85         match *self {
  86             Self::Str(ref s) => {
  87                 s.hash(state);
  88             },
  89             Self::Binary(ref b) => {
  90                 b.hash(state);
  91             },
  92             Self::Char(c) => {
  93                 c.hash(state);
  94             },
  95             Self::Int(i) => {
  96                 i.hash(state);
  97             },
  98             Self::F32(f) => {
  99                 f64::from(f).to_bits().hash(state);
 100             },
 101             Self::F64(f) => {
 102                 f.to_bits().hash(state);
 103             },
 104             Self::Bool(b) => {
 105                 b.hash(state);
 106             },
 107             Self::Vec(ref v) | Self::Tuple(ref v) => {
 108                 v.hash(state);
 109             },
 110             Self::Repeat(ref c, l) => {
 111                 c.hash(state);
 112                 l.hash(state);
 113             },
 114             Self::RawPtr(u) => {
 115                 u.hash(state);
 116             },
 117             Self::Ref(ref r) => {
 118                 r.hash(state);
 119             },
 120             Self::Err(ref s) => {
 121                 s.hash(state);
 122             },
 123         }
 124     }
 125 }
 126
 127 impl Constant {
 128     pub fn partial_cmp(tcx: TyCtxt<'_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option<Ordering> {
 129         match (left, right) {
 130             (&Self::Str(ref ls), &Self::Str(ref rs)) => Some(ls.cmp(rs)),
 131             (&Self::Char(ref l), &Self::Char(ref r)) => Some(l.cmp(r)),
 132             (&Self::Int(l), &Self::Int(r)) => match *cmp_type.kind() {
 133                 ty::Int(int_ty) => Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty))),
 134                 ty::Uint(_) => Some(l.cmp(&r)),
 135                 _ => bug!("Not an int type"),
 136             },
 137             (&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r),
 138             (&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r),
 139             (&Self::Bool(ref l), &Self::Bool(ref r)) => Some(l.cmp(r)),
 140             (&Self::Tuple(ref l), &Self::Tuple(ref r)) | (&Self::Vec(ref l), &Self::Vec(ref r)) => iter::zip(l, r)
 141                 .map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri))
 142                 .find(|r| r.map_or(true, |o| o != Ordering::Equal))
 143                 .unwrap_or_else(|| Some(l.len().cmp(&r.len()))),
 144             (&Self::Repeat(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => {
 145                 match Self::partial_cmp(tcx, cmp_type, lv, rv) {
 146                     Some(Equal) => Some(ls.cmp(rs)),
 147                     x => x,
 148                 }
 149             },
 150             (&Self::Ref(ref lb), &Self::Ref(ref rb)) => Self::partial_cmp(tcx, cmp_type, lb, rb),
 151             // TODO: are there any useful inter-type orderings?
 152             _ => None,
 153         }
 154     }
 155
 156     /// Returns the integer value or `None` if `self` or `val_type` is not integer type.
 157     pub fn int_value(&self, cx: &LateContext<'_>, val_type: Ty<'_>) -> Option<FullInt> {
 158         if let Constant::Int(const_int) = *self {
 159             match *val_type.kind() {
 160                 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
 161                 ty::Uint(_) => Some(FullInt::U(const_int)),
 162                 _ => None,
 163             }
 164         } else {
 165             None
 166         }
 167     }
 168
 169     #[must_use]
 170     pub fn peel_refs(mut self) -> Self {
 171         while let Constant::Ref(r) = self {
 172             self = *r;
 173         }
 174         self
 175     }
 176 }
 177
 178 /// Parses a `LitKind` to a `Constant`.
 179 pub fn lit_to_mir_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
 180     match *lit {
 181         LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
 182         LitKind::Byte(b) => Constant::Int(u128::from(b)),
 183         LitKind::ByteStr(ref s) => Constant::Binary(Lrc::clone(s)),
 184         LitKind::Char(c) => Constant::Char(c),
 185         LitKind::Int(n, _) => Constant::Int(n),
 186         LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
 187             ast::FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
 188             ast::FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
 189         },
 190         LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() {
 191             ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
 192             ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
 193             _ => bug!(),
 194         },
 195         LitKind::Bool(b) => Constant::Bool(b),
 196         LitKind::Err(s) => Constant::Err(s),
 197     }
 198 }
 199
 200 pub fn constant<'tcx>(
 201     lcx: &LateContext<'tcx>,
 202     typeck_results: &ty::TypeckResults<'tcx>,
 203     e: &Expr<'_>,
 204 ) -> Option<(Constant, bool)> {
 205     let mut cx = ConstEvalLateContext {
 206         lcx,
 207         typeck_results,
 208         param_env: lcx.param_env,
 209         needed_resolution: false,
 210         substs: lcx.tcx.intern_substs(&[]),
 211     };
 212     cx.expr(e).map(|cst| (cst, cx.needed_resolution))
 213 }
 214
 215 pub fn constant_simple<'tcx>(
 216     lcx: &LateContext<'tcx>,
 217     typeck_results: &ty::TypeckResults<'tcx>,
 218     e: &Expr<'_>,
 219 ) -> Option<Constant> {
 220     constant(lcx, typeck_results, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
 221 }
 222
 223 pub fn constant_full_int<'tcx>(
 224     lcx: &LateContext<'tcx>,
 225     typeck_results: &ty::TypeckResults<'tcx>,
 226     e: &Expr<'_>,
 227 ) -> Option<FullInt> {
 228     constant_simple(lcx, typeck_results, e)?.int_value(lcx, typeck_results.expr_ty(e))
 229 }
 230
 231 #[derive(Copy, Clone, Debug, Eq)]
 232 pub enum FullInt {
 233     S(i128),
 234     U(u128),
 235 }
 236
 237 impl PartialEq for FullInt {
 238     #[must_use]
 239     fn eq(&self, other: &Self) -> bool {
 240         self.cmp(other) == Ordering::Equal
 241     }
 242 }
 243
 244 impl PartialOrd for FullInt {
 245     #[must_use]
 246     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
 247         Some(self.cmp(other))
 248     }
 249 }
 250
 251 impl Ord for FullInt {
 252     #[must_use]
 253     fn cmp(&self, other: &Self) -> Ordering {
 254         use FullInt::{S, U};
 255
 256         fn cmp_s_u(s: i128, u: u128) -> Ordering {
 257             u128::try_from(s).map_or(Ordering::Less, |x| x.cmp(&u))
 258         }
 259
 260         match (*self, *other) {
 261             (S(s), S(o)) => s.cmp(&o),
 262             (U(s), U(o)) => s.cmp(&o),
 263             (S(s), U(o)) => cmp_s_u(s, o),
 264             (U(s), S(o)) => cmp_s_u(o, s).reverse(),
 265         }
 266     }
 267 }
 268
 269 /// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckResults`.
 270 pub fn constant_context<'a, 'tcx>(
 271     lcx: &'a LateContext<'tcx>,
 272     typeck_results: &'a ty::TypeckResults<'tcx>,
 273 ) -> ConstEvalLateContext<'a, 'tcx> {
 274     ConstEvalLateContext {
 275         lcx,
 276         typeck_results,
 277         param_env: lcx.param_env,
 278         needed_resolution: false,
 279         substs: lcx.tcx.intern_substs(&[]),
 280     }
 281 }
 282
 283 pub struct ConstEvalLateContext<'a, 'tcx> {
 284     lcx: &'a LateContext<'tcx>,
 285     typeck_results: &'a ty::TypeckResults<'tcx>,
 286     param_env: ty::ParamEnv<'tcx>,
 287     needed_resolution: bool,
 288     substs: SubstsRef<'tcx>,
 289 }
 290
 291 impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
 292     /// Simple constant folding: Insert an expression, get a constant or none.
 293     pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
 294         match e.kind {
 295             ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.typeck_results.expr_ty(e)),
 296             ExprKind::Block(block, _) => self.block(block),
 297             ExprKind::Lit(ref lit) => {
 298                 if is_direct_expn_of(e.span, "cfg").is_some() {
 299                     None
 300                 } else {
 301                     Some(lit_to_mir_constant(&lit.node, self.typeck_results.expr_ty_opt(e)))
 302                 }
 303             },
 304             ExprKind::Array(vec) => self.multi(vec).map(Constant::Vec),
 305             ExprKind::Tup(tup) => self.multi(tup).map(Constant::Tuple),
 306             ExprKind::Repeat(value, _) => {
 307                 let n = match self.typeck_results.expr_ty(e).kind() {
 308                     ty::Array(_, n) => n.try_eval_usize(self.lcx.tcx, self.lcx.param_env)?,
 309                     _ => span_bug!(e.span, "typeck error"),
 310                 };
 311                 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
 312             },
 313             ExprKind::Unary(op, operand) => self.expr(operand).and_then(|o| match op {
 314                 UnOp::Not => self.constant_not(&o, self.typeck_results.expr_ty(e)),
 315                 UnOp::Neg => self.constant_negate(&o, self.typeck_results.expr_ty(e)),
 316                 UnOp::Deref => Some(if let Constant::Ref(r) = o { *r } else { o }),
 317             }),
 318             ExprKind::If(cond, then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
 319             ExprKind::Binary(op, left, right) => self.binop(op, left, right),
 320             ExprKind::Call(callee, args) => {
 321                 // We only handle a few const functions for now.
 322                 if_chain! {
 323                     if args.is_empty();
 324                     if let ExprKind::Path(qpath) = &callee.kind;
 325                     let res = self.typeck_results.qpath_res(qpath, callee.hir_id);
 326                     if let Some(def_id) = res.opt_def_id();
 327                     let def_path = self.lcx.get_def_path(def_id);
 328                     let def_path: Vec<&str> = def_path.iter().take(4).map(Symbol::as_str).collect();
 329                     if let ["core", "num", int_impl, "max_value"] = *def_path;
 330                     then {
 331                         let value = match int_impl {
 332                             "<impl i8>" => i8::MAX as u128,
 333                             "<impl i16>" => i16::MAX as u128,
 334                             "<impl i32>" => i32::MAX as u128,
 335                             "<impl i64>" => i64::MAX as u128,
 336                             "<impl i128>" => i128::MAX as u128,
 337                             _ => return None,
 338                         };
 339                         Some(Constant::Int(value))
 340                     } else {
 341                         None
 342                     }
 343                 }
 344             },
 345             ExprKind::Index(arr, index) => self.index(arr, index),
 346             ExprKind::AddrOf(_, _, inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
 347             // TODO: add other expressions.
 348             _ => None,
 349         }
 350     }
 351
 352     #[expect(clippy::cast_possible_wrap)]
 353     fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
 354         use self::Constant::{Bool, Int};
 355         match *o {
 356             Bool(b) => Some(Bool(!b)),
 357             Int(value) => {
 358                 let value = !value;
 359                 match *ty.kind() {
 360                     ty::Int(ity) => Some(Int(unsext(self.lcx.tcx, value as i128, ity))),
 361                     ty::Uint(ity) => Some(Int(clip(self.lcx.tcx, value, ity))),
 362                     _ => None,
 363                 }
 364             },
 365             _ => None,
 366         }
 367     }
 368
 369     fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
 370         use self::Constant::{Int, F32, F64};
 371         match *o {
 372             Int(value) => {
 373                 let ity = match *ty.kind() {
 374                     ty::Int(ity) => ity,
 375                     _ => return None,
 376                 };
 377                 // sign extend
 378                 let value = sext(self.lcx.tcx, value, ity);
 379                 let value = value.checked_neg()?;
 380                 // clear unused bits
 381                 Some(Int(unsext(self.lcx.tcx, value, ity)))
 382             },
 383             F32(f) => Some(F32(-f)),
 384             F64(f) => Some(F64(-f)),
 385             _ => None,
 386         }
 387     }
 388
 389     /// Create `Some(Vec![..])` of all constants, unless there is any
 390     /// non-constant part.
 391     fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
 392         vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
 393     }
 394
 395     /// Lookup a possibly constant expression from an `ExprKind::Path`.
 396     fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'tcx>) -> Option<Constant> {
 397         let res = self.typeck_results.qpath_res(qpath, id);
 398         match res {
 399             Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
 400                 // Check if this constant is based on `cfg!(..)`,
 401                 // which is NOT constant for our purposes.
 402                 if let Some(node) = self.lcx.tcx.hir().get_if_local(def_id) &&
 403                 let Node::Item(&Item {
 404                     kind: ItemKind::Const(_, body_id),
 405                     ..
 406                 }) = node &&
 407                 let Node::Expr(&Expr {
 408                     kind: ExprKind::Lit(_),
 409                     span,
 410                     ..
 411                 }) = self.lcx.tcx.hir().get(body_id.hir_id) &&
 412                 is_direct_expn_of(span, "cfg").is_some() {
 413                     return None;
 414                 }
 415
 416                 let substs = self.typeck_results.node_substs(id);
 417                 let substs = if self.substs.is_empty() {
 418                     substs
 419                 } else {
 420                     EarlyBinder(substs).subst(self.lcx.tcx, self.substs)
 421                 };
 422
 423                 let result = self
 424                     .lcx
 425                     .tcx
 426                     .const_eval_resolve(
 427                         self.param_env,
 428                         ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs),
 429                         None,
 430                     )
 431                     .ok()
 432                     .map(|val| rustc_middle::ty::Const::from_value(self.lcx.tcx, val, ty))?;
 433                 let result = miri_to_const(result);
 434                 if result.is_some() {
 435                     self.needed_resolution = true;
 436                 }
 437                 result
 438             },
 439             // FIXME: cover all usable cases.
 440             _ => None,
 441         }
 442     }
 443
 444     fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
 445         let lhs = self.expr(lhs);
 446         let index = self.expr(index);
 447
 448         match (lhs, index) {
 449             (Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec.get(index as usize) {
 450                 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
 451                 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
 452                 _ => None,
 453             },
 454             (Some(Constant::Vec(vec)), _) => {
 455                 if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
 456                     match vec.get(0) {
 457                         Some(Constant::F32(x)) => Some(Constant::F32(*x)),
 458                         Some(Constant::F64(x)) => Some(Constant::F64(*x)),
 459                         _ => None,
 460                     }
 461                 } else {
 462                     None
 463                 }
 464             },
 465             _ => None,
 466         }
 467     }
 468
 469     /// A block can only yield a constant if it only has one constant expression.
 470     fn block(&mut self, block: &Block<'_>) -> Option<Constant> {
 471         if block.stmts.is_empty() {
 472             block.expr.as_ref().and_then(|b| self.expr(b))
 473         } else {
 474             None
 475         }
 476     }
 477
 478     fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
 479         if let Some(Constant::Bool(b)) = self.expr(cond) {
 480             if b {
 481                 self.expr(then)
 482             } else {
 483                 otherwise.as_ref().and_then(|expr| self.expr(expr))
 484             }
 485         } else {
 486             None
 487         }
 488     }
 489
 490     fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
 491         let l = self.expr(left)?;
 492         let r = self.expr(right);
 493         match (l, r) {
 494             (Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck_results.expr_ty_opt(left)?.kind() {
 495                 ty::Int(ity) => {
 496                     let l = sext(self.lcx.tcx, l, ity);
 497                     let r = sext(self.lcx.tcx, r, ity);
 498                     let zext = |n: i128| Constant::Int(unsext(self.lcx.tcx, n, ity));
 499                     match op.node {
 500                         BinOpKind::Add => l.checked_add(r).map(zext),
 501                         BinOpKind::Sub => l.checked_sub(r).map(zext),
 502                         BinOpKind::Mul => l.checked_mul(r).map(zext),
 503                         BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
 504                         BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
 505                         BinOpKind::Shr => l.checked_shr(r.try_into().expect("invalid shift")).map(zext),
 506                         BinOpKind::Shl => l.checked_shl(r.try_into().expect("invalid shift")).map(zext),
 507                         BinOpKind::BitXor => Some(zext(l ^ r)),
 508                         BinOpKind::BitOr => Some(zext(l | r)),
 509                         BinOpKind::BitAnd => Some(zext(l & r)),
 510                         BinOpKind::Eq => Some(Constant::Bool(l == r)),
 511                         BinOpKind::Ne => Some(Constant::Bool(l != r)),
 512                         BinOpKind::Lt => Some(Constant::Bool(l < r)),
 513                         BinOpKind::Le => Some(Constant::Bool(l <= r)),
 514                         BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 515                         BinOpKind::Gt => Some(Constant::Bool(l > r)),
 516                         _ => None,
 517                     }
 518                 },
 519                 ty::Uint(_) => match op.node {
 520                     BinOpKind::Add => l.checked_add(r).map(Constant::Int),
 521                     BinOpKind::Sub => l.checked_sub(r).map(Constant::Int),
 522                     BinOpKind::Mul => l.checked_mul(r).map(Constant::Int),
 523                     BinOpKind::Div => l.checked_div(r).map(Constant::Int),
 524                     BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
 525                     BinOpKind::Shr => l.checked_shr(r.try_into().expect("shift too large")).map(Constant::Int),
 526                     BinOpKind::Shl => l.checked_shl(r.try_into().expect("shift too large")).map(Constant::Int),
 527                     BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
 528                     BinOpKind::BitOr => Some(Constant::Int(l | r)),
 529                     BinOpKind::BitAnd => Some(Constant::Int(l & r)),
 530                     BinOpKind::Eq => Some(Constant::Bool(l == r)),
 531                     BinOpKind::Ne => Some(Constant::Bool(l != r)),
 532                     BinOpKind::Lt => Some(Constant::Bool(l < r)),
 533                     BinOpKind::Le => Some(Constant::Bool(l <= r)),
 534                     BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 535                     BinOpKind::Gt => Some(Constant::Bool(l > r)),
 536                     _ => None,
 537                 },
 538                 _ => None,
 539             },
 540             (Constant::F32(l), Some(Constant::F32(r))) => match op.node {
 541                 BinOpKind::Add => Some(Constant::F32(l + r)),
 542                 BinOpKind::Sub => Some(Constant::F32(l - r)),
 543                 BinOpKind::Mul => Some(Constant::F32(l * r)),
 544                 BinOpKind::Div => Some(Constant::F32(l / r)),
 545                 BinOpKind::Rem => Some(Constant::F32(l % r)),
 546                 BinOpKind::Eq => Some(Constant::Bool(l == r)),
 547                 BinOpKind::Ne => Some(Constant::Bool(l != r)),
 548                 BinOpKind::Lt => Some(Constant::Bool(l < r)),
 549                 BinOpKind::Le => Some(Constant::Bool(l <= r)),
 550                 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 551                 BinOpKind::Gt => Some(Constant::Bool(l > r)),
 552                 _ => None,
 553             },
 554             (Constant::F64(l), Some(Constant::F64(r))) => match op.node {
 555                 BinOpKind::Add => Some(Constant::F64(l + r)),
 556                 BinOpKind::Sub => Some(Constant::F64(l - r)),
 557                 BinOpKind::Mul => Some(Constant::F64(l * r)),
 558                 BinOpKind::Div => Some(Constant::F64(l / r)),
 559                 BinOpKind::Rem => Some(Constant::F64(l % r)),
 560                 BinOpKind::Eq => Some(Constant::Bool(l == r)),
 561                 BinOpKind::Ne => Some(Constant::Bool(l != r)),
 562                 BinOpKind::Lt => Some(Constant::Bool(l < r)),
 563                 BinOpKind::Le => Some(Constant::Bool(l <= r)),
 564                 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
 565                 BinOpKind::Gt => Some(Constant::Bool(l > r)),
 566                 _ => None,
 567             },
 568             (l, r) => match (op.node, l, r) {
 569                 (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
 570                 (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
 571                 (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
 572                     Some(r)
 573                 },
 574                 (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
 575                 (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
 576                 (BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
 577                 _ => None,
 578             },
 579         }
 580     }
 581 }
 582
 583 pub fn miri_to_const(result: ty::Const<'_>) -> Option<Constant> {
 584     use rustc_middle::mir::interpret::ConstValue;
 585     match result.val() {
 586         ty::ConstKind::Value(ConstValue::Scalar(Scalar::Int(int))) => {
 587             match result.ty().kind() {
 588                 ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
 589                 ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.assert_bits(int.size()))),
 590                 ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
 591                     int.try_into().expect("invalid f32 bit representation"),
 592                 ))),
 593                 ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
 594                     int.try_into().expect("invalid f64 bit representation"),
 595                 ))),
 596                 ty::RawPtr(type_and_mut) => {
 597                     if let ty::Uint(_) = type_and_mut.ty.kind() {
 598                         return Some(Constant::RawPtr(int.assert_bits(int.size())));
 599                     }
 600                     None
 601                 },
 602                 // FIXME: implement other conversions.
 603                 _ => None,
 604             }
 605         },
 606         ty::ConstKind::Value(ConstValue::Slice { data, start, end }) => match result.ty().kind() {
 607             ty::Ref(_, tam, _) => match tam.kind() {
 608                 ty::Str => String::from_utf8(
 609                     data.inner()
 610                         .inspect_with_uninit_and_ptr_outside_interpreter(start..end)
 611                         .to_owned(),
 612                 )
 613                 .ok()
 614                 .map(Constant::Str),
 615                 _ => None,
 616             },
 617             _ => None,
 618         },
 619         ty::ConstKind::Value(ConstValue::ByRef { alloc, offset: _ }) => match result.ty().kind() {
 620             ty::Array(sub_type, len) => match sub_type.kind() {
 621                 ty::Float(FloatTy::F32) => match miri_to_const(*len) {
 622                     Some(Constant::Int(len)) => alloc
 623                         .inner()
 624                         .inspect_with_uninit_and_ptr_outside_interpreter(0..(4 * len as usize))
 625                         .to_owned()
 626                         .chunks(4)
 627                         .map(|chunk| {
 628                             Some(Constant::F32(f32::from_le_bytes(
 629                                 chunk.try_into().expect("this shouldn't happen"),
 630                             )))
 631                         })
 632                         .collect::<Option<Vec<Constant>>>()
 633                         .map(Constant::Vec),
 634                     _ => None,
 635                 },
 636                 ty::Float(FloatTy::F64) => match miri_to_const(*len) {
 637                     Some(Constant::Int(len)) => alloc
 638                         .inner()
 639                         .inspect_with_uninit_and_ptr_outside_interpreter(0..(8 * len as usize))
 640                         .to_owned()
 641                         .chunks(8)
 642                         .map(|chunk| {
 643                             Some(Constant::F64(f64::from_le_bytes(
 644                                 chunk.try_into().expect("this shouldn't happen"),
 645                             )))
 646                         })
 647                         .collect::<Option<Vec<Constant>>>()
 648                         .map(Constant::Vec),
 649                     _ => None,
 650                 },
 651                 // FIXME: implement other array type conversions.
 652                 _ => None,
 653             },
 654             _ => None,
 655         },
 656         // FIXME: implement other conversions.
 657         _ => None,
 658     }
 659 }