1 #![allow(clippy::float_cmp)]
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, 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, 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::convert::TryInto;
17 use std::hash::{Hash, Hasher};
20 /// A `LitKind`-like enum to fold constant `Expr`s into.
21 #[derive(Debug, Clone)]
23 /// A `String` (e.g., "abc").
25 /// A binary string (e.g., `b"abc"`).
27 /// A single `char` (e.g., `'a'`).
29 /// An integer's bit representation.
35 /// `true` or `false`.
37 /// An array of constants.
39 /// Also an array, but with only one constant, repeated N times.
40 Repeat(Box<Constant>, u64),
41 /// A tuple of constants.
47 /// A literal with syntax error.
51 impl PartialEq for Constant {
52 fn eq(&self, other: &Self) -> bool {
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()
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()
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?
80 impl Hash for Constant {
81 fn hash<H>(&self, state: &mut H)
85 std::mem::discriminant(self).hash(state);
90 Self::Binary(ref b) => {
100 f64::from(f).to_bits().hash(state);
103 f.to_bits().hash(state);
108 Self::Vec(ref v) | Self::Tuple(ref v) => {
111 Self::Repeat(ref c, l) => {
118 Self::Ref(ref r) => {
121 Self::Err(ref s) => {
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)) => {
134 if let ty::Int(int_ty) = *cmp_type.kind() {
135 Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty)))
140 (&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r),
141 (&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r),
142 (&Self::Bool(ref l), &Self::Bool(ref r)) => Some(l.cmp(r)),
143 (&Self::Tuple(ref l), &Self::Tuple(ref r)) | (&Self::Vec(ref l), &Self::Vec(ref r)) => iter::zip(l, r)
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)),
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?
159 /// Returns the integer value or `None` if `self` or `val_type` is not integer type.
160 pub fn int_value(&self, cx: &LateContext<'_>, val_type: Ty<'_>) -> Option<FullInt> {
161 if let Constant::Int(const_int) = *self {
162 match *val_type.kind() {
163 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
164 ty::Uint(_) => Some(FullInt::U(const_int)),
173 pub fn peel_refs(mut self) -> Self {
174 while let Constant::Ref(r) = self {
181 /// Parses a `LitKind` to a `Constant`.
182 pub fn lit_to_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
184 LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
185 LitKind::Byte(b) => Constant::Int(u128::from(b)),
186 LitKind::ByteStr(ref s) => Constant::Binary(Lrc::clone(s)),
187 LitKind::Char(c) => Constant::Char(c),
188 LitKind::Int(n, _) => Constant::Int(n),
189 LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
190 ast::FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
191 ast::FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
193 LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() {
194 ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
195 ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
198 LitKind::Bool(b) => Constant::Bool(b),
199 LitKind::Err(s) => Constant::Err(s),
203 pub fn constant<'tcx>(
204 lcx: &LateContext<'tcx>,
205 typeck_results: &ty::TypeckResults<'tcx>,
207 ) -> Option<(Constant, bool)> {
208 let mut cx = ConstEvalLateContext {
211 param_env: lcx.param_env,
212 needed_resolution: false,
213 substs: lcx.tcx.intern_substs(&[]),
215 cx.expr(e).map(|cst| (cst, cx.needed_resolution))
218 pub fn constant_simple<'tcx>(
219 lcx: &LateContext<'tcx>,
220 typeck_results: &ty::TypeckResults<'tcx>,
222 ) -> Option<Constant> {
223 constant(lcx, typeck_results, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
226 pub fn constant_full_int(
227 lcx: &LateContext<'tcx>,
228 typeck_results: &ty::TypeckResults<'tcx>,
230 ) -> Option<FullInt> {
231 constant_simple(lcx, typeck_results, e)?.int_value(lcx, typeck_results.expr_ty(e))
234 #[derive(Copy, Clone, Debug, Eq)]
240 impl PartialEq for FullInt {
242 fn eq(&self, other: &Self) -> bool {
243 self.cmp(other) == Ordering::Equal
247 impl PartialOrd for FullInt {
249 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
250 Some(self.cmp(other))
254 impl Ord for FullInt {
256 fn cmp(&self, other: &Self) -> Ordering {
259 fn cmp_s_u(s: i128, u: u128) -> Ordering {
260 u128::try_from(s).map_or(Ordering::Less, |x| x.cmp(&u))
263 match (*self, *other) {
264 (S(s), S(o)) => s.cmp(&o),
265 (U(s), U(o)) => s.cmp(&o),
266 (S(s), U(o)) => cmp_s_u(s, o),
267 (U(s), S(o)) => cmp_s_u(o, s).reverse(),
272 /// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckResults`.
273 pub fn constant_context<'a, 'tcx>(
274 lcx: &'a LateContext<'tcx>,
275 typeck_results: &'a ty::TypeckResults<'tcx>,
276 ) -> ConstEvalLateContext<'a, 'tcx> {
277 ConstEvalLateContext {
280 param_env: lcx.param_env,
281 needed_resolution: false,
282 substs: lcx.tcx.intern_substs(&[]),
286 pub struct ConstEvalLateContext<'a, 'tcx> {
287 lcx: &'a LateContext<'tcx>,
288 typeck_results: &'a ty::TypeckResults<'tcx>,
289 param_env: ty::ParamEnv<'tcx>,
290 needed_resolution: bool,
291 substs: SubstsRef<'tcx>,
294 impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
295 /// Simple constant folding: Insert an expression, get a constant or none.
296 pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
298 ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.typeck_results.expr_ty(e)),
299 ExprKind::Block(block, _) => self.block(block),
300 ExprKind::Lit(ref lit) => {
301 if is_direct_expn_of(e.span, "cfg").is_some() {
304 Some(lit_to_constant(&lit.node, self.typeck_results.expr_ty_opt(e)))
307 ExprKind::Array(vec) => self.multi(vec).map(Constant::Vec),
308 ExprKind::Tup(tup) => self.multi(tup).map(Constant::Tuple),
309 ExprKind::Repeat(value, _) => {
310 let n = match self.typeck_results.expr_ty(e).kind() {
311 ty::Array(_, n) => n.try_eval_usize(self.lcx.tcx, self.lcx.param_env)?,
312 _ => span_bug!(e.span, "typeck error"),
314 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
316 ExprKind::Unary(op, operand) => self.expr(operand).and_then(|o| match op {
317 UnOp::Not => self.constant_not(&o, self.typeck_results.expr_ty(e)),
318 UnOp::Neg => self.constant_negate(&o, self.typeck_results.expr_ty(e)),
319 UnOp::Deref => Some(if let Constant::Ref(r) = o { *r } else { o }),
321 ExprKind::If(cond, then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
322 ExprKind::Binary(op, left, right) => self.binop(op, left, right),
323 ExprKind::Call(callee, args) => {
324 // We only handle a few const functions for now.
327 if let ExprKind::Path(qpath) = &callee.kind;
328 let res = self.typeck_results.qpath_res(qpath, callee.hir_id);
329 if let Some(def_id) = res.opt_def_id();
330 let def_path = self.lcx.get_def_path(def_id);
331 let def_path: Vec<&str> = def_path.iter().take(4).map(Symbol::as_str).collect();
332 if let ["core", "num", int_impl, "max_value"] = *def_path;
334 let value = match int_impl {
335 "<impl i8>" => i8::MAX as u128,
336 "<impl i16>" => i16::MAX as u128,
337 "<impl i32>" => i32::MAX as u128,
338 "<impl i64>" => i64::MAX as u128,
339 "<impl i128>" => i128::MAX as u128,
342 Some(Constant::Int(value))
349 ExprKind::Index(arr, index) => self.index(arr, index),
350 ExprKind::AddrOf(_, _, inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
351 // TODO: add other expressions.
356 #[allow(clippy::cast_possible_wrap)]
357 fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
358 use self::Constant::{Bool, Int};
360 Bool(b) => Some(Bool(!b)),
364 ty::Int(ity) => Some(Int(unsext(self.lcx.tcx, value as i128, ity))),
365 ty::Uint(ity) => Some(Int(clip(self.lcx.tcx, value, ity))),
373 fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
374 use self::Constant::{Int, F32, F64};
377 let ity = match *ty.kind() {
382 let value = sext(self.lcx.tcx, value, ity);
383 let value = value.checked_neg()?;
385 Some(Int(unsext(self.lcx.tcx, value, ity)))
387 F32(f) => Some(F32(-f)),
388 F64(f) => Some(F64(-f)),
393 /// Create `Some(Vec![..])` of all constants, unless there is any
394 /// non-constant part.
395 fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
396 vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
399 /// Lookup a possibly constant expression from an `ExprKind::Path`.
400 fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'tcx>) -> Option<Constant> {
401 let res = self.typeck_results.qpath_res(qpath, id);
403 Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
404 let substs = self.typeck_results.node_substs(id);
405 let substs = if self.substs.is_empty() {
408 substs.subst(self.lcx.tcx, self.substs)
416 ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs),
420 .map(|val| rustc_middle::ty::Const::from_value(self.lcx.tcx, val, ty))?;
421 let result = miri_to_const(result);
422 if result.is_some() {
423 self.needed_resolution = true;
427 // FIXME: cover all usable cases.
432 fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
433 let lhs = self.expr(lhs);
434 let index = self.expr(index);
437 (Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec.get(index as usize) {
438 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
439 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
442 (Some(Constant::Vec(vec)), _) => {
443 if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
445 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
446 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
457 /// A block can only yield a constant if it only has one constant expression.
458 fn block(&mut self, block: &Block<'_>) -> Option<Constant> {
459 if block.stmts.is_empty() {
460 block.expr.as_ref().and_then(|b| self.expr(b))
466 fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
467 if let Some(Constant::Bool(b)) = self.expr(cond) {
471 otherwise.as_ref().and_then(|expr| self.expr(expr))
478 fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
479 let l = self.expr(left)?;
480 let r = self.expr(right);
482 (Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck_results.expr_ty_opt(left)?.kind() {
484 let l = sext(self.lcx.tcx, l, ity);
485 let r = sext(self.lcx.tcx, r, ity);
486 let zext = |n: i128| Constant::Int(unsext(self.lcx.tcx, n, ity));
488 BinOpKind::Add => l.checked_add(r).map(zext),
489 BinOpKind::Sub => l.checked_sub(r).map(zext),
490 BinOpKind::Mul => l.checked_mul(r).map(zext),
491 BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
492 BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
493 BinOpKind::Shr => l.checked_shr(r.try_into().expect("invalid shift")).map(zext),
494 BinOpKind::Shl => l.checked_shl(r.try_into().expect("invalid shift")).map(zext),
495 BinOpKind::BitXor => Some(zext(l ^ r)),
496 BinOpKind::BitOr => Some(zext(l | r)),
497 BinOpKind::BitAnd => Some(zext(l & r)),
498 BinOpKind::Eq => Some(Constant::Bool(l == r)),
499 BinOpKind::Ne => Some(Constant::Bool(l != r)),
500 BinOpKind::Lt => Some(Constant::Bool(l < r)),
501 BinOpKind::Le => Some(Constant::Bool(l <= r)),
502 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
503 BinOpKind::Gt => Some(Constant::Bool(l > r)),
507 ty::Uint(_) => match op.node {
508 BinOpKind::Add => l.checked_add(r).map(Constant::Int),
509 BinOpKind::Sub => l.checked_sub(r).map(Constant::Int),
510 BinOpKind::Mul => l.checked_mul(r).map(Constant::Int),
511 BinOpKind::Div => l.checked_div(r).map(Constant::Int),
512 BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
513 BinOpKind::Shr => l.checked_shr(r.try_into().expect("shift too large")).map(Constant::Int),
514 BinOpKind::Shl => l.checked_shl(r.try_into().expect("shift too large")).map(Constant::Int),
515 BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
516 BinOpKind::BitOr => Some(Constant::Int(l | r)),
517 BinOpKind::BitAnd => Some(Constant::Int(l & r)),
518 BinOpKind::Eq => Some(Constant::Bool(l == r)),
519 BinOpKind::Ne => Some(Constant::Bool(l != r)),
520 BinOpKind::Lt => Some(Constant::Bool(l < r)),
521 BinOpKind::Le => Some(Constant::Bool(l <= r)),
522 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
523 BinOpKind::Gt => Some(Constant::Bool(l > r)),
528 (Constant::F32(l), Some(Constant::F32(r))) => match op.node {
529 BinOpKind::Add => Some(Constant::F32(l + r)),
530 BinOpKind::Sub => Some(Constant::F32(l - r)),
531 BinOpKind::Mul => Some(Constant::F32(l * r)),
532 BinOpKind::Div => Some(Constant::F32(l / r)),
533 BinOpKind::Rem => Some(Constant::F32(l % r)),
534 BinOpKind::Eq => Some(Constant::Bool(l == r)),
535 BinOpKind::Ne => Some(Constant::Bool(l != r)),
536 BinOpKind::Lt => Some(Constant::Bool(l < r)),
537 BinOpKind::Le => Some(Constant::Bool(l <= r)),
538 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
539 BinOpKind::Gt => Some(Constant::Bool(l > r)),
542 (Constant::F64(l), Some(Constant::F64(r))) => match op.node {
543 BinOpKind::Add => Some(Constant::F64(l + r)),
544 BinOpKind::Sub => Some(Constant::F64(l - r)),
545 BinOpKind::Mul => Some(Constant::F64(l * r)),
546 BinOpKind::Div => Some(Constant::F64(l / r)),
547 BinOpKind::Rem => Some(Constant::F64(l % r)),
548 BinOpKind::Eq => Some(Constant::Bool(l == r)),
549 BinOpKind::Ne => Some(Constant::Bool(l != r)),
550 BinOpKind::Lt => Some(Constant::Bool(l < r)),
551 BinOpKind::Le => Some(Constant::Bool(l <= r)),
552 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
553 BinOpKind::Gt => Some(Constant::Bool(l > r)),
556 (l, r) => match (op.node, l, r) {
557 (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
558 (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
559 (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
562 (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
563 (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
564 (BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
571 pub fn miri_to_const(result: &ty::Const<'_>) -> Option<Constant> {
572 use rustc_middle::mir::interpret::ConstValue;
574 ty::ConstKind::Value(ConstValue::Scalar(Scalar::Int(int))) => {
575 match result.ty.kind() {
576 ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
577 ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.assert_bits(int.size()))),
578 ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
579 int.try_into().expect("invalid f32 bit representation"),
581 ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
582 int.try_into().expect("invalid f64 bit representation"),
584 ty::RawPtr(type_and_mut) => {
585 if let ty::Uint(_) = type_and_mut.ty.kind() {
586 return Some(Constant::RawPtr(int.assert_bits(int.size())));
590 // FIXME: implement other conversions.
594 ty::ConstKind::Value(ConstValue::Slice { data, start, end }) => match result.ty.kind() {
595 ty::Ref(_, tam, _) => match tam.kind() {
596 ty::Str => String::from_utf8(
597 data.inspect_with_uninit_and_ptr_outside_interpreter(start..end)
606 ty::ConstKind::Value(ConstValue::ByRef { alloc, offset: _ }) => match result.ty.kind() {
607 ty::Array(sub_type, len) => match sub_type.kind() {
608 ty::Float(FloatTy::F32) => match miri_to_const(len) {
609 Some(Constant::Int(len)) => alloc
610 .inspect_with_uninit_and_ptr_outside_interpreter(0..(4 * len as usize))
614 Some(Constant::F32(f32::from_le_bytes(
615 chunk.try_into().expect("this shouldn't happen"),
618 .collect::<Option<Vec<Constant>>>()
622 ty::Float(FloatTy::F64) => match miri_to_const(len) {
623 Some(Constant::Int(len)) => alloc
624 .inspect_with_uninit_and_ptr_outside_interpreter(0..(8 * len as usize))
628 Some(Constant::F64(f64::from_le_bytes(
629 chunk.try_into().expect("this shouldn't happen"),
632 .collect::<Option<Vec<Constant>>>()
636 // FIXME: implement other array type conversions.
641 // FIXME: implement other conversions.