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, 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};
19 /// A `LitKind`-like enum to fold constant `Expr`s into.
20 #[derive(Debug, Clone)]
22 /// A `String` (e.g., "abc").
24 /// A binary string (e.g., `b"abc"`).
26 /// A single `char` (e.g., `'a'`).
28 /// An integer's bit representation.
34 /// `true` or `false`.
36 /// An array of constants.
38 /// Also an array, but with only one constant, repeated N times.
39 Repeat(Box<Constant>, u64),
40 /// A tuple of constants.
46 /// A literal with syntax error.
50 impl PartialEq for Constant {
51 fn eq(&self, other: &Self) -> bool {
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()
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()
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?
79 impl Hash for Constant {
80 fn hash<H>(&self, state: &mut H)
84 std::mem::discriminant(self).hash(state);
89 Self::Binary(ref b) => {
99 f64::from(f).to_bits().hash(state);
102 f.to_bits().hash(state);
107 Self::Vec(ref v) | Self::Tuple(ref v) => {
110 Self::Repeat(ref c, l) => {
117 Self::Ref(ref r) => {
120 Self::Err(ref s) => {
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"),
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)),
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?
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)),
170 pub fn peel_refs(mut self) -> Self {
171 while let Constant::Ref(r) = self {
178 /// Parses a `LitKind` to a `Constant`.
179 pub fn lit_to_mir_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
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()),
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()),
195 LitKind::Bool(b) => Constant::Bool(b),
196 LitKind::Err(s) => Constant::Err(s),
200 pub fn constant<'tcx>(
201 lcx: &LateContext<'tcx>,
202 typeck_results: &ty::TypeckResults<'tcx>,
204 ) -> Option<(Constant, bool)> {
205 let mut cx = ConstEvalLateContext {
208 param_env: lcx.param_env,
209 needed_resolution: false,
210 substs: lcx.tcx.intern_substs(&[]),
212 cx.expr(e).map(|cst| (cst, cx.needed_resolution))
215 pub fn constant_simple<'tcx>(
216 lcx: &LateContext<'tcx>,
217 typeck_results: &ty::TypeckResults<'tcx>,
219 ) -> Option<Constant> {
220 constant(lcx, typeck_results, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
223 pub fn constant_full_int<'tcx>(
224 lcx: &LateContext<'tcx>,
225 typeck_results: &ty::TypeckResults<'tcx>,
227 ) -> Option<FullInt> {
228 constant_simple(lcx, typeck_results, e)?.int_value(lcx, typeck_results.expr_ty(e))
231 #[derive(Copy, Clone, Debug, Eq)]
237 impl PartialEq for FullInt {
239 fn eq(&self, other: &Self) -> bool {
240 self.cmp(other) == Ordering::Equal
244 impl PartialOrd for FullInt {
246 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
247 Some(self.cmp(other))
251 impl Ord for FullInt {
253 fn cmp(&self, other: &Self) -> Ordering {
256 fn cmp_s_u(s: i128, u: u128) -> Ordering {
257 u128::try_from(s).map_or(Ordering::Less, |x| x.cmp(&u))
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(),
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 {
277 param_env: lcx.param_env,
278 needed_resolution: false,
279 substs: lcx.tcx.intern_substs(&[]),
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>,
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> {
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() {
301 Some(lit_to_mir_constant(&lit.node, self.typeck_results.expr_ty_opt(e)))
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"),
311 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
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 }),
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.
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;
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,
339 Some(Constant::Int(value))
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.
352 #[expect(clippy::cast_possible_wrap)]
353 fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
354 use self::Constant::{Bool, Int};
356 Bool(b) => Some(Bool(!b)),
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))),
369 fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
370 use self::Constant::{Int, F32, F64};
373 let ity = match *ty.kind() {
378 let value = sext(self.lcx.tcx, value, ity);
379 let value = value.checked_neg()?;
381 Some(Int(unsext(self.lcx.tcx, value, ity)))
383 F32(f) => Some(F32(-f)),
384 F64(f) => Some(F64(-f)),
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<_>>()
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);
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),
407 let Node::Expr(&Expr {
408 kind: ExprKind::Lit(_),
411 }) = self.lcx.tcx.hir().get(body_id.hir_id) &&
412 is_direct_expn_of(span, "cfg").is_some() {
416 let substs = self.typeck_results.node_substs(id);
417 let substs = if self.substs.is_empty() {
420 EarlyBinder(substs).subst(self.lcx.tcx, self.substs)
428 ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs),
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;
439 // FIXME: cover all usable cases.
444 fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
445 let lhs = self.expr(lhs);
446 let index = self.expr(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)),
454 (Some(Constant::Vec(vec)), _) => {
455 if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
457 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
458 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
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))
478 fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
479 if let Some(Constant::Bool(b)) = self.expr(cond) {
483 otherwise.as_ref().and_then(|expr| self.expr(expr))
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);
494 (Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck_results.expr_ty_opt(left)?.kind() {
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));
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)),
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)),
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)),
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)),
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)) => {
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)),
583 pub fn miri_to_const(result: ty::Const<'_>) -> Option<Constant> {
584 use rustc_middle::mir::interpret::ConstValue;
585 match result.kind() {
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"),
593 ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
594 int.try_into().expect("invalid f64 bit representation"),
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())));
602 // FIXME: implement other conversions.
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(
610 .inspect_with_uninit_and_ptr_outside_interpreter(start..end)
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
624 .inspect_with_uninit_and_ptr_outside_interpreter(0..(4 * len as usize))
628 Some(Constant::F32(f32::from_le_bytes(
629 chunk.try_into().expect("this shouldn't happen"),
632 .collect::<Option<Vec<Constant>>>()
636 ty::Float(FloatTy::F64) => match miri_to_const(*len) {
637 Some(Constant::Int(len)) => alloc
639 .inspect_with_uninit_and_ptr_outside_interpreter(0..(8 * len as usize))
643 Some(Constant::F64(f64::from_le_bytes(
644 chunk.try_into().expect("this shouldn't happen"),
647 .collect::<Option<Vec<Constant>>>()
651 // FIXME: implement other array type conversions.
656 // FIXME: implement other conversions.