1 #![allow(clippy::float_cmp)]
3 use crate::{clip, 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};
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)) => {
133 if let ty::Int(int_ty) = *cmp_type.kind() {
134 Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty)))
139 (&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r),
140 (&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r),
141 (&Self::Bool(ref l), &Self::Bool(ref r)) => Some(l.cmp(r)),
142 (&Self::Tuple(ref l), &Self::Tuple(ref r)) | (&Self::Vec(ref l), &Self::Vec(ref r)) => l
145 .map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri))
146 .find(|r| r.map_or(true, |o| o != Ordering::Equal))
147 .unwrap_or_else(|| Some(l.len().cmp(&r.len()))),
148 (&Self::Repeat(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => {
149 match Self::partial_cmp(tcx, cmp_type, lv, rv) {
150 Some(Equal) => Some(ls.cmp(rs)),
154 (&Self::Ref(ref lb), &Self::Ref(ref rb)) => Self::partial_cmp(tcx, cmp_type, lb, rb),
155 // TODO: are there any useful inter-type orderings?
161 /// Parses a `LitKind` to a `Constant`.
162 pub fn lit_to_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
164 LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
165 LitKind::Byte(b) => Constant::Int(u128::from(b)),
166 LitKind::ByteStr(ref s) => Constant::Binary(Lrc::clone(s)),
167 LitKind::Char(c) => Constant::Char(c),
168 LitKind::Int(n, _) => Constant::Int(n),
169 LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
170 ast::FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
171 ast::FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
173 LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() {
174 ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
175 ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
178 LitKind::Bool(b) => Constant::Bool(b),
179 LitKind::Err(s) => Constant::Err(s),
183 pub fn constant<'tcx>(
184 lcx: &LateContext<'tcx>,
185 typeck_results: &ty::TypeckResults<'tcx>,
187 ) -> Option<(Constant, bool)> {
188 let mut cx = ConstEvalLateContext {
191 param_env: lcx.param_env,
192 needed_resolution: false,
193 substs: lcx.tcx.intern_substs(&[]),
195 cx.expr(e).map(|cst| (cst, cx.needed_resolution))
198 pub fn constant_simple<'tcx>(
199 lcx: &LateContext<'tcx>,
200 typeck_results: &ty::TypeckResults<'tcx>,
202 ) -> Option<Constant> {
203 constant(lcx, typeck_results, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
206 /// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckResults`.
207 pub fn constant_context<'a, 'tcx>(
208 lcx: &'a LateContext<'tcx>,
209 typeck_results: &'a ty::TypeckResults<'tcx>,
210 ) -> ConstEvalLateContext<'a, 'tcx> {
211 ConstEvalLateContext {
214 param_env: lcx.param_env,
215 needed_resolution: false,
216 substs: lcx.tcx.intern_substs(&[]),
220 pub struct ConstEvalLateContext<'a, 'tcx> {
221 lcx: &'a LateContext<'tcx>,
222 typeck_results: &'a ty::TypeckResults<'tcx>,
223 param_env: ty::ParamEnv<'tcx>,
224 needed_resolution: bool,
225 substs: SubstsRef<'tcx>,
228 impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
229 /// Simple constant folding: Insert an expression, get a constant or none.
230 pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
232 ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.typeck_results.expr_ty(e)),
233 ExprKind::Block(ref block, _) => self.block(block),
234 ExprKind::Lit(ref lit) => Some(lit_to_constant(&lit.node, self.typeck_results.expr_ty_opt(e))),
235 ExprKind::Array(ref vec) => self.multi(vec).map(Constant::Vec),
236 ExprKind::Tup(ref tup) => self.multi(tup).map(Constant::Tuple),
237 ExprKind::Repeat(ref value, _) => {
238 let n = match self.typeck_results.expr_ty(e).kind() {
239 ty::Array(_, n) => n.try_eval_usize(self.lcx.tcx, self.lcx.param_env)?,
240 _ => span_bug!(e.span, "typeck error"),
242 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
244 ExprKind::Unary(op, ref operand) => self.expr(operand).and_then(|o| match op {
245 UnOp::Not => self.constant_not(&o, self.typeck_results.expr_ty(e)),
246 UnOp::Neg => self.constant_negate(&o, self.typeck_results.expr_ty(e)),
247 UnOp::Deref => Some(if let Constant::Ref(r) = o { *r } else { o }),
249 ExprKind::If(ref cond, ref then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
250 ExprKind::Binary(op, ref left, ref right) => self.binop(op, left, right),
251 ExprKind::Call(ref callee, ref args) => {
252 // We only handle a few const functions for now.
255 if let ExprKind::Path(qpath) = &callee.kind;
256 let res = self.typeck_results.qpath_res(qpath, callee.hir_id);
257 if let Some(def_id) = res.opt_def_id();
258 let def_path: Vec<_> = self.lcx.get_def_path(def_id).into_iter().map(Symbol::as_str).collect();
259 let def_path: Vec<&str> = def_path.iter().take(4).map(|s| &**s).collect();
260 if let ["core", "num", int_impl, "max_value"] = *def_path;
262 let value = match int_impl {
263 "<impl i8>" => i8::MAX as u128,
264 "<impl i16>" => i16::MAX as u128,
265 "<impl i32>" => i32::MAX as u128,
266 "<impl i64>" => i64::MAX as u128,
267 "<impl i128>" => i128::MAX as u128,
270 Some(Constant::Int(value))
277 ExprKind::Index(ref arr, ref index) => self.index(arr, index),
278 ExprKind::AddrOf(_, _, ref inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
279 // TODO: add other expressions.
284 #[allow(clippy::cast_possible_wrap)]
285 fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
286 use self::Constant::{Bool, Int};
288 Bool(b) => Some(Bool(!b)),
292 ty::Int(ity) => Some(Int(unsext(self.lcx.tcx, value as i128, ity))),
293 ty::Uint(ity) => Some(Int(clip(self.lcx.tcx, value, ity))),
301 fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
302 use self::Constant::{Int, F32, F64};
305 let ity = match *ty.kind() {
310 let value = sext(self.lcx.tcx, value, ity);
311 let value = value.checked_neg()?;
313 Some(Int(unsext(self.lcx.tcx, value, ity)))
315 F32(f) => Some(F32(-f)),
316 F64(f) => Some(F64(-f)),
321 /// Create `Some(Vec![..])` of all constants, unless there is any
322 /// non-constant part.
323 fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
324 vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
327 /// Lookup a possibly constant expression from a `ExprKind::Path`.
328 fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'tcx>) -> Option<Constant> {
329 let res = self.typeck_results.qpath_res(qpath, id);
331 Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
332 let substs = self.typeck_results.node_substs(id);
333 let substs = if self.substs.is_empty() {
336 substs.subst(self.lcx.tcx, self.substs)
344 ty::WithOptConstParam::unknown(def_id),
350 .map(|val| rustc_middle::ty::Const::from_value(self.lcx.tcx, val, ty))?;
351 let result = miri_to_const(&result);
352 if result.is_some() {
353 self.needed_resolution = true;
357 // FIXME: cover all usable cases.
362 fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
363 let lhs = self.expr(lhs);
364 let index = self.expr(index);
367 (Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec.get(index as usize) {
368 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
369 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
372 (Some(Constant::Vec(vec)), _) => {
373 if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
375 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
376 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
387 /// A block can only yield a constant if it only has one constant expression.
388 fn block(&mut self, block: &Block<'_>) -> Option<Constant> {
389 if block.stmts.is_empty() {
390 block.expr.as_ref().and_then(|b| self.expr(b))
396 fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
397 if let Some(Constant::Bool(b)) = self.expr(cond) {
401 otherwise.as_ref().and_then(|expr| self.expr(expr))
408 fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
409 let l = self.expr(left)?;
410 let r = self.expr(right);
412 (Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck_results.expr_ty_opt(left)?.kind() {
414 let l = sext(self.lcx.tcx, l, ity);
415 let r = sext(self.lcx.tcx, r, ity);
416 let zext = |n: i128| Constant::Int(unsext(self.lcx.tcx, n, ity));
418 BinOpKind::Add => l.checked_add(r).map(zext),
419 BinOpKind::Sub => l.checked_sub(r).map(zext),
420 BinOpKind::Mul => l.checked_mul(r).map(zext),
421 BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
422 BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
423 BinOpKind::Shr => l.checked_shr(r.try_into().expect("invalid shift")).map(zext),
424 BinOpKind::Shl => l.checked_shl(r.try_into().expect("invalid shift")).map(zext),
425 BinOpKind::BitXor => Some(zext(l ^ r)),
426 BinOpKind::BitOr => Some(zext(l | r)),
427 BinOpKind::BitAnd => Some(zext(l & r)),
428 BinOpKind::Eq => Some(Constant::Bool(l == r)),
429 BinOpKind::Ne => Some(Constant::Bool(l != r)),
430 BinOpKind::Lt => Some(Constant::Bool(l < r)),
431 BinOpKind::Le => Some(Constant::Bool(l <= r)),
432 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
433 BinOpKind::Gt => Some(Constant::Bool(l > r)),
437 ty::Uint(_) => match op.node {
438 BinOpKind::Add => l.checked_add(r).map(Constant::Int),
439 BinOpKind::Sub => l.checked_sub(r).map(Constant::Int),
440 BinOpKind::Mul => l.checked_mul(r).map(Constant::Int),
441 BinOpKind::Div => l.checked_div(r).map(Constant::Int),
442 BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
443 BinOpKind::Shr => l.checked_shr(r.try_into().expect("shift too large")).map(Constant::Int),
444 BinOpKind::Shl => l.checked_shl(r.try_into().expect("shift too large")).map(Constant::Int),
445 BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
446 BinOpKind::BitOr => Some(Constant::Int(l | r)),
447 BinOpKind::BitAnd => Some(Constant::Int(l & r)),
448 BinOpKind::Eq => Some(Constant::Bool(l == r)),
449 BinOpKind::Ne => Some(Constant::Bool(l != r)),
450 BinOpKind::Lt => Some(Constant::Bool(l < r)),
451 BinOpKind::Le => Some(Constant::Bool(l <= r)),
452 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
453 BinOpKind::Gt => Some(Constant::Bool(l > r)),
458 (Constant::F32(l), Some(Constant::F32(r))) => match op.node {
459 BinOpKind::Add => Some(Constant::F32(l + r)),
460 BinOpKind::Sub => Some(Constant::F32(l - r)),
461 BinOpKind::Mul => Some(Constant::F32(l * r)),
462 BinOpKind::Div => Some(Constant::F32(l / r)),
463 BinOpKind::Rem => Some(Constant::F32(l % r)),
464 BinOpKind::Eq => Some(Constant::Bool(l == r)),
465 BinOpKind::Ne => Some(Constant::Bool(l != r)),
466 BinOpKind::Lt => Some(Constant::Bool(l < r)),
467 BinOpKind::Le => Some(Constant::Bool(l <= r)),
468 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
469 BinOpKind::Gt => Some(Constant::Bool(l > r)),
472 (Constant::F64(l), Some(Constant::F64(r))) => match op.node {
473 BinOpKind::Add => Some(Constant::F64(l + r)),
474 BinOpKind::Sub => Some(Constant::F64(l - r)),
475 BinOpKind::Mul => Some(Constant::F64(l * r)),
476 BinOpKind::Div => Some(Constant::F64(l / r)),
477 BinOpKind::Rem => Some(Constant::F64(l % r)),
478 BinOpKind::Eq => Some(Constant::Bool(l == r)),
479 BinOpKind::Ne => Some(Constant::Bool(l != r)),
480 BinOpKind::Lt => Some(Constant::Bool(l < r)),
481 BinOpKind::Le => Some(Constant::Bool(l <= r)),
482 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
483 BinOpKind::Gt => Some(Constant::Bool(l > r)),
486 (l, r) => match (op.node, l, r) {
487 (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
488 (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
489 (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
492 (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
493 (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
494 (BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
501 pub fn miri_to_const(result: &ty::Const<'_>) -> Option<Constant> {
502 use rustc_middle::mir::interpret::ConstValue;
504 ty::ConstKind::Value(ConstValue::Scalar(Scalar::Int(int))) => {
505 match result.ty.kind() {
506 ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
507 ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.assert_bits(int.size()))),
508 ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
509 int.try_into().expect("invalid f32 bit representation"),
511 ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
512 int.try_into().expect("invalid f64 bit representation"),
514 ty::RawPtr(type_and_mut) => {
515 if let ty::Uint(_) = type_and_mut.ty.kind() {
516 return Some(Constant::RawPtr(int.assert_bits(int.size())));
520 // FIXME: implement other conversions.
524 ty::ConstKind::Value(ConstValue::Slice { data, start, end }) => match result.ty.kind() {
525 ty::Ref(_, tam, _) => match tam.kind() {
526 ty::Str => String::from_utf8(
527 data.inspect_with_uninit_and_ptr_outside_interpreter(start..end)
536 ty::ConstKind::Value(ConstValue::ByRef { alloc, offset: _ }) => match result.ty.kind() {
537 ty::Array(sub_type, len) => match sub_type.kind() {
538 ty::Float(FloatTy::F32) => match miri_to_const(len) {
539 Some(Constant::Int(len)) => alloc
540 .inspect_with_uninit_and_ptr_outside_interpreter(0..(4 * len as usize))
544 Some(Constant::F32(f32::from_le_bytes(
545 chunk.try_into().expect("this shouldn't happen"),
548 .collect::<Option<Vec<Constant>>>()
552 ty::Float(FloatTy::F64) => match miri_to_const(len) {
553 Some(Constant::Int(len)) => alloc
554 .inspect_with_uninit_and_ptr_outside_interpreter(0..(8 * len as usize))
558 Some(Constant::F64(f64::from_le_bytes(
559 chunk.try_into().expect("this shouldn't happen"),
562 .collect::<Option<Vec<Constant>>>()
566 // FIXME: implement other array type conversions.
571 // FIXME: implement other conversions.