1 #![allow(clippy::float_cmp)]
3 use crate::utils::{clip, higher, sext, unsext};
4 use if_chain::if_chain;
5 use rustc_ast::ast::{FloatTy, 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::ty::subst::{Subst, SubstsRef};
11 use rustc_middle::ty::{self, 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::convert::TryInto;
16 use std::hash::{Hash, Hasher};
18 /// A `LitKind`-like enum to fold constant `Expr`s into.
19 #[derive(Debug, Clone)]
21 /// A `String` (e.g., "abc").
23 /// A binary string (e.g., `b"abc"`).
25 /// A single `char` (e.g., `'a'`).
27 /// An integer's bit representation.
33 /// `true` or `false`.
35 /// An array of constants.
37 /// Also an array, but with only one constant, repeated N times.
38 Repeat(Box<Constant>, u64),
39 /// A tuple of constants.
43 /// A literal with syntax error.
47 impl PartialEq for Constant {
48 fn eq(&self, other: &Self) -> bool {
50 (&Self::Str(ref ls), &Self::Str(ref rs)) => ls == rs,
51 (&Self::Binary(ref l), &Self::Binary(ref r)) => l == r,
52 (&Self::Char(l), &Self::Char(r)) => l == r,
53 (&Self::Int(l), &Self::Int(r)) => l == r,
54 (&Self::F64(l), &Self::F64(r)) => {
55 // We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have
56 // `Fw32 == Fw64`, so don’t compare them.
57 // `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs.
58 l.to_bits() == r.to_bits()
60 (&Self::F32(l), &Self::F32(r)) => {
61 // We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have
62 // `Fw32 == Fw64`, so don’t compare them.
63 // `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs.
64 f64::from(l).to_bits() == f64::from(r).to_bits()
66 (&Self::Bool(l), &Self::Bool(r)) => l == r,
67 (&Self::Vec(ref l), &Self::Vec(ref r)) | (&Self::Tuple(ref l), &Self::Tuple(ref r)) => l == r,
68 (&Self::Repeat(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => ls == rs && lv == rv,
69 // TODO: are there inter-type equalities?
75 impl Hash for Constant {
76 fn hash<H>(&self, state: &mut H)
80 std::mem::discriminant(self).hash(state);
85 Self::Binary(ref b) => {
95 f64::from(f).to_bits().hash(state);
98 f.to_bits().hash(state);
103 Self::Vec(ref v) | Self::Tuple(ref v) => {
106 Self::Repeat(ref c, l) => {
113 Self::Err(ref s) => {
121 pub fn partial_cmp(tcx: TyCtxt<'_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option<Ordering> {
122 match (left, right) {
123 (&Self::Str(ref ls), &Self::Str(ref rs)) => Some(ls.cmp(rs)),
124 (&Self::Char(ref l), &Self::Char(ref r)) => Some(l.cmp(r)),
125 (&Self::Int(l), &Self::Int(r)) => {
126 if let ty::Int(int_ty) = cmp_type.kind {
127 Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty)))
132 (&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r),
133 (&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r),
134 (&Self::Bool(ref l), &Self::Bool(ref r)) => Some(l.cmp(r)),
135 (&Self::Tuple(ref l), &Self::Tuple(ref r)) | (&Self::Vec(ref l), &Self::Vec(ref r)) => l
138 .map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri))
139 .find(|r| r.map_or(true, |o| o != Ordering::Equal))
140 .unwrap_or_else(|| Some(l.len().cmp(&r.len()))),
141 (&Self::Repeat(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => {
142 match Self::partial_cmp(tcx, cmp_type, lv, rv) {
143 Some(Equal) => Some(ls.cmp(rs)),
147 // TODO: are there any useful inter-type orderings?
153 /// Parses a `LitKind` to a `Constant`.
154 pub fn lit_to_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
156 LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
157 LitKind::Byte(b) => Constant::Int(u128::from(b)),
158 LitKind::ByteStr(ref s) => Constant::Binary(Lrc::clone(s)),
159 LitKind::Char(c) => Constant::Char(c),
160 LitKind::Int(n, _) => Constant::Int(n),
161 LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
162 FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
163 FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
165 LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind {
166 ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
167 ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
170 LitKind::Bool(b) => Constant::Bool(b),
171 LitKind::Err(s) => Constant::Err(s),
175 pub fn constant<'c, 'cc>(
176 lcx: &LateContext<'c, 'cc>,
177 tables: &'c ty::TypeckTables<'cc>,
179 ) -> Option<(Constant, bool)> {
180 let mut cx = ConstEvalLateContext {
183 param_env: lcx.param_env,
184 needed_resolution: false,
185 substs: lcx.tcx.intern_substs(&[]),
187 cx.expr(e).map(|cst| (cst, cx.needed_resolution))
190 pub fn constant_simple<'c, 'cc>(
191 lcx: &LateContext<'c, 'cc>,
192 tables: &'c ty::TypeckTables<'cc>,
194 ) -> Option<Constant> {
195 constant(lcx, tables, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
198 /// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckTables`.
199 pub fn constant_context<'c, 'cc>(
200 lcx: &'c LateContext<'c, 'cc>,
201 tables: &'c ty::TypeckTables<'cc>,
202 ) -> ConstEvalLateContext<'c, 'cc> {
203 ConstEvalLateContext {
206 param_env: lcx.param_env,
207 needed_resolution: false,
208 substs: lcx.tcx.intern_substs(&[]),
212 pub struct ConstEvalLateContext<'a, 'tcx> {
213 lcx: &'a LateContext<'a, 'tcx>,
214 tables: &'a ty::TypeckTables<'tcx>,
215 param_env: ty::ParamEnv<'tcx>,
216 needed_resolution: bool,
217 substs: SubstsRef<'tcx>,
220 impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
221 /// Simple constant folding: Insert an expression, get a constant or none.
222 pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
223 if let Some((ref cond, ref then, otherwise)) = higher::if_block(&e) {
224 return self.ifthenelse(cond, then, otherwise);
227 ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.tables.expr_ty(e)),
228 ExprKind::Block(ref block, _) => self.block(block),
229 ExprKind::Lit(ref lit) => Some(lit_to_constant(&lit.node, self.tables.expr_ty_opt(e))),
230 ExprKind::Array(ref vec) => self.multi(vec).map(Constant::Vec),
231 ExprKind::Tup(ref tup) => self.multi(tup).map(Constant::Tuple),
232 ExprKind::Repeat(ref value, _) => {
233 let n = match self.tables.expr_ty(e).kind {
234 ty::Array(_, n) => n.try_eval_usize(self.lcx.tcx, self.lcx.param_env)?,
235 _ => span_bug!(e.span, "typeck error"),
237 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
239 ExprKind::Unary(op, ref operand) => self.expr(operand).and_then(|o| match op {
240 UnOp::UnNot => self.constant_not(&o, self.tables.expr_ty(e)),
241 UnOp::UnNeg => self.constant_negate(&o, self.tables.expr_ty(e)),
242 UnOp::UnDeref => Some(o),
244 ExprKind::Binary(op, ref left, ref right) => self.binop(op, left, right),
245 ExprKind::Call(ref callee, ref args) => {
246 // We only handle a few const functions for now.
249 if let ExprKind::Path(qpath) = &callee.kind;
250 let res = self.tables.qpath_res(qpath, callee.hir_id);
251 if let Some(def_id) = res.opt_def_id();
252 let def_path: Vec<_> = self.lcx.get_def_path(def_id).into_iter().map(Symbol::as_str).collect();
253 let def_path: Vec<&str> = def_path.iter().take(4).map(|s| &**s).collect();
254 if let ["core", "num", int_impl, "max_value"] = *def_path;
256 let value = match int_impl {
257 "<impl i8>" => i8::max_value() as u128,
258 "<impl i16>" => i16::max_value() as u128,
259 "<impl i32>" => i32::max_value() as u128,
260 "<impl i64>" => i64::max_value() as u128,
261 "<impl i128>" => i128::max_value() as u128,
264 Some(Constant::Int(value))
271 ExprKind::Index(ref arr, ref index) => self.index(arr, index),
272 // TODO: add other expressions.
277 #[allow(clippy::cast_possible_wrap)]
278 fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
279 use self::Constant::{Bool, Int};
281 Bool(b) => Some(Bool(!b)),
285 ty::Int(ity) => Some(Int(unsext(self.lcx.tcx, value as i128, ity))),
286 ty::Uint(ity) => Some(Int(clip(self.lcx.tcx, value, ity))),
294 fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
295 use self::Constant::{Int, F32, F64};
298 let ity = match ty.kind {
303 let value = sext(self.lcx.tcx, value, ity);
304 let value = value.checked_neg()?;
306 Some(Int(unsext(self.lcx.tcx, value, ity)))
308 F32(f) => Some(F32(-f)),
309 F64(f) => Some(F64(-f)),
314 /// Create `Some(Vec![..])` of all constants, unless there is any
315 /// non-constant part.
316 fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
317 vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
320 /// Lookup a possibly constant expression from a `ExprKind::Path`.
321 fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'cc>) -> Option<Constant> {
322 let res = self.tables.qpath_res(qpath, id);
324 Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
325 let substs = self.tables.node_substs(id);
326 let substs = if self.substs.is_empty() {
329 substs.subst(self.lcx.tcx, self.substs)
335 .const_eval_resolve(self.param_env, def_id, substs, None, None)
337 .map(|val| rustc_middle::ty::Const::from_value(self.lcx.tcx, val, ty))?;
338 let result = miri_to_const(&result);
339 if result.is_some() {
340 self.needed_resolution = true;
344 // FIXME: cover all usable cases.
349 fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
350 let lhs = self.expr(lhs);
351 let index = self.expr(index);
354 (Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec.get(index as usize) {
355 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
356 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
359 (Some(Constant::Vec(vec)), _) => {
360 if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
362 Some(Constant::F32(x)) => Some(Constant::F32(*x)),
363 Some(Constant::F64(x)) => Some(Constant::F64(*x)),
374 /// A block can only yield a constant if it only has one constant expression.
375 fn block(&mut self, block: &Block<'_>) -> Option<Constant> {
376 if block.stmts.is_empty() {
377 block.expr.as_ref().and_then(|b| self.expr(b))
383 fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
384 if let Some(Constant::Bool(b)) = self.expr(cond) {
388 otherwise.as_ref().and_then(|expr| self.expr(expr))
395 fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
396 let l = self.expr(left)?;
397 let r = self.expr(right);
399 (Constant::Int(l), Some(Constant::Int(r))) => match self.tables.expr_ty(left).kind {
401 let l = sext(self.lcx.tcx, l, ity);
402 let r = sext(self.lcx.tcx, r, ity);
403 let zext = |n: i128| Constant::Int(unsext(self.lcx.tcx, n, ity));
405 BinOpKind::Add => l.checked_add(r).map(zext),
406 BinOpKind::Sub => l.checked_sub(r).map(zext),
407 BinOpKind::Mul => l.checked_mul(r).map(zext),
408 BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
409 BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
410 BinOpKind::Shr => l.checked_shr(r.try_into().expect("invalid shift")).map(zext),
411 BinOpKind::Shl => l.checked_shl(r.try_into().expect("invalid shift")).map(zext),
412 BinOpKind::BitXor => Some(zext(l ^ r)),
413 BinOpKind::BitOr => Some(zext(l | r)),
414 BinOpKind::BitAnd => Some(zext(l & r)),
415 BinOpKind::Eq => Some(Constant::Bool(l == r)),
416 BinOpKind::Ne => Some(Constant::Bool(l != r)),
417 BinOpKind::Lt => Some(Constant::Bool(l < r)),
418 BinOpKind::Le => Some(Constant::Bool(l <= r)),
419 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
420 BinOpKind::Gt => Some(Constant::Bool(l > r)),
424 ty::Uint(_) => match op.node {
425 BinOpKind::Add => l.checked_add(r).map(Constant::Int),
426 BinOpKind::Sub => l.checked_sub(r).map(Constant::Int),
427 BinOpKind::Mul => l.checked_mul(r).map(Constant::Int),
428 BinOpKind::Div => l.checked_div(r).map(Constant::Int),
429 BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
430 BinOpKind::Shr => l.checked_shr(r.try_into().expect("shift too large")).map(Constant::Int),
431 BinOpKind::Shl => l.checked_shl(r.try_into().expect("shift too large")).map(Constant::Int),
432 BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
433 BinOpKind::BitOr => Some(Constant::Int(l | r)),
434 BinOpKind::BitAnd => Some(Constant::Int(l & r)),
435 BinOpKind::Eq => Some(Constant::Bool(l == r)),
436 BinOpKind::Ne => Some(Constant::Bool(l != r)),
437 BinOpKind::Lt => Some(Constant::Bool(l < r)),
438 BinOpKind::Le => Some(Constant::Bool(l <= r)),
439 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
440 BinOpKind::Gt => Some(Constant::Bool(l > r)),
445 (Constant::F32(l), Some(Constant::F32(r))) => match op.node {
446 BinOpKind::Add => Some(Constant::F32(l + r)),
447 BinOpKind::Sub => Some(Constant::F32(l - r)),
448 BinOpKind::Mul => Some(Constant::F32(l * r)),
449 BinOpKind::Div => Some(Constant::F32(l / r)),
450 BinOpKind::Rem => Some(Constant::F32(l % r)),
451 BinOpKind::Eq => Some(Constant::Bool(l == r)),
452 BinOpKind::Ne => Some(Constant::Bool(l != r)),
453 BinOpKind::Lt => Some(Constant::Bool(l < r)),
454 BinOpKind::Le => Some(Constant::Bool(l <= r)),
455 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
456 BinOpKind::Gt => Some(Constant::Bool(l > r)),
459 (Constant::F64(l), Some(Constant::F64(r))) => match op.node {
460 BinOpKind::Add => Some(Constant::F64(l + r)),
461 BinOpKind::Sub => Some(Constant::F64(l - r)),
462 BinOpKind::Mul => Some(Constant::F64(l * r)),
463 BinOpKind::Div => Some(Constant::F64(l / r)),
464 BinOpKind::Rem => Some(Constant::F64(l % r)),
465 BinOpKind::Eq => Some(Constant::Bool(l == r)),
466 BinOpKind::Ne => Some(Constant::Bool(l != r)),
467 BinOpKind::Lt => Some(Constant::Bool(l < r)),
468 BinOpKind::Le => Some(Constant::Bool(l <= r)),
469 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
470 BinOpKind::Gt => Some(Constant::Bool(l > r)),
473 (l, r) => match (op.node, l, r) {
474 (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
475 (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
476 (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
479 (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
480 (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
481 (BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
488 pub fn miri_to_const(result: &ty::Const<'_>) -> Option<Constant> {
489 use rustc_middle::mir::interpret::{ConstValue, Scalar};
491 ty::ConstKind::Value(ConstValue::Scalar(Scalar::Raw { data: d, .. })) => match result.ty.kind {
492 ty::Bool => Some(Constant::Bool(d == 1)),
493 ty::Uint(_) | ty::Int(_) => Some(Constant::Int(d)),
494 ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
495 d.try_into().expect("invalid f32 bit representation"),
497 ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
498 d.try_into().expect("invalid f64 bit representation"),
500 ty::RawPtr(type_and_mut) => {
501 if let ty::Uint(_) = type_and_mut.ty.kind {
502 return Some(Constant::RawPtr(d));
506 // FIXME: implement other conversions.
509 ty::ConstKind::Value(ConstValue::Slice { data, start, end }) => match result.ty.kind {
510 ty::Ref(_, tam, _) => match tam.kind {
511 ty::Str => String::from_utf8(
512 data.inspect_with_undef_and_ptr_outside_interpreter(start..end)
521 ty::ConstKind::Value(ConstValue::ByRef { alloc, offset: _ }) => match result.ty.kind {
522 ty::Array(sub_type, len) => match sub_type.kind {
523 ty::Float(FloatTy::F32) => match miri_to_const(len) {
524 Some(Constant::Int(len)) => alloc
525 .inspect_with_undef_and_ptr_outside_interpreter(0..(4 * len as usize))
529 Some(Constant::F32(f32::from_le_bytes(
530 chunk.try_into().expect("this shouldn't happen"),
533 .collect::<Option<Vec<Constant>>>()
537 ty::Float(FloatTy::F64) => match miri_to_const(len) {
538 Some(Constant::Int(len)) => alloc
539 .inspect_with_undef_and_ptr_outside_interpreter(0..(8 * len as usize))
543 Some(Constant::F64(f64::from_le_bytes(
544 chunk.try_into().expect("this shouldn't happen"),
547 .collect::<Option<Vec<Constant>>>()
551 // FIXME: implement other array type conversions.
556 // FIXME: implement other conversions.