1 #![allow(clippy::float_cmp)]
3 use crate::utils::{clip, higher, sext, unsext};
4 use if_chain::if_chain;
5 use rustc::ty::subst::{Subst, SubstsRef};
6 use rustc::ty::{self, Ty, TyCtxt};
7 use rustc::{bug, span_bug};
8 use rustc_data_structures::sync::Lrc;
9 use rustc_hir::def::{DefKind, Res};
11 use rustc_lint::LateContext;
12 use rustc_span::symbol::Symbol;
13 use std::cmp::Ordering::{self, Equal};
14 use std::convert::TryInto;
15 use std::hash::{Hash, Hasher};
16 use syntax::ast::{FloatTy, LitKind};
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 {
158 LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
159 LitKind::Byte(b) => Constant::Int(u128::from(b)),
160 LitKind::ByteStr(ref s) => Constant::Binary(Lrc::clone(s)),
161 LitKind::Char(c) => Constant::Char(c),
162 LitKind::Int(n, _) => Constant::Int(n),
163 LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
164 FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
165 FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
167 LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind {
168 ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
169 ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
172 LitKind::Bool(b) => Constant::Bool(b),
173 LitKind::Err(s) => Constant::Err(s),
177 pub fn constant<'c, 'cc>(
178 lcx: &LateContext<'c, 'cc>,
179 tables: &'c ty::TypeckTables<'cc>,
181 ) -> Option<(Constant, bool)> {
182 let mut cx = ConstEvalLateContext {
185 param_env: lcx.param_env,
186 needed_resolution: false,
187 substs: lcx.tcx.intern_substs(&[]),
189 cx.expr(e).map(|cst| (cst, cx.needed_resolution))
192 pub fn constant_simple<'c, 'cc>(
193 lcx: &LateContext<'c, 'cc>,
194 tables: &'c ty::TypeckTables<'cc>,
196 ) -> Option<Constant> {
197 constant(lcx, tables, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
200 /// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckTables`.
201 pub fn constant_context<'c, 'cc>(
202 lcx: &'c LateContext<'c, 'cc>,
203 tables: &'c ty::TypeckTables<'cc>,
204 ) -> ConstEvalLateContext<'c, 'cc> {
205 ConstEvalLateContext {
208 param_env: lcx.param_env,
209 needed_resolution: false,
210 substs: lcx.tcx.intern_substs(&[]),
214 pub struct ConstEvalLateContext<'a, 'tcx> {
215 lcx: &'a LateContext<'a, 'tcx>,
216 tables: &'a ty::TypeckTables<'tcx>,
217 param_env: ty::ParamEnv<'tcx>,
218 needed_resolution: bool,
219 substs: SubstsRef<'tcx>,
222 impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
223 /// Simple constant folding: Insert an expression, get a constant or none.
224 pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
225 if let Some((ref cond, ref then, otherwise)) = higher::if_block(&e) {
226 return self.ifthenelse(cond, then, otherwise);
229 ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.tables.expr_ty(e)),
230 ExprKind::Block(ref block, _) => self.block(block),
231 ExprKind::Lit(ref lit) => Some(lit_to_constant(&lit.node, self.tables.expr_ty_opt(e))),
232 ExprKind::Array(ref vec) => self.multi(vec).map(Constant::Vec),
233 ExprKind::Tup(ref tup) => self.multi(tup).map(Constant::Tuple),
234 ExprKind::Repeat(ref value, _) => {
235 let n = match self.tables.expr_ty(e).kind {
236 ty::Array(_, n) => n.eval_usize(self.lcx.tcx, self.lcx.param_env),
237 _ => span_bug!(e.span, "typeck error"),
239 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
241 ExprKind::Unary(op, ref operand) => self.expr(operand).and_then(|o| match op {
242 UnOp::UnNot => self.constant_not(&o, self.tables.expr_ty(e)),
243 UnOp::UnNeg => self.constant_negate(&o, self.tables.expr_ty(e)),
244 UnOp::UnDeref => Some(o),
246 ExprKind::Binary(op, ref left, ref right) => self.binop(op, left, right),
247 ExprKind::Call(ref callee, ref args) => {
248 // We only handle a few const functions for now.
251 if let ExprKind::Path(qpath) = &callee.kind;
252 let res = self.tables.qpath_res(qpath, callee.hir_id);
253 if let Some(def_id) = res.opt_def_id();
254 let def_path: Vec<_> = self.lcx.get_def_path(def_id).into_iter().map(Symbol::as_str).collect();
255 let def_path: Vec<&str> = def_path.iter().take(4).map(|s| &**s).collect();
256 if let ["core", "num", int_impl, "max_value"] = *def_path;
258 let value = match int_impl {
259 "<impl i8>" => i8::max_value() as u128,
260 "<impl i16>" => i16::max_value() as u128,
261 "<impl i32>" => i32::max_value() as u128,
262 "<impl i64>" => i64::max_value() as u128,
263 "<impl i128>" => i128::max_value() as u128,
266 Some(Constant::Int(value))
273 // TODO: add other expressions.
278 #[allow(clippy::cast_possible_wrap)]
279 fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
280 use self::Constant::*;
282 Bool(b) => Some(Bool(!b)),
286 ty::Int(ity) => Some(Int(unsext(self.lcx.tcx, value as i128, ity))),
287 ty::Uint(ity) => Some(Int(clip(self.lcx.tcx, value, ity))),
295 fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
296 use self::Constant::*;
299 let ity = match ty.kind {
304 let value = sext(self.lcx.tcx, value, ity);
305 let value = value.checked_neg()?;
307 Some(Int(unsext(self.lcx.tcx, value, ity)))
309 F32(f) => Some(F32(-f)),
310 F64(f) => Some(F64(-f)),
315 /// Create `Some(Vec![..])` of all constants, unless there is any
316 /// non-constant part.
317 fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
318 vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
321 /// Lookup a possibly constant expression from a `ExprKind::Path`.
322 fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'cc>) -> Option<Constant> {
323 let res = self.tables.qpath_res(qpath, id);
325 Res::Def(DefKind::Const, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
326 let substs = self.tables.node_substs(id);
327 let substs = if self.substs.is_empty() {
330 substs.subst(self.lcx.tcx, self.substs)
336 .const_eval_resolve(self.param_env, def_id, substs, None, None)
338 .map(|val| rustc::ty::Const::from_value(self.lcx.tcx, val, ty))?;
339 let result = miri_to_const(&result);
340 if result.is_some() {
341 self.needed_resolution = true;
345 // FIXME: cover all usable cases.
350 /// A block can only yield a constant if it only has one constant expression.
351 fn block(&mut self, block: &Block<'_>) -> Option<Constant> {
352 if block.stmts.is_empty() {
353 block.expr.as_ref().and_then(|b| self.expr(b))
359 fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
360 if let Some(Constant::Bool(b)) = self.expr(cond) {
364 otherwise.as_ref().and_then(|expr| self.expr(expr))
371 fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
372 let l = self.expr(left)?;
373 let r = self.expr(right);
375 (Constant::Int(l), Some(Constant::Int(r))) => match self.tables.expr_ty(left).kind {
377 let l = sext(self.lcx.tcx, l, ity);
378 let r = sext(self.lcx.tcx, r, ity);
379 let zext = |n: i128| Constant::Int(unsext(self.lcx.tcx, n, ity));
381 BinOpKind::Add => l.checked_add(r).map(zext),
382 BinOpKind::Sub => l.checked_sub(r).map(zext),
383 BinOpKind::Mul => l.checked_mul(r).map(zext),
384 BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
385 BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
386 BinOpKind::Shr => l.checked_shr(r.try_into().expect("invalid shift")).map(zext),
387 BinOpKind::Shl => l.checked_shl(r.try_into().expect("invalid shift")).map(zext),
388 BinOpKind::BitXor => Some(zext(l ^ r)),
389 BinOpKind::BitOr => Some(zext(l | r)),
390 BinOpKind::BitAnd => Some(zext(l & r)),
391 BinOpKind::Eq => Some(Constant::Bool(l == r)),
392 BinOpKind::Ne => Some(Constant::Bool(l != r)),
393 BinOpKind::Lt => Some(Constant::Bool(l < r)),
394 BinOpKind::Le => Some(Constant::Bool(l <= r)),
395 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
396 BinOpKind::Gt => Some(Constant::Bool(l > r)),
400 ty::Uint(_) => match op.node {
401 BinOpKind::Add => l.checked_add(r).map(Constant::Int),
402 BinOpKind::Sub => l.checked_sub(r).map(Constant::Int),
403 BinOpKind::Mul => l.checked_mul(r).map(Constant::Int),
404 BinOpKind::Div => l.checked_div(r).map(Constant::Int),
405 BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
406 BinOpKind::Shr => l.checked_shr(r.try_into().expect("shift too large")).map(Constant::Int),
407 BinOpKind::Shl => l.checked_shl(r.try_into().expect("shift too large")).map(Constant::Int),
408 BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
409 BinOpKind::BitOr => Some(Constant::Int(l | r)),
410 BinOpKind::BitAnd => Some(Constant::Int(l & r)),
411 BinOpKind::Eq => Some(Constant::Bool(l == r)),
412 BinOpKind::Ne => Some(Constant::Bool(l != r)),
413 BinOpKind::Lt => Some(Constant::Bool(l < r)),
414 BinOpKind::Le => Some(Constant::Bool(l <= r)),
415 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
416 BinOpKind::Gt => Some(Constant::Bool(l > r)),
421 (Constant::F32(l), Some(Constant::F32(r))) => match op.node {
422 BinOpKind::Add => Some(Constant::F32(l + r)),
423 BinOpKind::Sub => Some(Constant::F32(l - r)),
424 BinOpKind::Mul => Some(Constant::F32(l * r)),
425 BinOpKind::Div => Some(Constant::F32(l / r)),
426 BinOpKind::Rem => Some(Constant::F32(l % r)),
427 BinOpKind::Eq => Some(Constant::Bool(l == r)),
428 BinOpKind::Ne => Some(Constant::Bool(l != r)),
429 BinOpKind::Lt => Some(Constant::Bool(l < r)),
430 BinOpKind::Le => Some(Constant::Bool(l <= r)),
431 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
432 BinOpKind::Gt => Some(Constant::Bool(l > r)),
435 (Constant::F64(l), Some(Constant::F64(r))) => match op.node {
436 BinOpKind::Add => Some(Constant::F64(l + r)),
437 BinOpKind::Sub => Some(Constant::F64(l - r)),
438 BinOpKind::Mul => Some(Constant::F64(l * r)),
439 BinOpKind::Div => Some(Constant::F64(l / r)),
440 BinOpKind::Rem => Some(Constant::F64(l % r)),
441 BinOpKind::Eq => Some(Constant::Bool(l == r)),
442 BinOpKind::Ne => Some(Constant::Bool(l != r)),
443 BinOpKind::Lt => Some(Constant::Bool(l < r)),
444 BinOpKind::Le => Some(Constant::Bool(l <= r)),
445 BinOpKind::Ge => Some(Constant::Bool(l >= r)),
446 BinOpKind::Gt => Some(Constant::Bool(l > r)),
449 (l, r) => match (op.node, l, r) {
450 (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
451 (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
452 (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
455 (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
456 (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
457 (BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
464 pub fn miri_to_const(result: &ty::Const<'_>) -> Option<Constant> {
465 use rustc::mir::interpret::{ConstValue, Scalar};
467 ty::ConstKind::Value(ConstValue::Scalar(Scalar::Raw { data: d, .. })) => match result.ty.kind {
468 ty::Bool => Some(Constant::Bool(d == 1)),
469 ty::Uint(_) | ty::Int(_) => Some(Constant::Int(d)),
470 ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
471 d.try_into().expect("invalid f32 bit representation"),
473 ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
474 d.try_into().expect("invalid f64 bit representation"),
476 ty::RawPtr(type_and_mut) => {
477 if let ty::Uint(_) = type_and_mut.ty.kind {
478 return Some(Constant::RawPtr(d));
482 // FIXME: implement other conversions.
485 ty::ConstKind::Value(ConstValue::Slice { data, start, end }) => match result.ty.kind {
486 ty::Ref(_, tam, _) => match tam.kind {
487 ty::Str => String::from_utf8(
488 data.inspect_with_undef_and_ptr_outside_interpreter(start..end)
497 // FIXME: implement other conversions.