1 #![allow(cast_possible_truncation)]
3 use rustc::lint::LateContext;
4 use rustc::hir::def::Def;
5 use rustc_const_eval::lookup_const_by_id;
6 use rustc_const_math::ConstInt;
8 use rustc::ty::{self, Ty, TyCtxt};
9 use rustc::ty::subst::{Subst, Substs};
10 use std::cmp::Ordering::{self, Equal};
11 use std::cmp::PartialOrd;
12 use std::hash::{Hash, Hasher};
15 use syntax::ast::{FloatTy, LitKind, StrStyle};
17 use utils::const_to_u64;
19 #[derive(Debug, Copy, Clone)]
26 impl From<FloatTy> for FloatWidth {
27 fn from(ty: FloatTy) -> Self {
29 FloatTy::F32 => FloatWidth::F32,
30 FloatTy::F64 => FloatWidth::F64,
35 /// A `LitKind`-like enum to fold constant `Expr`s into.
36 #[derive(Debug, Clone)]
39 Str(String, StrStyle),
40 /// a Binary String b"abc"
44 /// an integer, third argument is whether the value is negated
46 /// a float with given type
47 Float(String, FloatWidth),
50 /// an array of constants
52 /// also an array, but with only one constant, repeated N times
53 Repeat(Box<Constant>, u64),
54 /// a tuple of constants
58 impl PartialEq for Constant {
59 fn eq(&self, other: &Self) -> bool {
61 (&Constant::Str(ref ls, ref l_sty), &Constant::Str(ref rs, ref r_sty)) => ls == rs && l_sty == r_sty,
62 (&Constant::Binary(ref l), &Constant::Binary(ref r)) => l == r,
63 (&Constant::Char(l), &Constant::Char(r)) => l == r,
64 (&Constant::Int(l), &Constant::Int(r)) => {
65 l.is_negative() == r.is_negative() && l.to_u128_unchecked() == r.to_u128_unchecked()
67 (&Constant::Float(ref ls, _), &Constant::Float(ref rs, _)) => {
68 // we want `Fw32 == FwAny` and `FwAny == Fw64`, by transitivity we must have
69 // `Fw32 == Fw64` so don’t compare them
70 match (ls.parse::<f64>(), rs.parse::<f64>()) {
71 // mem::transmute is required to catch non-matching 0.0, -0.0, and NaNs
72 (Ok(l), Ok(r)) => unsafe { mem::transmute::<f64, u64>(l) == mem::transmute::<f64, u64>(r) },
76 (&Constant::Bool(l), &Constant::Bool(r)) => l == r,
77 (&Constant::Vec(ref l), &Constant::Vec(ref r)) => l == r,
78 (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => ls == rs && lv == rv,
79 (&Constant::Tuple(ref l), &Constant::Tuple(ref r)) => l == r,
80 _ => false, // TODO: Are there inter-type equalities?
85 impl Hash for Constant {
86 fn hash<H>(&self, state: &mut H)
91 Constant::Str(ref s, ref k) => {
95 Constant::Binary(ref b) => {
98 Constant::Char(c) => {
101 Constant::Int(i) => {
102 i.to_u128_unchecked().hash(state);
103 i.is_negative().hash(state);
105 Constant::Float(ref f, _) => {
106 // don’t use the width here because of PartialEq implementation
107 if let Ok(f) = f.parse::<f64>() {
108 unsafe { mem::transmute::<f64, u64>(f) }.hash(state);
111 Constant::Bool(b) => {
114 Constant::Vec(ref v) | Constant::Tuple(ref v) => {
117 Constant::Repeat(ref c, l) => {
125 impl PartialOrd for Constant {
126 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
127 match (self, other) {
128 (&Constant::Str(ref ls, ref l_sty), &Constant::Str(ref rs, ref r_sty)) => if l_sty == r_sty {
133 (&Constant::Char(ref l), &Constant::Char(ref r)) => Some(l.cmp(r)),
134 (&Constant::Int(l), &Constant::Int(r)) => Some(l.cmp(&r)),
135 (&Constant::Float(ref ls, _), &Constant::Float(ref rs, _)) => {
136 match (ls.parse::<f64>(), rs.parse::<f64>()) {
137 (Ok(ref l), Ok(ref r)) => {
138 match (l.partial_cmp(r), l.is_sign_positive() == r.is_sign_positive()) {
139 // Check for comparison of -0.0 and 0.0
140 (Some(Ordering::Equal), false) => None,
147 (&Constant::Bool(ref l), &Constant::Bool(ref r)) => Some(l.cmp(r)),
148 (&Constant::Tuple(ref l), &Constant::Tuple(ref r)) | (&Constant::Vec(ref l), &Constant::Vec(ref r)) => {
151 (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => match lv.partial_cmp(rv) {
152 Some(Equal) => Some(ls.cmp(rs)),
155 _ => None, // TODO: Are there any useful inter-type orderings?
160 /// parse a `LitKind` to a `Constant`
161 #[allow(cast_possible_wrap)]
162 pub fn lit_to_constant<'a, 'tcx>(lit: &LitKind, tcx: TyCtxt<'a, 'tcx, 'tcx>, mut ty: Ty<'tcx>) -> Constant {
164 use syntax::ast::LitIntType::*;
165 use rustc::ty::util::IntTypeExt;
167 if let ty::TyAdt(adt, _) = ty.sty {
169 ty = adt.repr.discr_type().to_ty(tcx)
173 LitKind::Str(ref is, style) => Constant::Str(is.to_string(), style),
174 LitKind::Byte(b) => Constant::Int(ConstInt::U8(b)),
175 LitKind::ByteStr(ref s) => Constant::Binary(Rc::clone(s)),
176 LitKind::Char(c) => Constant::Char(c),
177 LitKind::Int(n, hint) => match (&ty.sty, hint) {
178 (&ty::TyInt(ity), _) | (_, Signed(ity)) => {
179 Constant::Int(ConstInt::new_signed_truncating(n as i128, ity, tcx.sess.target.isize_ty))
181 (&ty::TyUint(uty), _) | (_, Unsigned(uty)) => {
182 Constant::Int(ConstInt::new_unsigned_truncating(n as u128, uty, tcx.sess.target.usize_ty))
186 LitKind::Float(ref is, ty) => Constant::Float(is.to_string(), ty.into()),
187 LitKind::FloatUnsuffixed(ref is) => Constant::Float(is.to_string(), FloatWidth::Any),
188 LitKind::Bool(b) => Constant::Bool(b),
192 fn constant_not(o: &Constant) -> Option<Constant> {
193 use self::Constant::*;
195 Bool(b) => Some(Bool(!b)),
196 Int(value) => (!value).ok().map(Int),
201 fn constant_negate(o: Constant) -> Option<Constant> {
202 use self::Constant::*;
204 Int(value) => (-value).ok().map(Int),
205 Float(is, ty) => Some(Float(neg_float_str(&is), ty)),
210 fn neg_float_str(s: &str) -> String {
211 if s.starts_with('-') {
218 pub fn constant(lcx: &LateContext, e: &Expr) -> Option<(Constant, bool)> {
219 let mut cx = ConstEvalLateContext {
222 param_env: lcx.param_env,
223 needed_resolution: false,
224 substs: lcx.tcx.intern_substs(&[]),
226 cx.expr(e).map(|cst| (cst, cx.needed_resolution))
229 pub fn constant_simple(lcx: &LateContext, e: &Expr) -> Option<Constant> {
230 constant(lcx, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
233 struct ConstEvalLateContext<'a, 'tcx: 'a> {
234 tcx: TyCtxt<'a, 'tcx, 'tcx>,
235 tables: &'a ty::TypeckTables<'tcx>,
236 param_env: ty::ParamEnv<'tcx>,
237 needed_resolution: bool,
238 substs: &'tcx Substs<'tcx>,
241 impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
242 /// simple constant folding: Insert an expression, get a constant or none.
243 fn expr(&mut self, e: &Expr) -> Option<Constant> {
245 ExprPath(ref qpath) => self.fetch_path(qpath, e.hir_id),
246 ExprBlock(ref block) => self.block(block),
247 ExprIf(ref cond, ref then, ref otherwise) => self.ifthenelse(cond, then, otherwise),
248 ExprLit(ref lit) => Some(lit_to_constant(&lit.node, self.tcx, self.tables.expr_ty(e))),
249 ExprArray(ref vec) => self.multi(vec).map(Constant::Vec),
250 ExprTup(ref tup) => self.multi(tup).map(Constant::Tuple),
251 ExprRepeat(ref value, _) => {
252 let n = match self.tables.expr_ty(e).sty {
253 ty::TyArray(_, n) => const_to_u64(n),
254 _ => span_bug!(e.span, "typeck error"),
256 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
258 ExprUnary(op, ref operand) => self.expr(operand).and_then(|o| match op {
259 UnNot => constant_not(&o),
260 UnNeg => constant_negate(o),
263 ExprBinary(op, ref left, ref right) => self.binop(op, left, right),
264 // TODO: add other expressions
269 /// create `Some(Vec![..])` of all constants, unless there is any
270 /// non-constant part
271 fn multi(&mut self, vec: &[Expr]) -> Option<Vec<Constant>> {
273 .map(|elem| self.expr(elem))
274 .collect::<Option<_>>()
277 /// lookup a possibly constant expression from a ExprPath
278 fn fetch_path(&mut self, qpath: &QPath, id: HirId) -> Option<Constant> {
279 let def = self.tables.qpath_def(qpath, id);
281 Def::Const(def_id) | Def::AssociatedConst(def_id) => {
282 let substs = self.tables.node_substs(id);
283 let substs = if self.substs.is_empty() {
286 substs.subst(self.tcx, self.substs)
288 let param_env = self.param_env.and((def_id, substs));
289 if let Some((def_id, substs)) = lookup_const_by_id(self.tcx, param_env) {
292 tables: self.tcx.typeck_tables_of(def_id),
293 needed_resolution: false,
295 param_env: param_env.param_env,
297 let body = if let Some(id) = self.tcx.hir.as_local_node_id(def_id) {
298 self.tcx.mir_const_qualif(def_id);
299 self.tcx.hir.body(self.tcx.hir.body_owned_by(id))
301 self.tcx.extern_const_body(def_id).body
303 let ret = cx.expr(&body.value);
305 self.needed_resolution = true;
315 /// A block can only yield a constant if it only has one constant expression
316 fn block(&mut self, block: &Block) -> Option<Constant> {
317 if block.stmts.is_empty() {
318 block.expr.as_ref().and_then(|b| self.expr(b))
324 fn ifthenelse(&mut self, cond: &Expr, then: &P<Expr>, otherwise: &Option<P<Expr>>) -> Option<Constant> {
325 if let Some(Constant::Bool(b)) = self.expr(cond) {
329 otherwise.as_ref().and_then(|expr| self.expr(expr))
336 fn binop(&mut self, op: BinOp, left: &Expr, right: &Expr) -> Option<Constant> {
337 let l = if let Some(l) = self.expr(left) {
342 let r = self.expr(right);
343 match (op.node, l, r) {
344 (BiAdd, Constant::Int(l), Some(Constant::Int(r))) => (l + r).ok().map(Constant::Int),
345 (BiSub, Constant::Int(l), Some(Constant::Int(r))) => (l - r).ok().map(Constant::Int),
346 (BiMul, Constant::Int(l), Some(Constant::Int(r))) => (l * r).ok().map(Constant::Int),
347 (BiDiv, Constant::Int(l), Some(Constant::Int(r))) => (l / r).ok().map(Constant::Int),
348 (BiRem, Constant::Int(l), Some(Constant::Int(r))) => (l % r).ok().map(Constant::Int),
349 (BiAnd, Constant::Bool(false), _) => Some(Constant::Bool(false)),
350 (BiOr, Constant::Bool(true), _) => Some(Constant::Bool(true)),
351 (BiAnd, Constant::Bool(true), Some(r)) | (BiOr, Constant::Bool(false), Some(r)) => Some(r),
352 (BiBitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
353 (BiBitXor, Constant::Int(l), Some(Constant::Int(r))) => (l ^ r).ok().map(Constant::Int),
354 (BiBitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
355 (BiBitAnd, Constant::Int(l), Some(Constant::Int(r))) => (l & r).ok().map(Constant::Int),
356 (BiBitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
357 (BiBitOr, Constant::Int(l), Some(Constant::Int(r))) => (l | r).ok().map(Constant::Int),
358 (BiShl, Constant::Int(l), Some(Constant::Int(r))) => (l << r).ok().map(Constant::Int),
359 (BiShr, Constant::Int(l), Some(Constant::Int(r))) => (l >> r).ok().map(Constant::Int),
360 (BiEq, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l == r)),
361 (BiNe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l != r)),
362 (BiLt, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l < r)),
363 (BiLe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l <= r)),
364 (BiGe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l >= r)),
365 (BiGt, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l > r)),