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, TyCtxt};
9 use std::cmp::Ordering::{self, Equal};
10 use std::cmp::PartialOrd;
11 use std::hash::{Hash, Hasher};
14 use syntax::ast::{FloatTy, LitKind, StrStyle, NodeId};
17 #[derive(Debug, Copy, Clone)]
24 impl From<FloatTy> for FloatWidth {
25 fn from(ty: FloatTy) -> FloatWidth {
27 FloatTy::F32 => FloatWidth::F32,
28 FloatTy::F64 => FloatWidth::F64,
33 /// A `LitKind`-like enum to fold constant `Expr`s into.
34 #[derive(Debug, Clone)]
37 Str(String, StrStyle),
38 /// a Binary String b"abc"
42 /// an integer, third argument is whether the value is negated
44 /// a float with given type
45 Float(String, FloatWidth),
48 /// an array of constants
50 /// also an array, but with only one constant, repeated N times
51 Repeat(Box<Constant>, usize),
52 /// a tuple of constants
56 impl PartialEq for Constant {
57 fn eq(&self, other: &Constant) -> bool {
59 (&Constant::Str(ref ls, ref l_sty), &Constant::Str(ref rs, ref r_sty)) => ls == rs && l_sty == r_sty,
60 (&Constant::Binary(ref l), &Constant::Binary(ref r)) => l == r,
61 (&Constant::Char(l), &Constant::Char(r)) => l == r,
62 (&Constant::Int(l), &Constant::Int(r)) => {
63 l.is_negative() == r.is_negative() && l.to_u128_unchecked() == r.to_u128_unchecked()
65 (&Constant::Float(ref ls, _), &Constant::Float(ref rs, _)) => {
66 // we want `Fw32 == FwAny` and `FwAny == Fw64`, by transitivity we must have
67 // `Fw32 == Fw64` so don’t compare them
68 match (ls.parse::<f64>(), rs.parse::<f64>()) {
69 // mem::transmute is required to catch non-matching 0.0, -0.0, and NaNs
70 (Ok(l), Ok(r)) => unsafe { mem::transmute::<f64, u64>(l) == mem::transmute::<f64, u64>(r) },
74 (&Constant::Bool(l), &Constant::Bool(r)) => l == r,
75 (&Constant::Vec(ref l), &Constant::Vec(ref r)) => l == r,
76 (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => ls == rs && lv == rv,
77 (&Constant::Tuple(ref l), &Constant::Tuple(ref r)) => l == r,
78 _ => false, //TODO: Are there inter-type equalities?
83 impl Hash for Constant {
84 fn hash<H>(&self, state: &mut H)
88 Constant::Str(ref s, ref k) => {
92 Constant::Binary(ref b) => {
95 Constant::Char(c) => {
99 i.to_u128_unchecked().hash(state);
100 i.is_negative().hash(state);
102 Constant::Float(ref f, _) => {
103 // don’t use the width here because of PartialEq implementation
104 if let Ok(f) = f.parse::<f64>() {
105 unsafe { mem::transmute::<f64, u64>(f) }.hash(state);
108 Constant::Bool(b) => {
111 Constant::Vec(ref v) |
112 Constant::Tuple(ref v) => {
115 Constant::Repeat(ref c, l) => {
123 impl PartialOrd for Constant {
124 fn partial_cmp(&self, other: &Constant) -> Option<Ordering> {
125 match (self, other) {
126 (&Constant::Str(ref ls, ref l_sty), &Constant::Str(ref rs, ref 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)) |
149 (&Constant::Vec(ref l), &Constant::Vec(ref r)) => l.partial_cmp(r),
150 (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => {
151 match lv.partial_cmp(rv) {
152 Some(Equal) => Some(ls.cmp(rs)),
156 _ => None, //TODO: Are there any useful inter-type orderings?
161 /// parse a `LitKind` to a `Constant`
162 #[allow(cast_possible_wrap)]
163 pub fn lit_to_constant<'a, 'tcx>(lit: &LitKind, tcx: TyCtxt<'a, 'tcx, 'tcx>, mut ty: ty::Ty<'tcx>) -> Constant {
165 use syntax::ast::LitIntType::*;
166 use rustc::ty::util::IntTypeExt;
168 if let ty::TyAdt(adt, _) = ty.sty {
170 ty = adt.repr.discr_type().to_ty(tcx)
174 LitKind::Str(ref is, style) => Constant::Str(is.to_string(), style),
175 LitKind::Byte(b) => Constant::Int(ConstInt::U8(b)),
176 LitKind::ByteStr(ref s) => Constant::Binary(s.clone()),
177 LitKind::Char(c) => Constant::Char(c),
178 LitKind::Int(n, hint) => {
179 match (&ty.sty, hint) {
180 (&ty::TyInt(ity), _) |
181 (_, Signed(ity)) => {
182 Constant::Int(ConstInt::new_signed_truncating(n as i128, ity, tcx.sess.target.int_type))
184 (&ty::TyUint(uty), _) |
185 (_, Unsigned(uty)) => {
186 Constant::Int(ConstInt::new_unsigned_truncating(n as u128, uty, tcx.sess.target.uint_type))
191 LitKind::Float(ref is, ty) => Constant::Float(is.to_string(), ty.into()),
192 LitKind::FloatUnsuffixed(ref is) => Constant::Float(is.to_string(), FloatWidth::Any),
193 LitKind::Bool(b) => Constant::Bool(b),
197 fn constant_not(o: &Constant) -> Option<Constant> {
198 use self::Constant::*;
200 Bool(b) => Some(Bool(!b)),
201 Int(value) => (!value).ok().map(Int),
206 fn constant_negate(o: Constant) -> Option<Constant> {
207 use self::Constant::*;
209 Int(value) => (-value).ok().map(Int),
210 Float(is, ty) => Some(Float(neg_float_str(&is), ty)),
215 fn neg_float_str(s: &str) -> String {
216 if s.starts_with('-') {
223 pub fn constant(lcx: &LateContext, e: &Expr) -> Option<(Constant, bool)> {
224 let mut cx = ConstEvalLateContext {
227 needed_resolution: false,
229 cx.expr(e).map(|cst| (cst, cx.needed_resolution))
232 pub fn constant_simple(lcx: &LateContext, e: &Expr) -> Option<Constant> {
233 constant(lcx, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
236 struct ConstEvalLateContext<'a, 'tcx: 'a> {
237 tcx: TyCtxt<'a, 'tcx, 'tcx>,
238 tables: &'a ty::TypeckTables<'tcx>,
239 needed_resolution: bool,
242 impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
243 /// simple constant folding: Insert an expression, get a constant or none.
244 fn expr(&mut self, e: &Expr) -> Option<Constant> {
246 ExprPath(ref qpath) => self.fetch_path(qpath, e.id),
247 ExprBlock(ref block) => self.block(block),
248 ExprIf(ref cond, ref then, ref otherwise) => self.ifthenelse(cond, then, otherwise),
249 ExprLit(ref lit) => Some(lit_to_constant(&lit.node, self.tcx, self.tables.expr_ty(e))),
250 ExprArray(ref vec) => self.multi(vec).map(Constant::Vec),
251 ExprTup(ref tup) => self.multi(tup).map(Constant::Tuple),
252 ExprRepeat(ref value, _) => {
253 let n = match self.tables.expr_ty(e).sty {
254 ty::TyArray(_, n) => n,
255 _ => span_bug!(e.span, "typeck error"),
257 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
259 ExprUnary(op, ref operand) => {
260 self.expr(operand).and_then(|o| match op {
261 UnNot => constant_not(&o),
262 UnNeg => constant_negate(o),
266 ExprBinary(op, ref left, ref right) => self.binop(op, left, right),
267 // TODO: add other expressions
272 /// create `Some(Vec![..])` of all constants, unless there is any
273 /// non-constant part
274 fn multi(&mut self, vec: &[Expr]) -> Option<Vec<Constant>> {
276 .map(|elem| self.expr(elem))
277 .collect::<Option<_>>()
280 /// lookup a possibly constant expression from a ExprPath
281 fn fetch_path(&mut self, qpath: &QPath, id: NodeId) -> Option<Constant> {
282 let def = self.tables.qpath_def(qpath, id);
285 Def::AssociatedConst(def_id) => {
286 let substs = self.tables
287 .node_id_item_substs(id)
288 .unwrap_or_else(|| self.tcx.intern_substs(&[]));
289 if let Some((const_expr, _)) = lookup_const_by_id(self.tcx, def_id, substs) {
290 let mut cx = ConstEvalLateContext {
292 tables: self.tcx.typeck_tables_of(const_expr),
293 needed_resolution: false,
295 let body = if let Some(id) = self.tcx.hir.as_local_node_id(def_id) {
296 self.tcx.mir_const_qualif(def_id);
297 self.tcx.hir.body(self.tcx.hir.body_owned_by(id))
299 self.tcx.sess.cstore.item_body(self.tcx, def_id)
301 let ret = cx.expr(&body.value);
303 self.needed_resolution = true;
313 /// A block can only yield a constant if it only has one constant expression
314 fn block(&mut self, block: &Block) -> Option<Constant> {
315 if block.stmts.is_empty() {
316 block.expr.as_ref().and_then(|b| self.expr(b))
322 fn ifthenelse(&mut self, cond: &Expr, then: &P<Expr>, otherwise: &Option<P<Expr>>) -> Option<Constant> {
323 if let Some(Constant::Bool(b)) = self.expr(cond) {
327 otherwise.as_ref().and_then(|expr| self.expr(expr))
334 fn binop(&mut self, op: BinOp, left: &Expr, right: &Expr) -> Option<Constant> {
335 let l = if let Some(l) = self.expr(left) {
340 let r = self.expr(right);
341 match (op.node, l, r) {
342 (BiAdd, Constant::Int(l), Some(Constant::Int(r))) => (l + r).ok().map(Constant::Int),
343 (BiSub, Constant::Int(l), Some(Constant::Int(r))) => (l - r).ok().map(Constant::Int),
344 (BiMul, Constant::Int(l), Some(Constant::Int(r))) => (l * r).ok().map(Constant::Int),
345 (BiDiv, Constant::Int(l), Some(Constant::Int(r))) => (l / r).ok().map(Constant::Int),
346 (BiRem, Constant::Int(l), Some(Constant::Int(r))) => (l % r).ok().map(Constant::Int),
347 (BiAnd, Constant::Bool(false), _) => Some(Constant::Bool(false)),
348 (BiOr, Constant::Bool(true), _) => Some(Constant::Bool(true)),
349 (BiAnd, Constant::Bool(true), Some(r)) |
350 (BiOr, Constant::Bool(false), Some(r)) => Some(r),
351 (BiBitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
352 (BiBitXor, Constant::Int(l), Some(Constant::Int(r))) => (l ^ r).ok().map(Constant::Int),
353 (BiBitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
354 (BiBitAnd, Constant::Int(l), Some(Constant::Int(r))) => (l & r).ok().map(Constant::Int),
355 (BiBitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
356 (BiBitOr, Constant::Int(l), Some(Constant::Int(r))) => (l | r).ok().map(Constant::Int),
357 (BiShl, Constant::Int(l), Some(Constant::Int(r))) => (l << r).ok().map(Constant::Int),
358 (BiShr, Constant::Int(l), Some(Constant::Int(r))) => (l >> r).ok().map(Constant::Int),
359 (BiEq, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l == r)),
360 (BiNe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l != r)),
361 (BiLt, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l < r)),
362 (BiLe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l <= r)),
363 (BiGe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l >= r)),
364 (BiGt, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l > r)),