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, ConstUsize, ConstIsize};
8 use std::cmp::Ordering::{self, Equal};
9 use std::cmp::PartialOrd;
10 use std::hash::{Hash, Hasher};
13 use syntax::ast::{FloatTy, LitIntType, LitKind, StrStyle, UintTy, IntTy, NodeId};
16 #[derive(Debug, Copy, Clone)]
23 impl From<FloatTy> for FloatWidth {
24 fn from(ty: FloatTy) -> FloatWidth {
26 FloatTy::F32 => FloatWidth::F32,
27 FloatTy::F64 => FloatWidth::F64,
32 /// A `LitKind`-like enum to fold constant `Expr`s into.
33 #[derive(Debug, Clone)]
36 Str(String, StrStyle),
37 /// a Binary String b"abc"
41 /// an integer, third argument is whether the value is negated
43 /// a float with given type
44 Float(String, FloatWidth),
47 /// an array of constants
49 /// also an array, but with only one constant, repeated N times
50 Repeat(Box<Constant>, usize),
51 /// a tuple of constants
56 /// Convert to `u64` if possible.
60 /// If the constant could not be converted to `u64` losslessly.
61 fn as_u64(&self) -> u64 {
62 if let Constant::Int(val) = *self {
63 val.to_u64().expect("negative constant can't be casted to `u64`")
65 panic!("Could not convert a `{:?}` to `u64`", self);
70 impl PartialEq for Constant {
71 fn eq(&self, other: &Constant) -> bool {
73 (&Constant::Str(ref ls, ref l_sty), &Constant::Str(ref rs, ref r_sty)) => ls == rs && l_sty == r_sty,
74 (&Constant::Binary(ref l), &Constant::Binary(ref r)) => l == r,
75 (&Constant::Char(l), &Constant::Char(r)) => l == r,
76 (&Constant::Int(l), &Constant::Int(r)) => {
77 l.is_negative() == r.is_negative() && l.to_u128_unchecked() == r.to_u128_unchecked()
79 (&Constant::Float(ref ls, _), &Constant::Float(ref rs, _)) => {
80 // we want `Fw32 == FwAny` and `FwAny == Fw64`, by transitivity we must have
81 // `Fw32 == Fw64` so don’t compare them
82 match (ls.parse::<f64>(), rs.parse::<f64>()) {
83 // mem::transmute is required to catch non-matching 0.0, -0.0, and NaNs
84 (Ok(l), Ok(r)) => unsafe { mem::transmute::<f64, u64>(l) == mem::transmute::<f64, u64>(r) },
88 (&Constant::Bool(l), &Constant::Bool(r)) => l == r,
89 (&Constant::Vec(ref l), &Constant::Vec(ref r)) => l == r,
90 (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => ls == rs && lv == rv,
91 (&Constant::Tuple(ref l), &Constant::Tuple(ref r)) => l == r,
92 _ => false, //TODO: Are there inter-type equalities?
97 impl Hash for Constant {
98 fn hash<H>(&self, state: &mut H)
102 Constant::Str(ref s, ref k) => {
106 Constant::Binary(ref b) => {
109 Constant::Char(c) => {
112 Constant::Int(i) => {
113 i.to_u128_unchecked().hash(state);
114 i.is_negative().hash(state);
116 Constant::Float(ref f, _) => {
117 // don’t use the width here because of PartialEq implementation
118 if let Ok(f) = f.parse::<f64>() {
119 unsafe { mem::transmute::<f64, u64>(f) }.hash(state);
122 Constant::Bool(b) => {
125 Constant::Vec(ref v) |
126 Constant::Tuple(ref v) => {
129 Constant::Repeat(ref c, l) => {
137 impl PartialOrd for Constant {
138 fn partial_cmp(&self, other: &Constant) -> Option<Ordering> {
139 match (self, other) {
140 (&Constant::Str(ref ls, ref l_sty), &Constant::Str(ref rs, ref r_sty)) => {
147 (&Constant::Char(ref l), &Constant::Char(ref r)) => Some(l.cmp(r)),
148 (&Constant::Int(l), &Constant::Int(r)) => Some(l.cmp(&r)),
149 (&Constant::Float(ref ls, _), &Constant::Float(ref rs, _)) => {
150 match (ls.parse::<f64>(), rs.parse::<f64>()) {
151 (Ok(ref l), Ok(ref r)) => {
152 match (l.partial_cmp(r), l.is_sign_positive() == r.is_sign_positive()) {
153 // Check for comparison of -0.0 and 0.0
154 (Some(Ordering::Equal), false) => None,
161 (&Constant::Bool(ref l), &Constant::Bool(ref r)) => Some(l.cmp(r)),
162 (&Constant::Tuple(ref l), &Constant::Tuple(ref r)) |
163 (&Constant::Vec(ref l), &Constant::Vec(ref r)) => l.partial_cmp(r),
164 (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => {
165 match lv.partial_cmp(rv) {
166 Some(Equal) => Some(ls.cmp(rs)),
170 _ => None, //TODO: Are there any useful inter-type orderings?
175 /// parse a `LitKind` to a `Constant`
176 #[allow(cast_possible_wrap)]
177 pub fn lit_to_constant(lit: &LitKind) -> Constant {
179 LitKind::Str(ref is, style) => Constant::Str(is.to_string(), style),
180 LitKind::Byte(b) => Constant::Int(ConstInt::U8(b)),
181 LitKind::ByteStr(ref s) => Constant::Binary(s.clone()),
182 LitKind::Char(c) => Constant::Char(c),
183 LitKind::Int(value, LitIntType::Unsuffixed) => Constant::Int(ConstInt::Infer(value)),
184 LitKind::Int(value, LitIntType::Unsigned(UintTy::U8)) => Constant::Int(ConstInt::U8(value as u8)),
185 LitKind::Int(value, LitIntType::Unsigned(UintTy::U16)) => Constant::Int(ConstInt::U16(value as u16)),
186 LitKind::Int(value, LitIntType::Unsigned(UintTy::U32)) => Constant::Int(ConstInt::U32(value as u32)),
187 LitKind::Int(value, LitIntType::Unsigned(UintTy::U64)) => Constant::Int(ConstInt::U64(value as u64)),
188 LitKind::Int(value, LitIntType::Unsigned(UintTy::U128)) => Constant::Int(ConstInt::U128(value as u128)),
189 LitKind::Int(value, LitIntType::Unsigned(UintTy::Us)) => {
190 Constant::Int(ConstInt::Usize(ConstUsize::Us32(value as u32)))
192 LitKind::Int(value, LitIntType::Signed(IntTy::I8)) => Constant::Int(ConstInt::I8(value as i8)),
193 LitKind::Int(value, LitIntType::Signed(IntTy::I16)) => Constant::Int(ConstInt::I16(value as i16)),
194 LitKind::Int(value, LitIntType::Signed(IntTy::I32)) => Constant::Int(ConstInt::I32(value as i32)),
195 LitKind::Int(value, LitIntType::Signed(IntTy::I64)) => Constant::Int(ConstInt::I64(value as i64)),
196 LitKind::Int(value, LitIntType::Signed(IntTy::I128)) => Constant::Int(ConstInt::I128(value as i128)),
197 LitKind::Int(value, LitIntType::Signed(IntTy::Is)) => {
198 Constant::Int(ConstInt::Isize(ConstIsize::Is32(value as i32)))
200 LitKind::Float(ref is, ty) => Constant::Float(is.to_string(), ty.into()),
201 LitKind::FloatUnsuffixed(ref is) => Constant::Float(is.to_string(), FloatWidth::Any),
202 LitKind::Bool(b) => Constant::Bool(b),
206 fn constant_not(o: Constant) -> Option<Constant> {
207 use self::Constant::*;
209 Bool(b) => Some(Bool(!b)),
210 Int(value) => (!value).ok().map(Int),
215 fn constant_negate(o: Constant) -> Option<Constant> {
216 use self::Constant::*;
218 Int(value) => (-value).ok().map(Int),
219 Float(is, ty) => Some(Float(neg_float_str(is), ty)),
224 fn neg_float_str(s: String) -> String {
225 if s.starts_with('-') {
232 pub fn constant(lcx: &LateContext, e: &Expr) -> Option<(Constant, bool)> {
233 let mut cx = ConstEvalLateContext {
235 needed_resolution: false,
237 cx.expr(e).map(|cst| (cst, cx.needed_resolution))
240 pub fn constant_simple(e: &Expr) -> Option<Constant> {
241 let mut cx = ConstEvalLateContext {
243 needed_resolution: false,
248 struct ConstEvalLateContext<'c, 'cc: 'c> {
249 lcx: Option<&'c LateContext<'c, 'cc>>,
250 needed_resolution: bool,
253 impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
254 /// simple constant folding: Insert an expression, get a constant or none.
255 fn expr(&mut self, e: &Expr) -> Option<Constant> {
257 ExprPath(ref qpath) => self.fetch_path(qpath, e.id),
258 ExprBlock(ref block) => self.block(block),
259 ExprIf(ref cond, ref then, ref otherwise) => self.ifthenelse(cond, then, otherwise),
260 ExprLit(ref lit) => Some(lit_to_constant(&lit.node)),
261 ExprArray(ref vec) => self.multi(vec).map(Constant::Vec),
262 ExprTup(ref tup) => self.multi(tup).map(Constant::Tuple),
263 ExprRepeat(ref value, number_id) => {
264 if let Some(lcx) = self.lcx {
265 self.binop_apply(value,
266 &lcx.tcx.map.body(number_id).value,
267 |v, n| Some(Constant::Repeat(Box::new(v), n.as_u64() as usize)))
272 ExprUnary(op, ref operand) => {
273 self.expr(operand).and_then(|o| {
275 UnNot => constant_not(o),
276 UnNeg => constant_negate(o),
281 ExprBinary(op, ref left, ref right) => self.binop(op, left, right),
282 // TODO: add other expressions
287 /// create `Some(Vec![..])` of all constants, unless there is any
288 /// non-constant part
289 fn multi(&mut self, vec: &[Expr]) -> Option<Vec<Constant>> {
291 .map(|elem| self.expr(elem))
292 .collect::<Option<_>>()
295 /// lookup a possibly constant expression from a ExprPath
296 fn fetch_path(&mut self, qpath: &QPath, id: NodeId) -> Option<Constant> {
297 if let Some(lcx) = self.lcx {
298 let def = lcx.tcx.tables().qpath_def(qpath, id);
301 Def::AssociatedConst(def_id) => {
302 let substs = Some(lcx.tcx
304 .node_id_item_substs(id)
305 .unwrap_or_else(|| lcx.tcx.intern_substs(&[])));
306 if let Some((const_expr, _ty)) = lookup_const_by_id(lcx.tcx, def_id, substs) {
307 let ret = self.expr(const_expr);
309 self.needed_resolution = true;
320 /// A block can only yield a constant if it only has one constant expression
321 fn block(&mut self, block: &Block) -> Option<Constant> {
322 if block.stmts.is_empty() {
323 block.expr.as_ref().and_then(|b| self.expr(b))
329 fn ifthenelse(&mut self, cond: &Expr, then: &Block, otherwise: &Option<P<Expr>>) -> Option<Constant> {
330 if let Some(Constant::Bool(b)) = self.expr(cond) {
334 otherwise.as_ref().and_then(|expr| self.expr(expr))
341 fn binop(&mut self, op: BinOp, left: &Expr, right: &Expr) -> Option<Constant> {
342 let l = if let Some(l) = self.expr(left) {
347 let r = self.expr(right);
348 match (op.node, l, r) {
349 (BiAdd, Constant::Int(l), Some(Constant::Int(r))) => (l + r).ok().map(Constant::Int),
350 (BiSub, Constant::Int(l), Some(Constant::Int(r))) => (l - r).ok().map(Constant::Int),
351 (BiMul, Constant::Int(l), Some(Constant::Int(r))) => (l * r).ok().map(Constant::Int),
352 (BiDiv, Constant::Int(l), Some(Constant::Int(r))) => (l / r).ok().map(Constant::Int),
353 (BiRem, Constant::Int(l), Some(Constant::Int(r))) => (l % r).ok().map(Constant::Int),
354 (BiAnd, Constant::Bool(false), _) => Some(Constant::Bool(false)),
355 (BiOr, Constant::Bool(true), _) => Some(Constant::Bool(true)),
356 (BiAnd, Constant::Bool(true), Some(r)) |
357 (BiOr, Constant::Bool(false), Some(r)) => Some(r),
358 (BiBitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
359 (BiBitXor, Constant::Int(l), Some(Constant::Int(r))) => (l ^ r).ok().map(Constant::Int),
360 (BiBitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
361 (BiBitAnd, Constant::Int(l), Some(Constant::Int(r))) => (l & r).ok().map(Constant::Int),
362 (BiBitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
363 (BiBitOr, Constant::Int(l), Some(Constant::Int(r))) => (l | r).ok().map(Constant::Int),
364 (BiShl, Constant::Int(l), Some(Constant::Int(r))) => (l << r).ok().map(Constant::Int),
365 (BiShr, Constant::Int(l), Some(Constant::Int(r))) => (l >> r).ok().map(Constant::Int),
366 (BiEq, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l == r)),
367 (BiNe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l != r)),
368 (BiLt, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l < r)),
369 (BiLe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l <= r)),
370 (BiGe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l >= r)),
371 (BiGt, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l > r)),
377 fn binop_apply<F>(&mut self, left: &Expr, right: &Expr, op: F) -> Option<Constant>
378 where F: Fn(Constant, Constant) -> Option<Constant>
380 if let (Some(lc), Some(rc)) = (self.expr(left), self.expr(right)) {