rust-clippy/clippy_lints/src/consts.rs
Oliver Schneider 32a9394490
Rustup
2017-09-13 15:34:04 +02:00

369 lines
14 KiB
Rust
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#![allow(cast_possible_truncation)]
use rustc::lint::LateContext;
use rustc::hir::def::Def;
use rustc_const_eval::lookup_const_by_id;
use rustc_const_math::ConstInt;
use rustc::hir::*;
use rustc::ty::{self, Ty, TyCtxt};
use rustc::ty::subst::{Subst, Substs};
use std::cmp::Ordering::{self, Equal};
use std::cmp::PartialOrd;
use std::hash::{Hash, Hasher};
use std::mem;
use std::rc::Rc;
use syntax::ast::{FloatTy, LitKind, StrStyle};
use syntax::ptr::P;
use utils::const_to_u64;
#[derive(Debug, Copy, Clone)]
pub enum FloatWidth {
F32,
F64,
Any,
}
impl From<FloatTy> for FloatWidth {
fn from(ty: FloatTy) -> Self {
match ty {
FloatTy::F32 => FloatWidth::F32,
FloatTy::F64 => FloatWidth::F64,
}
}
}
/// A `LitKind`-like enum to fold constant `Expr`s into.
#[derive(Debug, Clone)]
pub enum Constant {
/// a String "abc"
Str(String, StrStyle),
/// a Binary String b"abc"
Binary(Rc<Vec<u8>>),
/// a single char 'a'
Char(char),
/// an integer, third argument is whether the value is negated
Int(ConstInt),
/// a float with given type
Float(String, FloatWidth),
/// true or false
Bool(bool),
/// an array of constants
Vec(Vec<Constant>),
/// also an array, but with only one constant, repeated N times
Repeat(Box<Constant>, u64),
/// a tuple of constants
Tuple(Vec<Constant>),
}
impl PartialEq for Constant {
fn eq(&self, other: &Self) -> bool {
match (self, other) {
(&Constant::Str(ref ls, ref l_sty), &Constant::Str(ref rs, ref r_sty)) => ls == rs && l_sty == r_sty,
(&Constant::Binary(ref l), &Constant::Binary(ref r)) => l == r,
(&Constant::Char(l), &Constant::Char(r)) => l == r,
(&Constant::Int(l), &Constant::Int(r)) => {
l.is_negative() == r.is_negative() && l.to_u128_unchecked() == r.to_u128_unchecked()
},
(&Constant::Float(ref ls, _), &Constant::Float(ref rs, _)) => {
// we want `Fw32 == FwAny` and `FwAny == Fw64`, by transitivity we must have
// `Fw32 == Fw64` so dont compare them
match (ls.parse::<f64>(), rs.parse::<f64>()) {
// mem::transmute is required to catch non-matching 0.0, -0.0, and NaNs
(Ok(l), Ok(r)) => unsafe { mem::transmute::<f64, u64>(l) == mem::transmute::<f64, u64>(r) },
_ => false,
}
},
(&Constant::Bool(l), &Constant::Bool(r)) => l == r,
(&Constant::Vec(ref l), &Constant::Vec(ref r)) => l == r,
(&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => ls == rs && lv == rv,
(&Constant::Tuple(ref l), &Constant::Tuple(ref r)) => l == r,
_ => false, // TODO: Are there inter-type equalities?
}
}
}
impl Hash for Constant {
fn hash<H>(&self, state: &mut H)
where
H: Hasher,
{
match *self {
Constant::Str(ref s, ref k) => {
s.hash(state);
k.hash(state);
},
Constant::Binary(ref b) => {
b.hash(state);
},
Constant::Char(c) => {
c.hash(state);
},
Constant::Int(i) => {
i.to_u128_unchecked().hash(state);
i.is_negative().hash(state);
},
Constant::Float(ref f, _) => {
// dont use the width here because of PartialEq implementation
if let Ok(f) = f.parse::<f64>() {
unsafe { mem::transmute::<f64, u64>(f) }.hash(state);
}
},
Constant::Bool(b) => {
b.hash(state);
},
Constant::Vec(ref v) | Constant::Tuple(ref v) => {
v.hash(state);
},
Constant::Repeat(ref c, l) => {
c.hash(state);
l.hash(state);
},
}
}
}
impl PartialOrd for Constant {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
match (self, other) {
(&Constant::Str(ref ls, ref l_sty), &Constant::Str(ref rs, ref r_sty)) => if l_sty == r_sty {
Some(ls.cmp(rs))
} else {
None
},
(&Constant::Char(ref l), &Constant::Char(ref r)) => Some(l.cmp(r)),
(&Constant::Int(l), &Constant::Int(r)) => Some(l.cmp(&r)),
(&Constant::Float(ref ls, _), &Constant::Float(ref rs, _)) => {
match (ls.parse::<f64>(), rs.parse::<f64>()) {
(Ok(ref l), Ok(ref r)) => {
match (l.partial_cmp(r), l.is_sign_positive() == r.is_sign_positive()) {
// Check for comparison of -0.0 and 0.0
(Some(Ordering::Equal), false) => None,
(x, _) => x,
}
},
_ => None,
}
},
(&Constant::Bool(ref l), &Constant::Bool(ref r)) => Some(l.cmp(r)),
(&Constant::Tuple(ref l), &Constant::Tuple(ref r)) | (&Constant::Vec(ref l), &Constant::Vec(ref r)) => {
l.partial_cmp(r)
},
(&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => match lv.partial_cmp(rv) {
Some(Equal) => Some(ls.cmp(rs)),
x => x,
},
_ => None, // TODO: Are there any useful inter-type orderings?
}
}
}
/// parse a `LitKind` to a `Constant`
#[allow(cast_possible_wrap)]
pub fn lit_to_constant<'a, 'tcx>(lit: &LitKind, tcx: TyCtxt<'a, 'tcx, 'tcx>, mut ty: Ty<'tcx>) -> Constant {
use syntax::ast::*;
use syntax::ast::LitIntType::*;
use rustc::ty::util::IntTypeExt;
if let ty::TyAdt(adt, _) = ty.sty {
if adt.is_enum() {
ty = adt.repr.discr_type().to_ty(tcx)
}
}
match *lit {
LitKind::Str(ref is, style) => Constant::Str(is.to_string(), style),
LitKind::Byte(b) => Constant::Int(ConstInt::U8(b)),
LitKind::ByteStr(ref s) => Constant::Binary(Rc::clone(s)),
LitKind::Char(c) => Constant::Char(c),
LitKind::Int(n, hint) => match (&ty.sty, hint) {
(&ty::TyInt(ity), _) | (_, Signed(ity)) => {
Constant::Int(ConstInt::new_signed_truncating(n as i128, ity, tcx.sess.target.isize_ty))
},
(&ty::TyUint(uty), _) | (_, Unsigned(uty)) => {
Constant::Int(ConstInt::new_unsigned_truncating(n as u128, uty, tcx.sess.target.usize_ty))
},
_ => bug!(),
},
LitKind::Float(ref is, ty) => Constant::Float(is.to_string(), ty.into()),
LitKind::FloatUnsuffixed(ref is) => Constant::Float(is.to_string(), FloatWidth::Any),
LitKind::Bool(b) => Constant::Bool(b),
}
}
fn constant_not(o: &Constant) -> Option<Constant> {
use self::Constant::*;
match *o {
Bool(b) => Some(Bool(!b)),
Int(value) => (!value).ok().map(Int),
_ => None,
}
}
fn constant_negate(o: Constant) -> Option<Constant> {
use self::Constant::*;
match o {
Int(value) => (-value).ok().map(Int),
Float(is, ty) => Some(Float(neg_float_str(&is), ty)),
_ => None,
}
}
fn neg_float_str(s: &str) -> String {
if s.starts_with('-') {
s[1..].to_owned()
} else {
format!("-{}", s)
}
}
pub fn constant(lcx: &LateContext, e: &Expr) -> Option<(Constant, bool)> {
let mut cx = ConstEvalLateContext {
tcx: lcx.tcx,
tables: lcx.tables,
param_env: lcx.param_env,
needed_resolution: false,
substs: lcx.tcx.intern_substs(&[]),
};
cx.expr(e).map(|cst| (cst, cx.needed_resolution))
}
pub fn constant_simple(lcx: &LateContext, e: &Expr) -> Option<Constant> {
constant(lcx, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
}
struct ConstEvalLateContext<'a, 'tcx: 'a> {
tcx: TyCtxt<'a, 'tcx, 'tcx>,
tables: &'a ty::TypeckTables<'tcx>,
param_env: ty::ParamEnv<'tcx>,
needed_resolution: bool,
substs: &'tcx Substs<'tcx>,
}
impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
/// simple constant folding: Insert an expression, get a constant or none.
fn expr(&mut self, e: &Expr) -> Option<Constant> {
match e.node {
ExprPath(ref qpath) => self.fetch_path(qpath, e.hir_id),
ExprBlock(ref block) => self.block(block),
ExprIf(ref cond, ref then, ref otherwise) => self.ifthenelse(cond, then, otherwise),
ExprLit(ref lit) => Some(lit_to_constant(&lit.node, self.tcx, self.tables.expr_ty(e))),
ExprArray(ref vec) => self.multi(vec).map(Constant::Vec),
ExprTup(ref tup) => self.multi(tup).map(Constant::Tuple),
ExprRepeat(ref value, _) => {
let n = match self.tables.expr_ty(e).sty {
ty::TyArray(_, n) => const_to_u64(n),
_ => span_bug!(e.span, "typeck error"),
};
self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
},
ExprUnary(op, ref operand) => self.expr(operand).and_then(|o| match op {
UnNot => constant_not(&o),
UnNeg => constant_negate(o),
UnDeref => Some(o),
}),
ExprBinary(op, ref left, ref right) => self.binop(op, left, right),
// TODO: add other expressions
_ => None,
}
}
/// create `Some(Vec![..])` of all constants, unless there is any
/// non-constant part
fn multi(&mut self, vec: &[Expr]) -> Option<Vec<Constant>> {
vec.iter()
.map(|elem| self.expr(elem))
.collect::<Option<_>>()
}
/// lookup a possibly constant expression from a ExprPath
fn fetch_path(&mut self, qpath: &QPath, id: HirId) -> Option<Constant> {
let def = self.tables.qpath_def(qpath, id);
match def {
Def::Const(def_id) | Def::AssociatedConst(def_id) => {
let substs = self.tables.node_substs(id);
let substs = if self.substs.is_empty() {
substs
} else {
substs.subst(self.tcx, self.substs)
};
let param_env = self.param_env.and((def_id, substs));
if let Some((def_id, substs)) = lookup_const_by_id(self.tcx, param_env) {
let mut cx = Self {
tcx: self.tcx,
tables: self.tcx.typeck_tables_of(def_id),
needed_resolution: false,
substs: substs,
param_env: param_env.param_env,
};
let body = if let Some(id) = self.tcx.hir.as_local_node_id(def_id) {
self.tcx.mir_const_qualif(def_id);
self.tcx.hir.body(self.tcx.hir.body_owned_by(id))
} else {
self.tcx.extern_const_body(def_id)
};
let ret = cx.expr(&body.value);
if ret.is_some() {
self.needed_resolution = true;
}
return ret;
}
},
_ => {},
}
None
}
/// A block can only yield a constant if it only has one constant expression
fn block(&mut self, block: &Block) -> Option<Constant> {
if block.stmts.is_empty() {
block.expr.as_ref().and_then(|b| self.expr(b))
} else {
None
}
}
fn ifthenelse(&mut self, cond: &Expr, then: &P<Expr>, otherwise: &Option<P<Expr>>) -> Option<Constant> {
if let Some(Constant::Bool(b)) = self.expr(cond) {
if b {
self.expr(&**then)
} else {
otherwise.as_ref().and_then(|expr| self.expr(expr))
}
} else {
None
}
}
fn binop(&mut self, op: BinOp, left: &Expr, right: &Expr) -> Option<Constant> {
let l = if let Some(l) = self.expr(left) {
l
} else {
return None;
};
let r = self.expr(right);
match (op.node, l, r) {
(BiAdd, Constant::Int(l), Some(Constant::Int(r))) => (l + r).ok().map(Constant::Int),
(BiSub, Constant::Int(l), Some(Constant::Int(r))) => (l - r).ok().map(Constant::Int),
(BiMul, Constant::Int(l), Some(Constant::Int(r))) => (l * r).ok().map(Constant::Int),
(BiDiv, Constant::Int(l), Some(Constant::Int(r))) => (l / r).ok().map(Constant::Int),
(BiRem, Constant::Int(l), Some(Constant::Int(r))) => (l % r).ok().map(Constant::Int),
(BiAnd, Constant::Bool(false), _) => Some(Constant::Bool(false)),
(BiOr, Constant::Bool(true), _) => Some(Constant::Bool(true)),
(BiAnd, Constant::Bool(true), Some(r)) | (BiOr, Constant::Bool(false), Some(r)) => Some(r),
(BiBitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
(BiBitXor, Constant::Int(l), Some(Constant::Int(r))) => (l ^ r).ok().map(Constant::Int),
(BiBitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
(BiBitAnd, Constant::Int(l), Some(Constant::Int(r))) => (l & r).ok().map(Constant::Int),
(BiBitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
(BiBitOr, Constant::Int(l), Some(Constant::Int(r))) => (l | r).ok().map(Constant::Int),
(BiShl, Constant::Int(l), Some(Constant::Int(r))) => (l << r).ok().map(Constant::Int),
(BiShr, Constant::Int(l), Some(Constant::Int(r))) => (l >> r).ok().map(Constant::Int),
(BiEq, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l == r)),
(BiNe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l != r)),
(BiLt, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l < r)),
(BiLe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l <= r)),
(BiGe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l >= r)),
(BiGt, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l > r)),
_ => None,
}
}
}