Merge pull request #184 from Manishearth/identity_op
Identity op now uses const folding, no longer follows const bindings
This commit is contained in:
Manish Goregaokar
commit
4f1fcd4d5b
393
src/consts.rs
Normal file
393
src/consts.rs
Normal file
@ -0,0 +1,393 @@
|
||||
use rustc::lint::Context;
|
||||
use rustc::middle::const_eval::lookup_const_by_id;
|
||||
use rustc::middle::def::PathResolution;
|
||||
use rustc::middle::def::Def::*;
|
||||
use syntax::ast::*;
|
||||
use syntax::ptr::P;
|
||||
use std::rc::Rc;
|
||||
use std::ops::Deref;
|
||||
use self::ConstantVariant::*;
|
||||
use self::FloatWidth::*;
|
||||
|
||||
#[derive(PartialEq, Eq, Debug, Copy, Clone)]
|
||||
pub enum FloatWidth {
|
||||
Fw32,
|
||||
Fw64,
|
||||
FwAny
|
||||
}
|
||||
|
||||
impl From<FloatTy> for FloatWidth {
|
||||
fn from(ty: FloatTy) -> FloatWidth {
|
||||
match ty {
|
||||
TyF32 => Fw32,
|
||||
TyF64 => Fw64,
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
#[derive(PartialEq, Eq, Debug, Clone)]
|
||||
pub struct Constant {
|
||||
pub constant: ConstantVariant,
|
||||
pub needed_resolution: bool
|
||||
}
|
||||
|
||||
impl Constant {
|
||||
pub fn new(variant: ConstantVariant) -> Constant {
|
||||
Constant { constant: variant, needed_resolution: false }
|
||||
}
|
||||
|
||||
pub fn new_resolved(variant: ConstantVariant) -> Constant {
|
||||
Constant { constant: variant, needed_resolution: true }
|
||||
}
|
||||
|
||||
// convert this constant to a f64, if possible
|
||||
pub fn as_float(&self) -> Option<f64> {
|
||||
match &self.constant {
|
||||
&ConstantByte(b) => Some(b as f64),
|
||||
&ConstantFloat(ref s, _) => s.parse().ok(),
|
||||
&ConstantInt(i, ty) => Some(if is_negative(ty) {
|
||||
-(i as f64) } else { i as f64 }),
|
||||
_ => None
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/// a Lit_-like enum to fold constant `Expr`s into
|
||||
#[derive(PartialEq, Eq, Debug, Clone)]
|
||||
pub enum ConstantVariant {
|
||||
/// a String "abc"
|
||||
ConstantStr(String, StrStyle),
|
||||
/// a Binary String b"abc"
|
||||
ConstantBinary(Rc<Vec<u8>>),
|
||||
/// a single byte b'a'
|
||||
ConstantByte(u8),
|
||||
/// a single char 'a'
|
||||
ConstantChar(char),
|
||||
/// an integer
|
||||
ConstantInt(u64, LitIntType),
|
||||
/// a float with given type
|
||||
ConstantFloat(String, FloatWidth),
|
||||
/// true or false
|
||||
ConstantBool(bool),
|
||||
/// an array of constants
|
||||
ConstantVec(Vec<Constant>),
|
||||
/// also an array, but with only one constant, repeated N times
|
||||
ConstantRepeat(Box<ConstantVariant>, usize),
|
||||
/// a tuple of constants
|
||||
ConstantTuple(Vec<Constant>),
|
||||
}
|
||||
|
||||
impl ConstantVariant {
|
||||
/// convert to u64 if possible
|
||||
///
|
||||
/// # panics
|
||||
///
|
||||
/// if the constant could not be converted to u64 losslessly
|
||||
fn as_u64(&self) -> u64 {
|
||||
if let &ConstantInt(val, _) = self {
|
||||
val // TODO we may want to check the sign if any
|
||||
} else {
|
||||
panic!("Could not convert a {:?} to u64");
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/// simple constant folding: Insert an expression, get a constant or none.
|
||||
pub fn constant(cx: &Context, e: &Expr) -> Option<Constant> {
|
||||
match &e.node {
|
||||
&ExprParen(ref inner) => constant(cx, inner),
|
||||
&ExprPath(_, _) => fetch_path(cx, e),
|
||||
&ExprBlock(ref block) => constant_block(cx, block),
|
||||
&ExprIf(ref cond, ref then, ref otherwise) =>
|
||||
constant_if(cx, &*cond, &*then, &*otherwise),
|
||||
&ExprLit(ref lit) => Some(lit_to_constant(&lit.node)),
|
||||
&ExprVec(ref vec) => constant_vec(cx, &vec[..]),
|
||||
&ExprTup(ref tup) => constant_tup(cx, &tup[..]),
|
||||
&ExprRepeat(ref value, ref number) =>
|
||||
constant_binop_apply(cx, value, number,|v, n|
|
||||
Some(ConstantRepeat(Box::new(v), n.as_u64() as usize))),
|
||||
&ExprUnary(op, ref operand) => constant(cx, operand).and_then(
|
||||
|o| match op {
|
||||
UnNot =>
|
||||
if let ConstantBool(b) = o.constant {
|
||||
Some(Constant{
|
||||
needed_resolution: o.needed_resolution,
|
||||
constant: ConstantBool(!b),
|
||||
})
|
||||
} else { None },
|
||||
UnNeg => constant_negate(o),
|
||||
UnUniq | UnDeref => Some(o),
|
||||
}),
|
||||
&ExprBinary(op, ref left, ref right) =>
|
||||
constant_binop(cx, op, left, right),
|
||||
//TODO: add other expressions
|
||||
_ => None,
|
||||
}
|
||||
}
|
||||
|
||||
fn lit_to_constant(lit: &Lit_) -> Constant {
|
||||
match lit {
|
||||
&LitStr(ref is, style) =>
|
||||
Constant::new(ConstantStr(is.to_string(), style)),
|
||||
&LitBinary(ref blob) => Constant::new(ConstantBinary(blob.clone())),
|
||||
&LitByte(b) => Constant::new(ConstantByte(b)),
|
||||
&LitChar(c) => Constant::new(ConstantChar(c)),
|
||||
&LitInt(value, ty) => Constant::new(ConstantInt(value, ty)),
|
||||
&LitFloat(ref is, ty) => {
|
||||
Constant::new(ConstantFloat(is.to_string(), ty.into()))
|
||||
},
|
||||
&LitFloatUnsuffixed(ref is) => {
|
||||
Constant::new(ConstantFloat(is.to_string(), FwAny))
|
||||
},
|
||||
&LitBool(b) => Constant::new(ConstantBool(b)),
|
||||
}
|
||||
}
|
||||
|
||||
/// create `Some(ConstantVec(..))` of all constants, unless there is any
|
||||
/// non-constant part
|
||||
fn constant_vec<E: Deref<Target=Expr> + Sized>(cx: &Context, vec: &[E]) -> Option<Constant> {
|
||||
let mut parts = Vec::new();
|
||||
let mut resolved = false;
|
||||
for opt_part in vec {
|
||||
match constant(cx, opt_part) {
|
||||
Some(p) => {
|
||||
resolved |= (&p).needed_resolution;
|
||||
parts.push(p)
|
||||
},
|
||||
None => { return None; },
|
||||
}
|
||||
}
|
||||
Some(Constant {
|
||||
constant: ConstantVec(parts),
|
||||
needed_resolution: resolved
|
||||
})
|
||||
}
|
||||
|
||||
fn constant_tup<E: Deref<Target=Expr> + Sized>(cx: &Context, tup: &[E]) -> Option<Constant> {
|
||||
let mut parts = Vec::new();
|
||||
let mut resolved = false;
|
||||
for opt_part in tup {
|
||||
match constant(cx, opt_part) {
|
||||
Some(p) => {
|
||||
resolved |= (&p).needed_resolution;
|
||||
parts.push(p)
|
||||
},
|
||||
None => { return None; },
|
||||
}
|
||||
}
|
||||
Some(Constant {
|
||||
constant: ConstantTuple(parts),
|
||||
needed_resolution: resolved
|
||||
})
|
||||
}
|
||||
|
||||
/// lookup a possibly constant expression from a ExprPath
|
||||
fn fetch_path(cx: &Context, e: &Expr) -> Option<Constant> {
|
||||
if let Some(&PathResolution { base_def: DefConst(id), ..}) =
|
||||
cx.tcx.def_map.borrow().get(&e.id) {
|
||||
lookup_const_by_id(cx.tcx, id, None).and_then(
|
||||
|l| constant(cx, l).map(|c| Constant::new_resolved(c.constant)))
|
||||
} else { None }
|
||||
}
|
||||
|
||||
/// A block can only yield a constant if it only has one constant expression
|
||||
fn constant_block(cx: &Context, block: &Block) -> Option<Constant> {
|
||||
if block.stmts.is_empty() {
|
||||
block.expr.as_ref().and_then(|b| constant(cx, &*b))
|
||||
} else { None }
|
||||
}
|
||||
|
||||
fn constant_if(cx: &Context, cond: &Expr, then: &Block, otherwise:
|
||||
&Option<P<Expr>>) -> Option<Constant> {
|
||||
if let Some(Constant{ constant: ConstantBool(b), needed_resolution: res }) =
|
||||
constant(cx, cond) {
|
||||
if b {
|
||||
constant_block(cx, then)
|
||||
} else {
|
||||
otherwise.as_ref().and_then(|expr| constant(cx, &*expr))
|
||||
}.map(|part|
|
||||
Constant {
|
||||
constant: part.constant,
|
||||
needed_resolution: res || part.needed_resolution,
|
||||
})
|
||||
} else { None }
|
||||
}
|
||||
|
||||
fn constant_negate(o: Constant) -> Option<Constant> {
|
||||
Some(Constant{
|
||||
needed_resolution: o.needed_resolution,
|
||||
constant: match o.constant {
|
||||
ConstantInt(value, ty) =>
|
||||
ConstantInt(value, match ty {
|
||||
SignedIntLit(ity, sign) =>
|
||||
SignedIntLit(ity, neg_sign(sign)),
|
||||
UnsuffixedIntLit(sign) => UnsuffixedIntLit(neg_sign(sign)),
|
||||
_ => { return None; },
|
||||
}),
|
||||
ConstantFloat(is, ty) =>
|
||||
ConstantFloat(neg_float_str(is), ty),
|
||||
_ => { return None; },
|
||||
}
|
||||
})
|
||||
}
|
||||
|
||||
fn neg_sign(s: Sign) -> Sign {
|
||||
match s {
|
||||
Sign::Plus => Sign::Minus,
|
||||
Sign::Minus => Sign::Plus,
|
||||
}
|
||||
}
|
||||
|
||||
fn neg_float_str(s: String) -> String {
|
||||
if s.starts_with('-') {
|
||||
s[1..].to_owned()
|
||||
} else {
|
||||
format!("-{}", &*s)
|
||||
}
|
||||
}
|
||||
|
||||
/// is the given LitIntType negative?
|
||||
///
|
||||
/// Examples
|
||||
///
|
||||
/// ```
|
||||
/// assert!(is_negative(UnsuffixedIntLit(Minus)));
|
||||
/// ```
|
||||
pub fn is_negative(ty: LitIntType) -> bool {
|
||||
match ty {
|
||||
SignedIntLit(_, sign) | UnsuffixedIntLit(sign) => sign == Minus,
|
||||
UnsignedIntLit(_) => false,
|
||||
}
|
||||
}
|
||||
|
||||
fn unify_int_type(l: LitIntType, r: LitIntType, s: Sign) -> Option<LitIntType> {
|
||||
match (l, r) {
|
||||
(SignedIntLit(lty, _), SignedIntLit(rty, _)) => if lty == rty {
|
||||
Some(SignedIntLit(lty, s)) } else { None },
|
||||
(UnsignedIntLit(lty), UnsignedIntLit(rty)) =>
|
||||
if s == Plus && lty == rty {
|
||||
Some(UnsignedIntLit(lty))
|
||||
} else { None },
|
||||
(UnsuffixedIntLit(_), UnsuffixedIntLit(_)) => Some(UnsuffixedIntLit(s)),
|
||||
(SignedIntLit(lty, _), UnsuffixedIntLit(_)) => Some(SignedIntLit(lty, s)),
|
||||
(UnsignedIntLit(lty), UnsuffixedIntLit(rs)) => if rs == Plus {
|
||||
Some(UnsignedIntLit(lty)) } else { None },
|
||||
(UnsuffixedIntLit(_), SignedIntLit(rty, _)) => Some(SignedIntLit(rty, s)),
|
||||
(UnsuffixedIntLit(ls), UnsignedIntLit(rty)) => if ls == Plus {
|
||||
Some(UnsignedIntLit(rty)) } else { None },
|
||||
_ => None,
|
||||
}
|
||||
}
|
||||
|
||||
fn constant_binop(cx: &Context, op: BinOp, left: &Expr, right: &Expr)
|
||||
-> Option<Constant> {
|
||||
match op.node {
|
||||
BiAdd => constant_binop_apply(cx, left, right, |l, r|
|
||||
match (l, r) {
|
||||
(ConstantByte(l8), ConstantByte(r8)) =>
|
||||
l8.checked_add(r8).map(ConstantByte),
|
||||
(ConstantInt(l64, lty), ConstantInt(r64, rty)) => {
|
||||
let (ln, rn) = (is_negative(lty), is_negative(rty));
|
||||
if ln == rn {
|
||||
unify_int_type(lty, rty, if ln { Minus } else { Plus })
|
||||
.and_then(|ty| l64.checked_add(r64).map(
|
||||
|v| ConstantInt(v, ty)))
|
||||
} else {
|
||||
if ln {
|
||||
add_neg_int(r64, rty, l64, lty)
|
||||
} else {
|
||||
add_neg_int(l64, lty, r64, rty)
|
||||
}
|
||||
}
|
||||
},
|
||||
// TODO: float
|
||||
_ => None
|
||||
}),
|
||||
BiSub => constant_binop_apply(cx, left, right, |l, r|
|
||||
match (l, r) {
|
||||
(ConstantByte(l8), ConstantByte(r8)) => if r8 > l8 {
|
||||
None } else { Some(ConstantByte(l8 - r8)) },
|
||||
(ConstantInt(l64, lty), ConstantInt(r64, rty)) => {
|
||||
let (ln, rn) = (is_negative(lty), is_negative(rty));
|
||||
match (ln, rn) {
|
||||
(false, false) => sub_int(l64, lty, r64, rty, r64 > l64),
|
||||
(true, true) => sub_int(l64, lty, r64, rty, l64 > r64),
|
||||
(true, false) => unify_int_type(lty, rty, Minus)
|
||||
.and_then(|ty| l64.checked_add(r64).map(
|
||||
|v| ConstantInt(v, ty))),
|
||||
(false, true) => unify_int_type(lty, rty, Plus)
|
||||
.and_then(|ty| l64.checked_add(r64).map(
|
||||
|v| ConstantInt(v, ty))),
|
||||
}
|
||||
},
|
||||
_ => None,
|
||||
}),
|
||||
//BiMul,
|
||||
//BiDiv,
|
||||
//BiRem,
|
||||
BiAnd => constant_short_circuit(cx, left, right, false),
|
||||
BiOr => constant_short_circuit(cx, left, right, true),
|
||||
//BiBitXor,
|
||||
//BiBitAnd,
|
||||
//BiBitOr,
|
||||
//BiShl,
|
||||
//BiShr,
|
||||
//BiEq,
|
||||
//BiLt,
|
||||
//BiLe,
|
||||
//BiNe,
|
||||
//BiGe,
|
||||
//BiGt,
|
||||
_ => None,
|
||||
}
|
||||
}
|
||||
|
||||
fn add_neg_int(pos: u64, pty: LitIntType, neg: u64, nty: LitIntType) ->
|
||||
Option<ConstantVariant> {
|
||||
if neg > pos {
|
||||
unify_int_type(nty, pty, Minus).map(|ty| ConstantInt(neg - pos, ty))
|
||||
} else {
|
||||
unify_int_type(nty, pty, Plus).map(|ty| ConstantInt(pos - neg, ty))
|
||||
}
|
||||
}
|
||||
|
||||
fn sub_int(l: u64, lty: LitIntType, r: u64, rty: LitIntType, neg: bool) ->
|
||||
Option<ConstantVariant> {
|
||||
unify_int_type(lty, rty, if neg { Minus } else { Plus }).and_then(
|
||||
|ty| l.checked_sub(r).map(|v| ConstantInt(v, ty)))
|
||||
}
|
||||
|
||||
fn constant_binop_apply<F>(cx: &Context, left: &Expr, right: &Expr, op: F)
|
||||
-> Option<Constant>
|
||||
where F: Fn(ConstantVariant, ConstantVariant) -> Option<ConstantVariant> {
|
||||
if let (Some(Constant { constant: lc, needed_resolution: ln }),
|
||||
Some(Constant { constant: rc, needed_resolution: rn })) =
|
||||
(constant(cx, left), constant(cx, right)) {
|
||||
op(lc, rc).map(|c|
|
||||
Constant {
|
||||
needed_resolution: ln || rn,
|
||||
constant: c,
|
||||
})
|
||||
} else { None }
|
||||
}
|
||||
|
||||
fn constant_short_circuit(cx: &Context, left: &Expr, right: &Expr, b: bool) ->
|
||||
Option<Constant> {
|
||||
constant(cx, left).and_then(|left|
|
||||
if let &ConstantBool(lbool) = &left.constant {
|
||||
if lbool == b {
|
||||
Some(left)
|
||||
} else {
|
||||
constant(cx, right).and_then(|right|
|
||||
if let ConstantBool(_) = right.constant {
|
||||
Some(Constant {
|
||||
constant: right.constant,
|
||||
needed_resolution: left.needed_resolution ||
|
||||
right.needed_resolution,
|
||||
})
|
||||
} else { None }
|
||||
)
|
||||
}
|
||||
} else { None }
|
||||
)
|
||||
}
|
||||
@ -4,6 +4,8 @@ use rustc::middle::def::*;
|
||||
use syntax::ast::*;
|
||||
use syntax::codemap::Span;
|
||||
|
||||
use consts::{constant, Constant, is_negative};
|
||||
use consts::ConstantVariant::ConstantInt;
|
||||
use utils::{span_lint, snippet};
|
||||
|
||||
declare_lint! { pub IDENTITY_OP, Warn,
|
||||
@ -44,35 +46,19 @@ impl LintPass for IdentityOp {
|
||||
|
||||
|
||||
fn check(cx: &Context, e: &Expr, m: i8, span: Span, arg: Span) {
|
||||
if have_lit(cx, e, m) {
|
||||
span_lint(cx, IDENTITY_OP, span, &format!(
|
||||
"the operation is ineffective. Consider reducing it to `{}`",
|
||||
snippet(cx, arg, "..")));
|
||||
}
|
||||
}
|
||||
|
||||
fn have_lit(cx: &Context, e : &Expr, m: i8) -> bool {
|
||||
match &e.node {
|
||||
&ExprUnary(UnNeg, ref litexp) => have_lit(cx, litexp, -m),
|
||||
&ExprLit(ref lit) => {
|
||||
match (&lit.node, m) {
|
||||
(&LitInt(0, _), 0) => true,
|
||||
(&LitInt(1, SignedIntLit(_, Plus)), 1) => true,
|
||||
(&LitInt(1, UnsuffixedIntLit(Plus)), 1) => true,
|
||||
(&LitInt(1, SignedIntLit(_, Minus)), -1) => true,
|
||||
(&LitInt(1, UnsuffixedIntLit(Minus)), -1) => true,
|
||||
_ => false
|
||||
}
|
||||
},
|
||||
&ExprParen(ref p) => have_lit(cx, p, m),
|
||||
&ExprPath(_, _) => {
|
||||
match cx.tcx.def_map.borrow().get(&e.id) {
|
||||
Some(&PathResolution { base_def: DefConst(id), ..}) =>
|
||||
lookup_const_by_id(cx.tcx, id, Option::None)
|
||||
.map_or(false, |l| have_lit(cx, l, m)),
|
||||
_ => false
|
||||
}
|
||||
},
|
||||
_ => false
|
||||
if let Some(c) = constant(cx, e) {
|
||||
if c.needed_resolution { return; } // skip linting w/ lookup for now
|
||||
if let ConstantInt(v, ty) = c.constant {
|
||||
if match m {
|
||||
0 => v == 0,
|
||||
-1 => is_negative(ty),
|
||||
1 => !is_negative(ty),
|
||||
_ => unreachable!(),
|
||||
} {
|
||||
span_lint(cx, IDENTITY_OP, span, &format!(
|
||||
"the operation is ineffective. Consider reducing it to `{}`",
|
||||
snippet(cx, arg, "..")));
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
@ -16,6 +16,7 @@ use rustc::lint::LintPassObject;
|
||||
|
||||
#[macro_use]
|
||||
pub mod utils;
|
||||
pub mod consts;
|
||||
pub mod types;
|
||||
pub mod misc;
|
||||
pub mod eq_op;
|
||||
|
||||
@ -11,14 +11,14 @@ fn main() {
|
||||
|
||||
x + 0; //~ERROR the operation is ineffective
|
||||
0 + x; //~ERROR the operation is ineffective
|
||||
x - ZERO; //~ERROR the operation is ineffective
|
||||
x - ZERO; //no error, as we skip lookups (for now)
|
||||
x | (0); //~ERROR the operation is ineffective
|
||||
((ZERO)) | x; //~ERROR the operation is ineffective
|
||||
((ZERO)) | x; //no error, as we skip lookups (for now)
|
||||
|
||||
x * 1; //~ERROR the operation is ineffective
|
||||
1 * x; //~ERROR the operation is ineffective
|
||||
x / ONE; //~ERROR the operation is ineffective
|
||||
x / ONE; //no error, as we skip lookups (for now)
|
||||
|
||||
x & NEG_ONE; //~ERROR the operation is ineffective
|
||||
x & NEG_ONE; //no error, as we skip lookups (for now)
|
||||
-1 & x; //~ERROR the operation is ineffective
|
||||
}
|
||||
|
||||
@ -2,6 +2,7 @@
|
||||
#![plugin(clippy)]
|
||||
|
||||
#[deny(precedence)]
|
||||
#[allow(identity_op)]
|
||||
#[allow(eq_op)]
|
||||
fn main() {
|
||||
format!("{} vs. {}", 1 << 2 + 3, (1 << 2) + 3); //~ERROR operator precedence can trip
|
||||
|
||||
34
tests/consts.rs
Normal file
34
tests/consts.rs
Normal file
@ -0,0 +1,34 @@
|
||||
#![allow(plugin_as_library)]
|
||||
#![feature(rustc_private)]
|
||||
|
||||
extern crate clippy;
|
||||
extern crate syntax;
|
||||
extern crate rustc;
|
||||
|
||||
use clippy::consts::constant;
|
||||
use clippy::consts::ConstantVariant::*;
|
||||
use syntax::ast::*;
|
||||
use syntax::ptr::P;
|
||||
use syntax::codemap::{Spanned, COMMAND_LINE_SP};
|
||||
use std::mem;
|
||||
use rustc::lint::Context;
|
||||
|
||||
fn ctx() -> &'static Context<'static, 'static> {
|
||||
unsafe {
|
||||
let x : *const Context<'static, 'static> = std::ptr::null();
|
||||
mem::transmute(x)
|
||||
}
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn test_lit() {
|
||||
assert_eq!(Some(ConstantBool(true)), constant(ctx(),
|
||||
&Expr{
|
||||
id: 1,
|
||||
node: ExprLit(P(Spanned{
|
||||
node: LitBool(true),
|
||||
span: COMMAND_LINE_SP,
|
||||
})),
|
||||
span: COMMAND_LINE_SP,
|
||||
}).map(|x| x.constant));
|
||||
}
|
||||
Loading…
Reference in New Issue
Block a user