use rustc::lint::*;
use rustc::ty;
use rustc::hir::*;
use std::collections::HashMap;
use std::collections::hash_map::Entry;
use syntax::parse::token::InternedString;
use syntax::util::small_vector::SmallVector;
use utils::{SpanlessEq, SpanlessHash};
use utils::{get_parent_expr, in_macro, span_note_and_lint};
declare_lint! {
pub IFS_SAME_COND,
Warn,
"consecutive `ifs` with the same condition"
}
declare_lint! {
pub IF_SAME_THEN_ELSE,
Warn,
"if with the same *then* and *else* blocks"
}
declare_lint! {
pub MATCH_SAME_ARMS,
Warn,
"`match` with identical arm bodies"
}
#[derive(Copy, Clone, Debug)]
pub struct CopyAndPaste;
impl LintPass for CopyAndPaste {
fn get_lints(&self) -> LintArray {
lint_array![IFS_SAME_COND, IF_SAME_THEN_ELSE, MATCH_SAME_ARMS]
}
}
impl LateLintPass for CopyAndPaste {
fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if !in_macro(cx, expr.span) {
if let Some(&Expr{node: ExprIf(_, _, Some(ref else_expr)), ..}) = get_parent_expr(cx, expr) {
if else_expr.id == expr.id {
return;
}
}
let (conds, blocks) = if_sequence(expr);
lint_same_then_else(cx, blocks.as_slice());
lint_same_cond(cx, conds.as_slice());
lint_match_arms(cx, expr);
}
}
}
fn lint_same_then_else(cx: &LateContext, blocks: &[&Block]) {
let hash: &Fn(&&Block) -> u64 = &|block| -> u64 {
let mut h = SpanlessHash::new(cx);
h.hash_block(block);
h.finish()
};
let eq: &Fn(&&Block, &&Block) -> bool = &|&lhs, &rhs| -> bool { SpanlessEq::new(cx).eq_block(lhs, rhs) };
if let Some((i, j)) = search_same(blocks, hash, eq) {
span_note_and_lint(cx,
IF_SAME_THEN_ELSE,
j.span,
"this `if` has identical blocks",
i.span,
"same as this");
}
}
fn lint_same_cond(cx: &LateContext, conds: &[&Expr]) {
let hash: &Fn(&&Expr) -> u64 = &|expr| -> u64 {
let mut h = SpanlessHash::new(cx);
h.hash_expr(expr);
h.finish()
};
let eq: &Fn(&&Expr, &&Expr) -> bool = &|&lhs, &rhs| -> bool { SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, rhs) };
if let Some((i, j)) = search_same(conds, hash, eq) {
span_note_and_lint(cx,
IFS_SAME_COND,
j.span,
"this `if` has the same condition as a previous if",
i.span,
"same as this");
}
}
fn lint_match_arms(cx: &LateContext, expr: &Expr) {
let hash = |arm: &Arm| -> u64 {
let mut h = SpanlessHash::new(cx);
h.hash_expr(&arm.body);
h.finish()
};
let eq = |lhs: &Arm, rhs: &Arm| -> bool {
lhs.guard.is_none() && rhs.guard.is_none() &&
SpanlessEq::new(cx).eq_expr(&lhs.body, &rhs.body) &&
bindings(cx, &lhs.pats[0]) == bindings(cx, &rhs.pats[0])
};
if let ExprMatch(_, ref arms, MatchSource::Normal) = expr.node {
if let Some((i, j)) = search_same(&arms, hash, eq) {
span_note_and_lint(cx,
MATCH_SAME_ARMS,
j.body.span,
"this `match` has identical arm bodies",
i.body.span,
"same as this");
}
}
}
fn if_sequence(mut expr: &Expr) -> (SmallVector<&Expr>, SmallVector<&Block>) {
let mut conds = SmallVector::zero();
let mut blocks = SmallVector::zero();
while let ExprIf(ref cond, ref then_block, ref else_expr) = expr.node {
conds.push(&**cond);
blocks.push(&**then_block);
if let Some(ref else_expr) = *else_expr {
expr = else_expr;
} else {
break;
}
}
if !blocks.is_empty() {
if let ExprBlock(ref block) = expr.node {
blocks.push(&**block);
}
}
(conds, blocks)
}
fn bindings<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, pat: &Pat) -> HashMap<InternedString, ty::Ty<'tcx>> {
fn bindings_impl<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, pat: &Pat, map: &mut HashMap<InternedString, ty::Ty<'tcx>>) {
match pat.node {
PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => bindings_impl(cx, pat, map),
PatKind::TupleStruct(_, Some(ref pats)) => {
for pat in pats {
bindings_impl(cx, pat, map);
}
}
PatKind::Ident(_, ref ident, ref as_pat) => {
if let Entry::Vacant(v) = map.entry(ident.node.name.as_str()) {
v.insert(cx.tcx.pat_ty(pat));
}
if let Some(ref as_pat) = *as_pat {
bindings_impl(cx, as_pat, map);
}
}
PatKind::Struct(_, ref fields, _) => {
for pat in fields {
bindings_impl(cx, &pat.node.pat, map);
}
}
PatKind::Tup(ref fields) => {
for pat in fields {
bindings_impl(cx, pat, map);
}
}
PatKind::Vec(ref lhs, ref mid, ref rhs) => {
for pat in lhs {
bindings_impl(cx, pat, map);
}
if let Some(ref mid) = *mid {
bindings_impl(cx, mid, map);
}
for pat in rhs {
bindings_impl(cx, pat, map);
}
}
PatKind::TupleStruct(..) |
PatKind::Lit(..) |
PatKind::QPath(..) |
PatKind::Range(..) |
PatKind::Wild |
PatKind::Path(..) => (),
}
}
let mut result = HashMap::new();
bindings_impl(cx, pat, &mut result);
result
}
fn search_same<T, Hash, Eq>(exprs: &[T], hash: Hash, eq: Eq) -> Option<(&T, &T)>
where Hash: Fn(&T) -> u64,
Eq: Fn(&T, &T) -> bool
{
if exprs.len() < 2 {
return None;
} else if exprs.len() == 2 {
return if eq(&exprs[0], &exprs[1]) {
Some((&exprs[0], &exprs[1]))
} else {
None
};
}
let mut map: HashMap<_, Vec<&_>> = HashMap::with_capacity(exprs.len());
for expr in exprs {
match map.entry(hash(expr)) {
Entry::Occupied(o) => {
for o in o.get() {
if eq(&o, expr) {
return Some((&o, expr));
}
}
}
Entry::Vacant(v) => {
v.insert(vec![expr]);
}
}
}
None
}