Differentiate between mutable iteration and immutable iteration in needless_range_loop

This commit is contained in:
Oliver Schneider 2017-11-07 14:41:54 +01:00
parent 088555c4ea
commit 652df0fb79
No known key found for this signature in database
GPG key ID: A69F8D225B3AD7D9
3 changed files with 100 additions and 5 deletions

View file

@ -952,10 +952,12 @@ fn check_for_loop_range<'a, 'tcx>(
let mut visitor = VarVisitor {
cx: cx,
var: canonical_id,
indexed_mut: HashSet::new(),
indexed: HashMap::new(),
indexed_directly: HashMap::new(),
referenced: HashSet::new(),
nonindex: false,
prefer_mutable: false,
};
walk_expr(&mut visitor, body);
@ -1009,6 +1011,12 @@ fn check_for_loop_range<'a, 'tcx>(
"".to_owned()
};
let (ref_mut, method) = if visitor.indexed_mut.contains(&indexed) {
("mut ", "iter_mut")
} else {
("", "iter")
};
if visitor.nonindex {
span_lint_and_then(
cx,
@ -1021,16 +1029,16 @@ fn check_for_loop_range<'a, 'tcx>(
"consider using an iterator".to_string(),
vec![
(pat.span, format!("({}, <item>)", ident.node)),
(arg.span, format!("{}.iter().enumerate(){}{}", indexed, take, skip)),
(arg.span, format!("{}.{}().enumerate(){}{}", indexed, method, take, skip)),
],
);
},
);
} else {
let repl = if starts_at_zero && take.is_empty() {
format!("&{}", indexed)
format!("&{}{}", ref_mut, indexed)
} else {
format!("{}.iter(){}{}", indexed, take, skip)
format!("{}.{}(){}{}", indexed, method, take, skip)
};
span_lint_and_then(
@ -1537,6 +1545,8 @@ struct VarVisitor<'a, 'tcx: 'a> {
cx: &'a LateContext<'a, 'tcx>,
/// var name to look for as index
var: ast::NodeId,
/// indexed variables that are used mutably
indexed_mut: HashSet<Name>,
/// indexed variables, the extend is `None` for global
indexed: HashMap<Name, Option<region::Scope>>,
/// subset of `indexed` of vars that are indexed directly: `v[i]`
@ -1548,6 +1558,9 @@ struct VarVisitor<'a, 'tcx: 'a> {
/// has the loop variable been used in expressions other than the index of
/// an index op?
nonindex: bool,
/// Whether we are inside the `$` in `&mut $` or `$ = foo` or `$.bar`, where bar
/// takes `&mut self`
prefer_mutable: bool,
}
impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
@ -1572,6 +1585,9 @@ impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
};
if index_used {
if self.prefer_mutable {
self.indexed_mut.insert(seqvar.segments[0].name);
}
let def = self.cx.tables.qpath_def(seqpath, seqexpr.hir_id);
match def {
Def::Local(node_id) | Def::Upvar(node_id, ..) => {
@ -1615,8 +1631,47 @@ impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
}
}
}
walk_expr(self, expr);
let old = self.prefer_mutable;
match expr.node {
ExprAssignOp(_, ref lhs, ref rhs) |
ExprAssign(ref lhs, ref rhs) => {
self.prefer_mutable = true;
self.visit_expr(lhs);
self.prefer_mutable = false;
self.visit_expr(rhs);
},
ExprAddrOf(mutbl, ref expr) => {
if mutbl == MutMutable {
self.prefer_mutable = true;
}
self.visit_expr(expr);
},
ExprCall(ref f, ref args) => {
for (ty, expr) in self.cx.tables.expr_ty(f).fn_sig(self.cx.tcx).inputs().skip_binder().iter().zip(args) {
self.prefer_mutable = false;
if let ty::TyRef(_, mutbl) = ty.sty {
if mutbl.mutbl == MutMutable {
self.prefer_mutable = true;
}
}
self.visit_expr(expr);
}
},
ExprMethodCall(_, _, ref args) => {
let def_id = self.cx.tables.type_dependent_defs()[expr.hir_id].def_id();
for (ty, expr) in self.cx.tcx.fn_sig(def_id).inputs().skip_binder().iter().zip(args) {
self.prefer_mutable = false;
if let ty::TyRef(_, mutbl) = ty.sty {
if mutbl.mutbl == MutMutable {
self.prefer_mutable = true;
}
}
self.visit_expr(expr);
}
},
_ => walk_expr(self, expr),
}
self.prefer_mutable = old;
}
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None

View file

@ -24,4 +24,17 @@ fn main() {
for i in 3..10 {
println!("{}", ns[calc_idx(i) % 4]);
}
let mut ms = vec![1, 2, 3, 4, 5, 6];
for i in 0..ms.len() {
ms[i] *= 2;
}
assert_eq!(ms, vec![2, 4, 6, 8, 10, 12]);
let mut ms = vec![1, 2, 3, 4, 5, 6];
for i in 0..ms.len() {
let x = &mut ms[i];
*x *= 2;
}
assert_eq!(ms, vec![2, 4, 6, 8, 10, 12]);
}

View file

@ -12,3 +12,30 @@ help: consider using an iterator
8 | for <item> in ns.iter().take(10).skip(3) {
| ^^^^^^
error: the loop variable `i` is only used to index `ms`.
--> $DIR/needless_range_loop.rs:29:5
|
29 | / for i in 0..ms.len() {
30 | | ms[i] *= 2;
31 | | }
| |_____^
|
help: consider using an iterator
|
29 | for <item> in &mut ms {
| ^^^^^^
error: the loop variable `i` is only used to index `ms`.
--> $DIR/needless_range_loop.rs:35:5
|
35 | / for i in 0..ms.len() {
36 | | let x = &mut ms[i];
37 | | *x *= 2;
38 | | }
| |_____^
|
help: consider using an iterator
|
35 | for <item> in &mut ms {
| ^^^^^^