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https://github.com/rust-lang/rust-clippy
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Merge pull request #2214 from rust-lang-nursery/nrlfp
Improve `needless_range_loop`
This commit is contained in:
Oliver Schneider
GitHub
commit
09d988521d
3 changed files with 151 additions and 20 deletions
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@ -952,16 +952,17 @@ fn check_for_loop_range<'a, 'tcx>(
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let mut visitor = VarVisitor {
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cx: cx,
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var: canonical_id,
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indexed: HashMap::new(),
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indexed_mut: HashSet::new(),
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indexed_indirectly: HashMap::new(),
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indexed_directly: HashMap::new(),
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referenced: HashSet::new(),
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nonindex: false,
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prefer_mutable: false,
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};
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walk_expr(&mut visitor, body);
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// linting condition: we only indexed one variable, and indexed it directly
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// (`indexed_directly` is subset of `indexed`)
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if visitor.indexed.len() == 1 && visitor.indexed_directly.len() == 1 {
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if visitor.indexed_indirectly.is_empty() && visitor.indexed_directly.len() == 1 {
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let (indexed, indexed_extent) = visitor
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.indexed_directly
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.into_iter()
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@ -1009,6 +1010,12 @@ fn check_for_loop_range<'a, 'tcx>(
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"".to_owned()
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};
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let (ref_mut, method) = if visitor.indexed_mut.contains(&indexed) {
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("mut ", "iter_mut")
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} else {
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("", "iter")
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};
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if visitor.nonindex {
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span_lint_and_then(
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cx,
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@ -1021,16 +1028,16 @@ fn check_for_loop_range<'a, 'tcx>(
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"consider using an iterator".to_string(),
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vec![
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(pat.span, format!("({}, <item>)", ident.node)),
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(arg.span, format!("{}.iter().enumerate(){}{}", indexed, take, skip)),
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(arg.span, format!("{}.{}().enumerate(){}{}", indexed, method, take, skip)),
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],
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);
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},
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);
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} else {
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let repl = if starts_at_zero && take.is_empty() {
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format!("&{}", indexed)
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format!("&{}{}", ref_mut, indexed)
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} else {
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format!("{}.iter(){}{}", indexed, take, skip)
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format!("{}.{}(){}{}", indexed, method, take, skip)
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};
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span_lint_and_then(
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@ -1537,8 +1544,10 @@ struct VarVisitor<'a, 'tcx: 'a> {
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cx: &'a LateContext<'a, 'tcx>,
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/// var name to look for as index
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var: ast::NodeId,
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/// indexed variables, the extend is `None` for global
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indexed: HashMap<Name, Option<region::Scope>>,
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/// indexed variables that are used mutably
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indexed_mut: HashSet<Name>,
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/// indirectly indexed variables (`v[(i + 4) % N]`), the extend is `None` for global
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indexed_indirectly: HashMap<Name, Option<region::Scope>>,
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/// subset of `indexed` of vars that are indexed directly: `v[i]`
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/// this will not contain cases like `v[calc_index(i)]` or `v[(i + 4) % N]`
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indexed_directly: HashMap<Name, Option<region::Scope>>,
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@ -1548,20 +1557,21 @@ struct VarVisitor<'a, 'tcx: 'a> {
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/// has the loop variable been used in expressions other than the index of
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/// an index op?
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nonindex: bool,
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/// Whether we are inside the `$` in `&mut $` or `$ = foo` or `$.bar`, where bar
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/// takes `&mut self`
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prefer_mutable: bool,
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}
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impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
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fn visit_expr(&mut self, expr: &'tcx Expr) {
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impl<'a, 'tcx> VarVisitor<'a, 'tcx> {
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fn check(&mut self, idx: &'tcx Expr, seqexpr: &'tcx Expr, expr: &'tcx Expr) -> bool {
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if_chain! {
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// an index op
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if let ExprIndex(ref seqexpr, ref idx) = expr.node;
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// the indexed container is referenced by a name
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if let ExprPath(ref seqpath) = seqexpr.node;
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if let QPath::Resolved(None, ref seqvar) = *seqpath;
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if seqvar.segments.len() == 1;
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then {
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let index_used_directly = same_var(self.cx, idx, self.var);
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let index_used = index_used_directly || {
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let indexed_indirectly = {
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let mut used_visitor = LocalUsedVisitor {
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cx: self.cx,
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local: self.var,
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@ -1571,7 +1581,10 @@ impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
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used_visitor.used
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};
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if index_used {
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if indexed_indirectly || index_used_directly {
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if self.prefer_mutable {
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self.indexed_mut.insert(seqvar.segments[0].name);
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}
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let def = self.cx.tables.qpath_def(seqpath, seqexpr.hir_id);
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match def {
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Def::Local(node_id) | Def::Upvar(node_id, ..) => {
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@ -1580,24 +1593,48 @@ impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
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let parent_id = self.cx.tcx.hir.get_parent(expr.id);
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let parent_def_id = self.cx.tcx.hir.local_def_id(parent_id);
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let extent = self.cx.tcx.region_scope_tree(parent_def_id).var_scope(hir_id.local_id);
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self.indexed.insert(seqvar.segments[0].name, Some(extent));
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if indexed_indirectly {
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self.indexed_indirectly.insert(seqvar.segments[0].name, Some(extent));
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}
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if index_used_directly {
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self.indexed_directly.insert(seqvar.segments[0].name, Some(extent));
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}
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return; // no need to walk further *on the variable*
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return false; // no need to walk further *on the variable*
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}
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Def::Static(..) | Def::Const(..) => {
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self.indexed.insert(seqvar.segments[0].name, None);
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if indexed_indirectly {
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self.indexed_indirectly.insert(seqvar.segments[0].name, None);
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}
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if index_used_directly {
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self.indexed_directly.insert(seqvar.segments[0].name, None);
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}
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return; // no need to walk further *on the variable*
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return false; // no need to walk further *on the variable*
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}
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_ => (),
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}
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}
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}
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}
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true
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}
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}
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impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
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fn visit_expr(&mut self, expr: &'tcx Expr) {
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if_chain! {
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// a range index op
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if let ExprMethodCall(ref meth, _, ref args) = expr.node;
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if meth.name == "index" || meth.name == "index_mut";
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if !self.check(&args[1], &args[0], expr);
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then { return }
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}
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if_chain! {
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// an index op
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if let ExprIndex(ref seqexpr, ref idx) = expr.node;
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if !self.check(idx, seqexpr, expr);
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then { return }
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}
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if_chain! {
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// directly using a variable
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@ -1615,8 +1652,47 @@ impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
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}
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}
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}
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walk_expr(self, expr);
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let old = self.prefer_mutable;
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match expr.node {
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ExprAssignOp(_, ref lhs, ref rhs) |
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ExprAssign(ref lhs, ref rhs) => {
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self.prefer_mutable = true;
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self.visit_expr(lhs);
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self.prefer_mutable = false;
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self.visit_expr(rhs);
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},
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ExprAddrOf(mutbl, ref expr) => {
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if mutbl == MutMutable {
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self.prefer_mutable = true;
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}
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self.visit_expr(expr);
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},
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ExprCall(ref f, ref args) => {
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for (ty, expr) in self.cx.tables.expr_ty(f).fn_sig(self.cx.tcx).inputs().skip_binder().iter().zip(args) {
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self.prefer_mutable = false;
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if let ty::TyRef(_, mutbl) = ty.sty {
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if mutbl.mutbl == MutMutable {
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self.prefer_mutable = true;
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}
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}
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self.visit_expr(expr);
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}
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},
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ExprMethodCall(_, _, ref args) => {
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let def_id = self.cx.tables.type_dependent_defs()[expr.hir_id].def_id();
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for (ty, expr) in self.cx.tcx.fn_sig(def_id).inputs().skip_binder().iter().zip(args) {
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self.prefer_mutable = false;
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if let ty::TyRef(_, mutbl) = ty.sty {
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if mutbl.mutbl == MutMutable {
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self.prefer_mutable = true;
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}
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}
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self.visit_expr(expr);
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}
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},
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_ => walk_expr(self, expr),
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}
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self.prefer_mutable = old;
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}
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fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
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NestedVisitorMap::None
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@ -24,4 +24,32 @@ fn main() {
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for i in 3..10 {
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println!("{}", ns[calc_idx(i) % 4]);
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}
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let mut ms = vec![1, 2, 3, 4, 5, 6];
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for i in 0..ms.len() {
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ms[i] *= 2;
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}
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assert_eq!(ms, vec![2, 4, 6, 8, 10, 12]);
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let mut ms = vec![1, 2, 3, 4, 5, 6];
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for i in 0..ms.len() {
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let x = &mut ms[i];
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*x *= 2;
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}
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assert_eq!(ms, vec![2, 4, 6, 8, 10, 12]);
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let g = vec![1, 2, 3, 4, 5, 6];
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let glen = g.len();
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for i in 0..glen {
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let x: u32 = g[i+1..].iter().sum();
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println!("{}", g[i] + x);
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}
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assert_eq!(g, vec![20, 18, 15, 11, 6, 0]);
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let mut g = vec![1, 2, 3, 4, 5, 6];
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let glen = g.len();
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for i in 0..glen {
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g[i] = g[i+1..].iter().sum();
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}
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assert_eq!(g, vec![20, 18, 15, 11, 6, 0]);
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}
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@ -12,3 +12,30 @@ help: consider using an iterator
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8 | for <item> in ns.iter().take(10).skip(3) {
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error: the loop variable `i` is only used to index `ms`.
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--> $DIR/needless_range_loop.rs:29:5
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29 | / for i in 0..ms.len() {
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30 | | ms[i] *= 2;
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31 | | }
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| |_____^
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help: consider using an iterator
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29 | for <item> in &mut ms {
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| ^^^^^^
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error: the loop variable `i` is only used to index `ms`.
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--> $DIR/needless_range_loop.rs:35:5
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35 | / for i in 0..ms.len() {
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36 | | let x = &mut ms[i];
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37 | | *x *= 2;
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38 | | }
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| |_____^
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help: consider using an iterator
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35 | for <item> in &mut ms {
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| ^^^^^^
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