Add for _ in vec![…] to the USELESS_VEC lint
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mcarton
parent
11eae72e6f
commit
777e810a39
26
src/loops.rs
26
src/loops.rs
@ -14,7 +14,7 @@
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use utils::{snippet, span_lint, get_parent_expr, match_trait_method, match_type, in_external_macro,
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span_help_and_lint, is_integer_literal, get_enclosing_block, span_lint_and_then,
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unsugar_range, walk_ptrs_ty};
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unsugar_range, walk_ptrs_ty, recover_for_loop};
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use utils::{BTREEMAP_PATH, HASHMAP_PATH, LL_PATH, OPTION_PATH, RESULT_PATH, VEC_PATH};
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use utils::UnsugaredRange;
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@ -641,30 +641,6 @@ fn visit_expr(&mut self, expr: &Expr) {
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}
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}
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/// Recover the essential nodes of a desugared for loop:
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/// `for pat in arg { body }` becomes `(pat, arg, body)`.
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fn recover_for_loop(expr: &Expr) -> Option<(&Pat, &Expr, &Expr)> {
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if_let_chain! {
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[
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let ExprMatch(ref iterexpr, ref arms, _) = expr.node,
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let ExprCall(_, ref iterargs) = iterexpr.node,
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iterargs.len() == 1 && arms.len() == 1 && arms[0].guard.is_none(),
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let ExprLoop(ref block, _) = arms[0].body.node,
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block.stmts.is_empty(),
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let Some(ref loopexpr) = block.expr,
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let ExprMatch(_, ref innerarms, MatchSource::ForLoopDesugar) = loopexpr.node,
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innerarms.len() == 2 && innerarms[0].pats.len() == 1,
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let PatKind::TupleStruct(_, Some(ref somepats)) = innerarms[0].pats[0].node,
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somepats.len() == 1
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], {
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return Some((&somepats[0],
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&iterargs[0],
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&innerarms[0].body));
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}
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}
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None
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}
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struct VarVisitor<'v, 't: 'v> {
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cx: &'v LateContext<'v, 't>, // context reference
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var: Name, // var name to look for as index
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@ -800,3 +800,27 @@ pub fn same_tys<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, a: ty::Ty<'tcx>, b: ty::Ty
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let new_b = b.subst(infcx.tcx, &infcx.parameter_environment.free_substs);
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infcx.can_equate(&new_a, &new_b).is_ok()
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}
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/// Recover the essential nodes of a desugared for loop:
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/// `for pat in arg { body }` becomes `(pat, arg, body)`.
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pub fn recover_for_loop(expr: &Expr) -> Option<(&Pat, &Expr, &Expr)> {
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if_let_chain! {
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[
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let ExprMatch(ref iterexpr, ref arms, _) = expr.node,
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let ExprCall(_, ref iterargs) = iterexpr.node,
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iterargs.len() == 1 && arms.len() == 1 && arms[0].guard.is_none(),
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let ExprLoop(ref block, _) = arms[0].body.node,
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block.stmts.is_empty(),
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let Some(ref loopexpr) = block.expr,
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let ExprMatch(_, ref innerarms, MatchSource::ForLoopDesugar) = loopexpr.node,
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innerarms.len() == 2 && innerarms[0].pats.len() == 1,
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let PatKind::TupleStruct(_, Some(ref somepats)) = innerarms[0].pats[0].node,
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somepats.len() == 1
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], {
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return Some((&somepats[0],
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&iterargs[0],
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&innerarms[0].body));
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}
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}
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None
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}
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60
src/vec.rs
60
src/vec.rs
@ -4,7 +4,7 @@
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use syntax::codemap::Span;
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use syntax::ptr::P;
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use utils::VEC_FROM_ELEM_PATH;
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use utils::{is_expn_of, match_path, snippet, span_lint_and_then};
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use utils::{is_expn_of, match_path, recover_for_loop, snippet, span_lint_and_then};
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/// **What it does:** This lint warns about using `&vec![..]` when using `&[..]` would be possible.
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///
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@ -38,32 +38,42 @@ fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
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let TypeVariants::TyRef(_, ref ty) = cx.tcx.expr_ty_adjusted(expr).sty,
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let TypeVariants::TySlice(..) = ty.ty.sty,
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let ExprAddrOf(_, ref addressee) = expr.node,
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let Some(vec_args) = unexpand_vec(cx, addressee)
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], {
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let snippet = match vec_args {
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VecArgs::Repeat(elem, len) => {
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format!("&[{}; {}]", snippet(cx, elem.span, "elem"), snippet(cx, len.span, "len")).into()
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}
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VecArgs::Vec(args) => {
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if let Some(last) = args.iter().last() {
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let span = Span {
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lo: args[0].span.lo,
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hi: last.span.hi,
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expn_id: args[0].span.expn_id,
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};
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format!("&[{}]", snippet(cx, span, "..")).into()
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}
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else {
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"&[]".into()
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}
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}
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};
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span_lint_and_then(cx, USELESS_VEC, expr.span, "useless use of `vec!`", |db| {
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db.span_suggestion(expr.span, "you can use a slice directly", snippet);
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});
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check_vec_macro(cx, expr, addressee);
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}}
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// search for `for _ in vec![…]`
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if let Some((_, arg, _)) = recover_for_loop(expr) {
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check_vec_macro(cx, arg, arg);
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}
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}
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}
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fn check_vec_macro(cx: &LateContext, expr: &Expr, vec: &Expr) {
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if let Some(vec_args) = unexpand_vec(cx, vec) {
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let snippet = match vec_args {
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VecArgs::Repeat(elem, len) => {
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format!("&[{}; {}]", snippet(cx, elem.span, "elem"), snippet(cx, len.span, "len")).into()
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}
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VecArgs::Vec(args) => {
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if let Some(last) = args.iter().last() {
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let span = Span {
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lo: args[0].span.lo,
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hi: last.span.hi,
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expn_id: args[0].span.expn_id,
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};
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format!("&[{}]", snippet(cx, span, "..")).into()
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}
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else {
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"&[]".into()
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}
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}
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};
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span_lint_and_then(cx, USELESS_VEC, expr.span, "useless use of `vec!`", |db| {
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db.span_suggestion(expr.span, "you can use a slice directly", snippet);
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});
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}
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}
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@ -41,4 +41,11 @@ fn main() {
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on_vec(&vec![]);
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on_vec(&vec![1, 2]);
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on_vec(&vec![1; 2]);
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for a in vec![1, 2, 3] {
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//~^ ERROR useless use of `vec!`
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//~| HELP you can use
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//~| SUGGESTION for a in &[1, 2, 3] {
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println!("{}", a);
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}
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}
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