From 96e2bc80f556e54b95ae224dc2f59cfa47397a38 Mon Sep 17 00:00:00 2001
From: CrazyRoka <rokarostuk@gmail.com>
Date: Fri, 24 Apr 2020 00:28:18 +0300
Subject: [PATCH] Added lint `match_vec_item`
---
CHANGELOG.md | 1 +
clippy_lints/src/lib.rs | 5 ++
clippy_lints/src/match_vec_item.rs | 111 +++++++++++++++++++++++++++++
src/lintlist/mod.rs | 7 ++
tests/ui/match_vec_item.rs | 109 ++++++++++++++++++++++++++++
tests/ui/match_vec_item.stderr | 27 +++++++
6 files changed, 260 insertions(+)
create mode 100644 clippy_lints/src/match_vec_item.rs
create mode 100644 tests/ui/match_vec_item.rs
create mode 100644 tests/ui/match_vec_item.stderr
diff --git a/CHANGELOG.md b/CHANGELOG.md
index abd7167502b..3ba2c51623b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1352,6 +1352,7 @@ Released 2018-09-13
[`match_ref_pats`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_ref_pats
[`match_same_arms`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_same_arms
[`match_single_binding`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_single_binding
+[`match_vec_item`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_vec_item
[`match_wild_err_arm`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_wild_err_arm
[`maybe_infinite_iter`]: https://rust-lang.github.io/rust-clippy/master/index.html#maybe_infinite_iter
[`mem_discriminant_non_enum`]: https://rust-lang.github.io/rust-clippy/master/index.html#mem_discriminant_non_enum
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index dee4188b75f..79bf13a1005 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -249,6 +249,7 @@ mod macro_use;
mod main_recursion;
mod map_clone;
mod map_unit_fn;
+mod match_vec_item;
mod matches;
mod mem_discriminant;
mod mem_forget;
@@ -629,6 +630,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
&map_clone::MAP_CLONE,
&map_unit_fn::OPTION_MAP_UNIT_FN,
&map_unit_fn::RESULT_MAP_UNIT_FN,
+ &match_vec_item::MATCH_VEC_ITEM,
&matches::INFALLIBLE_DESTRUCTURING_MATCH,
&matches::MATCH_AS_REF,
&matches::MATCH_BOOL,
@@ -1060,6 +1062,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
store.register_late_pass(|| box future_not_send::FutureNotSend);
store.register_late_pass(|| box utils::internal_lints::CollapsibleCalls);
store.register_late_pass(|| box if_let_mutex::IfLetMutex);
+ store.register_late_pass(|| box match_vec_item::MatchVecItem);
store.register_group(true, "clippy::restriction", Some("clippy_restriction"), vec![
LintId::of(&arithmetic::FLOAT_ARITHMETIC),
@@ -1277,6 +1280,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&map_clone::MAP_CLONE),
LintId::of(&map_unit_fn::OPTION_MAP_UNIT_FN),
LintId::of(&map_unit_fn::RESULT_MAP_UNIT_FN),
+ LintId::of(&match_vec_item::MATCH_VEC_ITEM),
LintId::of(&matches::INFALLIBLE_DESTRUCTURING_MATCH),
LintId::of(&matches::MATCH_AS_REF),
LintId::of(&matches::MATCH_BOOL),
@@ -1469,6 +1473,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&loops::WHILE_LET_ON_ITERATOR),
LintId::of(&main_recursion::MAIN_RECURSION),
LintId::of(&map_clone::MAP_CLONE),
+ LintId::of(&match_vec_item::MATCH_VEC_ITEM),
LintId::of(&matches::INFALLIBLE_DESTRUCTURING_MATCH),
LintId::of(&matches::MATCH_BOOL),
LintId::of(&matches::MATCH_OVERLAPPING_ARM),
diff --git a/clippy_lints/src/match_vec_item.rs b/clippy_lints/src/match_vec_item.rs
new file mode 100644
index 00000000000..7ea5a24abbd
--- /dev/null
+++ b/clippy_lints/src/match_vec_item.rs
@@ -0,0 +1,111 @@
+use crate::utils::{is_wild, span_lint_and_help};
+use if_chain::if_chain;
+use rustc_hir::{Arm, Expr, ExprKind, MatchSource};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_middle::lint::in_external_macro;
+use rustc_middle::ty::{self, AdtDef};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for `match vec[idx]` or `match vec[n..m]`.
+ ///
+ /// **Why is this bad?** This can panic at runtime.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust, no_run
+ /// let arr = vec![0, 1, 2, 3];
+ /// let idx = 1;
+ ///
+ /// // Bad
+ /// match arr[idx] {
+ /// 0 => println!("{}", 0),
+ /// 1 => println!("{}", 3),
+ /// _ => {},
+ /// }
+ /// ```
+ /// Use instead:
+ /// ```rust, no_run
+ /// let arr = vec![0, 1, 2, 3];
+ /// let idx = 1;
+ ///
+ /// // Good
+ /// match arr.get(idx) {
+ /// Some(0) => println!("{}", 0),
+ /// Some(1) => println!("{}", 3),
+ /// _ => {},
+ /// }
+ /// ```
+ pub MATCH_VEC_ITEM,
+ style,
+ "match vector by indexing can panic"
+}
+
+declare_lint_pass!(MatchVecItem => [MATCH_VEC_ITEM]);
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MatchVecItem {
+ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) {
+ if_chain! {
+ if !in_external_macro(cx.sess(), expr.span);
+ if let ExprKind::Match(ref ex, ref arms, MatchSource::Normal) = expr.kind;
+ if contains_wild_arm(arms);
+ if is_vec_indexing(cx, ex);
+
+ then {
+ span_lint_and_help(
+ cx,
+ MATCH_VEC_ITEM,
+ expr.span,
+ "indexing vector may panic",
+ None,
+ "consider using `get(..)` instead.",
+ );
+ }
+ }
+ }
+}
+
+fn contains_wild_arm(arms: &[Arm<'_>]) -> bool {
+ arms.iter().any(|arm| is_wild(&arm.pat) && is_unit_expr(arm.body))
+}
+
+fn is_vec_indexing<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
+ if_chain! {
+ if let ExprKind::Index(ref array, _) = expr.kind;
+ let ty = cx.tables.expr_ty(array);
+ if let ty::Adt(def, _) = ty.kind;
+ if is_vec(cx, def);
+
+ then {
+ return true;
+ }
+ }
+
+ false
+}
+
+fn is_vec<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, def: &'a AdtDef) -> bool {
+ if_chain! {
+ let def_path = cx.tcx.def_path(def.did);
+ if def_path.data.len() == 2;
+ if let Some(module) = def_path.data.get(0);
+ if module.data.as_symbol() == sym!(vec);
+ if let Some(name) = def_path.data.get(1);
+ if name.data.as_symbol() == sym!(Vec);
+
+ then {
+ return true;
+ }
+ }
+
+ false
+}
+
+fn is_unit_expr(expr: &Expr<'_>) -> bool {
+ match expr.kind {
+ ExprKind::Tup(ref v) if v.is_empty() => true,
+ ExprKind::Block(ref b, _) if b.stmts.is_empty() && b.expr.is_none() => true,
+ _ => false,
+ }
+}
diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs
index 2c466aa20c6..7c9e0448950 100644
--- a/src/lintlist/mod.rs
+++ b/src/lintlist/mod.rs
@@ -1172,6 +1172,13 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
deprecation: None,
module: "matches",
},
+ Lint {
+ name: "match_vec_item",
+ group: "style",
+ desc: "match vector by indexing can panic",
+ deprecation: None,
+ module: "match_vec_item",
+ },
Lint {
name: "match_wild_err_arm",
group: "style",
diff --git a/tests/ui/match_vec_item.rs b/tests/ui/match_vec_item.rs
new file mode 100644
index 00000000000..8e7c098d75c
--- /dev/null
+++ b/tests/ui/match_vec_item.rs
@@ -0,0 +1,109 @@
+#![warn(clippy::match_vec_item)]
+
+fn main() {
+ match_with_wildcard();
+ match_without_wildcard();
+ match_wildcard_and_action();
+ match_with_get();
+ match_with_array();
+}
+
+fn match_with_wildcard() {
+ let arr = vec![0, 1, 2, 3];
+ let range = 1..3;
+ let idx = 1;
+
+ // Lint, may panic
+ match arr[idx] {
+ 0 => println!("0"),
+ 1 => println!("1"),
+ _ => {},
+ }
+
+ // Lint, may panic
+ match arr[range] {
+ [0, 1] => println!("0 1"),
+ [1, 2] => println!("1 2"),
+ _ => {},
+ }
+}
+
+fn match_without_wildcard() {
+ let arr = vec![0, 1, 2, 3];
+ let range = 1..3;
+ let idx = 2;
+
+ // Ok
+ match arr[idx] {
+ 0 => println!("0"),
+ 1 => println!("1"),
+ num => {},
+ }
+
+ // Ok
+ match arr[range] {
+ [0, 1] => println!("0 1"),
+ [1, 2] => println!("1 2"),
+ [ref sub @ ..] => {},
+ }
+}
+
+fn match_wildcard_and_action() {
+ let arr = vec![0, 1, 2, 3];
+ let range = 1..3;
+ let idx = 3;
+
+ // Ok
+ match arr[idx] {
+ 0 => println!("0"),
+ 1 => println!("1"),
+ _ => println!("Hello, World!"),
+ }
+
+ // Ok
+ match arr[range] {
+ [0, 1] => println!("0 1"),
+ [1, 2] => println!("1 2"),
+ _ => println!("Hello, World!"),
+ }
+}
+
+fn match_with_get() {
+ let arr = vec![0, 1, 2, 3];
+ let range = 1..3;
+ let idx = 3;
+
+ // Ok
+ match arr.get(idx) {
+ Some(0) => println!("0"),
+ Some(1) => println!("1"),
+ _ => {},
+ }
+
+ // Ok
+ match arr.get(range) {
+ Some(&[0, 1]) => println!("0 1"),
+ Some(&[1, 2]) => println!("1 2"),
+ _ => {},
+ }
+}
+
+fn match_with_array() {
+ let arr = [0, 1, 2, 3];
+ let range = 1..3;
+ let idx = 3;
+
+ // Ok
+ match arr[idx] {
+ 0 => println!("0"),
+ 1 => println!("1"),
+ _ => {},
+ }
+
+ // Ok
+ match arr[range] {
+ [0, 1] => println!("0 1"),
+ [1, 2] => println!("1 2"),
+ _ => {},
+ }
+}
diff --git a/tests/ui/match_vec_item.stderr b/tests/ui/match_vec_item.stderr
new file mode 100644
index 00000000000..2494c3143f8
--- /dev/null
+++ b/tests/ui/match_vec_item.stderr
@@ -0,0 +1,27 @@
+error: indexing vector may panic
+ --> $DIR/match_vec_item.rs:17:5
+ |
+LL | / match arr[idx] {
+LL | | 0 => println!("0"),
+LL | | 1 => println!("1"),
+LL | | _ => {},
+LL | | }
+ | |_____^
+ |
+ = note: `-D clippy::match-vec-item` implied by `-D warnings`
+ = help: consider using `get(..)` instead.
+
+error: indexing vector may panic
+ --> $DIR/match_vec_item.rs:24:5
+ |
+LL | / match arr[range] {
+LL | | [0, 1] => println!("0 1"),
+LL | | [1, 2] => println!("1 2"),
+LL | | _ => {},
+LL | | }
+ | |_____^
+ |
+ = help: consider using `get(..)` instead.
+
+error: aborting due to 2 previous errors
+