diff --git a/CHANGELOG.md b/CHANGELOG.md
index 847a8d86e17..575773580c0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1431,6 +1431,7 @@ Released 2018-09-13
[`map_flatten`]: https://rust-lang.github.io/rust-clippy/master/index.html#map_flatten
[`match_as_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_as_ref
[`match_bool`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_bool
+[`match_on_vec_items`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_on_vec_items
[`match_overlapping_arm`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_overlapping_arm
[`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
diff --git a/clippy_lints/src/consts.rs b/clippy_lints/src/consts.rs
index 7916996e990..81ddc8c0067 100644
--- a/clippy_lints/src/consts.rs
+++ b/clippy_lints/src/consts.rs
@@ -358,9 +358,9 @@ impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
},
(Some(Constant::Vec(vec)), _) => {
if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
- match vec[0] {
- Constant::F32(x) => Some(Constant::F32(x)),
- Constant::F64(x) => Some(Constant::F64(x)),
+ match vec.get(0) {
+ Some(Constant::F32(x)) => Some(Constant::F32(*x)),
+ Some(Constant::F64(x)) => Some(Constant::F64(*x)),
_ => None,
}
} else {
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 4daaf9a9820..c995be5edc2 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_on_vec_items;
mod matches;
mod mem_discriminant;
mod mem_forget;
@@ -630,6 +631,7 @@ 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_on_vec_items::MATCH_ON_VEC_ITEMS,
&matches::INFALLIBLE_DESTRUCTURING_MATCH,
&matches::MATCH_AS_REF,
&matches::MATCH_BOOL,
@@ -1061,6 +1063,7 @@ 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_on_vec_items::MatchOnVecItems);
store.register_group(true, "clippy::restriction", Some("clippy_restriction"), vec![
LintId::of(&arithmetic::FLOAT_ARITHMETIC),
@@ -1280,6 +1283,7 @@ 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_on_vec_items::MATCH_ON_VEC_ITEMS),
LintId::of(&matches::INFALLIBLE_DESTRUCTURING_MATCH),
LintId::of(&matches::MATCH_AS_REF),
LintId::of(&matches::MATCH_OVERLAPPING_ARM),
@@ -1643,6 +1647,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&loops::NEVER_LOOP),
LintId::of(&loops::REVERSE_RANGE_LOOP),
LintId::of(&loops::WHILE_IMMUTABLE_CONDITION),
+ LintId::of(&match_on_vec_items::MATCH_ON_VEC_ITEMS),
LintId::of(&mem_discriminant::MEM_DISCRIMINANT_NON_ENUM),
LintId::of(&mem_replace::MEM_REPLACE_WITH_UNINIT),
LintId::of(&methods::CLONE_DOUBLE_REF),
diff --git a/clippy_lints/src/match_on_vec_items.rs b/clippy_lints/src/match_on_vec_items.rs
new file mode 100644
index 00000000000..4071406cc84
--- /dev/null
+++ b/clippy_lints/src/match_on_vec_items.rs
@@ -0,0 +1,89 @@
+use crate::utils::{is_type_diagnostic_item, snippet, span_lint_and_sugg, walk_ptrs_ty};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind, MatchSource};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_middle::lint::in_external_macro;
+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_ON_VEC_ITEMS,
+ correctness,
+ "matching on vector elements can panic"
+}
+
+declare_lint_pass!(MatchOnVecItems => [MATCH_ON_VEC_ITEMS]);
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MatchOnVecItems {
+ 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 match_expr, _, MatchSource::Normal) = expr.kind;
+ if let Some(idx_expr) = is_vec_indexing(cx, match_expr);
+ if let ExprKind::Index(vec, idx) = idx_expr.kind;
+
+ then {
+ // FIXME: could be improved to suggest surrounding every pattern with Some(_),
+ // but only when `or_patterns` are stabilized.
+ span_lint_and_sugg(
+ cx,
+ MATCH_ON_VEC_ITEMS,
+ match_expr.span,
+ "indexing into a vector may panic",
+ "try this",
+ format!(
+ "{}.get({})",
+ snippet(cx, vec.span, ".."),
+ snippet(cx, idx.span, "..")
+ ),
+ Applicability::MaybeIncorrect
+ );
+ }
+ }
+ }
+}
+
+fn is_vec_indexing<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) -> Option<&'tcx Expr<'tcx>> {
+ if_chain! {
+ if let ExprKind::Index(ref array, _) = expr.kind;
+ let ty = cx.tables.expr_ty(array);
+ let ty = walk_ptrs_ty(ty);
+ if is_type_diagnostic_item(cx, ty, sym!(vec_type));
+
+ then {
+ return Some(expr);
+ }
+ }
+
+ None
+}
diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs
index c6c388ee9f0..72675c25175 100644
--- a/src/lintlist/mod.rs
+++ b/src/lintlist/mod.rs
@@ -1144,6 +1144,13 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
deprecation: None,
module: "matches",
},
+ Lint {
+ name: "match_on_vec_items",
+ group: "correctness",
+ desc: "matching on vector elements can panic",
+ deprecation: None,
+ module: "match_on_vec_items",
+ },
Lint {
name: "match_overlapping_arm",
group: "style",
diff --git a/tests/ui/match_on_vec_items.rs b/tests/ui/match_on_vec_items.rs
new file mode 100644
index 00000000000..0bb39d77e46
--- /dev/null
+++ b/tests/ui/match_on_vec_items.rs
@@ -0,0 +1,130 @@
+#![warn(clippy::match_on_vec_items)]
+
+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;
+
+ // Lint, may panic
+ match arr[idx] {
+ 0 => println!("0"),
+ 1 => println!("1"),
+ num => {},
+ }
+
+ // Lint, may panic
+ 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;
+
+ // Lint, may panic
+ match arr[idx] {
+ 0 => println!("0"),
+ 1 => println!("1"),
+ _ => println!("Hello, World!"),
+ }
+
+ // Lint, may panic
+ match arr[range] {
+ [0, 1] => println!("0 1"),
+ [1, 2] => println!("1 2"),
+ _ => println!("Hello, World!"),
+ }
+}
+
+fn match_vec_ref() {
+ let arr = &vec![0, 1, 2, 3];
+ let range = 1..3;
+ let idx = 3;
+
+ // 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_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"),
+ _ => {},
+ }
+}
+
+fn main() {
+ match_with_wildcard();
+ match_without_wildcard();
+ match_wildcard_and_action();
+ match_vec_ref();
+ match_with_get();
+ match_with_array();
+}
diff --git a/tests/ui/match_on_vec_items.stderr b/tests/ui/match_on_vec_items.stderr
new file mode 100644
index 00000000000..49446d715ab
--- /dev/null
+++ b/tests/ui/match_on_vec_items.stderr
@@ -0,0 +1,52 @@
+error: indexing into a vector may panic
+ --> $DIR/match_on_vec_items.rs:9:11
+ |
+LL | match arr[idx] {
+ | ^^^^^^^^ help: try this: `arr.get(idx)`
+ |
+ = note: `-D clippy::match-on-vec-items` implied by `-D warnings`
+
+error: indexing into a vector may panic
+ --> $DIR/match_on_vec_items.rs:16:11
+ |
+LL | match arr[range] {
+ | ^^^^^^^^^^ help: try this: `arr.get(range)`
+
+error: indexing into a vector may panic
+ --> $DIR/match_on_vec_items.rs:29:11
+ |
+LL | match arr[idx] {
+ | ^^^^^^^^ help: try this: `arr.get(idx)`
+
+error: indexing into a vector may panic
+ --> $DIR/match_on_vec_items.rs:36:11
+ |
+LL | match arr[range] {
+ | ^^^^^^^^^^ help: try this: `arr.get(range)`
+
+error: indexing into a vector may panic
+ --> $DIR/match_on_vec_items.rs:49:11
+ |
+LL | match arr[idx] {
+ | ^^^^^^^^ help: try this: `arr.get(idx)`
+
+error: indexing into a vector may panic
+ --> $DIR/match_on_vec_items.rs:56:11
+ |
+LL | match arr[range] {
+ | ^^^^^^^^^^ help: try this: `arr.get(range)`
+
+error: indexing into a vector may panic
+ --> $DIR/match_on_vec_items.rs:69:11
+ |
+LL | match arr[idx] {
+ | ^^^^^^^^ help: try this: `arr.get(idx)`
+
+error: indexing into a vector may panic
+ --> $DIR/match_on_vec_items.rs:76:11
+ |
+LL | match arr[range] {
+ | ^^^^^^^^^^ help: try this: `arr.get(range)`
+
+error: aborting due to 8 previous errors
+