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Auto merge of #5522 - CrazyRoka:match_vec_item, r=phansch
New lint `match_vec_item` Added new lint to warn a match on index item which can panic. It's always better to use `get(..)` instead. Closes #5500 changelog: New lint `match_on_vec_items`
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -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]); | ||
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||
| 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 | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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||
| 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 | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -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"), | ||
| _ => {}, | ||
| } | ||
| } | ||
|
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||
| fn match_without_wildcard() { | ||
| let arr = vec![0, 1, 2, 3]; | ||
| let range = 1..3; | ||
| let idx = 2; | ||
|
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||
| // 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 @ ..] => {}, | ||
| } | ||
| } | ||
|
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||
| fn match_wildcard_and_action() { | ||
| let arr = vec![0, 1, 2, 3]; | ||
| let range = 1..3; | ||
| let idx = 3; | ||
|
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||
| // Lint, may panic | ||
| match arr[idx] { | ||
| 0 => println!("0"), | ||
| 1 => println!("1"), | ||
| _ => println!("Hello, World!"), | ||
| } | ||
|
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||
| // Lint, may panic | ||
| match arr[range] { | ||
| [0, 1] => println!("0 1"), | ||
| [1, 2] => println!("1 2"), | ||
| _ => println!("Hello, World!"), | ||
| } | ||
| } | ||
|
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||
| fn match_vec_ref() { | ||
| let arr = &vec![0, 1, 2, 3]; | ||
| let range = 1..3; | ||
| let idx = 3; | ||
|
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||
| // Lint, may panic | ||
| match arr[idx] { | ||
| 0 => println!("0"), | ||
| 1 => println!("1"), | ||
| _ => {}, | ||
| } | ||
|
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||
| // Lint, may panic | ||
| match arr[range] { | ||
| [0, 1] => println!("0 1"), | ||
| [1, 2] => println!("1 2"), | ||
| _ => {}, | ||
| } | ||
| } | ||
|
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||
| fn match_with_get() { | ||
| let arr = vec![0, 1, 2, 3]; | ||
| let range = 1..3; | ||
| let idx = 3; | ||
|
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||
| // Ok | ||
| match arr.get(idx) { | ||
| Some(0) => println!("0"), | ||
| Some(1) => println!("1"), | ||
| _ => {}, | ||
| } | ||
|
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||
| // Ok | ||
| match arr.get(range) { | ||
| Some(&[0, 1]) => println!("0 1"), | ||
| Some(&[1, 2]) => println!("1 2"), | ||
| _ => {}, | ||
| } | ||
| } | ||
|
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||
| fn match_with_array() { | ||
| let arr = [0, 1, 2, 3]; | ||
| let range = 1..3; | ||
| let idx = 3; | ||
|
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||
| // Ok | ||
| match arr[idx] { | ||
| 0 => println!("0"), | ||
| 1 => println!("1"), | ||
| _ => {}, | ||
| } | ||
|
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||
| // Ok | ||
| match arr[range] { | ||
| [0, 1] => println!("0 1"), | ||
| [1, 2] => println!("1 2"), | ||
| _ => {}, | ||
| } | ||
| } | ||
|
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||
| fn main() { | ||
| match_with_wildcard(); | ||
| match_without_wildcard(); | ||
| match_wildcard_and_action(); | ||
| match_vec_ref(); | ||
| match_with_get(); | ||
| match_with_array(); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -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` | ||
|
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||
| 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)` | ||
|
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||
| 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)` | ||
|
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||
| 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)` | ||
|
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||
| 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)` | ||
|
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||
| 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)` | ||
|
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||
| 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)` | ||
|
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||
| 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)` | ||
|
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||
| error: aborting due to 8 previous errors | ||
|
|