Small lint update

- Changed lint category to `correctness`
- Moved main function to bottom in test file
- Added `FIXME` comment to `span_lint_and_sugg` to improve later

clippy_lints/src/match_on_vec_items.rs

@@ -1,4 +1,4 @@
-use crate::utils::{is_type_diagnostic_item, snippet_with_applicability, span_lint_and_sugg, walk_ptrs_ty};
+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};
@@ -38,7 +38,7 @@ declare_clippy_lint! {
     /// }
     /// ```
     pub MATCH_ON_VEC_ITEMS,
-    style,
+    correctness,
     "matching on vector elements can panic"
 }
 
@@ -53,19 +53,20 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MatchOnVecItems {
             if let ExprKind::Index(vec, idx) = idx_expr.kind;
 
             then {
-                let mut applicability = Applicability::MaybeIncorrect;
+                // 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 vector may panic. Consider using `get`",
+                    "indexing into a vector may panic",
                     "try this",
                     format!(
                         "{}.get({})",
-                        snippet_with_applicability(cx, vec.span, "..", &mut applicability),
-                        snippet_with_applicability(cx, idx.span, "..", &mut applicability)
+                        snippet(cx, vec.span, ".."),
+                        snippet(cx, idx.span, "..")
                     ),
-                    applicability
+                    Applicability::MaybeIncorrect
                 );
             }
         }

tests/ui/match_on_vec_items.rs

@@ -1,14 +1,5 @@
 #![warn(clippy::match_on_vec_items)]
 
-fn main() {
-    match_with_wildcard();
-    match_without_wildcard();
-    match_wildcard_and_action();
-    match_vec_ref();
-    match_with_get();
-    match_with_array();
-}
-
 fn match_with_wildcard() {
     let arr = vec![0, 1, 2, 3];
     let range = 1..3;
@@ -128,3 +119,12 @@ fn match_with_array() {
         _ => {},
     }
 }
+
+fn main() {
+    match_with_wildcard();
+    match_without_wildcard();
+    match_wildcard_and_action();
+    match_vec_ref();
+    match_with_get();
+    match_with_array();
+}

tests/ui/match_on_vec_items.stderr

@@ -1,49 +1,49 @@
-error: indexing vector may panic. Consider using `get`
-  --> $DIR/match_on_vec_items.rs:18:11
+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 vector may panic. Consider using `get`
-  --> $DIR/match_on_vec_items.rs:25:11
+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 vector may panic. Consider using `get`
-  --> $DIR/match_on_vec_items.rs:38:11
+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 vector may panic. Consider using `get`
-  --> $DIR/match_on_vec_items.rs:45:11
+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 vector may panic. Consider using `get`
-  --> $DIR/match_on_vec_items.rs:58:11
+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 vector may panic. Consider using `get`
-  --> $DIR/match_on_vec_items.rs:65:11
+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 vector may panic. Consider using `get`
-  --> $DIR/match_on_vec_items.rs:78:11
+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 vector may panic. Consider using `get`
-  --> $DIR/match_on_vec_items.rs:85:11
+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)`