Removed unnecessary code, added support for vector references

4 files changed, 94 insertions, 71 deletions

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/match_vec_item.rs b/clippy_lints/src/match_vec_item.rs
index 7ea5a24abbd..07121dedefe 100644
--- a/clippy_lints/src/match_vec_item.rs
+++ b/clippy_lints/src/match_vec_item.rs
@@ -1,9 +1,9 @@
-use crate::utils::{is_wild, span_lint_and_help};
+use crate::utils::{is_type_diagnostic_item, snippet_with_applicability, span_lint_and_sugg, walk_ptrs_ty};
 use if_chain::if_chain;
-use rustc_hir::{Arm, Expr, ExprKind, MatchSource};
+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_middle::ty::{self, AdtDef};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 declare_clippy_lint! {
@@ -48,64 +48,41 @@ 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);
+            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 {
-                span_lint_and_help(
+                let mut applicability = Applicability::MaybeIncorrect;
+                span_lint_and_sugg(
                     cx,
                     MATCH_VEC_ITEM,
-                    expr.span,
-                    "indexing vector may panic",
-                    None,
-                    "consider using `get(..)` instead.",
+                    match_expr.span,
+                    "indexing vector may panic. Consider using `get`",
+                    "try this",
+                    format!(
+                        "{}.get({})",
+                        snippet_with_applicability(cx, vec.span, "..", &mut applicability),
+                        snippet_with_applicability(cx, idx.span, "..", &mut applicability)
+                    ),
+                    applicability
                 );
             }
         }
     }
 }
 
-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 {
+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);
-        if let ty::Adt(def, _) = ty.kind;
-        if is_vec(cx, def);
+        let ty = walk_ptrs_ty(ty);
+        if is_type_diagnostic_item(cx, ty, sym!(vec_type));
 
         then {
-            return true;
+            return Some(expr);
         }
     }
 
-    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,
-    }
+    None
 }
diff --git a/tests/ui/match_vec_item.rs b/tests/ui/match_vec_item.rs
index 8e7c098d75c..d00d0bc2fe5 100644
--- a/tests/ui/match_vec_item.rs
+++ b/tests/ui/match_vec_item.rs
@@ -4,6 +4,7 @@ fn main() {
     match_with_wildcard();
     match_without_wildcard();
     match_wildcard_and_action();
+    match_vec_ref();
     match_with_get();
     match_with_array();
 }
@@ -33,14 +34,14 @@ fn match_without_wildcard() {
     let range = 1..3;
     let idx = 2;
 
-    // Ok
+    // Lint, may panic
     match arr[idx] {
         0 => println!("0"),
         1 => println!("1"),
         num => {},
     }
 
-    // Ok
+    // Lint, may panic
     match arr[range] {
         [0, 1] => println!("0 1"),
         [1, 2] => println!("1 2"),
@@ -53,14 +54,14 @@ fn match_wildcard_and_action() {
     let range = 1..3;
     let idx = 3;
 
-    // Ok
+    // Lint, may panic
     match arr[idx] {
         0 => println!("0"),
         1 => println!("1"),
         _ => println!("Hello, World!"),
     }
 
-    // Ok
+    // Lint, may panic
     match arr[range] {
         [0, 1] => println!("0 1"),
         [1, 2] => println!("1 2"),
@@ -68,6 +69,26 @@ fn match_wildcard_and_action() {
     }
 }
 
+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;
diff --git a/tests/ui/match_vec_item.stderr b/tests/ui/match_vec_item.stderr
index 2494c3143f8..2da2eaeee9b 100644
--- a/tests/ui/match_vec_item.stderr
+++ b/tests/ui/match_vec_item.stderr
@@ -1,27 +1,52 @@
-error: indexing vector may panic
-  --> $DIR/match_vec_item.rs:17:5
+error: indexing vector may panic. Consider using `get`
+  --> $DIR/match_vec_item.rs:18:11
    |
-LL | /     match arr[idx] {
-LL | |         0 => println!("0"),
-LL | |         1 => println!("1"),
-LL | |         _ => {},
-LL | |     }
-   | |_____^
+LL |     match arr[idx] {
+   |           ^^^^^^^^ help: try this: `arr.get(idx)`
    |
    = 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
+error: indexing vector may panic. Consider using `get`
+  --> $DIR/match_vec_item.rs:25:11
    |
-LL | /     match arr[range] {
-LL | |         [0, 1] => println!("0 1"),
-LL | |         [1, 2] => println!("1 2"),
-LL | |         _ => {},
-LL | |     }
-   | |_____^
+LL |     match arr[range] {
+   |           ^^^^^^^^^^ help: try this: `arr.get(range)`
+
+error: indexing vector may panic. Consider using `get`
+  --> $DIR/match_vec_item.rs:38:11
+   |
+LL |     match arr[idx] {
+   |           ^^^^^^^^ help: try this: `arr.get(idx)`
+
+error: indexing vector may panic. Consider using `get`
+  --> $DIR/match_vec_item.rs:45:11
+   |
+LL |     match arr[range] {
+   |           ^^^^^^^^^^ help: try this: `arr.get(range)`
+
+error: indexing vector may panic. Consider using `get`
+  --> $DIR/match_vec_item.rs:58:11
+   |
+LL |     match arr[idx] {
+   |           ^^^^^^^^ help: try this: `arr.get(idx)`
+
+error: indexing vector may panic. Consider using `get`
+  --> $DIR/match_vec_item.rs:65:11
+   |
+LL |     match arr[range] {
+   |           ^^^^^^^^^^ help: try this: `arr.get(range)`
+
+error: indexing vector may panic. Consider using `get`
+  --> $DIR/match_vec_item.rs:78:11
+   |
+LL |     match arr[idx] {
+   |           ^^^^^^^^ help: try this: `arr.get(idx)`
+
+error: indexing vector may panic. Consider using `get`
+  --> $DIR/match_vec_item.rs:85:11
    |
-   = help: consider using `get(..)` instead.
+LL |     match arr[range] {
+   |           ^^^^^^^^^^ help: try this: `arr.get(range)`
 
-error: aborting due to 2 previous errors
+error: aborting due to 8 previous errors