Auto merge of #5997 - giraffate:fix_fp_about_clone_in_same_item_push, r=ebroto

Fix FP in `same_item_push`

Don't emit a lint when the pushed item doesn't have Clone trait

Fix #5979

changelog: Fix FP in `same_item_push` not to emit a lint when the pushed item doesn't have Clone trait

clippy_lints/src/loops.rs

@@ -1140,6 +1140,14 @@ fn detect_same_item_push<'tcx>(
     walk_expr(&mut same_item_push_visitor, body);
     if same_item_push_visitor.should_lint {
         if let Some((vec, pushed_item)) = same_item_push_visitor.vec_push {
+            let vec_ty = cx.typeck_results().expr_ty(vec);
+            let ty = vec_ty.walk().nth(1).unwrap().expect_ty();
+            if cx
+                .tcx
+                .lang_items()
+                .clone_trait()
+                .map_or(false, |id| implements_trait(cx, ty, id, &[]))
+            {
                 // Make sure that the push does not involve possibly mutating values
                 if let PatKind::Wild = pat.kind {
                     let vec_str = snippet_with_macro_callsite(cx, vec.span, "");
@@ -1182,6 +1190,7 @@ fn detect_same_item_push<'tcx>(
             }
         }
     }
+}
 
 /// Checks for looping over a range and then indexing a sequence with it.
 /// The iteratee must be a range literal.

tests/ui/same_item_push.rs

@@ -94,4 +94,21 @@ fn main() {
         vec13.push(item);
         item += 10;
     }
+
+    // Fix #5979
+    let mut vec14: Vec<std::fs::File> = Vec::new();
+    for _ in 0..10 {
+        vec14.push(std::fs::File::open("foobar").unwrap());
+    }
+    // Fix #5979
+    #[derive(Clone)]
+    struct S {}
+
+    trait T {}
+    impl T for S {}
+
+    let mut vec15: Vec<Box<dyn T>> = Vec::new();
+    for _ in 0..10 {
+        vec15.push(Box::new(S {}));
+    }
 }