Merge commit '6ed6f1e6a1a8f414ba7e6d9b8222e7e5a1686e42' into clippyup

1 files changed, 47 insertions, 0 deletions

diff --git a/clippy_lints/src/methods/iter_count.rs b/clippy_lints/src/methods/iter_count.rs
new file mode 100644
index 00000000000..869440e0165
--- /dev/null
+++ b/clippy_lints/src/methods/iter_count.rs
@@ -0,0 +1,47 @@
+use crate::methods::derefs_to_slice;
+use crate::utils::{is_type_diagnostic_item, match_type, paths, snippet_with_applicability, span_lint_and_sugg};
+
+use rustc_errors::Applicability;
+use rustc_hir::Expr;
+use rustc_lint::LateContext;
+use rustc_span::sym;
+
+use super::ITER_COUNT;
+
+pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, iter_args: &'tcx [Expr<'tcx>], iter_method: &str) {
+    let ty = cx.typeck_results().expr_ty(&iter_args[0]);
+    let caller_type = if derefs_to_slice(cx, &iter_args[0], ty).is_some() {
+        "slice"
+    } else if is_type_diagnostic_item(cx, ty, sym::vec_type) {
+        "Vec"
+    } else if is_type_diagnostic_item(cx, ty, sym::vecdeque_type) {
+        "VecDeque"
+    } else if is_type_diagnostic_item(cx, ty, sym::hashset_type) {
+        "HashSet"
+    } else if is_type_diagnostic_item(cx, ty, sym::hashmap_type) {
+        "HashMap"
+    } else if match_type(cx, ty, &paths::BTREEMAP) {
+        "BTreeMap"
+    } else if match_type(cx, ty, &paths::BTREESET) {
+        "BTreeSet"
+    } else if match_type(cx, ty, &paths::LINKED_LIST) {
+        "LinkedList"
+    } else if match_type(cx, ty, &paths::BINARY_HEAP) {
+        "BinaryHeap"
+    } else {
+        return;
+    };
+    let mut applicability = Applicability::MachineApplicable;
+    span_lint_and_sugg(
+        cx,
+        ITER_COUNT,
+        expr.span,
+        &format!("called `.{}().count()` on a `{}`", iter_method, caller_type),
+        "try",
+        format!(
+            "{}.len()",
+            snippet_with_applicability(cx, iter_args[0].span, "..", &mut applicability),
+        ),
+        applicability,
+    );
+}