Add 5 other container types and start testing

clippy_lints/src/methods/clear_with_drain.rs

@@ -2,6 +2,7 @@ use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::is_range_full;
 use clippy_utils::ty::is_type_diagnostic_item;
 use rustc_errors::Applicability;
+use rustc_hir as hir;
 use rustc_hir::{Expr, ExprKind, QPath};
 use rustc_lint::LateContext;
 use rustc_span::symbol::sym;
@@ -9,17 +10,37 @@ use rustc_span::Span;
 
 use super::CLEAR_WITH_DRAIN;
 
-pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, span: Span, arg: &Expr<'_>) {
-    let ty = cx.typeck_results().expr_ty(recv);
-    if is_type_diagnostic_item(cx, ty, sym::Vec)
-        && let ExprKind::Path(QPath::Resolved(None, container_path)) = recv.kind
-        && is_range_full(cx, arg, Some(container_path))
+const ACCEPTABLE_TYPES_WITH_ARG: [rustc_span::Symbol; 3] = [sym::String, sym::Vec, sym::VecDeque];
+
+const ACCEPTABLE_TYPES_WITHOUT_ARG: [rustc_span::Symbol; 3] = [sym::BinaryHeap, sym::HashMap, sym::HashSet];
+
+pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, span: Span, arg: Option<&Expr<'_>>) {
+    if let Some(arg) = arg {
+        if match_acceptable_type(cx, recv, &ACCEPTABLE_TYPES_WITH_ARG)
+            && let ExprKind::Path(QPath::Resolved(None, container_path)) = recv.kind
+            && is_range_full(cx, arg, Some(container_path))
+        {
+            suggest(cx, expr, recv, span);
+        }
+    } else if match_acceptable_type(cx, recv, &ACCEPTABLE_TYPES_WITHOUT_ARG) {
+        suggest(cx, expr, recv, span);
+    }
+}
+
+fn match_acceptable_type(cx: &LateContext<'_>, expr: &hir::Expr<'_>, types: &[rustc_span::Symbol]) -> bool {
+    let expr_ty = cx.typeck_results().expr_ty(expr).peel_refs();
+    types.iter().any(|&ty| is_type_diagnostic_item(cx, expr_ty, ty))
+}
+
+fn suggest(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, span: Span) {
+    if let Some(adt) = cx.typeck_results().expr_ty(recv).ty_adt_def()
+        && let Some(ty_name) = cx.tcx.get_diagnostic_name(adt.did())
     {
         span_lint_and_sugg(
             cx,
             CLEAR_WITH_DRAIN,
             span.with_hi(expr.span.hi()),
-            "`drain` used to clear a `Vec`",
+            &format!("`drain` used to clear a `{}`", ty_name),
             "try",
             "clear()".to_string(),
             Applicability::MachineApplicable,

clippy_lints/src/methods/mod.rs

@@ -3589,12 +3589,13 @@ impl Methods {
                     Some(("bytes", recv2, [], _, _)) => bytes_count_to_len::check(cx, expr, recv, recv2),
                     _ => {},
                 },
-                ("drain", [arg]) => {
-                if let Node::Stmt(Stmt { hir_id: _, kind, .. }) = cx.tcx.hir().get_parent(expr.hir_id)
-                    && matches!(kind, StmtKind::Semi(_))
+                ("drain", ..) => {
+                    if let Node::Stmt(Stmt { hir_id: _, kind, .. }) = cx.tcx.hir().get_parent(expr.hir_id)
+                        && matches!(kind, StmtKind::Semi(_))
+                        && args.len() <= 1
                     {
-                        clear_with_drain::check(cx, expr, recv, span, arg);
-                    } else {
+                        clear_with_drain::check(cx, expr, recv, span, args.first());
+                    } else if let [arg] = args {
                         iter_with_drain::check(cx, expr, recv, span, arg);
                     }
                 },

tests/ui/clear_with_drain.fixed

@@ -2,6 +2,11 @@
 #![allow(unused)]
 #![warn(clippy::clear_with_drain)]
 
+use std::collections::BinaryHeap;
+use std::collections::HashMap;
+use std::collections::HashSet;
+use std::collections::VecDeque;
+
 fn range() {
     let mut v = vec![1, 2, 3];
     let iter = v.drain(0..v.len()); // Yay
@@ -83,4 +88,22 @@ fn partial_drains() {
     let w: Vec<i8> = v.drain(1..v.len() - 1).collect(); // Yay
 }
 
-fn main() {}
+fn main() {
+    let mut deque: VecDeque<_> = [1, 2, 3].into();
+    deque.clear();
+
+    let mut set = HashSet::from([1, 2, 3]);
+    set.clear();
+
+    let mut a = HashMap::new();
+    a.insert(1, "a");
+    a.insert(2, "b");
+    a.clear();
+
+    let mut heap = BinaryHeap::from([1, 3]);
+    heap.clear();
+
+    // Not firing for now because `String` is not reckognized by `is_type_diagnostic_item`
+    let mut s = String::from("α is alpha, β is beta");
+    s.drain(..);
+}

tests/ui/clear_with_drain.rs

@@ -2,6 +2,11 @@
 #![allow(unused)]
 #![warn(clippy::clear_with_drain)]
 
+use std::collections::BinaryHeap;
+use std::collections::HashMap;
+use std::collections::HashSet;
+use std::collections::VecDeque;
+
 fn range() {
     let mut v = vec![1, 2, 3];
     let iter = v.drain(0..v.len()); // Yay
@@ -83,4 +88,22 @@ fn partial_drains() {
     let w: Vec<i8> = v.drain(1..v.len() - 1).collect(); // Yay
 }
 
-fn main() {}
+fn main() {
+    let mut deque: VecDeque<_> = [1, 2, 3].into();
+    deque.drain(..);
+
+    let mut set = HashSet::from([1, 2, 3]);
+    set.drain();
+
+    let mut a = HashMap::new();
+    a.insert(1, "a");
+    a.insert(2, "b");
+    a.drain();
+
+    let mut heap = BinaryHeap::from([1, 3]);
+    heap.drain();
+
+    // Not firing for now because `String` is not reckognized by `is_type_diagnostic_item`
+    let mut s = String::from("α is alpha, β is beta");
+    s.drain(..);
+}

tests/ui/clear_with_drain.stderr

@@ -1,5 +1,5 @@
 error: `drain` used to clear a `Vec`
-  --> $DIR/clear_with_drain.rs:17:7
+  --> $DIR/clear_with_drain.rs:22:7
    |
 LL |     v.drain(0..v.len()); // Nay
    |       ^^^^^^^^^^^^^^^^^ help: try: `clear()`
@@ -7,34 +7,58 @@ LL |     v.drain(0..v.len()); // Nay
    = note: `-D clippy::clear-with-drain` implied by `-D warnings`
 
 error: `drain` used to clear a `Vec`
-  --> $DIR/clear_with_drain.rs:20:7
+  --> $DIR/clear_with_drain.rs:25:7
    |
 LL |     v.drain(usize::MIN..v.len()); // Nay
    |       ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `clear()`
 
 error: `drain` used to clear a `Vec`
-  --> $DIR/clear_with_drain.rs:35:7
+  --> $DIR/clear_with_drain.rs:40:7
    |
 LL |     v.drain(0..); // Nay
    |       ^^^^^^^^^^ help: try: `clear()`
 
 error: `drain` used to clear a `Vec`
-  --> $DIR/clear_with_drain.rs:38:7
+  --> $DIR/clear_with_drain.rs:43:7
    |
 LL |     v.drain(usize::MIN..); // Nay
    |       ^^^^^^^^^^^^^^^^^^^ help: try: `clear()`
 
 error: `drain` used to clear a `Vec`
-  --> $DIR/clear_with_drain.rs:52:7
+  --> $DIR/clear_with_drain.rs:57:7
    |
 LL |     v.drain(..); // Nay
    |       ^^^^^^^^^ help: try: `clear()`
 
 error: `drain` used to clear a `Vec`
-  --> $DIR/clear_with_drain.rs:66:7
+  --> $DIR/clear_with_drain.rs:71:7
    |
 LL |     v.drain(..v.len()); // Nay
    |       ^^^^^^^^^^^^^^^^ help: try: `clear()`
 
-error: aborting due to 6 previous errors
+error: `drain` used to clear a `VecDeque`
+  --> $DIR/clear_with_drain.rs:93:11
+   |
+LL |     deque.drain(..);
+   |           ^^^^^^^^^ help: try: `clear()`
+
+error: `drain` used to clear a `HashSet`
+  --> $DIR/clear_with_drain.rs:96:9
+   |
+LL |     set.drain();
+   |         ^^^^^^^ help: try: `clear()`
+
+error: `drain` used to clear a `HashMap`
+  --> $DIR/clear_with_drain.rs:101:7
+   |
+LL |     a.drain();
+   |       ^^^^^^^ help: try: `clear()`
+
+error: `drain` used to clear a `BinaryHeap`
+  --> $DIR/clear_with_drain.rs:104:10
+   |
+LL |     heap.drain();
+   |          ^^^^^^^ help: try: `clear()`
+
+error: aborting due to 10 previous errors