Suggest .copied() instead of .cloned() in map_clone when dealing with references

Author: Manishearth

clippy_lints/src/map_clone.rs

@@ -73,14 +73,14 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
                         hir::BindingAnnotation::Unannotated, .., name, None
                     ) = inner.node {
                         if ident_eq(name, closure_expr) {
-                            lint(cx, e.span, args[0].span);
+                            lint(cx, e.span, args[0].span, true);
                         }
                     },
                     hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, .., name, None) => {
                         match closure_expr.node {
                             hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner) => {
                                 if ident_eq(name, inner) && !cx.tables.expr_ty(inner).is_box() {
-                                    lint(cx, e.span, args[0].span);
+                                    lint(cx, e.span, args[0].span, true);
                                 }
                             },
                             hir::ExprKind::MethodCall(ref method, _, ref obj) => {
@@ -89,7 +89,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
 
                                     let obj_ty = cx.tables.expr_ty(&obj[0]);
                                     if let ty::Ref(..) = obj_ty.sty {
-                                        lint(cx, e.span, args[0].span);
+                                        lint(cx, e.span, args[0].span, false);
                                     } else {
                                         lint_needless_cloning(cx, e.span, args[0].span);
                                     }
@@ -125,18 +125,33 @@ fn lint_needless_cloning(cx: &LateContext<'_, '_>, root: Span, receiver: Span) {
     )
 }
 
-fn lint(cx: &LateContext<'_, '_>, replace: Span, root: Span) {
+fn lint(cx: &LateContext<'_, '_>, replace: Span, root: Span, copied: bool) {
     let mut applicability = Applicability::MachineApplicable;
-    span_lint_and_sugg(
-        cx,
-        MAP_CLONE,
-        replace,
-        "You are using an explicit closure for cloning elements",
-        "Consider calling the dedicated `cloned` method",
-        format!(
-            "{}.cloned()",
-            snippet_with_applicability(cx, root, "..", &mut applicability)
-        ),
-        applicability,
-    )
+    if copied {
+        span_lint_and_sugg(
+            cx,
+            MAP_CLONE,
+            replace,
+            "You are using an explicit closure for copying elements",
+            "Consider calling the dedicated `copied` method",
+            format!(
+                "{}.copied()",
+                snippet_with_applicability(cx, root, "..", &mut applicability)
+            ),
+            applicability,
+        )
+    } else {
+        span_lint_and_sugg(
+            cx,
+            MAP_CLONE,
+            replace,
+            "You are using an explicit closure for cloning elements",
+            "Consider calling the dedicated `cloned` method",
+            format!(
+                "{}.cloned()",
+                snippet_with_applicability(cx, root, "..", &mut applicability)
+            ),
+            applicability,
+        )
+    }
 }

tests/ui/map_clone.fixed

@@ -4,11 +4,12 @@
 #![allow(clippy::clone_on_copy)]
 #![allow(clippy::missing_docs_in_private_items)]
 #![allow(clippy::redundant_closure)]
+#![feature(iter_copied)]
 
 fn main() {
-    let _: Vec<i8> = vec![5_i8; 6].iter().cloned().collect();
+    let _: Vec<i8> = vec![5_i8; 6].iter().copied().collect();
     let _: Vec<String> = vec![String::new()].iter().cloned().collect();
-    let _: Vec<u32> = vec![42, 43].iter().cloned().collect();
+    let _: Vec<u32> = vec![42, 43].iter().copied().collect();
     let _: Option<u64> = Some(Box::new(16)).map(|b| *b);
 
     // Don't lint these

tests/ui/map_clone.rs

@@ -4,6 +4,7 @@
 #![allow(clippy::clone_on_copy)]
 #![allow(clippy::missing_docs_in_private_items)]
 #![allow(clippy::redundant_closure)]
+#![feature(iter_copied)]
 
 fn main() {
     let _: Vec<i8> = vec![5_i8; 6].iter().map(|x| *x).collect();

tests/ui/map_clone.stderr

@@ -1,25 +1,25 @@
-error: You are using an explicit closure for cloning elements
-  --> $DIR/map_clone.rs:9:22
+error: You are using an explicit closure for copying elements
+  --> $DIR/map_clone.rs:10:22
    |
 LL |     let _: Vec<i8> = vec![5_i8; 6].iter().map(|x| *x).collect();
-   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `cloned` method: `vec![5_i8; 6].iter().cloned()`
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `copied` method: `vec![5_i8; 6].iter().copied()`
    |
    = note: `-D clippy::map-clone` implied by `-D warnings`
 
 error: You are using an explicit closure for cloning elements
-  --> $DIR/map_clone.rs:10:26
+  --> $DIR/map_clone.rs:11:26
    |
 LL |     let _: Vec<String> = vec![String::new()].iter().map(|x| x.clone()).collect();
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `cloned` method: `vec![String::new()].iter().cloned()`
 
-error: You are using an explicit closure for cloning elements
-  --> $DIR/map_clone.rs:11:23
+error: You are using an explicit closure for copying elements
+  --> $DIR/map_clone.rs:12:23
    |
 LL |     let _: Vec<u32> = vec![42, 43].iter().map(|&x| x).collect();
-   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `cloned` method: `vec![42, 43].iter().cloned()`
+   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `copied` method: `vec![42, 43].iter().copied()`
 
 error: You are needlessly cloning iterator elements
-  --> $DIR/map_clone.rs:23:29
+  --> $DIR/map_clone.rs:24:29
    |
 LL |     let _ = std::env::args().map(|v| v.clone());
    |                             ^^^^^^^^^^^^^^^^^^^ help: Remove the map call