Also handle Result type for map_clone lint

Author: GuillaumeGomez

clippy_lints/src/methods/map_clone.rs

@@ -18,6 +18,7 @@ pub(super) fn check(cx: &LateContext<'_>, e: &hir::Expr<'_>, recv: &hir::Expr<'_
     if let Some(method_id) = cx.typeck_results().type_dependent_def_id(e.hir_id)
         && (cx.tcx.impl_of_method(method_id).map_or(false, |id| {
             is_type_diagnostic_item(cx, cx.tcx.type_of(id).instantiate_identity(), sym::Option)
+                || is_type_diagnostic_item(cx, cx.tcx.type_of(id).instantiate_identity(), sym::Result)
         }) || is_diag_trait_item(cx, method_id, sym::Iterator))
     {
         match arg.kind {

tests/ui/map_clone.fixed

@@ -70,4 +70,10 @@ fn main() {
     //~^ ERROR: you are explicitly cloning with `.map()`
     let y = x.cloned();
     //~^ ERROR: you are explicitly cloning with `.map()`
+
+    // Testing with `Result` now.
+    let x: Result<String, ()> = Ok(String::new());
+    let x = x.as_ref(); // We do this to prevent triggering the `useless_asref` lint.
+    let y = x.cloned();
+    //~^ ERROR: you are explicitly cloning with `.map()`
 }

tests/ui/map_clone.rs

@@ -70,4 +70,10 @@ fn main() {
     //~^ ERROR: you are explicitly cloning with `.map()`
     let y = x.map(String::clone);
     //~^ ERROR: you are explicitly cloning with `.map()`
+
+    // Testing with `Result` now.
+    let x: Result<String, ()> = Ok(String::new());
+    let x = x.as_ref(); // We do this to prevent triggering the `useless_asref` lint.
+    let y = x.map(|x| String::clone(x));
+    //~^ ERROR: you are explicitly cloning with `.map()`
 }

tests/ui/map_clone.stderr

@@ -55,5 +55,11 @@ error: you are explicitly cloning with `.map()`
 LL |     let y = x.map(String::clone);
    |             ^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `cloned` method: `x.cloned()`
 
-error: aborting due to 9 previous errors
+error: you are explicitly cloning with `.map()`
+  --> $DIR/map_clone.rs:77:13
+   |
+LL |     let y = x.map(|x| String::clone(x));
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `cloned` method: `x.cloned()`
+
+error: aborting due to 10 previous errors