Also suggest .copied() when .clone() is called on a Copy type

Author: Manishearth

clippy_lints/src/map_clone.rs

@@ -1,6 +1,6 @@
 use crate::utils::paths;
 use crate::utils::{
-    in_macro, match_trait_method, match_type, remove_blocks, snippet_with_applicability, span_lint_and_sugg,
+    in_macro, match_trait_method, match_type, remove_blocks, snippet_with_applicability, span_lint_and_sugg, is_copy
 };
 use if_chain::if_chain;
 use rustc::hir;
@@ -88,8 +88,9 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
                                     && match_trait_method(cx, closure_expr, &paths::CLONE_TRAIT) {
 
                                     let obj_ty = cx.tables.expr_ty(&obj[0]);
-                                    if let ty::Ref(..) = obj_ty.sty {
-                                        lint(cx, e.span, args[0].span, false);
+                                    if let ty::Ref(_, ty, _) = obj_ty.sty {
+                                        let copy = is_copy(cx, ty);
+                                        lint(cx, e.span, args[0].span, copy);
                                     } else {
                                         lint_needless_cloning(cx, e.span, args[0].span);
                                     }

tests/ui/map_clone.fixed

@@ -11,6 +11,7 @@ fn main() {
     let _: Vec<String> = vec![String::new()].iter().cloned().collect();
     let _: Vec<u32> = vec![42, 43].iter().copied().collect();
     let _: Option<u64> = Some(Box::new(16)).map(|b| *b);
+    let _: Vec<u8> = vec![1; 6].iter().copied().collect();
 
     // Don't lint these
     let v = vec![5_i8; 6];

tests/ui/map_clone.rs

@@ -11,6 +11,7 @@ fn main() {
     let _: Vec<String> = vec![String::new()].iter().map(|x| x.clone()).collect();
     let _: Vec<u32> = vec![42, 43].iter().map(|&x| x).collect();
     let _: Option<u64> = Some(Box::new(16)).map(|b| *b);
+    let _: Vec<u8> = vec![1; 6].iter().map(|x| x.clone()).collect();
 
     // Don't lint these
     let v = vec![5_i8; 6];

tests/ui/map_clone.stderr

@@ -18,11 +18,17 @@ error: You are using an explicit closure for copying elements
 LL |     let _: Vec<u32> = vec![42, 43].iter().map(|&x| x).collect();
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `copied` method: `vec![42, 43].iter().copied()`
 
+error: You are using an explicit closure for copying elements
+  --> $DIR/map_clone.rs:14:22
+   |
+LL |     let _: Vec<u8> = vec![1; 6].iter().map(|x| x.clone()).collect();
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `copied` method: `vec![1; 6].iter().copied()`
+
 error: You are needlessly cloning iterator elements
-  --> $DIR/map_clone.rs:24:29
+  --> $DIR/map_clone.rs:25:29
    |
 LL |     let _ = std::env::args().map(|v| v.clone());
    |                             ^^^^^^^^^^^^^^^^^^^ help: Remove the map call
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors