Auto merge of #3970 - rust-lang:map_copied, r=flip1995

Suggest .copied() instead of .cloned() in map_clone where applicable

partial fix for #3958

changelog: Improve suggestion in `map_clone` to suggest `.copied()` where applicable

Author: bors

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, is_copy, match_trait_method, match_type, remove_blocks, snippet_with_applicability, span_lint_and_sugg,
 };
 use if_chain::if_chain;
 use rustc::hir;
@@ -63,7 +63,8 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
             if args.len() == 2;
             if method.ident.as_str() == "map";
             let ty = cx.tables.expr_ty(&args[0]);
-            if match_type(cx, ty, &paths::OPTION) || match_trait_method(cx, e, &paths::ITERATOR);
+            let is_option = match_type(cx, ty, &paths::OPTION);
+            if is_option || match_trait_method(cx, e, &paths::ITERATOR);
             if let hir::ExprKind::Closure(_, _, body_id, _, _) = args[1].node;
             let closure_body = cx.tcx.hir().body(body_id);
             let closure_expr = remove_blocks(&closure_body.value);
@@ -73,23 +74,26 @@ 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);
+                            // FIXME When Iterator::copied() stabilizes we can remove is_option
+                            // from here and the other lint() calls
+                            lint(cx, e.span, args[0].span, is_option);
                         }
                     },
                     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, is_option);
                                 }
                             },
                             hir::ExprKind::MethodCall(ref method, _, ref obj) => {
                                 if ident_eq(name, &obj[0]) && method.ident.as_str() == "clone"
                                     && 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);
+                                    if let ty::Ref(_, ty, _) = obj_ty.sty {
+                                        let copy = is_copy(cx, ty);
+                                        lint(cx, e.span, args[0].span, is_option && copy);
                                     } else {
                                         lint_needless_cloning(cx, e.span, args[0].span);
                                     }
@@ -125,18 +129,33 @@ 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

@@ -10,6 +10,8 @@ fn main() {
     let _: Vec<String> = vec![String::new()].iter().cloned().collect();
     let _: Vec<u32> = vec![42, 43].iter().cloned().collect();
     let _: Option<u64> = Some(Box::new(16)).map(|b| *b);
+    let _: Option<u64> = Some(&16).copied();
+    let _: Option<u8> = Some(&1).copied();
 
     // Don't lint these
     let v = vec![5_i8; 6];

tests/ui/map_clone.rs

@@ -10,6 +10,8 @@ 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 _: Option<u64> = Some(&16).map(|b| *b);
+    let _: Option<u8> = Some(&1).map(|x| x.clone());
 
     // Don't lint these
     let v = vec![5_i8; 6];

tests/ui/map_clone.stderr

@@ -18,11 +18,23 @@ error: You are using an explicit closure for cloning elements
 LL |     let _: Vec<u32> = vec![42, 43].iter().map(|&x| x).collect();
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `cloned` method: `vec![42, 43].iter().cloned()`
 
+error: You are using an explicit closure for copying elements
+  --> $DIR/map_clone.rs:13:26
+   |
+LL |     let _: Option<u64> = Some(&16).map(|b| *b);
+   |                          ^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `copied` method: `Some(&16).copied()`
+
+error: You are using an explicit closure for copying elements
+  --> $DIR/map_clone.rs:14:25
+   |
+LL |     let _: Option<u8> = Some(&1).map(|x| x.clone());
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `copied` method: `Some(&1).copied()`
+
 error: You are needlessly cloning iterator elements
-  --> $DIR/map_clone.rs:23:29
+  --> $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 6 previous errors