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Auto merge of #3970 - rust-lang:map_copied, r=flip1995
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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
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@bors
bors committed Apr 16, 2019
2 parents fbb3a47 + e9cde41 commit 3e8d992
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Showing 4 changed files with 56 additions and 21 deletions.
57 changes: 38 additions & 19 deletions clippy_lints/src/map_clone.rs
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Original file line number Diff line number Diff line change
@@ -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;
Expand Down Expand Up @@ -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);
Expand All @@ -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);
}
Expand Down Expand Up @@ -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,
)
}
}
2 changes: 2 additions & 0 deletions tests/ui/map_clone.fixed
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Original file line number Diff line number Diff line change
Expand Up @@ -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];
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/map_clone.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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];
Expand Down
16 changes: 14 additions & 2 deletions tests/ui/map_clone.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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

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