Auto merge of #3662 - mikerite:fix-498, r=oli-obk
Fix `map_clone` bad suggestion `cloned` requires that the elements of the iterator must be references. This change determines if that is the case by examining the type of the closure argument and suggesting `.cloned` only if it is a reference. When the closure argument is not a reference, it suggests removing the `map` call instead. A minor problem with this change is that the new check sometimes overlaps with the `clone_on_copy` lint. Fixes #498
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commit
1b89724b48
@ -5,6 +5,7 @@ use crate::utils::{
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use if_chain::if_chain;
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use rustc::hir;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::ty;
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use rustc::{declare_tool_lint, lint_array};
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use rustc_errors::Applicability;
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use syntax::ast::Ident;
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@ -18,9 +19,7 @@ pub struct Pass;
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///
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/// **Why is this bad?** Readability, this can be written more concisely
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///
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/// **Known problems:** Sometimes `.cloned()` requires stricter trait
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/// bound than `.map(|e| e.clone())` (which works because of the coercion).
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/// See [#498](https://github.com/rust-lang-nursery/rust-clippy/issues/498).
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/// **Known problems:** None
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///
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/// **Example:**
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///
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@ -69,19 +68,27 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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hir::PatKind::Ref(ref inner, _) => if let hir::PatKind::Binding(
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hir::BindingAnnotation::Unannotated, _, name, None
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) = inner.node {
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lint(cx, e.span, args[0].span, name, closure_expr);
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if ident_eq(name, closure_expr) {
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lint(cx, e.span, args[0].span);
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}
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},
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hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, name, None) => {
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match closure_expr.node {
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hir::ExprKind::Unary(hir::UnOp::UnDeref, ref inner) => {
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if !cx.tables.expr_ty(inner).is_box() {
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lint(cx, e.span, args[0].span, name, inner);
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if ident_eq(name, inner) && !cx.tables.expr_ty(inner).is_box() {
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lint(cx, e.span, args[0].span);
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}
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},
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hir::ExprKind::MethodCall(ref method, _, ref obj) => {
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if method.ident.as_str() == "clone"
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if ident_eq(name, &obj[0]) && method.ident.as_str() == "clone"
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&& match_trait_method(cx, closure_expr, &paths::CLONE_TRAIT) {
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lint(cx, e.span, args[0].span, name, &obj[0]);
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let obj_ty = cx.tables.expr_ty(&obj[0]);
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if let ty::Ref(..) = obj_ty.sty {
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lint(cx, e.span, args[0].span);
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} else {
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lint_needless_cloning(cx, e.span, args[0].span);
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}
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}
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},
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_ => {},
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@ -94,22 +101,38 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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}
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}
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fn lint(cx: &LateContext<'_, '_>, replace: Span, root: Span, name: Ident, path: &hir::Expr) {
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fn ident_eq(name: Ident, path: &hir::Expr) -> bool {
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if let hir::ExprKind::Path(hir::QPath::Resolved(None, ref path)) = path.node {
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if path.segments.len() == 1 && path.segments[0].ident == name {
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let mut applicability = Applicability::MachineApplicable;
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span_lint_and_sugg(
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cx,
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MAP_CLONE,
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replace,
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"You are using an explicit closure for cloning elements",
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"Consider calling the dedicated `cloned` method",
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format!(
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"{}.cloned()",
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snippet_with_applicability(cx, root, "..", &mut applicability)
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),
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applicability,
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)
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}
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path.segments.len() == 1 && path.segments[0].ident == name
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} else {
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false
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}
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}
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fn lint_needless_cloning(cx: &LateContext<'_, '_>, root: Span, receiver: Span) {
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span_lint_and_sugg(
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cx,
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MAP_CLONE,
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root.trim_start(receiver).unwrap(),
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"You are needlessly cloning iterator elements",
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"Remove the map call",
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String::new(),
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Applicability::MachineApplicable,
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)
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}
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fn lint(cx: &LateContext<'_, '_>, replace: Span, root: Span) {
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let mut applicability = Applicability::MachineApplicable;
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span_lint_and_sugg(
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cx,
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MAP_CLONE,
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replace,
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"You are using an explicit closure for cloning elements",
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"Consider calling the dedicated `cloned` method",
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format!(
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"{}.cloned()",
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snippet_with_applicability(cx, root, "..", &mut applicability)
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),
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applicability,
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)
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}
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@ -1,6 +1,7 @@
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// run-rustfix
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#![warn(clippy::all, clippy::pedantic)]
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#![allow(clippy::iter_cloned_collect)]
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#![allow(clippy::clone_on_copy)]
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#![allow(clippy::missing_docs_in_private_items)]
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fn main() {
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@ -8,4 +9,15 @@ fn main() {
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let _: Vec<String> = vec![String::new()].iter().cloned().collect();
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let _: Vec<u32> = vec![42, 43].iter().cloned().collect();
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let _: Option<u64> = Some(Box::new(16)).map(|b| *b);
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// Don't lint these
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let v = vec![5_i8; 6];
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let a = 0;
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let b = &a;
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let _ = v.iter().map(|_x| *b);
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let _ = v.iter().map(|_x| a.clone());
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let _ = v.iter().map(|&_x| a);
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// Issue #498
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let _ = std::env::args();
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}
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@ -1,6 +1,7 @@
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// run-rustfix
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#![warn(clippy::all, clippy::pedantic)]
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#![allow(clippy::iter_cloned_collect)]
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#![allow(clippy::clone_on_copy)]
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#![allow(clippy::missing_docs_in_private_items)]
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fn main() {
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@ -8,4 +9,15 @@ fn main() {
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let _: Vec<String> = vec![String::new()].iter().map(|x| x.clone()).collect();
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let _: Vec<u32> = vec![42, 43].iter().map(|&x| x).collect();
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let _: Option<u64> = Some(Box::new(16)).map(|b| *b);
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// Don't lint these
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let v = vec![5_i8; 6];
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let a = 0;
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let b = &a;
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let _ = v.iter().map(|_x| *b);
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let _ = v.iter().map(|_x| a.clone());
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let _ = v.iter().map(|&_x| a);
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// Issue #498
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let _ = std::env::args().map(|v| v.clone());
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}
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@ -1,5 +1,5 @@
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error: You are using an explicit closure for cloning elements
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--> $DIR/map_clone.rs:7:22
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--> $DIR/map_clone.rs:8:22
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LL | let _: Vec<i8> = vec![5_i8; 6].iter().map(|x| *x).collect();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `cloned` method: `vec![5_i8; 6].iter().cloned()`
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@ -7,16 +7,22 @@ LL | let _: Vec<i8> = vec![5_i8; 6].iter().map(|x| *x).collect();
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= note: `-D clippy::map-clone` implied by `-D warnings`
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error: You are using an explicit closure for cloning elements
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--> $DIR/map_clone.rs:8:26
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--> $DIR/map_clone.rs:9:26
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LL | let _: Vec<String> = vec![String::new()].iter().map(|x| x.clone()).collect();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `cloned` method: `vec![String::new()].iter().cloned()`
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error: You are using an explicit closure for cloning elements
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--> $DIR/map_clone.rs:9:23
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--> $DIR/map_clone.rs:10:23
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LL | let _: Vec<u32> = vec![42, 43].iter().map(|&x| x).collect();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Consider calling the dedicated `cloned` method: `vec![42, 43].iter().cloned()`
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error: aborting due to 3 previous errors
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error: You are needlessly cloning iterator elements
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--> $DIR/map_clone.rs:22:29
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LL | let _ = std::env::args().map(|v| v.clone());
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| ^^^^^^^^^^^^^^^^^^^ help: Remove the map call
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error: aborting due to 4 previous errors
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