Make manual_swap autofixable

Author: flip1995

clippy_lints/src/swap.rs

@@ -1,7 +1,7 @@
 use crate::utils::sugg::Sugg;
 use crate::utils::{
-    differing_macro_contexts, is_type_diagnostic_item, match_type, paths, snippet, span_lint_and_then, walk_ptrs_ty,
-    SpanlessEq,
+    differing_macro_contexts, is_type_diagnostic_item, match_type, paths, snippet_with_applicability,
+    span_lint_and_then, walk_ptrs_ty, SpanlessEq,
 };
 use if_chain::if_chain;
 use matches::matches;
@@ -105,8 +105,9 @@ fn check_manual_swap(cx: &LateContext<'_, '_>, block: &Block) {
                     }
                 }
 
-                let slice = check_for_slice(cx, lhs1, lhs2);
+                let mut applicability = Applicability::MachineApplicable;
 
+                let slice = check_for_slice(cx, lhs1, lhs2);
                 let (replace, what, sugg) = if let Slice::NotSwappable = slice {
                     return;
                 } else if let Slice::Swappable(slice, idx1, idx2) = slice {
@@ -117,8 +118,8 @@ fn check_manual_swap(cx: &LateContext<'_, '_>, block: &Block) {
                             format!(
                                 "{}.swap({}, {})",
                                 slice.maybe_par(),
-                                snippet(cx, idx1.span, ".."),
-                                snippet(cx, idx2.span, ".."),
+                                snippet_with_applicability(cx, idx1.span, "..", &mut applicability),
+                                snippet_with_applicability(cx, idx2.span, "..", &mut applicability),
                             ),
                         )
                     } else {
@@ -147,7 +148,7 @@ fn check_manual_swap(cx: &LateContext<'_, '_>, block: &Block) {
                                 span,
                                 "try",
                                 sugg,
-                                Applicability::Unspecified,
+                                applicability,
                             );
 
                             if replace {

tests/ui/swap.fixed

@@ -0,0 +1,83 @@
+// run-rustfix
+
+#![warn(clippy::all)]
+#![allow(
+    clippy::blacklisted_name,
+    clippy::no_effect,
+    clippy::redundant_clone,
+    redundant_semicolon,
+    unused_assignments
+)]
+
+struct Foo(u32);
+
+#[derive(Clone)]
+struct Bar {
+    a: u32,
+    b: u32,
+}
+
+fn field() {
+    let mut bar = Bar { a: 1, b: 2 };
+
+    let temp = bar.a;
+    bar.a = bar.b;
+    bar.b = temp;
+
+    let mut baz = vec![bar.clone(), bar.clone()];
+    let temp = baz[0].a;
+    baz[0].a = baz[1].a;
+    baz[1].a = temp;
+}
+
+fn array() {
+    let mut foo = [1, 2];
+    foo.swap(0, 1);
+
+    foo.swap(0, 1);
+}
+
+fn slice() {
+    let foo = &mut [1, 2];
+    foo.swap(0, 1);
+
+    foo.swap(0, 1);
+}
+
+fn unswappable_slice() {
+    let foo = &mut [vec![1, 2], vec![3, 4]];
+    let temp = foo[0][1];
+    foo[0][1] = foo[1][0];
+    foo[1][0] = temp;
+
+    // swap(foo[0][1], foo[1][0]) would fail
+}
+
+fn vec() {
+    let mut foo = vec![1, 2];
+    foo.swap(0, 1);
+
+    foo.swap(0, 1);
+}
+
+#[rustfmt::skip]
+fn main() {
+    field();
+    array();
+    slice();
+    unswappable_slice();
+    vec();
+
+    let mut a = 42;
+    let mut b = 1337;
+
+    std::mem::swap(&mut a, &mut b);
+
+    ; std::mem::swap(&mut a, &mut b);
+
+    let mut c = Foo(42);
+
+    std::mem::swap(&mut c.0, &mut a);
+
+    ; std::mem::swap(&mut c.0, &mut a);
+}

tests/ui/swap.rs

@@ -1,3 +1,5 @@
+// run-rustfix
+
 #![warn(clippy::all)]
 #![allow(
     clippy::blacklisted_name,
@@ -69,6 +71,7 @@ fn main() {
     field();
     array();
     slice();
+    unswappable_slice();
     vec();
 
     let mut a = 42;

tests/ui/swap.stderr

@@ -1,5 +1,5 @@
 error: this looks like you are swapping elements of `foo` manually
-  --> $DIR/swap.rs:33:5
+  --> $DIR/swap.rs:35:5
    |
 LL | /     let temp = foo[0];
 LL | |     foo[0] = foo[1];
@@ -9,23 +9,23 @@ LL | |     foo[1] = temp;
    = note: `-D clippy::manual-swap` implied by `-D warnings`
 
 error: this looks like you are swapping elements of `foo` manually
-  --> $DIR/swap.rs:42:5
+  --> $DIR/swap.rs:44:5
    |
 LL | /     let temp = foo[0];
 LL | |     foo[0] = foo[1];
 LL | |     foo[1] = temp;
    | |_________________^ help: try: `foo.swap(0, 1)`
 
 error: this looks like you are swapping elements of `foo` manually
-  --> $DIR/swap.rs:60:5
+  --> $DIR/swap.rs:62:5
    |
 LL | /     let temp = foo[0];
 LL | |     foo[0] = foo[1];
 LL | |     foo[1] = temp;
    | |_________________^ help: try: `foo.swap(0, 1)`
 
 error: this looks like you are swapping `a` and `b` manually
-  --> $DIR/swap.rs:80:7
+  --> $DIR/swap.rs:83:7
    |
 LL |       ; let t = a;
    |  _______^
@@ -36,7 +36,7 @@ LL | |     b = t;
    = note: or maybe you should use `std::mem::replace`?
 
 error: this looks like you are swapping `c.0` and `a` manually
-  --> $DIR/swap.rs:89:7
+  --> $DIR/swap.rs:92:7
    |
 LL |       ; let t = c.0;
    |  _______^
@@ -47,7 +47,7 @@ LL | |     a = t;
    = note: or maybe you should use `std::mem::replace`?
 
 error: this looks like you are trying to swap `a` and `b`
-  --> $DIR/swap.rs:77:5
+  --> $DIR/swap.rs:80:5
    |
 LL | /     a = b;
 LL | |     b = a;
@@ -57,7 +57,7 @@ LL | |     b = a;
    = note: or maybe you should use `std::mem::replace`?
 
 error: this looks like you are trying to swap `c.0` and `a`
-  --> $DIR/swap.rs:86:5
+  --> $DIR/swap.rs:89:5
    |
 LL | /     c.0 = a;
 LL | |     a = c.0;