new lint cast_abs_to_unsigned

Add a lint to detect cast to unsigned for abs() and suggest
unsigned_abs() to avoid panic when called on MIN.

6 files changed, 37 insertions, 5 deletions

diff --git a/tests/ui/cast.rs b/tests/ui/cast.rs
index 2e31ad3172e..cf85a5ca931 100644
--- a/tests/ui/cast.rs
+++ b/tests/ui/cast.rs
@@ -7,7 +7,7 @@
     clippy::cast_sign_loss,
     clippy::cast_possible_wrap
 )]
-#[allow(clippy::no_effect, clippy::unnecessary_operation)]
+#[allow(clippy::cast_abs_to_unsigned, clippy::no_effect, clippy::unnecessary_operation)]
 fn main() {
     // Test clippy::cast_precision_loss
     let x0 = 1i32;
diff --git a/tests/ui/cast_abs_to_unsigned.fixed b/tests/ui/cast_abs_to_unsigned.fixed
new file mode 100644
index 00000000000..4ec2465be06
--- /dev/null
+++ b/tests/ui/cast_abs_to_unsigned.fixed
@@ -0,0 +1,8 @@
+// run-rustfix
+#![warn(clippy::cast_abs_to_unsigned)]
+
+fn main() {
+    let x: i32 = -42;
+    let y: u32 = x.unsigned_abs();
+    println!("The absolute value of {} is {}", x, y);
+}
diff --git a/tests/ui/cast_abs_to_unsigned.rs b/tests/ui/cast_abs_to_unsigned.rs
new file mode 100644
index 00000000000..59b9c8c3678
--- /dev/null
+++ b/tests/ui/cast_abs_to_unsigned.rs
@@ -0,0 +1,8 @@
+// run-rustfix
+#![warn(clippy::cast_abs_to_unsigned)]
+
+fn main() {
+    let x: i32 = -42;
+    let y: u32 = x.abs() as u32;
+    println!("The absolute value of {} is {}", x, y);
+}
diff --git a/tests/ui/cast_abs_to_unsigned.stderr b/tests/ui/cast_abs_to_unsigned.stderr
new file mode 100644
index 00000000000..eb12857357a
--- /dev/null
+++ b/tests/ui/cast_abs_to_unsigned.stderr
@@ -0,0 +1,10 @@
+error: casting the result of `i32::abs()` to u32
+  --> $DIR/cast_abs_to_unsigned.rs:6:18
+   |
+LL |     let y: u32 = x.abs() as u32;
+   |                  ^^^^^^^^^^^^^^ help: replace with: `x.unsigned_abs()`
+   |
+   = note: `-D clippy::cast-abs-to-unsigned` implied by `-D warnings`
+
+error: aborting due to previous error
+
diff --git a/tests/ui/min_rust_version_attr.rs b/tests/ui/min_rust_version_attr.rs
index 7666d01ffe1..f83c3e0e281 100644
--- a/tests/ui/min_rust_version_attr.rs
+++ b/tests/ui/min_rust_version_attr.rs
@@ -150,6 +150,11 @@ fn err_expect() {
     x.err().expect("Testing expect_err");
 }
 
+fn cast_abs_to_unsigned() {
+    let x: i32 = 10;
+    assert_eq!(10u32, x.abs() as u32);
+}
+
 fn main() {
     filter_map_next();
     checked_conversion();
@@ -168,6 +173,7 @@ fn main() {
     unnest_or_patterns();
     int_from_bool();
     err_expect();
+    cast_abs_to_unsigned();
 }
 
 mod just_under_msrv {
diff --git a/tests/ui/min_rust_version_attr.stderr b/tests/ui/min_rust_version_attr.stderr
index 9ed6308f115..de225eb740d 100644
--- a/tests/ui/min_rust_version_attr.stderr
+++ b/tests/ui/min_rust_version_attr.stderr
@@ -1,12 +1,12 @@
 error: stripping a prefix manually
-  --> $DIR/min_rust_version_attr.rs:192:24
+  --> $DIR/min_rust_version_attr.rs:198:24
    |
 LL |             assert_eq!(s["hello, ".len()..].to_uppercase(), "WORLD!");
    |                        ^^^^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::manual-strip` implied by `-D warnings`
 note: the prefix was tested here
-  --> $DIR/min_rust_version_attr.rs:191:9
+  --> $DIR/min_rust_version_attr.rs:197:9
    |
 LL |         if s.starts_with("hello, ") {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -17,13 +17,13 @@ LL ~             assert_eq!(<stripped>.to_uppercase(), "WORLD!");
    |
 
 error: stripping a prefix manually
-  --> $DIR/min_rust_version_attr.rs:204:24
+  --> $DIR/min_rust_version_attr.rs:210:24
    |
 LL |             assert_eq!(s["hello, ".len()..].to_uppercase(), "WORLD!");
    |                        ^^^^^^^^^^^^^^^^^^^^
    |
 note: the prefix was tested here
-  --> $DIR/min_rust_version_attr.rs:203:9
+  --> $DIR/min_rust_version_attr.rs:209:9
    |
 LL |         if s.starts_with("hello, ") {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^