Rollup merge of rust-lang#4764 - chansuke:fix_checked_abs, r=flip1995

Allow casts from the result of `checked_abs` to unsigned

Fixes rust-lang#4743.

clippy_lints/src/types.rs

@@ -1020,12 +1020,12 @@ fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_fro
         }
     }
 
-    // don't lint for the result of `abs`
+    // don't lint for the result of `abs` & `checked_abs`
     // `abs` is an inherent impl of `i{N}`, so a method call with ident `abs` will always
     // resolve to that spesific method
     if_chain! {
         if let ExprKind::MethodCall(ref path, _, _) = op.kind;
-        if path.ident.name.as_str() == "abs";
+        if ["abs", "checked_abs"].contains(path.ident.name);
         then {
             return
         }

tests/ui/cast.rs

@@ -47,4 +47,9 @@ fn main() {
     (-1i32).abs() as u32;
     (-1i64).abs() as u64;
     (-1isize).abs() as usize;
+    (-1i8).checked_abs().unwrap() as u8;
+    (-1i16).checked_abs().unwrap() as u16;
+    (-1i32).checked_abs().unwrap() as u32;
+    (-1i64).checked_abs().unwrap() as u64;
+    (-1isize).checked_abs().unwrap() as usize;
 }