fix: map_unwrap_or suggests wrongly for empty slice

Author: profetia

clippy_lints/src/methods/map_unwrap_or.rs

@@ -36,7 +36,8 @@ pub(super) fn check<'tcx>(
 
     // lint if the caller of `map()` is an `Option`
     if is_option || is_result {
-        if !is_copy(cx, cx.typeck_results().expr_ty(unwrap_arg)) {
+        let unwrap_arg_ty = cx.typeck_results().expr_ty(unwrap_arg);
+        if !is_copy(cx, unwrap_arg_ty) {
             // Replacing `.map(<f>).unwrap_or(<a>)` with `.map_or(<a>, <f>)` can sometimes lead to
             // borrowck errors, see #10579 for one such instance.
             // In particular, if `a` causes a move and `f` references that moved binding, then we cannot lint:
@@ -124,6 +125,13 @@ pub(super) fn check<'tcx>(
                     } else if suggest_is_some_and {
                         if is_result { "is_ok_and" } else { "is_some_and" }
                     } else {
+                        let unwrap_arg_ty = unwrap_arg_ty.peel_refs();
+                        if unwrap_arg_ty.is_array()
+                            && let unwrap_arg_ty_adj = cx.typeck_results().expr_ty_adjusted(unwrap_arg).peel_refs()
+                            && unwrap_arg_ty_adj.is_slice()
+                        {
+                            return;
+                        }
                         "map_or"
                     }),
                 ),

tests/ui/map_unwrap_or.rs

@@ -156,3 +156,11 @@ mod issue_10579 {
         println!("{y:?}");
     }
 }
+
+fn issue15752() {
+    struct Foo<'a>(&'a [u32]);
+
+    let x = Some(Foo(&[1, 2, 3]));
+    x.map(|y| y.0).unwrap_or(&[]);
+    //~^ map_unwrap_or
+}

tests/ui/map_unwrap_or.stderr

@@ -199,5 +199,11 @@ LL -     let _ = opt.map(|x| x > 5).unwrap_or(false);
 LL +     let _ = opt.is_some_and(|x| x > 5);
    |
 
-error: aborting due to 15 previous errors
+error: called `map(<f>).unwrap_or(<a>)` on an `Option` value
+  --> tests/ui/map_unwrap_or.rs:164:5
+   |
+LL |     x.map(|y| y.0).unwrap_or(&[]);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 16 previous errors