Extract never-like into clippy_utils

Author: Centri3

clippy_lints/src/methods/unwrap_expect_used.rs

@@ -1,5 +1,5 @@
-use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::ty::{is_never_like, is_type_diagnostic_item};
 use clippy_utils::{is_in_cfg_test, is_in_test_function, is_lint_allowed};
 use rustc_hir::Expr;
 use rustc_lint::{LateContext, Lint};
@@ -32,7 +32,8 @@ impl Variant {
     }
 }
 
-/// lint use of `unwrap()` or `unwrap_err` for `Result` and `unwrap()` for `Option`.
+/// Lint usage of `unwrap` or `unwrap_err` for `Result` and `unwrap()` for `Option` (and their
+/// `expect` counterparts).
 pub(super) fn check(
     cx: &LateContext<'_>,
     expr: &Expr<'_>,
@@ -49,10 +50,7 @@ pub(super) fn check(
         && let ty::Adt(_, substs) = ty.kind()
         && let Some(t_or_e_ty) = substs[usize::from(!is_err)].as_type()
     {
-        // Issue #11245: Do not lint `!` or never-like enums
-        if t_or_e_ty.is_never()
-            || (t_or_e_ty.is_enum() && t_or_e_ty.ty_adt_def().is_some_and(|def| def.variants().is_empty()))
-        {
+        if is_never_like(t_or_e_ty) {
             return;
         }
 
@@ -67,21 +65,19 @@ pub(super) fn check(
         return;
     }
 
-    let help = if variant == Variant::Unwrap && is_lint_allowed(cx, EXPECT_USED, expr.hir_id) {
-        format!(
-            "if you don't want to handle the `{none_value}` case gracefully, consider \
-                using `expect{method_suffix}()` to provide a better panic message"
-        )
-    } else {
-        format!("if this value is {none_prefix}`{none_value}`, it will panic")
-    };
-
-    span_lint_and_help(
+    span_lint_and_then(
         cx,
         variant.lint(),
         expr.span,
         &format!("used `{}()` on {kind} value", variant.method_name(is_err)),
-        None,
-        &help,
+        |diag| {
+            diag.note(format!("if this value is {none_prefix}`{none_value}`, it will panic"));
+
+            if variant == Variant::Unwrap && is_lint_allowed(cx, EXPECT_USED, expr.hir_id) {
+                diag.help(format!(
+                    "consider using `expect{method_suffix}()` to provide a better panic message"
+                ));
+            }
+        },
     );
 }

clippy_utils/src/ty.rs

@@ -1093,6 +1093,11 @@ fn assert_generic_args_match<'tcx>(tcx: TyCtxt<'tcx>, did: DefId, args: &[Generi
     }
 }
 
+/// Returns whether `ty` is never-like; i.e., `!` (never) or an enum with zero variants.
+pub fn is_never_like(ty: Ty<'_>) -> bool {
+    ty.is_never() || (ty.is_enum() && ty.ty_adt_def().is_some_and(|def| def.variants().is_empty()))
+}
+
 /// Makes the projection type for the named associated type in the given impl or trait impl.
 ///
 /// This function is for associated types which are "known" to exist, and as such, will only return

tests/ui-toml/expect_used/expect_used.stderr

@@ -4,7 +4,7 @@ error: used `expect()` on an `Option` value
 LL |     let _ = opt.expect("");
    |             ^^^^^^^^^^^^^^
    |
-   = help: if this value is `None`, it will panic
+   = note: if this value is `None`, it will panic
    = note: `-D clippy::expect-used` implied by `-D warnings`
 
 error: used `expect()` on a `Result` value
@@ -13,7 +13,7 @@ error: used `expect()` on a `Result` value
 LL |     let _ = res.expect("");
    |             ^^^^^^^^^^^^^^
    |
-   = help: if this value is an `Err`, it will panic
+   = note: if this value is an `Err`, it will panic
 
 error: aborting due to 2 previous errors
 

tests/ui-toml/unwrap_used/unwrap_used.stderr

@@ -12,7 +12,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = boxed_slice.get(1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
    = note: `-D clippy::unwrap-used` implied by `-D warnings`
 
 error: called `.get().unwrap()` on a slice. Using `[]` is more clear and more concise
@@ -27,7 +28,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_slice.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a Vec. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:40:17
@@ -41,7 +43,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_vec.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a VecDeque. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:41:17
@@ -55,7 +58,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_vecdeque.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a HashMap. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:42:17
@@ -69,7 +73,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_hashmap.get(&1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a BTreeMap. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:43:17
@@ -83,7 +88,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_btreemap.get(&1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a slice. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:47:21
@@ -97,7 +103,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _: u8 = *boxed_slice.get(1).unwrap();
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a slice. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:52:9
@@ -111,7 +118,8 @@ error: used `unwrap()` on an `Option` value
 LL |         *boxed_slice.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a slice. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:53:9
@@ -125,7 +133,8 @@ error: used `unwrap()` on an `Option` value
 LL |         *some_slice.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a Vec. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:54:9
@@ -139,7 +148,8 @@ error: used `unwrap()` on an `Option` value
 LL |         *some_vec.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a VecDeque. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:55:9
@@ -153,7 +163,8 @@ error: used `unwrap()` on an `Option` value
 LL |         *some_vecdeque.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a Vec. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:67:17
@@ -167,7 +178,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_vec.get(0..1).unwrap().to_vec();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a Vec. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:68:17
@@ -181,7 +193,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_vec.get_mut(0..1).unwrap().to_vec();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a slice. Using `[]` is more clear and more concise
   --> $DIR/unwrap_used.rs:75:13

tests/ui/expect.stderr

@@ -4,7 +4,7 @@ error: used `expect()` on an `Option` value
 LL |     let _ = opt.expect("");
    |             ^^^^^^^^^^^^^^
    |
-   = help: if this value is `None`, it will panic
+   = note: if this value is `None`, it will panic
    = note: `-D clippy::expect-used` implied by `-D warnings`
 
 error: used `expect()` on a `Result` value
@@ -13,15 +13,15 @@ error: used `expect()` on a `Result` value
 LL |     let _ = res.expect("");
    |             ^^^^^^^^^^^^^^
    |
-   = help: if this value is an `Err`, it will panic
+   = note: if this value is an `Err`, it will panic
 
 error: used `expect_err()` on a `Result` value
   --> $DIR/expect.rs:12:13
    |
 LL |     let _ = res.expect_err("");
    |             ^^^^^^^^^^^^^^^^^^
    |
-   = help: if this value is an `Ok`, it will panic
+   = note: if this value is an `Ok`, it will panic
 
 error: aborting due to 3 previous errors
 

tests/ui/get_unwrap.stderr

@@ -16,7 +16,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = boxed_slice.get(1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
    = note: `-D clippy::unwrap-used` implied by `-D warnings`
 
 error: called `.get().unwrap()` on a slice. Using `[]` is more clear and more concise
@@ -31,7 +32,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_slice.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a Vec. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:40:17
@@ -45,7 +47,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_vec.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a VecDeque. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:41:17
@@ -59,7 +62,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_vecdeque.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a HashMap. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:42:17
@@ -73,7 +77,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_hashmap.get(&1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a BTreeMap. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:43:17
@@ -87,7 +92,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_btreemap.get(&1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a slice. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:47:21
@@ -101,7 +107,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _: u8 = *boxed_slice.get(1).unwrap();
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a slice. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:52:9
@@ -115,7 +122,8 @@ error: used `unwrap()` on an `Option` value
 LL |         *boxed_slice.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a slice. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:53:9
@@ -129,7 +137,8 @@ error: used `unwrap()` on an `Option` value
 LL |         *some_slice.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a Vec. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:54:9
@@ -143,7 +152,8 @@ error: used `unwrap()` on an `Option` value
 LL |         *some_vec.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a VecDeque. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:55:9
@@ -157,7 +167,8 @@ error: used `unwrap()` on an `Option` value
 LL |         *some_vecdeque.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a Vec. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:67:17
@@ -171,7 +182,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_vec.get(0..1).unwrap().to_vec();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a Vec. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:68:17
@@ -185,7 +197,8 @@ error: used `unwrap()` on an `Option` value
 LL |         let _ = some_vec.get_mut(0..1).unwrap().to_vec();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a slice. Using `[]` is more clear and more concise
   --> $DIR/get_unwrap.rs:78:24