Auto merge of rust-lang#11252 - Centri3:rust-lang#11245, r=xFrednet

[`unwrap_used`]: Do not lint unwrapping on `!` or never-like enums

Fixes rust-lang#11245

changelog: [`unwrap_used`]: Do not lint unwrapping on `!` or never-like enums
changelog: [`expect_used`]: Do not lint unwrapping on `!` or never-like enums

Author: bors

clippy_lints/src/methods/expect_used.rs

@@ -17,7 +17,6 @@ mod collapsible_str_replace;
 mod drain_collect;
 mod err_expect;
 mod expect_fun_call;
-mod expect_used;
 mod extend_with_drain;
 mod filetype_is_file;
 mod filter_map;
@@ -105,7 +104,7 @@ mod unnecessary_lazy_eval;
 mod unnecessary_literal_unwrap;
 mod unnecessary_sort_by;
 mod unnecessary_to_owned;
-mod unwrap_used;
+mod unwrap_expect_used;
 mod useless_asref;
 mod utils;
 mod vec_resize_to_zero;
@@ -3948,13 +3947,27 @@ impl Methods {
                     match method_call(recv) {
                         Some(("ok", recv, [], _, _)) => ok_expect::check(cx, expr, recv),
                         Some(("err", recv, [], err_span, _)) => err_expect::check(cx, expr, recv, span, err_span, &self.msrv),
-                        _ => expect_used::check(cx, expr, recv, false, self.allow_expect_in_tests),
+                        _ => unwrap_expect_used::check(
+                            cx,
+                            expr,
+                            recv,
+                            false,
+                            self.allow_expect_in_tests,
+                            unwrap_expect_used::Variant::Expect,
+                        ),
                     }
                     unnecessary_literal_unwrap::check(cx, expr, recv, name, args);
                 },
                 ("expect_err", [_]) => {
                     unnecessary_literal_unwrap::check(cx, expr, recv, name, args);
-                    expect_used::check(cx, expr, recv, true, self.allow_expect_in_tests);
+                    unwrap_expect_used::check(
+                        cx,
+                        expr,
+                        recv,
+                        true,
+                        self.allow_expect_in_tests,
+                        unwrap_expect_used::Variant::Expect,
+                    );
                 },
                 ("extend", [arg]) => {
                     string_extend_chars::check(cx, expr, recv, arg);
@@ -4180,11 +4193,25 @@ impl Methods {
                         _ => {},
                     }
                     unnecessary_literal_unwrap::check(cx, expr, recv, name, args);
-                    unwrap_used::check(cx, expr, recv, false, self.allow_unwrap_in_tests);
+                    unwrap_expect_used::check(
+                        cx,
+                        expr,
+                        recv,
+                        false,
+                        self.allow_unwrap_in_tests,
+                        unwrap_expect_used::Variant::Unwrap,
+                    );
                 },
                 ("unwrap_err", []) => {
                     unnecessary_literal_unwrap::check(cx, expr, recv, name, args);
-                    unwrap_used::check(cx, expr, recv, true, self.allow_unwrap_in_tests);
+                    unwrap_expect_used::check(
+                        cx,
+                        expr,
+                        recv,
+                        true,
+                        self.allow_unwrap_in_tests,
+                        unwrap_expect_used::Variant::Unwrap,
+                    );
                 },
                 ("unwrap_or", [u_arg]) => {
                     match method_call(recv) {

clippy_lints/src/methods/mod.rs

@@ -0,0 +1,83 @@
+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};
+use rustc_middle::ty;
+use rustc_span::sym;
+
+use super::{EXPECT_USED, UNWRAP_USED};
+
+#[derive(Clone, Copy, Eq, PartialEq)]
+pub(super) enum Variant {
+    Unwrap,
+    Expect,
+}
+
+impl Variant {
+    fn method_name(self, is_err: bool) -> &'static str {
+        match (self, is_err) {
+            (Variant::Unwrap, true) => "unwrap_err",
+            (Variant::Unwrap, false) => "unwrap",
+            (Variant::Expect, true) => "expect_err",
+            (Variant::Expect, false) => "expect",
+        }
+    }
+
+    fn lint(self) -> &'static Lint {
+        match self {
+            Variant::Unwrap => UNWRAP_USED,
+            Variant::Expect => EXPECT_USED,
+        }
+    }
+}
+
+/// 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<'_>,
+    recv: &Expr<'_>,
+    is_err: bool,
+    allow_unwrap_in_tests: bool,
+    variant: Variant,
+) {
+    let ty = cx.typeck_results().expr_ty(recv).peel_refs();
+
+    let (kind, none_value, none_prefix) = if is_type_diagnostic_item(cx, ty, sym::Option) && !is_err {
+        ("an `Option`", "None", "")
+    } else if is_type_diagnostic_item(cx, ty, sym::Result)
+        && let ty::Adt(_, substs) = ty.kind()
+        && let Some(t_or_e_ty) = substs[usize::from(!is_err)].as_type()
+    {
+        if is_never_like(t_or_e_ty) {
+            return;
+        }
+
+        ("a `Result`", if is_err { "Ok" } else { "Err" }, "an ")
+    } else {
+        return;
+    };
+
+    let method_suffix = if is_err { "_err" } else { "" };
+
+    if allow_unwrap_in_tests && (is_in_test_function(cx.tcx, expr.hir_id) || is_in_cfg_test(cx.tcx, expr.hir_id)) {
+        return;
+    }
+
+    span_lint_and_then(
+        cx,
+        variant.lint(),
+        expr.span,
+        &format!("used `{}()` on {kind} value", variant.method_name(is_err)),
+        |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_lints/src/methods/unwrap_expect_used.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

clippy_lints/src/methods/unwrap_used.rs

@@ -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