From 6fdf295664acc28ebb018e1d7b97b9e9e1e8f0ea Mon Sep 17 00:00:00 2001
From: y21 <30553356+y21@users.noreply.github.com>
Date: Tue, 16 Apr 2024 20:25:35 +0200
Subject: [PATCH] let `qualify_min_const_fn` deal with drop checks

---
 clippy_lints/src/missing_const_for_fn.rs       | 15 +--------------
 .../ui/missing_const_for_fn/could_be_const.rs  | 18 ++++++++++++++++++
 .../missing_const_for_fn/could_be_const.stderr | 18 +++++++++++++++++-
 3 files changed, 36 insertions(+), 15 deletions(-)

diff --git a/clippy_lints/src/missing_const_for_fn.rs b/clippy_lints/src/missing_const_for_fn.rs
index 9ba19e0a8658..fe636f27a0f0 100644
--- a/clippy_lints/src/missing_const_for_fn.rs
+++ b/clippy_lints/src/missing_const_for_fn.rs
@@ -1,7 +1,6 @@
 use clippy_config::msrvs::{self, Msrv};
 use clippy_utils::diagnostics::span_lint;
 use clippy_utils::qualify_min_const_fn::is_min_const_fn;
-use clippy_utils::ty::has_drop;
 use clippy_utils::{fn_has_unsatisfiable_preds, is_entrypoint_fn, is_from_proc_macro, trait_ref_of_method};
 use rustc_hir as hir;
 use rustc_hir::def_id::CRATE_DEF_ID;
@@ -121,10 +120,7 @@ fn check_fn(
                 }
             },
             FnKind::Method(_, sig, ..) => {
-                if trait_ref_of_method(cx, def_id).is_some()
-                    || already_const(sig.header)
-                    || method_accepts_droppable(cx, def_id)
-                {
+                if trait_ref_of_method(cx, def_id).is_some() || already_const(sig.header) {
                     return;
                 }
             },
@@ -162,15 +158,6 @@ fn check_fn(
     extract_msrv_attr!(LateContext);
 }
 
-/// Returns true if any of the method parameters is a type that implements `Drop`. The method
-/// can't be made const then, because `drop` can't be const-evaluated.
-fn method_accepts_droppable(cx: &LateContext<'_>, def_id: LocalDefId) -> bool {
-    let sig = cx.tcx.fn_sig(def_id).instantiate_identity().skip_binder();
-
-    // If any of the params are droppable, return true
-    sig.inputs().iter().any(|&ty| has_drop(cx, ty))
-}
-
 // We don't have to lint on something that's already `const`
 #[must_use]
 fn already_const(header: hir::FnHeader) -> bool {
diff --git a/tests/ui/missing_const_for_fn/could_be_const.rs b/tests/ui/missing_const_for_fn/could_be_const.rs
index 06dbbeb31c0d..8e0ede478b56 100644
--- a/tests/ui/missing_const_for_fn/could_be_const.rs
+++ b/tests/ui/missing_const_for_fn/could_be_const.rs
@@ -141,3 +141,21 @@ fn union_access_can_be_const() {
         let _ = unsafe { bar.val };
     }
 }
+
+mod issue12677 {
+    pub struct Wrapper {
+        pub strings: Vec<String>,
+    }
+
+    impl Wrapper {
+        #[must_use]
+        pub fn new(strings: Vec<String>) -> Self {
+            Self { strings }
+        }
+
+        #[must_use]
+        pub fn empty() -> Self {
+            Self { strings: Vec::new() }
+        }
+    }
+}
diff --git a/tests/ui/missing_const_for_fn/could_be_const.stderr b/tests/ui/missing_const_for_fn/could_be_const.stderr
index b2cade305637..84ad6357b7bc 100644
--- a/tests/ui/missing_const_for_fn/could_be_const.stderr
+++ b/tests/ui/missing_const_for_fn/could_be_const.stderr
@@ -130,5 +130,21 @@ LL | |         let _ = unsafe { bar.val };
 LL | |     }
    | |_____^
 
-error: aborting due to 14 previous errors
+error: this could be a `const fn`
+  --> tests/ui/missing_const_for_fn/could_be_const.rs:152:9
+   |
+LL | /         pub fn new(strings: Vec<String>) -> Self {
+LL | |             Self { strings }
+LL | |         }
+   | |_________^
+
+error: this could be a `const fn`
+  --> tests/ui/missing_const_for_fn/could_be_const.rs:157:9
+   |
+LL | /         pub fn empty() -> Self {
+LL | |             Self { strings: Vec::new() }
+LL | |         }
+   | |_________^
+
+error: aborting due to 16 previous errors