Rollup merge of #144817 - WaffleLapkin:reject-referety, r=Urgau

Properly reject tail calls to `&FnPtr` or `&FnDef`

Fixes rust-lang/rust#144795

5 files changed, 145 insertions, 0 deletions

diff --git a/tests/ui/explicit-tail-calls/callee_is_ref.fixed b/tests/ui/explicit-tail-calls/callee_is_ref.fixed
new file mode 100644
index 00000000000..7525e5c5df8
--- /dev/null
+++ b/tests/ui/explicit-tail-calls/callee_is_ref.fixed
@@ -0,0 +1,26 @@
+//@ run-rustfix
+#![feature(explicit_tail_calls)]
+#![expect(incomplete_features)]
+
+fn f() {}
+
+fn g() {
+    become (*(&f))() //~ error: tail calls can only be performed with function definitions or pointers
+}
+
+fn h() {
+    let table = [f as fn()];
+    if let Some(fun) = table.get(0) {
+        become (*fun)(); //~ error: tail calls can only be performed with function definitions or pointers
+    }
+}
+
+fn i() {
+    become (***Box::new(&mut &f))(); //~ error: tail calls can only be performed with function definitions or pointers
+}
+
+fn main() {
+    g();
+    h();
+    i();
+}
diff --git a/tests/ui/explicit-tail-calls/callee_is_ref.rs b/tests/ui/explicit-tail-calls/callee_is_ref.rs
new file mode 100644
index 00000000000..36bf9efb952
--- /dev/null
+++ b/tests/ui/explicit-tail-calls/callee_is_ref.rs
@@ -0,0 +1,26 @@
+//@ run-rustfix
+#![feature(explicit_tail_calls)]
+#![expect(incomplete_features)]
+
+fn f() {}
+
+fn g() {
+    become (&f)() //~ error: tail calls can only be performed with function definitions or pointers
+}
+
+fn h() {
+    let table = [f as fn()];
+    if let Some(fun) = table.get(0) {
+        become fun(); //~ error: tail calls can only be performed with function definitions or pointers
+    }
+}
+
+fn i() {
+    become Box::new(&mut &f)(); //~ error: tail calls can only be performed with function definitions or pointers
+}
+
+fn main() {
+    g();
+    h();
+    i();
+}
diff --git a/tests/ui/explicit-tail-calls/callee_is_ref.stderr b/tests/ui/explicit-tail-calls/callee_is_ref.stderr
new file mode 100644
index 00000000000..4a2ff465e68
--- /dev/null
+++ b/tests/ui/explicit-tail-calls/callee_is_ref.stderr
@@ -0,0 +1,38 @@
+error: tail calls can only be performed with function definitions or pointers
+  --> $DIR/callee_is_ref.rs:8:12
+   |
+LL |     become (&f)()
+   |            ^^^^^^
+   |
+   = note: callee has type `&fn() {f}`
+help: consider dereferencing the expression to get a function definition
+   |
+LL |     become (*(&f))()
+   |            ++    +
+
+error: tail calls can only be performed with function definitions or pointers
+  --> $DIR/callee_is_ref.rs:14:16
+   |
+LL |         become fun();
+   |                ^^^^^
+   |
+   = note: callee has type `&fn()`
+help: consider dereferencing the expression to get a function pointer
+   |
+LL |         become (*fun)();
+   |                ++   +
+
+error: tail calls can only be performed with function definitions or pointers
+  --> $DIR/callee_is_ref.rs:19:12
+   |
+LL |     become Box::new(&mut &f)();
+   |            ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: callee has type `Box<&mut &fn() {f}>`
+help: consider dereferencing the expression to get a function definition
+   |
+LL |     become (***Box::new(&mut &f))();
+   |            ++++                 +
+
+error: aborting due to 3 previous errors
+
diff --git a/tests/ui/explicit-tail-calls/callee_is_weird.rs b/tests/ui/explicit-tail-calls/callee_is_weird.rs
new file mode 100644
index 00000000000..b3ca878c232
--- /dev/null
+++ b/tests/ui/explicit-tail-calls/callee_is_weird.rs
@@ -0,0 +1,29 @@
+#![feature(explicit_tail_calls, exclusive_wrapper, fn_traits, unboxed_closures)]
+#![expect(incomplete_features)]
+
+fn f() {}
+
+fn g() {
+    become std::sync::Exclusive::new(f)() //~ error: tail calls can only be performed with function definitions or pointers
+}
+
+fn h() {
+    become (&mut &std::sync::Exclusive::new(f))() //~ error: tail calls can only be performed with function definitions or pointers
+}
+
+fn i() {
+    struct J;
+
+    impl FnOnce<()> for J {
+        type Output = ();
+        extern "rust-call" fn call_once(self, (): ()) -> Self::Output {}
+    }
+
+    become J(); //~ error: tail calls can only be performed with function definitions or pointers
+}
+
+fn main() {
+    g();
+    h();
+    i();
+}
diff --git a/tests/ui/explicit-tail-calls/callee_is_weird.stderr b/tests/ui/explicit-tail-calls/callee_is_weird.stderr
new file mode 100644
index 00000000000..a4e5a38ce33
--- /dev/null
+++ b/tests/ui/explicit-tail-calls/callee_is_weird.stderr
@@ -0,0 +1,26 @@
+error: tail calls can only be performed with function definitions or pointers
+  --> $DIR/callee_is_weird.rs:7:12
+   |
+LL |     become std::sync::Exclusive::new(f)()
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: callee has type `Exclusive<fn() {f}>`
+
+error: tail calls can only be performed with function definitions or pointers
+  --> $DIR/callee_is_weird.rs:11:12
+   |
+LL |     become (&mut &std::sync::Exclusive::new(f))()
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: callee has type `Exclusive<fn() {f}>`
+
+error: tail calls can only be performed with function definitions or pointers
+  --> $DIR/callee_is_weird.rs:22:12
+   |
+LL |     become J();
+   |            ^^^
+   |
+   = note: callee has type `J`
+
+error: aborting due to 3 previous errors
+