Rollup merge of #68302 - anp:caller-fn-ptr, r=eddyb,oli-obk

Fix #[track_caller] and function pointers

Starting with failing tests, fix the miscompilation and ICE caused by `ReifyShim` bug.

Fixes #68178.

src/test/ui/rfc-2091-track-caller/tracked-fn-ptr-with-arg.rs

@@ -0,0 +1,19 @@
+// run-pass
+
+#![feature(track_caller)]
+
+fn pass_to_ptr_call<T>(f: fn(T), x: T) {
+    f(x);
+}
+
+#[track_caller]
+fn tracked_unit(_: ()) {
+    let expected_line = line!() - 1;
+    let location = std::panic::Location::caller();
+    assert_eq!(location.file(), file!());
+    assert_eq!(location.line(), expected_line, "call shims report location as fn definition");
+}
+
+fn main() {
+    pass_to_ptr_call(tracked_unit, ());
+}

src/test/ui/rfc-2091-track-caller/tracked-fn-ptr.rs

@@ -0,0 +1,19 @@
+// run-pass
+
+#![feature(track_caller)]
+
+fn ptr_call(f: fn()) {
+    f();
+}
+
+#[track_caller]
+fn tracked() {
+    let expected_line = line!() - 1;
+    let location = std::panic::Location::caller();
+    assert_eq!(location.file(), file!());
+    assert_eq!(location.line(), expected_line, "call shims report location as fn definition");
+}
+
+fn main() {
+    ptr_call(tracked);
+}