fix function_casts_as_integer lint

Author: RalfJung

src/tools/miri/src/shims/native_lib/trace/parent.rs

@@ -500,9 +500,8 @@ fn handle_segfault(
     capstone_disassemble(&instr, addr, cs, acc_events).expect("Failed to disassemble instruction");
 
     // Move the instr ptr into the deprotection code.
-    #[allow(unknown_lints)]
-    #[expect(clippy::as_conversions, function_casts_as_integer)]
-    new_regs.set_ip(mempr_off as usize);
+    #[expect(clippy::as_conversions)]
+    new_regs.set_ip(mempr_off as *const () as usize);
     // Don't mess up the stack by accident!
     new_regs.set_sp(stack_ptr);
 
@@ -553,9 +552,8 @@ fn handle_segfault(
     new_regs = regs_bak;
 
     // Reprotect everything and continue.
-    #[allow(unknown_lints)]
-    #[expect(clippy::as_conversions, function_casts_as_integer)]
-    new_regs.set_ip(mempr_on as usize);
+    #[expect(clippy::as_conversions)]
+    new_regs.set_ip(mempr_on as *const () as usize);
     new_regs.set_sp(stack_ptr);
     ptrace::setregs(pid, new_regs).unwrap();
     wait_for_signal(Some(pid), signal::SIGSTOP, InitialCont::Yes)?;

src/tools/miri/tests/pass/backtrace/backtrace-api-v1.rs

@@ -1,7 +1,5 @@
 //@normalize-stderr-test: "::<.*>" -> ""
 
-#![allow(function_casts_as_integer)]
-
 #[inline(never)]
 fn func_a() -> Box<[*mut ()]> {
     func_b::<u8>()

src/tools/miri/tests/pass/backtrace/backtrace-api-v1.stdout

@@ -1,5 +1,5 @@
-tests/pass/backtrace/backtrace-api-v1.rs:29:9 (func_d)
-tests/pass/backtrace/backtrace-api-v1.rs:16:9 (func_c)
-tests/pass/backtrace/backtrace-api-v1.rs:11:5 (func_b::<u8>)
-tests/pass/backtrace/backtrace-api-v1.rs:7:5 (func_a)
-tests/pass/backtrace/backtrace-api-v1.rs:36:18 (main)
+tests/pass/backtrace/backtrace-api-v1.rs:27:9 (func_d)
+tests/pass/backtrace/backtrace-api-v1.rs:14:9 (func_c)
+tests/pass/backtrace/backtrace-api-v1.rs:9:5 (func_b::<u8>)
+tests/pass/backtrace/backtrace-api-v1.rs:5:5 (func_a)
+tests/pass/backtrace/backtrace-api-v1.rs:34:18 (main)