Try without generics, use fn pointers instead

Author: jieyouxu

tests/ui/debuginfo/auxiliary/line-tables-only-helper.rs

@@ -1,22 +1,25 @@
 //@ compile-flags: -Cstrip=none -Cdebuginfo=line-tables-only
+use std::backtrace::Backtrace;
 
 #[no_mangle]
-pub fn baz<F>(mut cb: F, data: u32) where F: FnMut(u32) {
-    cb(data);
+pub fn baz(cb: fn(u32) -> Backtrace, data: u32) -> Backtrace {
+    cb(data)
 }
 
 #[no_mangle]
-pub fn bar<F>(cb: F, data: u32) where F: FnMut(u32) {
-    baz(cb, data);
+pub fn bar(cb: fn(u32) -> Backtrace, data: u32) -> Backtrace {
+    baz(cb, data)
 }
 
 #[no_mangle]
-pub fn foo<F>(cb: F, data: u32) where F: FnMut(u32) {
-    bar(cb, data);
+pub fn foo(cb: fn(u32) -> Backtrace, data: u32) -> Backtrace {
+    bar(cb, data)
+}
+
+fn helper(_x: u32) -> Backtrace {
+    Backtrace::capture()
 }
 
 pub fn capture_backtrace() -> std::backtrace::Backtrace {
-    let mut bt = None;
-    foo(|_| bt = Some(std::backtrace::Backtrace::capture()), 42);
-    bt.unwrap()
+    foo(helper, 42)
 }