WIP

Author: nealsid

library/core/Cargo.toml

@@ -16,6 +16,7 @@ test = false
 bench = false
 
 [features]
+default = ["debug_refcell"]
 # Make panics and failed asserts immediately abort without formatting any message
 panic_immediate_abort = []
 # Choose algorithms that are optimized for binary size instead of runtime performance

library/core/src/cell.rs

@@ -743,7 +743,7 @@ impl Debug for BorrowError {
         let mut builder = f.debug_struct("BorrowError");
 
         #[cfg(feature = "debug_refcell")]
-        builder.field("location", &format_args!("{}", self.location));
+        builder.field("location", self.location);
 
         builder.finish()
     }
@@ -767,12 +767,13 @@ pub struct BorrowMutError {
 #[stable(feature = "try_borrow", since = "1.13.0")]
 impl Debug for BorrowMutError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let mut builder = f.debug_struct("BorrowMutError");
+        write!(f, "{}", self.location)
+        // let mut builder = f.debug_struct("BorrowMutError");
 
-        #[cfg(feature = "debug_refcell")]
-        builder.field("location", &format_args!("{}", self.location));
+        // #[cfg(feature = "debug_refcell")]
+        // builder.field("location", self.location);
 
-        builder.finish()
+        // builder.finish()
     }
 }
 
@@ -787,23 +788,23 @@ impl Display for BorrowMutError {
 #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
 #[track_caller]
 #[cold]
-fn panic_already_borrowed(_err: BorrowMutError) -> ! {
+fn panic_already_borrowed(err: BorrowMutError) -> ! {
     if cfg!(feature = "debug_refcell") {
-        panic!("cannot borrow as mutable because it is also borrowed as immutable here {:?}", _err);
+        panic!("already borrowed here: {:?}", err);
     } else {
-        panic!("cannot borrow as mutable because it is also borrowed as immutable");
+        panic!("already borrowed");
     }
 }
 
 // This ensures the panicking code is outlined from `borrow` for `RefCell`.
 #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
 #[track_caller]
 #[cold]
-fn panic_already_mutably_borrowed(_err: BorrowError) -> ! {
+fn panic_already_mutably_borrowed(err: BorrowError) -> ! {
     if cfg!(feature = "debug_refcell") {
-        panic!("cannot borrow as immutable because it is also borrowed as mutable here {:?}", _err);
+        panic!("already mutably borrowed here: {:?}", err);
     } else {
-        panic!("cannot borrow as immutable because it is also borrowed as mutable");
+        panic!("already mutably borrowed");
     }
 }