Review feedback.

Author: cfallin

src/stub/error.rs

@@ -44,6 +44,7 @@ pub(crate) enum InternalError<T, C> {
     TracepointFeatureUnimplemented(u8),
     TracepointUnsupportedSourceEnumeration,
     MissingMultiThreadSchedulerLocking,
+    MissingToRawId,
 
     // Internal - A non-fatal error occurred (with errno-style error code)
     //
@@ -149,6 +150,7 @@ where
             TracepointFeatureUnimplemented(feat) => write!(f, "GDB client sent us a tracepoint packet using feature {}, but `gdbstub` doesn't implement it. If this is something you require, please file an issue at https://github.com/daniel5151/gdbstub/issues", *feat as char),
             TracepointUnsupportedSourceEnumeration => write!(f, "The target doesn't support the gdbstub TracepointSource extension, but attempted to transition to enumerating tracepoint sources"),
             MissingMultiThreadSchedulerLocking => write!(f, "GDB requested Scheduler Locking, but the Target does not implement the `MultiThreadSchedulerLocking` IDET"),
+            MissingToRawId => write!(f, "A RegId was used with an API that requires raw register IDs to be available (e.g. `report_stop_with_regs`) but returned `None` from `to_raw_id()`"),
 
             NonFatalError(_) => write!(f, "Internal non-fatal error. You should never see this! Please file an issue if you do!"),
         }

src/stub/state_machine.rs

@@ -301,12 +301,13 @@ impl<'a, T: Target, C: Connection> GdbStubStateMachineInner<'a, state::Running,
         if let Some(regs) = regs {
             if reason.is_t_packet() {
                 for (reg_id, value) in regs {
-                    if let Some(reg) = reg_id.to_raw_id() {
-                        res.write_num(reg).map_err(InternalError::from)?;
-                        res.write_str(":").map_err(InternalError::from)?;
-                        res.write_hex_buf(value).map_err(InternalError::from)?;
-                        res.write_str(";").map_err(InternalError::from)?;
-                    }
+                    let reg = reg_id
+                        .to_raw_id()
+                        .ok_or(InternalError::MissingToRawId)?;
+                    res.write_num(reg).map_err(InternalError::from)?;
+                    res.write_str(":").map_err(InternalError::from)?;
+                    res.write_hex_buf(value).map_err(InternalError::from)?;
+                    res.write_str(";").map_err(InternalError::from)?;
                 }
             }
         }