Fix #14690 - :steplocal panics after break-on-error
:steplocal
enables only breakpoints in the current top-level binding.
When a normal breakpoint is hit, then the module name and the break id from the BRK_FUN
byte code
allow us to access the corresponding entry in a ModBreak table. From this entry we then get the SrcSpan
(see compiler/main/InteractiveEval.hs:bindLocalsAtBreakpoint).
With this source-span we can then determine the current top-level binding, needed for the steplocal command.
However, if we break at an exception or at an error, we don't have an BRK_FUN byte-code, so we don't have any source information.
The function bindLocalsAtBreakpoint
creates an UnhelpfulSpan
, which doesn't allow us to determine the current top-level binding.
To avoid a panic
, we have to check for UnhelpfulSpan
in the function ghc/GHCi/UI.hs:stepLocalCmd
.
Hence a :steplocal command after a break-on-exception or a break-on-error is not possible.