ex_getln: Save and restore try state

Problem: when processing cycle such as

    :for pat in [' \ze*', ' \zs*']
    :  try
    :    let l = matchlist('x x', pat)
    :    $put ='E888 NOT detected for ' . pat
    :  catch
    :    $put ='E888 detected for ' . pat
    :  endtry
    :endfor

`:let l = …` throwing an error causes this error to be caught after 
color_cmdline attempts to get callback for highlighting next line (the one with 
`$put = 'E888 NOT…`). Saving/restoring state prevents this from happening.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/nvim/api/private/helpers.h b/src/nvim/api/private/helpers.h
index 159b9d5c2a..112d785bfd 100644
--- a/src/nvim/api/private/helpers.h
+++ b/src/nvim/api/private/helpers.h
@@ -82,6 +82,18 @@
 #define api_free_window(value)
 #define api_free_tabpage(value)
 
+/// Structure used for saving state for :try
+///
+/// Used when caller is supposed to be operating when other VimL code is being
+/// processed and that “other VimL code” must not be affected.
+typedef struct {
+  int trylevel;
+  int got_int;
+  int did_throw;
+  struct msglist *private_msg_list;
+  const struct msglist *const *msg_list;
+} TryState;
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "api/private/helpers.h.generated.h"
 #endif