patch 8.2.2784: Vim9: cannot use \=expr in :substitute
Problem: Vim9: cannot use \=expr in :substitute.
Solution: Compile the expression into instructions and execute them when
invoked.
diff --git a/src/globals.h b/src/globals.h
index 51a6946..017c059 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1379,6 +1379,9 @@
EXTERN long sub_nsubs; // total number of substitutions
EXTERN linenr_T sub_nlines; // total number of lines changed
+// Used when a compiled :substitute has an expression.
+EXTERN struct subs_expr_S *substitute_instr INIT(= NULL);
+
// table to store parsed 'wildmode'
EXTERN char_u wim_flags[4];