vim-patch:8.1.1539: not easy to define a variable and lock it

Problem:    Not easy to define a variable and lock it.
Solution:   Add ":const".
https://github.com/vim/vim/commit/9937a055437ef67b57a1bdec8f0799b669c9dbf0

1 files changed, 25 insertions, 2 deletions

diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 4eaa72ee68..6649bebedb 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -9629,8 +9629,31 @@ This does NOT work: >
 			No error message is given for a non-existing
 			variable, also without !.
 			If the system does not support deleting an environment
-			variable, it is made emtpy.
-
+			variable, it is made empty.
+
+						*:cons* *:const* *E996*
+:cons[t] {var-name} = {expr1}
+:cons[t] [{name1}, {name2}, ...] = {expr1}
+:cons[t] [{name1}, {name2}, ...] .= {expr1}
+:cons[t] [{name}, ..., ; {lastname}] = {expr1}
+:cons[t] {var-name} =<< [trim] {marker}
+text...
+text...
+{marker}
+			Similar to |:let|, but additionally lock the variable
+			after setting the value.  This is the same as locking
+			the variable with |:lockvar| just after |:let|, thus: >
+				:const x = 1
+<			is equivalent to: >
+				:let x = 1
+				:lockvar 1 x
+<			This is useful if you want to make sure the variable
+			is not modified.
+							*E995*
+			|:const| does not allow to for changing a variable. >
+				:let x = 1
+				:const x = 2  " Error!
+<
 :lockv[ar][!] [depth] {name} ...			*:lockvar* *:lockv*
 			Lock the internal variable {name}.  Locking means that
 			it can no longer be changed (until it is unlocked).