From bd2facb24512fd6c5787f4641e8f437f65692063 Mon Sep 17 00:00:00 2001
From: Vidar Holen <spam@vidarholen.net>
Date: Sat, 9 Sep 2017 16:07:38 -0700
Subject: [PATCH] Suggest (( expr )) over let expr (#813)

---
 ShellCheck/Checks/Commands.hs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/ShellCheck/Checks/Commands.hs b/ShellCheck/Checks/Commands.hs
index 3523a0c..cae11fe 100644
--- a/ShellCheck/Checks/Commands.hs
+++ b/ShellCheck/Checks/Commands.hs
@@ -87,6 +87,7 @@ commandChecks = [
     ,checkDeprecatedFgrep
     ,checkWhileGetoptsCase
     ,checkCatastrophicRm
+    ,checkLetUsage
     ]
 
 buildCommandMap :: [CommandCheck] -> Map.Map CommandName (Token -> Analysis)
@@ -824,5 +825,13 @@ checkCatastrophicRm = CommandCheck (Basename "rm") $ \t ->
     importantPaths = filter (not . null) $
         ["", "/", "/*", "/*/*"] >>= (\x -> map (++x) paths)
 
+
+prop_checkLetUsage1 = verify checkLetUsage "let a=1"
+prop_checkLetUsage2 = verifyNot checkLetUsage "(( a=1 ))"
+checkLetUsage = CommandCheck (Exactly "let") f
+  where
+    f t = whenShell [Bash,Ksh] $ do
+        style (getId t) 2219 $ "Instead of 'let expr', prefer (( expr )) ."
+
 return []
 runTests =  $( [| $(forAllProperties) (quickCheckWithResult (stdArgs { maxSuccess = 1 }) ) |])