Warn about flipped $ and " in $"(cmd)" (fixes koalaman#1517)

CHANGELOG.md

@@ -3,6 +3,7 @@
 - Preliminary support for fix suggestions
 - Files containing Bats tests can now be checked
 - Directory wide directives can now be placed in a `.shellcheckrc`
+- SC2247: Warn about $"(cmd)" and $"{var}"
 - SC2246: Warn if a shebang's interpreter ends with /
 - SC2245: Warn that Ksh ignores all but the first glob result in `[`
 - SC2243/SC2244: Suggest using explicit -n for `[ $foo ]`

src/ShellCheck/Analytics.hs

@@ -171,6 +171,7 @@ nodeChecks = [
     ,checkInvertedStringTest
     ,checkRedirectionToCommand
     ,checkNullaryExpansionTest
+    ,checkDollarQuoteParen
     ]
 
 
@@ -3169,5 +3170,18 @@ checkNullaryExpansionTest params t =
                 fix = fixWith [replaceStart id params 0 "-n "]
         _ -> return ()
 
+
+prop_checkDollarQuoteParen1 = verify checkDollarQuoteParen "$\"(foo)\""
+prop_checkDollarQuoteParen2 = verify checkDollarQuoteParen "$\"{foo}\""
+prop_checkDollarQuoteParen3 = verifyNot checkDollarQuoteParen "\"$(foo)\""
+prop_checkDollarQuoteParen4 = verifyNot checkDollarQuoteParen "$\"..\""
+checkDollarQuoteParen params t =
+    case t of
+        T_DollarDoubleQuoted id ((T_Literal _ (c:_)):_) | c `elem` "({" ->
+            warnWithFix id 2247 "Flip leading $ and \" if this should be a quoted substitution." (fix id)
+        _ -> return ()
+  where
+    fix id = fixWith [replaceStart id params 2 "\"$"]
+
 return []
 runTests =  $( [| $(forAllProperties) (quickCheckWithResult (stdArgs { maxSuccess = 1 }) ) |])