Parser support for $[..], plus deprecation warning.

ShellCheck/AST.hs

@@ -60,6 +60,7 @@ data Token =
     | T_Do Id
     | T_DollarArithmetic Id Token
     | T_DollarBraced Id Token
+    | T_DollarBracket Id Token
     | T_DollarDoubleQuoted Id [Token]
     | T_DollarExpansion Id [Token]
     | T_DollarSingleQuoted Id String

ShellCheck/Analytics.hs

@@ -127,6 +127,7 @@ basicChecks = [
     ,checkSpuriousExec
     ,checkSpuriousExpansion
     ,checkUnusedEchoEscapes
+    ,checkDollarBrackets
     ]
 treeChecks = [
     checkUnquotedExpansions
@@ -363,6 +364,7 @@ checkBashisms = bashism
     bashism (T_DollarDoubleQuoted id _) = warnMsg id "$\"..\""
     bashism (T_ForArithmetic id _ _ _ _) = warnMsg id "arithmetic for loop"
     bashism (T_Arithmetic id _) = warnMsg id "standalone ((..))"
+    bashism (T_DollarBracket id _) = warnMsg id "$[..] in place of $((..))"
     bashism (T_SelectIn id _ _ _) = warnMsg id "select loop"
     bashism (T_BraceExpansion id _) = warnMsg id "brace expansion"
     bashism (T_Condition id DoubleBracket _) = warnMsg id "[[ ]]"
@@ -1227,8 +1229,14 @@ checkUnusedEchoEscapes = checkCommand "echo" f
             info id "echo won't expand escape sequences. Consider printf."
 
 
---- Subshell detection
+prop_checkDollarBrackets1 = verify checkDollarBrackets "echo $[1+2]"
+prop_checkDollarBrackets2 = verifyNot checkDollarBrackets "echo $((1+2))"
+checkDollarBrackets (T_DollarBracket id _) =
+    style id "Use $((..)) instead of deprecated $[..]"
+checkDollarBrackets _ = return ()
 
+
+--- Subshell detection
 prop_subshellAssignmentCheck = verifyFull     subshellAssignmentCheck "cat foo | while read bar; do a=$bar; done; echo \"$a\""
 prop_subshellAssignmentCheck2 = verifyNotFull subshellAssignmentCheck "while read bar; do a=$bar; done < file; echo \"$a\""
 prop_subshellAssignmentCheck3 = verifyFull    subshellAssignmentCheck "( A=foo; ); rm $A"

ShellCheck/Parser.hs

@@ -843,7 +843,7 @@ readBraced = try $ do
 
 readNormalDollar = readDollarExpression <|> readDollarLonely <|> readDollarDoubleQuote
 readDoubleQuotedDollar = readDollarExpression <|> readDollarLonely
-readDollarExpression = readDollarArithmetic <|> readDollarBraced <|> readDollarExpansion <|> readDollarVariable <|> readDollarSingleQuote
+readDollarExpression = readDollarArithmetic <|> readDollarBracket <|> readDollarBraced <|> readDollarExpansion <|> readDollarVariable <|> readDollarSingleQuote
 
 prop_readDollarSingleQuote = isOk readDollarSingleQuote "$'foo\\\'lol'"
 readDollarSingleQuote = called "$'..' expression" $ do
@@ -873,6 +873,13 @@ readDollarArithmetic = called "$((..)) expression" $ do
     string "))"
     return (T_DollarArithmetic id c)
 
+readDollarBracket = called "$[..] expression" $ do
+    id <- getNextId
+    try (string "$[")
+    c <- readArithmeticContents
+    string "]"
+    return (T_DollarBracket id c)
+
 readArithmeticExpression = called "((..)) command" $ do
     id <- getNextId
     try (string "((")