Rubberduck: Parser Error: comma when Erasing two Arrays

[dimitropoulos]

A new module with the following code:

Public Sub EraseTwoArrays()

Dim someArray() As String
Dim someOtherArray() as String

Erase someArray(), someOtherArray()

End Sub

yeilds the following error:
msg: "extraneous input ',' expecting {, '!', '.', ACCESS, ADDRESSOF, ALIAS, AND, ATTRIBUTE, APPACTIVATE, APPEND, AS, BEGIN, BEEP, BINARY, BOOLEAN, BYVAL, BYREF, BYTE, CALL, CASE, CHDIR, CHDRIVE, CLASS, CLOSE, COLLECTION, CONST, DATABASE, DATE, DECLARE, DEFBOOL, DEFBYTE, DEFDATE, DEFDBL, DEFDEC, DEFCUR, DEFINT, DEFLNG, DEFOBJ, DEFSNG, DEFSTR, DEFVAR, DELETESETTING, DIM, DO, DOUBLE, EACH, ELSE, ELSEIF, END_ENUM, END_FUNCTION, END_IF, END_PROPERTY, END_SELECT, END_SUB, END_TYPE, END_WITH, END, ENUM, EQV, ERASE, ERROR, EVENT, EXIT_DO, EXIT_FOR, EXIT_FUNCTION, EXIT_PROPERTY, EXIT_SUB, FALSE, FILECOPY, FRIEND, FOR, FUNCTION, GET, GLOBAL, GOSUB, GOTO, IF, IMP, IMPLEMENTS, IN, INPUT, IS, INTEGER, KILL, LOAD, LOCK, LONG, LOOP, LEN, LET, LIB, LIKE, LINE_INPUT, LSET, ME, MID, MKDIR, MOD, NAME, NEXT, NEW, NOT, NOTHING, NULL, ON, ON_ERROR, ON_LOCAL_ERROR, OPEN, OPTIONAL, OPTION_BASE, OPTION_EXPLICIT, OPTION_COMPARE, OPTION_PRIVATE_MODULE, OR, OUTPUT, PARAMARRAY, PRESERVE, PRINT, PRIVATE, PROPERTY_GET, PROPERTY_LET, PROPERTY_SET, PUBLIC, PUT, RANDOM, RANDOMIZE, RAISEEVENT, READ, REDIM, REM, RESET, RESUME, RETURN, RMDIR, RSET, SAVEPICTURE, SAVESETTING, SEEK, SELECT, SENDKEYS, SET, SETATTR, SHARED, SINGLE, SPC, STATIC, STEP, STOP, STRING, SUB, TAB, TEXT, THEN, TIME, TO, TRUE, TYPE, TYPEOF, UNLOAD, UNLOCK, UNTIL, VARIANT, VERSION, WEND, WHILE, WIDTH, WITH, WITHEVENTS, WRITE, XOR, '&', '/', '\', '=', '>=', '>', '<=', '(', '<', '-', '*', '<>', '+', '^', NEWLINE, REMCOMMENT, COMMENT, ':', WS, IDENTIFIER}"

offending symbol: {[@33,109:109=',',<7>,6:17]}

Line 6, character 17 + 1 (character 18)

---

A workaround to

Public Sub EraseTwoArrays()

Dim someArray() As String
Dim someOtherArray() As String

Erase someArray()
Erase someOtherArray()

End Sub

fixes the issue temporarily

[retailcoder]

The parser rule that defines the Erase statement syntax simply doesn't handle it - congratulations, you've found one of the [very] few bugs left in the grammar!

eraseStmt : ERASE WS valueStmt;

The fix is pretty simple: we need to allow multiple valueStmt's.

[Vogel612]

soo fix would be:

eraseStmt : ERASE WS valueStmtList
valueStmtList : valueStmt (WS? "," WS? valueStmtList)

Or is that basic recursion again a problem for ANTLR?

[ghost]

Why are built-in functions like these treated specially? Couldn't we just treat them as normal function calls ? That is, get rid of the eraseStmt and let it be parsed as a normal procedure call. What are the reasons against such an approach?

[retailcoder]

@autoboosh very good question. might need to ask the original author for that, @uwol - I believe Rubberduck _is_ using _some_ of these "special-cased" parser rules to implement inspections, but I can't think of one off the top of my head ATM.

[retailcoder]

@autoboosh well they _could_ be treated as function calls, but they're not part of the VBA standard library (AFAIK), so they wouldn't resolve to a known function anyway. It doesn't hurt either way, but having it in the grammar gives us a handle if we ever want to inspect things.

[uwol]

The grammar distinguishes statements and functions. For each statement, there is a specific parser rule in the grammar according to the official Visual Basic language reference
https://msdn.microsoft.com/en-us/library/aa338153%28v=vs.60%29.aspx
In contrast, functions are not defined as parts of the language and thus not part of the grammar.

E. g. the Erase Statement is defined in
https://msdn.microsoft.com/en-us/library/aa243360%28v=vs.60%29.aspx
just next to typical control structures and in contrast to functions such as the Format function
https://msdn.microsoft.com/en-us/library/aa262745%28v=vs.60%29.aspx
which therefore is not part of the grammar.

[uwol]

A non-recursive fix would be

eraseStmt : ERASE WS valueStmtList 
valueStmtList : valueStmt (WS? "," WS? valueStmt)*

[ghost]

Fixed with https://github.com/rubberduck-vba/Rubberduck/pull/1255.