RDC00310 — Redundant ByVal argument

Severity: Hint · Family: RDC (Rubberduck Core analyzers) · Raised by: RedundantByValArgumentAnalyzer

An argument is written ByVal for a parameter that is ByVal already.

The parameter takes its argument by value whether ByVal is written before it or not: Twice(ByVal 2) and Twice(2) pass the same value the same way. An object is passed as itself, not as the value of its default member, which a pair of parentheses would make it. The keyword changes nothing.

MS-VBA compiles it. MS-VBAL §5.6.13.1 says ByVal is written only before an argument of an external procedure, and RD-VBA compiles it where MS-VBA does (RD-VBAL §5.6.13.1 Argument Lists). Written anywhere else, ByVal is a compile error, the one MS-VBA reports: Type mismatch before an argument of a ByRef parameter, and a Syntax error before one of a function MS-VBA compiles inline, such as Len or InStr.

ByVal is not redundant before an argument of a Declare's ByRef or As Any parameter, or of VarPtr: there it passes a value where an address goes.

That the parameter is ByVal is a fact of the argument (ValueExpressionSemanticFlags.RedundantByVal): the analyzer reads it off the facts the environment host found, and is not given the syntax tree to look it up in.

How it is raised

Situation	Example	Resolution
An argument of a `ByVal` parameter of the workspace, of a library, of a class, or of a `Declare`.	`Twice(ByVal 2)`, `Left("abc", ByVal 1)`, `k.Add ByVal n`	Remove `ByVal`: `Twice(2)`.
The same, given by name.	`Twice(n:=ByVal 2)`	Remove `ByVal`: `Twice(n:=2)`.

Table of Contents

RDC00310 — Redundant ByVal argument

How it is raised

See also