RDC00115 — Implicit result local

Severity: Information · Family: RDC (Rubberduck Core analyzers) · Raised by: ImplicitResultLocalAnalyzer

A function or a property getter reads its own return value, as the local variable it implicitly is.

A function declaration implicitly defines a local variable that shares its name and its declared type with the function, the function result variable (MS-VBAL §5.3.1 Procedure Declarations): what the function returns is what that variable holds when it ends. Assigning it is how a function returns a value. Reading it - Total = Total + Item, Debug.Print Total, Items.Add x - works too, and makes the name of the function a local variable of its own body. That reads as a call of the function, which it is everywhere else, and which Total(1) is in a function that takes an argument. A local declared for the work, and assigned to the return value once, at the end, says what the code does.

Each read is reported where it is. A recursive call (Factorial(n - 1)) is a call, not a read, and is not reported; neither is an assignment of the return value, nor a call of the function from another procedure.

How it is raised

Situation	Example	Resolution
The return value is used as an accumulator.	`For Each x In Items: Total = Total + x: Next`	Declare `Dim result As Long`, accumulate in it, and end with `Total = result`.
The return value is read after it is assigned.	`Size = 2: Size = Size * 2`	Compute the value in a local, and assign it once.
A member of an object it returns is called.	`Set Items = New Collection: Items.Add 1`	Build the object in a local (`Set result = New Collection`), and end with `Set Items = result`.

Quick fix

The diagnostic comes with a quick fix, Declare a local for the return value of '…', which makes these edits of the procedure:

a Dim of a local, before its first statement: result, or result2, result3… when the module or the procedure already has the name, of the type the procedure returns, written as it is (an As clause, a type character, an array);
the local in place of each name of the return value in the body, read or assigned;
the return value assigned the local before each Exit Function or Exit Property, on its line (If n = 0 Then Total = result: Exit Function), and on a line of its own before the end of the procedure, with Set when the body Sets its return value.

It is not offered for a procedure whose body starts on the line it is declared on. A function that returns an array and indexes it (Values(0) = 1) is not reported: the index reads as a call of the function.

Table of Contents

RDC00115 — Implicit result local

How it is raised

Quick fix

See also