Inspection for duplicated function calls in If..Then

[daFreeMan]

There is need for a new inspection for redundant function calls when guarding against divide-by-zero errors:

If Foo(Bar, Baz) > 0 then
  Result = Frob(Baz) / Foo(Bar, Baz)
Else
  Result = -1
End If

No big deal unless Foo() is long running, memory intensive, network hogging, or...

Quick Fix would be:

Dim fooResult as Long
fooResult = Foo(Bar, Baz) 
If fooResult > 0 then
  Result = Frob(Baz) / fooResult
Else
  Result = -1
End If

Giving the user the option to name fooResult to his hearts desire.

There are probably other guard clause type situations (not just Div/0) that this would apply to, but a more general inspection is more difficult than what I can dream up at the moment.

[Vogel612]

Something like "Repeated Function Computation in boolean expression and successive block" seems appropriate. This could apply to While loops as well, I don't know whether it applies to For-Loops...

An easy false positive we want to avoid is when the arguments to the function are changed before recomputation. So at least parts of this will need to deal with the computation graph...

[daFreeMan]

Another situation to consider (as I just discovered in my own code):

If Foo(Bar, Baz) > 0 then
  Result = Conflate( Frob(Baz), Foo(Bar, Baz) )
Else
  Result = -1
End If

should yield:

Dim fooResult as Long
fooResult = Foo(Bar, Baz) 
If fooResult > 0 then
  Result = Conflate( Frob(Baz), fooResult)
Else
  Result = -1
End If

The duplicated function call is passed as a parameter to another function within the If.

I don't know enough about the parse tree to know if that would be handled in one go, but that would make for a good test case.

[rkapka]

I think invoking the same procedure within one boolean statement should also be covered, for example:

If Foo() < 0 Or Foo() > 10

[comintern]

The only problem I could foresee with a quickfix for this would if the function being evaluated has side effects. A slightly contrived example would be this:

Private Sub Foo()
    If Bar() > 0 Or Bar() > 0 Then
        MsgBox "WTF?"
    End If
End Sub

Private Function Bar() As Long
    Static Baz As Long
    Baz = Baz + 1
    Bar = Baz
End Function

[daFreeMan]

Still up to the end-user to apply the fix or an '@Ignore...

Also, that'll learn ya to minimize yer side-effecting functions!