B4J Question No Error message in the IDE

[Midimaster]

Today I did a copy/paste typo and the IDE did not find this bug, but handled the sub call as normal. But the variable was empty afterwards.

Lets say I would have this function:

Sub Button1_Click
    Dim Original As String ="abcdefg"
    Dim After As String  =NonSenseFunction(Original)
    Log("<" & After & "><" & Original &">")
End Sub

Sub NonSenseFunction(text As String) As String
    Return "12345"
End Sub

this would return:

<12345><abcdefg>

But if I do this typo:

Sub Button1_Click
    Dim Original As String ="abcdefg"
    Dim After As String  =NonSenseFunction(Original),Original
    Log("<" & After & "><" & Original &">")
End Sub

Sub NonSenseFunction(text As String) As String
    Return "12345"
End Sub

it returns this:

<12345><>

Is this a valid code line? Shouldn't the IDE find that error?

 

[agraham]

Yes, it is valid code. You are reDimming Original so it is now empty.

You will probably get a missing type warning if you look.

 

[stevel05]

Although you should see a warning in the log, something like:

Variable declaration type is missing. String type will be used. (warning #5)

 

[DonManfred]

Dim After As String =NonSenseFunction(Original),Original

 

[Midimaster]

Yes afterwards I recognized the warning. (It was there from the beginning, but I did not see. )

But did you expect that already inside the SUB the value was redimmed?

Sub NonSenseFunction(text As String) As String
    log("TEXT=" & text") ' shows an empty string'
    Return "12345"
End Sub

 

[agraham]

But did you expect that already inside the SUB the value was redimmed?

No, it will be compiled in this order

Dim Original As String = ""
Original = "abcdefg"
Dim After As String = ""
After = NonSenseFunction(Original)
Dim Original As String = ""
Log("<" & After & "><" & Original &">")