Constant gives error when used in concatenation

PaulS

In my case I want to concatenate a filename and an extension. The extension is a constant with the value ".svg"

Var iconfile As String = IconName + file_extension_svg

I get error: Undefined identifier 'file_extension_svg'.

bgrommes

So this is a problem specific to concatenation, in that you can simply assign or compare the constant? I looked at my code base which has a lot of constants within classes like this. One of my projects does successfully use constants in concatenation. Literally the only thing I'm doing different is using the upper-case naming convention, like if you had done FILE_EXTENSION_SVG -- but of course that shouldn't matter.

Are you running version 26.8.3 of Studio?

PaulS

Yes, I'm running Objo version 26.8.3.
I noticed this behavior in the past and worked around it. But now I thought that this shouldn't happen.

PaulS

I changed the constant having an uppercase constant name but that didn't work either.

When I moved the constant to an other module and used the constant by adding the module (in my case modGlobal) before the constant, all of sudden the constant was found (no error).

Var iconfile As String = IconName + modGlobal.file_extension_svg

bgrommes

I believe the ability to make shared constants was a recent change -- perhaps it broke something at the class level. The only other thing I can think of is to remove and redefine the class level constant and see if that shakes it loose. I'm sure Garry will weigh in here shortly!

Garry

Thanks for the detailed report, PaulS. That was a real bug, not anything you were doing wrong, and it's now fixed for the next release: https://feedback.objo.dev/bug/1143

What was happening

The error wasn't actually specific to concatenation. Any bare reference to a module constant or variable from a method failed if the member was declared after the method in the module:

Module modGlobal
    Sub Build(IconName As String)
        Var iconfile As String = IconName + file_extension_svg   # "Undefined identifier"
    End Sub

    Const file_extension_svg As String = ".svg"
End Module

The generated code and the runtime were fine with this all along - it was purely a compile-time resolution bug. The type checker resolves bare module members through the lexical scope as it reads the file top-to-bottom, and the module fallback path only knew about methods, not constants or variables. So:

A constant or variable declared after the method that used it wasn't visible → Undefined identifier.
Declaring it before the method worked.
Qualifying it (modGlobal.file_extension_svg) worked, because qualified access uses an order-independent member table.
Class constants were never affected because they take a different (order-independent) resolution path.

bgrommes, this is why your class-level constants worked — and why PaulS's workaround (moving the constant to modGlobal and qualifying it) made it vanish.

The fix

Module methods can now reference module constants and variables by their bare name regardless of declaration order - matching how module-to-module method calls already behaved, and how class members behave. Your original line now compiles as written:

Module modGlobal
    Sub Build(IconName As String)
        Var iconfile As String = IconName + file_extension_svg   # works now
    End Sub

    Const file_extension_svg As String = ".svg"
End Module

Of course end users can't really determine the order declarations are processed - the IDE handles this so this was a nasty bug that has now been squashed.