Delegate parameter is invoked when it shouldn't be

[Preston159]

Description

When a function takes another function as a parameter, which in turn takes a function as a parameter, and attempts to call that function by passing in a function, Fable incorrectly calls the innermost function and passes in its return value rather than passing the function itself.

Repro code

REPL

Expected and actual results

Expected console output

• del is a function
• testFunc called

Actual console output

• testFunc called
• del is undefined
• Uncaught TypeError: del is not a function

Related information

• Fable version: 4.19.3
• Operating system: Windows 11 Pro 22631.3737

[ncave]

@Preston159 This seems to only affect delegates, as changing the type from

type DelegateType = delegate of unit -> unit

to

type DelegateType = unit -> unit

, and the call site from del.Invoke () to del () works as expected.

Not a fix, obviously, just a workaround if using delegates is not critical.

[ncave]

@Preston159 Thanks for reporting the issue, should be resolved in the next release.

[Preston159]

@ncave Happy to help. Thanks for the quick resolution, both the workaround and the fix!

[OnurGumus]

I think this change caused some regressions. Trying to come up with a repro case.

[OnurGumus]

@ncave

[ncave]

@OnurGumus Perhaps, let me know if you can find an example. The original code was done to resolve #2400.

[OnurGumus]

@ncave Hi, I reproduced the problem with minimal example and created issue. It's not related to this bug I think.

https://github.com/fable-compiler/Fable/issues/3915