readsig.go:66: unknown SigElemType: '9' about gomacro HOT 9 CLOSED

Can you please provide a (possibly small) package that exhibits this problem?

I could not find readsig.go or SigElemType anywhere, and for me :env works with all packages that I tried until now...

Thanks

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yeah, sorry about that. It's difficult to minimize the reproducer.
type SigElemType int is just a type in the code.

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I have an idea - it comes from the observation that :env only calls the String() method (if available) of the constants, variables, functions and types declared in the package.

Maybe the package contains some SigElemType constants, and SigElemType has a method String() that panics if the receiver is not one of the "known good" constants, and the SigElemType constant '9' is declared but is not among the "known good" ones?

Checking line 66 of readsig.go, where the panic happens, could help verifying if this is the case...

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Yes, you were right, @cosmos72. I was missing some constants in a big switch doing String() string output. When I filled in the missing cases, then :env is happy.

Partial repro here:

https://github.com/glycerine/repro

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obviously this is user error on my part. My code should have had those constants. I'm sure rob pike published a tool at one point to generate those String() methods for us automagically, but I can't remember what it is called to find it again.

Anyway.

I'll leave this open--for you to close when you wish-- just in case something occurs to you that would make such confusion over cause less likely in the future. I'm not sure what to suggest other than to point out to me that the crash was in my code and not in gomacro; gomacro was invoking my code during :env -- that's the part I didn't realize.

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Thanks :) it makes sense that a big switch could miss some cases.

I will harden :env against panics in String() and GoString() methods of the constants, variables, types and functions present in the package

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About autogenerating the String() method:

if you do not find anything already implemented for the purpose, gomacro has extensive (although poorly documented) code generation features - it could be a nice and simple example, if I have time I will implement it and reply here

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Commit 6eee083 should fix this problem.

Anyway, as you wrote in https://github.com/glycerine/repro, a panic in the String() method usually has a different and non-fatal effect: :env simply shows the panic message instead of the constant or variable, as for example:

ArrayFSMTy      = %!v(PANIC=unknown SigElemType: '9')	// repro.SigElemType

so, lacking a clear analysis, I am still not 100% convinced that commit 6eee083 is enough.

Can you try updating gomacro and re-running :env on your private package?

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Confirmed: the panics no longer crash gomacro. Looks good. Thanks again!

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