[rfc] build bug in type abstraction?

[John Pritchard]

Hi,

I have a disparity between "go run" [https://go.dev/play/p/5mr5M0luZ9k?v=goprev] 

and "go build" [https://github.com/syntelos/go-type-abstraction/tree/third].  Using go version 1.21.0.

A fairly simple structure of type abstraction works on play.go.dev, but fails to build.

Comments?  Issue?

Thanks,

John

[Jason Phillips]

A few things:

* As illustrated by the output in your README, it appears your "make list" command is only compiling "main/main.go", rather than both "main/main.go" and "main/run.go"

* There can only be one main function per main package in Go, so I'm not sure how main/run.go and main/main.go are expected to coexist in a valid Go application

[Brian Candler]

On Wednesday, 16 August 2023 at 14:05:49 UTC+1 John Pritchard wrote: 

I have a disparity between "go run" [https://go.dev/play/p/5mr5M0luZ9k?v=goprev] 

and "go build" [https://github.com/syntelos/go-type-abstraction/tree/third].  Using go version 1.21.0.

I don't quite understand where "go run" comes into this.  In your Makefile, both options use "go build".

"make list" is doing something dubious:

go_sources := $(shell ls *.go)

...
list: main/main.go $(go_sources)
go build -o $@ $<

That is, I think you're trying to compile "main/main.go" and "types.go" at the same time into a single object file.  But types.go is "package types" whereas main.go is "package main".  That should give you an error; if it doesn't, that makes me suspect that go_sources is in fact empty.  The "make list" output you show in README.txt appears to confirm this:

$ make

go build -o list main/main.go    # <<< note that no additional sources are listed on the command line

In main.go, there is a pretty clear error that the compiler calls out in line 46:

main/main.go:46:15: undefined: Abstract

The corresponding source line is:

var abstract Abstract = types.Init()

and as far as I can see, it's correct: you have no type "Abstract" in package main in main.go (in otherwise, you should be referring to "types.Abstract")

[John Pritchard]

Hi Brian,

Thanks for the review.  Your basic conclusion matches mine, that the ./main/main.go:46 and ./types.go are proven in the "go run" case, and disproven in the "go build" case.  

Best,

John

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