go2gen

go2gen

go2gen is a prototype implementation of the proposed Go 2 check/handle keywords. It transpiles invalid .go2 files with check/handle syntax into valid .go file counterparts.

go2gen is just a playful experiment, and is not meant to be used seriously. I personally enjoyed being able to get a feeling for what using check/handle would be like; however, the extra build step and lack of immediate error highlighting disqualify it from actual use.

PS: In VS Code, check/handle don't seem to interfere with syntax highlighting; to get it, add

"files.associations": {
        "*.go2": "go"
},

to your user settings.

Usage

go get github.com/joelterry/go2gen

To transpile .go2 files in the current directory:

$ go2gen

To transpile .go2 files in a specific directory:

$ go2gen DIR_PATH

I progressively type-check the generated package to create variable names that include their types, so the program can't be run on a per-file basis.

Discrepancies

Check only allowed within blocks

Check expressions are currently only valid in statements within blocks: all "clauses" (not sure if that's the right word) of if/else if, switch, and select statements are ignored. The reasoning for switch and select is that the control flow is not explicit, and therefore can't be implemented with transpilation. If/else if on the other hand has explicit control flow, but I opted to ignore it anyways. Else if would require extra nesting, and if would have been the only exception to the rule, which might be confusing.

Handler chain is not called like a function

The draft states that "the handler chain appears to the runtime as if it were called by the enclosing function, in its own stack frame." In this implementation, handler chain code is inserted directly, without an enclosing anonymous function.

Errors

If the code is invalid, it's likely that a standard parse error will be passed along (which will be unhelpful, but will at least give you a line number).

Comments

Comments are currently not preserved. The standard Go AST doesn't handle modification well RE comments (https://github.com/golang/go/issues/20744). While https://github.com/dave/dst was initially a great solution, I later decided to progressively type-check the package, which required the standard AST.