x/sys/windows: mkwinsyscall isn't diagnosable if format.Source fails

[dagood]

I'm working on the x/sys/windows main branch (6e4d1c53), and tried to add a new syscall, but mkwinsyscall failed because of a Go syntax error in the generated code:

44:8: expected ';', found '-' (and 10 more errors)

However, there is no file with a line 44, so I can't see what it's referring to, or the additional errors. format.Source(buf.Bytes()) fails, and the generated source is only in memory at that point, so it is lost.

Expected result

When mkwinsyscall hits a formatting error, it should write the pre-formatted source to a temporary file so the error can be diagnosed.

Background

The error I hit in this case was a - in the DLL name, and fixing that is tracked over here:

• x/sys/windows: mkwinsyscall: Support - and . in DLL name #57913

[dagood]

I'm planning to submit a CL soon with a fix.

[gopherbot]

Change https://go.dev/cl/463216 mentions this issue: windows/mkwinsyscall: write source to temp file if formatting fails