Format generated source code before writing it to the destination

[peterstace]

No description provided.

[dsymonds]

let's make this

g := new(generator)

[dsymonds]

This looks fine. Just a few nits.

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[peterstace]

I've signed the CLA.

[googlebot]

CLAs look good, thanks!

[dsymonds]

Merged in d581abf.