Move mutation of program to the final step.
+ 2 assertions;
+ switches.go: comment fix.
LGTM=gri
R=gri
CC=golang-codereviews
https://golang.org/cl/61510044
This is (a) more efficient and (b) avoids the need for
constant error handling, since buffer writes can't fail.
Also:
- added WriteFunction and WritePackage functions,
similar to types.WriteFoo.
- *Function and *Package now implement io.WriterTo.
LGTM=gri
R=gri
CC=golang-codereviews
https://golang.org/cl/57930044
Alan Donovan
Robert Griesemer