When constant values change but stringer has not
been run again, we can get misleading string values.
Protect against this by generating code that will fail
with a compiler error when this happens.
Most compilers should be smart enough to omit the
code containing the checks.
Change-Id: I7a36d20f014cba0e7d88851d1b649a098ee30d76
Reviewed-on: https://go-review.googlesource.com/c/tools/+/163637
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
