debuginfo: Fix type description generic enum discriminants.

[michaelwoerister]

This fixes an issue that @alexcrichton found while trying to upgrade LLVM: So far the code has assumed that the type of a generic enum's discriminant always was the same, regardless of any type arguments. This is not true. An Option<i16> will have a 16 bit discriminant, while an Option<i32> will have a 32 bit discriminant. This PR fixes this.

[rust-highfive]

r? @Aatch

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[alexcrichton]

@bors: r+ f9a20bb

Thanks!

[tamird]

An Option will have a 16 bit discriminant, while an Option will have a 32 bit discriminant.

Something wrong with this sentence

[Manishearth]

This might be causing a test failure http://buildbot.rust-lang.org/builders/auto-mac-64-opt/builds/5712

[bors]

⌛ Testing commit f9a20bb with merge b465213...

[Manishearth]

@bors r-

[Manishearth]

@bors r- force

(fails tests)

[alexcrichton]

I'm gonna land this as part of #27076 and just ignore the LLDB half of things for now (this is being tested on gdb and fixes bugs elsewhere in the upgrade). I'll open an issue about dealing with the LLDB failure, however, so we can be sure to keep track of it as it definitely looks like it should be investigated!

[Manishearth]

Sure!

(was just r-ing so it won't clog up the queue 😄 )