Fix dep graph edges around the fulfillment cache in the tcx#31087

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bors merged 3 commits intorust-lang:masterfrom

nikomatsakis:incr-comp-fulfillment-cache

Jan 22, 2016

Commits on Jan 19, 2016

remove the `SimplifiedType` from the `DepNode` for now, just to keep
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committed

Commits on Jan 21, 2016

Revamp the fulfillment cache tracking to only cache trait-refs, which
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Indicate that trans is always dependent on typeck
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