Partial type signatures + extensions panic

Partial type signatures combined with the following GHC extensions cause a panic:

class C a where default f :: _       -- DefaultSignatures

instance Num Bool where negate :: _  -- InstanceSigs

deriving instance _                  -- StandaloneDeriving

Trac metadata

Trac field	Value
Version	7.9
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	thomasw
Operating system
Architecture

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Partial type signatures + extensions panic