Changeable lexer/parser (like DynFlags.log_action)

It would be very convenient for projects such as 'Haskell Server Pages' if the GHC library allowed the user to supply his own lexer and parser.

Trac metadata

Trac field	Value
Version	6.4.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	low
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Multiple
Architecture	Multiple