Remove out of date new_tc_notes

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-
-Notes on the new type constraint solver
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-* 1/9/10: Consider
-    {alpha} [b] (c~b) => (alpha ~ b)
-  Then to maximise the chance of floating the equality out of
-  the implication we'd like to orient the given as (b~c) 
-  rather than (c~b).
-     See test gadt-escape1, gadt13, gadt7
-  These tests pass because of approximateImplications
-
-* Equality superclasses are not getting the right instance decl
-    indexed-types/should_compile/T2238:
-
-* Partial applications of data type families
-    indexed-types/should_compile/DerivingNewType
-  
-Functional dependencies
-~~~~~~~~~~~~~~~~~~~~~~~
-* indexed-types/Gentle
-
-RelaxedPolyRec by default
-~~~~~~~~~~~~~~~~~~~~~~~~~
-* tcfail071
-* tcfail144
-* tcfail149, 150
-
-
----------------------
-* 18/8/10: Fixed treatment of new work list from superclasses of wanteds. 
-           TODO TODO: Revisit the desugarer to deal with equalities that 
-           may mention recursive dictionaries. 
-
-* 12/8/10: Fixed proper kind checking for equalities and type family equalities.
-  NOTE: Type synonyms stay unexpanded in canonical constraints. Is this correct?
-
-* 24/7/10: canonicalisation orients meta variables
-           kind checking?
-  see trySpontaneous: need to take care with orientation 
-
-* See newWantedSCWorkList: no adding superclass equalities
-  for wanteds.  Seems ad hoc.
-
-* Happy genericTemplate notHappyAtAll needs a signature
-
-* time package needs signatures; I have put -XNoMonoLocalBinds in 
-     validate-settings.mk for now
-
-Improve error message
-~~~~~~~~~~~~~~~~~~~~~
-   FD1(normal)          <- DV: Failure to produce FD equality from *given* and top-level
-
-   FD2(normal)          <- DV: Failure to produce FC equality from two *givens*
-
-Unexpected failures:
-~~~~~~~~~~~~~~~~~~~~~
-   PolyRec(normal,hpc,optasm)     <- DV: Actually works, but we have a warning 
-                                     for -XRelaxedPolyRec deprecated flag
-   T1470(normal,optc,hpc,optasm)   
-   T2494(normal)
-   T2494-2(normal,optc,hpc,optasm)
-   T3108(normal,hpc,optasm)       <- DV: Actually works, but we have a warning for 
-                                     deprecated flags
-   T3391(normal,optc,hpc,optasm)  
-   tc003(hpc)
-   tc081(normal,optc,hpc,optasm)  <- DV: Let does not get generalized for 
-                                         *single* variable binding
-   tc089(normal,optc,hpc,optasm)       
-   tc095(normal,optc,hpc,optasm)
-   tc111(normal,optc,hpc,optasm)
-   tc113(normal,optc,hpc,optasm)  Generalize top-level var binding
-   tc127(normal,optc,hpc,optasm)  <- DV: Missing module Maybe in haskell98 package ... 
-   tc132(normal,optc,hpc,optasm)  Generalize top-level var binding
-   tc150(normal,optc,hpc,optasm)  Pattern signatures 
-   tc159(normal,optc,hpc,optasm)  <- ILL FORMED EVIDENCE (related to newtype ... deriving) 
-   tc162(normal)
-   tc168(normal,optc,hpc,optasm)  <- DV: Actually works, don't know why its reported
-   tc170(normal)
-   tc175(normal,optc,hpc,optasm)
-   tc189(normal,optc,hpc,optasm)  <- higher-rank ? 
-   tc192(normal,optc,hpc,optasm)  <- loop in desugarer
-   tc194(normal,optc,hpc,optasm)  <- polymorphic pattern signatures / higher-rank?
-   tc211(normal,optc,hpc,optasm)  <- polymorphic pattern signatures / higher-rank?
-   tc216(normal,optc,hpc,optasm)  <- ctx stack depth exceeded ... 
-   tc217(normal,optc,hpc,optasm)  
-   tc222(normal,optc,hpc,optasm)
-   tc231(normal,optc,hpc,optasm)
-   tc237(normal,optc,hpc,optasm)
-   tc243(normal,optc,hpc,optasm)      <- DV: Actually works, Definition but no signature warning 
-   tc244(normal,optc,hpc,optasm)
-
-
- 
-
-ToDo
-~~~~
-* zonking Coercions should use a function of a different name
-
-Basic setup
-~~~~~~~~~~~
-   New modules     TcSimplify (old name, but all new code)
-		   TcInteract
-                   TcCanonical (defines the TcS monad too)
-                   Constraints (both Wanted and Canonical)
-
-Existing modules   Coercion (defines operations over Coercions)
-	 	   Kind
-	 	   Type
-		   TypeRep (the representation of types, kinds, coercions)
-
-   Dead modules	   TcTyFuns
-		   TcSimplify-old.lhs (the old TcSimplify, 
-			in repo just for reference)
-
-
-Significant differences wrt the prototype
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-* "Givens"  are simply evidence variables (EvVar)
-  "Wanteds" are WantedConstraints
-  See the Implication type in TcSolverTypes.lhs
-
-  There is no sum type combining given and wanted constraints
-
-* Wanted constraints are of three flavours (see data WantedConstraint)
-	- evidenence variables: we can abstract over these
-	- implications: we can't abstract over these
-        - literal and method constraints; we can't abstract over these
-		either, and they aren't implemented yet
-
-* We use a mutable group of bindings attached to each Inplication as the
-  place to accumulate evidence for dictionaries and implicit parameters
-  (It's also vital for equality superclasses.)  Each Impliciation has a
-  TcEvBinds, defined in hsSyn/HsBinds.  The reference cell to accumulate
-  bindings into is carried by the TcS solver monad; we need to fill in 
-  evidence in the solver.
-
-* An evidence variable is
-	- a dictionary
-	- an implicit paramter
-	- a coercion variable
-  See newEvVar in Inst.lhs
-
-* The main Tc monad carries a set of untouchables
-  The unifier ensures that they are not unified
-  See Note [Unifying untouchables]
-
-* tcCheckExpr does deep-skol on expected type, and
-  then calls tcExpr with (Check ty), where ty is deeply-skolemised
-
-
--------------------
-Things to check later
--------------------
-* Monomorphism restriction puts type variables in the top level env
-  When generalising, we can't generalise over these ones (alas)
-  Consider: 
-    - Reject programs that fall under the monomorphism restriction
-        (top-level monomorphic is rare)
-    - Some hack to accept H98 programs
-
-* No orientation of tv~ty constraints; we don't need it
-
-Note [OpenSynTyCon app]
-~~~~~~~~~~~~~~~~~~~~~~~
-Given
-
-  type family T a :: * -> *
-
-the two types (T () a) and (T () Int) must unify, even if there are
-no type instances for T at all.  Should we just turn them into an
-equality (T () a ~ T () Int)?  I don't think so.  We currently try to
-eagerly unify everything we can before generating equalities; otherwise,
-we could turn the unification of [Int] with [a] into an equality, too.
-
-------------------------
-We need to both 'unBox' and zonk deferred types.  We need to unBox as
-functions, such as TcExpr.tcMonoExpr promise to fill boxes in the expected
-type.  We need to zonk as the types go into the kind of the coercion variable
-`cotv' and those are not zonked in Inst.zonkInst.  (Maybe it would be better
-to zonk in zonInst instead.  Would that be sufficient?)
-