[commit: ghc] master: Comments about TyBinders (only) (563d64f)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/563d64fd067219a0e42c5f1c83830d2847243f6f/ghc

>---------------------------------------------------------------

commit 563d64fd067219a0e42c5f1c83830d2847243f6f
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Fri Jan 13 15:58:06 2017 +0000

    Comments about TyBinders (only)


>---------------------------------------------------------------

563d64fd067219a0e42c5f1c83830d2847243f6f
 compiler/types/TyCoRep.hs | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/compiler/types/TyCoRep.hs b/compiler/types/TyCoRep.hs
index 63aba3c..ef6917a 100644
--- a/compiler/types/TyCoRep.hs
+++ b/compiler/types/TyCoRep.hs
@@ -409,8 +409,9 @@ same kinds.
 -- ('Named') or nondependent ('Anon'). They may also be visible or not.
 -- See Note [TyBinders]
 data TyBinder
-  = Named TyVarBinder
-  | Anon Type   -- Visibility is determined by the type (Constraint vs. *)
+  = Named TyVarBinder   -- A type-lambda binder
+  | Anon Type           -- A term-lambda binder
+                        -- Visibility is determined by the type (Constraint vs. *)
   deriving Data.Data
 
 -- | Remove the binder's variable from the set, if the binder has
@@ -437,7 +438,7 @@ A TyBinder represents the type of binders -- that is, the type of an
 argument to a Pi-type. GHC Core currently supports two different
 Pi-types:
 
- * A non-dependent function,
+ * A non-dependent function type,
    written with ->, e.g. ty1 -> ty2
    represented as FunTy ty1 ty2
 
@@ -447,12 +448,8 @@ Pi-types:
 
 Both Pi-types classify terms/types that take an argument. In other
 words, if `x` is either a function or a polytype, `x arg` makes sense
-(for an appropriate `arg`). It is thus often convenient to group
-Pi-types together.  This is ForAllTy.
+(for an appropriate `arg`).
 
-The two constructors for TyBinder sort out the two different possibilities.
-`Named` builds a polytype, while `Anon` builds an ordinary function.
-(ForAllTy (Anon arg) res used to be called FunTy arg res.)
 
 Note [TyBinders and ArgFlags]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~