Merge branch 'master' of http://darcs.haskell.org/ghc into ghc-generics

[ghc-hetmet.git] / compiler / hsSyn / HsLit.lhs

diff --git a/compiler/hsSyn/HsLit.lhs b/compiler/hsSyn/HsLit.lhs
index 0874dda..4a565ff 100644 (file)
--- a/compiler/hsSyn/HsLit.lhs
+++ b/compiler/hsSyn/HsLit.lhs
@@ -63,8 +63,7 @@ instance Eq HsLit where
 data HsOverLit id      -- An overloaded literal
   = OverLit {
        ol_val :: OverLitVal, 
-       ol_rebindable :: Bool,          -- True <=> rebindable syntax
-                                       -- False <=> standard syntax
+       ol_rebindable :: Bool,          -- Note [ol_rebindable]
        ol_witness :: SyntaxExpr id,    -- Note [Overloaded literal witnesses]
        ol_type :: PostTcType }
   deriving (Data, Typeable)
@@ -79,6 +78,19 @@ overLitType :: HsOverLit a -> Type
 overLitType = ol_type
 \end{code}
 
+Note [ol_rebindable]
+~~~~~~~~~~~~~~~~~~~~
+The ol_rebindable field is True if this literal is actually 
+using rebindable syntax.  Specifically:
+
+  False iff ol_witness is the standard one
+  True  iff ol_witness is non-standard
+
+Equivalently it's True if
+  a) RebindableSyntax is on
+  b) the witness for fromInteger/fromRational/fromString
+     that happens to be in scope isn't the standard one
+
 Note [Overloaded literal witnesses]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *Before* type checking, the SyntaxExpr in an HsOverLit is the
@@ -89,7 +101,7 @@ This witness should replace the literal.
 
 This dual role is unusual, because we're replacing 'fromInteger' with 
 a call to fromInteger.  Reason: it allows commoning up of the fromInteger
-calls, which wouldn't be possible if the desguarar made the application
+calls, which wouldn't be possible if the desguarar made the application.
 
 The PostTcType in each branch records the type the overload literal is
 found to have.