From 829c9b9494ad073ecc5bf3dcef8355ba3fcf8d9a Mon Sep 17 00:00:00 2001
From: Brian Huffman <huffman@galois.com>
Date: Wed, 19 Jun 2019 10:30:28 -0700
Subject: [PATCH] Support lhs indexing on record field constructors and
 updaters.

For example, we can now write

    foo = { f : [8] -> [4][4][8] }
    foo = { f i @ j @ k = i + j + k }
---
 src/Cryptol/Parser.y              | 8 ++++++--
 src/Cryptol/Parser/ParserUtils.hs | 8 ++++----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/Cryptol/Parser.y b/src/Cryptol/Parser.y
index d830d364..2e540bc6 100644
--- a/src/Cryptol/Parser.y
+++ b/src/Cryptol/Parser.y
@@ -538,8 +538,12 @@ rec_expr :: { Expr PName }
 field_expr             :: { UpdField PName }
   : selector field_how expr     { UpdField $2 [$1] $3 }
   | sels field_how expr         { UpdField $2 $1 $3 }
-  | sels apats field_how expr   { UpdField $3 $1 (EFun (reverse $2) $4) }
-  | selector apats field_how expr   { UpdField $3 [$1] (EFun (reverse $2) $4) }
+  | sels apats_indices field_how expr
+                                { UpdField $3 $1 (EFun (reverse (fst $2))
+                                                  (mkGenerate (reverse (snd $2)) $4)) }
+  | selector apats_indices field_how expr
+                                { UpdField $3 [$1] (EFun (reverse (fst $2))
+                                                    (mkGenerate (reverse (snd $2)) $4)) }
 
 field_how :: { UpdHow }
   : '='                          { UpdSet }
diff --git a/src/Cryptol/Parser/ParserUtils.hs b/src/Cryptol/Parser/ParserUtils.hs
index bbcb850e..9bc2a022 100644
--- a/src/Cryptol/Parser/ParserUtils.hs
+++ b/src/Cryptol/Parser/ParserUtils.hs
@@ -438,11 +438,11 @@ mkIndexedDecl f (ps, ixs) e =
              }
   where
     rhs :: Expr PName
-    rhs = foldr mkGenerate e (reverse ixs)
-
-    mkGenerate :: Pattern PName -> Expr PName -> Expr PName
-    mkGenerate pat body = EGenerate (EFun [pat] body)
+    rhs = mkGenerate (reverse ixs) e
 
+mkGenerate :: [Pattern PName] -> Expr PName -> Expr PName
+mkGenerate pats body =
+  foldr (\pat e -> EGenerate (EFun [pat] e)) body pats
 
 mkIf :: [(Expr PName, Expr PName)] -> Expr PName -> Expr PName
 mkIf ifThens theElse = foldr addIfThen theElse ifThens