From a01721f35c830f02cdc9ca7008058de4c0fddade Mon Sep 17 00:00:00 2001
From: Leonid Ryzhyk <lryzhyk@vmware.com>
Date: Wed, 12 Jun 2019 10:23:07 -0700
Subject: [PATCH] Bug in code generation for transformers

There was a completely unnecessary hack in `Compiler.compileApplyNode`
that used name case to distinguish relation from function arguments to
transformer.  This broke when combined with module name flattening.

The fix uses proper HO type information instead.
---
 src/Language/DifferentialDatalog/Compile.hs | 7 ++++---
 src/Language/DifferentialDatalog/Syntax.hs  | 4 ++--
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/Language/DifferentialDatalog/Compile.hs b/src/Language/DifferentialDatalog/Compile.hs
index f7ebbef81..f6b252db0 100644
--- a/src/Language/DifferentialDatalog/Compile.hs
+++ b/src/Language/DifferentialDatalog/Compile.hs
@@ -958,11 +958,12 @@ compileApplyNode d Apply{..} = ApplyNode $
     "    })"                                                                                                                                                   $$
     "}; transformer}"
   where
-    inputs = concatMap (\i ->
-                         if isLower $ head i
+    Transformer{..} = getTransformer d applyTransformer
+    inputs = concatMap (\(i, ti) ->
+                         if hotypeIsFunction (hofType ti)
                             then [rname i]
                             else ["collections.get(&(" <> relId i <> ")).unwrap()", extractValue d (relType $ getRelation d i)])
-                       applyInputs
+                       (zip applyInputs transInputs)
              ++
              map (\o -> parens $ "|v|" <> mkValue' d "v" (relType $ getRelation d o)) applyOutputs
     outputs = map rname applyOutputs
diff --git a/src/Language/DifferentialDatalog/Syntax.hs b/src/Language/DifferentialDatalog/Syntax.hs
index 50e20ab86..f9e1087a3 100644
--- a/src/Language/DifferentialDatalog/Syntax.hs
+++ b/src/Language/DifferentialDatalog/Syntax.hs
@@ -794,11 +794,11 @@ instance Show HOType where
 
 hotypeIsRelation :: HOType -> Bool
 hotypeIsRelation HOTypeRelation{} = True
-hotypeIsRelation _                = True
+hotypeIsRelation _                = False
 
 hotypeIsFunction :: HOType -> Bool
 hotypeIsFunction HOTypeFunction{} = True
-hotypeIsFunction _                = True
+hotypeIsFunction _                = False
 
 -- | Type variables used in transformer declaration in the order they appear in the declaration
 hotypeTypeVars :: HOType -> [String]