Fix bug in arity checker with pi types (#2300)

All variables bound in a pi type were assumed to be of arity unit. This
pr fixes that.

- Closes #2296

src/Juvix/Compiler/Internal/Translation/FromInternal/Analysis/ArityChecking/Checker.hs

@@ -166,11 +166,8 @@ checkFunctionClause ari cl = do
 simplelambda :: a
 simplelambda = error "simple lambda expressions are not supported by the arity checker"
 
-withLocalTypeVar :: Members '[Reader LocalVars] r => VarName -> Sem r a -> Sem r a
-withLocalTypeVar v = withLocalVar v ArityUnit
-
-withLocalVar :: Members '[Reader LocalVars] r => VarName -> Arity -> Sem r a -> Sem r a
-withLocalVar v = local . withArity v
+withLocalVar :: Members '[Reader LocalVars] r => Arity -> VarName -> Sem r a -> Sem r a
+withLocalVar ari v = local (withArity v ari)
 
 withEmptyLocalVars :: Sem (Reader LocalVars ': r) a -> Sem r a
 withEmptyLocalVars = runReader emptyLocalVars
@@ -547,7 +544,8 @@ checkExpression hintArity expr = case expr of
     goFunction :: Function -> Sem r Function
     goFunction (Function l r) = do
       l' <- goFunctionParameter l
-      r' <- maybe id withLocalTypeVar (l ^. paramName) (checkType r)
+      let ari = typeArity (l' ^. paramType)
+      r' <- maybe id (withLocalVar ari) (l ^. paramName) (checkType r)
       return (Function l' r')
       where
         goFunctionParameter :: FunctionParameter -> Sem r FunctionParameter

test/Typecheck/Positive.hs

@@ -272,7 +272,11 @@ tests =
     posTest
       "Omit Type annotation"
       $(mkRelDir ".")
-      $(mkRelFile "OmitType.juvix")
+      $(mkRelFile "OmitType.juvix"),
+    posTest
+      "Issue 2296 (Pi types with lhs arity other than unit)"
+      $(mkRelDir "issue2296")
+      $(mkRelFile "M.juvix")
   ]
     <> [ compilationTest t | t <- Compilation.tests
        ]

tests/positive/issue2296/M.juvix

@@ -0,0 +1,4 @@
+module M;
+
+f : (F : Type → Type) → (A : Type) → F A → F A;
+f _ _ x := x;

tests/positive/issue2296/juvix.yaml

@@ -0,0 +1,4 @@
+dependencies:
+- .juvix-build/stdlib/
+name: issue2296
+version: 0.0.0