Fix issue with calling generics

Issue #80 identified a case where the resolver would hang when calling a
generic function with a parameter whose name matched the name of the
argument.

This occurred due to the order of resolution. Since we resolved bindings
in a depth-first fashion, we simply ended up resolving a generic
parameter to itself.

One way to resolve this would have been to synthesize new names for each
parameter in the scope of a local binding. But generating names and
ensuring they are all unique is annoying. Instead, we switch the order
of resolution. When binding generic args, we first resolve the arguments
before traversing the body.

That is, for a replacement series

int -> x -> x

We previously did

int -> (x -> x)

whereas now we do

(int -> x) -> x

Since the top-level (LHS) is always concrete, this process must
terminate.

Author: nc6

example/cddl-files/issue80-min.cddl

@@ -0,0 +1,8 @@
+main = test<int, int>
+set<x> = [x]
+test<x, x1> = [
+	1,
+	x,
+	set<x>
+]
+

src/Codec/CBOR/Cuddle/CDDL/Resolve.hs

@@ -25,7 +25,6 @@
 --    generic arguments bound.
 module Codec.CBOR.Cuddle.CDDL.Resolve (
   buildResolvedCTree,
-  monoCTree,
   buildRefCTree,
   asMap,
   buildMonoCTree,
@@ -323,10 +322,10 @@ postludeBinding =
     , (Name "null" mempty, PTNil)
     ]
 
-data BindingEnv poly f = BindingEnv
+data BindingEnv poly f g = BindingEnv
   { global :: Map.Map Name (poly (CTree.Node f))
   -- ^ Global name bindings via 'RuleDef'
-  , local :: Map.Map Name (CTree.Node f)
+  , local :: Map.Map Name (CTree.Node g)
   -- ^ Local bindings for generic parameters
   }
   deriving (Generic)
@@ -354,7 +353,7 @@ deriving instance Eq (CTreeRoot DistRef)
 instance Hashable (CTreeRoot DistRef)
 
 resolveRef ::
-  BindingEnv (ParametrisedWith [Name]) OrRef ->
+  BindingEnv (ParametrisedWith [Name]) OrRef OrRef ->
   CTree.Node OrRef ->
   Either NameResolutionFailure (DistRef (CTree DistRef))
 resolveRef env (It a) = DIt <$> resolveCTree env a
@@ -375,7 +374,7 @@ resolveRef env (Ref n args) = case Map.lookup n postludeBinding of
       Nothing -> Left $ UnboundReference n
 
 resolveCTree ::
-  BindingEnv (ParametrisedWith [Name]) OrRef ->
+  BindingEnv (ParametrisedWith [Name]) OrRef OrRef ->
   CTree OrRef ->
   Either NameResolutionFailure (CTree DistRef)
 resolveCTree e = CTree.traverseCTree (resolveRef e)
@@ -407,7 +406,7 @@ deriving instance
   Show (poly (CTree.Node MonoRef)) =>
   Show (CTreeRoot' poly MonoRef)
 
-type MonoEnv = BindingEnv (ParametrisedWith [Name]) DistRef
+type MonoEnv = BindingEnv (ParametrisedWith [Name]) DistRef MonoRef
 
 -- | We introduce additional bindings in the state
 type MonoState = Map.Map Name (CTree.Node MonoRef)
@@ -432,10 +431,10 @@ newtype MonoM a = MonoM
   deriving
     ( HasSource
         "local"
-        (Map.Map Name (CTree.Node DistRef))
+        (Map.Map Name (CTree.Node MonoRef))
     , HasReader
         "local"
-        (Map.Map Name (CTree.Node DistRef))
+        (Map.Map Name (CTree.Node MonoRef))
     )
     via Field
           "local"
@@ -490,11 +489,12 @@ synthMono n@(Name origName _) args =
           Just (Unparametrised _) -> throwNR $ MismatchingArgs n []
           Just (Parametrised r params') ->
             if length params' == length args
-              then
-                let localBinds = Map.fromList $ zip params' args
-                 in Reader.local @"local" (Map.union localBinds) $ do
-                      foo <- resolveGenericRef r
-                      modify @"synth" $ Map.insert fresh foo
+              then do
+                rargs <- traverse resolveGenericRef args
+                let localBinds = Map.fromList $ zip params' rargs
+                Reader.local @"local" (Map.union localBinds) $ do
+                  foo <- resolveGenericRef r
+                  modify @"synth" $ Map.insert fresh foo
               else throwNR $ MismatchingArgs n params'
           Nothing -> throwNR $ UnboundReference n
         pure fresh
@@ -512,7 +512,7 @@ resolveGenericRef (RuleRef n margs) =
 resolveGenericRef (GenericRef n) = do
   localBinds <- ask @"local"
   case Map.lookup n localBinds of
-    Just node -> resolveGenericRef node
+    Just node -> pure node
     Nothing -> throwNR $ UnboundReference n
 
 resolveGenericCTree ::