From 18499fc9b45f52b58d3d3747f23d43421571f3d7 Mon Sep 17 00:00:00 2001
From: Harry Li <me@flandia.dev>
Date: Wed, 30 Oct 2024 12:14:06 +0800
Subject: [PATCH] Generalize `Apps`

Previsouly `Apps` unapplies the tree of form `App(App(App(id: Ident, p1), p2), p3)` to `Apps(id: Ident, p1 :: p2 :: p3 :: Nil)`. Now it unapplies this as well but also `App(App(App(tree: Tree, p1), p2), p3)` to `Apps(tree: Tree, p1 :: p2 :: p3 :: Nil)`. This is especially useful for type parameters as we want to unwarp as many of layers of `App` as we can, then unwrap the `TyApp`.
---
 .../shared/src/main/scala/hkmc2/semantics/Elaborator.scala | 7 ++-----
 hkmc2/shared/src/main/scala/hkmc2/syntax/Tree.scala        | 5 ++---
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala b/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala
index 2eb99012e..3238fa835 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala
@@ -384,7 +384,7 @@ extends Importer:
             (ctx, acc)
         newCtx.givenIn:
           go(sts, newAcc)
-      case (hd @ LetLike(`let`, Apps(id, tups), rhso, N)) :: sts if id.name.headOption.exists(_.isLower) =>
+      case (hd @ LetLike(`let`, Apps(id: Ident, tups), rhso, N)) :: sts if id.name.headOption.exists(_.isLower) =>
         val sym =
           fieldOrVarSym(LetBind, id)
         log(s"Processing `let` statement $id (${sym}) ${ctx.outer}")
@@ -428,12 +428,9 @@ extends Importer:
                 case S(t) => typeParams(t)
                 case N => (N, ctx)
               // Add parameters to context
-              val (ps, newCtx) = td.params match
-                case S(ts) => // Go through all parameter lists
-                  ts.foldLeft((Ls[Param](), newCtx1)):
+              val (ps, newCtx) = td.paramLists.foldLeft((Ls[Param](), newCtx1)):
                     case ((ps, ctx), t) => params(t)(using ctx).mapFirst(ps ++ _)
                   .mapFirst(some)
-                case N => (N, newCtx1)
               val b = rhs.map(term(_)(using newCtx))
               val r = FlowSymbol(s"‹result of ${sym}›", nextUid)
               val tdf = TermDefinition(k, sym, ps,
diff --git a/hkmc2/shared/src/main/scala/hkmc2/syntax/Tree.scala b/hkmc2/shared/src/main/scala/hkmc2/syntax/Tree.scala
index 8c721ee52..555131789 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/syntax/Tree.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/syntax/Tree.scala
@@ -157,10 +157,9 @@ object PlainTup:
   def apply(fields: Tree*): Tree = Tup(fields.toList)
 
 object Apps:
-  def unapply(t: Tree): Opt[(Ident, Ls[Tup])] = t match
+  def unapply(t: Tree): Opt[(Tree, Ls[Tup])] = t match
     case App(Apps(id, args), arg: Tup) => S(id, args :+ arg)
-    case id: Ident => S(id -> Nil)
-    case _ => N
+    case t => S(t, Nil)
 
 
 sealed abstract class OuterKind(val desc: Str)