fix: make parser use only parsley parser bridge apply

src/main/wacc/parser.scala

@@ -93,10 +93,7 @@ object parser {
   private val `<ident>` = Ident(ident)
   private lazy val `<ident-or-array-elem>` =
     `<ident>` <**> (`<array-indices>` </> identity)
-  private val `<array-indices>` =
-    some("[" ~> `<expr>` <~ "]") map { indices =>
-      ArrayElem((_: Ident), indices)
-    }
+  private val `<array-indices>` = ArrayElem(some("[" ~> `<expr>` <~ "]"))
 
   // Types
   private lazy val `<type>`: Parsley[Type] =
@@ -104,7 +101,7 @@ object parser {
   private val `<base-type>` =
     (IntType from "int") | (BoolType from "bool") | (CharType from "char") | (StringType from "string")
   private lazy val `<array-type>` =
-    countSome("[" ~> "]") map { cnt => ArrayType((_: Type), cnt) }
+    ArrayType(countSome("[" ~> "]"))
   private val `<pair-type>` = "pair"
   private val `<pair-elems-type>`: Parsley[PairType] = PairType(
     "(" ~> `<pair-elem-type>` <~ ",",
@@ -112,10 +109,10 @@ object parser {
   )
   private lazy val `<pair-elem-type>` =
     (`<base-type>` <**> (`<array-type>` </> identity)) |
-      `<pair-type>` ~> ((`<pair-elems-type>` <**> `<array-type>`.explain(
-        "non-erased pair types cannot be nested"
-      )) </> UntypedPairType)
-  // TODO: better explanation here?
+      ((UntypedPairType from `<pair-type>`) <**>
+        ((`<pair-elems-type>` <**> `<array-type>`)
+          .map(arr => (_: UntypedPairType) => arr) </> identity))
+
   // Statements
   private lazy val `<program>` = Program(
     "begin" ~> many(
@@ -124,11 +121,12 @@ object parser {
     `<stmt>`.label("main program body") <~ "end"
   )
   private lazy val `<partial-func-decl>` =
-    (sepBy(`<param>`, ",") <~ ")" <~ "is" <~> `<stmt>`.guardAgainst {
-      case stmts if !stmts.isReturning => Seq("all functions must end in a returning statement")
-    } <~ "end") map { (params, stmt) =>
-      (FuncDecl((_: Type), (_: Ident), params, stmt)).tupled
-    }
+    FuncDecl(
+      sepBy(`<param>`, ",") <~ ")" <~ "is",
+      `<stmt>`.guardAgainst {
+        case stmts if !stmts.isReturning => Seq("All functions must end in a returning statement")
+      } <~ "end"
+    )
   private lazy val `<param>` = Param(`<type>`, `<ident>`)
   private lazy val `<stmt>`: Parsley[NonEmptyList[Stmt]] =
     (