some fixes for zero argument functions, test_code.lang improvements

src/print_visitor.cpp

@@ -597,7 +597,7 @@ void PrintVisitor::Visit(FunctionType* node) {
   out_ << "[FunctionType] (";
   bool is_first = true;
   for (auto& type : node->types) {
-    if (!is_first) {
+    if (!is_first || node->types.size() == 1) {
       out_ << " -> ";
     }
     is_first = false;

src/typed_print_visitor.cpp

@@ -849,7 +849,7 @@ void TypedPrintVisitor::Visit(FunctionType* node) {
   out_ << "] (";
   bool is_first = true;
   for (auto& type : node->types) {
-    if (!is_first) {
+    if (!is_first || node->types.size() == 1) {
       out_ << " -> ";
     }
     is_first = false;

tests/test_code.lang

@@ -1,5 +1,106 @@
-decl print : String -> Unit
+basic Float
+basic Int
+basic String
+basic Char
+basic Bool
+basic Unit
+
+// bool functions
+
+decl not : Bool -> Bool
+def not : x =
+  match x with
+    | true -> false
+    | false -> true
+
+decl ( && ) : Bool -> Bool -> Bool
+def ( && ) : x y =
+  match x with
+    | true -> (
+      match y with
+        | true -> true
+        | false -> false
+    )
+    | false -> false
+
+decl ( || ) : Bool -> Bool -> Bool
+def ( || ) : x y =
+  match x with
+    | true -> true
+    | false -> (
+      match y with
+        | true -> true
+        | false -> false
+    )
+
+// Eq typeclass
+
+typeclass Eq =
+  & ( == ) : Eq -> Bool
+  & ( != ) : Eq -> Bool
+
+namespace const Eq {
+  def ( != ) : x = not: (self == x)
+}
+
+// Ord typeclass
+
+struct Order =
+  | EQ
+  | LT
+  | GT
+
+typeclass (Ord : #Eq) =
+  & compare: Ord -> Order
+  & ( < ) : Ord -> Bool
+  & ( >= ) : Ord -> Bool
+  & ( > ) : Ord -> Bool
+  & ( <= ) : Ord -> Bool
+  & min : Ord -> Ord
+  & max : Ord -> Ord
+
+namespace var Ord {
+  def compare : x =
+    if self == x then $EQ
+    elif self < x then $LT
+    else $GT
+
+  def ( >= ) : x = not: (self < x)
+  def ( > ) : x = x < self
+  def ( <= ) : x = not: (x < self)
+  def min : x = if self < x then self else x
+  def max : x = if self < x then x else self
+}
+
+//
+
+typeclass Show =
+  & show : -> String
+
+typeclass Read =
+  & read : String -> Read
+
+typeclass Debug =
+  & debug : -> String
+
+//
+
+// Enum typeclass
+
+typeclass Enum =
+  & succ : Enum -> (Optional Enum)
+  & pred : Enum -> (Optional Enum)
+
+//
+
 decl ( -- ) : Int -> Int -> Int_0
+def ( -- ) : begin end = {
+  var current = begin
+  return (while current < end do {
+    ; current += 1
+    return current - 1
+  })
+}
 
 decl func : String -> Int
 def func : s = {