fix: count subscript parameters in wrenMakeCallHandle for bracket signatures

Add missing loop to count underscore parameters in subscript operator signatures
starting with '['. Previously only counted parameters in parenthesized signatures,
causing incorrect arity for methods like `[_,_]` and `[_,_]=(_)`. Also adds
validation assertions for null and empty signatures, and extends test coverage
with unary, binary, subscript, and subscript-set operator call handles.

test/api/call.c

@@ -13,7 +13,11 @@ void callRunTests(WrenVM* vm)
   WrenValue* zero = wrenMakeCallHandle(vm, "zero()");
   WrenValue* one = wrenMakeCallHandle(vm, "one(_)");
   WrenValue* two = wrenMakeCallHandle(vm, "two(_,_)");
-  
+  WrenValue* unary = wrenMakeCallHandle(vm, "-");
+  WrenValue* binary = wrenMakeCallHandle(vm, "-(_)");
+  WrenValue* subscript = wrenMakeCallHandle(vm, "[_,_]");
+  WrenValue* subscriptSet = wrenMakeCallHandle(vm, "[_,_]=(_)");
+
   // Different arity.
   wrenEnsureSlots(vm, 1);
   wrenSetSlotValue(vm, 0, callClass);
@@ -34,6 +38,29 @@ void callRunTests(WrenVM* vm)
   wrenSetSlotDouble(vm, 2, 2.0);
   wrenCall(vm, two);
   
+  // Operators.
+  wrenEnsureSlots(vm, 1);
+  wrenSetSlotValue(vm, 0, callClass);
+  wrenCall(vm, unary);
+
+  wrenEnsureSlots(vm, 2);
+  wrenSetSlotValue(vm, 0, callClass);
+  wrenSetSlotDouble(vm, 1, 1.0);
+  wrenCall(vm, binary);
+  
+  wrenEnsureSlots(vm, 3);
+  wrenSetSlotValue(vm, 0, callClass);
+  wrenSetSlotDouble(vm, 1, 1.0);
+  wrenSetSlotDouble(vm, 2, 2.0);
+  wrenCall(vm, subscript);
+  
+  wrenEnsureSlots(vm, 4);
+  wrenSetSlotValue(vm, 0, callClass);
+  wrenSetSlotDouble(vm, 1, 1.0);
+  wrenSetSlotDouble(vm, 2, 2.0);
+  wrenSetSlotDouble(vm, 3, 3.0);
+  wrenCall(vm, subscriptSet);
+
   // Returning a value.
   WrenValue* getValue = wrenMakeCallHandle(vm, "getValue()");
   wrenEnsureSlots(vm, 1);
@@ -89,4 +116,8 @@ void callRunTests(WrenVM* vm)
   wrenReleaseValue(vm, two);
   wrenReleaseValue(vm, getValue);
   wrenReleaseValue(vm, value);
+  wrenReleaseValue(vm, unary);
+  wrenReleaseValue(vm, binary);
+  wrenReleaseValue(vm, subscript);
+  wrenReleaseValue(vm, subscriptSet);
 }

test/api/call.wren

@@ -21,12 +21,32 @@ class Call {
   }
 
   static getValue() { ["a", "b"] }
+
+  static - {
+    System.print("unary")
+  }
+
+  static -(arg) {
+    System.print("binary %(arg)")
+  }
+
+  static [one, two] {
+    System.print("subscript %(one) %(two)")
+  }
+
+  static [one, two]=(three) {
+    System.print("subscript set %(one) %(two) %(three)")
+  }
 }
 
 // expect: noParams
 // expect: zero
 // expect: one 1
 // expect: two 1 2
+// expect: unary
+// expect: binary 1
+// expect: subscript 1 2
+// expect: subscript set 1 2 3
 
 // expect: two true false
 // expect: two 1.2 3.4