/// <summary>
///
///
/// The difference
/// between RETURN_BLOCK and RETURN_CLOSURE *is* meaningful, as the former will attempt to return context
/// to parent scope and the latter will attempt to return context to saved scope. Mixing up the two will
/// cause memory corruption and probable execution failure.
///
/// Note that we push arguments for a call from 0...n (end), and recovered the same way, as we shift them and
/// move them to the new stack, where they will be removed in LIFO order.
/// </summary>
/// <param name="vm"></param>
/// <param name="i"></param>
internal static void CallFunction(VirtualMachine vm, Instruction i)
{
Value callable = vm.Stack.Shift();
if (callable.Type != ValueTypes.CODE_BLOCK) {
vm.RaiseError("Tried to call a non-callable value as a function");
return;
}
if (i.Type == OpCodeTypes.CALL_CLOSURE && callable.CodeBlock_Value.Closure == null) {
vm.RaiseError("Tried to call a non-closure block with lexical scope.");
return;
}
if ( (i.Type == OpCodeTypes.CALL_BLOCK || i.Type == OpCodeTypes.CALL_FUNCTION) && callable.CodeBlock_Value.Closure != null) {
vm.RaiseError("Tried to call a closure with dynamic scope.");
return;
}
// Create a new environment and shift arguments onto the stack
Environment env = null;
if (i.Type == OpCodeTypes.CALL_BLOCK) { // dynamically-scoped
env = vm.PushCurrentEnvironment();
} else if (i.Type == OpCodeTypes.CALL_FUNCTION) { // non-closure lexical scope (function)
env = vm.PushClosure();
} else if (i.Type == OpCodeTypes.CALL_CLOSURE) { // lexically-scoped (closure)
env = callable.CodeBlock_Value.Closure;
} else {
vm.RaiseError("Attempt to call block or closure with unknown opcode " + i.Type);
return;
}
for (int aInc = callable.CodeBlock_Value.ArgumentsArity.Count() - 1; aInc >= 0; aInc--) {
Value v = callable.CodeBlock_Value.ArgumentsArity[aInc];
Value arg = vm.Stack.Shift();
if (v.Type != ValueTypes.ANY_TYPE && arg.Type != v.Type) {
vm.RaiseError("Argument arity error: expected type " + arg.Type + ", saw " + v.Type);
return;
}
env.Stack.Push(arg);
}
// If we're operating in lexical scope, save the current environment so we can return
// back to it.
if (i.Type == OpCodeTypes.CALL_CLOSURE || i.Type == OpCodeTypes.CALL_FUNCTION) {
vm.ClosureStack.Add(vm.CurrentEnvironment);
}
// Finally, add the code block to the VM's function call list. We only use this to
// enable tail calls so we don't lose tex start locations and function arity
vm.FunctionCallList.Add(callable.CodeBlock_Value);
vm.CurrentEnvironment = env;
vm.ByteCode.ProgramCounter = callable.CodeBlock_Value.StartProgramCounter;
}