private static void Field(Compiler c, bool allowAssignment)
{
// Initialize it with a fake value so we can keep parsing and minimize the
// number of cascaded errors.
int field = 255;
ClassCompiler enclosingClass = c.GetEnclosingClass();
if (enclosingClass == null)
{
c.Error("Cannot reference a field outside of a class definition.");
}
else if (enclosingClass.IsStaticMethod)
{
c.Error("Cannot use an instance field in a static method.");
}
else
{
// Look up the field, or implicitly define it.
string fieldName = c._parser.Source.Substring(c._parser.Previous.Start, c._parser.Previous.Length);
field = enclosingClass.Fields.IndexOf(fieldName);
if (field < 0)
{
enclosingClass.Fields.Add(fieldName);
field = enclosingClass.Fields.IndexOf(fieldName);
}
if (field >= MaxFields)
{
c.Error(string.Format("A class can only have {0} fields.", MaxFields));
}
}
// If there's an "=" after a field name, it's an assignment.
bool isLoad = true;
if (c.Match(TokenType.Eq))
{
if (!allowAssignment) c.Error("Invalid assignment.");
// Compile the right-hand side.
c.Expression();
isLoad = false;
}
// If we're directly inside a method, use a more optimal instruction.
if (c._parent != null && c._parent._enclosingClass == enclosingClass)
{
c.EmitByteArg(isLoad ? Instruction.LoadFieldThis : Instruction.StoreFieldThis,
field);
}
else
{
c.LoadThis();
c.EmitByteArg(isLoad ? Instruction.LoadField : Instruction.StoreField, field);
}
}
private static void super_(Compiler c, bool allowAssignment)
{
ClassCompiler enclosingClass = c.GetEnclosingClass();
if (enclosingClass == null)
{
c.Error("Cannot use 'super' outside of a method.");
}
else if (enclosingClass.IsStaticMethod)
{
c.Error("Cannot use 'super' in a static method.");
}
c.LoadThis();
// TODO: Super operator calls.
// See if it's a named super call, or an unnamed one.
if (c.Match(TokenType.Dot))
{
// Compile the superclass call.
c.Consume(TokenType.Name, "Expect method name after 'super.'.");
c.NamedCall(allowAssignment, Instruction.Super0);
}
else if (enclosingClass != null)
{
// No explicit name, so use the name of the enclosing method. Make sure we
// check that enclosingClass isn't null first. We've already reported the
// error, but we don't want to crash here.
c.MethodCall(Instruction.Super0, enclosingClass.MethodName, enclosingClass.MethodLength);
}
}
private static void this_(Compiler c, bool allowAssignment)
{
if (c.GetEnclosingClass() == null)
{
c.Error("Cannot use 'this' outside of a method.");
return;
}
c.LoadThis();
}
// Compiles a variable name or method call with an implicit receiver.
private static void Name(Compiler c, bool allowAssignment)
{
// Look for the name in the scope chain up to the nearest enclosing method.
Token token = c._parser.Previous;
Instruction loadInstruction;
string varName = c._parser.Source.Substring(token.Start, token.Length);
int index = c.ResolveNonmodule(varName, token.Length, out loadInstruction);
if (index != -1)
{
c.Variable(allowAssignment, index, loadInstruction);
return;
}
// TODO: The fact that we return above here if the variable is known and parse
// an optional argument list below if not means that the grammar is not
// context-free. A line of code in a method like "someName(foo)" is a parse
// error if "someName" is a defined variable in the surrounding scope and not
// if it isn't. Fix this. One option is to have "someName(foo)" always
// resolve to a self-call if there is an argument list, but that makes
// getters a little confusing.
// If we're inside a method and the name is lowercase, treat it as a method
// on this.
if (IsLocalName(varName) && c.GetEnclosingClass() != null)
{
c.LoadThis();
c.NamedCall(allowAssignment, Instruction.Call0);
return;
}
// Otherwise, look for a module-level variable with the name.
int module = c._parser.Module.Variables.FindIndex(v => v.Name == varName);
if (module == -1)
{
if (IsLocalName(varName))
{
c.Error("Undefined variable.");
return;
}
// If it's a nonlocal name, implicitly define a module-level variable in
// the hopes that we get a real definition later.
module = c._parser.Vm.DeclareVariable(c._parser.Module, varName);
if (module == -2)
{
c.Error("Too many module variables defined.");
}
}
c.Variable(allowAssignment, module, Instruction.LoadModuleVar);
}