// Given declarations d1 and d2, a declaration error occurs when:
//
// - d2 changes the meaning of the name declared by d1, or if not that, then
// - d1 and d2 are both objects, or
// - d1 and d2 are functions that cannot be overloaded, or
// - d1 and d2 are types having different kinds.
//
// Note that d1 precedes d2 in lexical order.
//
// TODO: Would it make sense to poison the declaration so that it's not
// analyzed in subsequent passes? We could essentially replace the existing
// overload set with one containing a poisoned declaration. Any expression
// that uses that name would have an invalid type. We could then use this
// to list the places where the error affects use.
void
check_declarations(Context& cxt, Decl const& d1, Decl const& d2)
{
struct fn
{
Context& cxt;
Decl const& d2;
void operator()(Decl const& d) { lingo_unhandled(d); }
void operator()(Object_decl const& d1) { return check_declarations(cxt, d1, cast_as(d1, d2)); }
void operator()(Function_decl const& d1) { return check_declarations(cxt, d1, cast_as(d1, d2)); }
void operator()(Type_decl const& d1) { return check_declarations(cxt, d1, cast_as(d1, d2)); }
};
if (typeid(d1) != typeid(d2)) {
// TODO: Get the source location right.
error(cxt, "declaration changes the meaning of '{}'", d1.name());
note("'{}' previously declared as:", d1.name());
// TODO: Don't print the definition. It's not germaine to
// the error. If we have source locations, I wonder if we
// can just point at the line.
note("{}", d1);
throw Declaration_error();
}
apply(d1, fn{cxt, d2});
}
// Add the declaration d to the given scope.
void
declare(Context& cxt, Scope& scope, Decl& decl)
{
if (Overload_set* ovl = scope.lookup(decl.name()))
declare(cxt, *ovl, decl);
else
scope.bind(decl);
}
// Add the declaration d to the given scope.
//
// Note that this does not currently check to see if the declaration is
// valid i.e., that it does not conflict a previous declaration. This is
// only checkable if all declarations are fully elaborated (i.e., typed).
void
declare(Context& cxt, Scope& scope, Decl& decl)
{
if (Overload_set* ovl = scope.lookup(decl.name()))
ovl->push_back(decl);
else
scope.bind(decl);
}
Value
Evaluator::eval(Call_expr const* e)
{
// Evaluate the function expression.
Value v = eval(e->target());
Function_decl const* f = v.get_function();
// Evaluate each argument in turn.
Value_seq args;
args.reserve(e->arguments().size());
for (Expr const* a : e->arguments())
args.push_back(eval(a));
// Build the new call frame by pushing bindings
// from each parameter to the corresponding argument.
//
// FIXME: Since everything type-checked, these *must*
// happen to magically line up. However, it would be
// a good idea to verify.
Store_sentinel frame(*this);
for (std::size_t i = 0; i < args.size(); ++i) {
Decl* p = f->parameters()[i];
Value& v = args[i];
stack.top().bind(p->name(), v);
}
// Evaluate the function definition.
//
// TODO: Check result in case we've thrown
// an exception (for example).
Value result;
Control ctl = eval(f->body(), result);
if (ctl != return_ctl)
throw std::runtime_error("function evaluation failed");
return result;
}
Template_decl(Decl_list const& p, Decl& d)
: Decl(d.name()), parms(p), cons(nullptr), decl(&d)
{
lingo_assert(!d.context());
d.context(*this);
}