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LibJS: Implement basic exception throwing

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You can now throw exceptions by calling Interpreter::throw_exception().
Anyone who calls ASTNode::execute() needs to check afterwards if the
Interpreter now has an exception(), and if so, stop what they're doing
and simply return.

When catching an exception, we'll first execute the CatchClause node
if present. After that, we'll execute the finalizer block if present.

This is unlikely to be completely correct, but it's a start! :^)
This commit is contained in:
Andreas Kling 2020-03-24 14:37:39 +01:00
parent c33d4aefc3
commit 343e224aa8
11 changed files with 257 additions and 5 deletions
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41
Libraries/LibJS/AST.cpp
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@ -30,6 +30,7 @@
#include <LibJS/AST.h>
#include <LibJS/Interpreter.h>
#include <LibJS/Runtime/Array.h>
#include <LibJS/Runtime/Error.h>
#include <LibJS/Runtime/PrimitiveString.h>
#include <LibJS/Runtime/ScriptFunction.h>
#include <LibJS/Runtime/Value.h>
@ -62,16 +63,29 @@ Value ExpressionStatement::execute(Interpreter& interpreter) const
Value CallExpression::execute(Interpreter& interpreter) const
{
auto callee = m_callee->execute(interpreter);
if (interpreter.exception())
return {};
ASSERT(callee.is_object());
ASSERT(callee.as_object()->is_function());
auto* function = static_cast<Function*>(callee.as_object());
auto& call_frame = interpreter.push_call_frame();
for (size_t i = 0; i < m_arguments.size(); ++i)
for (size_t i = 0; i < m_arguments.size(); ++i) {
call_frame.arguments.append(m_arguments[i].execute(interpreter));
if (interpreter.exception())
return {};
}
if (m_callee->is_member_expression())
call_frame.this_value = static_cast<const MemberExpression&>(*m_callee).object().execute(interpreter).to_object(interpreter.heap());
if (m_callee->is_member_expression()) {
auto object_value = static_cast<const MemberExpression&>(*m_callee).object().execute(interpreter);
if (interpreter.exception())
return {};
auto this_value = object_value.to_object(interpreter.heap());
if (interpreter.exception())
return {};
call_frame.this_value = this_value;
}
auto result = function->call(interpreter, call_frame.arguments);
interpreter.pop_call_frame();
@ -464,7 +478,10 @@ void ForStatement::dump(int indent) const
Value Identifier::execute(Interpreter& interpreter) const
{
return interpreter.get_variable(string());
auto value = interpreter.get_variable(string());
if (value.is_undefined())
return interpreter.throw_exception(interpreter.heap().allocate<Error>("ReferenceError", String::format("'%s' not known", string().characters())));
return value;
}
void Identifier::dump(int indent) const
@ -745,13 +762,27 @@ void CatchClause::dump(int indent) const
body().dump(indent + 1);
}
Value TryStatement::execute(Interpreter&) const
Value TryStatement::execute(Interpreter& interpreter) const
{
interpreter.run(block(), {}, ScopeType::Try);
if (auto* exception = interpreter.exception()) {
if (m_handler) {
interpreter.clear_exception();
Vector<Argument> arguments { { m_handler->parameter(), Value(exception) } };
interpreter.run(m_handler->body(), move(arguments));
}
}
if (m_finalizer)
m_finalizer->execute(interpreter);
return {};
}
Value CatchClause::execute(Interpreter&) const
{
// NOTE: CatchClause execution is handled by TryStatement.
ASSERT_NOT_REACHED();
return {};
}