lean2/src/library/elaborator/elaborator_exception.h
Leonardo de Moura d87ad9eb7e refactor(util/lua): propagate C++ Lean exceptions in Lua
The following call sequence is possible:
C++ -> Lua -> C++ -> Lua -> C++

The first block of C++ is the Lean main function.
The main function invokes the Lua interpreter.
The Lua interpreter invokes a C++ Lean API.
Then the Lean API invokes a callback implemented in Lua.
The Lua callback invokes another Lean API.
Now, suppose the Lean API throws an exception.
We want the C++ exception to propagate over the mixed C++/Lua call stack.
We use the clone/rethrow exception idiom to achieve this goal.

Before this commit, the C++ exceptions were converted into strings
using the method what(), and then they were propagated over the Lua
stack using lua_error. A lua_error was then converted into a lua_exception when going back to C++.
This solution was very unsatisfactory, since all C++ exceptions were being converted into a lua_exception, and consequently the structure of the exception was being lost.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-11-27 12:25:29 -08:00

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C++

/*
Copyright (c) 2013 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Leonardo de Moura
*/
#pragma once
#include "util/exception.h"
#include "kernel/justification.h"
namespace lean {
/**
\brief Elaborator and related components store the reason for
failure in justification objects.
*/
class elaborator_exception : public exception {
justification m_justification;
public:
elaborator_exception(justification const & j):m_justification(j) {}
virtual ~elaborator_exception() {}
virtual char const * what() const noexcept { return "elaborator exception"; }
justification const & get_justification() const { return m_justification; }
virtual exception * clone() const { return new elaborator_exception(m_justification); }
virtual void rethrow() const { throw *this; }
};
}