After this commit, in the type checker, when checking convertability, we first compute a normal form without expanding opaque terms.
If the terms are convertible, then we are done, and saved a lot of time by not expanding unnecessary definitions.
If they are not, instead of throwing an error, we try again expanding the opaque terms.
This seems to be the best of both worlds.
The opaque flag is a hint for the type checker, but it would never prevent us from type checking a valid term.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
The elaborator produces better proof terms. This is particularly important when we have to prove the remaining holes using tactics.
For example, in one of the tests, the elaborator was producing the sub-expression
(λ x : N, if ((λ x::1 : N, if (P a x x::1) ⊥ ⊤) == (λ x : N, ⊤)) ⊥ ⊤)
After, this commit it produces
(λ x : N, ¬ ∀ x::1 : N, ¬ P a x x::1)
The expressions above are definitionally equal, but the second is easier to work with.
Question: do we really need hidden definitions?
Perhaps, we can use only the opaque flag.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
The elaborator was failing in the following scenario:
- Failing constraint of the form
ctx |- ?m1 =:= ?m2
where
?m2 is assigned to ?m1,
and ?m1 is unassigned.
has_metavar(?m2, ?m1) returns true, and a cycle is incorrectly reported.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
The elaborator was missing solutions because of the missing condition at is_simple_ho_match.
This commit also adds a new test that exposes the problem.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
This commits also adds a new unit test that demonstrates non-termination due to this kind of constraint.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
The "quota" hack used before this commit was inefficient, and too hackish.
This commit uses two lists of constraints: active and delayed.
The delayed constraints are only processed when there are no active constraints.
We use a simple index to quickly find which delayed constraints have assigned metavariables.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
checkpoint
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
The idea is to catch the inconsistency in constraints such as:
ctx |- ?m[inst:0 v] == fun x, ?m a x
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
The modifications started at commit 1852c86948 made a big difference. For example, before these changes test tests/lean/implicit7.lean generated complicated constraints such as:
[x : Type; a : ?M::29[inst:1 ?M::0[lift:0:1]] x] ⊢ Pi B : Type, (Pi _ : x, (Pi _ : (?M::35[inst:0 #0, inst:1 #2, inst:2 #4, inst:3 #6, inst:5 #5, inst:6 #7, inst:7 #9, inst:9 #9, inst:10 #11, inst:13 ?M::0[lift:0:13]] x a B _), (?M::36[inst:1 #1, inst:2 #3, inst:3 #5, inst:4 #7, inst:6 #6, inst:7 #8, inst:8 #10, inst:10 #10, inst:11 #12, inst:14 ?M::0[lift:0:14]] x a B _ _))) ≈
?M::22 x a
After the changes, only very simple constraints are generated. The most complicated one is:
[] ⊢ Pi a : ?M::0, (Pi B : Type, (Pi _ : ?M::0, (Pi _ : B, ?M::0))) ≈ Pi x : ?M::17, ?M::18
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
This commit also simplifies the method check_pi in the type_checker and type_inferer.
It also fixes process_meta_app in the elaborator.
The problem was in the method process_meta_app and process_meta_inst.
They were processing convertability constrains as equality constraints.
For example, process_meta_app would handle
ctx |- Type << ?f b
as
ctx |- Type =:= ?f b
This is not correct because a ?f that returns (Type U) for b satisfies the first but not the second.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
This modification was motivated by a bug exposed by tst17 at tests/kernel/type_checker.
metavar_env is now a smart point to metavar_env_cell.
ro_metavar_env is a read-only smart pointer. It is useful to make sure we are using proof_state correctly.
example showing that the approach for caching metavar_env is broken in the type_checker
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
The environment object is a "smart-pointer".
Before this commit, the use of "const &" for environment objects was broken.
For example, suppose we have a function f that should not modify the input environment.
Before this commit, its signature would be
void f(environment const & env)
This is broken, f's implementation can easilty convert it to a read-write pointer by using
the copy constructor.
environment rw_env(env);
Now, f can use rw_env to update env.
To fix this issue, we now have ro_environment. It is a shared *const* pointer.
We can convert an environment into a ro_environment, but not the other way around.
ro_environment can also be seen as a form of documentation.
For example, now it is clear that type_inferer is not updating the environment, since its constructor takes a ro_environment.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Lean was spending 17% on the runtime "throwing exceptions" in the test tests/lean/implicit7.lean
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Synthesizer is not part of the elaborator anymore.
The elaborator fills the "easy" holes.
The remaining holes are filled using different techniques (e.g., tactic framework) that are independent of the elaborator.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
After this commit, a value of type 'expr' cannot be a reference to nullptr.
This commit also fixes several bugs due to the use of 'null' expressions.
TODO: do the same for kernel objects, sexprs, etc.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
This commit improves the condition for showing that an equality(and convertability) constraint cannot be solved. A nice consequence is that Lean produces nicer error messages. For example, the error message for unit test elab1.lean is more informative.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Before this commit, the elaborator would only assign ?M <- P, if P was normalized. This is bad since normalization may "destroy" the structure of P.
For example, consider the constraint
[a : Bool; b : Bool; c : Bool] ⊢ ?M::1 ≺ implies a (implies b (and a b))
Before this, ?M::1 will not be assigned to the "implies-term" because the "implies-term" is not normalized yet.
So, the elaborator would continue to process the constraint, and convert it into:
[a : Bool; b : Bool; c : Bool] ⊢ ?M::1 ≺ if Bool a (if Bool b (if Bool (if Bool a (if Bool b false true) true) false true) true) true
Now, ?M::1 is assigned to the term
if Bool a (if Bool b (if Bool (if Bool a (if Bool b false true) true) false true) true) true
This is bad, since the original structure was lost.
This commit also contains an example that only works after the commit is applied.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
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>
Instead of having m_interrupted flags in several components. We use a thread_local global variable.
The new approach is much simpler to get right since there is no risk of "forgetting" to propagate
the set_interrupt method to sub-components.
The plan is to support set_interrupt methods and m_interrupted flags only in tactic objects.
We need to support them in tactics and tacticals because we want to implement combinators/tacticals such as (try_for T M) that fails if tactic T does not finish in M ms.
For example, consider the tactic:
try-for (T1 ORELSE T2) 5
It tries the tactic (T1 ORELSE T2) for 5ms.
Thus, if T1 does not finish after 5ms an interrupt request is sent, and T1 is interrupted.
Now, if you do not have a m_interrupted flag marking each tactic, the ORELSE combinator will try T2.
The set_interrupt method for ORELSE tactical should turn on the m_interrupted flag.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
It is incorrect to apply substitutions during normalization.
The problem is that we do not have support for tracking justifications in the normalizer. So, substitutions were being silently applied during normalization. Thus, the correctness of the conflict resolution in the elaboration was being affected.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
