cduce issues https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues 2022-02-01T17:00:39+01:00 https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues/26 Weak polymorphism is not unified nor propagated when used in a function 2022-02-01T17:00:39+01:00 Mattias Weak polymorphism is not unified nor propagated when used in a function Some examples here: ```ocaml # let r = ref ([ &#39;a* ]) [];; val r : { get=[ ] -&gt; [ &#39;_weak0* ] set=[ &#39;_weak0* ] -&gt; [ ] } = { get=&lt;fun&gt; # let f (x : Int) : Int = r := [ x ]; x + 1;; val f : Int -&gt; Int = &lt;fun&gt; # r;; - : { get=[ ] -&gt; [ &#39;_... Some examples here: ```ocaml # let r = ref ([ 'a* ]) [];; val r : { get=[ ] -> [ '_weak0* ] set=[ '_weak0* ] -> [ ] } = { get=<fun> # let f (x : Int) : Int = r := [ x ]; x + 1;; val f : Int -> Int = <fun> # r;; - : { get=[ ] -> [ '_weak0* ] set=[ '_weak0* ] -> [ ] } = { get=<fun> set=<fun> } ``` ```ocaml # let g (x : 'a) : 'a = r := [ x ]; x;; val g : 'a -> 'a = <fun> # g 3;; - : 3 = 3 # g;; - : 'a -> 'a = <fun> # r;; - : { get=[ ] -> [ '_weak0* ] set=[ '_weak0* ] -> [ ] } = { get=<fun> set=<fun> } ``` Kim Nguyễn Kim Nguyễn https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues/25 Issue in apply that makes it not monotone 2022-01-30T14:35:33+01:00 Mickael Laurent Issue in apply that makes it not monotone When intersecting an arrow type whose dnf contain several conjunctions, if this intersection makes one of the conjunctions empty, it will not be simplified in the DNF. Then, using the operator apply on this arrow type will consider the ... When intersecting an arrow type whose dnf contain several conjunctions, if this intersection makes one of the conjunctions empty, it will not be simplified in the DNF. Then, using the operator apply on this arrow type will consider the positive part of this empty conjunction and thus it will not yield the expected type but a larger one. This can be reproduced with the following code: ```ocaml module CD = Cduce_types let cup t1 t2 = CD.Types.cup t1 t2 let cap t1 t2 = CD.Types.cap t1 t2 let diff = CD.Types.diff let cons = CD.Types.cons let mk_arrow = CD.Types.arrow let true_typ = CD.Builtin_defs.true_type let false_typ = CD.Builtin_defs.false_type let bool_typ = cup true_typ false_typ let int_typ = CD.Types.Int.any let any = CD.Types.any let empty = CD.Types.empty let any_node = cons any let empty_node = cons empty let subtype = CD.Types.subtype let pp_typ = CD.Types.Print.print_noname let apply t args = let t = CD.Types.Arrow.get t in CD.Types.Arrow.apply t args let arrow_any = CD.Types.Function.any let domain t = if subtype t arrow_any then let t = CD.Types.Arrow.get t in CD.Types.Arrow.domain t else empty let _ = let simple_arrow = mk_arrow (cons int_typ) (cons int_typ) in let test = simple_arrow in let test = cup test (mk_arrow (cons bool_typ) any_node) in let test = diff test (mk_arrow any_node any_node) in let test = cap test (mk_arrow (cons (diff any bool_typ)) any_node) in Format.printf "%a@." pp_typ test ; Format.printf "Subtype of %a ? %b@." pp_typ simple_arrow (subtype test simple_arrow) ; Format.printf "But when we apply an Int to it: %a@." pp_typ (apply test (domain simple_arrow)) ; ``` It has been tested on the branches dune-switch and polymorphic. Kim Nguyễn Kim Nguyễn https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues/18 Unsoundness with testing of function types 2021-05-02T10:25:08+02:00 Tommaso Petrucciani Unsoundness with testing of function types This code (fun ((Int -&gt; Int) -&gt; `true; (Any \ (Int -&gt; Int)) -&gt; `false) | ((Int -&gt; Int) \ (Bool -&gt; Bool)) -&gt; `true | (Int -&gt; Int) &amp; (Bool -&gt; Bool) -&gt; `true | _ -&gt; `false) (fun (x: Int): Int = x + 1) breaks type pre... This code (fun ((Int -> Int) -> `true; (Any \ (Int -> Int)) -> `false) | ((Int -> Int) \ (Bool -> Bool)) -> `true | (Int -> Int) & (Bool -> Bool) -> `true | _ -> `false) (fun (x: Int): Int = x + 1) breaks type preservation (in the cduce-next branch), producing - : `true = false The first function is well-typed; in particular, when the argument has type `Int -> Int`, the result must be `true` since either of the first two branches must apply (together, they cover `Int -> Int` entirely). The application is well-typed as well, but it reduces to the third branch (which is statically predicted to be unused) because the second function can be assigned neither type `(Int -> Int) \ (Bool -> Bool)` nor type `(Int -> Int) & (Bool -> Bool)`. This behaviour actually seems consistent with that described in the formalization (POPL '14 and '15), but it's unsound. When type tests are performed at runtime functions should probably be given negations of arrow types to ensure soundness. I'm not sure how this interacts with polymorphism though. https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues/17 Unsoundness with record typing 2021-05-02T10:41:43+02:00 Tommaso Petrucciani Unsoundness with record typing Functions on records can be given unsound types as in the following: # let f = fun ({..} -&gt; &#39;a) x -&gt; x;; val f : Record -&gt; &#39;a = &lt;fun&gt; # f {};; - : &#39;a = { } It seems that this `&#39;a` cannot be instantiated: # (f {}) + 1;; Characte... Functions on records can be given unsound types as in the following: # let f = fun ({..} -> 'a) x -> x;; val f : Record -> 'a = <fun> # f {};; - : 'a = { } It seems that this `'a` cannot be instantiated: # (f {}) + 1;; Characters 1-5: This expression should have type: !float | { .. } | Int but its inferred type is: 'a which is not a subtype, as shown by the sample: Atom & 'a However, here it becomes unsound: # f (f {});; - : Empty = { } Typing of field removal is also unsound: # let g = fun ({a=Int;b=Bool;..}&'a -> {b=Bool;..}&'a) x -> x\a;; val g : { a=Int b=Bool .. } & 'a -> { b=Bool .. } & 'a = <fun> # g {a=2;b=`true};; - : { a=2 b=`true } = { b=true } # (g {a=2;b=`true}).a;; - : 2 = true # (g {a=2;b=`true}).b;; - : `true = true # (g {a=2;b=`true}).a + 2;; File "runtime/value.ml", line 873, characters 9-15: Assertion failed Kim Nguyễn Kim Nguyễn https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues/13 Tallying: failure in recursive calls inside merge make the whole merge fail 2021-05-02T15:32:53+02:00 Tommaso Petrucciani Tallying: failure in recursive calls inside merge make the whole merge fail Currently `Type_tallying.merge` raises an exception if a constraint set is unsolvable. This exception is handled by `Type_tallying.type_tallying` but not by `merge` itself. Thus, if a recursive call inside `merge` fails, the whole call f... Currently `Type_tallying.merge` raises an exception if a constraint set is unsolvable. This exception is handled by `Type_tallying.type_tallying` but not by `merge` itself. Thus, if a recursive call inside `merge` fails, the whole call fails. In particular, tallying fails on the constraint set ``` 'a <= 'b -> 'c 1 <= 'b 'a -> 'c <= ('f -> 'f) -> 'e ``` (which admits a solution 'a := (1 -> 1), other variables := 1). Test with ``` debug tallying [] ( 'a , ( 1 , ('a -> 'c) ) ) ( ('b -> 'c), ( 'b , (('f -> 'f) -> 1) ) );; ``` (here tallying finds only the solution `'a := Empty` and not the other one). Normalization generates two constraints, one for `'a := Empty`, the other ``` { 'f -> 'f <= 'a <= 'b -> 'c, 1 <= 'b <= Any, Empty <= 'c <= 1 } ``` which is not solved correctly. In `merge`, the contraint `'f -> 'f <= 'b -> 'c` is generated and normalised into ``` { { Empty <= 'b <= 'f, 'f <= 'c <= Any }, { Empty <= 'b <= Empty } } ``` only the first of which is solvable (since `1 <= 'b`, `'b <= Empty` is impossible). The case `'b <= Empty` is considered first and `merge` fails completely instead of considering the other case. Replacing line 605 ``` let m1' = merge delta cache m1 in ``` with ``` let m1' = try merge delta cache m1 with UnSatConstr _ -> ConstrSet.unsat in ``` solves this. I'm not sure if it breaks anything else, but it seems to be what the specification of tallying says (the recursive calls are in union with each other, so empty sets are ignored). Kim Nguyễn Kim Nguyễn https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues/12 Solving type equation with recursive types for a variable &#39;a does not work wh... 2017-10-16T08:48:07+02:00 Kim Nguyễn Solving type equation with recursive types for a variable 'a does not work when 'a occurs below a union/intersection/negation The problem is in decompose and solve_rectype in Types. The Positive module giving the least fix point solution of a system of equation (aka Courcelle) does not work when variable occurs below type connective. See for instance: ``` ... The problem is in decompose and solve_rectype in Types. The Positive module giving the least fix point solution of a system of equation (aka Courcelle) does not work when variable occurs below type connective. See for instance: ``` debug tallying [] [ (Int, 'a),'b ; 'b, 'a ] ;; ``` Kim Nguyễn Kim Nguyễn https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues/10 Loop/errors on tallying 2021-05-02T14:34:55+02:00 Kim Nguyễn Loop/errors on tallying This loops &lt;pre&gt; let x : (Int -&gt; Int) &amp; (&#39;b -&gt; &#39;b) &amp; ((&#39;a -&gt; &#39;a) -&gt; (&#39;a -&gt; &#39;a)) = fun (x : &#39;d ) : (&#39;d) = x : (&#39;d) ;; &lt;/pre&gt; This gives the wrong result &lt;pre&gt; # let x : ((&#39;a -&gt; &#39;a) -&gt; (&#39;a -&gt; &#39;a)) &amp; (Int -&gt; Int) &amp; (&#39;d -&gt; &#39;d) = fun (x : &#39;... This loops <pre> let x : (Int -> Int) & ('b -> 'b) & (('a -> 'a) -> ('a -> 'a)) = fun (x : 'd ) : ('d) = x : ('d) ;; </pre> This gives the wrong result <pre> # let x : (('a -> 'a) -> ('a -> 'a)) & (Int -> Int) & ('d -> 'd) = fun (x : 'd ) : ('d) = x : ('d) ;; This expression should have type: 'd -> 'd but its inferred type is: (('a -> 'a) -> 'a -> 'a) & (Int -> Int) & ('d -> 'd) </pre> while each separate intersection works: <pre> # let x : (('a -> 'a) -> ('a -> 'a)) & (Int -> Int) = fun (x : 'd ) : ('d) = x : ('d) ;; val x : (Int -> Int) & (('a -> 'a) -> 'a -> 'a) = <fun> # let x : ('d -> 'd) = fun (x : 'd ) : ('d) = x : ('d) ;; val x : 'd -> 'd = <fun> </pre> https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues/8 Type error in patricia trees 2021-05-02T14:55:48+02:00 Kim Nguyễn Type error in patricia trees With the current commit 25b127810a48fae75a795ca3bfc9fe7f388a6c11 patricia trees attached (see also [tests/poly/patricia.cd] in the distribution) [merge] function does not type. The error is ``` File &quot;tests/poly/patricia.cd&quot;, line 69, cha... With the current commit 25b127810a48fae75a795ca3bfc9fe7f388a6c11 patricia trees attached (see also [tests/poly/patricia.cd] in the distribution) [merge] function does not type. The error is ``` File "tests/poly/patricia.cd", line 69, characters 31-43: This expression should have type: Empty but its inferred type is: 'a which is not a subtype, as shown by the sample: 'a & Int ``` The line at issue is ``` | (<leaf key=k>x , t) -> insert c k x t ``` And the error message states that at the position of x was wating somethig of an empty type. Let us show why. First notice that ``` insert : ('a -> 'a -> 'a) -> Caml_int -> 'a -> Dict -> Leaf|Branch ``` since we have the following declaration ``` let insert (c: 'a -> 'a -> 'a) (k: Caml_int) (x: 'a) (t: Dict): Leaf|Branch ``` First of all let us replace the line 69 with the following one: ``` | (<leaf key=k>x , t) -> insert ``` we **correctly** obtain the following error: ``` File "tests/poly/patricia.cd", line 69, characters 31-37: This expression should have type: Branch | Leaf but its inferred type is: ('_a_0 -> '_a_0 -> '_a_0) -> Caml_int -> '_a_0 -> [ ] | <brch bit=Caml_int pre=Caml_int>X1 | <leaf key=Caml_int>'_a_0 -> X2 where X1 = [ X2 X2 ] and X2 = <brch bit=Caml_int pre=Caml_int>X1 | <leaf key=Caml_int>'_a_0 which is not a subtype, as shown by the sample: ('_a_0 -> '_a_0 -> '_a_0) -> Caml_int -> '_a_0 -> [ ] | <brch bit=Caml_int pre=Caml_int>X1 | <leaf key=Caml_int>'_a_0 -> X2 where X1 = [ X2 X2 ] and X2 = <brch bit=Caml_int pre=Caml_int>X1 | <leaf key=Caml_int>'_a_0 ``` Notice two things: the system expects as result of the matching something of type ``Leaf|Branch`` (perfect!) and the type deduced for @insert@ is exactly the original type where ``'a`` has been renamed into a fresh variable. If now I use for this line the following definition ``` | (<leaf key=k>x , t) -> insert c ``` I expect that the fresh variable ``'_a_0`` is unified with ``'a`` of the type of ``c``, and thus that this expression has type ``Caml_int -> 'a -> Dict -> Leaf|Branch``. Instead we obtain: ``` File "tests/poly/patricia.cd", line 69, characters 31-39: This expression should have type: Branch | Leaf but its inferred type is: Caml_int -> Arrow which is not a subtype, as shown by the sample: Caml_int -> Arrow ``` So what did happen? Well the fresh variable ``'_a_0`` was **WRONGLY** substituted by Empty instead of by ``'a``. And therefore the deduced type is ``` Caml_int -> Empty -> Dict -> Leaf|Branch ``` (i.e. ``Caml_int -> Arrow``). This explain why feeding two more arguments to it we obtain the error message that the function was expecting something of type Empty. Indeed with ``` | (<leaf key=k>x , t) -> insert c k x ``` we obtain ``` File "tests/poly/patricia.cd", line 69, characters 31-43: This expression should have type: Empty but its inferred type is: 'a which is not a subtype, as shown by the sample: 'a & Int ``` Kim Nguyễn Kim Nguyễn https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues/7 Typechecking should only use squaresubtype when checking a result type agains... 2021-05-02T14:53:42+02:00 Kim Nguyễn Typechecking should only use squaresubtype when checking a result type against an expected constraint The typechecking function as the following signature: ``` type_check loc env constr e ``` where ``loc`` is a location, env is the environment, ``constr`` is an expected type and ``e`` is the expression to type-check. It returns an expres... The typechecking function as the following signature: ``` type_check loc env constr e ``` where ``loc`` is a location, env is the environment, ``constr`` is an expected type and ``e`` is the expression to type-check. It returns an expression ``e'`` (where some expressions may have been modified, e.g. branch of patterns specialized, unneeded cast removed etc.) and an output type ``t``. The last thing it often does before returning is: ``` verify loc t constr ``` which checks that indeed, ``t`` is a subtype of the expected constraint ``constr`` (for instance, when typing the body of a function, the constraint is the expected result type of the function). ``verify`` uses plain subtyping which is wrong. It should: use ``squaresubtype_delta`` to check if there exists substitutions s1,...,sn such that t < constr return not, t but t{s1} & ... & t{sn} Note that because typechecking is half half between the old monomorphic code and the new polymorphic code (buggy) we end up with either weird type error or even unsound and clearly ill-typed code that compiles: ``` let f (<bar>['a] -> <foo>['a]) <bar>[ x ] -> <foo>[x] ;; let f (<bar>['a] -> <foo>['a]) <bar>[ y ] -> <foo>[ y] in let apply (x : 'b) : 'b = f x ;; ``` the body of apply is clearly wrong yet it compiles with the current master. We need to thoroughly review the code of ``type_check`` (and other functions) to check for the following: + check everywhere there is an instance of ``Types.subtype`` to see whether ``Types.squaresubtype`` should be used instead. + properly review how the generalisation/freshening of type variables is done Kim Nguyễn Kim Nguyễn https://gitlab.math.univ-paris-diderot.fr/cduce/cduce/-/issues/3 Fix pretty printing of parentheses in types 2021-05-02T14:51:06+02:00 Kim Nguyễn Fix pretty printing of parentheses in types Some types generate superfluous parentheses: ``` #print_type (&#39;a | &#39;b ) \&#39;c;; ((&#39;a | &#39;b) \ (&#39;c)) ``` And some others are missing parenthses: ``` #print_type (Int -&gt; Int) &amp; (Bool -&gt; Bool);; Bool -&gt; Bool &amp; Int -&gt; Int # #print_type Bool -... Some types generate superfluous parentheses: ``` #print_type ('a | 'b ) \'c;; (('a | 'b) \ ('c)) ``` And some others are missing parenthses: ``` #print_type (Int -> Int) & (Bool -> Bool);; Bool -> Bool & Int -> Int # #print_type Bool -> Bool & Int -> Int;; Bool -> Arrow ``` here we cannot paste the output of the toplevel. Kim Nguyễn Kim Nguyễn