[m-rev.] for review: check module qualification when testing for type_info

[Tyson Dowd]

On 23-Aug-2001, David Overton <dmo at cs.mu.OZ.AU> wrote:
> Hi,
> 
> This is for Tyson to review.  The new definitions of type_info, etc in
> library/rtti_implementation.m were not compilable in reserved_tag
> grades.  This change fixes that, but I'm not sure if it is the right
> way to do it since I don't know enough about the current designs and
> future plans for RTTI.

I'm not sure what "not compilable" means?  Does it mean the compiler
falls over because it assumes that any type with the name "type_info" is
private_builtin__type_info?  If so isn't this just a plain old bug --
the user is allowed to have a type called type_info.

I don't think I have any plans for rtti_implementation that will require
any more special types to be introduced.  I was just going to implement
a lot of the stuff in the runtime and in std_util.m in Mercury.

> Estimated hours taken: 0.5
> Branches: main
> 
> compiler/type_util.m:
> 	When testing for type_info types, check that the type is either
> 	unqualified or qualified as 'private_builtin'.

The change itself is fine, but some rationale as to why the change has
to be made would be good.

> 
> Index: type_util.m
> ===================================================================
> RCS file: /home/mercury1/repository/mercury/compiler/type_util.m,v
> retrieving revision 1.97
> diff -u -r1.97 type_util.m
> --- type_util.m	27 Jun 2001 05:04:30 -0000	1.97
> +++ type_util.m	22 Aug 2001 06:05:21 -0000
> @@ -994,12 +994,12 @@
>  
>  type_constructors_are_no_tag_type(Ctors, Ctor, ArgType, MaybeArgName) :-
>  	type_is_single_ctor_single_arg(Ctors, Ctor, MaybeSymName, ArgType),
> -	unqualify_name(Ctor, Name),
> -	\+ name_is_type_info(Name),
> +	\+ ctor_is_type_info(Ctor),
>  
>  	% We don't handle unary tuples as no_tag types --
>  	% they are rare enough that it's not worth
>  	% the implementation effort.
> +	unqualify_name(Ctor, Name),
>  	Name \= "{}",
>  
>  	(
> @@ -1013,7 +1013,13 @@
>  
>  type_constructors_are_type_info(Ctors) :-
>  	type_is_single_ctor_single_arg(Ctors, Ctor, _, _),
> -	unqualify_name(Ctor, Name),
> +	ctor_is_type_info(Ctor).
> +
> +:- pred ctor_is_type_info(sym_name).
> +:- mode ctor_is_type_info(in) is semidet.
> +
> +ctor_is_type_info(Ctor) :-
> +	unqualify_private_builtin(Ctor, Name),
>  	name_is_type_info(Name).
>  
>  :- pred name_is_type_info(string).
> @@ -1023,6 +1029,18 @@
>  name_is_type_info("type_ctor_info").
>  name_is_type_info("typeclass_info").
>  name_is_type_info("base_typeclass_info").
> +
> +	% If the sym_name is in the private_builtin module, unqualify it,
> +	% otherwise fail.
> +	% A sym_name is in private_builtin iff it is unqualified or it is
> +	% qualified with the private_builtin module.
> +
> +:- pred unqualify_private_builtin(sym_name, string).
> +:- mode unqualify_private_builtin(in, out) is semidet.
> +
> +unqualify_private_builtin(unqualified(Name), Name).
> +unqualify_private_builtin(qualified(ModuleName, Name), Name) :-
> +	mercury_private_builtin_module(ModuleName).
>  
>  :- pred type_is_single_ctor_single_arg(list(constructor), sym_name, 
>  	maybe(sym_name), type).
> -- 
> David Overton      Department of Computer Science & Software Engineering
> PhD Student        The University of Melbourne, Victoria 3010, Australia
> +61 3 8344 9159    http://www.cs.mu.oz.au/~dmo
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