!ASIS Issue #061
!topic Asis and statements'labels
!from  Alain Le Guennec
!keywords label
!discussion

In the current ASIS draft, there is no way to query the _whole_ label
attached to a statement, only label names through the query
Asis.Statements.Label_Names.

Now consider the two following (a bit pathological) examples :

procedure Sample1 is
begin
   << --  << inside comment :-)
   label_name >> null;
end Sample1;

procedure Sample2 is
begin
   loop_name  --  : inside comment :-)
 :
    loop
       null;
    end loop loop_name;
end Sample2;

Now if one wants (for example in a style-checker application) to get
the _whole_ image corresponding to a label, there is no other way than
getting the image of the whole statement, then manually parse to
extract the relevant part.

The Element_Image returned for A_Defining_Identifier corresponding to
a label will only give the label_name, not the full text between '<<'
and '>>' (or not until the ':' for loops and blocks identifier.)

After reading the relevant part of the RM, I definitely think that
labels (for gotos, loops and blocks) are an independant 'syntaxic
construct' which has no counter-part in Asis.

I think there is simply a missing Asis.Element_Kind : A_Label which
could then be further qualified as Label_Kinds :

 - Not_A_Label
 - A_Statement_Label
 - A_Loop_Identifier_Label
 - A_Block_Identifier_Label

(the fact that a statement label and a loop identifier can not have
the same name in a given sub-program clearly suggests that they are of
the same kind: A_Label.)

With this new category, there wouldn't be any more ambiguities about
what to return as an Element_Image. And there would be one more
structural query to return the label name of A_Label element.
Asis.Statements.Label_Names would have to be renamed
Asis.Statements.Labels which should return a list of A_Label elements
instead of a list of A_Defining_Identifier elements.

!resolution  Accepted, with Modifications.
!date 97-03-26
!Notes

See resolution of Issue #060, which also resolves this issue.

Changes made in ASIS version 2.0.M.