VHDL Issue Number:      0143
Classification:         Language Enhancement
Language Version:       VHDL-87
Summary:                Allow case-statement 'coverage' checking to be done
                        whenever possible by the analyzer.
Related Issues:         ?
Relevant LRM Sections:  8.8
Key Words and Phrases:  Case-statement
Current Status:         Submitted
1076-1993 Disposition:  Closed (All Issues Completely Addressed)
Disposition Rationale:  Section 8.8 revized to list what kind of expression
                        is allowed. See the 5 bullet items.
Superseded By:          N/A
-----------------------
Date Submitted:         1989/06/21
Author of Submission:   Ken Scott
Author's Affiliation:   Vantage Analysis Systems, Inc.
Author's Post Address:  42840 Christy St., Suite 201
                        Fremont, CA   94538
Author's Phone Number:  (415) 659-0901
Author's Fax Number:    
Author's Net Address:   N/A
-----------------------
Date Analyzed:          TBD   
Author of Analysis:     TBD
Revision Number:        $Revision: 1.7 $
Date Last Revised:      $Date: 1995/05/13 21:53:48 $


Description of Problem
----------------------
   The third paragraph of section 8.7 requires that checking for
   case-statement coverage be done in the following two cases:
      o If the expression is the name of an object whose subtype
        is locally static;
      o If the expression is a qualified expression or type conversion
        whose type mark denotes a locally static subtype.

   Examine the following VHDL:
      p:
      process
          -- Define a function which returns a locally static subtype.
          function F return BIT is
          begin
              return '1';
          end;

      begin
          case F is
             when '0' => -- Do something;
             -- Missing a case for '1'
          end case;
      end process p;
      
   According to a strict reading of the LRM, this VHDL should be
   legal.  Yet it is obvious that the case statement does not have
   choices for each and every possible value that can be returned
   from the function F.  In order to enable this checking you need
   to qualify the function call F with the type BIT:

      case BIT'(F) is ...

   which is ludicrous.

Proposed Resolution
-------------------
   Expand the case-statement checking to cover not only objects but
   any expression which results in a value of a locally static subtype.

VASG-ISAC Analysis & Rationale
------------------------------


VASG-ISAC Recommendation for IEEE Std 1076-1987
-----------------------------------------------


VASG-ISAC Recommendation for Future Revisions
---------------------------------------------