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Report From: Delphi-BCB/Compiler/Delphi/Errors - Warnings [ Add a report in this area ]

Report #: 8770

Status: Open

Warning for duplicate identifiers in with-scope

Project: Delphi

Build #: 7.0.4.453

Version: 7.0

Submitted By: Hallvard Vassbotn

Report Type: Suggestion / Enhancement Request

Date Reported: 8/10/2004 6:01:35 AM

Severity: Commonly encountered problem

Last Updated: 1/9/2007 10:42:57 AM

Platform: 95, 98, 2000, NT, XP

Internal Tracking #:

Resolution: Duplicate

Resolved in Build: : None

Duplicate of: 2667

Voting and Rating

Overall Rating: (4 Total Ratings)

4.75 out of 5

Total Votes: 3

Description

There should be a new Warning for potential name conflicts when the same identifier is defined in a with-scope and a non-with scope.

Again (as in QC #8761), the goal is to catch unintended changes in semantics after changes have been made to used units - but this time specifically for cases where the with-statment changes the scoping rules and introduces potential name conflicts.

IMO, if we could have this kind of warning for with statements, it would be the first steps towards patching one of the very few sorespots of the language.

Steps to Reproduce:

With-statements are tricker to design good warnings for. I think the rule-of-thumb should be that it doesn't warn on local identfiers defined in the same unit. Trust the programmer have control over the identifiers and name space-pollution caused by himself in the current unit. Local changes that have local effect isn't that harmful.

Once there is a name-clash between a local identifier and an identifier in the with-scope, generate a warning. This will catch future changes in external units that cause semantic changes.

For instance:

Unit Foo;
type
   TGadget = class
     bar: integer;
   end
...
Unit Bar;
var
   a  : TGadget;
   foo: integer
begin
   with a do
     foo := 123;
end;

This is version 1. Code compiles without warnings and works correctly. Now Mr. Component on the other side of the globe makes an update to the TGadget class:

Unit Foo;
type
   TGadget = class
     foo: integer; // New feature!
     bar: integer;
   end

Now Joe Doe recompiles his code with this new version:

Unit Bar;
var
   a  : TGadget;
   foo: integer
begin
   with a do
     foo := 123;
end;

With D7, there is no warning. Code compiles, but fails at run-time. In a future version of the compiler he would get warning such as:

Warning: Potential name conflict: foo declared in unit Bar and Foo.TGadget.

In this case, to get rid of the warning, the programmer could change the code to

Bar.foo := 123;

or he could get rid of the with-statement.

Workarounds

None

Attachment

None

Comments

Kristofer Skaug at 8/25/2004 4:51:11 AM -

Also related to #1615, although perhaps not 100% duplicate.

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