digitalmars.D.bugs - [Issue 603] New: Undocumented behaviour: case and default create a scope
- d-bugmail puremagic.com (43/43) Nov 26 2006 http://d.puremagic.com/issues/show_bug.cgi?id=603
- d-bugmail puremagic.com (11/11) Dec 15 2006 http://d.puremagic.com/issues/show_bug.cgi?id=603
- Stewart Gordon (10/14) Dec 15 2006 d.puremagic.com seems to be down at the moment - so I wonder if this'll
- d-bugmail puremagic.com (14/14) Dec 16 2006 http://d.puremagic.com/issues/show_bug.cgi?id=603
- d-bugmail puremagic.com (5/5) Jan 07 2007 http://d.puremagic.com/issues/show_bug.cgi?id=603
- d-bugmail puremagic.com (7/7) Jan 07 2007 http://d.puremagic.com/issues/show_bug.cgi?id=603
- d-bugmail puremagic.com (8/10) Jan 27 2007 http://d.puremagic.com/issues/show_bug.cgi?id=603
- d-bugmail puremagic.com (9/9) Jun 20 2008 http://d.puremagic.com/issues/show_bug.cgi?id=603
- d-bugmail puremagic.com (57/57) Jul 07 2009 http://d.puremagic.com/issues/show_bug.cgi?id=603
- d-bugmail puremagic.com (10/10) Jul 08 2009 http://d.puremagic.com/issues/show_bug.cgi?id=603
- d-bugmail puremagic.com (11/11) Nov 08 2010 http://d.puremagic.com/issues/show_bug.cgi?id=603
- d-bugmail puremagic.com (11/11) Nov 08 2010 http://d.puremagic.com/issues/show_bug.cgi?id=603
- d-bugmail puremagic.com (12/12) Nov 08 2010 http://d.puremagic.com/issues/show_bug.cgi?id=603
http://d.puremagic.com/issues/show_bug.cgi?id=603 Summary: Undocumented behaviour: case and default create a scope Product: D Version: 0.175 Platform: PC URL: http://www.digitalmars.com/d/statement.html#SwitchStatem ent OS/Version: Windows Status: NEW Keywords: rejects-valid, spec Severity: normal Priority: P2 Component: DMD AssignedTo: bugzilla digitalmars.com ReportedBy: smjg iname.com I've noticed an interesting behaviour: the code between two consecutive case or default labels creates a scope. ---------- import std.stdio; void main() { int qwert; switch (qwert) { case 42: int yuiop; int asdfg; default: int hjkl = 98; writefln(yuiop); writefln(asdfg); writefln(hjkl); } } ---------- D:\My Documents\Programming\D\Tests\label_scope_2.d(12): Error: undefined identifier yuiop D:\My Documents\Programming\D\Tests\label_scope_2.d(13): Error: undefined identifier asdfg ---------- While this is intuitively sensible (it enables cases to define their own variables independently of each other), it doesn't follow from the logical code structure (in which all cases are at one level immediately below the SwitchStatement) or from anything on the relevant page of the spec. --
Nov 26 2006
http://d.puremagic.com/issues/show_bug.cgi?id=603 bugzilla digitalmars.com changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |INVALID What happens is the { } after the switch creates a new scope. The case and default statements are just labels. I believe the grammar implies this behavior, and no changes are necessary. --
Dec 15 2006
d-bugmail puremagic.com wrote:What happens is the { } after the switch creates a new scope. The case and default statements are just labels. I believe the grammar implies this behavior, and no changes are necessary.d.puremagic.com seems to be down at the moment - so I wonder if this'll make it there.... Your marking this INVALID is nonsense. A bug is a bug, whether it's the spec or the compiler that's doing what you intended. If the case and default statements weren't themselves creating scopes, then there would be no "undefined identifier" errors. If the errors aren't coming up when you try my testcase, then DMD has an OS-version-dependent bug. Stewart.
Dec 15 2006
http://d.puremagic.com/issues/show_bug.cgi?id=603 smjg iname.com changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |REOPENED Resolution|INVALID | (Originally posted to digitalmars.D.bugs) A bug is a bug, whether it's the spec or the compiler that's doing what you intended. If the case and default statements weren't themselves creating scopes, then there would be no "undefined identifier" errors. If the errors aren't coming up when you try my testcase, then DMD has an OS-version-dependent bug. --
Dec 16 2006
http://d.puremagic.com/issues/show_bug.cgi?id=603 We can say that switch do implicit goto, but spec say that useing goto for skiping initialisation is an error. --
Jan 07 2007
http://d.puremagic.com/issues/show_bug.cgi?id=603 See issue 602. Moreover, it isn't clear whether a goto should be allowed to skip a declaration with no explicit initializer. While you could question the validity of the code on this basis, you can't sensibly claim this as the reason for the particular error message reported. --
Jan 07 2007
http://d.puremagic.com/issues/show_bug.cgi?id=603We can say that switch do implicit goto, but spec say that useing goto for skiping initialisation is an error.With that premise, the code would be invalid even if the default section doesn't touch yuiop or asdfg. It's still skipping initialisation even if what hasn't been initialised is never used. The variables are nonetheless in scope, if you believe the spec rather than the compiler. --
Jan 27 2007
http://d.puremagic.com/issues/show_bug.cgi?id=603 kamm-removethis incasoftware.de changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |kamm- | |removethis incasoftware.de ------- *** Bug 2155 has been marked as a duplicate of this bug. *** --
Jun 20 2008
http://d.puremagic.com/issues/show_bug.cgi?id=603 2009-07-07 11:50:12 PDT --- The fact that default and case statements create a new scope is evident in the frontend code: statements = new Statements(); while (token.value != TOKcase && token.value != TOKdefault && token.value != TOKrcurly) { statements->push(parseStatement(PSsemi | PScurlyscope)); } s = new CompoundStatement(loc, statements); s = new ScopeStatement(loc, s); With this in mind, it would make sense to add this to the section on switch statements: Case and default statements create a new scope that contains all statements up until the next case or default statement with the same parent, or the end of the enclosing scope. Example: switch(i) { case 1: ... case 2: if (i) { case 3: ... case 4: ... } case 5: } is equivalent to switch(i) { case 1: { ... } case 2: { if (i) { case 3: { ... } case 4: { ... } } } case 5: } I'm not marking this as 'patch' because I'm not happy with 'with the same parent'. Suggestions? Also, can someone suggest a grammar change that would explain this behavior? Replacing case ExpressionList : Statement with case ExpressionList : ScopeStatement isn't right as ScopeStatement is either BlockStatement or NonEmptyStatement. I think we need a new ScopeCaseStatement here. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jul 07 2009
http://d.puremagic.com/issues/show_bug.cgi?id=603 Sobirari Muhomori <maxmo pochta.ru> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords|rejects-valid |diagnostic PDT --- Scoped case is a step towards switch redesign :) +1. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jul 08 2009
http://d.puremagic.com/issues/show_bug.cgi?id=603 Walter Bright <bugzilla digitalmars.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|REOPENED |RESOLVED Resolution| |FIXED 00:00:23 PST --- http://www.dsource.org/projects/phobos/changeset/2129 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Nov 08 2010
http://d.puremagic.com/issues/show_bug.cgi?id=603 Walter Bright <bugzilla digitalmars.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |REOPENED Resolution|FIXED | 00:08:08 PST --- Ahh, I'm confused. Wrong fix. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Nov 08 2010
http://d.puremagic.com/issues/show_bug.cgi?id=603 Walter Bright <bugzilla digitalmars.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|REOPENED |RESOLVED Resolution| |FIXED 00:35:29 PST --- http://www.dsource.org/projects/phobos/changeset/2130 This should do it. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Nov 08 2010