digitalmars.D.bugs - [Issue 3746] New: Misleding error message "OP has no effect in expression XXX), in void function
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http://d.puremagic.com/issues/show_bug.cgi?id=3746
Summary: Misleding error message "OP has no effect in
expression XXX), in void function
Product: D
Version: 2.041
Platform: Other
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P2
Component: DMD
AssignedTo: nobody puremagic.com
ReportedBy: baryluk smp.if.uj.edu.pl
17:15:05 PST ---
On function with void return type, if one will put expression after return:
void f() {
auto a = 1, b = 3, c = 5;
return a/b*c;
}
will end with compiler error like:
aaa.d(4): Error: * has no effect in expression (a / b * c)
My function "f" was lot bigger, and took me about 5 minutes to understand what
is wrong.
Could such bugs can be detected and be something like
aaa.d(4): Error: no return statment allowed in void function/method
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Jan 27 2010
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Witold Baryluk <baryluk smp.if.uj.edu.pl> changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |minor
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Jan 27 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3746
Bernard Helyer <blood.of.life gmail.com> changed:
What |Removed |Added
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CC| |blood.of.life gmail.com
19:59:24 PST ---
Well, obviously return *is* allowed from void functions (void f() { return; }).
But 'error: return statement with a value in a void function' would be a
preferable message than talking about values having no effect in expressions.
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Jan 27 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3746
12:12:00 PST ---
Well, obviously return *is* allowed from void functions (void f() { return; }).
But 'error: return statement with a value in a void function' would be a
preferable message than talking about values having no effect in expressions.
Yes you are right. Error messages should be as precise as possible.
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Jan 28 2010
http://d.puremagic.com/issues/show_bug.cgi?id=3746
yebblies <yebblies gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |sky q1cc.net
*** Issue 3855 has been marked as a duplicate of this issue. ***
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Jun 12 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3746
yebblies <yebblies gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |yebblies gmail.com
Resolution| |DUPLICATE
*** This issue has been marked as a duplicate of issue 3630 ***
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Jun 12 2011
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yebblies <yebblies gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|DUPLICATE |
Severity|minor |enhancement
My bad, this is a request for a better error.
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Jun 12 2011
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bearophile_hugs eml.cc changed:
What |Removed |Added
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CC| |bearophile_hugs eml.cc
*** Issue 3922 has been marked as a duplicate of this issue. ***
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Jun 13 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3746 Issue 3922 contains some interesting comments. It seems this enhancement request for a better error message has many dupes! -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jun 13 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3746
yebblies <yebblies gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |patch
Summary|Misleding error message "OP |Misleading error message
| has no effect in |"OP has no effect in
|expression XXX), in void |expression XXX), in void
|function |function
https://github.com/D-Programming-Language/dmd/pull/121
This adds the error message:
testx.d(4): Error: expression with no side effects used with void return
Good enough?
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Jun 13 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3746https://github.com/D-Programming-Language/dmd/pull/121 This adds the error message: testx.d(4): Error: expression with no side effects used with void return Good enough?I don't understand. Elsewhere I have a bug report that asks for a new error message if you don't use the result of a pure function. But this bug report just asks for a better error message in the situation of using "return x;" in a void function. So I expected an error message like: foo.d(20): Error: a void function can't return 'int'. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jun 13 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3746I don't understand. Elsewhere I have a bug report that asks for a new error message if you don't use the result of a pure function. But this bug report just asks for a better error message in the situation of using "return x;" in a void function. So I expected an error message like: foo.d(20): Error: a void function can't return 'int'.Returning an int expression from a void function is perfectly legal, so long as the expression has side effects. This is explicitly allowed by the spec. http://www.digitalmars.com/d/2.0/statement.html#ReturnStatement You're talking about two completely separate issues, both of which are enhancements. This issue is about providing a clearer error message without changing the spec. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jun 13 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3746You're talking about two completely separate issues, both of which are enhancements. This issue is about providing a clearer error message without changing the spec.Walter has accepted one of the enhancement requests I was talking about (the one about pure functions). I was not aware the second too is an enhancement request, but after re-reading that part of the D specs I see you are right. So technically your error message is correct. But it's hard to keep in memory all the D specs, especially for D newbies. So I suggest a longer and more wordy error message, because this error message is not easy enough to understand. ---------- According to the D specs this code is illegal, is your patch raising an error on it? pure int sqr(int x) { return x * x; } void main() { return sqr(10); } ---------- According to the current D specs this code is correct: int sqr(int x) { return x * x; } void main() { return sqr(10); } But I can't see this as correct, it's bug prone. So bug 3922 was not a dupe, it was an ehancement request! I have to reopen it. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jun 14 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3746
Don <clugdbug yahoo.com.au> changed:
What |Removed |Added
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CC| |clugdbug yahoo.com.au
I don't understand. Elsewhere I have a bug report that asks for a new error
message if you don't use the result of a pure function.
But this bug report just asks for a better error message in the situation of
using "return x;" in a void function. So I expected an error message like:
foo.d(20): Error: a void function can't return 'int'.
Returning an int expression from a void function is perfectly legal, so long as
the expression has side effects. This is explicitly allowed by the spec.
http://www.digitalmars.com/d/2.0/statement.html#ReturnStatement
Yes, but it was agreed on the newsgroup that this is a misfeature. (Andrei was
horrified about it). It should be disallowed.
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Jun 14 2011
http://d.puremagic.com/issues/show_bug.cgi?id=3746
Without this feature, what should happen with lazy void?
void lf(lazy void a) { a; }
void main()
{
int i;
lf(i++);
}
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Jun 14 2011
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yebblies <yebblies gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |RESOLVED
Resolution| |FIXED
This bug has been fixed with issue 5399.
https://github.com/D-Programming-Language/dmd/commit/c942d51c8b1103d5ce4c3dfc03ae77c07c687cd6
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Oct 09 2011