Bug 6707 – Error message for mismatch of const/non-const property functions needs to improve

struct Foo { int payload; @property void value(int x) { payload = x;} @property int value() { return payload; } const bool opEquals(ref const(Foo) other) { return this.value == other.value; } } void main() { } This errors with: Error: function test.Foo.value (int x) is not callable using argument types () The solution is to add a const property function like this one: @property const(int) value() const { return payload; } But this can't be easily figured out from that error message.

Better test case: struct Foo { @property bool value() { return true; } void test() const { auto x = value; // not callable using argument types () auto y = value(); // not callable using argument types () const } } void main() { } It seems 'this' for property func isn't printed out properly unless it's called as a function, I'll see if this is fixable.

Commits pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/d123b58057a8116d3549418551ed7ea03f9c46cd Fixes Issue 6707 https://github.com/D-Programming-Language/dmd/commit/b022c3c66616600cdf349d53d32983774b72fdbd Merge pull request #1164 from AndrejMitrovic/Fix6707 Fix Issue 6707 - Print better error message on const property mismatch

*** Issue 8549 has been marked as a duplicate of this issue. ***

I reopen this as enhancement request because I think the error message is not good enough still. See Issue 8549 for more info. This program: struct Foo { int[] opSlice() { return [0]; } } struct Bar { Foo spam; const(Foo) bar() const { return spam; } } void main() { Bar().bar()[]; } Currently gives: test.d(11): Error: function test.Foo.opSlice () is not callable using argument types () const In Issue 8549 Andrej Mitrovic suggests an error message similar to: Error: function test.Foo.opSlice () is not callable using const(this) But I think a better error message, more newbie-friendly, tells the programmer how to fix the problem, (not complete error message): test.d(11): Error: function test.Foo.opSlice() needs to be const to [...]

(In reply to comment #4) > But I think a better error message, more newbie-friendly, tells the programmer > how to fix the problem, (not complete error message): > > test.d(11): Error: function test.Foo.opSlice() needs to be const to [...] If it's in a 3rd party library then the user has no other choice but to use a const object. I don't think we should start recommending to rewrite code like that, especially to newbies.

(In reply to comment #5) > If it's in a 3rd party library then the user has no other choice but to use a > const object. I don't think we should start recommending to rewrite code like > that, especially to newbies. I understand. Time ago I have seen this error message and it took me some some to understand what's the problem. So I've asked for a simpler to understand error message. If you think my suggestion is not good, then do something different :-) Maybe we should ask to more people in the D newsgroup.

*** Issue 9132 has been marked as a duplicate of this issue. ***

The pull for Issue 1730 will likely resolve your issue of the unreadable error message. *** This issue has been marked as a duplicate of issue 1730 ***

*** Issue 8552 has been marked as a duplicate of this issue. ***