Refuse int indexing of associative arrays with char keys

[dlangBugzillaToGithub]

bearophile_hugs reported this on 2013-12-12T10:11:20Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=11733

CC List

• yebblies

Description

I think this code should be disallowed:


void main() {
    int[char] aa1;
    int[dchar] aa2;
    auto r1 = aa1[0];
    auto r2 = aa2[0];
}


dmd 2.065alpha compiles it with no errors, and gives at run-time:

core.exception.RangeError@temp(4): Range violation

[dlangBugzillaToGithub]

yebblies commented on 2013-12-12T23:01:55Z

Why?  0 implicitly converts to both char and dchar.

[dlangBugzillaToGithub]

bearophile_hugs commented on 2013-12-13T04:46:25Z

This is not as important as other changes I have proposed elsewhere.


(In reply to comment #1)
> Why?  0 implicitly converts to both char and dchar.

Because int and char are two different types. It makes code less clear, and in D there is a simple syntax to express that:

auto r1 = aa1['\0'];
auto r2 = aa2['\0'];

There is no ambiguity here, '\0' is clearly a char for the person that reads the code. Using 0 instead of '\0' seems a weakly typing archaism coming from C.

[dlangBugzillaToGithub]

yebblies commented on 2013-12-13T06:19:24Z

There is no ambiguity anyway.  Asking for int not to convert to char is not new, and I vaguely recall it was rejected on the grounds that char x = 'a'+7; should work.  I don't if there is an existing report for that.