[Issue 3534] New: const data can be modified by passing through ref function parameter

[d-bugmail]

http://d.puremagic.com/issues/show_bug.cgi?id=3534

           Summary: const data can be modified by passing through ref
                    function parameter
           Product: D
           Version: 2.036
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Keywords: accepts-invalid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nob...@puremagic.com
        ReportedBy: s...@iname.com
            Blocks: 2573


--- Comment #0 from Stewart Gordon <s...@iname.com> 2009-11-20 10:58:34 PST ---
Based on a newsgroup post by Tomek Sowi�ski.  Both these testcases compile
without error:

----------
import std.stdio;

const int a;

void foo(ref int i) {
    i = 4;
}

void foo() {
    foo(a);
}

void main() {
    writefln("%d", a);
    foo();
    writefln("%d", a);
}
----------
The bug disappears if a is explicitly initialised.

----------
import std.stdio;

const int value;

void changeConst() {
    doChange(value);
}

void doChange(ref int var) {
    var = 42;
}

void main() {
    writefln("%d", value);
    changeConst();
    writefln("%d", value);
}
----------
The bug disappears if a is explicitly initialised.

----------
import std.stdio;

class Class {
    int value;

    void changeConst() const {
        doChange(value);
    }

    void doChange(ref int var) const {
        var = 42;
    }
}

void main() {
    Class obj = new Class;
    writefln("%d", obj.value);
    obj.changeConst();
    writefln("%d", obj.value);
}

----------
The bug also bits if doChange is made static or global and the const attribute
removed.  If only the const attribute is removed, the error is correctly
diagnosed (though this may be partly due to another bug).

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