[Issue 6708] New: immutable ref implicit cast to const ref

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=6708

           Summary: immutable ref implicit cast to const ref
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2011-09-21 13:48:10 PDT ---
I think this is correct code because foo and bar can't change the contents of
arr and x in any way:


void foo(const ref int y) {}
void bar(const ref int[5] a1) {}
void spam(const ref int[] a2) {}
void baz(const ref int[int] aa) {}
void main() {
    immutable int x;
    foo(x); // Error?
    immutable int[5] arr1;
    bar(arr1); // Error?
    immutable int[] arr2;
    spam(arr2); // Error?
    immutable int[int] aa;
    baz(aa); // Error?
}


But DMD 2.055 gives errors:

test.d(7): Error: constant 0 is not an lvalue
test.d(9): Error: cast(const(int[5u]))arr1 is not an lvalue
test.d(11): Error: cast(const(int[]))arr2 is not an lvalue
test.d(13): Error: cast(const(int[int]))aa is not an lvalue


See also a thread on this topic in D.learn:
http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D.learn&article_id=29609

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