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digitalmars.D.bugs - [Issue 16221] New: Better compiler error message for disabled


          Issue ID: 16221
           Summary: Better compiler error message for  disabled function
           Product: D
           Version: D2
          Hardware: x86_64
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: acehreli yahoo.com

(This may be related to bug 11747.)

The following code would fail compilation anyway because const(B)'s A member
has a  disabled opEquals:

struct A {
     disable bool opEquals(A);

void main() {
    auto a = const(A)();
    if (a == a) {}

However, although technically correct, the error message is about function
being non-const:

  Error: mutable method deneme.A.opEquals is not callable using a const object

The message is misleading because it sounds as if making it const would work.
Let's try it:

     disable bool opEquals(A) const;    // <-- now const

Ok, only now the error is clear:

  Error: function deneme.A.opEquals is not callable because it is annotated
with  disable

I'm creating this bug because it was relatively harder to determine what was
wrong in a more complex piece of code where A was a member of another object.


Jun 30 2016