• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (17/17) Apr 13 2013 When immutable constructors are implemented, will there be a difference
• Timon Gehr (4/21) Apr 14 2013 I guess so. But it does not really make sense to declare an immutable
• deadalnix (4/37) Apr 14 2013 I was about to answer exactly the same.

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

When immutable constructors are implemented, will there be a difference 
between the two syntaxes below?

struct MyStruct
{
     int i;

     // ... assume that MyStruct has both
     // mutable and immutable constructors ...
}

     auto s0 = immutable(MyStruct)("some parameter");

     immutable s1 = MyStruct("some parameter");

The former syntax constructs an immutable literal, so the type of s0 is 
deduced to be immutable.

The latter syntax constructs a mutable literal and blits it to the 
immutable s1.

Should the former syntax call the immutable constructor and the latter 
syntax call the mutable constructor?

Ali

Timon Gehr <timon.gehr gmx.ch> writes:

On 04/14/2013 02:48 AM, Ali Çehreli wrote:
 When immutable constructors are implemented, will there be a difference
 between the two syntaxes below?

 struct MyStruct
 {
      int i;

      // ... assume that MyStruct has both
      // mutable and immutable constructors ...
 }

      auto s0 = immutable(MyStruct)("some parameter");

      immutable s1 = MyStruct("some parameter");

 The former syntax constructs an immutable literal, so the type of s0 is
 deduced to be immutable.

 The latter syntax constructs a mutable literal and blits it to the
 immutable s1.

 Should the former syntax call the immutable constructor and the latter
 syntax call the mutable constructor?

 Ali

I guess so. But it does not really make sense to declare an immutable 
constructor if the struct instances implicitly convert between mutable 
and immutable.

"deadalnix" <deadalnix gmail.com> writes:

On Sunday, 14 April 2013 at 08:03:16 UTC, Timon Gehr wrote:
 On 04/14/2013 02:48 AM, Ali Çehreli wrote:
 When immutable constructors are implemented, will there be a 
 difference
 between the two syntaxes below?

 struct MyStruct
 {
     int i;

     // ... assume that MyStruct has both
     // mutable and immutable constructors ...
 }

     auto s0 = immutable(MyStruct)("some parameter");

     immutable s1 = MyStruct("some parameter");

 The former syntax constructs an immutable literal, so the type 
 of s0 is
 deduced to be immutable.

 The latter syntax constructs a mutable literal and blits it to 
 the
 immutable s1.

 Should the former syntax call the immutable constructor and 
 the latter
 syntax call the mutable constructor?

 Ali

 I guess so. But it does not really make sense to declare an 
 immutable constructor if the struct instances implicitly 
 convert between mutable and immutable.

I was about to answer exactly the same.

Note that s1 should fail is immutable => mutable conversion can't 
be done implicitly (if MyStruct contains references).