[Issue 15347] New: error message for converting return value with ctor/dtor is horrible

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15347

          Issue ID: 15347
           Summary: error message for converting return value with
                    ctor/dtor is horrible
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: diagnostic
          Severity: major
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: schveiguy at yahoo.com

Simple example:

struct S(T)
{
   T *t;
   immutable(S) foo(T* x) { return S(x);}
}

S!int s;

The error message is as follows:

 Error: cannot implicitly convert expression (S(x)) of type S!int to
immutable(S!int)

Reasonable, straightforward message. But it starts breaking down as we add ctor
and dtor:

struct S(T)
{
   T *t;
   this(T *x) { t = x;}
   immutable(S) foo(T* x) { return S(x);}
}

Error: cannot implicitly convert expression (S(null).this(x)) of type S!int to
immutable(S!int)

Not sure where the S(null).this(x) comes from. Add a dtor and it's even worse:

struct S(T)
{
   T *t;
   this(T *x) { t = x;}
   ~this() {}
   immutable(S) foo(T* x) { return S(x);}
}

Error: cannot implicitly convert expression (( S!int __slS51 = S(null);
 , __slS51).this(x)) of type S!int to immutable(S!int)

That carriage return is actually in the output. I don't even think that's valid
D code (semicolon followed by comma).

All three of these should look like the first one.

Note that just a dtor does not affect the output.

Tested as far back as 2.067.1

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