Re: dmd 2.093.1: duplicate method definitions ignored altogether

[Jacob Carlborg via Digitalmars-d-learn]

On 2021-01-05 03:02, kdevel wrote:

expected output: none. The compiler should have rejected the code after 
the duplicate definition def #2. dmd 2.093.1 ignores both definitions 
instead. Is this a bug or a bug?


DMD 2.095.0 now reports an error for this.

--
/Jacob Carlborg

Re: dmd 2.093.1: duplicate method definitions ignored altogether

[kdevel via Digitalmars-d-learn]

On Tuesday, 5 January 2021 at 03:36:47 UTC, Paul Backus wrote:

On Tuesday, 5 January 2021 at 02:02:39 UTC, kdevel wrote:


[...]

If you try to call .toString directly on a const(S), you get 
the following error:


onlineapp.d(27): Error: onlineapp.S.toString called with 
argument types () const matches both:

onlineapp.d(9): onlineapp.S.toString() const
and:
onlineapp.d(13): onlineapp.S.toString() const


Sure, but that's too late. IMHO the compiler should detect 
duplicate
definitions (probably concealing a program error) regardless 
whether
the method is called. There is a difference between calls which 
match

two or more functions and duplicate definitions. Isn't it?

Other compilers for other languages complain loud and clear:

```ddcpp.cc
template
struct X {
   int foo ()
   {
  return 0;
   }
   int foo ()
   {
  return 0;
   }
};
```

result from clang++:

ddcpp.cc:7:8: error: class member cannot be redeclared
   int foo ()
   ^
ddcpp.cc:3:8: note: previous declaration is here
   int foo ()
   ^
ddcpp.cc:7:8: error: redefinition of 'foo'
   int foo ()
   ^
ddcpp.cc:3:8: note: previous definition is here
   int foo ()
   ^
2 errors generated.

Re: dmd 2.093.1: duplicate method definitions ignored altogether

[Paul Backus via Digitalmars-d-learn]

On Tuesday, 5 January 2021 at 02:02:39 UTC, kdevel wrote:
expected output: none. The compiler should have rejected the 
code after the duplicate definition def #2. dmd 2.093.1 ignores 
both definitions instead. Is this a bug or a bug?


If you try to call .toString directly on a const(S), you get the 
following error:


onlineapp.d(27): Error: onlineapp.S.toString called with argument 
types () const matches both:

onlineapp.d(9): onlineapp.S.toString() const
and:
onlineapp.d(13): onlineapp.S.toString() const

The reason it is ignored when using writeln is that writeln uses 
__traits(compiles) to check whether it can call toString on a 
const(S). Since the call does not compile, it falls back to the 
default struct formatting code, which produces the output you saw 
in your example.

dmd 2.093.1: duplicate method definitions ignored altogether

[kdevel via Digitalmars-d-learn]

~~~tsnf.d
import std.stdio: writeln;

struct S {
   string s;
   string toString ()
   {
  return __PRETTY_FUNCTION__ ~ `: ` ~ s;
   }
   string toString () const // def #1
   {
  return __PRETTY_FUNCTION__ ~ `: ` ~ s;
   }
   const string toString () // def #2
   {
  return __PRETTY_FUNCTION__ ~ `: ` ~ s;
   }
}

void foo (T) (in ref T t) // fancy way of declaring t const
{
   writeln (t);
}

int main ()
{
   S s;
   writeln (s);
   foo (s);
   return 0;
}
~~~

$ dmd tsnf
$ ./tsnf
string tsnf.S.toString():
const(S)("")

expected output: none. The compiler should have rejected the code 
after the duplicate definition def #2. dmd 2.093.1 ignores both 
definitions instead. Is this a bug or a bug?