https://issues.dlang.org/show_bug.cgi?id=17477

Eyal <eyal@weka.io> changed:

           What    |Removed                     |Added
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           Keywords|                            |diagnostic

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https://issues.dlang.org/show_bug.cgi?id=17477

Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Hardware|x86_64                      |All
                 OS|Linux                       |All

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https://issues.dlang.org/show_bug.cgi?id=17477

Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> changed:

           What    |Removed                     |Added
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           See Also|                            |https://issues.dlang.org/sh
                   |                            |ow_bug.cgi?id=10602

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https://issues.dlang.org/show_bug.cgi?id=17477

Iain Buclaw <ibuclaw@gdcproject.org> changed:

           What    |Removed                     |Added
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           Priority|P1                          |P3

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https://issues.dlang.org/show_bug.cgi?id=17477

RazvanN <razvan.nitu1305@gmail.com> changed:

           What    |Removed                     |Added
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             Status|NEW                         |RESOLVED
                 CC|                            |razvan.nitu1305@gmail.com
         Resolution|---                         |WORKSFORME

--- Comment #1 from RazvanN <razvan.nitu1305@gmail.com> ---
This code now compiles because the compiler does inference for function literals.

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https://issues.dlang.org/show_bug.cgi?id=17477

Eyal <eyal@weka.io> changed:

           What    |Removed                     |Added
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             Status|RESOLVED                    |REOPENED
         Resolution|WORKSFORME                  |---

--- Comment #2 from Eyal <eyal@weka.io> ---
It is true that this *specific* example now compiles, but if you extract g() to the global scope it shows the problem again:

void f(void delegate(int) nothrow dlg) {}

void g(int x) {}

void main() {
    f((x){ g(x); });
}

  Error: function `testfuncliteral.f(void delegate(int) nothrow dlg)` is not
  callable using argument types `(void)`
         cannot pass argument `__lambda1` of type `void` to parameter `void
delegate(int) nothrow dlg`

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https://issues.dlang.org/show_bug.cgi?id=17477

Nick Treleaven <nick@geany.org> changed:

           What    |Removed                     |Added
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                 CC|                            |nick@geany.org

--- Comment #3 from Nick Treleaven <nick@geany.org> ---
> This is wrong, as the argument type is not (void).

The type of a template is void. A lambda without parameter types is a template. When a template lambda doesn't implicitly convert to the expected parameter type, it's not established what the type of the implicitly instantiated lambda is, as it failed to instantiate.

> It is also very difficult to figure out what is wrong with this program from this error (when the code is far more complicated).

The fix for issue #10602 gives:

/home/nick/old/lambdaarg.d(16): Error: function `lambdaarg.f(void delegate(int)
nothrow dlg)` is not callable using argument types `(void)`
/home/nick/old/lambdaarg.d(16):        cannot implicitly convert expression
`__lambda2` of type `void delegate(int x) @system` to `void delegate(int)
nothrow`

Note the inferred argument type that the compiler tried on the second line.

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https://issues.dlang.org/show_bug.cgi?id=17477

--- Comment #4 from Eyal <eyal@weka.io> ---
With the fix for issue #10602 - it sounds much better, though even then I don't think the error should say:

  function `lambdaarg.f(void delegate(int) nothrow dlg)` is not callable using
argument types `(void)`

but rather:

  function `lambdaarg.f(void delegate(int) nothrow dlg)` is not callable using
given template, as it failed to instantiate:

And this is much clearer direction for the programmer to read the actual problem on the next line.

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https://issues.dlang.org/show_bug.cgi?id=17477

--- Comment #5 from Nick Treleaven <nick@geany.org> ---
In this case, yes. But the first line is supposed to show all the argument types passed to the function. E.g. when there's more than one argument.

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https://issues.dlang.org/show_bug.cgi?id=17477

--- Comment #6 from Eyal <eyal@weka.io> ---
Then perhaps instead of "void" it is better to spell out "template instantiation failure, see below" as the type itself.

Verbose, maybe, but clearer how to progress

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