Bug 15732 – std.function partial does not work with function / delegate references

Created attachment 1587 Example of error using partial with delegate reference Trying to use "partial" from "std.function" with a variable referring to a function or delegate does not behave as expected. See "example_error.d" for unexpected behaviour. ketmar, on #d observed that the issue is either with DMD or with phobos: either `is(typeof(basic) == function)` should be true there (and then it's dmdfe bug), or `partial` should use `isCallable` (and then it's phobos bug) He was able to provide a fix with the following: i changed `static if (is(typeof(fun) == delegate) || is(typeof(fun) == function))` line in `partial` to `static if (isCallable!fun)` Which I will attach as an example.

Created attachment 1588 Examle of "fixed" partial

Example of error: auto partial_application () { // definition of a basic function on 3 parameters using lambda syntax auto basic = (float a, float b, float c) => a + b / c; // partially apply value to basic import std.functional : partial; alias partial!(basic, 1) apply1; return &apply1; // Error: partial(Ts...)(Ts args2) is not an lvalue } void main(string[] args) { auto test = partial_application(); import std.stdio : writeln; writeln("result: ", test(1, 2, 3)); }

Since the https://github.com/dlang/phobos/pull/6497 was merged, a fixed version of the example above compiles: auto partial_application () { // definition of a basic function on 3 parameters using lambda syntax auto basic = (float a, float b, float c) => a + b / c; // partially apply value to basic import std.functional : partial; alias partial!(basic, 1) apply1; return &apply1; // now OK, didn't compile before } void main(string[] args) { auto test = partial_application(); import std.stdio : writeln; writeln("result: ", test(2, 3)); // 1 + (2/3) = 1.66667 } I see no reason why the GitHub -> Bugzilla integration didn't close the issue automatically, so I'm closing it manually.

It seems, this was not actually closed. Closing it now.