Bug 24334 – parameter name is ignored in invocation of struct constructor with default values

struct Foo { this(int a, int b = 2, int c = 3) { imported!"std.stdio".writefln!"a=%s b=%s c=%s"(a, b, c); } } void main() { auto foo = Foo(1, c: 99); } Expected output: a=1 b=2 c=99 Actual output: a=1 b=99 c=3 (This bug is dangerous, and quite shocking for a mature language.) Note that the problem is only with a constructor. e.g, this works correctly: struct Bar { static void bar(int a, int b = 2, int c = 3) { imported!"std.stdio".writefln!"a=%s b=%s c=%s"(a, b, c); } } void main() { Bar.bar(1, c: 99); } output: a=1 b=2 c=99

P.S. The default constructor works correctly: struct Foo { int a, b = 2, c = 3; } void main() { auto foo = Foo(1, c: 99); imported!"std.stdio".writefln!"a=%s b=%s c=%s"(foo.a, foo.b, foo.c); } output: a=1 b=2 c=99

> and quite shocking for a mature language Named parameters are not mature, support began to be added in the April release last year. They were not mentioned in any changelogs and should have been behind a preview switch*. But the spec was updated, it should perhaps have a warning about stability. * https://forum.dlang.org/post/[email protected]

This has been fixed by https://github.com/dlang/dmd/pull/15662 The output I get with dmd master is: ``` a=1 b=2 c=99 ``` Which is your expected output. Please update your compiler version.

2.103.1 to 2.104.2: Success with output: a=1 b=99 c=3 Since 2.105.3: Success with output: a=1 b=2 c=99

> it should perhaps have a warning about stability Or perhaps the compiler test suite should cover basic aspects of the feature.

> Or perhaps the compiler test suite should cover basic aspects of the feature. It did by the time the spec mentioned named arguments.