On Friday, 12 September 2025 at 09:17:10 UTC, realhet wrote:
On Friday, 12 September 2025 at 08:44:47 UTC, Stefan Koch wrote:
On Friday, 12 September 2025 at 08:36:42 UTC, realhet wrote:
Hi, thanks for quick answer!
When I turn the string mixin into a statement by putting a `;`
at its end, the
enum bla = `(){return 4;}();`
`mixin(bla);` Case works perfectly. It just drops its return
statement;
But now the expression variant drops an error:
`auto x = mixin(bla);`
```
Error: unexpected token `;` after call expression
while parsing string mixin expression
```
So my problem is that before 1.41 both versions went fine with
the expr mixin template.
enum bla = `(){return 4;}();`;
mixin(bla); //Compiles, drops the return value
auto x = mixin(bla); //Compiles, stores the return value in
variable `x`
I don't think so, according to `run.dlang.org`:
```d
void main() {
enum bla = `(){return 4;}();`;
mixin(bla);
auto x = mixin(bla);
}
```
rdmd playground.d
```
Up to 2.078.3: Failure with output: onlineapp.d(4): Error:
incomplete mixin expression ("(){return 4;}();")
2.079.1 to 2.082.1: Failure with output: onlineapp.d(4): Error:
incomplete mixin expression `"(){return 4;}();"`
2.083.1 to 2.105.3: Failure with output: onlineapp.d(4): Error:
incomplete mixin expression `(){return 4;}();`
Since 2.106.1: Failure with output:
-----
onlineapp.d-mixin-4(4): Error: unexpected token `;` after call
expression
onlineapp.d-mixin-4(4): while parsing string mixin
expression `(){return 4;}();`
-----
```
So it seems it's been an error for many years, it just became
clearer since 2.106.
At this point of understanding, I can solve this in a manual
way by using 2 string mixins: an expression mixin and a
statement mixin. I'm only a bit sad, that in the past it was
fully automatic.
I think back then compiler verified it the mixin is a statement
or an expression at a later state.
But now as you said, it expects one of them by checking the
place of mixin insertion:
- if it finds an `=`, then it must be a mixin expression. <-
this expectation is valid
- if it does not find an `=`, then it must be a mixin
statement. <- Now this is bad, because `xxx;` xxx can be BOTH
a mixin statement and a mixin expression(with side effects and
unused return value).
The rules are simple - if it can be a mixin statement, it is.
Otherwise it is a mixin expression (or mixin type).
