Re: Why can't I assign a mixin to an alias?
On Saturday, 11 June 2016 at 01:53:10 UTC, David Nadlinger wrote: This might be a gratuitous grammar restriction. There are a few of those surrounding alias "targets". A template that simply returns its parameter might work, though, such as std.meta.Alias (alias foo = Alias!(mixin(…));). It seems to be that it would be a good idea to file this in as a suggested change/fix. Do I have support?
Re: Why can't I assign a mixin to an alias?
On Saturday, 11 June 2016 at 02:46:00 UTC, Adam D. Ruppe wrote: On Saturday, 11 June 2016 at 02:33:46 UTC, Alex Parrill wrote: Mixins are statements. No, they're not. Well, yes they are [1], but there are also mixin expressions [2]. Not to be confused with the TemplateMixin[3], which is indeed always a statement. 1: http://dlang.org/spec/grammar.html#MixinExpression 2: http://dlang.org/spec/grammar.html#MixinStatement 3: http://dlang.org/spec/grammar.html#TemplateMixin Huh, every time I've used mixins, I've always run into the issue in the OP, so I assumed they were statements. It definitely seems like a bug then.
Re: Why can't I assign a mixin to an alias?
On Saturday, 11 June 2016 at 02:33:46 UTC, Alex Parrill wrote: Mixins are statements. No, they're not. Well, yes they are [1], but there are also mixin expressions [2]. Not to be confused with the TemplateMixin[3], which is indeed always a statement. 1: http://dlang.org/spec/grammar.html#MixinExpression 2: http://dlang.org/spec/grammar.html#MixinStatement 3: http://dlang.org/spec/grammar.html#TemplateMixin
Re: Why can't I assign a mixin to an alias?
On Friday, 10 June 2016 at 22:38:29 UTC, Dechcaudron wrote:
I have the following code:
private string getVariableSignalWrappersName(VarType)()
{
return VarType.stringof ~ "SignalWrappers";
}
void addVariableListener(VarType)(int variableIndex, void
delegate(int, VarType))
{
alias typeSignalWrappers =
mixin(getVariableSignalWrappersName!VarType);
}
On compilation, the following error is issued:
Error: basic type expected, not mixin
Why should it be like that? I believe the compiler should not
impose restrictions on what mixins can or cannot do :/
Mixins are statements. They cannot be a part of an expression.
The other two posts have demonstrated how to get around this.
Re: Why can't I assign a mixin to an alias?
On Friday, 10 June 2016 at 22:38:29 UTC, Dechcaudron wrote: Error: basic type expected, not mixin Why should it be like that? I believe the compiler should not impose restrictions on what mixins can or cannot do :/ This might be a gratuitous grammar restriction. There are a few of those surrounding alias "targets". A template that simply returns its parameter might work, though, such as std.meta.Alias (alias foo = Alias!(mixin(…));). — David
Re: Why can't I assign a mixin to an alias?
On Friday, 10 June 2016 at 22:38:29 UTC, Dechcaudron wrote:
I have the following code:
private string getVariableSignalWrappersName(VarType)()
{
return VarType.stringof ~ "SignalWrappers";
}
void addVariableListener(VarType)(int variableIndex, void
delegate(int, VarType))
{
alias typeSignalWrappers =
mixin(getVariableSignalWrappersName!VarType);
}
On compilation, the following error is issued:
Error: basic type expected, not mixin
Why should it be like that? I believe the compiler should not
impose restrictions on what mixins can or cannot do :/
I'm no expert, but this looks like a grammar issue more than
anything else. You can work around it by moving the alias
declaration into the mixin.
mixin("alias typeSignalWrappers = " ~
getVariableSignalWrappersName!VarType ~ ";");
Why can't I assign a mixin to an alias?
I have the following code:
private string getVariableSignalWrappersName(VarType)()
{
return VarType.stringof ~ "SignalWrappers";
}
void addVariableListener(VarType)(int variableIndex, void
delegate(int, VarType))
{
alias typeSignalWrappers =
mixin(getVariableSignalWrappersName!VarType);
}
On compilation, the following error is issued:
Error: basic type expected, not mixin
Why should it be like that? I believe the compiler should not
impose restrictions on what mixins can or cannot do :/
