MixinConstraints

Mixes in constraints into another mixin template, to provide static guarantees that it is not mixed into a type of scope other than the one specified.

Using this you can ensure that a mixin template meant to be mixed into a class isn't mixed into a module-level scope, or into a function, etc.

More than one scope type can be supplied with bitwise OR.

mixin template MixinConstraints (

MixinScope mixinScope

string mixinName = "a constrained mixin"

) {}

Parameters

mixinScope: The scope into which to only allow the mixin to be mixed in. All other kinds of scopes will be statically rejected.
mixinName: Optional string name of the mixing-in mixin. Can be anything; it's just used for the error messages.

Examples

module foo;

mixin template Foo()
{
    mixin MixinConstraints!(MixinScope.module_, "Foo");  // Constrained to module-level scope
}

mixin Foo;  // no problem, scope is MixinScope.module_

void bar()
{
    mixin Foo;  // static assert(0): scope is MixinScope.function_, not MixinScope.module_
}

class C
{
    mixin Foo;  // static assert(0): ditto but MixinScope.class_
}

struct C
{
    mixin Foo;  // static assert(0): ditto but MixinScope.struct_
}

mixin template FooStructOrClass()
{
    mixin MixinConstraints(MixinScope.struct_ | MixinScope.class_);
}

void fun()
{
    // MixinConstraints!(MixinScope.function_, "TestMixinConstrainedToFunctions");
    mixin TestMixinConstrainedToFunctions;
}

class TestClassC
{
    // MixinConstraints!(MixinScope.class_, "TestMixinConstrainedToClass");
    mixin TestMixinConstrainedToClass;
}

struct TestStructS
{
    // mixin MixinConstraints!(MixinScope.struct_, "TestMixinConstrainedToStruct");
    mixin TestMixinConstrainedToStruct;
}

struct TestStructS2
{
    mixin TestMixinConstrainedToClassOrStruct;
}

MixinConstraints

Parameters

Examples

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