create a mutable map from this

NYI: maybe add default implementation when there is a naive implementation only requiring property.equatable

create a string containing all mappings

dynamic_apply -- apply `f.call` to `Any.this`'s dynamic type and value

This can be used to perform operation on values depending on their dynamic
type.

Here is an example that takes a `Sequence Any` that may contain boxed values
of types `i32` and `f64`. We can now write a feature `get_f64` that extracts
these values converted to `f64` and build a function `sum` that sums them up
as follows:


NYI: IMPROVEMENT: #5892: If this is fixed, we could write

Get the dynamic type of this instance. For value instances `x`, this is
equal to `type_of x`, but for `x` with a `ref` type `x.dynamic_type` gives
the actual runtime type, while `type_of x` results in the static
compile-time type.

There is no dynamic type of a type instance since this would result in an
endless hierarchy of types. So for Type values, dynamic_type is redefined
to just return Type.type.

check if key k is present in the set of keys

get the value k is mapped to, or nil if none.

get a sequence of all key/value pairs in this map

get a sequence of all keys in this map

convenience prefix operator to create a string from a value.

This permits usage of `$` as a prefix operator in a similar way both
inside and outside of constant strings: $x and "$x" will produce the
same string.

returns a new Persistent_Map
which contains all entries of the
current Map and k,v.
An already existing k will be replaced.

number of entries in this map

get a sequence of all values in this map

string representation of this type to be used for debugging.

result has the form "Type of '<name>'", but this might change in the future

There is no dynamic type of a type instance since this would result in an
endless hierarchy of types, so dynamic_type is redefined to just return
Type.type here.

initializer for this map

every map implementation needs to implement this

Is this type assignable to a type parameter with constraint `T`?

The result of this is a compile-time constant that can be used to specialize
code for a particular type.


it is most useful in conjunction with preconditions or `if` statements as in


or

name of this type, including type parameters, e.g. 'option (list i32)'.

convenience prefix operator to create a string from a value.

This permits usage of `$` as a prefix operator in a similar way both
inside and outside of constant strings: $x and "$x" will produce the
same string.

NYI: Redefinition allows the type feature to be distinguished from its normal counterpart, see #3913

Get a type as a value.

This is a feature with the effect equivalent to Fuzion's `expr.type` call tail.
It is recommended to use `expr.type` and not `expr.type_value`.

`type_value` is here to show how this can be implemented and to illustrate the
difference to `dynamic_type`.