Implement user-defined type guard method#1501
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| def context_from(type_name) | ||
| if type_name.namespace == RBS::Namespace.root | ||
| [nil, type_name] | ||
| else | ||
| parent = context_from(type_name.namespace.to_type_name) | ||
| [parent, type_name] | ||
| end | ||
| end |
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I could not find such a helper method in Steep and RBS.
I'm not sure where the best place is.
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This implements the minimal version of user-defined type guard method.
A user-defined type guard methos is a method defined by user that is
able to guarantee the type of the objects (receiver or arguments).
At present, Steep supports type guard methods provided by ruby-core (ex.
`#is_a?`, `#nil?`, and so on). But we also have many kinds of
user-defined methods that are able to check the type of the objects.
Therefore user-defined type guard will help checking the type of these
applications by narrowing types.
This implementation uses an annotation to declare user-defined type
guard method.
```
class Example < Integer
%a{guard:self is Integer}
def integer?: () -> bool
end
```
For example, the above method `Example#integer?` is a user-defined
type guard method that narrows the Example object itself to an Integer
if the conditional branch passed.
```
example = Example.new
if example.integer?
example #=> Integer
end
```
In this PR, the predicate of type guards only supports "self is TYPE"
statement. I have a plan to extend it:
* `%a{guard:self is arg}`
* `%a{guard:self is_a arg}`
* `%a{guard:self is TYPE_PARAM}`
* `%a{guard:arg is TYPE}`
Note: The compatibility of RBS syntax is the large reason of using
annotations. I'm afraid that adding a new syntax to define it will
bring breaking change to the RBS, and difficult to use it on common
repository or generators (ex. gem_rbs_collection and rbs_rails).
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This implements the minimal version of user-defined type guard method. A user-defined type guard methos is a method defined by user that is able to guarantee the type of the objects (receiver or arguments).
At present, Steep supports type guard methods provided by ruby-core (ex.
#is_a?,#nil?, and so on). But we also have many kinds of user-defined methods that are able to check the type of the objects.Therefore user-defined type guard will help checking the type of these applications by narrowing types.
This implementation uses an annotation to declare user-defined type guard method.
For example, the following method
Example#integer?is a user-defined type guard method that narrows the Example object itself to an Integer if the conditional branch passed.In this PR, the predicate of type guards only supports "self is TYPE" statement. I have a plan to extend it:
%a{guard:self is arg}%a{guard:self is_a arg}%a{guard:self is TYPE_PARAM}%a{guard:arg is TYPE}Note: The compatibility of RBS syntax is the large reason of using annotations. I'm afraid that adding a new syntax to define it will bring breaking change to the RBS, and difficult to use it on common repository or generators (ex. gem_rbs_collection and rbs_rails).
refs: