Optional default tag for union type

[nellaG]

implements #13 .

[nellaG]

oh my

[checkmate-bot]

Checklist 🤔

src/Nirum/Parser.hs

• If a new reserved keyword is introduced, it has to be also added to reservedKeywords set in the Nirum.Constructs.Identifier module.

[kanghyojun]

I changed template engine of union type on Python target as well. cc @nellaG @dahlia

[nellaG]

👍

[dahlia]

Need changelog as well.

[dahlia]

This check comment should go to the top of Parser.hs source. See also Checkmate docs. Since it's sensitive to block indentation levels, if a CHECK comment is too deeply inside it could be hardly warned.

[dahlia]

Despite this kind of conditionals are necessary for the runtime library to be compatible old and new versions of the compiler, it's no more needed for compiler-generated codes; it's guaranteed that it's always generated by the new one.

[dahlia]

These toStrict $ renderMarkup ... codes have remained by intention; they need to be merely removed in the near future by replacing type CompileResult Python = Code with type CompileResult Python = BI.Markup.

[dahlia]

We don't need to define tags like the following code in where clause:

tags :: [Tag]
tags = findTags u

Instead we can just match both of UnionType and its tags:

, type' = u@(UnionType tags)

Also we should rename u to better one.

[dahlia]

Since we now have proper conditionals through Heterocephalus, things like arg "cls" "type" or ret className can be avoided. See also compileTypeDeclaration function for EnumType:

    @classmethod
%{ case pyVer }
%{ of Python2 }
    def __nirum_deserialize__(cls, value):
%{ of Python3 }
    def __nirum_deserialize__(cls: type, value: str) -> '#{className}':
%{ endcase }
        return cls(value.replace('-', '_'))  # FIXME: validate input

[dahlia]

👏