Swift Target: Need to Override init(_ input: CharInputStream)

[patersoz]

I've converted the grammars used by the PKL Lang project (https://github.com/apple/pkl/blob/0.26.1/pkl-core/src/main/antlr/PklLexer.g4) from Java to Swift targets.

It has all been relatively painless, except in the PklLexer.g4 java grammar there is the following @members entry:

class StringInterpolationScope {
  int parenLevel = 0;
  int poundLength = 0;
}

java.util.Deque<StringInterpolationScope> interpolationScopes = new java.util.ArrayDeque<>();
StringInterpolationScope interpolationScope;

{ pushInterpolationScope(); }

void pushInterpolationScope() {
  interpolationScope = new StringInterpolationScope();
  interpolationScopes.push(interpolationScope);
}

Swift doesn't allow (as far as I know) something like:

{ pushInterpolationScope(); }

And it won't allow the generated init(_ input: CharInputStream) initializer because it hasn't initialised "interpolationScope" by the time super.init() is called. So to get it to work I have to manually move the two code lines in pushInterpolationScope down to the init initializer.

Once I do that everything works, well. But of course now I have a manual intervention in my lexer generation. In all likelihood I won't be running the generation that often so I can live with the work around.

But I was wondering if there was a way to override what the Target generator is producing for init(_ input: CharInputStream)?