[Macros] Passing context instance reference to another class

[Alexander Myltsev]

Hi!

I have code:

object Parser {
  type ParserContext = Context { type PrefixType = Parser }

  def ruleImpl(c: ParserContext)(r: c.Expr[Rule]): c.Expr[Boolean] = {
    val opTreeContext = new OpTreeContext(c)
    val opTree = opTreeContext.parse(r.tree) // Compilation error (see below): Parser.scala: type mismatch;
    opTree.render
  }
}

class OpTreeContext(c: Parser.ParserContext) {
  import c.universe._

  def parse(tree: c.Tree): Expression = ???
}

Compiler is not happy with error:
[error] Parser.scala: type mismatch;
[error]  found   : c.universe.Tree
[error]  required: opTreeContext.c.Tree
[error]     (which expands to)  opTreeContext.c.universe.Tree
[error]     val opTree = opTreeContext.parse(r.tree)
[error]                                        ^


Why type of `c` in OpTreeContext differs from type of `r.tree` in `ruleImpl`? And how to pass instance reference of Parser.ParserContext to another class?

Regards,
  Alexander

[Johannes Rudolph]

Hi Alexander,

have you seen this section in the documentation:

http://docs.scala-lang.org/overviews/macros/overview.html#writing_bigger_macros

You probably need a type parameter on OpTreeContext for the context.

Johannes

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Johannes

-----------------------------------------------
Johannes Rudolph
http://virtual-void.net

[Alexander Myltsev]

Johaness,

that is exactly I was searching for! I didn't give much attention while was reading at first time. Thanks!

A.