Scala macros is a facility for Scala—a general-purpose programming language—that permits compile-time metaprogramming against Scala syntax trees, from within the Scala language.
Questions tagged [scala-macros]
774 questions
0
votes
1 answer
How to pass parameters to annotation with macro expansions
I'm using macros annotation for generating code. I would like to change its behaviour based on additional string parameters. So it would produce different results for same code. I closely followed the guide for macro annotations that covers only…
ayvango
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1 answer
scala proxy macro, issue converting method args to values
I am trying to write a proxy macro using scala macros. I want to be able to proxy a trait X and return instances of X that invoke a function for all methods of X.
Here is what I did so far. Say we want to proxy the trait TheTrait (which is defined…
kostas.kougios
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use scala macro annotation to create type and method definition at the same level
I created a macro annotation to be used together with another macro to transform case classes into records with dynamic, typed method…
cedric
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Deferring implicit resolution in macros
So, lets say I have a few things before hand:
case class M[A](val value: A) {
def apply(as: M[A]*) = macro applyImpl[A]
}
def tpAware(implicit ev: Context[A]): M[A]
val ma: M[X] = ???
I want to do:
ma(tpAware)
Where applyImpl is defined…
pfn
- 1,820
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Calling function with implicit parameter from quasioquote
For some reason every time I try to call a function with an implicit parameter from quasiquotes, it fails with
Can't unquote x.universe.Tree, consider providing an implicit instance of Liftable[x.universe.Tree]
What's wrong with that? Am I not…
ilinum
- 464
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Convert scala collections in nested case class to java equivalent
I have some case classes:
case class Address(street : String, state : String, zip : Option[Int])
case class Person(name : String, address : Option[Address], children : Seq[Person])
and a function that returns one of these classes:
def getPerson()…
mushroom
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2 answers
Passing type Parameter to reify while implementing a scala macro
Going from the following macro implementation, which is working as expected, i would like to remove the hard coded Account and replace it with a variable beeing passed as type parameter T:c.WeakTypeTag to the macro by the caller.
how should the…
Bate
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- 8
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1 answer
Scala macros Type or Symbol lifted
I'm trying to use the fields of a type in a macro, and pass the symbol or typesigs for the fields to a method so I can do some operations that require concrete information about the type.
I have code like this (played about with variations):
object…
sksamuel
- 16,154
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Generate a new value in Scala AST
I'm using APIs to reconstruct the scala AST during compiling.
I want to change an "Apply" AST like
a(1)
into an "Assign and Return" Block
{
val newvalue = a(1)
newvalue
}
And here's my code for generating a new value in AST:
val newVal : Tree =…
user5279007
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How to use cq in quasi quote to return the matched pattern
I am trying to write this case authorDao: AuthorDao => authorDao so that it returns the subclass of Dao itself.
When I use this quasi quote:
val daoType = TypeName(daoName)
val caseTerm = TermName(daoName.toLowerCase)
cases.append(cq"$caseTerm:…
user1187135
0
votes
0 answers
Passing & validating multiple values to Scala macro
So, I am new to macros in Scala and am having some difficulty with my current objective. I have a class that performs Json parsing of case classes. If the given case class has fields that are of type Enumeration, an implicit array of those…
Jake Sankey
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1 answer
Debug macro annotation in Intellij
While debuging macro annotation IntelliJ throws this error:
test\UseMacro.scala:7: error: macro annotation could not be expanded (the most common reason for that is that you need to enable the macro paradise plugin; another possibility is that you…
Daryl
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Scala IDE 4.1 and SBT
We have a project that uses Scala macros. Scala IDE 4.1 supports Scopes to ease compilation of projects with macros. However, when I use sbt eclipse, the generated project does not show macros as a source folder and does not create separate outputs…
Wickoo
- 6,745
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1 answer
Writing Macro for Positive Integers
Given the following types:
sealed trait PosIntCheckResult
case class LteZero(x: Int) extends PosIntCheckResult
case object NotConstant extends PosIntCheckResult
I'm trying to write a macro that checks whether the given Int is greater than 0.
import…
Kevin Meredith
- 41,036
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Can I add class fields dynamically using macros?
I'm new to Scala macros, so sorry if this is an obvious question.
I wonder if the following is even possible before I dig in deeper.
Let's say I have a class named DynamicProperties
Is it possible to add members to the class based on something like…
Eran Medan
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