lampepfl/dotty-macro-examples

Various tasks solved via metaprogramming in Dotty

dotty-macro-examples's Issues

A ternary operator example wanted

Could it be possible with Dotty to write some macro for ternary operator that would replace

A ? B : C

by

if (A)
  B
else
  C

without adding an overhead in runtime?

Compile all these examples using `-Xcheck-macros`

Expand case class default values example

Hi,

I think this defaultParamsInference is a great example I'd like to extend further to include the type of each case class field.

What amazes me is I didn't realize you can cast a Tree as you do here:
https://github.com/lampepfl/dotty-macro-examples/blob/main/defaultParamsInference/src/macro.scala#L18

I thought I would need to use the Symbol's signature to get the type but I don't see a lot of documentation for signature or how to access type information (such as individually selecting types from higher orders, such as List[Int], as enabled in scala 2 by typeSignature or scala.reflect.macros.Context.typeCheck).

So can someone please clarify how tree or signature can be used to get detailed type information for each case class field?

Thanks!

Fail to update the version to 3.0.0

I try to update the version to 3.0.0 in build.sc:

def scalaVersion = "3.0.0"

When try to run mill abstractTypeclassBody.run I see:

[20/38] abstractTypeclassBody.resolvedIvyDeps | Downloading [2/2] artifacts (~0/0 bytes)
1 targets failed
abstractTypeclassBody.resolvedIvyDeps 
Resolution failed for 1 modules:
--------------------------------------------
  org.scala-lang:scala3-library_3.0:3.0.0 
	not found: /home/shapeless-cat/.ivy2/local/org.scala-lang/scala3-library_3.0/3.0.0/ivys/ivy.xml
	not found: https://repo1.maven.org/maven2/org/scala-lang/scala3-library_3.0/3.0.0/scala3-library_3.0-3.0.0.pom

Upgrade to 3.0.0-M3

Seems quite a lot staff changed in 3.0.0-M3

Instantiate a class from a Map

May you add the example: instantiate a class from a Map

    case class Foo(a: Int, c: String)
    val params: Map[String, String] = Map("a" -> "1", "c" -> "hi")
    fromParams[Foo](params) // Right(Foo(1, "hi")))

nice to have example

It would be nice to have an example where a macro runs inside a function, but it returns a tuple of the function name and an Object that has the parameters as vals and the parameter values as typed values.

def blah(x: Int, y: String, z: Float) =
  val (name, params) = functionMacro
  println("x value in function $name is ${params.x}")