build.sbt

val scala3Version = "3.2.0"
lazy val root = project
  .in(file("."))
  .settings(
    name := "macro-repro",
    version := "0.1.0-SNAPSHOT",
    scalaVersion := scala3Version,
  )

Foo.scala

class Foo[F[_]] {
  
}

Main.scala

object Main:
  def main(args: Array[String]):Unit = println(SourceMacro.getContent[Foo[?]])
end Main

SourceMacro.scala

object SourceMacro {
  import scala.quoted.*

  inline def getContent[A]: String = ${getContentImpl[A]}

  def getContentImpl[A: Type](using Quotes): Expr[String] =
    import quotes.reflect.*
      // for the source specifically of A
    // val str = TypeRepr.of[A].typeSymbol.tree.pos.sourceCode.getOrElse(
    //   report.errorAndAbort("no source code")
    // )

      // for the whole source file containing the definition of A
    val str = TypeRepr.of[A].typeSymbol.pos.getOrElse(
      report.errorAndAbort("no symbol position")
    ).sourceFile.content.getOrElse(
      report.errorAndAbort("no source-file content")
    )

    Expr(str)
}