Closed
Description
Minimized example
The example code for "Recovering precise types using patterns" does not compile. Here is the code:
extension (inline sc: StringContext) inline def showMe(inline args: Any*): String = ${ showMeExpr('sc, 'args) }
private def showMeExpr(sc: Expr[StringContext], argsExpr: Expr[Seq[Any]])(using QuoteContext): Expr[String] = {
argsExpr match {
case Varargs(argExprs) =>
val argShowedExprs = argExprs.map {
case '{ $arg: t } =>
Expr.summon[Show[t]] match {
case Some(showExpr) => '{ $showExpr.show($arg) }
case None => Reporting.error(s"could not find implicit for ${showTp.show}", arg); '{???}
}
}
val newArgsExpr = Varargs(argShowedExprs)
'{ $sc.s($newArgsExpr: _*) }
case _ =>
// `new StringContext(...).showMeExpr(args: _*)` not an explicit `showMeExpr"..."`
Reporting.error(s"Args must be explicit", argsExpr)
'{???}
}
}
trait Show[-T] {
def show(x: T): String
}Output
[error] -- [E006] Not Found Error: RecordMacro.scala:400:24
[error] 400 | case '{ $arg: t } =>
[error] | ^
[error] | Not found: type t
[error] -- [E006] Not Found Error: RecordMacro.scala:401:27
[error] 401 | Expr.summon[Show[t]] match {
[error] | ^
[error] | Not found: type t
[error] -- [E006] Not Found Error: RecordMacro.scala:403:25
[error] 403 | case None => Reporting.error(s"could not find implicit for ${showTp.show}", arg); '{???}
[error] | ^^^^^^^^^
[error] | Not found: Reporting
[error] -- [E006] Not Found Error: RecordMacro.scala:410:8
[error] 410 | Reporting.error(s"Args must be explicit", argsExpr)
[error] | ^^^^^^^^^
[error] | Not found: Reporting
[error] four errors found
1 targets failed
dcase2020.compile Compilation failedExpectation
Expected it to compile. Tested with 3.0.0-M1. With the changes below I am left with the error related to the t type variable.
extension (inline sc: StringContext) inline def showMe(inline args: Any*): String = ${ showMeExpr('sc, 'args) }
private def showMeExpr(sc: Expr[StringContext], argsExpr: Expr[Seq[Any]])(using QuoteContext): Expr[String] = {
argsExpr match {
case Varargs(argExprs) =>
val argShowedExprs = argExprs.map {
case '{ $arg: t } =>
Expr.summon[Show[t]] match {
case Some(showExpr) => '{ $showExpr.show($arg) }
case None => report.error(s"could not find implicit for ${arg.show}", arg); '{???}
}
}
val newArgsExpr = Varargs(argShowedExprs)
'{ $sc.s($newArgsExpr: _*) }
case _ =>
// `new StringContext(...).showMeExpr(args: _*)` not an explicit `showMeExpr"..."`
report.error(s"Args must be explicit", argsExpr)
'{???}
}
}
trait Show[-T] {
def show(x: T): String
}