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Fix interpretation of Typed trees #3852

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Merged
merged 1 commit into from
Jan 18, 2018
Merged

Fix interpretation of Typed trees #3852

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5 changes: 4 additions & 1 deletion compiler/src/dotty/tools/dotc/interpreter/Interpreter.scala
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Expand Up @@ -111,10 +111,13 @@ class Interpreter(implicit ctx: Context) {
val env2 = bindings.foldLeft(env)((acc, x) => interpretStat(x, acc))
interpretTreeImpl(expansion, env2)

case Typed(expr, _) =>
interpretTreeImpl(expr, env)
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Do we need a check here? Maybe not.

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What kind of check? This is a fully typed tree, we evaluate it's erased version.

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I was thinking to check the type, but it's not the semantics of the language. So ignore the comment.


case _ =>
// TODO Add more precise descriptions of why it could not be interpreted.
// This should be done after the full interpreter is implemented.
throw new StopInterpretation(s"Could not interpret ${tree.show}\n${tree}", tree.pos)
throw new StopInterpretation(s"Could not interpret ${tree.show}. Consider extracting logic into a helper def.", tree.pos)
}
}

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2 changes: 2 additions & 0 deletions tests/run/quote-splice-interpret-1.check
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@@ -0,0 +1,2 @@
true
false
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How can I be sure the output is from compile-time, not run-time?

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Because the inline def has a top level ~ it can always be inlined. Then the inlined tree is interpreted to evaluate the Expr[T] which is then spliced in (see #3853 for a bit of info on that regard).
In short a macro call is guaranteed to be inlined or the compilation fails.

14 changes: 14 additions & 0 deletions tests/run/quote-splice-interpret-1/Macro_1.scala
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@@ -0,0 +1,14 @@
import dotty.tools.dotc.ast.Trees.Import

import scala.quoted._
object Macros {
sealed trait Nat
case object Z extends Nat
case class S[N <: Nat]() extends Nat

inline def isZero(inline n: Int): Boolean = ~{
if (n == 0) (true: Expr[Boolean])
else (false: Expr[Boolean])
}

}
7 changes: 7 additions & 0 deletions tests/run/quote-splice-interpret-1/Test_2.scala
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@@ -0,0 +1,7 @@
import Macros._
object Test {
def main(args: Array[String]): Unit = {
println(isZero(0))
println(isZero(1))
}
}