Move compiler and compiler tests to compiler dir

1 files changed, 99 insertions, 0 deletions

diff --git a/compiler/src/dotty/tools/dotc/transform/TryCatchPatterns.scala b/compiler/src/dotty/tools/dotc/transform/TryCatchPatterns.scala
new file mode 100644
index 000000000..9a6ecef51
--- /dev/null
+++ b/compiler/src/dotty/tools/dotc/transform/TryCatchPatterns.scala
@@ -0,0 +1,99 @@
+package dotty.tools.dotc
+package transform
+
+import core.Symbols._
+import core.StdNames._
+import ast.Trees._
+import core.Types._
+import dotty.tools.dotc.core.Decorators._
+import dotty.tools.dotc.core.Flags
+import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.transform.TreeTransforms.{MiniPhaseTransform, TransformerInfo}
+import dotty.tools.dotc.util.Positions.Position
+
+/** Compiles the cases that can not be handled by primitive catch cases as a common pattern match.
+ *
+ *  The following code:
+ *    ```
+ *    try { <code> }
+ *    catch {
+ *      <tryCases> // Cases that can be handled by catch
+ *      <patternMatchCases> // Cases starting with first one that can't be handled by catch
+ *    }
+ *    ```
+ *  will become:
+ *    ```
+ *    try { <code> }
+ *    catch {
+ *      <tryCases>
+ *      case e => e match {
+ *        <patternMatchCases>
+ *      }
+ *    }
+ *    ```
+ *
+ *  Cases that are not supported include:
+ *   - Applies and unapplies
+ *   - Idents
+ *   - Alternatives
+ *   - `case _: T =>` where `T` is not `Throwable`
+ *
+ */
+class TryCatchPatterns extends MiniPhaseTransform {
+  import dotty.tools.dotc.ast.tpd._
+
+  def phaseName: String = "tryCatchPatterns"
+
+  override def runsAfter = Set(classOf[ElimRepeated])
+
+  override def checkPostCondition(tree: Tree)(implicit ctx: Context): Unit = tree match {
+    case Try(_, cases, _) =>
+      cases.foreach {
+        case CaseDef(Typed(_, _), guard, _) => assert(guard.isEmpty, "Try case should not contain a guard.")
+        case CaseDef(Bind(_, _), guard, _) => assert(guard.isEmpty, "Try case should not contain a guard.")
+        case c =>
+          assert(isDefaultCase(c), "Pattern in Try should be Bind, Typed or default case.")
+      }
+    case _ =>
+  }
+
+  override def transformTry(tree: Try)(implicit ctx: Context, info: TransformerInfo): Tree = {
+    val (tryCases, patternMatchCases) = tree.cases.span(isCatchCase)
+    val fallbackCase = mkFallbackPatterMatchCase(patternMatchCases, tree.pos)
+    cpy.Try(tree)(cases = tryCases ++ fallbackCase)
+  }
+
+  /** Is this pattern node a catch-all or type-test pattern? */
+  private def isCatchCase(cdef: CaseDef)(implicit ctx: Context): Boolean = cdef match {
+    case CaseDef(Typed(Ident(nme.WILDCARD), tpt), EmptyTree, _)          => isSimpleThrowable(tpt.tpe)
+    case CaseDef(Bind(_, Typed(Ident(nme.WILDCARD), tpt)), EmptyTree, _) => isSimpleThrowable(tpt.tpe)
+    case _                                                               => isDefaultCase(cdef)
+  }
+
+  private def isSimpleThrowable(tp: Type)(implicit ctx: Context): Boolean = tp match {
+    case tp @ TypeRef(pre, _) =>
+      (pre == NoPrefix || pre.widen.typeSymbol.isStatic) && // Does not require outer class check
+      !tp.symbol.is(Flags.Trait) && // Traits not supported by JVM
+      tp.derivesFrom(defn.ThrowableClass)
+    case _ =>
+      false
+  }
+
+  private def mkFallbackPatterMatchCase(patternMatchCases: List[CaseDef], pos: Position)(
+      implicit ctx: Context, info: TransformerInfo): Option[CaseDef] = {
+    if (patternMatchCases.isEmpty) None
+    else {
+      val exName = ctx.freshName("ex").toTermName
+      val fallbackSelector =
+        ctx.newSymbol(ctx.owner, exName, Flags.Synthetic | Flags.Case, defn.ThrowableType, coord = pos)
+      val sel = Ident(fallbackSelector.termRef).withPos(pos)
+      val rethrow = CaseDef(EmptyTree, EmptyTree, Throw(ref(fallbackSelector)))
+      Some(CaseDef(
+          Bind(fallbackSelector, Underscore(fallbackSelector.info).withPos(pos)),
+          EmptyTree,
+          transformFollowing(Match(sel, patternMatchCases ::: rethrow :: Nil)))
+      )
+    }
+  }
+
+}