Handle macro annotation suspends and crashes

Author: nicolasstucki

compiler/src/dotty/tools/dotc/quoted/Interpreter.scala

@@ -268,19 +268,6 @@ class Interpreter(pos: SrcPos, classLoader: ClassLoader)(using Context):
         }
     }
 
-  private object MissingClassDefinedInCurrentRun {
-    def unapply(targetException: Throwable)(using Context): Option[Symbol] = {
-      targetException match
-        case _: NoClassDefFoundError | _: ClassNotFoundException =>
-          val className = targetException.getMessage
-          if className eq null then None
-          else
-            val sym = staticRef(className.toTypeName).symbol
-            if (sym.isDefinedInCurrentRun) Some(sym) else None
-        case _ => None
-    }
-  }
-
   /** List of classes of the parameters of the signature of `sym` */
   private def paramsSig(sym: Symbol): List[Class[?]] = {
     def paramClass(param: Type): Class[?] = {
@@ -364,3 +351,16 @@ object Interpreter:
       }
     }
   end Call
+
+  object MissingClassDefinedInCurrentRun {
+    def unapply(targetException: Throwable)(using Context): Option[Symbol] = {
+      targetException match
+        case _: NoClassDefFoundError | _: ClassNotFoundException =>
+          val className = targetException.getMessage
+          if className eq null then None
+          else
+            val sym = staticRef(className.toTypeName).symbol
+            if (sym.isDefinedInCurrentRun) Some(sym) else None
+        case _ => None
+    }
+  }

compiler/src/dotty/tools/dotc/transform/MacroAnnotations.scala

@@ -13,11 +13,15 @@ import dotty.tools.dotc.core.DenotTransformers.DenotTransformer
 import dotty.tools.dotc.core.Flags.*
 import dotty.tools.dotc.core.MacroClassLoader
 import dotty.tools.dotc.core.Symbols.*
+import dotty.tools.dotc.core.Types._
 import dotty.tools.dotc.quoted.*
 import dotty.tools.dotc.util.SrcPos
 import scala.quoted.runtime.impl.{QuotesImpl, SpliceScope}
 
 import scala.quoted.Quotes
+import scala.util.control.NonFatal
+
+import java.lang.reflect.InvocationTargetException
 
 class MacroAnnotations(thisPhase: DenotTransformer):
   import tpd.*
@@ -53,7 +57,33 @@ class MacroAnnotations(thisPhase: DenotTransformer):
           debug.println(i"Expanding macro annotation: ${annot}")
 
           // Interpret call to `new myAnnot(..).transform(using <Quotes>)(<tree>)`
-          val transformedTrees = callMacro(macroInterpreter, tree, annot)
+          val transformedTrees =
+            try callMacro(macroInterpreter, tree, annot)
+            catch
+              // TODO: Replace this case when scala.annaotaion.MacroAnnotation is no longer experimental and reflectiveSelectable is not used
+              //       Replace this case with the nested cases.
+              case ex0: InvocationTargetException =>
+                ex0.getCause match
+                  case ex: scala.quoted.runtime.StopMacroExpansion =>
+                    if !ctx.reporter.hasErrors then
+                      report.error("Macro expansion was aborted by the macro without any errors reported. Macros should issue errors to end-users to facilitate debugging when aborting a macro expansion.", annot.tree)
+                    List(tree)
+                  case Interpreter.MissingClassDefinedInCurrentRun(sym) if ctx.compilationUnit.isSuspendable =>
+                    if (ctx.settings.XprintSuspension.value)
+                      report.echo(i"suspension triggered by a dependency on $sym", annot.tree)
+                    ctx.compilationUnit.suspend() // this throws a SuspendException
+                  case NonFatal(ex) =>
+                    val stack0 = ex.getStackTrace.takeWhile(_.getClassName != "dotty.tools.dotc.transform.MacroAnnotations")
+                    val stack = stack0.take(1 + stack0.lastIndexWhere(_.getMethodName == "transform"))
+                    val msg =
+                      em"""Failed to evaluate macro.
+                          |  Caused by ${ex.getClass}: ${if (ex.getMessage == null) "" else ex.getMessage}
+                          |    ${stack.mkString("\n    ")}
+                          |"""
+                    report.error(msg, annot.tree)
+                    List(tree)
+                  case _ =>
+                    throw ex0
           transformedTrees.span(_.symbol != tree.symbol) match
             case (prefixed, newTree :: suffixed) =>
               allTrees ++= prefixed

tests/neg-macros/annot-crash.check

@@ -0,0 +1,8 @@
+
+-- Error: tests/neg-macros/annot-crash/Test_2.scala:1:0 ----------------------------------------------------------------
+1 |@crash // error
+  |^^^^^^
+  |Failed to evaluate macro.
+  |  Caused by class scala.NotImplementedError: an implementation is missing
+  |    scala.Predef$.$qmark$qmark$qmark(Predef.scala:344)
+  |    crash.transform(Macro_1.scala:7)

tests/neg-macros/annot-crash/Macro_1.scala

@@ -0,0 +1,8 @@
+import scala.annotation.{experimental, MacroAnnotation}
+import scala.quoted._
+
+@experimental
+class crash extends MacroAnnotation {
+  def transform(using Quotes)(tree: quotes.reflect.Definition): List[quotes.reflect.Definition] =
+    ???
+}

tests/neg-macros/annot-crash/Test_2.scala

@@ -0,0 +1,2 @@
+@crash // error
+def test = ()

tests/neg-macros/annot-suspend-cycle.check

@@ -0,0 +1,12 @@
+-- [E129] Potential Issue Warning: tests/neg-macros/annot-suspend-cycle/Macro.scala:7:4 --------------------------------
+7 |    new Foo
+  |    ^^^^^^^
+  |    A pure expression does nothing in statement position; you may be omitting necessary parentheses
+  |
+  | longer explanation available when compiling with `-explain`
+Cyclic macro dependencies in tests/neg-macros/annot-suspend-cycle/Test.scala.
+Compilation stopped since no further progress can be made.
+
+To fix this, place macros in one set of files and their callers in another.
+
+Compiling with  -Xprint-suspension   gives more information.

tests/neg-macros/annot-suspend-cycle/Macro.scala

@@ -0,0 +1,9 @@
+import scala.annotation.{experimental, MacroAnnotation}
+import scala.quoted._
+
+@experimental
+class cycle extends MacroAnnotation {
+  def transform(using Quotes)(tree: quotes.reflect.Definition): List[quotes.reflect.Definition] =
+    new Foo
+    List(tree)
+}

tests/neg-macros/annot-suspend-cycle/Test.scala

@@ -0,0 +1,5 @@
+// nopos-error
+class Foo
+
+@cycle
+def test = ()