Merge pull request #4101 from dotty-staging/quote-error-reporting

Add error reporter for inlined quotes

Author: nicolasstucki

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

@@ -336,7 +336,7 @@ class ReifyQuotes extends MacroTransformWithImplicits {
             }
 
             val tree1 =
-              if (level == 0) cpy.Inlined(tree)(call, stagedBindings, Splicer.splice(seq(splicedBindings, body)))
+              if (level == 0) cpy.Inlined(tree)(call, stagedBindings, Splicer.splice(seq(splicedBindings, body).withPos(tree.pos)))
               else seq(stagedBindings, cpy.Select(expansion)(cpy.Inlined(tree)(call, splicedBindings, body), name))
             val tree2 = transform(tree1)
 

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

@@ -3,9 +3,14 @@ package transform
 
 import dotty.tools.dotc.ast.tpd
 import dotty.tools.dotc.core.Contexts._
+import dotty.tools.dotc.core.Decorators._
 import dotty.tools.dotc.core.quoted._
 import dotty.tools.dotc.interpreter._
 
+import scala.util.control.NonFatal
+
+import java.lang.reflect.InvocationTargetException
+
 /** Utility class to splice quoted expressions */
 object Splicer {
   import tpd._
@@ -22,7 +27,22 @@ object Splicer {
   /** Splice the Tree for a Quoted expression which is constructed via a reflective call to the given method */
   private def reflectiveSplice(tree: Tree)(implicit ctx: Context): Tree = {
     val interpreter = new Interpreter
-    interpreter.interpretTree[scala.quoted.Expr[_]](tree).map(PickledQuotes.quotedExprToTree).getOrElse(tree)
+    val interpreted =
+      try interpreter.interpretTree[scala.quoted.Expr[_]](tree)
+      catch { case ex: InvocationTargetException => handleTargetException(tree, ex); None }
+    interpreted.fold(tree)(PickledQuotes.quotedExprToTree)
+  }
+
+  private def handleTargetException(tree: Tree, ex: InvocationTargetException)(implicit ctx: Context): Unit = ex.getCause match {
+    case ex: scala.quoted.QuoteError => ctx.error(ex.getMessage, tree.pos)
+    case NonFatal(ex) =>
+      val msg =
+        s"""Failed to evaluate inlined quote.
+           |  Caused by: ${ex.getMessage}
+           |  ${ex.getStackTrace.takeWhile(_.getClassName != "sun.reflect.NativeMethodAccessorImpl").mkString("\n  ")}
+         """.stripMargin
+      ctx.error(msg, tree.pos)
+    case _ => throw ex
   }
 
 }

library/src/scala/quoted/QuoteError.scala

@@ -0,0 +1,11 @@
+package scala.quoted
+
+/** Throwing this error in the implementation of an inline macro
+ *  will result in a compilation error with the given message.
+ */
+class QuoteError(message: String) extends Throwable(message)
+
+object QuoteError {
+  /** Throws a QuoteError with the given message */
+  def apply(message: => String): Nothing = throw new QuoteError(message)
+}

tests/neg/quote-error/Macro_1.scala

@@ -0,0 +1,8 @@
+import quoted._
+
+object Macro_1 {
+  inline def foo(inline b: Boolean): Unit = ~fooImpl(b)
+  def fooImpl(b: Boolean): Expr[Unit] =
+    if (b) '(println("foo(true)"))
+    else QuoteError("foo cannot be called with false")
+}

tests/neg/quote-error/Test_2.scala

@@ -0,0 +1,6 @@
+import Macro_1._
+
+object Test_2 {
+  foo(true)
+  foo(false) // error: foo cannot be called with false
+}

tests/neg/quote-exception/Macro_1.scala

@@ -0,0 +1,8 @@
+import quoted._
+
+object Macro_1 {
+  inline def foo(inline b: Boolean): Unit = ~fooImpl(b)
+  def fooImpl(b: Boolean): Expr[Unit] =
+    if (b) '(println("foo(true)"))
+  else ???
+}

tests/neg/quote-exception/Test_2.scala

@@ -0,0 +1,6 @@
+import Macro_1._
+
+object Test_2 {
+  foo(true)
+  foo(false) // error: Failed to evaluate inlined quote. Caused by: an implementation is missing
+}