Merge pull request #4479 from dotty-staging/fix-QuoteError-in-splices

Handle QuotedError when evaluating holes in quotes

Author: nicolasstucki

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

@@ -36,7 +36,11 @@ object Splicer {
       val liftedArgs = getLiftedArgs(call, bindings)
       val interpreter = new Interpreter(pos, classLoader)
       val interpreted = interpreter.interpretCallToSymbol[Seq[Any] => Object](call.symbol)
-      interpreted.flatMap(lambda => evaluateLambda(lambda, liftedArgs, pos)).fold(tree)(PickledQuotes.quotedExprToTree)
+      evaluateMacro(pos) {
+        // Some parts of the macro are evaluated during the unpickling performed in quotedExprToTree
+        val evaluated = interpreted.map(lambda => lambda(liftedArgs).asInstanceOf[scala.quoted.Expr[Nothing]])
+        evaluated.fold(tree)(PickledQuotes.quotedExprToTree)
+      }
   }
 
   /** Given the inline code and bindings, compute the lifted arguments that will be used to execute the macro
@@ -73,20 +77,21 @@ object Splicer {
     liftArgs(call.symbol.info, allArgs(call, Nil))
   }
 
-  private def evaluateLambda(lambda: Seq[Any] => Object, args: Seq[Any], pos: Position)(implicit ctx: Context): Option[scala.quoted.Expr[Nothing]] = {
-    try Some(lambda(args).asInstanceOf[scala.quoted.Expr[Nothing]])
+  /* Evaluate the code in the macro and handle exceptions durring evaluation */
+  private def evaluateMacro(pos: Position)(code: => Tree)(implicit ctx: Context): Tree = {
+    try code
     catch {
       case ex: scala.quoted.QuoteError =>
         ctx.error(ex.getMessage, pos)
-        None
+        EmptyTree
       case NonFatal(ex) =>
         val msg =
           s"""Failed to evaluate inlined quote.
-             |  Caused by: ${ex.getMessage}
-             |  ${ex.getStackTrace.takeWhile(_.getClassName != "dotty.tools.dotc.transform.Splicer$").init.mkString("\n  ")}
+             |  Caused by ${ex.getClass}: ${if (ex.getMessage == null) "" else ex.getMessage}
+             |    ${ex.getStackTrace.takeWhile(_.getClassName != "dotty.tools.dotc.transform.Splicer$").init.mkString("\n    ")}
          """.stripMargin
         ctx.error(msg, pos)
-        None
+        EmptyTree
     }
   }
 

tests/neg/quote-error-2/Macro_1.scala

@@ -0,0 +1,12 @@
+import quoted._
+
+object Macro_1 {
+  inline def foo(inline b: Boolean): Unit = ~fooImpl(b)
+  def fooImpl(b: Boolean): Expr[Unit] =
+    '(println(~msg(b)))
+
+  def msg(b: Boolean): Expr[String] =
+    if (b) '("foo(true)")
+    else QuoteError("foo cannot be called with false")
+
+}

tests/neg/quote-error-2/Test_2.scala

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