Turn off position checking for XML-generated blocks

Author: smarter

compiler/src/dotty/tools/dotc/ast/Positioned.scala

@@ -181,6 +181,8 @@ abstract class Positioned extends DotClass with Product {
         }
         if (nonOverlapping) {
           this match {
+            case _: XMLBlock =>
+              // FIXME: Trees generated by the XML parser do not satisfy `checkPos`
             case _: WildcardFunction
             if lastPositioned.isInstanceOf[ValDef] && !p.isInstanceOf[ValDef] =>
               // ignore transition from last wildcard parameter to body

compiler/src/dotty/tools/dotc/ast/untpd.scala

@@ -101,6 +101,10 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
    */
   class InfixOpBlock(leftOperand: Tree, rightOp: Tree) extends Block(leftOperand :: Nil, rightOp)
 
+  /** A block generated by the XML parser, only treated specially by
+   *  `Positioned#checkPos` */
+  class XMLBlock(stats: List[Tree], expr: Tree) extends Block(stats, expr)
+
   // ----- Modifiers -----------------------------------------------------
   /** Mod is intended to record syntactic information about modifiers, it's
     * NOT a replacement of FlagSet.

compiler/src/dotty/tools/dotc/parsing/SymbolicXMLBuilder.scala

@@ -258,6 +258,6 @@ class SymbolicXMLBuilder(parser: Parser, preserveWS: Boolean)(implicit ctx: Cont
       args
     )
 
-    atPos(pos.toSynthetic)( Block(nsResult, Block(attrResult, body)) )
+    atPos(pos.toSynthetic)(new XMLBlock(nsResult, new XMLBlock(attrResult, body)))
   }
 }

tests/pos/xml-pos.scala

@@ -0,0 +1,10 @@
+object Test {
+  val a =
+    <foo a="bla" n="foo" />
+
+  val b =
+    <foo xmlns:bar="baz" />
+
+  val c =
+    <a><c/></a>
+}