Improve error position and drop second error since it is pruned

Author: b-studios

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

@@ -540,7 +540,7 @@ object Parsers {
       def handleThis(qual: Ident) = {
         in.nextToken()
         val t = atPos(start) { This(qual) }
-        if (!thisOK && in.token != DOT) syntaxError(DanglingThisInPath(), start)
+        if (!thisOK && in.token != DOT) syntaxError(DanglingThisInPath(), t.pos)
         dotSelectors(t, finish)
       }
       def handleSuper(qual: Ident) = {

tests/neg/i1845.scala

@@ -1,3 +1,3 @@
 object Test {
   type X = FooBar22.this // error
-} // error
+}