unapp: Fix Span/Coord when creating patbound symbols

In a modified version of maximizeType I ended up with picking test
failures, and this seems to be the right position.

Author: dwijnand

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -1354,7 +1354,7 @@ trait Applications extends Compatibility {
             // Constraining only fails if the pattern cannot possibly match,
             // but useless pattern checks detect more such cases, so we simply rely on them instead.
             withMode(Mode.GadtConstraintInference)(TypeComparer.constrainPatternType(unapplyArgType, selType))
-            val patternBound = maximizeType(unapplyArgType, tree.span)
+            val patternBound = maximizeType(unapplyArgType, unapplyFn.span.endPos)
             if (patternBound.nonEmpty) unapplyFn = addBinders(unapplyFn, patternBound)
             unapp.println(i"case 2 $unapplyArgType ${ctx.typerState.constraint}")
             unapplyArgType