Allow space tab mismatch when rewritting to indent

Author: adpi2

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

@@ -817,8 +817,10 @@ object Parsers {
         if enclosingIndent < in.currentRegion.indentWidth then
           in.currentRegion.indentWidth
         else if
-          in.token == CASE &&
-          in.currentRegion.indentWidth == in.currentRegion.enclosing.indentWidth
+          in.token == CASE && (
+            in.currentRegion.enclosing == null ||
+            in.currentRegion.indentWidth == in.currentRegion.enclosing.indentWidth
+          )
         then enclosingIndent
         else enclosingIndent.increment
       try body

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

@@ -643,7 +643,8 @@ object Scanners {
             currentRegion.knownWidth = nextWidth
         else if (lastWidth != nextWidth)
           val lw = lastWidth
-          errorButContinue(spaceTabMismatchMsg(lw, nextWidth))
+          val msg = spaceTabMismatchMsg(lw, nextWidth)
+          if rewriteToIndent then report.warning(msg) else errorButContinue(msg)
       if token != OUTDENT then
         handleNewIndentWidth(currentRegion, _.otherIndentWidths += nextWidth)
       if next.token == EMPTY then