Fix scala#4393 WIP

Min tests: `try { ??? } catch {}` (can be scripted) and `try { ??? } catch {`.

Author: Blaisorblade

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

@@ -245,8 +245,8 @@ object Parsers {
       ctx.deprecationWarning(msg, source atPos Position(offset))
 
     /** Issue an error at current offset taht input is incomplete */
-    def incompleteInputError(msg: => Message) =
-      ctx.incompleteInputError(msg, source atPos Position(in.offset))
+    def incompleteInputError(msg: => Message, pos: Position = Position(in.offset)) =
+      ctx.incompleteInputError(msg, source atPos pos)
 
     /** If at end of file, issue an incompleteInputError.
      *  Otherwise issue a syntax error and skip to next safe point.
@@ -1162,7 +1162,10 @@ object Parsers {
             if (in.token == CATCH) {
               val pos = in.offset
               in.nextToken()
-              (expr(), pos)
+              accept(LBRACE)
+              val res = (expr(), pos)
+              accept(RBRACE)
+              res
             } else (EmptyTree, -1)
 
           handler match {