SI-5702 Pattern parser halts on star

In patterns, the parser halts when it sees stars.
This means it does not handle infix notation for a case class
named "*".  This patch uses lookahead to decide whether to parse
'_' '*' as a sequence pattern or as the start of infix.
(For both normal and error cases, the tokens are always consumed
immediately.) Error messages are improved for _* (as a help to learners)
and slightly improved recovery helps the parse continue.
The entry point for XML patterns is now distinct; otherwise,
the change is local to pattern3-simplepattern; the entry point
for simplepattern() is unchanged because it is commented
"hook for IDE."

1 files changed, 17 insertions, 0 deletions

diff --git a/test/files/neg/t5702-neg-bad-brace.scala b/test/files/neg/t5702-neg-bad-brace.scala
new file mode 100644
index 0000000000..16a341cf8c
--- /dev/null
+++ b/test/files/neg/t5702-neg-bad-brace.scala
@@ -0,0 +1,17 @@
+
+object Test {
+
+  def main(args: Array[String]) {
+    val is = List(1,2,3)
+
+    is match {
+// the erroneous brace is ignored, so we can't halt on it.
+// maybe brace healing can detect overlapping unmatched (...}
+// In this case, the fix emits an extra error:
+// t5702-neg-bad-brace.scala:10: error: Unmatched closing brace '}' ignored here
+// t5702-neg-bad-brace.scala:10: error: illegal start of simple pattern (i.e., =>)
+// t5702-neg-bad-brace.scala:11: error: ')' expected but '}' found.
+      case List(1, _*} =>
+    }
+  }
+}