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, 15 insertions, 0 deletions

diff --git a/test/files/pos/t5702-pos-infix-star.scala b/test/files/pos/t5702-pos-infix-star.scala
new file mode 100644
index 0000000000..756bcdd8de
--- /dev/null
+++ b/test/files/pos/t5702-pos-infix-star.scala
@@ -0,0 +1,15 @@
+
+object Test {
+  case class *(a: Int, b: Int)
+  type Star = *
+  case class P(a: Int, b: Star) // alias still required
+
+  def main(args: Array[String]) {
+    val v = new *(6,7)
+    val x * y = v
+    printf("%d,%d\n",x,y)
+    val p = P(5, v)
+    val P(a, b * c) = p
+    printf("%d,%d,%d\n",a,b,c)
+  }
+}