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, 31 insertions, 0 deletions

diff --git a/test/files/neg/t5702-neg-bad-xbrace.scala b/test/files/neg/t5702-neg-bad-xbrace.scala
new file mode 100644
index 0000000000..64bbdb18be
--- /dev/null
+++ b/test/files/neg/t5702-neg-bad-xbrace.scala
@@ -0,0 +1,31 @@
+
+object Test {
+  def main(args: Array[String]) {
+    /* PiS example, minus a brace
+    val yearMade = 1965
+    val old =
+      <a>{ if (yearMade < 2000) <old>yearMade}</old>
+           else xml.NodeSeq.Empty } </a>
+    println(old)
+    */
+
+    // bad brace or paren after _*
+    // actually, we know it's a bad paren...
+    // we skip it because not in a context looking for rparen
+    val xyear = <year>1965</year>
+    val ancient =
+      <b>{
+        val when = xyear match {
+          case <year>{_*)}</year> => y
+          case _ => "2035"
+        }
+        <old>{when}</old>
+      }</b>
+    println(ancient)
+
+    val xml = <top><a>apple</a><b>boy</b><c>child</c></top>
+    // bad brace or paren after _*
+    val <top>{a, z@_*)}</top> = xml
+    println("A for "+ a +", ending with "+ z)
+  }
+}