Fix for parser regression allowing 0-case match...

Fix for parser regression allowing 0-case match blocks. Closes #4217, no
review.

3 files changed, 13 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
index 21628f9864..d75d28c45f 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
@@ -1542,8 +1542,12 @@ self =>
    /** CaseClauses ::= CaseClause {CaseClause}
     *   CaseClause ::= case Pattern [Guard] `=>' Block
     */
-    def caseClauses(): List[CaseDef] = caseSeparated {
-      atPos(in.offset)(makeCaseDef(pattern(), guard(), caseBlock()))
+    def caseClauses(): List[CaseDef] = {
+      val cases = caseSeparated { atPos(in.offset)(makeCaseDef(pattern(), guard(), caseBlock())) }
+      if (cases.isEmpty)  // trigger error if there are no cases
+        accept(CASE)
+
+      cases
     }
 
     // IDE HOOK (so we can memoize case blocks) // needed?
diff --git a/test/files/neg/bug4217.check b/test/files/neg/bug4217.check
new file mode 100644
index 0000000000..4de9201da8
--- /dev/null
+++ b/test/files/neg/bug4217.check
@@ -0,0 +1,4 @@
+bug4217.scala:2: error: 'case' expected but '}' found.
+  42 match { } 
+             ^
+one error found
diff --git a/test/files/neg/bug4217.scala b/test/files/neg/bug4217.scala
new file mode 100644
index 0000000000..8b5c4a6e05
--- /dev/null
+++ b/test/files/neg/bug4217.scala
@@ -0,0 +1,3 @@
+object A extends Application {
+  42 match { }
+}