3 files changed, 55 insertions, 25 deletions

diff --git a/src/main/scala/firrtl/Parser.scala b/src/main/scala/firrtl/Parser.scala
index b2d97e86..a4c366ec 100644
--- a/src/main/scala/firrtl/Parser.scala
+++ b/src/main/scala/firrtl/Parser.scala
@@ -10,6 +10,8 @@ import firrtl.parser.Listener
 import firrtl.Utils.time
 import firrtl.antlr.{FIRRTLParser, _}
 
+import scala.util.control.NonFatal
+
 class ParserException(message: String) extends FirrtlUserException(message)
 
 case class ParameterNotSpecifiedException(message: String) extends ParserException(message)
@@ -42,12 +44,25 @@ object Parser extends LazyLogging {
       parser.getInterpreter.setPredictionMode(PredictionMode.SLL)
       parser.addParseListener(listener)
 
-      // Concrete Syntax Tree
-      parser.circuit
+      // Syntax errors may violate assumptions in the Listener and Visitor.
+      // We need to handle these errors gracefully.
+      val throwable =
+        try {
+          parser.circuit
+          None
+        } catch {
+          case e: ParserException => throw e
+          case NonFatal(e) => Some(e)
+        }
 
       val numSyntaxErrors = parser.getNumberOfSyntaxErrors
       if (numSyntaxErrors > 0) throw new SyntaxErrorsException(s"$numSyntaxErrors syntax error(s) detected")
 
+      // Note that this should never happen because any throwables caught should be due to syntax
+      // errors that are reported above. This is just to ensure that we don't accidentally mask any
+      // bugs in the Parser, Listener, or Visitor.
+      if (throwable.nonEmpty) Utils.throwInternalError(exception = throwable)
+
       listener.getCircuit
     }
 
diff --git a/src/main/scala/firrtl/Utils.scala b/src/main/scala/firrtl/Utils.scala
index ec68d4eb..9e267a39 100644
--- a/src/main/scala/firrtl/Utils.scala
+++ b/src/main/scala/firrtl/Utils.scala
@@ -165,7 +165,7 @@ object Utils extends LazyLogging {
     * @param message - possible string to emit,
     * @param exception - possible exception triggering the error.
     */
-  def throwInternalError(message: String = "", exception: Option[Exception] = None) = {
+  def throwInternalError(message: String = "", exception: Option[Throwable] = None) = {
     // We'll get the first exception in the chain, keeping it intact.
     val first = true
     val throwable = getThrowable(exception, true)
diff --git a/src/test/scala/firrtlTests/ParserSpec.scala b/src/test/scala/firrtlTests/ParserSpec.scala
index bb7c2ab2..5003871d 100644
--- a/src/test/scala/firrtlTests/ParserSpec.scala
+++ b/src/test/scala/firrtlTests/ParserSpec.scala
@@ -129,29 +129,33 @@ class ParserSpec extends FirrtlFlatSpec {
     firrtl.Parser.parse(c.serialize)
   }
 
-  an[UnsupportedVersionException] should be thrownBy {
-    val input = """
-                  |FIRRTL version 1.2.0
-                  |circuit Test :
-                  |  module Test :
-                  |    input in : UInt<1>
-                  |    in <= UInt(0)
-      """.stripMargin
-    firrtl.Parser.parse(input)
+  "Version 1.2.0" should "be rejected" in {
+    an[UnsupportedVersionException] should be thrownBy {
+      val input = """
+                    |FIRRTL version 1.2.0
+                    |circuit Test :
+                    |  module Test :
+                    |    input in : UInt<1>
+                    |    in <= UInt(0)
+        """.stripMargin
+      firrtl.Parser.parse(input)
+    }
   }
 
-  an[UnsupportedVersionException] should be thrownBy {
-    val input = """
-                  |FIRRTL version 2.0.0
-                  |crcuit Test :
-                  |  module Test @@#!# :
-                  |    input in1 : UInt<2>
-                  |    input in2 : UInt<3>
-                  |    output out : UInt<4>
-                  |    out[1:0] <= in1
-                  |    out[3:2] <= in2[1:0]
-      """.stripMargin
-    firrtl.Parser.parse(input)
+  "Version 2.0.0" should "be rejected" in {
+    an[UnsupportedVersionException] should be thrownBy {
+      val input = """
+                    |FIRRTL version 2.0.0
+                    |crcuit Test :
+                    |  module Test @@#!# :
+                    |    input in1 : UInt<2>
+                    |    input in2 : UInt<3>
+                    |    output out : UInt<4>
+                    |    out[1:0] <= in1
+                    |    out[3:2] <= in2[1:0]
+        """.stripMargin
+      firrtl.Parser.parse(input)
+    }
   }
 
   // ********** Memories **********
@@ -379,7 +383,7 @@ class ParserSpec extends FirrtlFlatSpec {
     }
   }
 
-  it should "be able to parse a MultiInfo as a FileInfo" in {
+  "The Parser" should "be able to parse a MultiInfo as a FileInfo" in {
     // currently MultiInfo gets flattened into a single string which can only be recovered as a FileInfo
     val info = ir.MultiInfo(Seq(ir.MultiInfo(Seq(ir.FileInfo("a"))), ir.FileInfo("b"), ir.FileInfo("c")))
     val input =
@@ -390,6 +394,17 @@ class ParserSpec extends FirrtlFlatSpec {
     val c = firrtl.Parser.parse(input)
     assert(c.info == ir.FileInfo("a b c"))
   }
+
+  it should "handle parse errors gracefully" in {
+    val input =
+      s"""circuit test :
+         |  module test :
+         |    output out :
+         |""".stripMargin
+    a[SyntaxErrorsException] should be thrownBy {
+      firrtl.Parser.parse(input)
+    }
+  }
 }
 
 class ParserPropSpec extends FirrtlPropSpec {