Check for module name conflicts

* Fixes #1436

2 files changed, 32 insertions, 0 deletions

diff --git a/src/main/scala/firrtl/passes/Checks.scala b/src/main/scala/firrtl/passes/Checks.scala
index e176bcc4..8717ffec 100644
--- a/src/main/scala/firrtl/passes/Checks.scala
+++ b/src/main/scala/firrtl/passes/Checks.scala
@@ -33,6 +33,8 @@ trait CheckHighFormLike { this: Pass =>
     s"$info: [module $mname] Register $name cannot be a bundle type with flips.")
   class InvalidAccessException(info: Info, mname: String) extends PassException(
     s"$info: [module $mname] Invalid access to non-reference.")
+  class ModuleNameNotUniqueException(info: Info, mname: String) extends PassException(
+    s"$info: Repeat definition of module $mname")
   class ModuleNotDefinedException(info: Info, mname: String, name: String) extends PassException(
     s"$info: Module $name is not defined.")
   class IncorrectNumArgsException(info: Info, mname: String, op: String, n: Int) extends PassException(
@@ -73,6 +75,10 @@ trait CheckHighFormLike { this: Pass =>
     val moduleGraph = new ModuleGraph
     val moduleNames = (c.modules map (_.name)).toSet
 
+    c.modules.view.groupBy(_.name).filter(_._2.length > 1).flatMap(_._2).foreach {
+      m => errors.append(new ModuleNameNotUniqueException(m.info, m.name))
+    }
+
     def checkHighFormPrimop(info: Info, mname: String, e: DoPrim): Unit = {
       def correctNum(ne: Option[Int], nc: Int): Unit = {
         ne match {
diff --git a/src/test/scala/firrtlTests/CheckSpec.scala b/src/test/scala/firrtlTests/CheckSpec.scala
index 9a384d21..f03b6611 100644
--- a/src/test/scala/firrtlTests/CheckSpec.scala
+++ b/src/test/scala/firrtlTests/CheckSpec.scala
@@ -307,6 +307,32 @@ class CheckSpec extends FlatSpec with Matchers {
       }
     }
   }
+
+  s"Duplicate module names" should "throw an exception" in {
+    val input =
+      s"""|circuit bar :
+          |  module bar :
+          |    input i : UInt<8>
+          |    output o : UInt<8>
+          |    o <= i
+          |  module dup :
+          |    input i : UInt<8>
+          |    output o : UInt<8>
+          |    o <= i
+          |  module dup :
+          |    input i : UInt<8>
+          |    output o : UInt<8>
+          |    o <= not(i)
+          |""".stripMargin
+    assertThrows[CheckHighForm.ModuleNameNotUniqueException] {
+      try {
+        checkHighInput(input)
+      } catch {
+        case e: firrtl.passes.PassExceptions => throw e.exceptions.head
+      }
+    }
+  }
+
 }
 
 object CheckSpec {