Merge pull request #912 from seldridge/c911

Make BaseModule.name lazy

2 files changed, 27 insertions, 1 deletions

diff --git a/chiselFrontend/src/main/scala/chisel3/core/Module.scala b/chiselFrontend/src/main/scala/chisel3/core/Module.scala
index 88013bae..3bdc86d6 100644
--- a/chiselFrontend/src/main/scala/chisel3/core/Module.scala
+++ b/chiselFrontend/src/main/scala/chisel3/core/Module.scala
@@ -180,7 +180,13 @@ abstract class BaseModule extends HasId {
   def desiredName = this.getClass.getName.split('.').last
 
   /** Legalized name of this module. */
-  final val name = Builder.globalNamespace.name(desiredName)
+  final lazy val name = try {
+    Builder.globalNamespace.name(desiredName)
+  } catch {
+    case e: NullPointerException => throwException(
+      s"Error: desiredName of ${this.getClass.getName} is null. Did you evaluate 'name' before all values needed by desiredName were available?", e)
+    case t: Throwable => throw t
+  }
 
   /** Returns a FIRRTL ModuleName that references this object
     * @note Should not be called until circuit elaboration is complete
diff --git a/src/test/scala/chiselTests/Module.scala b/src/test/scala/chiselTests/Module.scala
index 968e7578..b3d1899c 100644
--- a/src/test/scala/chiselTests/Module.scala
+++ b/src/test/scala/chiselTests/Module.scala
@@ -62,6 +62,19 @@ class ModuleRewrap extends Module {
   val inst2 = Module(inst)
 }
 
+class ModuleWrapper(gen: => Module) extends Module {
+  val io = IO(new Bundle{})
+  val child = Module(gen)
+  override val desiredName = s"${child.desiredName}Wrapper"
+}
+
+class NullModuleWrapper extends Module {
+  val io = IO(new Bundle{})
+  override lazy val desiredName = s"${child.desiredName}Wrapper"
+  println(s"My name is ${name}")
+  val child = Module(new ModuleWire)
+}
+
 class ModuleSpec extends ChiselPropSpec {
 
   property("ModuleVec should elaborate") {
@@ -138,4 +151,11 @@ class ModuleSpec extends ChiselPropSpec {
           "a" -> m.a, "b" -> m.b))
     })
   }
+  property("A desiredName parameterized by a submodule should work") {
+    Driver.elaborate(() => new ModuleWrapper(new ModuleWire)).name should be ("ModuleWireWrapper")
+  }
+  property("A name generating a null pointer exception should provide a good error message") {
+    (the [Exception] thrownBy (Driver.elaborate(() => new NullModuleWrapper)))
+      .getMessage should include ("desiredName of chiselTests.NullModuleWrapper is null")
+  }
 }