diff --git a/chiselFrontend/src/main/scala/chisel3/core/Module.scala b/chiselFrontend/src/main/scala/chisel3/core/Module.scala index 89dd2dee643..3bdc86d6f15 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 lazy val name = Builder.globalNamespace.name(desiredName) + final lazy val name = try { + Builder.globalNamespace.name(desiredName) + } catch { + case e: NullPointerException => throwException( + s"Error: desiredName of ${this.getClass.getName} is null. Did you evaluate 'name' before all values needed by desiredName were available?", e) + case t: Throwable => throw t + } /** Returns a FIRRTL ModuleName that references this object * @note Should not be called until circuit elaboration is complete diff --git a/src/test/scala/chiselTests/Module.scala b/src/test/scala/chiselTests/Module.scala index dc44838a287..b3d1899cf0d 100644 --- a/src/test/scala/chiselTests/Module.scala +++ b/src/test/scala/chiselTests/Module.scala @@ -65,7 +65,14 @@ class ModuleRewrap extends Module { class ModuleWrapper(gen: => Module) extends Module { val io = IO(new Bundle{}) val child = Module(gen) + override val desiredName = s"${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 { @@ -147,4 +154,8 @@ class ModuleSpec extends ChiselPropSpec { 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") + } }