chipsalliance/chisel

Bad error reporting on wrong (subword) assignments

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#1,465 opened on Jun 6, 2020

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good first issue

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Description

Type of issue: other enhancement

Impact: no functional change

Development Phase: request

Other information This is more a meta-issue mostly related to the beginners user experience. I think most of these issues are not done by more experienced devs.

If the current behavior is a bug, please provide the steps to reproduce the problem:

  1. Start with chisel-template (commit 11f6ca470120908d167cb8dc3241953eb31d0acb was used for this experiment)
  2. Create a new file in src/main/scala/gcd/Bug.scala (see content below)
  3. Run sbt "runMain gcd.BugDriver" to reproduce the output.
  4. See how the error reporting explain (or does not explain) the bad assignment.

What is the current behavior?

These are examples where the error reporting is (IMHO) bad / misleading.

Wrong transfer direction:

package gcd

import chisel3._
import chisel3.stage.{ChiselGeneratorAnnotation, ChiselStage}

class BugModule extends Module {
  val io = IO(new Bundle {
    val in  = Input(UInt(16.W))
    val out = Output(UInt(16.W))
  })

  io.in := io.out
}


object BugDriver extends App {
  (new ChiselStage).execute(args, Seq(ChiselGeneratorAnnotation(() => new BugModule)))
}

[info] Loading settings for project chisel_bad_error-build from plugins.sbt ...
[info] Loading project definition from /home/tom/src/bugs/chisel_bad_error/project
[info] Loading settings for project chisel_bad_error from build.sbt ...
[info] Set current project to chisel-module-template (in build file:/home/tom/src/bugs/chisel_bad_error/)
[info] Compiling 1 Scala source to /home/tom/src/bugs/chisel_bad_error/target/scala-2.12/classes ...
[warn] there were two feature warnings; re-run with -feature for details
[warn] one warning found
[info] Done compiling.
[info] running gcd.BugDriver 
[info] [0.002] Elaborating design...
[error] chisel3.internal.ChiselException: Connection between sink (UInt<16>(IO in unelaborated BugModule)) and source (UInt<16>(IO in unelaborated BugModule)) failed @: Sink is unwriteable by current module.
[error] 	...
[error] 	at gcd.BugModule.<init>(Bug.scala:14)
[error] 	at gcd.BugDriver$.$anonfun$new$1(Bug.scala:19)
[error] 	... (Stack trace trimmed to user code only, rerun with --full-stacktrace if you wish to see the full stack trace)
[error] (run-main-0) firrtl.options.StageError: 
[error] firrtl.options.StageError: 
[error] 	at chisel3.stage.ChiselStage.run(ChiselStage.scala:49)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Stage.$anonfun$transform$5(Stage.scala:46)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.Stage.$anonfun$transform$3(Stage.scala:46)
[error] 	at logger.Logger$.$anonfun$makeScope$2(Logger.scala:168)
[error] 	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:62)
[error] 	at logger.Logger$.makeScope(Logger.scala:166)
[error] 	at firrtl.options.Stage.transform(Stage.scala:46)
[error] 	at firrtl.options.Stage.execute(Stage.scala:57)
[error] 	at gcd.BugDriver$.delayedEndpoint$gcd$BugDriver$1(Bug.scala:19)
[error] 	at gcd.BugDriver$delayedInit$body.apply(Bug.scala:18)
[error] 	at scala.Function0.apply$mcV$sp(Function0.scala:39)
[error] 	at scala.Function0.apply$mcV$sp$(Function0.scala:39)
[error] 	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:17)
[error] 	at scala.App.$anonfun$main$1$adapted(App.scala:80)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.App.main(App.scala:80)
[error] 	at scala.App.main$(App.scala:78)
[error] 	at gcd.BugDriver$.main(Bug.scala:18)
[error] 	at gcd.BugDriver.main(Bug.scala)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.lang.reflect.Method.invoke(Method.java:498)
[error] Caused by: chisel3.internal.ChiselException: Connection between sink (UInt<16>(IO in unelaborated BugModule)) and source (UInt<16>(IO in unelaborated BugModule)) failed @: Sink is unwriteable by current module.
[error] 	at chisel3.internal.throwException$.apply(Error.scala:85)
[error] 	at chisel3.Data.connect(Data.scala:406)
[error] 	at chisel3.Data.$colon$eq(Data.scala:494)
[error] 	at gcd.BugModule.<init>(Bug.scala:14)
[error] 	at gcd.BugDriver$.$anonfun$new$1(Bug.scala:19)
[error] 	at chisel3.Module$.do_apply(Module.scala:52)
[error] 	at chisel3.stage.ChiselGeneratorAnnotation.$anonfun$elaborate$1(ChiselAnnotations.scala:50)
[error] 	at chisel3.internal.Builder$.$anonfun$build$1(Builder.scala:408)
[error] 	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:62)
[error] 	at chisel3.internal.Builder$.build(Builder.scala:406)
[error] 	at chisel3.stage.ChiselGeneratorAnnotation.elaborate(ChiselAnnotations.scala:50)
[error] 	at chisel3.stage.phases.Elaborate.$anonfun$transform$1(Elaborate.scala:19)
[error] 	at scala.collection.TraversableLike.$anonfun$flatMap$1(TraversableLike.scala:245)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.collection.TraversableLike.flatMap(TraversableLike.scala:245)
[error] 	at scala.collection.TraversableLike.flatMap$(TraversableLike.scala:242)
[error] 	at scala.collection.immutable.List.flatMap(List.scala:355)
[error] 	at chisel3.stage.phases.Elaborate.transform(Elaborate.scala:18)
[error] 	at chisel3.stage.phases.Elaborate.transform(Elaborate.scala:16)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.DependencyManager.$anonfun$transform$3(DependencyManager.scala:262)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.DependencyManager.transform(DependencyManager.scala:255)
[error] 	at firrtl.options.DependencyManager.transform$(DependencyManager.scala:240)
[error] 	at firrtl.options.PhaseManager.transform(DependencyManager.scala:419)
[error] 	at chisel3.stage.ChiselStage.run(ChiselStage.scala:35)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Stage.$anonfun$transform$5(Stage.scala:46)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.Stage.$anonfun$transform$3(Stage.scala:46)
[error] 	at logger.Logger$.$anonfun$makeScope$2(Logger.scala:168)
[error] 	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:62)
[error] 	at logger.Logger$.makeScope(Logger.scala:166)
[error] 	at firrtl.options.Stage.transform(Stage.scala:46)
[error] 	at firrtl.options.Stage.execute(Stage.scala:57)
[error] 	at gcd.BugDriver$.delayedEndpoint$gcd$BugDriver$1(Bug.scala:19)
[error] 	at gcd.BugDriver$delayedInit$body.apply(Bug.scala:18)
[error] 	at scala.Function0.apply$mcV$sp(Function0.scala:39)
[error] 	at scala.Function0.apply$mcV$sp$(Function0.scala:39)
[error] 	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:17)
[error] 	at scala.App.$anonfun$main$1$adapted(App.scala:80)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.App.main(App.scala:80)
[error] 	at scala.App.main$(App.scala:78)
[error] 	at gcd.BugDriver$.main(Bug.scala:18)
[error] 	at gcd.BugDriver.main(Bug.scala)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.lang.reflect.Method.invoke(Method.java:498)
[error] stack trace is suppressed; run 'last Compile / bgRunMain' for the full output
[error] Nonzero exit code: 1
[error] (Compile / runMain) Nonzero exit code: 1
[error] Total time: 8 s, completed Jun 6, 2020 1:59:07 PM

Flipped bounds:

package gcd

import chisel3._
import chisel3.stage.{ChiselGeneratorAnnotation, ChiselStage}

class BugModule extends Module {
  val io = IO(new Bundle {
    val in  = Input(UInt(16.W))
    val out = Output(UInt(16.W))
  })

  io.out := io.in(0, 15)
}


object BugDriver extends App {
  (new ChiselStage).execute(args, Seq(ChiselGeneratorAnnotation(() => new BugModule)))
}

[info] Loading settings for project chisel_bad_error-build from plugins.sbt ...
[info] Loading project definition from /home/tom/src/bugs/chisel_bad_error/project
[info] Loading settings for project chisel_bad_error from build.sbt ...
[info] Set current project to chisel-module-template (in build file:/home/tom/src/bugs/chisel_bad_error/)
[info] running gcd.BugDriver 
[info] [0.002] Elaborating design...
[error] java.lang.IllegalArgumentException: requirement failed
[error] 	...
[error] 	at gcd.BugModule.<init>(Bug.scala:14)
[error] 	at gcd.BugDriver$.$anonfun$new$1(Bug.scala:19)
[error] 	... (Stack trace trimmed to user code only, rerun with --full-stacktrace if you wish to see the full stack trace)
[error] (run-main-0) firrtl.options.StageError: 
[error] firrtl.options.StageError: 
[error] 	at chisel3.stage.ChiselStage.run(ChiselStage.scala:49)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Stage.$anonfun$transform$5(Stage.scala:46)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.Stage.$anonfun$transform$3(Stage.scala:46)
[error] 	at logger.Logger$.$anonfun$makeScope$2(Logger.scala:168)
[error] 	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:62)
[error] 	at logger.Logger$.makeScope(Logger.scala:166)
[error] 	at firrtl.options.Stage.transform(Stage.scala:46)
[error] 	at firrtl.options.Stage.execute(Stage.scala:57)
[error] 	at gcd.BugDriver$.delayedEndpoint$gcd$BugDriver$1(Bug.scala:19)
[error] 	at gcd.BugDriver$delayedInit$body.apply(Bug.scala:18)
[error] 	at scala.Function0.apply$mcV$sp(Function0.scala:39)
[error] 	at scala.Function0.apply$mcV$sp$(Function0.scala:39)
[error] 	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:17)
[error] 	at scala.App.$anonfun$main$1$adapted(App.scala:80)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.App.main(App.scala:80)
[error] 	at scala.App.main$(App.scala:78)
[error] 	at gcd.BugDriver$.main(Bug.scala:18)
[error] 	at gcd.BugDriver.main(Bug.scala)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.lang.reflect.Method.invoke(Method.java:498)
[error] Caused by: chisel3.internal.ChiselException: Exception thrown when elaborating ChiselGeneratorAnnotation
[error] 	at chisel3.stage.ChiselGeneratorAnnotation.elaborate(ChiselAnnotations.scala:55)
[error] 	at chisel3.stage.phases.Elaborate.$anonfun$transform$1(Elaborate.scala:19)
[error] 	at scala.collection.TraversableLike.$anonfun$flatMap$1(TraversableLike.scala:245)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.collection.TraversableLike.flatMap(TraversableLike.scala:245)
[error] 	at scala.collection.TraversableLike.flatMap$(TraversableLike.scala:242)
[error] 	at scala.collection.immutable.List.flatMap(List.scala:355)
[error] 	at chisel3.stage.phases.Elaborate.transform(Elaborate.scala:18)
[error] 	at chisel3.stage.phases.Elaborate.transform(Elaborate.scala:16)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.DependencyManager.$anonfun$transform$3(DependencyManager.scala:262)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.DependencyManager.transform(DependencyManager.scala:255)
[error] 	at firrtl.options.DependencyManager.transform$(DependencyManager.scala:240)
[error] 	at firrtl.options.PhaseManager.transform(DependencyManager.scala:419)
[error] 	at chisel3.stage.ChiselStage.run(ChiselStage.scala:35)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Stage.$anonfun$transform$5(Stage.scala:46)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.Stage.$anonfun$transform$3(Stage.scala:46)
[error] 	at logger.Logger$.$anonfun$makeScope$2(Logger.scala:168)
[error] 	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:62)
[error] 	at logger.Logger$.makeScope(Logger.scala:166)
[error] 	at firrtl.options.Stage.transform(Stage.scala:46)
[error] 	at firrtl.options.Stage.execute(Stage.scala:57)
[error] 	at gcd.BugDriver$.delayedEndpoint$gcd$BugDriver$1(Bug.scala:19)
[error] 	at gcd.BugDriver$delayedInit$body.apply(Bug.scala:18)
[error] 	at scala.Function0.apply$mcV$sp(Function0.scala:39)
[error] 	at scala.Function0.apply$mcV$sp$(Function0.scala:39)
[error] 	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:17)
[error] 	at scala.App.$anonfun$main$1$adapted(App.scala:80)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.App.main(App.scala:80)
[error] 	at scala.App.main$(App.scala:78)
[error] 	at gcd.BugDriver$.main(Bug.scala:18)
[error] 	at gcd.BugDriver.main(Bug.scala)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.lang.reflect.Method.invoke(Method.java:498)
[error] Caused by: java.lang.IllegalArgumentException: requirement failed
[error] 	at scala.Predef$.require(Predef.scala:268)
[error] 	at chisel3.internal.firrtl.KnownWidth.<init>(IR.scala:182)
[error] 	at chisel3.internal.firrtl.Width$.apply(IR.scala:156)
[error] 	at chisel3.Bits.$anonfun$do_apply$6(Bits.scala:169)
[error] 	at scala.Option.getOrElse(Option.scala:189)
[error] 	at chisel3.Bits.do_apply(Bits.scala:167)
[error] 	at gcd.BugModule.<init>(Bug.scala:14)
[error] 	at gcd.BugDriver$.$anonfun$new$1(Bug.scala:19)
[error] 	at chisel3.Module$.do_apply(Module.scala:52)
[error] 	at chisel3.stage.ChiselGeneratorAnnotation.$anonfun$elaborate$1(ChiselAnnotations.scala:50)
[error] 	at chisel3.internal.Builder$.$anonfun$build$1(Builder.scala:408)
[error] 	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:62)
[error] 	at chisel3.internal.Builder$.build(Builder.scala:406)
[error] 	at chisel3.stage.ChiselGeneratorAnnotation.elaborate(ChiselAnnotations.scala:50)
[error] 	at chisel3.stage.phases.Elaborate.$anonfun$transform$1(Elaborate.scala:19)
[error] 	at scala.collection.TraversableLike.$anonfun$flatMap$1(TraversableLike.scala:245)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.collection.TraversableLike.flatMap(TraversableLike.scala:245)
[error] 	at scala.collection.TraversableLike.flatMap$(TraversableLike.scala:242)
[error] 	at scala.collection.immutable.List.flatMap(List.scala:355)
[error] 	at chisel3.stage.phases.Elaborate.transform(Elaborate.scala:18)
[error] 	at chisel3.stage.phases.Elaborate.transform(Elaborate.scala:16)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.DependencyManager.$anonfun$transform$3(DependencyManager.scala:262)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.DependencyManager.transform(DependencyManager.scala:255)
[error] 	at firrtl.options.DependencyManager.transform$(DependencyManager.scala:240)
[error] 	at firrtl.options.PhaseManager.transform(DependencyManager.scala:419)
[error] 	at chisel3.stage.ChiselStage.run(ChiselStage.scala:35)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Stage.$anonfun$transform$5(Stage.scala:46)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.Stage.$anonfun$transform$3(Stage.scala:46)
[error] 	at logger.Logger$.$anonfun$makeScope$2(Logger.scala:168)
[error] 	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:62)
[error] 	at logger.Logger$.makeScope(Logger.scala:166)
[error] 	at firrtl.options.Stage.transform(Stage.scala:46)
[error] 	at firrtl.options.Stage.execute(Stage.scala:57)
[error] 	at gcd.BugDriver$.delayedEndpoint$gcd$BugDriver$1(Bug.scala:19)
[error] 	at gcd.BugDriver$delayedInit$body.apply(Bug.scala:18)
[error] 	at scala.Function0.apply$mcV$sp(Function0.scala:39)
[error] 	at scala.Function0.apply$mcV$sp$(Function0.scala:39)
[error] 	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:17)
[error] 	at scala.App.$anonfun$main$1$adapted(App.scala:80)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.App.main(App.scala:80)
[error] 	at scala.App.main$(App.scala:78)
[error] 	at gcd.BugDriver$.main(Bug.scala:18)
[error] 	at gcd.BugDriver.main(Bug.scala)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.lang.reflect.Method.invoke(Method.java:498)
[error] stack trace is suppressed; run 'last Compile / bgRunMain' for the full output
[error] Nonzero exit code: 1
[error] (Compile / runMain) Nonzero exit code: 1
[error] Total time: 5 s, completed Jun 6, 2020 2:06:53 PM

Negative bounds:

package gcd

import chisel3._
import chisel3.stage.{ChiselGeneratorAnnotation, ChiselStage}

class BugModule extends Module {
  val io = IO(new Bundle {
    val in  = Input(UInt(16.W))
    val out = Output(UInt(16.W))
  })

  io.out := io.in(15, -1)
}


object BugDriver extends App {
  (new ChiselStage).execute(args, Seq(ChiselGeneratorAnnotation(() => new BugModule)))
}

[info] Loading settings for project chisel_bad_error-build from plugins.sbt ...
[info] Loading project definition from /home/tom/src/bugs/chisel_bad_error/project
[info] Loading settings for project chisel_bad_error from build.sbt ...
[info] Set current project to chisel-module-template (in build file:/home/tom/src/bugs/chisel_bad_error/)
[info] running gcd.BugDriver 
[info] [0.002] Elaborating design...
[error] Bits.scala:160: Invalid bit range (15,-1) in class chisel3.Bits
[error] There were 1 error(s) during hardware elaboration.
[error] chisel3.internal.ChiselException: Fatal errors during hardware elaboration
[error] 	...
[error] 	... (Stack trace trimmed to user code only, rerun with --full-stacktrace if you wish to see the full stack trace)
[error] (run-main-0) firrtl.options.StageError: 
[error] firrtl.options.StageError: 
[error] 	at chisel3.stage.ChiselStage.run(ChiselStage.scala:49)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Stage.$anonfun$transform$5(Stage.scala:46)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.Stage.$anonfun$transform$3(Stage.scala:46)
[error] 	at logger.Logger$.$anonfun$makeScope$2(Logger.scala:168)
[error] 	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:62)
[error] 	at logger.Logger$.makeScope(Logger.scala:166)
[error] 	at firrtl.options.Stage.transform(Stage.scala:46)
[error] 	at firrtl.options.Stage.execute(Stage.scala:57)
[error] 	at gcd.BugDriver$.delayedEndpoint$gcd$BugDriver$1(Bug.scala:19)
[error] 	at gcd.BugDriver$delayedInit$body.apply(Bug.scala:18)
[error] 	at scala.Function0.apply$mcV$sp(Function0.scala:39)
[error] 	at scala.Function0.apply$mcV$sp$(Function0.scala:39)
[error] 	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:17)
[error] 	at scala.App.$anonfun$main$1$adapted(App.scala:80)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.App.main(App.scala:80)
[error] 	at scala.App.main$(App.scala:78)
[error] 	at gcd.BugDriver$.main(Bug.scala:18)
[error] 	at gcd.BugDriver.main(Bug.scala)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.lang.reflect.Method.invoke(Method.java:498)
[error] Caused by: chisel3.internal.ChiselException: Fatal errors during hardware elaboration
[error] 	at chisel3.internal.throwException$.apply(Error.scala:85)
[error] 	at chisel3.internal.ErrorLog.checkpoint(Error.scala:152)
[error] 	at chisel3.internal.Builder$.$anonfun$build$1(Builder.scala:410)
[error] 	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:62)
[error] 	at chisel3.internal.Builder$.build(Builder.scala:406)
[error] 	at chisel3.stage.ChiselGeneratorAnnotation.elaborate(ChiselAnnotations.scala:50)
[error] 	at chisel3.stage.phases.Elaborate.$anonfun$transform$1(Elaborate.scala:19)
[error] 	at scala.collection.TraversableLike.$anonfun$flatMap$1(TraversableLike.scala:245)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.collection.TraversableLike.flatMap(TraversableLike.scala:245)
[error] 	at scala.collection.TraversableLike.flatMap$(TraversableLike.scala:242)
[error] 	at scala.collection.immutable.List.flatMap(List.scala:355)
[error] 	at chisel3.stage.phases.Elaborate.transform(Elaborate.scala:18)
[error] 	at chisel3.stage.phases.Elaborate.transform(Elaborate.scala:16)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.DependencyManager.$anonfun$transform$3(DependencyManager.scala:262)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.DependencyManager.transform(DependencyManager.scala:255)
[error] 	at firrtl.options.DependencyManager.transform$(DependencyManager.scala:240)
[error] 	at firrtl.options.PhaseManager.transform(DependencyManager.scala:419)
[error] 	at chisel3.stage.ChiselStage.run(ChiselStage.scala:35)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.Stage$$anon$1.transform(Stage.scala:43)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:37)
[error] 	at firrtl.options.phases.DeletedWrapper.internalTransform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Translator.transform(Phase.scala:240)
[error] 	at firrtl.options.Translator.transform$(Phase.scala:240)
[error] 	at firrtl.options.phases.DeletedWrapper.transform(DeletedWrapper.scala:15)
[error] 	at firrtl.options.Stage.$anonfun$transform$5(Stage.scala:46)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
[error] 	at scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
[error] 	at scala.collection.immutable.List.foldLeft(List.scala:89)
[error] 	at firrtl.options.Stage.$anonfun$transform$3(Stage.scala:46)
[error] 	at logger.Logger$.$anonfun$makeScope$2(Logger.scala:168)
[error] 	at scala.util.DynamicVariable.withValue(DynamicVariable.scala:62)
[error] 	at logger.Logger$.makeScope(Logger.scala:166)
[error] 	at firrtl.options.Stage.transform(Stage.scala:46)
[error] 	at firrtl.options.Stage.execute(Stage.scala:57)
[error] 	at gcd.BugDriver$.delayedEndpoint$gcd$BugDriver$1(Bug.scala:19)
[error] 	at gcd.BugDriver$delayedInit$body.apply(Bug.scala:18)
[error] 	at scala.Function0.apply$mcV$sp(Function0.scala:39)
[error] 	at scala.Function0.apply$mcV$sp$(Function0.scala:39)
[error] 	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:17)
[error] 	at scala.App.$anonfun$main$1$adapted(App.scala:80)
[error] 	at scala.collection.immutable.List.foreach(List.scala:392)
[error] 	at scala.App.main(App.scala:80)
[error] 	at scala.App.main$(App.scala:78)
[error] 	at gcd.BugDriver$.main(Bug.scala:18)
[error] 	at gcd.BugDriver.main(Bug.scala)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.lang.reflect.Method.invoke(Method.java:498)
[error] stack trace is suppressed; run 'last Compile / bgRunMain' for the full output
[error] Nonzero exit code: 1
[error] (Compile / runMain) Nonzero exit code: 1
[error] Total time: 4 s, completed Jun 6, 2020 2:09:08 PM

What is the expected behavior?

These are examples where the error reporting (IMHO) is clear and precise.

High bit out of bounds:

package gcd

import chisel3._
import chisel3.stage.{ChiselGeneratorAnnotation, ChiselStage}

class BugModule extends Module {
  val io = IO(new Bundle {
    val in  = Input(UInt(16.W))
    val out = Output(UInt(16.W))
  })

  io.out := io.in(16, 0)
}


object BugDriver extends App {
  (new ChiselStage).execute(args, Seq(ChiselGeneratorAnnotation(() => new BugModule)))
}

[info] Loading settings for project chisel_bad_error-build from plugins.sbt ...
[info] Loading project definition from /home/tom/src/bugs/chisel_bad_error/project
[info] Loading settings for project chisel_bad_error from build.sbt ...
[info] Set current project to chisel-module-template (in build file:/home/tom/src/bugs/chisel_bad_error/)
[info] running gcd.BugDriver 
[info] [0.002] Elaborating design...
[info] [0.097] Done elaborating.
Computed transform order in: 397.3 ms
[error] (run-main-0) firrtl.passes.CheckWidths$BitsWidthException:  @[Bug.scala 14:18]: [target ~BugModule|BugModule] High bit 16 in bits operator is larger than input width 16 in bits(io.in, 16, 0).
[error] firrtl.passes.CheckWidths$BitsWidthException:  @[Bug.scala 14:18]: [target ~BugModule|BugModule] High bit 16 in bits operator is larger than input width 16 in bits(io.in, 16, 0).
[error] stack trace is suppressed; run 'last Compile / bgRunMain' for the full output
[error] Nonzero exit code: 1
[error] (Compile / runMain) Nonzero exit code: 1
[error] Total time: 4 s, completed Jun 6, 2020 2:02:18 PM

Please tell us about your environment: See linked chisel-template commit.

What is the use case for changing the behavior? New-user experience.

Contributor guide

Research direction
Examine the Chisel error reporting code in Data.scala and Builder.scala to add clearer messages for common mistakes like wrong assignment direction or reversed subword bounds.
Tech stack
scala
Domain
compilers
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
ScalaChisel
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80