Improve exception message for aliased bundle fields (#2304)

- Shows groups of field names that share a common id (i.e. aliased)
- Show, as much as possible, them in the order that fields appear in bundle
- Updated BundleSpec's relevant tests

Co-authored-by: Megan Wachs <megan@sifive.com>
Co-authored-by: Jack Koenig <koenig@sifive.com>

2 files changed, 34 insertions, 6 deletions

diff --git a/src/test/scala/chiselTests/BundleSpec.scala b/src/test/scala/chiselTests/BundleSpec.scala
index 51dedfb1..d9f82e6d 100644
--- a/src/test/scala/chiselTests/BundleSpec.scala
+++ b/src/test/scala/chiselTests/BundleSpec.scala
@@ -111,17 +111,21 @@ class BundleSpec extends ChiselFlatSpec with BundleSpecUtils with Utils {
     }
   }
 
-  "Bundles" should "not have aliased fields" in {
+  "Bundles" should "with aliased fields, should show a helpful error message" in {
+    class AliasedBundle extends Bundle {
+      val a = UInt(8.W)
+      val b = a
+      val c = SInt(8.W)
+      val d = c
+    }
+
     (the[ChiselException] thrownBy extractCause[ChiselException] {
       ChiselStage.elaborate { new Module {
-        val io = IO(Output(new Bundle {
-          val a = UInt(8.W)
-          val b = a
-        }))
+        val io = IO(Output(new AliasedBundle))
         io.a := 0.U
         io.b := 1.U
       } }
-    }).getMessage should include("aliased fields")
+    }).getMessage should include("contains aliased fields named (a,b),(c,d)")
   }
 
   "Bundles" should "not have bound hardware" in {
diff --git a/src/test/scala/chiselTests/RecordSpec.scala b/src/test/scala/chiselTests/RecordSpec.scala
index f0edca8b..e6986efb 100644
--- a/src/test/scala/chiselTests/RecordSpec.scala
+++ b/src/test/scala/chiselTests/RecordSpec.scala
@@ -8,6 +8,8 @@ import chisel3.testers.BasicTester
 import chisel3.util.{Counter, Queue}
 import chisel3.experimental.DataMirror
 
+import scala.collection.immutable.SeqMap
+
 trait RecordSpecUtils {
   class MyBundle extends Bundle {
     val foo = UInt(32.W)
@@ -64,6 +66,11 @@ trait RecordSpecUtils {
     }
   }
 
+  class AliasedRecord extends Module {
+    val field = UInt(32.W)
+    val io = IO(new CustomBundle("in" -> Input(field), "out" -> Output(field)))
+  }
+
   class RecordIOModule extends Module {
     val io = IO(new CustomBundle("in" -> Input(UInt(32.W)), "out" -> Output(UInt(32.W))))
     io("out") := io("in")
@@ -103,6 +110,23 @@ class RecordSpec extends ChiselFlatSpec with RecordSpecUtils with Utils {
     ChiselStage.elaborate { new MyModule(new MyBundle, fooBarType) }
   }
 
+  they should "not allow aliased fields" in {
+    class AliasedFieldRecord extends Record {
+      val foo = UInt(8.W)
+      val elements = SeqMap("foo" -> foo, "bar" -> foo)
+      override def cloneType: AliasedFieldRecord.this.type = this
+    }
+
+    val e = intercept[AliasedAggregateFieldException] {
+      ChiselStage.elaborate {
+        new Module {
+          val io = IO(new AliasedFieldRecord)
+        }
+      }
+    }
+    e.getMessage should include ("contains aliased fields named (bar,foo)")
+  }
+
   they should "follow UInt serialization/deserialization API" in {
     assertTesterPasses { new RecordSerializationTest }
   }