Check field referential equality in autoclonetype

chiselFrontend/src/main/scala/chisel3/core/Aggregate.scala

@@ -658,6 +658,22 @@ abstract class Bundle(implicit compileOptions: CompileOptions) extends Record {
       throw new AutoClonetypeException(s"Unable to automatically infer cloneType on $clazz: $desc")
     }
 
+    def validateClone(clone: Bundle, equivDiagnostic: String): Unit = {
+      if (!clone.typeEquivalent(this)) {
+        autoClonetypeError(s"Automatically cloned $clone not type-equivalent to base $this. " + equivDiagnostic)
+      }
+
+      for ((name, field) <- elements) {
+        if (clone.elements(name) eq field) {
+          autoClonetypeError(s"Automatically cloned $clone has field $name aliased with base $this." +
+            " In the future, this can be solved by wrapping the field in Field(...)," +
+            " see https://github.com/freechipsproject/chisel3/pull/909." +
+            " For now, ensure Chisel types used in the Bundle definition are passed through constructor arguments," +
+            " or wrapped in Input(...), Output(...), or Flipped(...) if appropriate.")
+        }
+      }
+    }
+
     val mirror = runtimeMirror(clazz.getClassLoader)
     val classSymbolOption = try {
       Some(mirror.reflect(this).symbol)
@@ -741,10 +757,7 @@ abstract class Bundle(implicit compileOptions: CompileOptions) extends Record {
       clone match {
         case Some(clone) =>
           clone._outerInst = this._outerInst
-          if (!clone.typeEquivalent(this)) {
-            autoClonetypeError(s"automatically cloned $clone not type-equivalent to base." +
-            " Constructor argument values were not inferred, ensure constructor is deterministic.")
-          }
+          validateClone(clone, "Constructor argument values were not inferred, ensure constructor is deterministic.")
           return clone.asInstanceOf[this.type]
         case None =>
       }
@@ -781,6 +794,8 @@ abstract class Bundle(implicit compileOptions: CompileOptions) extends Record {
       try {
         val clone = ctors.head.newInstance(outerClassInstance.get._2).asInstanceOf[this.type]
         clone._outerInst = this._outerInst
+
+        validateClone(clone, "Outer class instance was inferred, ensure constructor is deterministic.")
         return clone
       } catch {
         case e @ (_: java.lang.reflect.InvocationTargetException | _: IllegalArgumentException) =>
@@ -844,14 +859,11 @@ abstract class Bundle(implicit compileOptions: CompileOptions) extends Record {
     val clone = classMirror.reflectConstructor(ctor).apply(ctorParamsVals:_*).asInstanceOf[this.type]
     clone._outerInst = this._outerInst
 
-    if (!clone.typeEquivalent(this)) {
-      // scalastyle:off line.size.limit
-      autoClonetypeError(s"Automatically cloned $clone not type-equivalent to base $this." +
-          " Constructor argument values were inferred: ensure that variable names are consistent and have the same value throughout the constructor chain," +
-          " and that the constructor is deterministic.")
-      // scalastyle:on line.size.limit
-    }
-
+    validateClone(clone,
+      "Constructor argument values were inferred:" +
+        " ensure that variable names are consistent and have the same value throughout the constructor chain," +
+        " and that the constructor is deterministic."
+    )
     clone
   }
 

src/test/scala/chiselTests/AutoClonetypeSpec.scala

@@ -172,4 +172,29 @@ class AutoClonetypeSpec extends ChiselFlatSpec {
       val a = WireDefault(io)
     } }
   }
+
+  "Aliased fields" should "be caught" in {
+    a [ChiselException] should be thrownBy {
+      elaborate { new Module {
+        val bundleFieldType = UInt(8.W)
+        val io = IO(Output(new Bundle {
+          val a = bundleFieldType
+        }))
+        io.a := 0.U
+      } }
+    }
+  }
+
+  "Aliased fields from inadequate autoclonetype" should "be caught" in {
+    a [ChiselException] should be thrownBy {
+      class BadBundle(val typeTuple: (Data, Int)) extends Bundle {
+        val a = typeTuple._1
+      }
+
+      elaborate { new Module {
+        val io = IO(Output(new BadBundle(UInt(8.W), 1)))
+        io.a := 0.U
+      } }
+    }
+  }
 }