improve resource connection errors

Author: Oron Port

core/src/main/scala/dfhdl/core/DFVal.scala

@@ -1239,8 +1239,9 @@ extension [T <: DFTypeAny](dfVar: DFValOf[T])
 extension [T <: DFTypeAny](lhs: DFValOf[T])
   def connect(resource: Resource)(using dfc: DFC): Unit =
     import dfc.getSet
+    import dfhdl.compiler.analysis.DclPort
     lhs.asIR.departialDcl match
-      case Some(dcl, range) =>
+      case Some(dcl @ DclPort(), range) if dcl.getOwnerDesign.isTop =>
         val newSigConstraints =
           if (range.length != dcl.width) resource.allSigConstraints.flatMap { cs =>
             for (i <- range) yield cs.updateBitIdx(i)
@@ -1254,7 +1255,10 @@ extension [T <: DFTypeAny](lhs: DFValOf[T])
           (existingSigConstraints ++ newSigConstraints).merge.consolidate(dcl.width)
         val updatedAnnotations = updatedSigConstraints ++ otherAnnotations
         dcl.setMeta(m => m.copy(annotations = updatedAnnotations))
-      case None =>
+      case _ =>
+        throw new IllegalArgumentException(
+          "Cannot apply resource constraints to a non-top-level port value."
+        )
     end match
   end connect
   def connect[R <: DFTypeAny](rhs: DFValOf[R])(using DFC): Unit =
@@ -1461,6 +1465,7 @@ object DFPortOps:
     )(using
         connectableOnly: ConnectableOnly[C, rhs.ExactFrom]
     ): ConnectPlaceholder =
+      given CTName = CTName("<>")
       trydf {
         rhs.exactFrom match
           case resource: Resource => dfPort.connect(resource)

core/src/main/scala/dfhdl/platforms/resources/Resource.scala

@@ -3,6 +3,7 @@ import scala.annotation.implicitNotFound
 import scala.collection.mutable
 import dfhdl.compiler.ir.constraints.SigConstraint
 import dfhdl.core.*
+import dfhdl.internals.CTName
 
 trait Resource extends ResourceContext:
   private val connections = mutable.ListBuffer[Resource]()
@@ -43,7 +44,9 @@ object Resource extends ResourceLP:
       resource1.connect(resource2)
       resource2.connect(resource1)
   given [T <: Resource, R <: DFValAny](using DFC): CanConnect[T, R] =
-    (resource: T, dfVal: R) => dfVal.connect(resource)
+    (resource: T, dfVal: R) =>
+      given CTName = CTName("<>")
+      trydf { dfVal.connect(resource) }
 
   object Ops:
     extension [T <: Resource](self: T)