add overassign diagnostics

Author: ducky64

compiler/src/main/scala/edg/compiler/ConstProp.scala

@@ -207,11 +207,9 @@ class ConstProp() {
     } else {
       if (!forcedParams.contains(target)) {
         if (params.nodeDefinedAt(target)) { // TODO add propagated assign
-          //        paramSource.get(target).map { case (root, constrName, value) =>
-          //          CompilerError.OverAssignCause.Assign(target, root, constrName, value)
-          //        }.toSeq
+          val (prevRoot, prevConstr, _) = paramSource.get(target).getOrElse("?", "?", "")
           paramErrors.getOrElseUpdate(target, mutable.ListBuffer()).append(
-            ErrorValue(s"over-assign from $root.$constrName")
+            ErrorValue(s"over-assign from $root.$constrName, prev assigned from $prevRoot.$prevConstr")
           )
           return // first set "wins"
         }

compiler/src/test/scala/edg/compiler/ConstPropAssignTest.scala

@@ -178,21 +178,6 @@ class ConstPropAssignTest extends AnyFlatSpec {
     constProp2.getValue(IndirectDesignPath() + "a") should equal(Some(IntValue(3)))
   }
 
-  it should "not propagate ErrorValues" in {
-    import edgir.expr.expr.BinaryExpr.Op
-    val constProp = new ConstProp()
-    constProp.addDeclaration(DesignPath() + "a", ValInit.Integer)
-    constProp.addDeclaration(DesignPath() + "b", ValInit.Integer)
-    constProp.addAssignValue(IndirectDesignPath() + "a", ErrorValue("error!"))
-    constProp.addAssignExpr(
-      IndirectDesignPath() + "b",
-      ValueExpr.BinOp(Op.ADD, ValueExpr.Literal(3), ValueExpr.Ref("a")),
-    )
-    constProp.getValue(IndirectDesignPath() + "a") should equal(None)
-    constProp.getValue(IndirectDesignPath() + "b") should equal(None)
-    constProp.getErrors should not be empty
-  }
-
   it should "not propagate generated ErrorValues" in {
     import edgir.expr.expr.BinaryExpr.Op
     val constProp = new ConstProp()