Index: src/Common/utility.h
===================================================================
--- src/Common/utility.h	(revision 66ef082f967c9b603cac1112ed2a7902eef0ea35)
+++ src/Common/utility.h	(revision cbb675d18003fb910aa3be3afa6c9460760945c0)
@@ -322,5 +322,5 @@
 	std::string filename;
 
-    /// Create a new unset CodeLocation.
+	/// Create a new unset CodeLocation.
 	CodeLocation()
 		: linenumber( -1 )
@@ -328,5 +328,5 @@
 	{}
 
-    /// Create a new CodeLocation with the given values.
+	/// Create a new CodeLocation with the given values.
 	CodeLocation( const char* filename, int lineno )
 		: linenumber( lineno )
@@ -334,11 +334,11 @@
 	{}
 
-    bool isSet () const {
-        return -1 != linenumber;
-    }
-
-    bool isUnset () const {
-        return !isSet();
-    }
+	bool isSet () const {
+		return -1 != linenumber;
+	}
+
+	bool isUnset () const {
+		return !isSet();
+	}
 
 	void unset () {
@@ -353,4 +353,5 @@
 	return location.isSet() ? location.filename + ":" + std::to_string(location.linenumber) + " " : "";
 }
+
 #endif // _UTILITY_H
 
Index: src/GenPoly/Box.cc
===================================================================
--- src/GenPoly/Box.cc	(revision 66ef082f967c9b603cac1112ed2a7902eef0ea35)
+++ src/GenPoly/Box.cc	(revision cbb675d18003fb910aa3be3afa6c9460760945c0)
@@ -765,4 +765,8 @@
 						arg = new AddressExpr( arg );
 					}
+					if ( ! ResolvExpr::typesCompatible( param, arg->get_result(), SymTab::Indexer() ) ) {
+						// silence warnings by casting boxed parameters when the actual type does not match up with the formal type.
+						arg = new CastExpr( arg, param->clone() );
+					}
 				} else {
 					// use type computed in unification to declare boxed variables
@@ -902,6 +906,5 @@
 				} // if
 				UntypedExpr *assign = new UntypedExpr( new NameExpr( "?=?" ) );
-				UntypedExpr *deref = new UntypedExpr( new NameExpr( "*?" ) );
-				deref->get_args().push_back( new CastExpr( new VariableExpr( *param++ ), new PointerType( Type::Qualifiers(), realType->get_returnVals().front()->get_type()->clone() ) ) );
+				UntypedExpr *deref = UntypedExpr::createDeref( new CastExpr( new VariableExpr( *param++ ), new PointerType( Type::Qualifiers(), realType->get_returnVals().front()->get_type()->clone() ) ) );
 				assign->get_args().push_back( deref );
 				addAdapterParams( adapteeApp, arg, param, adapterType->get_parameters().end(), realParam, tyVars );
@@ -1217,11 +1220,4 @@
 
 		Statement * Pass1::mutate( ReturnStmt *returnStmt ) {
-			// maybe need access to the env when mutating the expr
-			if ( Expression * expr = returnStmt->get_expr() ) {
-				if ( expr->get_env() ) {
-					env = expr->get_env();
-				}
-			}
-
 			if ( retval && returnStmt->get_expr() ) {
 				assert( returnStmt->get_expr()->has_result() && ! returnStmt->get_expr()->get_result()->isVoid() );
@@ -1539,6 +1535,6 @@
 					Type *declType = objectDecl->get_type();
 					std::string bufName = bufNamer.newName();
-					ObjectDecl *newBuf = new ObjectDecl( bufName, Type::StorageClasses(), LinkageSpec::C, 0, 
-						new ArrayType( Type::Qualifiers(), new BasicType( Type::Qualifiers(), BasicType::Kind::Char), new NameExpr( sizeofName( mangleType(declType) ) ), 
+					ObjectDecl *newBuf = new ObjectDecl( bufName, Type::StorageClasses(), LinkageSpec::C, 0,
+						new ArrayType( Type::Qualifiers(), new BasicType( Type::Qualifiers(), BasicType::Kind::Char), new NameExpr( sizeofName( mangleType(declType) ) ),
 						true, false, std::list<Attribute*>{ new Attribute( std::string{"aligned"}, std::list<Expression*>{ new ConstantExpr( Constant::from_int(8) ) } ) } ), 0 );
 					stmtsToAdd.push_back( new DeclStmt( noLabels, newBuf ) );
@@ -1578,15 +1574,4 @@
 		}
 
-		/// Returns an expression dereferenced n times
-		Expression *makeDerefdVar( Expression *derefdVar, long n ) {
-			for ( int i = 1; i < n; ++i ) {
-				UntypedExpr *derefExpr = new UntypedExpr( new NameExpr( "*?" ) );
-				derefExpr->get_args().push_back( derefdVar );
-				// xxx - should set results on derefExpr
-				derefdVar = derefExpr;
-			}
-			return derefdVar;
-		}
-
 		Expression *PolyGenericCalculator::mutate( MemberExpr *memberExpr ) {
 			// mutate, exiting early if no longer MemberExpr
@@ -1595,14 +1580,7 @@
 			if ( ! memberExpr ) return expr;
 
-			// get declaration for base struct, exiting early if not found
-			int varDepth;
-			VariableExpr *varExpr = getBaseVar( memberExpr->get_aggregate(), &varDepth );
-			if ( ! varExpr ) return memberExpr;
-			ObjectDecl *objectDecl = dynamic_cast< ObjectDecl* >( varExpr->get_var() );
-			if ( ! objectDecl ) return memberExpr;
-
 			// only mutate member expressions for polymorphic types
 			int tyDepth;
-			Type *objectType = hasPolyBase( objectDecl->get_type(), scopeTyVars, &tyDepth );
+			Type *objectType = hasPolyBase( memberExpr->get_aggregate()->get_result(), scopeTyVars, &tyDepth );
 			if ( ! objectType ) return memberExpr;
 			findGeneric( objectType ); // ensure layout for this type is available
@@ -1622,8 +1600,13 @@
 				fieldLoc->get_args().push_back( aggr );
 				fieldLoc->get_args().push_back( makeOffsetIndex( objectType, i ) );
+				fieldLoc->set_result( memberExpr->get_result()->clone() );
 				newMemberExpr = fieldLoc;
 			} else if ( dynamic_cast< UnionInstType* >( objectType ) ) {
-				// union members are all at offset zero, so build appropriately-dereferenced variable
-				newMemberExpr = makeDerefdVar( varExpr->clone(), varDepth );
+				// union members are all at offset zero, so just use the aggregate expr
+				Expression * aggr = memberExpr->get_aggregate()->clone();
+				delete aggr->get_env(); // xxx - there's a problem with keeping the env for some reason, so for now just get rid of it
+				aggr->set_env( nullptr );
+				newMemberExpr = aggr;
+				newMemberExpr->set_result( memberExpr->get_result()->clone() );
 			} else return memberExpr;
 			assert( newMemberExpr );
@@ -1633,6 +1616,5 @@
 				// Not all members of a polymorphic type are themselves of polymorphic type; in this case the member expression should be wrapped and dereferenced to form an lvalue
 				CastExpr *ptrCastExpr = new CastExpr( newMemberExpr, new PointerType( Type::Qualifiers(), memberType->clone() ) );
-				UntypedExpr *derefExpr = new UntypedExpr( new NameExpr( "*?" ) );
-				derefExpr->get_args().push_back( ptrCastExpr );
+				UntypedExpr *derefExpr = UntypedExpr::createDeref( ptrCastExpr );
 				newMemberExpr = derefExpr;
 			}