1 files changed, 32 insertions, 0 deletions

diff --git a/subprojects/language/src/main/java/tools/refinery/language/typesystem/MutableType.java b/subprojects/language/src/main/java/tools/refinery/language/typesystem/MutableType.java
new file mode 100644
index 00000000..78fdf884
--- /dev/null
+++ b/subprojects/language/src/main/java/tools/refinery/language/typesystem/MutableType.java
@@ -0,0 +1,32 @@
+/*
+ * SPDX-FileCopyrightText: 2024 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package tools.refinery.language.typesystem;
+
+public final class MutableType implements ExprType {
+        private DataExprType actualType;
+
+        @Override
+        public FixedType getActualType() {
+                return actualType == null ? INVALID : actualType;
+        }
+
+        public void setActualType(DataExprType actualType) {
+                if (this.actualType != null) {
+                        throw new IllegalStateException("Actual type was already set");
+                }
+                this.actualType = actualType;
+        }
+
+        @Override
+        public ExprType unwrapIfSet() {
+                return actualType == null ? this : actualType;
+        }
+
+        @Override
+        public String toString() {
+                return getActualType().toString();
+        }
+}