GP-6475 follow up on datatype merge action to only popup on supported

datatypes.

Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/actions/MergeDataTypeAction.java

@@ -57,12 +57,6 @@ public class MergeDataTypeAction extends DockingAction {
 		setHelpLocation(new HelpLocation("DataTypeManagerPlugin", "merge_datatypes"));
 	}
 
-	@Override
-	public boolean isAddToPopup(ActionContext context) {
-		DataTypeTreeNode node = getSelectedDataTypeTreeNode(context);
-		return node instanceof DataTypeNode;
-	}
-
 	@Override
 	public boolean isEnabledForContext(ActionContext context) {
 		DataTypeTreeNode node = getSelectedDataTypeTreeNode(context);
@@ -75,6 +69,10 @@ public class MergeDataTypeAction extends DockingAction {
 		}
 
 		DataType dataType = dtNode.getDataType();
+		if (!DataTypeUtilities.supportsMerge(dataType)) {
+			return false;
+		}
+		
 		DataTypeManager dataTypeManager = dataType.getDataTypeManager();
 
 		// for now, only allow merging on program datatypes.

Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/data/DataTypeUtilities.java

@@ -1106,6 +1106,16 @@ public class DataTypeUtilities {
 		return getNameWithoutConflict(name1).equals(getNameWithoutConflict(name2));
 	}
 	
+
+	/**
+	 * Returns true if there is a {@link DataTypeMerger} that can handle the given datatype. Currently, only structures
+	 * unions, and enums are supported.
+	 * @param dataType the dataType to check
+	 * @return true if there is support for merging that dataType
+	 */
+	public static boolean supportsMerge(DataType dataType) {
+		return dataType instanceof Composite || dataType instanceof Enum;
+	}
 	/**
 	 * Convenience method for getting the appropriate datatype merger or throwing an exception
 	 * if the two datatypes are not eligible to be merged.