private DataType resolveDataType(String dataTypeName) throws CancelledException {
		if (dtMap.containsKey(dataTypeName)) {
			return dtMap.get(dataTypeName);
		}

		DataType dataType = null;
		try {
			dataType = dataTypeParser.parse(dataTypeName);
		}
		catch (InvalidDataTypeException e) {
			// ignore - return null
		}
		return dataType;
	}
Parse the given function signature text into a FunctionDefinitionDataType.

@param originalSignature the function signature before editing. This may be
                         null if the user is entering a new signature instead
                         of editing an existing one.
@param signatureText     the text to be parsed into a function signature.
@return the FunctionDefinitionDataType resulting from parsing.
@throws ParseException if the text could not be parsed.
@throws CancelledException if parse cancelled by user
Ghidra/Features/Base/src/main/java/ghidra/app/util/parser/FunctionSignatureParser.java