DataType extractReturnType(String signatureText) throws ParseException, CancelledException {
		int parenIndex = signatureText.indexOf('(');
		if (parenIndex < 0) {
			throw new ParseException("Can't find return type");
		}
		String[] split = StringUtils.split(signatureText.substring(0, parenIndex));
		if (split.length < 2) {
			throw new ParseException("Can't find return type");
		}
		String returnTypeName = StringUtils.join(split, " ", 0, split.length - 1);

		DataType dt = resolveDataType(returnTypeName);
		if (dt == null) {
			throw new ParseException("Can't resolve return type: " + returnTypeName);
		}
		return dt;
	}
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