public static Expression FromText(string source)
{
var lexer = new FlowScriptLexer(new AntlrInputStream(source));
var tokenStream = new CommonTokenStream(lexer);
// parse expression
var parser = new FlowScriptParser(tokenStream);
parser.BuildParseTree = true;
var expressionParseTree = parser.expression();
// parse ast nodes
var compilationUnitParser = new CompilationUnitParser();
compilationUnitParser.TryParseExpression(expressionParseTree, out var expression);
// resolve types
var typeResolver = new TypeResolver();
typeResolver.TryResolveTypesInExpression(expression);
return(expression);
}