public SyntaxTree Get(SourceText sourceText) { Requires.NotNull(sourceText, nameof(sourceText)); SyntaxTree syntaxTree; if (this.sources.TryGetValue(sourceText, out syntaxTree)) { return(syntaxTree); } using (var stream = sourceText.GetStream()) syntaxTree = SyntaxTree.CreateFromSteam(stream); this.sources.Add(sourceText, syntaxTree); return(syntaxTree); }