in Backend/Core/ForTea.Core/Services/TypingAssist/T4TypingAssist.cs [286:298]
private bool IsInAttributeValue([NotNull] ITextControl textControl)
{
var lexer = GetCachingLexer(textControl);
if (lexer == null) return false;
var offset = textControl.Caret.DocumentOffset();
if (offset.Offset <= 1) return false;
if (!lexer.FindTokenAt(offset.Offset - 1)) return false;
var tokenType = lexer.TokenType;
if (AttributeValueTokens.Contains(tokenType)) return true;
if (tokenType != T4TokenNodeTypes.QUOTE) return false;
if (!lexer.FindTokenAt(offset.Offset)) return false;
return tokenType == T4TokenNodeTypes.QUOTE || tokenType == T4TokenNodeTypes.RAW_ATTRIBUTE_VALUE;
}