Incorrect classification (and therefore IntelliSense) for expressions containing transition characters (ex @)

[dougbu]

When providing values for non-string tag helper properties, Razor authors lose IntelliSense and other C# support when the expression contains transitions. A simple example would be <element non-string="@object + value" />.

Using existing MVC tag helpers in a contrived way, the following illustrates the issue. Note only @ValidationSummary.All is highlighted in the second case. Even the attribute name gets the wrong classification.

Problem is likely related to fact not all Span components of the more-complex expression get SpanKind.Code. In particular TagHelperBlockRewriter.CreateMarkupAttribute() isn't called on every code path through TagHelperBlockRewriter.TryParseBlock().

[NTaylorMullen]

039062c