Token detection was broken for conditional and for expressions that
represent template control sequences. The code originally attempted to
determine whether or not a conditional or for expression was a control
sequence by inspecting the expression's parent. Unfortunately, that
approach is unable to distinguish between expressions that are control
sequences and those that are merely template parts. These changes
instead inspect the first token of the expression for a template control
token (i.e. `%{`): if such a token is found, the expression is detected
as a template control sequence.
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