- Only allow assignment at the top level in an expression statement.
- Allow both negation and complement as subexpressions of both bitwise
and numeric operators.
- Remove parsing support for postincrement and postdecrement.
- Add parsing support for `as` operator.
- Use the same ambient precedence for types and non-type expressions.
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Co-authored-by: Chandler Carruth <chandlerc@gmail.com>