博客围绕while语句展开，阐述了变量v在while语句不同位置的确定赋值状态。包括在表达式开始时与语句开始时状态相同，以及根据表达式结束时v的不同赋值状态，分析其在控制流转移到循环体和语句终点时的赋值情况。
12.3.3.7 While statements
For a while statement stmt of the form:
while (expr) while-body
?v has the same definite assignment state at the beginning of expr as at
the beginning of stmt.
?If v is definitely assigned at the end of expr, then it is definitely
assigned on the control flow transfer
to while-body and to the end point of stmt.
?If v has the state .definitely assigned after true expression. at the end
of expr, then it is definitely
assigned on the control flow transfer to while-body, but not definitely
assigned at the end-point of
stmt.
?If v has the state .definitely assigned after false expression. at the
end of expr, then it is definitely
assigned on the control flow transfer to the end point of stmt.
For a while statement stmt of the form:
while (expr) while-body
?v has the same definite assignment state at the beginning of expr as at
the beginning of stmt.
?If v is definitely assigned at the end of expr, then it is definitely
assigned on the control flow transfer
to while-body and to the end point of stmt.
?If v has the state .definitely assigned after true expression. at the end
of expr, then it is definitely
assigned on the control flow transfer to while-body, but not definitely
assigned at the end-point of
stmt.
?If v has the state .definitely assigned after false expression. at the
end of expr, then it is definitely
assigned on the control flow transfer to the end point of stmt.
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