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Revise static typecheck rules for for-in.

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BUG=
R=paulberry@google.com

Review URL: https://codereview.chromium.org//1184183010.
This commit is contained in:
Gilad Bracha 2015-06-15 17:50:37 -07:00
parent b34c19d0ce
commit f71b48a041
1 changed files with 1 additions and 11 deletions
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12
docs/language/dartLangSpec.tex
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@ -5683,18 +5683,8 @@ var n0 = $e$.iterator;
$s$
\}
\end{dartCode}
where \code{n0} is an identifier that does not occur anywhere in the program.
where \code{n0} is an identifier that does not occur anywhere in the program, except that for purposes of static typechecking, it is checked under the assumption that $n0$ is declared to be of type $T$, where $T$ is the static type of $e.iterator$.
\commentary{
Note that in fact, using a \CONST{} variable would give rise to a compile time error since \cd{n0.current} is not a constant expression.
}
It is a static warning if the static type of $e$ does not have a member \cd{iterator}. It is a static warning if the static type of \cd{$e$.iterator} does not have a method \cd{moveNext}. It is a static warning if static return type of \cd{$e$.iterator.moveNext()} is not assignable to the static type of \cd{id}.
\commentary {
One might have required that \cd{n0} had type \cd{Iterable$<T>$} where $T$ was the static type of \cd{id}. However, that would cause failure in checked mode if $e$ was merely emulating the \cd{Iterable} interface.
}
\subsubsection{Asynchronous For-in}