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Add message to assert in specification.

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R=eernst@google.com

Review URL: https://codereview.chromium.org/2530083002 .
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Lasse R.H. Nielsen 2016-11-28 09:19:28 +01:00
parent 7957a1c256
commit c05eb97461
1 changed files with 11 additions and 6 deletions
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17
docs/language/dartLangSpec.tex
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@ -6593,19 +6593,24 @@ An {\em assert statement} is used to disrupt normal execution if a given boolean
\begin{grammar}
{\bf assertStatement:}
assert `(' expression `)' `{\escapegrammar ;}'
assert `(' expression ( `,` expression )? `)' `{\escapegrammar ;}'
.
\end{grammar}
\LMHash{}
The assert statement has no effect in production mode. In checked mode, execution of an assert statement \code{\ASSERT{}($e$);} proceeds as follows:
An assert statement on the form \code{\ASSERT($e$);)} is equivalent to a statment on the form \code{\ASSERT($e$, null);}.
\LMHash{}
The expression $e$ is evaluated to an object $o$. If the class of $o$ is a subtype of \code{Function} then let $r$ be the result of invoking $o$ with no arguments. Otherwise, let $r$ be $o$.
It is a dynamic type error if $o$ is not of type \code{bool} or of type \code{Function}, or if $r$ is not of type \code{bool}. If $r$ is \FALSE{}, we say that the assertion failed. If $r$ is \TRUE{}, we say that the assertion succeeded. If the assertion succeeded, execution of the assert statement is complete. If the assertion failed, the execution throws (\ref{completion}) an \code{AssertionError} with a stack trace corresponding to the current execution state at the \ASSERT{} statement.
The assert statement has no effect in production mode. In checked mode, execution of an assert statement \code{\ASSERT{}($c$, $e$);} proceeds as follows:
%\Q{Might be cleaner to define it as \code{if (!$e$) \{\THROW{} \NEW{} AssertionError();\}} (in checked mode only).
%What about an error message as part of the assert?}
\LMHash{}
The expression $c$ is evaluated to an object $o$. If the class of $o$ is a subtype of \code{Function} then let $r$ be the result of invoking $o$ with no arguments. Otherwise, let $r$ be $o$.
It is a dynamic type error if $o$ is not of type \code{bool} or of type \code{Function}, or if $r$ is not of type \code{bool}.
If $r$ is \FALSE{}, we say that the assertion failed.
If $r$ is \TRUE{}, we say that the assertion succeeded.
If the assertion succeeded, execution of the assert statement completes normally (\ref{completion}).
If the assertion failed, $e$ is evaluated to an object $m$.
Then the execution of the assert statement throws (\ref{completion}) an \code{AssertionError} containing $m$ and with a stack trace corresponding to the current execution state at the \ASSERT{} statement.
\LMHash{}
It is a static type warning if the type of $e$ may not be assigned to either \code{bool} or $() \rightarrow$ \code{bool}.