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Change symbolLiteral to match actual implementation, clean up reserved words formatting #1588

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Merged
merged 4 commits into from
Apr 16, 2021
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Change symbolLiteral to match actual implementation, clean up reserved words formatting #1588

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91d367a
Clean up reserved words formatting, change symbolLiteral to match act…
eernstg Apr 15, 2021
5506fed
Correction: now matching actual behavior
eernstg Apr 15, 2021
31438ca
More small corrections
eernstg Apr 15, 2021
f8a8d7f
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eernstg Apr 16, 2021
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106 changes: 70 additions & 36 deletions specification/dartLangSpec.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -8966,30 +8966,28 @@ \subsection{Symbols}
\LMHash{}%
A \IndexCustom{symbol literal}{literal!symbol}
denotes a name that would be either
a valid declaration name or a valid library name in a Dart program.
a valid declaration name, a valid library name, or \VOID.

\begin{grammar}
<symbolLiteral> ::= `#' (<operator> | (<identifier> (`.' <identifier>)*))
<symbolLiteral> ::=
`#' (<identifier> (`.' <identifier>)* | <operator> | \VOID)
\end{grammar}

\LMHash{}%
A symbol literal \code{\#\id} where \id{} is an identifier
that does not begin with an underscore (`\code{\_}'),
evaluates to an instance of \code{Symbol} representing the identifier \id.
All occurrences of \code{\#\id} evaluate to the same instance
\commentary{(symbol instances are canonicalized)},
and no other symbol literals evaluate to that \code{Symbol} instance
or to a \code{Symbol} instance that is equal
(according to the \lit{==} operator \ref{equality}) to that instance.
The static type of a symbol literal is \code{Symbol}.

\LMHash{}%
Let \id{} be an identifier that does not begin with an underscore
(`\code{\_}').
The symbol literal \code{\#\id}
evaluates to an instance of \code{Symbol}
representing the identifier \id.

\LMHash{}%
A symbol literal \code{\#$\id.\id_2\ldots\id_n$}
where $\id{} \ldots \id_n$ are identifiers,
evaluates to an instance of \code{Symbol} representing that particular sequence of identifiers.
All occurrences of \code{\#$\id.\id_2\ldots\id_n$} with the same sequence of identifiers
evaluate to the same instance,
and no other symbol literals evaluate to that \code{Symbol} instance
or to a \code{Symbol} instance that is \lit{==} to that instance.
A symbol literal \code{\#$\id_1$.$\id_2$.$\cdots$.$\id_n$}
where \List{\id}{1}{n} are identifiers
evaluates to an instance of \code{Symbol}
representing that particular sequence of identifiers.
\commentary{%
This kind of symbol literal denotes the name of a library declaration,
as specified in a \synt{libraryName}.
Expand All @@ -8998,18 +8996,39 @@ \subsection{Symbols}
}

\LMHash{}%
A symbol literal \code{\#\metavar{operator}} evaluates to an instance of \code{Symbol}
A symbol literal \code{\#\metavar{op}}
where \metavar{op} is derived from \synt{operator}
evaluates to an instance of \code{Symbol}
representing that particular operator name.
All occurrences of \code{\#\metavar{operator}} evaluate to the same instance,
and no other symbol literals evaluate to that \code{Symbol} instance
or to a \code{Symbol} instance that is \lit{==} to that instance.

\LMHash{}%
A symbol literal \code{\#\_\id}, evaluates to an instance of \code{Symbol}
The symbol literal \code{\#void}
evaluates to an instance of \code{Symbol}
representing the reserved word \VOID.

\LMHash{}%
Assume that the term $t$ is an identifier \id{}
that does not start with an underscore,
that $t$ is \VOID,
that $t$ is a period separated sequence of identifiers
\code{$id_1$.$id_2$.$\cdots$.$id_n$},
or that $t$ is derived from \synt{operator}.
Any two occurrences of \code{\#t} evaluate to the same object
(\commentary{that is, symbol instances are canonicalized}),
and no other symbol literals evaluate to that object,
nor to a \code{Symbol} instance that is equal to that object
according to the \lit{==} operator
(\ref{equality}).

\LMHash{}%
A symbol literal \code{\#\_\id} where \id{} is an identifier
evaluates to an instance of \code{Symbol}
representing the private identifier \code{\_\id} of the containing library.
All occurrences of \code{\#\_\id} \emph{in the same library} evaluate to the same instance,
and no other symbol literals evaluate to that \code{Symbol} instance
or to a \code{Symbol} instance that is \lit{==} to that instance.
All occurrences of \code{\#\_\id} \emph{in the same library} evaluate to
the same object,
and no other symbol literals evaluate to the same object,
nor to a \code{Symbol} instance that is equal to that object
according to the \lit{==} operator.

\LMHash{}%
The objects created by symbol literals all override
Expand Down Expand Up @@ -9043,9 +9062,6 @@ \subsection{Symbols}
convenient substitutes for enums are secondary benefits.%
}

\LMHash{}%
The static type of a symbol literal is \code{Symbol}.


\subsection{Collection Literals}
\LMLabel{collectionLiterals}
Expand Down Expand Up @@ -16048,6 +16064,13 @@ \subsection{Identifier Reference}

<qualifiedName> ::= <typeIdentifier> `.' <identifier>
\alt <typeIdentifier> `.' <typeIdentifier> `.' <identifier>

<LETTER> ::= `a' .. `z'
\alt `A' .. `Z'

<DIGIT> ::= `0' .. `9'

<WHITESPACE> ::= (`\\t' | ` ' | <NEWLINE>)+
\end{grammar}

\LMHash{}%
Expand Down Expand Up @@ -21424,17 +21447,28 @@ \subsubsection{Reserved Words}
\LMLabel{reservedWords}

\LMHash{}%
A \Index{reserved word} may not be used as an identifier; it is a compile-time error if a reserved word is used where an identifier is expected.
A \Index{reserved word} can only be used in the syntactic positions
specified by the grammar.
In particular, a compile-time error occurs if a reserved word is used
where an identifier is expected.

\ASSERT{}, \BREAK{}, \CASE{}, \CATCH{}, \CLASS{}, \CONST{}, \CONTINUE{}, \DEFAULT{}, \DO{}, \ELSE{}, \ENUM{}, \EXTENDS{}, \FALSE{}, \FINAL{}, \FINALLY{}, \FOR{}, \IF{}, \IN{}, \IS{}, \NEW{}, \NULL{}, \RETHROW, \RETURN{}, \SUPER{}, \SWITCH{}, \THIS{}, \THROW{}, \TRUE{}, \TRY{}, \VAR{}, \VOID{}, \WHILE{}, \WITH{}.
\commentary{%
Note that reserved words occur bold and unquoted in grammar rules
(e.g., \ASSERT{})
even though the consistent notation would use quotes
(e.g., \lit{assert}).
This notational abuse occurs because we believe
it makes the grammar rules more readable.%
}

\begin{grammar}
<LETTER> ::= `a' .. `z'
\alt `A' .. `Z'

<DIGIT> ::= `0' .. `9'

<WHITESPACE> ::= (`\\t' | ` ' | <NEWLINE>)+
<reservedWord> ::= \ASSERT{} | \BREAK{} | \CASE{} | \CATCH{} |
\CLASS{} | \CONST{} | \CONTINUE{}
\alt\hspace{-3mm} \DEFAULT{} | \DO{} | \ELSE{} | \ENUM{} | \EXTENDS{} |
\FALSE{} | \FINAL{} | \FINALLY{} | \FOR{} | \IF{} | \IN{} | \IS{}
\alt\hspace{-3mm} \NEW{} | \NULL{} | \RETHROW{} | \RETURN{} | \SUPER{} |
\SWITCH{} | \THIS{} | \THROW{} | \TRUE{} | \TRY{}
\alt\hspace{-3mm} \VAR{} | \VOID{} | \WHILE{} | \WITH{}
\end{grammar}


Expand Down