Slight rewording of compile-time errors for switch cases, for clarity. No semantic change.

docs/language/dartLangSpec.tex

 \documentclass{article}
 \usepackage{epsfig}
 \usepackage{dart}
 \usepackage{bnf}
 \usepackage{hyperref}
 \newcommand{\code}[1]{{\sf #1}}
 \title{Dart Programming Language  Specification \\
 {\large Draft Version 0.61}}
 \author{The Dart Team}
 \begin{document}
 \maketitle
 
-\tableofcontents
+\tableofcontents 

[rmacnak, 2013/10/09 20:54:43]

Stray whitespace.

 
 \newpage
 
 \pagestyle{myheadings}
 \markright{{\bf Draft}  Dart Programming Language Specification {\bf Draft}}
 
 \section{Notes}
 
 Expect the contents and language rules to change over time.
 %Please mail comments to gbracha@google.com.
@@ skipping 2330 matching lines @@
 Metadata consists of a series of annotations, each of which begin with the character @, followed by  a constant expression that starts with an identifier. It is a compile time error if the expression is not one of the following:
 \begin{itemize}
 \item A reference to a compile-time constant variable.
 \item The name of a class.
 \item A call to a constant constructor.
 \end{itemize}
 
 Metadata is associated with the abstract syntax tree of the program construct $p$ that immediately follows the metadata, assuming $p$ is not itself metadata or a comment. Metadata can be retrieved at runtime via a reflective call, provided the annotated program construct $p$ is accessible via reflection.
 
 \commentary{
-Reflective access to metadata is not yet implemented as of the M4 release.
-
 Obviously, metadata can also be retrieved statically by parsing the program and evaluating the constants via a suitable interpreter. In fact many if not most uses of metadata are entirely static.
 }
 
 \rationale{
 It is important that no runtime overhead be incurred by the introduction of metadata that is not actually used. Because metadata only involves constants, the time at which it is computed is irrelevant so that implementations may skip the metadata during ordinary parsing and execution and evaluate it lazily.
 }
 
 \commentary{
 It is possible to associate metadata with constructs that may not be accessible via reflection, such as local variables (though it is conceivable that in the future, richer reflective libraries might provide access to these as well).  This is not as useless as it might seem. As noted above, the data can be retrieved statically if source code is available.
 }
@@ skipping 2387 matching lines @@
 
 {\bf switchCase:}
       label* (\CASE{} expression `{\escapegrammar :}') statements
     .
 
 {\bf defaultCase:}
       label*  \DEFAULT{} `{\escapegrammar :}' statements
     .
  \end{grammar}
  
- Given a switch statement of the form \code{\SWITCH{} ($e$) \{ \CASE{} $label_{11} \ldots label_{1j_1}$ $e_1: s_1 \ldots$  \CASE{} $label_{n1} \ldots label_{nj_n}$ $e_n: s_n$ \DEFAULT{}: $s_{n+1}$ \}} or the form \code{\SWITCH{} ($e$) \{ \CASE{} $label_{11} \ldots label_{1j_1}$ $e_1: s_1 \ldots$  \CASE{} $label_{n1} \ldots label_{nj_n}$ $e_n: s_n$ \}}, it is a compile-time error if the expressions $e_k$ are not compile-time constants for all  $k \in 1..n$.  It is a compile-time error if the values of the expressions $e_k$ are not all instances of the same class $C$ or of a class that implements \cd{int} or \cd{String}, for all $k \in 1..n$. 
+ Given a switch statement of the form \code{\SWITCH{} ($e$) \{ \CASE{} $label_{11} \ldots label_{1j_1}$ $e_1: s_1 \ldots$  \CASE{} $label_{n1} \ldots label_{nj_n}$ $e_n: s_n$ \DEFAULT{}: $s_{n+1}$ \}} or the form \code{\SWITCH{} ($e$) \{ \CASE{} $label_{11} \ldots label_{1j_1}$ $e_1: s_1 \ldots$  \CASE{} $label_{n1} \ldots label_{nj_n}$ $e_n: s_n$ \}}, it is a compile-time error if the expressions $e_k$ are not compile-time constants for all  $k \in 1..n$.  It is a compile-time error if the values of the expressions $e_k$ are not either:
+ \begin{itemize}
+ \item all instances of the same class $C$ or 
+ \item instances of a class that implements \cd{int} or \cd{String}, for all $k \in 1..n$. 

[rmacnak, 2013/10/09 20:54:43]

I read this as allowing mixture of ints and Strings.

Consider
* All instances of a class or classes that implement int
* All instances of a class or classes that implement String

("or classes" covers mixing Smi/Mint/Bigint)

+ \end{itemize}
  
-\commentary{In other words,  all the expressions in the cases evaluate to constants of the exact same user defined class or  are of certain known types.  Note that the values of the expressions are known at compile-time, and are independent of any static type annotations.
+\commentary{In other words,  all the expressions in the cases evaluate to constants of the exact same user defined class or are of certain known types.  Note that the values of the expressions are known at compile-time, and are independent of any static type annotations.
 }
 
-It is a compile-time error if the class $C$ implements the operator $==$ unless the value of the expression is a string or integer.
+It is a compile-time error if the class $C$ has an implementation the operator $==$ other than the one inherited from \code{Object} unless the value of the expression is a string or an integer.

[rmacnak, 2013/10/09 20:54:43]

has an implementation with the operator ==

  
  \rationale{
  The prohibition on user defined equality allows us to implement the switch efficiently for user defined types. We could formulate matching in terms of identity instead with the same efficiency. However, if a type defines an equality operator, programmers would find it quite surprising that equal objects did not match.
  
  }
 
 \commentary{
 The \SWITCH{}  statement should only be used in very limited situations (e.g., interpreters or scanners).  
 }
 
@@ skipping 1294 matching lines @@
 \item The names of compile time constant variables never use lower case letters. If they consist of multiple words, those words are separated by underscores. Examples: PI,  I\_AM\_A\_CONSTANT.
 \item The names of functions (including getters, setters, methods and local or library functions) and non-constant variables begin with a lowercase letter. If the name consists of multiple words, each  word (except the first) begins with an uppercase letter.  No other uppercase letters are used. Examples: camlCase, dart4TheWorld
 \item The names of types (including classes and type aliases) begin with an upper case letter.  If the name consists of multiple words, each  word  begins with an uppercase letter.  No other uppercase letters are used. Examples: CamlCase, Dart4TheWorld.
 \item The names of type variables are short (preferably single letter). Examples: T, S, K, V , E.
 \item The names of libraries or library prefixes never use upper case letters. If they consist of multiple words, those words are separated by underscores. Example: my\_favorite\_library.
 \end{itemize}
 }
 
 
 \end{document}