Add trailing commas to argument and parameter lists.

docs/language/dartLangSpec.tex

Index: docs/language/dartLangSpec.tex
diff --git a/docs/language/dartLangSpec.tex b/docs/language/dartLangSpec.tex
index 140a8df4fafc328bc0b4fd246f9ad83805d0d7b9..0b76367151cb8dc4d241284cec129433f7401bc4 100644
--- a/docs/language/dartLangSpec.tex
+++ b/docs/language/dartLangSpec.tex
@@ -655,9 +655,11 @@ The body of a function introduces a new scope known as the function's {\em  body
 It is a compile-time error if a formal parameter is declared as a constant variable (\ref{variables}).
 
 \begin{grammar}
-{\bf formalParameterList:}`(' `)';
- `(' normalFormalParameters ( `,'  optionalFormalParameters)? `)';
-  `(' optionalFormalParameters `)'
+{\bf formalParameterList:}
+     `(' `)';
+     `(' normalFormalParameters `,'? `)';
+     `(' normalFormalParameters `,'  optionalFormalParameters `)';
+     `(' optionalFormalParameters `)'
    .
 %\end{grammar}
 %}
@@ -673,18 +675,21 @@ It is a compile-time error if a formal parameter is declared as a constant varia
       normalFormalParameter (`,' normalFormalParameter)*
     .
 
-{\bf optionalFormalParameters:}optionalPositionalFormalParameters;
+{\bf optionalFormalParameters:}
+      optionalPositionalFormalParameters;
       namedFormalParameters
     .
 
 {\bf optionalPositionalFormalParameters:}
-      `[' defaultFormalParameter (`,' defaultFormalParameter)* `]'
+      `[' defaultFormalParameter (`,' defaultFormalParameter)* `,'? `]'
     .
 {\bf namedFormalParameters:}
-      `\{' defaultNamedParameter (`,' defaultNamedParameter)* `\}'
+      `\{' defaultNamedParameter (`,' defaultNamedParameter)* `,'? `\}'
     .
 \end{grammar}
 
+Formal parameter lists allow an optional trailing comma after the last parameter ($`,'?$). A parameter list with such a trailing comma is equivalent in all ways to the same parameter list without the trailing comma. All parameter lists in this specification are shown without a trailing comma, but the rules and semantics apply equally to the corresponding parameter list with a trailing comma.
+
 %Formal parameters are always \FINAL{}.
 %\Q{We're awaiting some data on whether enforcing this would cause widespread pain.}
 %A formal parameter is always considered to be initialized.  \rationale{This is because it will always be initialized by the call - even if it is optional.}
@@ -3608,10 +3613,11 @@ Function invocation involves evaluation of the list of actual arguments to the f
 
 \begin{grammar}
 {\bf arguments:}
-      `(' argumentList? `)'
+      `(' (argumentList  `,'?)? `)'
     .
 
-{\bf argumentList:}namedArgument (`,' namedArgument)*;
+{\bf argumentList:}
+      namedArgument (`,' namedArgument)*;
   %    expressionList ',' spreadArgument;
       expressionList (`,' namedArgument)*
 %      spreadArgument
@@ -3622,6 +3628,8 @@ Function invocation involves evaluation of the list of actual arguments to the f
     .
  \end{grammar}
 
+Argument lists allow an optional trailing comma after the last argument ($`,'?$). An argument list with such a trailing comma is equivalent in all ways to the same parameter list without the trailing comma. All argument lists in this specification are shown without a trailing comma, but the rules and semantics apply equally to the corresponding argument list with a trailing comma.
+
 \LMHash{}
 Evaluation of an actual argument list of the form