diff --git a/proposals/0002-cxx-attributes.md b/proposals/0002-cxx-attributes.md index c493ecc4..32b21c45 100644 --- a/proposals/0002-cxx-attributes.md +++ b/proposals/0002-cxx-attributes.md @@ -124,4 +124,65 @@ Below are a few more examples of C++ attributes that we could support: } } ``` +## Detailed design + +The simplest explanation of this feature is supporting C++11 attribute syntax on +all shared grammar elements between HLSL and C++. This spec attempts to detail +some of the grammar and parsing implications and will specify the process by +which existing attributes will convert to C++ attributes. +### Attribute Parsing + +This proposal introduces new grammar formulations for parsing attributes +matching some formulations from C++ `dcl.attr.grammar`. Specifically: + +```ebnf +attribute-specifier-seq: [ attribute-specifier-seq ], attribute-specifier +attribute-specifier: "[" , "[" , attribute-list , "]" , "]" +attribute-list: [ attribute ] || + attribute-list , "," , [attribute] || + { attribute } || + attribute-list , "," , { attribute } +attribute: attribute-token , [attribute-argument-clause] +attribute-token: identifier || + attribute-scoped-token +attribute-scoped-token: attribute-namespace , "::" , identifier +attribute-namespace: identifier +attribute-argument-clause: "(" , balanced-token-seq , ")" +balanced-token-seq: [ balanced-token ] || + balanced-token-seq , balanced-token +balanced-token: "(" , balanced-token-seq , ")" + "[" , balanced-token-seq , "]" + "{" , balanced-token-seq , "}" +``` + +In contrast to existing HLSL annotations and Microsoft-style attributes, these +attribute identifiers are case-sensitive `identifier` tokens. + + +#### Statements + +```ebnf +statement: [ attribute-specifier-seq ] , expression-statement || + [ attribute-specifier-seq ] , compound-statement || + [ attribute-specifier-seq ] , selection-statement || + [ attribute-specifier-seq ] , iteration-statement || + [ attribute-specifier-seq ] , jump-statement || + declaration-statement + labeled-statement +labeled-statement: [ attribute-specifier-seq ] , "case" , constant-expression , ":" , statement + [ attribute-specifier-seq ] , "default" , ":" , statement +``` + +#### Declarations + +The `attribute-specifier-seq` element supports annotating type declarations. The +following grammar formulations are valid: + +```ebnf +class-key: "class" || "struct" +class-declaration: class-key , attribute-specifier-seq , identifier + +alias-declaration: "using" , identifier , [ attribute-specifier-seq ] , "=" , type-id , ";" +``` +