clang: C++1y deprecated attribute message

[Richard Smith]

On Tue, Jan 28, 2014 at 4:58 PM, Joseph Mansfield <sftrabbit at gmail.com>wrote:

> The attached patch adds support for deprecation messages in C++1y. This is
> my first time hacking with clang so a code review would definitely be
> needed.
>
> As an example of what is now supported:
>
> [[deprecated("use bar instead")]] void foo();
>
> When this function is used, the following warning is emitted:
>
>  warning: 'foo' is deprecated: use bar instead [-Wdeprecated-declarations]
>   foo();
>   ^
>
> Some tests included.
>
> Known potential issues:
> - Attribute parsing currently doesn't seem to distinguish between C++11
> and C++1y attributes.
> - Maybe errors like [[deprecated("foo", "bar")]] would better report "too
> many arguments" than "expected ')'". Not sure about the best way to go
> about this.
>

Thanks for the patch! The code generally looks good from a style
perspective, but please start variable names with a capital letter in new
code (the current codebase is woefully inconsistent, but we're trying to
get new code to follow the style guide). (The style guide also says to
start functions with a lowercase letter, but we're not doing that for
Parse* because it's such a well-established pattern that the inconsistency
would be worse than following the style guide. We'll get around to doing a
mass cleanup of this stuff one day...)

We've been trying to move away from having a collection of different
attribute argument parsing functions, and towards generating the parsing
logic from the Attr.td file -- I'll let Aaron weigh in on whether we want
something like ParseAttributeWithMessageArg or whether we should generalize
and reuse ParseGNUAttributeArgs.

+  if (Tok.isNot(tok::string_literal)) {
+    Diag(Tok, diag::err_expected_string_literal)
+      << /*Source='attribute'*/2
+      << AttrName.getName();
+    SkipUntil(tok::r_paren, StopAtSemi);
+    return;
+  }

This check isn't quite right: there are five different tokens that can
start a string literal (string_literal, wide_string_literal,
utf8_string_literal, ...) -- use isTokenStringLiteral() instead.
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