[PATCH] Support named values in the autocomplete feature.

[Samuel Benzaquen]

================
Comment at: include/clang/ASTMatchers/Dynamic/Parser.h:86
@@ +85,3 @@
+    virtual std::vector<MatcherCompletion>
+    getNamedValueCompletions(llvm::ArrayRef<ArgKind> AcceptedTypes);
+
----------------
Peter Collingbourne wrote:
> This approach requires a bunch of common logic to be duplicated between individual Sema implementations. Instead, you could have a virtual function in this class that returns (a const reference to) a map of named values, which would be called by this function and getNamedValue.
> 
> You might also consider changing the parser API to pass the map separately (along with Sema) to the parser. That way, you could also avoid complicating Sema too much as a result of having to allow completeExpression to take custom Semas.
Having this in the Sema object is following the same logic as having the matchers.
It allows an implementation of it to do whatever it wants. It could be backed by an in-memory std::map, be generated on demand, or by some other source.
Earlier, I added 'RegistrySema' because it was common to use that one.
I was thinking in providing a MappedValueSema, and make both of these mix-ins that the user can add to their implementations.

wrt duplicated logic, I added most of the required logic in the support classes (VariantValue, etc). The implementation of this method of a backing string->value map is just a few lines.

http://reviews.llvm.org/D3509