[cfe-dev] Qualified and unqualified name lookup and IdResolver

[Sebastian Redl]

On Thu, 4 Dec 2008 17:30:10 -0800, Douglas Gregor <dgregor at apple.com>
wrote:
> The attached patch changes how we perform both qualified and  
> unqualified name lookup in Clang. It represents a significant  
> departure from the approach currently implemented in Clang, but I  
> believe it will have performance and maintainability benefits in the  
> future.
> 
> I propose---and this patch implements---an alternative solution that  
> returns the chain of declarations back to a chain of declarations that  
> occur within the lexical scope of the program. For our function N2::f,  
> the chain for "x" would contain only #1, which is the only "x" within  
> the lexical scope. Essentially, when names get introduced into a scope  
> via a declaration, they are added to the declaration chain for their  
> name; when that scope is destroyed those names are removed from the  
> declaration chain. That way, the declaration chains only contain  
> declarations that can actually be found by unqualified name lookup,  
> and are no deeper than the nesting of lexical scopes.
> 
> For qualified name lookup, each DeclContext has the ability to perform  
> a lookup into the declarations it contains. For example, to find N::x,  
> we would ask the DeclContext represented by N whether it has a name  
> "x" in it. The lookup is performed in an efficient data structure: for  
> < 6 declarations in the DeclContext, it's an array; for more  
> declarations, it's a hash table.
> 

Haven't looked at the patch yet, but I like the concept very much.

Sebastian