Merge #176

176: Move completio to ra_analysis r=matklad a=matklad

While we should handle completion for isolated file, it's better
achieved by using empty Analysis, rather than working only with &File:
we need memoization for type inference even inside a single file.

Co-authored-by: Aleksey Kladov <aleksey.kladov@gmail.com>

crates/ra_analysis/src/syntax_ptr.rs

@@ -12,6 +12,7 @@ salsa::query_group! {
     pub(crate) trait SyntaxPtrDatabase: SyntaxDatabase {
         fn resolve_syntax_ptr(ptr: SyntaxPtr) -> SyntaxNode {
             type ResolveSyntaxPtrQuery;
+            // Don't retain syntax trees in memory
             storage volatile;
         }
     }
@@ -83,6 +84,10 @@ impl LocalSyntaxPtr {
                 .unwrap_or_else(|| panic!("can't resolve local ptr to SyntaxNode: {:?}", self))
         }
     }
+
+    pub(crate) fn into_global(self, file_id: FileId) -> SyntaxPtr {
+        SyntaxPtr { file_id, local: self}
+    }
 }