Align config's API with usage

The config now is mostly immutable, optimize for that.

crates/rust-analyzer/src/cli/analysis_bench.rs

@@ -6,9 +6,12 @@ use anyhow::{bail, format_err, Result};
 use ide::{
     Analysis, AnalysisHost, Change, CompletionConfig, DiagnosticsConfig, FilePosition, LineCol,
 };
-use ide_db::base_db::{
-    salsa::{Database, Durability},
-    FileId,
+use ide_db::{
+    base_db::{
+        salsa::{Database, Durability},
+        FileId,
+    },
+    helpers::SnippetCap,
 };
 use vfs::AbsPathBuf;
 
@@ -87,7 +90,14 @@ impl BenchCmd {
                 let file_position = FilePosition { file_id, offset };
 
                 if is_completion {
-                    let options = CompletionConfig::default();
+                    let options = CompletionConfig {
+                        enable_postfix_completions: true,
+                        enable_autoimport_completions: true,
+                        add_call_parenthesis: true,
+                        add_call_argument_snippets: true,
+                        snippet_cap: SnippetCap::new(true),
+                        merge: None,
+                    };
                     let res = do_work(&mut host, file_id, |analysis| {
                         analysis.completions(&options, file_position)
                     });