Align config's API with usage

The config now is mostly immutable, optimize for that.

22 files changed, 164 insertions, 162 deletions

diff --git a/crates/assists/src/assist_config.rs b/crates/assists/src/assist_config.rs
index c458d9054..4fe8ea761 100644
--- a/crates/assists/src/assist_config.rs
+++ b/crates/assists/src/assist_config.rs
@@ -4,8 +4,7 @@
 //! module, and we use to statically check that we only produce snippet
 //! assists if we are allowed to.
 
-use hir::PrefixKind;
-use ide_db::helpers::insert_use::MergeBehavior;
+use ide_db::helpers::{insert_use::MergeBehavior, SnippetCap};
 
 use crate::AssistKind;
 
@@ -16,35 +15,8 @@ pub struct AssistConfig {
     pub insert_use: InsertUseConfig,
 }
 
-impl AssistConfig {
-    pub fn allow_snippets(&mut self, yes: bool) {
-        self.snippet_cap = if yes { Some(SnippetCap { _private: () }) } else { None }
-    }
-}
-
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub struct SnippetCap {
-    _private: (),
-}
-
-impl Default for AssistConfig {
-    fn default() -> Self {
-        AssistConfig {
-            snippet_cap: Some(SnippetCap { _private: () }),
-            allowed: None,
-            insert_use: InsertUseConfig::default(),
-        }
-    }
-}
-
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub struct InsertUseConfig {
     pub merge: Option<MergeBehavior>,
-    pub prefix_kind: PrefixKind,
-}
-
-impl Default for InsertUseConfig {
-    fn default() -> Self {
-        InsertUseConfig { merge: Some(MergeBehavior::Full), prefix_kind: PrefixKind::Plain }
-    }
+    pub prefix_kind: hir::PrefixKind,
 }
diff --git a/crates/assists/src/assist_context.rs b/crates/assists/src/assist_context.rs
index 4f59d39a9..91cc63427 100644
--- a/crates/assists/src/assist_context.rs
+++ b/crates/assists/src/assist_context.rs
@@ -4,7 +4,10 @@ use std::mem;
 
 use algo::find_covering_element;
 use hir::Semantics;
-use ide_db::base_db::{AnchoredPathBuf, FileId, FileRange};
+use ide_db::{
+    base_db::{AnchoredPathBuf, FileId, FileRange},
+    helpers::SnippetCap,
+};
 use ide_db::{
     label::Label,
     source_change::{FileSystemEdit, SourceChange, SourceFileEdit},
@@ -17,10 +20,7 @@ use syntax::{
 };
 use text_edit::{TextEdit, TextEditBuilder};
 
-use crate::{
-    assist_config::{AssistConfig, SnippetCap},
-    Assist, AssistId, AssistKind, GroupLabel,
-};
+use crate::{assist_config::AssistConfig, Assist, AssistId, AssistKind, GroupLabel};
 
 /// `AssistContext` allows to apply an assist or check if it could be applied.
 ///
diff --git a/crates/assists/src/handlers/generate_function.rs b/crates/assists/src/handlers/generate_function.rs
index f4cf155b6..d169abedb 100644
--- a/crates/assists/src/handlers/generate_function.rs
+++ b/crates/assists/src/handlers/generate_function.rs
@@ -1,5 +1,5 @@
 use hir::HirDisplay;
-use ide_db::base_db::FileId;
+use ide_db::{base_db::FileId, helpers::SnippetCap};
 use rustc_hash::{FxHashMap, FxHashSet};
 use syntax::{
     ast::{
@@ -11,7 +11,6 @@ use syntax::{
 };
 
 use crate::{
-    assist_config::SnippetCap,
     utils::{render_snippet, Cursor},
     AssistContext, AssistId, AssistKind, Assists,
 };
diff --git a/crates/assists/src/lib.rs b/crates/assists/src/lib.rs
index 5e3a1b368..90009c55a 100644
--- a/crates/assists/src/lib.rs
+++ b/crates/assists/src/lib.rs
@@ -24,7 +24,7 @@ use syntax::TextRange;
 
 pub(crate) use crate::assist_context::{AssistContext, Assists};
 
-pub use assist_config::AssistConfig;
+pub use assist_config::{AssistConfig, InsertUseConfig};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum AssistKind {
diff --git a/crates/assists/src/tests.rs b/crates/assists/src/tests.rs
index 21e448fb8..a4c6a7570 100644
--- a/crates/assists/src/tests.rs
+++ b/crates/assists/src/tests.rs
@@ -1,15 +1,29 @@
 mod generated;
 
 use hir::Semantics;
-use ide_db::base_db::{fixture::WithFixture, FileId, FileRange, SourceDatabaseExt};
-use ide_db::source_change::FileSystemEdit;
-use ide_db::RootDatabase;
+use ide_db::{
+    base_db::{fixture::WithFixture, FileId, FileRange, SourceDatabaseExt},
+    helpers::{insert_use::MergeBehavior, SnippetCap},
+    source_change::FileSystemEdit,
+    RootDatabase,
+};
 use syntax::TextRange;
 use test_utils::{assert_eq_text, extract_offset, extract_range};
 
-use crate::{handlers::Handler, Assist, AssistConfig, AssistContext, AssistKind, Assists};
+use crate::{
+    handlers::Handler, Assist, AssistConfig, AssistContext, AssistKind, Assists, InsertUseConfig,
+};
 use stdx::{format_to, trim_indent};
 
+pub(crate) const TEST_CONFIG: AssistConfig = AssistConfig {
+    snippet_cap: SnippetCap::new(true),
+    allowed: None,
+    insert_use: InsertUseConfig {
+        merge: Some(MergeBehavior::Full),
+        prefix_kind: hir::PrefixKind::Plain,
+    },
+};
+
 pub(crate) fn with_single_file(text: &str) -> (RootDatabase, FileId) {
     RootDatabase::with_single_file(text)
 }
@@ -48,14 +62,14 @@ fn check_doc_test(assist_id: &str, before: &str, after: &str) {
     let before = db.file_text(file_id).to_string();
     let frange = FileRange { file_id, range: selection.into() };
 
-    let assist = Assist::get(&db, &AssistConfig::default(), true, frange)
+    let assist = Assist::get(&db, &TEST_CONFIG, true, frange)
         .into_iter()
         .find(|assist| assist.id.0 == assist_id)
         .unwrap_or_else(|| {
             panic!(
                 "\n\nAssist is not applicable: {}\nAvailable assists: {}",
                 assist_id,
-                Assist::get(&db, &AssistConfig::default(), false, frange)
+                Assist::get(&db, &TEST_CONFIG, false, frange)
                     .into_iter()
                     .map(|assist| assist.id.0)
                     .collect::<Vec<_>>()
@@ -89,7 +103,7 @@ fn check(handler: Handler, before: &str, expected: ExpectedResult, assist_label:
     let frange = FileRange { file_id: file_with_caret_id, range: range_or_offset.into() };
 
     let sema = Semantics::new(&db);
-    let config = AssistConfig::default();
+    let config = TEST_CONFIG;
     let ctx = AssistContext::new(sema, &config, frange);
     let mut acc = Assists::new(&ctx, true);
     handler(&mut acc, &ctx);
@@ -156,7 +170,7 @@ fn assist_order_field_struct() {
     let (before_cursor_pos, before) = extract_offset(before);
     let (db, file_id) = with_single_file(&before);
     let frange = FileRange { file_id, range: TextRange::empty(before_cursor_pos) };
-    let assists = Assist::get(&db, &AssistConfig::default(), false, frange);
+    let assists = Assist::get(&db, &TEST_CONFIG, false, frange);
     let mut assists = assists.iter();
 
     assert_eq!(assists.next().expect("expected assist").label, "Change visibility to pub(crate)");
@@ -176,7 +190,7 @@ fn assist_order_if_expr() {
     let (range, before) = extract_range(before);
     let (db, file_id) = with_single_file(&before);
     let frange = FileRange { file_id, range };
-    let assists = Assist::get(&db, &AssistConfig::default(), false, frange);
+    let assists = Assist::get(&db, &TEST_CONFIG, false, frange);
     let mut assists = assists.iter();
 
     assert_eq!(assists.next().expect("expected assist").label, "Extract into variable");
@@ -198,7 +212,7 @@ fn assist_filter_works() {
     let frange = FileRange { file_id, range };
 
     {
-        let mut cfg = AssistConfig::default();
+        let mut cfg = TEST_CONFIG;
         cfg.allowed = Some(vec![AssistKind::Refactor]);
 
         let assists = Assist::get(&db, &cfg, false, frange);
@@ -209,7 +223,7 @@ fn assist_filter_works() {
     }
 
     {
-        let mut cfg = AssistConfig::default();
+        let mut cfg = TEST_CONFIG;
         cfg.allowed = Some(vec![AssistKind::RefactorExtract]);
         let assists = Assist::get(&db, &cfg, false, frange);
         assert_eq!(assists.len(), 1);
@@ -219,7 +233,7 @@ fn assist_filter_works() {
     }
 
     {
-        let mut cfg = AssistConfig::default();
+        let mut cfg = TEST_CONFIG;
         cfg.allowed = Some(vec![AssistKind::QuickFix]);
         let assists = Assist::get(&db, &cfg, false, frange);
         assert!(assists.is_empty(), "All asserts but quickfixes should be filtered out");
diff --git a/crates/assists/src/utils.rs b/crates/assists/src/utils.rs
index 8212cd129..9ea96eb73 100644
--- a/crates/assists/src/utils.rs
+++ b/crates/assists/src/utils.rs
@@ -4,7 +4,7 @@ pub(crate) mod import_assets;
 use std::ops;
 
 use hir::HasSource;
-use ide_db::RootDatabase;
+use ide_db::{helpers::SnippetCap, RootDatabase};
 use itertools::Itertools;
 use syntax::{
     ast::edit::AstNodeEdit,
@@ -16,10 +16,7 @@ use syntax::{
     SyntaxNode, TextSize, T,
 };
 
-use crate::{
-    assist_config::SnippetCap,
-    ast_transform::{self, AstTransform, QualifyPaths, SubstituteTypeParams},
-};
+use crate::ast_transform::{self, AstTransform, QualifyPaths, SubstituteTypeParams};
 
 pub(crate) fn unwrap_trivial_block(block: ast::BlockExpr) -> ast::Expr {
     extract_trivial_expression(&block)
diff --git a/crates/completion/src/completions/postfix.rs b/crates/completion/src/completions/postfix.rs
index 3883d6d21..4888f518a 100644
--- a/crates/completion/src/completions/postfix.rs
+++ b/crates/completion/src/completions/postfix.rs
@@ -2,7 +2,7 @@
 
 mod format_like;
 
-use ide_db::ty_filter::TryEnum;
+use ide_db::{helpers::SnippetCap, ty_filter::TryEnum};
 use syntax::{
     ast::{self, AstNode, AstToken},
     SyntaxKind::{BLOCK_EXPR, EXPR_STMT},
@@ -10,9 +10,8 @@ use syntax::{
 };
 use text_edit::TextEdit;
 
-use self::format_like::add_format_like_completions;
 use crate::{
-    config::SnippetCap,
+    completions::postfix::format_like::add_format_like_completions,
     context::CompletionContext,
     item::{Builder, CompletionKind},
     CompletionItem, CompletionItemKind, Completions,
diff --git a/crates/completion/src/completions/postfix/format_like.rs b/crates/completion/src/completions/postfix/format_like.rs
index def4b13fb..3afc63021 100644
--- a/crates/completion/src/completions/postfix/format_like.rs
+++ b/crates/completion/src/completions/postfix/format_like.rs
@@ -14,12 +14,11 @@
 //   + `logw` -> `log::warn!(...)`
 //   + `loge` -> `log::error!(...)`
 
-use crate::{
-    completions::postfix::postfix_snippet, config::SnippetCap, context::CompletionContext,
-    Completions,
-};
+use ide_db::helpers::SnippetCap;
 use syntax::ast::{self, AstToken};
 
+use crate::{completions::postfix::postfix_snippet, context::CompletionContext, Completions};
+
 /// Mapping ("postfix completion item" => "macro to use")
 static KINDS: &[(&str, &str)] = &[
     ("format", "format!"),
diff --git a/crates/completion/src/completions/snippet.rs b/crates/completion/src/completions/snippet.rs
index 842590130..b5e704696 100644
--- a/crates/completion/src/completions/snippet.rs
+++ b/crates/completion/src/completions/snippet.rs
@@ -1,8 +1,10 @@
 //! This file provides snippet completions, like `pd` => `eprintln!(...)`.
 
+use ide_db::helpers::SnippetCap;
+
 use crate::{
-    config::SnippetCap, item::Builder, CompletionContext, CompletionItem, CompletionItemKind,
-    CompletionKind, Completions,
+    item::Builder, CompletionContext, CompletionItem, CompletionItemKind, CompletionKind,
+    Completions,
 };
 
 fn snippet(ctx: &CompletionContext, cap: SnippetCap, label: &str, snippet: &str) -> Builder {
diff --git a/crates/completion/src/completions/unqualified_path.rs b/crates/completion/src/completions/unqualified_path.rs
index 896f167ff..2da21b5c2 100644
--- a/crates/completion/src/completions/unqualified_path.rs
+++ b/crates/completion/src/completions/unqualified_path.rs
@@ -192,12 +192,14 @@ mod tests {
     use test_utils::mark;
 
     use crate::{
-        test_utils::{check_edit, check_edit_with_config, completion_list_with_config},
+        test_utils::{
+            check_edit, check_edit_with_config, completion_list_with_config, TEST_CONFIG,
+        },
         CompletionConfig, CompletionKind,
     };
 
     fn check(ra_fixture: &str, expect: Expect) {
-        check_with_config(CompletionConfig::default(), ra_fixture, expect);
+        check_with_config(TEST_CONFIG, ra_fixture, expect);
     }
 
     fn check_with_config(config: CompletionConfig, ra_fixture: &str, expect: Expect) {
@@ -205,10 +207,6 @@ mod tests {
         expect.assert_eq(&actual)
     }
 
-    fn fuzzy_completion_config() -> CompletionConfig {
-        CompletionConfig::default()
-    }
-
     #[test]
     fn self_fulfilling_completion() {
         mark::check!(self_fulfilling_completion);
@@ -832,7 +830,7 @@ impl My<|>
     #[test]
     fn function_fuzzy_completion() {
         check_edit_with_config(
-            fuzzy_completion_config(),
+            TEST_CONFIG,
             "stdin",
             r#"
 //- /lib.rs crate:dep
@@ -858,7 +856,7 @@ fn main() {
     #[test]
     fn macro_fuzzy_completion() {
         check_edit_with_config(
-            fuzzy_completion_config(),
+            TEST_CONFIG,
             "macro_with_curlies!",
             r#"
 //- /lib.rs crate:dep
@@ -886,7 +884,7 @@ fn main() {
     #[test]
     fn struct_fuzzy_completion() {
         check_edit_with_config(
-            fuzzy_completion_config(),
+            TEST_CONFIG,
             "ThirdStruct",
             r#"
 //- /lib.rs crate:dep
@@ -917,7 +915,7 @@ fn main() {
     fn fuzzy_completions_come_in_specific_order() {
         mark::check!(certain_fuzzy_order_test);
         check_with_config(
-            fuzzy_completion_config(),
+            TEST_CONFIG,
             r#"
 //- /lib.rs crate:dep
 pub struct FirstStruct;
diff --git a/crates/completion/src/config.rs b/crates/completion/src/config.rs
index 9f82b0346..b4439b7d1 100644
--- a/crates/completion/src/config.rs
+++ b/crates/completion/src/config.rs
@@ -4,7 +4,7 @@
 //! module, and we use to statically check that we only produce snippet
 //! completions if we are allowed to.
 
-use ide_db::helpers::insert_use::MergeBehavior;
+use ide_db::helpers::{insert_use::MergeBehavior, SnippetCap};
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct CompletionConfig {
@@ -15,27 +15,3 @@ pub struct CompletionConfig {
     pub snippet_cap: Option<SnippetCap>,
     pub merge: Option<MergeBehavior>,
 }
-
-impl CompletionConfig {
-    pub fn allow_snippets(&mut self, yes: bool) {
-        self.snippet_cap = if yes { Some(SnippetCap { _private: () }) } else { None }
-    }
-}
-
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub struct SnippetCap {
-    _private: (),
-}
-
-impl Default for CompletionConfig {
-    fn default() -> Self {
-        CompletionConfig {
-            enable_postfix_completions: true,
-            enable_autoimport_completions: true,
-            add_call_parenthesis: true,
-            add_call_argument_snippets: true,
-            snippet_cap: Some(SnippetCap { _private: () }),
-            merge: Some(MergeBehavior::Full),
-        }
-    }
-}
diff --git a/crates/completion/src/item.rs b/crates/completion/src/item.rs
index 65f8353e7..7087fae37 100644
--- a/crates/completion/src/item.rs
+++ b/crates/completion/src/item.rs
@@ -5,13 +5,11 @@ use std::fmt;
 use hir::{Documentation, ModPath, Mutability};
 use ide_db::helpers::{
     insert_use::{self, ImportScope, MergeBehavior},
-    mod_path_to_ast,
+    mod_path_to_ast, SnippetCap,
 };
 use syntax::{algo, TextRange};
 use text_edit::TextEdit;
 
-use crate::config::SnippetCap;
-
 /// `CompletionItem` describes a single completion variant in the editor pop-up.
 /// It is basically a POD with various properties. To construct a
 /// `CompletionItem`, use `new` method and the `Builder` struct.
diff --git a/crates/completion/src/lib.rs b/crates/completion/src/lib.rs
index 366aced71..3c7d5a46c 100644
--- a/crates/completion/src/lib.rs
+++ b/crates/completion/src/lib.rs
@@ -158,8 +158,7 @@ pub fn resolve_completion_edits(
 
 #[cfg(test)]
 mod tests {
-    use crate::config::CompletionConfig;
-    use crate::test_utils;
+    use crate::test_utils::{self, TEST_CONFIG};
 
     struct DetailAndDocumentation<'a> {
         detail: &'a str,
@@ -168,7 +167,7 @@ mod tests {
 
     fn check_detail_and_documentation(ra_fixture: &str, expected: DetailAndDocumentation) {
         let (db, position) = test_utils::position(ra_fixture);
-        let config = CompletionConfig::default();
+        let config = TEST_CONFIG;
         let completions: Vec<_> = crate::completions(&db, &config, position).unwrap().into();
         for item in completions {
             if item.detail() == Some(expected.detail) {
@@ -183,7 +182,7 @@ mod tests {
 
     fn check_no_completion(ra_fixture: &str) {
         let (db, position) = test_utils::position(ra_fixture);
-        let config = CompletionConfig::default();
+        let config = TEST_CONFIG;
 
         let completions: Option<Vec<String>> = crate::completions(&db, &config, position)
             .and_then(|completions| {
diff --git a/crates/completion/src/render.rs b/crates/completion/src/render.rs
index ac0b2a513..7554c1565 100644
--- a/crates/completion/src/render.rs
+++ b/crates/completion/src/render.rs
@@ -11,13 +11,13 @@ pub(crate) mod type_alias;
 mod builder_ext;
 
 use hir::{Documentation, HasAttrs, HirDisplay, Mutability, ScopeDef, Type};
-use ide_db::RootDatabase;
+use ide_db::{helpers::SnippetCap, RootDatabase};
 use syntax::TextRange;
 use test_utils::mark;
 
 use crate::{
-    config::SnippetCap, item::ImportEdit, CompletionContext, CompletionItem, CompletionItemKind,
-    CompletionKind, CompletionScore,
+    item::ImportEdit, CompletionContext, CompletionItem, CompletionItemKind, CompletionKind,
+    CompletionScore,
 };
 
 use crate::render::{enum_variant::render_variant, function::render_fn, macro_::render_macro};
@@ -320,8 +320,8 @@ mod tests {
     use test_utils::mark;
 
     use crate::{
-        test_utils::{check_edit, do_completion, get_all_items},
-        CompletionConfig, CompletionKind, CompletionScore,
+        test_utils::{check_edit, do_completion, get_all_items, TEST_CONFIG},
+        CompletionKind, CompletionScore,
     };
 
     fn check(ra_fixture: &str, expect: Expect) {
@@ -338,7 +338,7 @@ mod tests {
             }
         }
 
-        let mut completions = get_all_items(CompletionConfig::default(), ra_fixture);
+        let mut completions = get_all_items(TEST_CONFIG, ra_fixture);
         completions.sort_by_key(|it| (Reverse(it.score()), it.label().to_string()));
         let actual = completions
             .into_iter()
diff --git a/crates/completion/src/render/function.rs b/crates/completion/src/render/function.rs
index 081be14f4..7b2f62b4b 100644
--- a/crates/completion/src/render/function.rs
+++ b/crates/completion/src/render/function.rs
@@ -113,7 +113,7 @@ mod tests {
     use test_utils::mark;
 
     use crate::{
-        test_utils::{check_edit, check_edit_with_config},
+        test_utils::{check_edit, check_edit_with_config, TEST_CONFIG},
         CompletionConfig,
     };
 
@@ -211,7 +211,7 @@ fn main() { S::foo(${1:&self})$0 }
     fn suppress_arg_snippets() {
         mark::check!(suppress_arg_snippets);
         check_edit_with_config(
-            CompletionConfig { add_call_argument_snippets: false, ..CompletionConfig::default() },
+            CompletionConfig { add_call_argument_snippets: false, ..TEST_CONFIG },
             "with_args",
             r#"
 fn with_args(x: i32, y: String) {}
diff --git a/crates/completion/src/render/pattern.rs b/crates/completion/src/render/pattern.rs
index a3b6a3cac..61d8a17e5 100644
--- a/crates/completion/src/render/pattern.rs
+++ b/crates/completion/src/render/pattern.rs
@@ -1,12 +1,10 @@
 //! Renderer for patterns.
 
 use hir::{db::HirDatabase, HasAttrs, HasVisibility, Name, StructKind};
+use ide_db::helpers::SnippetCap;
 use itertools::Itertools;
 
-use crate::{
-    config::SnippetCap, item::CompletionKind, render::RenderContext, CompletionItem,
-    CompletionItemKind,
-};
+use crate::{item::CompletionKind, render::RenderContext, CompletionItem, CompletionItemKind};
 
 fn visible_fields(
     ctx: &RenderContext<'_>,
diff --git a/crates/completion/src/test_utils.rs b/crates/completion/src/test_utils.rs
index eb0c16f52..b5e296777 100644
--- a/crates/completion/src/test_utils.rs
+++ b/crates/completion/src/test_utils.rs
@@ -1,8 +1,11 @@
 //! Runs completion for testing purposes.
 
 use hir::Semantics;
-use ide_db::base_db::{fixture::ChangeFixture, FileLoader, FilePosition};
-use ide_db::RootDatabase;
+use ide_db::{
+    base_db::{fixture::ChangeFixture, FileLoader, FilePosition},
+    helpers::{insert_use::MergeBehavior, SnippetCap},
+    RootDatabase,
+};
 use itertools::Itertools;
 use stdx::{format_to, trim_indent};
 use syntax::{AstNode, NodeOrToken, SyntaxElement};
@@ -10,6 +13,15 @@ use test_utils::{assert_eq_text, RangeOrOffset};
 
 use crate::{item::CompletionKind, CompletionConfig, CompletionItem};
 
+pub(crate) const TEST_CONFIG: CompletionConfig = CompletionConfig {
+    enable_postfix_completions: true,
+    enable_autoimport_completions: true,
+    add_call_parenthesis: true,
+    add_call_argument_snippets: true,
+    snippet_cap: SnippetCap::new(true),
+    merge: Some(MergeBehavior::Full),
+};
+
 /// Creates analysis from a multi-file fixture, returns positions marked with <|>.
 pub(crate) fn position(ra_fixture: &str) -> (RootDatabase, FilePosition) {
     let change_fixture = ChangeFixture::parse(ra_fixture);
@@ -24,7 +36,7 @@ pub(crate) fn position(ra_fixture: &str) -> (RootDatabase, FilePosition) {
 }
 
 pub(crate) fn do_completion(code: &str, kind: CompletionKind) -> Vec<CompletionItem> {
-    do_completion_with_config(CompletionConfig::default(), code, kind)
+    do_completion_with_config(TEST_CONFIG, code, kind)
 }
 
 pub(crate) fn do_completion_with_config(
@@ -39,7 +51,7 @@ pub(crate) fn do_completion_with_config(
 }
 
 pub(crate) fn completion_list(code: &str, kind: CompletionKind) -> String {
-    completion_list_with_config(CompletionConfig::default(), code, kind)
+    completion_list_with_config(TEST_CONFIG, code, kind)
 }
 
 pub(crate) fn completion_list_with_config(
@@ -76,7 +88,7 @@ fn monospace_width(s: &str) -> usize {
 }
 
 pub(crate) fn check_edit(what: &str, ra_fixture_before: &str, ra_fixture_after: &str) {
-    check_edit_with_config(CompletionConfig::default(), what, ra_fixture_before, ra_fixture_after)
+    check_edit_with_config(TEST_CONFIG, what, ra_fixture_before, ra_fixture_after)
 }
 
 pub(crate) fn check_edit_with_config(
diff --git a/crates/ide/src/lib.rs b/crates/ide/src/lib.rs
index 72c8bfd09..cea2a13c8 100644
--- a/crates/ide/src/lib.rs
+++ b/crates/ide/src/lib.rs
@@ -80,7 +80,7 @@ pub use crate::{
         HighlightedRange,
     },
 };
-pub use assists::{Assist, AssistConfig, AssistId, AssistKind};
+pub use assists::{Assist, AssistConfig, AssistId, AssistKind, InsertUseConfig};
 pub use completion::{
     CompletionConfig, CompletionItem, CompletionItemKind, CompletionScore, ImportEdit,
     InsertTextFormat,
diff --git a/crates/ide_db/src/helpers.rs b/crates/ide_db/src/helpers.rs
index d988588ff..e3e5670f1 100644
--- a/crates/ide_db/src/helpers.rs
+++ b/crates/ide_db/src/helpers.rs
@@ -1,9 +1,10 @@
 //! A module with ide helpers for high-level ide features.
-use crate::RootDatabase;
+pub mod insert_use;
+
 use hir::{Crate, Enum, Module, ScopeDef, Semantics, Trait};
 use syntax::ast::{self, make};
 
-pub mod insert_use;
+use crate::RootDatabase;
 
 /// Converts the mod path struct into its ast representation.
 pub fn mod_path_to_ast(path: &hir::ModPath) -> ast::Path {
@@ -201,3 +202,18 @@ pub use prelude::*;
         Some(def)
     }
 }
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct SnippetCap {
+    _private: (),
+}
+
+impl SnippetCap {
+    pub const fn new(allow_snippets: bool) -> Option<SnippetCap> {
+        if allow_snippets {
+            Some(SnippetCap { _private: () })
+        } else {
+            None
+        }
+    }
+}
diff --git a/crates/rust-analyzer/src/cli/analysis_bench.rs b/crates/rust-analyzer/src/cli/analysis_bench.rs
index 5a8484c62..7d3fda7a8 100644
--- a/crates/rust-analyzer/src/cli/analysis_bench.rs
+++ b/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)
                     });
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index ce9526315..e3ba81ac6 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -11,8 +11,11 @@ use std::{convert::TryFrom, ffi::OsString, path::PathBuf};
 
 use flycheck::FlycheckConfig;
 use hir::PrefixKind;
-use ide::{AssistConfig, CompletionConfig, DiagnosticsConfig, HoverConfig, InlayHintsConfig};
-use ide_db::helpers::insert_use::MergeBehavior;
+use ide::{
+    AssistConfig, CompletionConfig, DiagnosticsConfig, HoverConfig, InlayHintsConfig,
+    InsertUseConfig,
+};
+use ide_db::helpers::{insert_use::MergeBehavior, SnippetCap};
 use itertools::Itertools;
 use lsp_types::{ClientCapabilities, MarkupKind};
 use project_model::{CargoConfig, ProjectJson, ProjectJsonData, ProjectManifest};
@@ -534,37 +537,39 @@ impl Config {
         }
     }
     pub fn completion(&self) -> CompletionConfig {
-        let mut res = CompletionConfig::default();
-        res.enable_postfix_completions = self.data.completion_postfix_enable;
-        res.enable_autoimport_completions =
-            self.data.completion_autoimport_enable && completion_item_edit_resolve(&self.caps);
-        res.add_call_parenthesis = self.data.completion_addCallParenthesis;
-        res.add_call_argument_snippets = self.data.completion_addCallArgumentSnippets;
-        res.merge = self.merge_behavior();
-
-        res.allow_snippets(try_or!(
-            self.caps
-                .text_document
-                .as_ref()?
-                .completion
-                .as_ref()?
-                .completion_item
-                .as_ref()?
-                .snippet_support?,
-            false
-        ));
-        res
+        CompletionConfig {
+            enable_postfix_completions: self.data.completion_postfix_enable,
+            enable_autoimport_completions: self.data.completion_autoimport_enable
+                && completion_item_edit_resolve(&self.caps),
+            add_call_parenthesis: self.data.completion_addCallParenthesis,
+            add_call_argument_snippets: self.data.completion_addCallArgumentSnippets,
+            merge: self.merge_behavior(),
+            snippet_cap: SnippetCap::new(try_or!(
+                self.caps
+                    .text_document
+                    .as_ref()?
+                    .completion
+                    .as_ref()?
+                    .completion_item
+                    .as_ref()?
+                    .snippet_support?,
+                false
+            )),
+        }
     }
     pub fn assist(&self) -> AssistConfig {
-        let mut res = AssistConfig::default();
-        res.insert_use.merge = self.merge_behavior();
-        res.insert_use.prefix_kind = match self.data.assist_importPrefix {
-            ImportPrefixDef::Plain => PrefixKind::Plain,
-            ImportPrefixDef::ByCrate => PrefixKind::ByCrate,
-            ImportPrefixDef::BySelf => PrefixKind::BySelf,
-        };
-        res.allow_snippets(self.experimental("snippetTextEdit"));
-        res
+        AssistConfig {
+            snippet_cap: SnippetCap::new(self.experimental("snippetTextEdit")),
+            allowed: None,
+            insert_use: InsertUseConfig {
+                merge: self.merge_behavior(),
+                prefix_kind: match self.data.assist_importPrefix {
+                    ImportPrefixDef::Plain => PrefixKind::Plain,
+                    ImportPrefixDef::ByCrate => PrefixKind::ByCrate,
+                    ImportPrefixDef::BySelf => PrefixKind::BySelf,
+                },
+            },
+        }
     }
     pub fn call_info_full(&self) -> bool {
         self.data.callInfo_full
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index a5f7e3af7..bb221c1d1 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -850,6 +850,7 @@ pub(crate) fn markup_content(markup: Markup) -> lsp_types::MarkupContent {
 #[cfg(test)]
 mod tests {
     use ide::Analysis;
+    use ide_db::helpers::SnippetCap;
 
     use super::*;
 
@@ -868,7 +869,14 @@ mod tests {
         let (analysis, file_id) = Analysis::from_single_file(text);
         let completions: Vec<(String, Option<String>)> = analysis
             .completions(
-                &ide::CompletionConfig::default(),
+                &ide::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,
+                },
                 ide_db::base_db::FilePosition { file_id, offset },
             )
             .unwrap()