1 //! This module contains functions to suggest names for expressions, functions and other items
4 use ide_db::RootDatabase;
5 use itertools::Itertools;
6 use stdx::to_lower_snake_case;
9 match_ast, AstNode, SmolStr,
12 /// Trait names, that will be ignored when in `impl Trait` and `dyn Trait`
13 const USELESS_TRAITS: &[&str] = &["Send", "Sync", "Copy", "Clone", "Eq", "PartialEq"];
15 /// Identifier names that won't be suggested, ever
17 /// **NOTE**: they all must be snake lower case
18 const USELESS_NAMES: &[&str] =
19 &["new", "default", "option", "some", "none", "ok", "err", "str", "string"];
21 /// Generic types replaced by their first argument
24 /// `Option<Name>` -> `Name`
25 /// `Result<User, Error>` -> `User`
26 const WRAPPER_TYPES: &[&str] = &["Box", "Option", "Result"];
28 /// Prefixes to strip from methods names
31 /// `vec.as_slice()` -> `slice`
32 /// `args.into_config()` -> `config`
33 /// `bytes.to_vec()` -> `vec`
34 const USELESS_METHOD_PREFIXES: &[&str] = &["into_", "as_", "to_"];
36 /// Useless methods that are stripped from expression
39 /// `var.name().to_string()` -> `var.name()`
40 const USELESS_METHODS: &[&str] = &[
61 pub(crate) fn for_generic_parameter(ty: &ast::ImplTraitType) -> SmolStr {
64 .and_then(|bounds| bounds.syntax().text().char_at(0.into()))
66 c.encode_utf8(&mut [0; 4]).into()
69 /// Suggest name of variable for given expression
71 /// **NOTE**: it is caller's responsibility to guarantee uniqueness of the name.
72 /// I.e. it doesn't look for names in scope.
74 /// # Current implementation
76 /// In current implementation, the function tries to get the name from
77 /// the following sources:
79 /// * if expr is an argument to function/method, use parameter name
80 /// * if expr is a function/method call, use function name
81 /// * expression type name if it exists (E.g. `()`, `fn() -> ()` or `!` do not have names)
82 /// * fallback: `var_name`
84 /// It also applies heuristics to filter out less informative names
86 /// Currently it sticks to the first name found.
87 // FIXME: Microoptimize and return a `SmolStr` here.
88 pub(crate) fn for_variable(expr: &ast::Expr, sema: &Semantics<'_, RootDatabase>) -> String {
89 // `from_param` does not benefit from stripping
90 // it need the largest context possible
91 // so we check firstmost
92 if let Some(name) = from_param(expr, sema) {
96 let mut next_expr = Some(expr.clone());
97 while let Some(expr) = next_expr {
99 from_call(&expr).or_else(|| from_type(&expr, sema)).or_else(|| from_field_name(&expr));
100 if let Some(name) = name {
105 ast::Expr::RefExpr(inner) => next_expr = inner.expr(),
106 ast::Expr::BoxExpr(inner) => next_expr = inner.expr(),
107 ast::Expr::AwaitExpr(inner) => next_expr = inner.expr(),
108 // ast::Expr::BlockExpr(block) => expr = block.tail_expr(),
109 ast::Expr::CastExpr(inner) => next_expr = inner.expr(),
110 ast::Expr::MethodCallExpr(method) if is_useless_method(&method) => {
111 next_expr = method.receiver();
113 ast::Expr::ParenExpr(inner) => next_expr = inner.expr(),
114 ast::Expr::TryExpr(inner) => next_expr = inner.expr(),
115 ast::Expr::PrefixExpr(prefix) if prefix.op_kind() == Some(ast::UnaryOp::Deref) => {
116 next_expr = prefix.expr()
122 "var_name".to_string()
125 fn normalize(name: &str) -> Option<String> {
126 let name = to_lower_snake_case(name);
128 if USELESS_NAMES.contains(&name.as_str()) {
132 if !is_valid_name(&name) {
139 fn is_valid_name(name: &str) -> bool {
140 match ide_db::syntax_helpers::LexedStr::single_token(name) {
141 Some((syntax::SyntaxKind::IDENT, _error)) => true,
146 fn is_useless_method(method: &ast::MethodCallExpr) -> bool {
147 let ident = method.name_ref().and_then(|it| it.ident_token());
150 Some(ident) => USELESS_METHODS.contains(&ident.text()),
155 fn from_call(expr: &ast::Expr) -> Option<String> {
156 from_func_call(expr).or_else(|| from_method_call(expr))
159 fn from_func_call(expr: &ast::Expr) -> Option<String> {
160 let call = match expr {
161 ast::Expr::CallExpr(call) => call,
164 let func = match call.expr()? {
165 ast::Expr::PathExpr(path) => path,
168 let ident = func.path()?.segment()?.name_ref()?.ident_token()?;
169 normalize(ident.text())
172 fn from_method_call(expr: &ast::Expr) -> Option<String> {
173 let method = match expr {
174 ast::Expr::MethodCallExpr(call) => call,
177 let ident = method.name_ref()?.ident_token()?;
178 let mut name = ident.text();
180 if USELESS_METHODS.contains(&name) {
184 for prefix in USELESS_METHOD_PREFIXES {
185 if let Some(suffix) = name.strip_prefix(prefix) {
194 fn from_param(expr: &ast::Expr, sema: &Semantics<'_, RootDatabase>) -> Option<String> {
195 let arg_list = expr.syntax().parent().and_then(ast::ArgList::cast)?;
196 let args_parent = arg_list.syntax().parent()?;
197 let func = match_ast! {
199 ast::CallExpr(call) => {
200 let func = call.expr()?;
201 let func_ty = sema.type_of_expr(&func)?.adjusted();
202 func_ty.as_callable(sema.db)?
204 ast::MethodCallExpr(method) => sema.resolve_method_call_as_callable(&method)?,
209 let (idx, _) = arg_list.args().find_position(|it| it == expr).unwrap();
210 let (pat, _) = func.params(sema.db).into_iter().nth(idx)?;
211 let pat = match pat? {
212 either::Either::Right(pat) => pat,
215 let name = var_name_from_pat(&pat)?;
216 normalize(&name.to_string())
219 fn var_name_from_pat(pat: &ast::Pat) -> Option<ast::Name> {
221 ast::Pat::IdentPat(var) => var.name(),
222 ast::Pat::RefPat(ref_pat) => var_name_from_pat(&ref_pat.pat()?),
223 ast::Pat::BoxPat(box_pat) => var_name_from_pat(&box_pat.pat()?),
228 fn from_type(expr: &ast::Expr, sema: &Semantics<'_, RootDatabase>) -> Option<String> {
229 let ty = sema.type_of_expr(expr)?.adjusted();
230 let ty = ty.remove_ref().unwrap_or(ty);
232 name_of_type(&ty, sema.db)
235 fn name_of_type(ty: &hir::Type, db: &RootDatabase) -> Option<String> {
236 let name = if let Some(adt) = ty.as_adt() {
237 let name = adt.name(db).to_string();
239 if WRAPPER_TYPES.contains(&name.as_str()) {
240 let inner_ty = ty.type_arguments().next()?;
241 return name_of_type(&inner_ty, db);
245 } else if let Some(trait_) = ty.as_dyn_trait() {
246 trait_name(&trait_, db)?
247 } else if let Some(traits) = ty.as_impl_traits(db) {
248 let mut iter = traits.filter_map(|t| trait_name(&t, db));
249 let name = iter.next()?;
250 if iter.next().is_some() {
260 fn trait_name(trait_: &hir::Trait, db: &RootDatabase) -> Option<String> {
261 let name = trait_.name(db).to_string();
262 if USELESS_TRAITS.contains(&name.as_str()) {
268 fn from_field_name(expr: &ast::Expr) -> Option<String> {
269 let field = match expr {
270 ast::Expr::FieldExpr(field) => field,
273 let ident = field.name_ref()?.ident_token()?;
274 normalize(ident.text())
279 use ide_db::base_db::{fixture::WithFixture, FileRange};
284 fn check(ra_fixture: &str, expected: &str) {
285 let (db, file_id, range_or_offset) = RootDatabase::with_range_or_offset(ra_fixture);
286 let frange = FileRange { file_id, range: range_or_offset.into() };
288 let sema = Semantics::new(&db);
289 let source_file = sema.parse(frange.file_id);
290 let element = source_file.syntax().covering_element(frange.range);
292 element.ancestors().find_map(ast::Expr::cast).expect("selection is not an expression");
294 expr.syntax().text_range(),
296 "selection is not an expression(yet contained in one)"
298 let name = for_variable(&expr, &sema);
299 assert_eq!(&name, expected);
304 check(r#"fn foo() { $0bar()$0 }"#, "bar");
305 check(r#"fn foo() { $0bar.frobnicate()$0 }"#, "frobnicate");
310 check(r#"fn foo() { $0bar(1)$0 }"#, "bar");
315 check(r#"fn foo() { $0bar(1, 2, 3)$0 }"#, "bar");
320 check(r#"fn foo() { $0i32::bar(1, 2, 3)$0 }"#, "bar");
324 fn generic_params() {
325 check(r#"fn foo() { $0bar::<i32>(1, 2, 3)$0 }"#, "bar");
326 check(r#"fn foo() { $0bar.frobnicate::<i32, u32>()$0 }"#, "frobnicate");
336 fn to_config(&self) -> Config {}
339 $0Args.to_config()$0;
350 fn bar(n: i32, m: u32);
351 fn foo() { bar($01$0, 2) }
361 fn bar(mut n: i32, m: u32);
362 fn foo() { bar($01$0, 2) }
369 fn func_does_not_exist() {
370 check(r#"fn foo() { bar($01$0, 2) }"#, "var_name");
377 fn bar(_: i32, m: u32);
378 fn foo() { bar($01$0, 2) }
388 fn bar((n, k): (i32, i32), m: u32);
401 fn bar(&n: &i32, m: u32);
402 fn foo() { bar($0&1$0, 3) }
412 fn bar(box n: &i32, m: u32);
413 fn foo() { bar($01$0, 3) }
420 fn param_out_of_index() {
423 fn bar(n: i32, m: u32);
424 fn foo() { bar(1, 2, $03$0) }
431 fn generic_param_resolved() {
434 fn bar<T>(n: T, m: u32);
435 fn foo() { bar($01$0, 2) }
442 fn generic_param_unresolved() {
445 fn bar<T>(n: T, m: u32);
446 fn foo<T>(x: T) { bar($0x$0, 2) }
457 impl S { fn bar(&self, n: i32, m: u32); }
458 fn foo() { S.bar($01$0, 2) }
465 fn method_on_impl_trait() {
470 fn bar(&self, n: i32, m: u32);
472 impl T for S { fn bar(&self, n: i32, m: u32); }
473 fn foo() { S.bar($01$0, 2) }
484 impl S { fn bar(&self, n: i32, m: u32); }
485 fn foo() { S::bar(&S, $01$0, 2) }
496 impl S { fn bar(&self, n: i32, m: u32); }
497 fn foo() { S::bar($0&S$0, 1, 2) }
504 fn method_self_named() {
508 impl S { fn bar(strukt: &Self, n: i32, m: u32); }
509 fn foo() { S::bar($0&S$0, 1, 2) }
517 check(r#"fn foo() { let _: i32 = $01$0; }"#, "var_name");
522 check(r#"fn foo() { let _: u64 = $01$0; }"#, "var_name");
527 check(r#"fn foo() { let _: bool = $0true$0; }"#, "var_name");
535 fn foo() { let _ = $0Seed$0; }
542 fn struct_unit_to_snake() {
546 fn foo() { let _ = $0SeedState$0; }
553 fn struct_single_arg() {
557 fn foo() { let _ = $0Seed(0)$0; }
564 fn struct_with_fields() {
567 struct Seed { value: u32 }
568 fn foo() { let _ = $0Seed { value: 0 }$0; }
579 fn foo() { let _ = $0Kind::A$0; }
586 fn enum_generic_resolved() {
589 enum Kind<T> { A { x: T }, B }
590 fn foo() { let _ = $0Kind::A { x:1 }$0; }
597 fn enum_generic_unresolved() {
600 enum Kind<T> { A { x: T }, B }
601 fn foo<T>(x: T) { let _ = $0Kind::A { x }$0; }
612 fn bar() -> dyn DynHandler {}
613 fn foo() { $0(bar())$0; }
623 trait StaticHandler {}
624 fn bar() -> impl StaticHandler {}
625 fn foo() { $0(bar())$0; }
632 fn impl_trait_plus_clone() {
635 trait StaticHandler {}
637 fn bar() -> impl StaticHandler + Clone {}
638 fn foo() { $0(bar())$0; }
645 fn impl_trait_plus_lifetime() {
648 trait StaticHandler {}
650 fn bar<'a>(&'a i32) -> impl StaticHandler + 'a {}
651 fn foo() { $0(bar(&1))$0; }
658 fn impl_trait_plus_trait() {
662 trait StaticHandler {}
663 fn bar() -> impl StaticHandler + Handler {}
664 fn foo() { $0(bar())$0; }
676 fn foo() { $0(bar())$0; }
686 struct Box<T>(*const T);
688 fn bar() -> Box<Seed> {}
689 fn foo() { $0(bar())$0; }
699 struct Box<T>(*const T);
700 fn bar<T>() -> Box<T> {}
701 fn foo<T>() { $0(bar::<T>())$0; }
711 enum Option<T> { Some(T) }
713 fn bar() -> Option<Seed> {}
714 fn foo() { $0(bar())$0; }
724 enum Result<T, E> { Ok(T), Err(E) }
727 fn bar() -> Result<Seed, Error> {}
728 fn foo() { $0(bar())$0; }
738 fn foo() { $0&bar(1, 3)$0 }
745 fn name_to_string() {
748 fn foo() { $0function.name().to_string()$0 }
755 fn nested_useless_method() {
758 fn foo() { $0function.name().as_ref().unwrap().to_string()$0 }
765 fn struct_field_name() {
771 fn foo<T>(some_struct: S<T>) { $0some_struct.some_field$0 }