1 //! `assists` crate provides a bunch of code assists, also known as code actions
2 //! (in LSP) or intentions (in IntelliJ).
4 //! An assist is a micro-refactoring, which is automatically activated in
5 //! certain context. For example, if the cursor is over `,`, a "swap `,`" assist
8 //! ## Assists Guidelines
10 //! Assists are the main mechanism to deliver advanced IDE features to the user,
11 //! so we should pay extra attention to the UX.
13 //! The power of assists comes from their context-awareness. The main problem
14 //! with IDE features is that there are a lot of them, and it's hard to teach
15 //! the user what's available. Assists solve this problem nicely: 💡 signifies
16 //! that *something* is possible, and clicking on it reveals a *short* list of
17 //! actions. Contrast it with Emacs `M-x`, which just spits an infinite list of
20 //! Here are some considerations when creating a new assist:
22 //! * It's good to preserve semantics, and it's good to keep the code compiling,
23 //! but it isn't necessary. Example: "flip binary operation" might change
25 //! * Assist shouldn't necessary make the code "better". A lot of assist come in
26 //! pairs: "if let <-> match".
27 //! * Assists should have as narrow scope as possible. Each new assists greatly
28 //! improves UX for cases where the user actually invokes it, but it makes UX
29 //! worse for every case where the user clicks 💡 to invoke some *other*
30 //! assist. So, a rarely useful assist which is always applicable can be a net
32 //! * Rarely useful actions are tricky. Sometimes there are features which are
33 //! clearly useful to some users, but are just noise most of the time. We
34 //! don't have a good solution here, our current approach is to make this
35 //! functionality available only if assist is applicable to the whole
36 //! selection. Example: `sort_items` sorts items alphabetically. Naively, it
37 //! should be available more or less everywhere, which isn't useful. So
38 //! instead we only show it if the user *selects* the items they want to sort.
39 //! * Consider grouping related assists together (see [`Assists::add_group`]).
40 //! * Make assists robust. If the assist depends on results of type-inference too
41 //! much, it might only fire in fully-correct code. This makes assist less
42 //! useful and (worse) less predictable. The user should have a clear
43 //! intuition when each particular assist is available.
44 //! * Make small assists, which compose. Example: rather than auto-importing
45 //! enums in `add_missing_match_arms`, we use fully-qualified names. There's a
46 //! separate assist to shorten a fully-qualified name.
47 //! * Distinguish between assists and fixits for diagnostics. Internally, fixits
48 //! and assists are equivalent. They have the same "show a list + invoke a
49 //! single element" workflow, and both use [`Assist`] data structure. The main
50 //! difference is in the UX: while 💡 looks only at the cursor position,
51 //! diagnostics squigglies and fixits are calculated for the whole file and
52 //! are presented to the user eagerly. So, diagnostics should be fixable
53 //! errors, while assists can be just suggestions for an alternative way to do
54 //! something. If something *could* be a diagnostic, it should be a
55 //! diagnostic. Conversely, it might be valuable to turn a diagnostic with a
56 //! lot of false errors into an assist.
58 //! See also this post:
59 //! <https://rust-analyzer.github.io/blog/2020/09/28/how-to-make-a-light-bulb.html>
61 #![warn(rust_2018_idioms, unused_lifetimes, semicolon_in_expressions_from_macros)]
64 macro_rules! eprintln {
65 ($($tt:tt)*) => { stdx::eprintln!($($tt)*) };
75 use ide_db::{base_db::FileRange, RootDatabase};
76 use syntax::TextRange;
78 pub(crate) use crate::assist_context::{AssistContext, Assists};
80 pub use assist_config::AssistConfig;
81 pub use ide_db::assists::{
82 Assist, AssistId, AssistKind, AssistResolveStrategy, GroupLabel, SingleResolve,
85 /// Return all the assists applicable at the given position.
87 // NOTE: We don't have a `Feature: ` section for assists, they are special-cased
91 config: &AssistConfig,
92 resolve: AssistResolveStrategy,
95 let sema = Semantics::new(db);
96 let ctx = AssistContext::new(sema, config, range);
97 let mut acc = Assists::new(&ctx, resolve);
98 handlers::all().iter().for_each(|handler| {
99 handler(&mut acc, &ctx);
105 use crate::{AssistContext, Assists};
107 pub(crate) type Handler = fn(&mut Assists, &AssistContext<'_>) -> Option<()>;
109 mod add_explicit_type;
110 mod add_label_to_loop;
111 mod add_lifetime_to_type;
112 mod add_missing_impl_members;
116 mod change_visibility;
117 mod convert_bool_then;
118 mod convert_comment_block;
119 mod convert_integer_literal;
120 mod convert_into_to_from;
121 mod convert_iter_for_each_to_for;
122 mod convert_let_else_to_match;
123 mod convert_tuple_struct_to_named_struct;
124 mod convert_to_guarded_return;
125 mod convert_two_arm_bool_match_to_matches_macro;
126 mod convert_while_to_loop;
127 mod destructure_tuple_binding;
128 mod expand_glob_import;
129 mod extract_function;
131 mod extract_struct_from_enum_variant;
132 mod extract_type_alias;
133 mod extract_variable;
134 mod add_missing_match_arms;
138 mod flip_trait_bound;
139 mod generate_constant;
140 mod generate_default_from_enum_variant;
141 mod generate_default_from_new;
144 mod generate_documentation_template;
145 mod generate_enum_is_method;
146 mod generate_enum_projection_method;
147 mod generate_enum_variant;
148 mod generate_from_impl_for_enum;
149 mod generate_function;
152 mod generate_is_empty_from_len;
155 mod generate_delegate_methods;
158 mod inline_local_variable;
159 mod inline_type_alias;
160 mod introduce_named_lifetime;
163 mod merge_match_arms;
166 mod move_module_to_file;
168 mod move_from_mod_rs;
169 mod number_representation;
170 mod promote_local_to_const;
171 mod pull_assignment_up;
173 mod qualify_method_call;
177 mod remove_unused_param;
179 mod reorder_impl_items;
180 mod replace_try_expr_with_match;
181 mod replace_derive_with_manual_impl;
182 mod replace_if_let_with_match;
183 mod replace_or_with_or_else;
184 mod introduce_named_generic;
185 mod replace_let_with_if_let;
186 mod replace_qualified_name_with_use;
187 mod replace_string_with_char;
188 mod replace_turbofish_with_explicit_type;
190 mod unmerge_match_arm;
194 mod unnecessary_async;
196 mod unwrap_result_return_type;
197 mod wrap_return_type_in_result;
199 pub(crate) fn all() -> &'static [Handler] {
201 // These are alphabetic for the foolish consistency
202 add_explicit_type::add_explicit_type,
203 add_label_to_loop::add_label_to_loop,
204 add_missing_match_arms::add_missing_match_arms,
205 add_lifetime_to_type::add_lifetime_to_type,
206 add_return_type::add_return_type,
207 add_turbo_fish::add_turbo_fish,
208 apply_demorgan::apply_demorgan,
209 auto_import::auto_import,
210 change_visibility::change_visibility,
211 convert_bool_then::convert_bool_then_to_if,
212 convert_bool_then::convert_if_to_bool_then,
213 convert_comment_block::convert_comment_block,
214 convert_integer_literal::convert_integer_literal,
215 convert_into_to_from::convert_into_to_from,
216 convert_iter_for_each_to_for::convert_iter_for_each_to_for,
217 convert_iter_for_each_to_for::convert_for_loop_with_for_each,
218 convert_let_else_to_match::convert_let_else_to_match,
219 convert_to_guarded_return::convert_to_guarded_return,
220 convert_tuple_struct_to_named_struct::convert_tuple_struct_to_named_struct,
221 convert_two_arm_bool_match_to_matches_macro::convert_two_arm_bool_match_to_matches_macro,
222 convert_while_to_loop::convert_while_to_loop,
223 destructure_tuple_binding::destructure_tuple_binding,
224 expand_glob_import::expand_glob_import,
225 extract_struct_from_enum_variant::extract_struct_from_enum_variant,
226 extract_type_alias::extract_type_alias,
227 fix_visibility::fix_visibility,
228 flip_binexpr::flip_binexpr,
229 flip_comma::flip_comma,
230 flip_trait_bound::flip_trait_bound,
231 generate_constant::generate_constant,
232 generate_default_from_enum_variant::generate_default_from_enum_variant,
233 generate_default_from_new::generate_default_from_new,
234 generate_derive::generate_derive,
235 generate_documentation_template::generate_documentation_template,
236 generate_documentation_template::generate_doc_example,
237 generate_enum_is_method::generate_enum_is_method,
238 generate_enum_projection_method::generate_enum_as_method,
239 generate_enum_projection_method::generate_enum_try_into_method,
240 generate_enum_variant::generate_enum_variant,
241 generate_from_impl_for_enum::generate_from_impl_for_enum,
242 generate_function::generate_function,
243 generate_impl::generate_impl,
244 generate_is_empty_from_len::generate_is_empty_from_len,
245 generate_new::generate_new,
246 inline_call::inline_call,
247 inline_call::inline_into_callers,
248 inline_local_variable::inline_local_variable,
249 inline_type_alias::inline_type_alias,
250 inline_type_alias::inline_type_alias_uses,
251 introduce_named_generic::introduce_named_generic,
252 introduce_named_lifetime::introduce_named_lifetime,
253 invert_if::invert_if,
254 merge_imports::merge_imports,
255 merge_match_arms::merge_match_arms,
256 move_bounds::move_bounds_to_where_clause,
257 move_guard::move_arm_cond_to_match_guard,
258 move_guard::move_guard_to_arm_body,
259 move_module_to_file::move_module_to_file,
260 move_to_mod_rs::move_to_mod_rs,
261 move_from_mod_rs::move_from_mod_rs,
262 number_representation::reformat_number_literal,
263 pull_assignment_up::pull_assignment_up,
264 promote_local_to_const::promote_local_to_const,
265 qualify_path::qualify_path,
266 qualify_method_call::qualify_method_call,
267 raw_string::add_hash,
268 raw_string::make_usual_string,
269 raw_string::remove_hash,
270 remove_dbg::remove_dbg,
271 remove_mut::remove_mut,
272 remove_unused_param::remove_unused_param,
273 reorder_fields::reorder_fields,
274 reorder_impl_items::reorder_impl_items,
275 replace_try_expr_with_match::replace_try_expr_with_match,
276 replace_derive_with_manual_impl::replace_derive_with_manual_impl,
277 replace_if_let_with_match::replace_if_let_with_match,
278 replace_if_let_with_match::replace_match_with_if_let,
279 replace_let_with_if_let::replace_let_with_if_let,
280 replace_or_with_or_else::replace_or_else_with_or,
281 replace_or_with_or_else::replace_or_with_or_else,
282 replace_turbofish_with_explicit_type::replace_turbofish_with_explicit_type,
283 replace_qualified_name_with_use::replace_qualified_name_with_use,
284 sort_items::sort_items,
285 split_import::split_import,
286 toggle_ignore::toggle_ignore,
287 unmerge_match_arm::unmerge_match_arm,
288 unmerge_use::unmerge_use,
289 unnecessary_async::unnecessary_async,
290 unwrap_block::unwrap_block,
291 unwrap_result_return_type::unwrap_result_return_type,
292 wrap_return_type_in_result::wrap_return_type_in_result,
293 // These are manually sorted for better priorities. By default,
294 // priority is determined by the size of the target range (smaller
295 // target wins). If the ranges are equal, position in this list is
296 // used as a tie-breaker.
297 add_missing_impl_members::add_missing_impl_members,
298 add_missing_impl_members::add_missing_default_members,
300 replace_string_with_char::replace_string_with_char,
301 replace_string_with_char::replace_char_with_string,
302 raw_string::make_raw_string,
304 extract_variable::extract_variable,
305 extract_function::extract_function,
306 extract_module::extract_module,
308 generate_getter::generate_getter,
309 generate_getter::generate_getter_mut,
310 generate_setter::generate_setter,
311 generate_delegate_methods::generate_delegate_methods,
312 generate_deref::generate_deref,
313 // Are you sure you want to add new assist here, and not to the
314 // sorted list above?