ide_completion/completions/
fn_param.rs

1//! See [`complete_fn_param`].
2
3use hir::HirDisplay;
4use ide_db::FxHashMap;
5use itertools::Either;
6use syntax::{
7    AstNode, Direction, SmolStr, SyntaxKind, TextRange, TextSize, ToSmolStr, algo,
8    ast::{self, HasModuleItem},
9    format_smolstr, match_ast,
10};
11
12use crate::{
13    CompletionContext, CompletionItem, CompletionItemKind, Completions,
14    context::{ParamContext, ParamKind, PatternContext},
15};
16
17// FIXME: Make this a submodule of [`pattern`]
18/// Complete repeated parameters, both name and type. For example, if all
19/// functions in a file have a `spam: &mut Spam` parameter, a completion with
20/// `spam: &mut Spam` insert text/label will be suggested.
21///
22/// Also complete parameters for closure or local functions from the surrounding defined locals.
23pub(crate) fn complete_fn_param(
24    acc: &mut Completions,
25    ctx: &CompletionContext<'_>,
26    pattern_ctx: &PatternContext,
27) -> Option<()> {
28    let (ParamContext { param_list, kind, param, .. }, impl_or_trait) = match pattern_ctx {
29        PatternContext { param_ctx: Some(kind), impl_or_trait, .. } => (kind, impl_or_trait),
30        _ => return None,
31    };
32
33    let qualifier = param_qualifier(param);
34    let comma_wrapper = comma_wrapper(ctx);
35    let mut add_new_item_to_acc = |label: &str| {
36        let label = label.strip_prefix(qualifier.as_str()).unwrap_or(label);
37        let insert = if label.starts_with('#') {
38            // FIXME: `#[attr] it: i32` -> `#[attr] mut it: i32`
39            label.to_smolstr()
40        } else {
41            format_smolstr!("{qualifier}{label}")
42        };
43        let mk_item = |insert_text: &str, range: TextRange| {
44            let mut item =
45                CompletionItem::new(CompletionItemKind::Binding, range, label, ctx.edition);
46            if insert_text != label {
47                item.insert_text(insert_text);
48            }
49            item
50        };
51        let item = match &comma_wrapper {
52            Some((fmt, range)) => mk_item(&fmt(&insert), *range),
53            None => mk_item(&insert, ctx.source_range()),
54        };
55        // Completion lookup is omitted intentionally here.
56        // See the full discussion: https://github.com/rust-lang/rust-analyzer/issues/12073
57        item.add_to(acc, ctx.db)
58    };
59
60    match kind {
61        ParamKind::Function(function) => {
62            fill_fn_params(ctx, function, param_list, param, impl_or_trait, add_new_item_to_acc);
63        }
64        ParamKind::Closure(closure) => {
65            if is_simple_param(param) {
66                let stmt_list = closure.syntax().ancestors().find_map(ast::StmtList::cast)?;
67                params_from_stmt_list_scope(ctx, stmt_list, |name, ty| {
68                    add_new_item_to_acc(&format_smolstr!(
69                        "{}: {ty}",
70                        name.display(ctx.db, ctx.edition)
71                    ));
72                });
73            }
74        }
75    }
76
77    Some(())
78}
79
80fn fill_fn_params(
81    ctx: &CompletionContext<'_>,
82    function: &ast::Fn,
83    param_list: &ast::ParamList,
84    current_param: &ast::Param,
85    impl_or_trait: &Option<Either<ast::Impl, ast::Trait>>,
86    mut add_new_item_to_acc: impl FnMut(&str),
87) {
88    let mut file_params = FxHashMap::default();
89
90    let mut extract_params = |f: ast::Fn| {
91        f.param_list().into_iter().flat_map(|it| it.params()).for_each(|param| {
92            if let Some(pat) = param.pat() {
93                let whole_param = param.to_smolstr();
94                let binding = pat.to_smolstr();
95                file_params.entry(whole_param).or_insert(binding);
96            }
97        });
98    };
99
100    for node in ctx.token.parent_ancestors() {
101        if !is_simple_param(current_param) {
102            break;
103        }
104        match_ast! {
105            match node {
106                ast::SourceFile(it) => it.items().filter_map(|item| match item {
107                    ast::Item::Fn(it) => Some(it),
108                    _ => None,
109                }).for_each(&mut extract_params),
110                ast::ItemList(it) => it.items().filter_map(|item| match item {
111                    ast::Item::Fn(it) => Some(it),
112                    _ => None,
113                }).for_each(&mut extract_params),
114                ast::AssocItemList(it) => it.assoc_items().filter_map(|item| match item {
115                    ast::AssocItem::Fn(it) => Some(it),
116                    _ => None,
117                }).for_each(&mut extract_params),
118                _ => continue,
119            }
120        };
121    }
122
123    if let Some(stmt_list) = function.syntax().parent().and_then(ast::StmtList::cast)
124        && is_simple_param(current_param)
125    {
126        params_from_stmt_list_scope(ctx, stmt_list, |name, ty| {
127            file_params
128                .entry(format_smolstr!("{}: {ty}", name.display(ctx.db, ctx.edition)))
129                .or_insert(name.display(ctx.db, ctx.edition).to_smolstr());
130        });
131    }
132    remove_duplicated(&mut file_params, param_list.params());
133    let self_completion_items = ["self", "&self", "mut self", "&mut self"];
134    if should_add_self_completions(ctx.token.text_range().start(), param_list, impl_or_trait) {
135        self_completion_items.into_iter().for_each(&mut add_new_item_to_acc);
136    }
137
138    file_params.keys().for_each(|whole_param| add_new_item_to_acc(whole_param));
139}
140
141fn params_from_stmt_list_scope(
142    ctx: &CompletionContext<'_>,
143    stmt_list: ast::StmtList,
144    mut cb: impl FnMut(hir::Name, String),
145) {
146    let syntax_node = match stmt_list.syntax().last_child() {
147        Some(it) => it,
148        None => return,
149    };
150    if let Some(scope) =
151        ctx.sema.scope_at_offset(stmt_list.syntax(), syntax_node.text_range().end())
152    {
153        let module = scope.module().into();
154        scope.process_all_names(&mut |name, def| {
155            if let hir::ScopeDef::Local(local) = def
156                && let Ok(ty) = local.ty(ctx.db).display_source_code(ctx.db, module, true)
157            {
158                cb(name, ty);
159            }
160        });
161    }
162}
163
164fn remove_duplicated(
165    file_params: &mut FxHashMap<SmolStr, SmolStr>,
166    fn_params: ast::AstChildren<ast::Param>,
167) {
168    fn_params.for_each(|param| {
169        let whole_param = param.to_smolstr();
170        file_params.remove(&whole_param);
171
172        match param.pat() {
173            // remove suggestions for patterns that already exist
174            // if the type is missing we are checking the current param to be completed
175            // in which case this would find itself removing the suggestions due to itself
176            Some(pattern) if param.ty().is_some() => {
177                let binding = pattern.to_smolstr();
178                file_params.retain(|_, v| v != &binding);
179            }
180            _ => (),
181        }
182    })
183}
184
185fn should_add_self_completions(
186    cursor: TextSize,
187    param_list: &ast::ParamList,
188    impl_or_trait: &Option<Either<ast::Impl, ast::Trait>>,
189) -> bool {
190    if impl_or_trait.is_none() || param_list.self_param().is_some() {
191        return false;
192    }
193    match param_list.params().next() {
194        Some(first) => first.pat().is_some_and(|pat| pat.syntax().text_range().contains(cursor)),
195        None => true,
196    }
197}
198
199fn comma_wrapper(ctx: &CompletionContext<'_>) -> Option<(impl Fn(&str) -> SmolStr, TextRange)> {
200    let param =
201        ctx.original_token.parent_ancestors().find(|node| node.kind() == SyntaxKind::PARAM)?;
202
203    let next_token_kind = {
204        let t = param.last_token()?.next_token()?;
205        let t = algo::skip_whitespace_token(t, Direction::Next)?;
206        t.kind()
207    };
208    let prev_token_kind = {
209        let t = param.first_token()?.prev_token()?;
210        let t = algo::skip_whitespace_token(t, Direction::Prev)?;
211        t.kind()
212    };
213
214    let has_trailing_comma =
215        matches!(next_token_kind, SyntaxKind::COMMA | SyntaxKind::R_PAREN | SyntaxKind::PIPE);
216    let trailing = if has_trailing_comma { "" } else { "," };
217
218    let has_leading_comma =
219        matches!(prev_token_kind, SyntaxKind::COMMA | SyntaxKind::L_PAREN | SyntaxKind::PIPE);
220    let leading = if has_leading_comma { "" } else { ", " };
221
222    Some((move |label: &_| format_smolstr!("{leading}{label}{trailing}"), param.text_range()))
223}
224
225fn is_simple_param(param: &ast::Param) -> bool {
226    param
227        .pat()
228        .is_none_or(|pat| matches!(pat, ast::Pat::IdentPat(ident_pat) if ident_pat.pat().is_none()))
229}
230
231fn param_qualifier(param: &ast::Param) -> SmolStr {
232    let mut b = syntax::SmolStrBuilder::new();
233    if let Some(ast::Pat::IdentPat(pat)) = param.pat() {
234        if pat.ref_token().is_some() {
235            b.push_str("ref ");
236        }
237        if pat.mut_token().is_some() {
238            b.push_str("mut ");
239        }
240    }
241    b.finish()
242}
ide_completion/completions/fn_param.rs

ide_completion/completions/
fn_param.rs
