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diff --git a/crates/assists/src/ast_transform.rs b/crates/assists/src/ast_transform.rs
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1//! `AstTransformer`s are functions that replace nodes in an AST and can be easily combined.
2use hir::{HirDisplay, PathResolution, SemanticsScope};
3use ide_db::helpers::mod_path_to_ast;
4use rustc_hash::FxHashMap;
5use syntax::{
6 algo::SyntaxRewriter,
7 ast::{self, AstNode},
8 SyntaxNode,
9};
10
11pub fn apply<'a, N: AstNode>(transformer: &dyn AstTransform<'a>, node: N) -> N {
12 SyntaxRewriter::from_fn(|element| match element {
13 syntax::SyntaxElement::Node(n) => {
14 let replacement = transformer.get_substitution(&n, transformer)?;
15 Some(replacement.into())
16 }
17 _ => None,
18 })
19 .rewrite_ast(&node)
20}
21
22/// `AstTransform` helps with applying bulk transformations to syntax nodes.
23///
24/// This is mostly useful for IDE code generation. If you paste some existing
25/// code into a new context (for example, to add method overrides to an `impl`
26/// block), you generally want to appropriately qualify the names, and sometimes
27/// you might want to substitute generic parameters as well:
28///
29/// ```
30/// mod x {
31/// pub struct A;
32/// pub trait T<U> { fn foo(&self, _: U) -> A; }
33/// }
34///
35/// mod y {
36/// use x::T;
37///
38/// impl T<()> for () {
39/// // If we invoke **Add Missing Members** here, we want to copy-paste `foo`.
40/// // But we want a slightly-modified version of it:
41/// fn foo(&self, _: ()) -> x::A {}
42/// }
43/// }
44/// ```
45///
46/// So, a single `AstTransform` describes such function from `SyntaxNode` to
47/// `SyntaxNode`. Note that the API here is a bit too high-order and high-brow.
48/// We'd want to somehow express this concept simpler, but so far nobody got to
49/// simplifying this!
50pub trait AstTransform<'a> {
51 fn get_substitution(
52 &self,
53 node: &SyntaxNode,
54 recur: &dyn AstTransform<'a>,
55 ) -> Option<SyntaxNode>;
56
57 fn or<T: AstTransform<'a> + 'a>(self, other: T) -> Box<dyn AstTransform<'a> + 'a>
58 where
59 Self: Sized + 'a,
60 {
61 Box::new(Or(Box::new(self), Box::new(other)))
62 }
63}
64
65struct Or<'a>(Box<dyn AstTransform<'a> + 'a>, Box<dyn AstTransform<'a> + 'a>);
66
67impl<'a> AstTransform<'a> for Or<'a> {
68 fn get_substitution(
69 &self,
70 node: &SyntaxNode,
71 recur: &dyn AstTransform<'a>,
72 ) -> Option<SyntaxNode> {
73 self.0.get_substitution(node, recur).or_else(|| self.1.get_substitution(node, recur))
74 }
75}
76
77pub struct SubstituteTypeParams<'a> {
78 source_scope: &'a SemanticsScope<'a>,
79 substs: FxHashMap<hir::TypeParam, ast::Type>,
80}
81
82impl<'a> SubstituteTypeParams<'a> {
83 pub fn for_trait_impl(
84 source_scope: &'a SemanticsScope<'a>,
85 // FIXME: there's implicit invariant that `trait_` and `source_scope` match...
86 trait_: hir::Trait,
87 impl_def: ast::Impl,
88 ) -> SubstituteTypeParams<'a> {
89 let substs = get_syntactic_substs(impl_def).unwrap_or_default();
90 let generic_def: hir::GenericDef = trait_.into();
91 let substs_by_param: FxHashMap<_, _> = generic_def
92 .type_params(source_scope.db)
93 .into_iter()
94 // this is a trait impl, so we need to skip the first type parameter -- this is a bit hacky
95 .skip(1)
96 // The actual list of trait type parameters may be longer than the one
97 // used in the `impl` block due to trailing default type parameters.
98 // For that case we extend the `substs` with an empty iterator so we
99 // can still hit those trailing values and check if they actually have
100 // a default type. If they do, go for that type from `hir` to `ast` so
101 // the resulting change can be applied correctly.
102 .zip(substs.into_iter().map(Some).chain(std::iter::repeat(None)))
103 .filter_map(|(k, v)| match v {
104 Some(v) => Some((k, v)),
105 None => {
106 let default = k.default(source_scope.db)?;
107 Some((
108 k,
109 ast::make::ty(
110 &default
111 .display_source_code(source_scope.db, source_scope.module()?.into())
112 .ok()?,
113 ),
114 ))
115 }
116 })
117 .collect();
118 return SubstituteTypeParams { source_scope, substs: substs_by_param };
119
120 // FIXME: It would probably be nicer if we could get this via HIR (i.e. get the
121 // trait ref, and then go from the types in the substs back to the syntax).
122 fn get_syntactic_substs(impl_def: ast::Impl) -> Option<Vec<ast::Type>> {
123 let target_trait = impl_def.trait_()?;
124 let path_type = match target_trait {
125 ast::Type::PathType(path) => path,
126 _ => return None,
127 };
128 let generic_arg_list = path_type.path()?.segment()?.generic_arg_list()?;
129
130 let mut result = Vec::new();
131 for generic_arg in generic_arg_list.generic_args() {
132 match generic_arg {
133 ast::GenericArg::TypeArg(type_arg) => result.push(type_arg.ty()?),
134 ast::GenericArg::AssocTypeArg(_)
135 | ast::GenericArg::LifetimeArg(_)
136 | ast::GenericArg::ConstArg(_) => (),
137 }
138 }
139
140 Some(result)
141 }
142 }
143}
144
145impl<'a> AstTransform<'a> for SubstituteTypeParams<'a> {
146 fn get_substitution(
147 &self,
148 node: &SyntaxNode,
149 _recur: &dyn AstTransform<'a>,
150 ) -> Option<SyntaxNode> {
151 let type_ref = ast::Type::cast(node.clone())?;
152 let path = match &type_ref {
153 ast::Type::PathType(path_type) => path_type.path()?,
154 _ => return None,
155 };
156 let resolution = self.source_scope.speculative_resolve(&path)?;
157 match resolution {
158 hir::PathResolution::TypeParam(tp) => Some(self.substs.get(&tp)?.syntax().clone()),
159 _ => None,
160 }
161 }
162}
163
164pub struct QualifyPaths<'a> {
165 target_scope: &'a SemanticsScope<'a>,
166 source_scope: &'a SemanticsScope<'a>,
167}
168
169impl<'a> QualifyPaths<'a> {
170 pub fn new(target_scope: &'a SemanticsScope<'a>, source_scope: &'a SemanticsScope<'a>) -> Self {
171 Self { target_scope, source_scope }
172 }
173}
174
175impl<'a> AstTransform<'a> for QualifyPaths<'a> {
176 fn get_substitution(
177 &self,
178 node: &SyntaxNode,
179 recur: &dyn AstTransform<'a>,
180 ) -> Option<SyntaxNode> {
181 // FIXME handle value ns?
182 let from = self.target_scope.module()?;
183 let p = ast::Path::cast(node.clone())?;
184 if p.segment().and_then(|s| s.param_list()).is_some() {
185 // don't try to qualify `Fn(Foo) -> Bar` paths, they are in prelude anyway
186 return None;
187 }
188 let resolution = self.source_scope.speculative_resolve(&p)?;
189 match resolution {
190 PathResolution::Def(def) => {
191 let found_path = from.find_use_path(self.source_scope.db.upcast(), def)?;
192 let mut path = mod_path_to_ast(&found_path);
193
194 let type_args = p
195 .segment()
196 .and_then(|s| s.generic_arg_list())
197 .map(|arg_list| apply(recur, arg_list));
198 if let Some(type_args) = type_args {
199 let last_segment = path.segment().unwrap();
200 path = path.with_segment(last_segment.with_generic_args(type_args))
201 }
202
203 Some(path.syntax().clone())
204 }
205 PathResolution::Local(_)
206 | PathResolution::TypeParam(_)
207 | PathResolution::SelfType(_)
208 | PathResolution::ConstParam(_) => None,
209 PathResolution::Macro(_) => None,
210 PathResolution::AssocItem(_) => None,
211 }
212 }
213}
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-07 15:17:25 +0000