aboutsummaryrefslogtreecommitdiff
path: root/crates/ide_assists/src/path_transform.rs
blob: 48a7fa06a220a209f3ec9f659cb7b50d9aa2b7f5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
//! See [`PathTransform`].

use hir::{HirDisplay, SemanticsScope};
use ide_db::helpers::mod_path_to_ast;
use rustc_hash::FxHashMap;
use syntax::{
    ast::{self, AstNode},
    ted,
};

/// `PathTransform` substitutes path in SyntaxNodes in bulk.
///
/// This is mostly useful for IDE code generation. If you paste some existing
/// code into a new context (for example, to add method overrides to an `impl`
/// block), you generally want to appropriately qualify the names, and sometimes
/// you might want to substitute generic parameters as well:
///
/// ```
/// mod x {
///   pub struct A<V>;
///   pub trait T<U> { fn foo(&self, _: U) -> A<U>; }
/// }
///
/// mod y {
///   use x::T;
///
///   impl T<()> for () {
///      // If we invoke **Add Missing Members** here, we want to copy-paste `foo`.
///      // But we want a slightly-modified version of it:
///      fn foo(&self, _: ()) -> x::A<()> {}
///   }
/// }
/// ```
pub(crate) struct PathTransform<'a> {
    pub(crate) subst: (hir::Trait, ast::Impl),
    pub(crate) target_scope: &'a SemanticsScope<'a>,
    pub(crate) source_scope: &'a SemanticsScope<'a>,
}

impl<'a> PathTransform<'a> {
    pub(crate) fn apply(&self, item: ast::AssocItem) {
        if let Some(ctx) = self.build_ctx() {
            ctx.apply(item)
        }
    }
    fn build_ctx(&self) -> Option<Ctx<'a>> {
        let db = self.source_scope.db;
        let target_module = self.target_scope.module()?;
        let source_module = self.source_scope.module()?;

        let substs = get_syntactic_substs(self.subst.1.clone()).unwrap_or_default();
        let generic_def: hir::GenericDef = self.subst.0.into();
        let substs_by_param: FxHashMap<_, _> = generic_def
            .type_params(db)
            .into_iter()
            // this is a trait impl, so we need to skip the first type parameter -- this is a bit hacky
            .skip(1)
            // The actual list of trait type parameters may be longer than the one
            // used in the `impl` block due to trailing default type parameters.
            // For that case we extend the `substs` with an empty iterator so we
            // can still hit those trailing values and check if they actually have
            // a default type. If they do, go for that type from `hir` to `ast` so
            // the resulting change can be applied correctly.
            .zip(substs.into_iter().map(Some).chain(std::iter::repeat(None)))
            .filter_map(|(k, v)| match v {
                Some(v) => Some((k, v)),
                None => {
                    let default = k.default(db)?;
                    Some((
                        k,
                        ast::make::ty(&default.display_source_code(db, source_module.into()).ok()?),
                    ))
                }
            })
            .collect();

        let res = Ctx { substs: substs_by_param, target_module, source_scope: self.source_scope };
        Some(res)
    }
}

struct Ctx<'a> {
    substs: FxHashMap<hir::TypeParam, ast::Type>,
    target_module: hir::Module,
    source_scope: &'a SemanticsScope<'a>,
}

impl<'a> Ctx<'a> {
    fn apply(&self, item: ast::AssocItem) {
        for event in item.syntax().preorder() {
            let node = match event {
                syntax::WalkEvent::Enter(_) => continue,
                syntax::WalkEvent::Leave(it) => it,
            };
            if let Some(path) = ast::Path::cast(node.clone()) {
                self.transform_path(path);
            }
        }
    }
    fn transform_path(&self, path: ast::Path) -> Option<()> {
        if path.qualifier().is_some() {
            return None;
        }
        if path.segment().and_then(|s| s.param_list()).is_some() {
            // don't try to qualify `Fn(Foo) -> Bar` paths, they are in prelude anyway
            return None;
        }

        let resolution = self.source_scope.speculative_resolve(&path)?;

        match resolution {
            hir::PathResolution::TypeParam(tp) => {
                if let Some(subst) = self.substs.get(&tp) {
                    ted::replace(path.syntax(), subst.clone_subtree().clone_for_update().syntax())
                }
            }
            hir::PathResolution::Def(def) => {
                let found_path =
                    self.target_module.find_use_path(self.source_scope.db.upcast(), def)?;
                let res = mod_path_to_ast(&found_path).clone_for_update();
                if let Some(args) = path.segment().and_then(|it| it.generic_arg_list()) {
                    if let Some(segment) = res.segment() {
                        let old = segment.get_or_create_generic_arg_list();
                        ted::replace(old.syntax(), args.clone_subtree().syntax().clone_for_update())
                    }
                }
                ted::replace(path.syntax(), res.syntax())
            }
            hir::PathResolution::Local(_)
            | hir::PathResolution::ConstParam(_)
            | hir::PathResolution::SelfType(_)
            | hir::PathResolution::Macro(_)
            | hir::PathResolution::AssocItem(_) => (),
        }
        Some(())
    }
}

// FIXME: It would probably be nicer if we could get this via HIR (i.e. get the
// trait ref, and then go from the types in the substs back to the syntax).
fn get_syntactic_substs(impl_def: ast::Impl) -> Option<Vec<ast::Type>> {
    let target_trait = impl_def.trait_()?;
    let path_type = match target_trait {
        ast::Type::PathType(path) => path,
        _ => return None,
    };
    let generic_arg_list = path_type.path()?.segment()?.generic_arg_list()?;

    let mut result = Vec::new();
    for generic_arg in generic_arg_list.generic_args() {
        match generic_arg {
            ast::GenericArg::TypeArg(type_arg) => result.push(type_arg.ty()?),
            ast::GenericArg::AssocTypeArg(_)
            | ast::GenericArg::LifetimeArg(_)
            | ast::GenericArg::ConstArg(_) => (),
        }
    }

    Some(result)
}