1 //! Transforms syntax into `Path` objects, ideally with accounting for hygiene
12 use syntax::ast::{self, AstNode, TypeBoundsOwner};
14 use super::AssociatedTypeBinding;
17 path::{GenericArg, GenericArgs, ModPath, Path, PathKind},
18 type_ref::{LifetimeRef, TypeBound, TypeRef},
21 pub(super) use lower_use::lower_use_tree;
23 /// Converts an `ast::Path` to `Path`. Works with use trees.
24 /// It correctly handles `$crate` based path from macro call.
25 pub(super) fn lower_path(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
26 let mut kind = PathKind::Plain;
27 let mut type_anchor = None;
28 let mut segments = Vec::new();
29 let mut generic_args = Vec::new();
30 let ctx = LowerCtx::with_hygiene(hygiene);
32 let segment = path.segment()?;
34 if segment.coloncolon_token().is_some() {
38 match segment.kind()? {
39 ast::PathSegmentKind::Name(name_ref) => {
40 // FIXME: this should just return name
41 match hygiene.name_ref_to_name(name_ref) {
42 Either::Left(name) => {
45 .and_then(|it| lower_generic_args(&ctx, it))
47 lower_generic_args_from_fn_path(
55 generic_args.push(args)
57 Either::Right(crate_id) => {
58 kind = PathKind::DollarCrate(crate_id);
63 ast::PathSegmentKind::Type { type_ref, trait_ref } => {
64 assert!(path.qualifier().is_none()); // this can only occur at the first segment
66 let self_type = TypeRef::from_ast(&ctx, type_ref?);
71 type_anchor = Some(Box::new(self_type));
72 kind = PathKind::Plain;
74 // <T as Trait<A>>::Foo desugars to Trait<Self=T, A>::Foo
76 let path = Path::from_src(trait_ref.path()?, hygiene)?;
77 let num_segments = path.mod_path.segments.len();
78 kind = path.mod_path.kind;
80 let mut prefix_segments = path.mod_path.segments;
81 prefix_segments.reverse();
82 segments.extend(prefix_segments);
84 let mut prefix_args = path.generic_args;
85 prefix_args.reverse();
86 generic_args.extend(prefix_args);
88 // Insert the type reference (T in the above example) as Self parameter for the trait
90 generic_args.iter_mut().rev().nth(num_segments.saturating_sub(1))?;
91 if last_segment.is_none() {
92 *last_segment = Some(Arc::new(GenericArgs::empty()));
94 let args = last_segment.as_mut().unwrap();
95 let mut args_inner = Arc::make_mut(args);
96 args_inner.has_self_type = true;
97 args_inner.args.insert(0, GenericArg::Type(self_type));
101 ast::PathSegmentKind::CrateKw => {
102 kind = PathKind::Crate;
105 ast::PathSegmentKind::SelfKw => {
106 // don't break out if `self` is the last segment of a path, this mean we got an
107 // use tree like `foo::{self}` which we want to resolve as `foo`
108 if !segments.is_empty() {
109 kind = PathKind::Super(0);
113 ast::PathSegmentKind::SuperKw => {
114 let nested_super_count = if let PathKind::Super(n) = kind { n } else { 0 };
115 kind = PathKind::Super(nested_super_count + 1);
118 path = match qualifier(&path) {
124 generic_args.reverse();
126 if segments.is_empty() && kind == PathKind::Plain && type_anchor.is_none() {
127 // plain empty paths don't exist, this means we got a single `self` segment as our path
128 kind = PathKind::Super(0);
131 // handle local_inner_macros :
132 // Basically, even in rustc it is quite hacky:
133 // https://github.com/rust-lang/rust/blob/614f273e9388ddd7804d5cbc80b8865068a3744e/src/librustc_resolve/macros.rs#L456
134 // We follow what it did anyway :)
135 if segments.len() == 1 && kind == PathKind::Plain {
136 if let Some(_macro_call) = path.syntax().parent().and_then(ast::MacroCall::cast) {
137 if let Some(crate_id) = hygiene.local_inner_macros(path) {
138 kind = PathKind::DollarCrate(crate_id);
143 let mod_path = ModPath::from_segments(kind, segments);
144 return Some(Path { type_anchor, mod_path, generic_args });
146 fn qualifier(path: &ast::Path) -> Option<ast::Path> {
147 if let Some(q) = path.qualifier() {
150 // FIXME: this bottom up traversal is not too precise.
151 // Should we handle do a top-down analysis, recording results?
152 let use_tree_list = path.syntax().ancestors().find_map(ast::UseTreeList::cast)?;
153 let use_tree = use_tree_list.parent_use_tree();
158 pub(super) fn lower_generic_args(
159 lower_ctx: &LowerCtx,
160 node: ast::GenericArgList,
161 ) -> Option<GenericArgs> {
162 let mut args = Vec::new();
163 let mut bindings = Vec::new();
164 for generic_arg in node.generic_args() {
166 ast::GenericArg::TypeArg(type_arg) => {
167 let type_ref = TypeRef::from_ast_opt(lower_ctx, type_arg.ty());
168 args.push(GenericArg::Type(type_ref));
170 ast::GenericArg::AssocTypeArg(assoc_type_arg) => {
171 if let Some(name_ref) = assoc_type_arg.name_ref() {
172 let name = name_ref.as_name();
173 let type_ref = assoc_type_arg.ty().map(|it| TypeRef::from_ast(lower_ctx, it));
174 let bounds = if let Some(l) = assoc_type_arg.type_bound_list() {
175 l.bounds().map(|it| TypeBound::from_ast(lower_ctx, it)).collect()
179 bindings.push(AssociatedTypeBinding { name, type_ref, bounds });
182 ast::GenericArg::LifetimeArg(lifetime_arg) => {
183 if let Some(lifetime) = lifetime_arg.lifetime() {
184 let lifetime_ref = LifetimeRef::new(&lifetime);
185 args.push(GenericArg::Lifetime(lifetime_ref))
188 // constants are ignored for now.
189 ast::GenericArg::ConstArg(_) => (),
193 if args.is_empty() && bindings.is_empty() {
196 Some(GenericArgs { args, has_self_type: false, bindings })
199 /// Collect `GenericArgs` from the parts of a fn-like path, i.e. `Fn(X, Y)
200 /// -> Z` (which desugars to `Fn<(X, Y), Output=Z>`).
201 fn lower_generic_args_from_fn_path(
203 params: Option<ast::ParamList>,
204 ret_type: Option<ast::RetType>,
205 ) -> Option<GenericArgs> {
206 let mut args = Vec::new();
207 let mut bindings = Vec::new();
208 if let Some(params) = params {
209 let mut param_types = Vec::new();
210 for param in params.params() {
211 let type_ref = TypeRef::from_ast_opt(&ctx, param.ty());
212 param_types.push(type_ref);
214 let arg = GenericArg::Type(TypeRef::Tuple(param_types));
217 if let Some(ret_type) = ret_type {
218 let type_ref = TypeRef::from_ast_opt(&ctx, ret_type.ty());
219 bindings.push(AssociatedTypeBinding {
221 type_ref: Some(type_ref),
225 if args.is_empty() && bindings.is_empty() {
228 Some(GenericArgs { args, has_self_type: false, bindings })