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//! Transforms syntax into `Path` objects, ideally with accounting for hygiene
mod lower_use;
use std::sync::Arc;
use either::Either;
use hir_expand::{
hygiene::Hygiene,
name::{name, AsName},
};
use ra_syntax::ast::{self, AstNode, TypeAscriptionOwner};
use crate::{
path::{GenericArg, GenericArgs, ModPath, Path, PathKind},
type_ref::TypeRef,
};
pub(super) use lower_use::lower_use_tree;
/// Converts an `ast::Path` to `Path`. Works with use trees.
/// It correctly handles `$crate` based path from macro call.
pub(super) fn lower_path(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
let mut kind = PathKind::Plain;
let mut type_anchor = None;
let mut segments = Vec::new();
let mut generic_args = Vec::new();
loop {
let segment = path.segment()?;
if segment.has_colon_colon() {
kind = PathKind::Abs;
}
match segment.kind()? {
ast::PathSegmentKind::Name(name_ref) => {
// FIXME: this should just return name
match hygiene.name_ref_to_name(name_ref) {
Either::Left(name) => {
let args = segment
.type_arg_list()
.and_then(lower_generic_args)
.or_else(|| {
lower_generic_args_from_fn_path(
segment.param_list(),
segment.ret_type(),
)
})
.map(Arc::new);
segments.push(name);
generic_args.push(args)
}
Either::Right(crate_id) => {
kind = PathKind::DollarCrate(crate_id);
break;
}
}
}
ast::PathSegmentKind::Type { type_ref, trait_ref } => {
assert!(path.qualifier().is_none()); // this can only occur at the first segment
let self_type = TypeRef::from_ast(type_ref?);
match trait_ref {
// <T>::foo
None => {
type_anchor = Some(Box::new(self_type));
kind = PathKind::Plain;
}
// <T as Trait<A>>::Foo desugars to Trait<Self=T, A>::Foo
Some(trait_ref) => {
let path = Path::from_src(trait_ref.path()?, hygiene)?;
kind = path.mod_path.kind;
let mut prefix_segments = path.mod_path.segments;
prefix_segments.reverse();
segments.extend(prefix_segments);
let mut prefix_args = path.generic_args;
prefix_args.reverse();
generic_args.extend(prefix_args);
// Insert the type reference (T in the above example) as Self parameter for the trait
let last_segment = generic_args.last_mut()?;
if last_segment.is_none() {
*last_segment = Some(Arc::new(GenericArgs::empty()));
};
let args = last_segment.as_mut().unwrap();
let mut args_inner = Arc::make_mut(args);
args_inner.has_self_type = true;
args_inner.args.insert(0, GenericArg::Type(self_type));
}
}
}
ast::PathSegmentKind::CrateKw => {
kind = PathKind::Crate;
break;
}
ast::PathSegmentKind::SelfKw => {
kind = PathKind::Super(0);
break;
}
ast::PathSegmentKind::SuperKw => {
kind = PathKind::Super(1);
break;
}
}
path = match qualifier(&path) {
Some(it) => it,
None => break,
};
}
segments.reverse();
generic_args.reverse();
let mod_path = ModPath { kind, segments };
return Some(Path { type_anchor, mod_path, generic_args });
fn qualifier(path: &ast::Path) -> Option<ast::Path> {
if let Some(q) = path.qualifier() {
return Some(q);
}
// FIXME: this bottom up traversal is not too precise.
// Should we handle do a top-down analysis, recording results?
let use_tree_list = path.syntax().ancestors().find_map(ast::UseTreeList::cast)?;
let use_tree = use_tree_list.parent_use_tree();
use_tree.path()
}
}
pub(super) fn lower_generic_args(node: ast::TypeArgList) -> Option<GenericArgs> {
let mut args = Vec::new();
for type_arg in node.type_args() {
let type_ref = TypeRef::from_ast_opt(type_arg.type_ref());
args.push(GenericArg::Type(type_ref));
}
// lifetimes ignored for now
let mut bindings = Vec::new();
for assoc_type_arg in node.assoc_type_args() {
if let Some(name_ref) = assoc_type_arg.name_ref() {
let name = name_ref.as_name();
let type_ref = TypeRef::from_ast_opt(assoc_type_arg.type_ref());
bindings.push((name, type_ref));
}
}
if args.is_empty() && bindings.is_empty() {
None
} else {
Some(GenericArgs { args, has_self_type: false, bindings })
}
}
/// Collect `GenericArgs` from the parts of a fn-like path, i.e. `Fn(X, Y)
/// -> Z` (which desugars to `Fn<(X, Y), Output=Z>`).
fn lower_generic_args_from_fn_path(
params: Option<ast::ParamList>,
ret_type: Option<ast::RetType>,
) -> Option<GenericArgs> {
let mut args = Vec::new();
let mut bindings = Vec::new();
if let Some(params) = params {
let mut param_types = Vec::new();
for param in params.params() {
let type_ref = TypeRef::from_ast_opt(param.ascribed_type());
param_types.push(type_ref);
}
let arg = GenericArg::Type(TypeRef::Tuple(param_types));
args.push(arg);
}
if let Some(ret_type) = ret_type {
let type_ref = TypeRef::from_ast_opt(ret_type.type_ref());
bindings.push((name![Output], type_ref))
}
if args.is_empty() && bindings.is_empty() {
None
} else {
Some(GenericArgs { args, has_self_type: false, bindings })
}
}
|
