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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 syntax::ast::{self, AstNode, TypeBoundsOwner};
use super::AssociatedTypeBinding;
use crate::{
body::LowerCtx,
path::{GenericArg, GenericArgs, ModPath, Path, PathKind},
type_ref::{LifetimeRef, TypeBound, 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();
let ctx = LowerCtx::with_hygiene(hygiene);
loop {
let segment = path.segment()?;
if segment.coloncolon_token().is_some() {
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
.generic_arg_list()
.and_then(|it| lower_generic_args(&ctx, it))
.or_else(|| {
lower_generic_args_from_fn_path(
&ctx,
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(&ctx, 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 => {
// don't break out if `self` is the last segment of a path, this mean we got an
// use tree like `foo::{self}` which we want to resolve as `foo`
if !segments.is_empty() {
kind = PathKind::Super(0);
break;
}
}
ast::PathSegmentKind::SuperKw => {
let nested_super_count = if let PathKind::Super(n) = kind { n } else { 0 };
kind = PathKind::Super(nested_super_count + 1);
}
}
path = match qualifier(&path) {
Some(it) => it,
None => break,
};
}
segments.reverse();
generic_args.reverse();
if segments.is_empty() && kind == PathKind::Plain && type_anchor.is_none() {
// plain empty paths don't exist, this means we got a single `self` segment as our path
kind = PathKind::Super(0);
}
// handle local_inner_macros :
// Basically, even in rustc it is quite hacky:
// https://github.com/rust-lang/rust/blob/614f273e9388ddd7804d5cbc80b8865068a3744e/src/librustc_resolve/macros.rs#L456
// We follow what it did anyway :)
if segments.len() == 1 && kind == PathKind::Plain {
if let Some(_macro_call) = path.syntax().parent().and_then(ast::MacroCall::cast) {
if let Some(crate_id) = hygiene.local_inner_macros(path) {
kind = PathKind::DollarCrate(crate_id);
}
}
}
let mod_path = ModPath::from_segments(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(
lower_ctx: &LowerCtx,
node: ast::GenericArgList,
) -> Option<GenericArgs> {
let mut args = Vec::new();
let mut bindings = Vec::new();
for generic_arg in node.generic_args() {
match generic_arg {
ast::GenericArg::TypeArg(type_arg) => {
let type_ref = TypeRef::from_ast_opt(lower_ctx, type_arg.ty());
args.push(GenericArg::Type(type_ref));
}
ast::GenericArg::AssocTypeArg(assoc_type_arg) => {
if let Some(name_ref) = assoc_type_arg.name_ref() {
let name = name_ref.as_name();
let type_ref = assoc_type_arg.ty().map(|it| TypeRef::from_ast(lower_ctx, it));
let bounds = if let Some(l) = assoc_type_arg.type_bound_list() {
l.bounds().map(|it| TypeBound::from_ast(lower_ctx, it)).collect()
} else {
Vec::new()
};
bindings.push(AssociatedTypeBinding { name, type_ref, bounds });
}
}
ast::GenericArg::LifetimeArg(lifetime_arg) => {
if let Some(lifetime) = lifetime_arg.lifetime() {
let lifetime_ref = LifetimeRef::new(&lifetime);
args.push(GenericArg::Lifetime(lifetime_ref))
}
}
// constants are ignored for now.
ast::GenericArg::ConstArg(_) => (),
}
}
if args.is_empty() && bindings.is_empty() {
return None;
}
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(
ctx: &LowerCtx,
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(&ctx, param.ty());
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(&ctx, ret_type.ty());
bindings.push(AssociatedTypeBinding {
name: name![Output],
type_ref: Some(type_ref),
bounds: Vec::new(),
});
}
if args.is_empty() && bindings.is_empty() {
None
} else {
Some(GenericArgs { args, has_self_type: false, bindings })
}
}
|
