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Restructure find_path into a separate functions for modules and non-module items

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Also renames `prefer_core` imports config to `prefer_no_std` and changes the behavior of no_std path searching by preferring `core` paths `over` alloc
This commit is contained in:
Lukas Wirth 2022-09-13 15:09:40 +02:00
parent b1a4ba3e84
commit a8ecaa1979
31 changed files with 322 additions and 231 deletions
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422
crates/hir-def/src/find_path.rs
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@ -1,6 +1,6 @@
//! An algorithm to find a path to refer to a certain item.
use std::iter;
use std::{cmp::Ordering, iter};
use hir_expand::name::{known, AsName, Name};
use rustc_hash::FxHashSet;
@ -20,10 +20,10 @@ pub fn find_path(
db: &dyn DefDatabase,
item: ItemInNs,
from: ModuleId,
prefer_core: bool,
prefer_no_std: bool,
) -> Option<ModPath> {
let _p = profile::span("find_path");
find_path_inner(db, item, from, None, prefer_core)
find_path_inner(db, item, from, None, prefer_no_std)
}
pub fn find_path_prefixed(
@ -31,48 +31,14 @@ pub fn find_path_prefixed(
item: ItemInNs,
from: ModuleId,
prefix_kind: PrefixKind,
prefer_core: bool,
prefer_no_std: bool,
) -> Option<ModPath> {
let _p = profile::span("find_path_prefixed");
find_path_inner(db, item, from, Some(prefix_kind), prefer_core)
find_path_inner(db, item, from, Some(prefix_kind), prefer_no_std)
}
const MAX_PATH_LEN: usize = 15;
trait ModPathExt {
fn starts_with_std(&self) -> bool;
fn can_start_with_std(&self) -> bool;
}
impl ModPathExt for ModPath {
fn starts_with_std(&self) -> bool {
self.segments().first() == Some(&known::std)
}
// Can we replace the first segment with `std::` and still get a valid, identical path?
fn can_start_with_std(&self) -> bool {
let first_segment = self.segments().first();
first_segment == Some(&known::alloc) || first_segment == Some(&known::core)
}
}
fn check_self_super(def_map: &DefMap, item: ItemInNs, from: ModuleId) -> Option<ModPath> {
if item == ItemInNs::Types(from.into()) {
// - if the item is the module we're in, use `self`
Some(ModPath::from_segments(PathKind::Super(0), None))
} else if let Some(parent_id) = def_map[from.local_id].parent {
// - if the item is the parent module, use `super` (this is not used recursively, since `super::super` is ugly)
let parent_id = def_map.module_id(parent_id);
if item == ItemInNs::Types(ModuleDefId::ModuleId(parent_id)) {
Some(ModPath::from_segments(PathKind::Super(1), None))
} else {
None
}
} else {
None
}
}
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum PrefixKind {
/// Causes paths to always start with either `self`, `super`, `crate` or a crate-name.
@ -100,117 +66,60 @@ impl PrefixKind {
self == &PrefixKind::ByCrate
}
}
/// Attempts to find a path to refer to the given `item` visible from the `from` ModuleId
fn find_path_inner(
db: &dyn DefDatabase,
item: ItemInNs,
from: ModuleId,
prefixed: Option<PrefixKind>,
prefer_core: bool,
prefer_no_std: bool,
) -> Option<ModPath> {
// FIXME: Do fast path for std/core libs?
let mut visited_modules = FxHashSet::default();
let def_map = from.def_map(db);
find_path_inner_(
db,
&def_map,
from,
item,
MAX_PATH_LEN,
prefixed,
&mut visited_modules,
prefer_core,
)
}
fn find_path_inner_(
db: &dyn DefDatabase,
def_map: &DefMap,
from: ModuleId,
item: ItemInNs,
max_len: usize,
mut prefixed: Option<PrefixKind>,
visited_modules: &mut FxHashSet<ModuleId>,
prefer_core: bool,
) -> Option<ModPath> {
if max_len == 0 {
return None;
// - if the item is a builtin, it's in scope
if let ItemInNs::Types(ModuleDefId::BuiltinType(builtin)) = item {
return Some(ModPath::from_segments(PathKind::Plain, Some(builtin.as_name())));
}
// Base cases:
let def_map = from.def_map(db);
let crate_root = def_map.crate_root(db);
// - if the item is a module, jump straight to module search
if let ItemInNs::Types(ModuleDefId::ModuleId(module_id)) = item {
let mut visited_modules = FxHashSet::default();
return find_path_for_module(
db,
&def_map,
&mut visited_modules,
crate_root,
from,
module_id,
MAX_PATH_LEN,
prefixed,
prefer_no_std || db.crate_supports_no_std(crate_root.krate),
);
}
// - if the item is already in scope, return the name under which it is
let scope_name = def_map.with_ancestor_maps(db, from.local_id, &mut |def_map, local_id| {
def_map[local_id].scope.name_of(item).map(|(name, _)| name.clone())
});
let scope_name = find_in_scope(db, &def_map, from, item);
if prefixed.is_none() {
if let Some(scope_name) = scope_name {
return Some(ModPath::from_segments(PathKind::Plain, Some(scope_name)));
}
}
// - if the item is a builtin, it's in scope
if let ItemInNs::Types(ModuleDefId::BuiltinType(builtin)) = item {
return Some(ModPath::from_segments(PathKind::Plain, Some(builtin.as_name())));
}
// - if the item is the crate root, return `crate`
let crate_root = def_map.crate_root(db);
if item == ItemInNs::Types(ModuleDefId::ModuleId(crate_root)) {
return Some(ModPath::from_segments(PathKind::Crate, None));
}
if prefixed.filter(PrefixKind::is_absolute).is_none() {
if let modpath @ Some(_) = check_self_super(&def_map, item, from) {
return modpath;
}
}
// - if the item is the crate root of a dependency crate, return the name from the extern prelude
let root_def_map = crate_root.def_map(db);
if let ItemInNs::Types(ModuleDefId::ModuleId(item)) = item {
for (name, &def_id) in root_def_map.extern_prelude() {
if item == def_id {
let name = scope_name.unwrap_or_else(|| name.clone());
let name_already_occupied_in_type_ns = def_map
.with_ancestor_maps(db, from.local_id, &mut |def_map, local_id| {
def_map[local_id]
.scope
.type_(&name)
.filter(|&(id, _)| id != ModuleDefId::ModuleId(def_id))
})
.is_some();
let kind = if name_already_occupied_in_type_ns {
cov_mark::hit!(ambiguous_crate_start);
PathKind::Abs
} else {
PathKind::Plain
};
return Some(ModPath::from_segments(kind, Some(name)));
}
}
}
// - if the item is in the prelude, return the name from there
if let Some(prelude_module) = root_def_map.prelude() {
// Preludes in block DefMaps are ignored, only the crate DefMap is searched
let prelude_def_map = prelude_module.def_map(db);
let prelude_scope = &prelude_def_map[prelude_module.local_id].scope;
if let Some((name, vis)) = prelude_scope.name_of(item) {
if vis.is_visible_from(db, from) {
return Some(ModPath::from_segments(PathKind::Plain, Some(name.clone())));
}
}
if let Some(value) = find_in_prelude(db, &crate_root.def_map(db), item, from) {
return value;
}
// Recursive case:
// - if the item is an enum variant, refer to it via the enum
if let Some(ModuleDefId::EnumVariantId(variant)) = item.as_module_def_id() {
if let Some(mut path) =
find_path(db, ItemInNs::Types(variant.parent.into()), from, prefer_core)
{
// - if the item is an enum variant, refer to it via the enum
if let Some(mut path) = find_path_inner(
db,
ItemInNs::Types(variant.parent.into()),
from,
prefixed,
prefer_no_std,
) {
let data = db.enum_data(variant.parent);
path.push_segment(data.variants[variant.local_id].name.clone());
return Some(path);
@ -220,29 +129,184 @@ fn find_path_inner_(
// variant somewhere
}
// - otherwise, look for modules containing (reexporting) it and import it from one of those
let prefer_no_std = prefer_core || db.crate_supports_no_std(crate_root.krate);
let mut best_path = None;
let mut best_path_len = max_len;
let mut visited_modules = FxHashSet::default();
calculate_best_path(
db,
&def_map,
&mut visited_modules,
crate_root,
MAX_PATH_LEN,
item,
from,
prefixed,
prefer_no_std || db.crate_supports_no_std(crate_root.krate),
scope_name,
)
}
fn find_path_for_module(
db: &dyn DefDatabase,
def_map: &DefMap,
visited_modules: &mut FxHashSet<ModuleId>,
crate_root: ModuleId,
from: ModuleId,
module_id: ModuleId,
max_len: usize,
prefixed: Option<PrefixKind>,
prefer_no_std: bool,
) -> Option<ModPath> {
if max_len == 0 {
return None;
}
// Base cases:
// - if the item is already in scope, return the name under which it is
let scope_name = find_in_scope(db, def_map, from, ItemInNs::Types(module_id.into()));
if prefixed.is_none() {
if let Some(scope_name) = scope_name {
return Some(ModPath::from_segments(PathKind::Plain, Some(scope_name)));
}
}
// - if the item is the crate root, return `crate`
if module_id == crate_root {
return Some(ModPath::from_segments(PathKind::Crate, None));
}
// - if relative paths are fine, check if we are searching for a parent
if prefixed.filter(PrefixKind::is_absolute).is_none() {
if let modpath @ Some(_) = find_self_super(&def_map, module_id, from) {
return modpath;
}
}
// - if the item is the crate root of a dependency crate, return the name from the extern prelude
let root_def_map = crate_root.def_map(db);
for (name, &def_id) in root_def_map.extern_prelude() {
if module_id == def_id {
let name = scope_name.unwrap_or_else(|| name.clone());
let name_already_occupied_in_type_ns = def_map
.with_ancestor_maps(db, from.local_id, &mut |def_map, local_id| {
def_map[local_id]
.scope
.type_(&name)
.filter(|&(id, _)| id != ModuleDefId::ModuleId(def_id))
})
.is_some();
let kind = if name_already_occupied_in_type_ns {
cov_mark::hit!(ambiguous_crate_start);
PathKind::Abs
} else {
PathKind::Plain
};
return Some(ModPath::from_segments(kind, Some(name)));
}
}
if let Some(value) = find_in_prelude(db, &root_def_map, ItemInNs::Types(module_id.into()), from)
{
return value;
}
calculate_best_path(
db,
def_map,
visited_modules,
crate_root,
max_len,
ItemInNs::Types(module_id.into()),
from,
prefixed,
prefer_no_std,
scope_name,
)
}
fn find_in_scope(
db: &dyn DefDatabase,
def_map: &DefMap,
from: ModuleId,
item: ItemInNs,
) -> Option<Name> {
def_map.with_ancestor_maps(db, from.local_id, &mut |def_map, local_id| {
def_map[local_id].scope.name_of(item).map(|(name, _)| name.clone())
})
}
fn find_in_prelude(
db: &dyn DefDatabase,
root_def_map: &DefMap,
item: ItemInNs,
from: ModuleId,
) -> Option<Option<ModPath>> {
if let Some(prelude_module) = root_def_map.prelude() {
// Preludes in block DefMaps are ignored, only the crate DefMap is searched
let prelude_def_map = prelude_module.def_map(db);
let prelude_scope = &prelude_def_map[prelude_module.local_id].scope;
if let Some((name, vis)) = prelude_scope.name_of(item) {
if vis.is_visible_from(db, from) {
return Some(Some(ModPath::from_segments(PathKind::Plain, Some(name.clone()))));
}
}
}
None
}
fn find_self_super(def_map: &DefMap, item: ModuleId, from: ModuleId) -> Option<ModPath> {
if item == from {
// - if the item is the module we're in, use `self`
Some(ModPath::from_segments(PathKind::Super(0), None))
} else if let Some(parent_id) = def_map[from.local_id].parent {
// - if the item is the parent module, use `super` (this is not used recursively, since `super::super` is ugly)
let parent_id = def_map.module_id(parent_id);
if item == parent_id {
Some(ModPath::from_segments(PathKind::Super(1), None))
} else {
None
}
} else {
None
}
}
fn calculate_best_path(
db: &dyn DefDatabase,
def_map: &DefMap,
visited_modules: &mut FxHashSet<ModuleId>,
crate_root: ModuleId,
max_len: usize,
item: ItemInNs,
from: ModuleId,
mut prefixed: Option<PrefixKind>,
prefer_no_std: bool,
scope_name: Option<Name>,
) -> Option<ModPath> {
if max_len <= 1 {
return None;
}
let mut best_path = None;
// Recursive case:
// - otherwise, look for modules containing (reexporting) it and import it from one of those
if item.krate(db) == Some(from.krate) {
let mut best_path_len = max_len;
// Item was defined in the same crate that wants to import it. It cannot be found in any
// dependency in this case.
// FIXME: this should have a fast path that doesn't look through the prelude again?
for (module_id, name) in find_local_import_locations(db, item, from) {
if !visited_modules.insert(module_id) {
cov_mark::hit!(recursive_imports);
continue;
}
if let Some(mut path) = find_path_inner_(
if let Some(mut path) = find_path_for_module(
db,
def_map,
visited_modules,
crate_root,
from,
ItemInNs::Types(ModuleDefId::ModuleId(module_id)),
module_id,
best_path_len - 1,
prefixed,
visited_modules,
prefer_core,
prefer_no_std,
) {
path.push_segment(name);
@ -265,15 +329,16 @@ fn find_path_inner_(
import_map.import_info_for(item).and_then(|info| {
// Determine best path for containing module and append last segment from `info`.
// FIXME: we should guide this to look up the path locally, or from the same crate again?
let mut path = find_path_inner_(
let mut path = find_path_for_module(
db,
def_map,
from,
ItemInNs::Types(ModuleDefId::ModuleId(info.container)),
best_path_len - 1,
prefixed,
visited_modules,
prefer_core,
from,
crate_root,
info.container,
max_len - 1,
prefixed,
prefer_no_std,
)?;
cov_mark::hit!(partially_imported);
path.push_segment(info.path.segments.last()?.clone());
@ -289,16 +354,12 @@ fn find_path_inner_(
best_path = Some(new_path);
}
}
// If the item is declared inside a block expression, don't use a prefix, as we don't handle
// that correctly (FIXME).
if let Some(item_module) = item.as_module_def_id().and_then(|did| did.module(db)) {
if item_module.def_map(db).block_id().is_some() && prefixed.is_some() {
if let Some(module) = item.module(db) {
if module.def_map(db).block_id().is_some() && prefixed.is_some() {
cov_mark::hit!(prefixed_in_block_expression);
prefixed = Some(PrefixKind::Plain);
}
}
match prefixed.map(PrefixKind::prefix) {
Some(prefix) => best_path.or_else(|| {
scope_name.map(|scope_name| ModPath::from_segments(prefix, Some(scope_name)))
@ -308,29 +369,48 @@ fn find_path_inner_(
}
fn select_best_path(old_path: ModPath, new_path: ModPath, prefer_no_std: bool) -> ModPath {
if old_path.starts_with_std() && new_path.can_start_with_std() {
if prefer_no_std {
cov_mark::hit!(prefer_no_std_paths);
new_path
} else {
cov_mark::hit!(prefer_std_paths);
old_path
const STD_CRATES: [Name; 3] = [known::std, known::core, known::alloc];
match (old_path.segments().first(), new_path.segments().first()) {
(Some(old), Some(new)) if STD_CRATES.contains(old) && STD_CRATES.contains(new) => {
let rank = match prefer_no_std {
false => |name: &Name| match name {
name if name == &known::core => 0,
name if name == &known::alloc => 0,
name if name == &known::std => 1,
_ => unreachable!(),
},
true => |name: &Name| match name {
name if name == &known::core => 2,
name if name == &known::alloc => 1,
name if name == &known::std => 0,
_ => unreachable!(),
},
};
let nrank = rank(new);
let orank = rank(old);
match nrank.cmp(&orank) {
Ordering::Less => old_path,
Ordering::Equal => {
if new_path.len() < old_path.len() {
new_path
} else {
old_path
}
}
Ordering::Greater => new_path,
}
}
} else if new_path.starts_with_std() && old_path.can_start_with_std() {
if prefer_no_std {
cov_mark::hit!(prefer_no_std_paths);
old_path
} else {
cov_mark::hit!(prefer_std_paths);
new_path
_ => {
if new_path.len() < old_path.len() {
new_path
} else {
old_path
}
}
} else if new_path.len() < old_path.len() {
new_path
} else {
old_path
}
}
// FIXME: Remove allocations
/// Finds locations in `from.krate` from which `item` can be imported by `from`.
fn find_local_import_locations(
db: &dyn DefDatabase,
@ -490,8 +570,8 @@ $0
"#,
"E::A",
"E::A",
"E::A",
"E::A",
"crate::E::A",
"self::E::A",
);
}
@ -810,7 +890,6 @@ pub use super::foo;
#[test]
fn prefer_std_paths_over_alloc() {
cov_mark::check!(prefer_std_paths);
check_found_path(
r#"
//- /main.rs crate:main deps:alloc,std
@ -835,7 +914,6 @@ pub mod sync {
#[test]
fn prefer_core_paths_over_std() {
cov_mark::check!(prefer_no_std_paths);
check_found_path(
r#"
//- /main.rs crate:main deps:core,std