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|
//! See [`PathTransform`].
use crate::helpers::mod_path_to_ast;
use hir::{HirDisplay, SemanticsScope};
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 struct PathTransform<'a> {
pub subst: (hir::Trait, ast::Impl),
pub target_scope: &'a SemanticsScope<'a>,
pub source_scope: &'a SemanticsScope<'a>,
}
impl<'a> PathTransform<'a> {
pub 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)
}
|
