289 lines
11 KiB
Rust
289 lines
11 KiB
Rust
//! See [`PathTransform`].
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use crate::helpers::mod_path_to_ast;
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use either::Either;
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use hir::{AsAssocItem, HirDisplay, SemanticsScope};
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use rustc_hash::FxHashMap;
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use syntax::{
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ast::{self, AstNode},
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ted, SyntaxNode,
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};
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/// `PathTransform` substitutes path in SyntaxNodes in bulk.
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///
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/// This is mostly useful for IDE code generation. If you paste some existing
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/// code into a new context (for example, to add method overrides to an `impl`
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/// block), you generally want to appropriately qualify the names, and sometimes
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/// you might want to substitute generic parameters as well:
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///
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/// ```
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/// mod x {
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/// pub struct A<V>;
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/// pub trait T<U> { fn foo(&self, _: U) -> A<U>; }
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/// }
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///
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/// mod y {
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/// use x::T;
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///
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/// impl T<()> for () {
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/// // If we invoke **Add Missing Members** here, we want to copy-paste `foo`.
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/// // But we want a slightly-modified version of it:
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/// fn foo(&self, _: ()) -> x::A<()> {}
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/// }
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/// }
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/// ```
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pub struct PathTransform<'a> {
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generic_def: hir::GenericDef,
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substs: Vec<ast::Type>,
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target_scope: &'a SemanticsScope<'a>,
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source_scope: &'a SemanticsScope<'a>,
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}
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impl<'a> PathTransform<'a> {
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pub fn trait_impl(
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target_scope: &'a SemanticsScope<'a>,
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source_scope: &'a SemanticsScope<'a>,
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trait_: hir::Trait,
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impl_: ast::Impl,
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) -> PathTransform<'a> {
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PathTransform {
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source_scope,
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target_scope,
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generic_def: trait_.into(),
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substs: get_syntactic_substs(impl_).unwrap_or_default(),
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}
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}
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pub fn function_call(
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target_scope: &'a SemanticsScope<'a>,
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source_scope: &'a SemanticsScope<'a>,
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function: hir::Function,
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generic_arg_list: ast::GenericArgList,
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) -> PathTransform<'a> {
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PathTransform {
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source_scope,
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target_scope,
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generic_def: function.into(),
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substs: get_type_args_from_arg_list(generic_arg_list).unwrap_or_default(),
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}
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}
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pub fn apply(&self, syntax: &SyntaxNode) {
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self.build_ctx().apply(syntax)
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}
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fn build_ctx(&self) -> Ctx<'a> {
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let db = self.source_scope.db;
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let target_module = self.target_scope.module();
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let source_module = self.source_scope.module();
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let skip = match self.generic_def {
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// this is a trait impl, so we need to skip the first type parameter -- this is a bit hacky
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hir::GenericDef::Trait(_) => 1,
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_ => 0,
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};
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let substs_by_param: FxHashMap<_, _> = self
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.generic_def
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.type_params(db)
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.into_iter()
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.skip(skip)
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// The actual list of trait type parameters may be longer than the one
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// used in the `impl` block due to trailing default type parameters.
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// For that case we extend the `substs` with an empty iterator so we
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// can still hit those trailing values and check if they actually have
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// a default type. If they do, go for that type from `hir` to `ast` so
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// the resulting change can be applied correctly.
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.zip(self.substs.iter().map(Some).chain(std::iter::repeat(None)))
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.filter_map(|(k, v)| match k.split(db) {
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Either::Left(_) => None,
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Either::Right(t) => match v {
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Some(v) => Some((k, v.clone())),
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None => {
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let default = t.default(db)?;
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Some((
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k,
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ast::make::ty(
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&default.display_source_code(db, source_module.into()).ok()?,
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),
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))
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}
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},
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})
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.collect();
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Ctx { substs: substs_by_param, target_module, source_scope: self.source_scope }
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}
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}
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struct Ctx<'a> {
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substs: FxHashMap<hir::TypeOrConstParam, ast::Type>,
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target_module: hir::Module,
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source_scope: &'a SemanticsScope<'a>,
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}
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impl<'a> Ctx<'a> {
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fn apply(&self, item: &SyntaxNode) {
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// `transform_path` may update a node's parent and that would break the
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// tree traversal. Thus all paths in the tree are collected into a vec
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// so that such operation is safe.
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let paths = item
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.preorder()
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.filter_map(|event| match event {
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syntax::WalkEvent::Enter(_) => None,
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syntax::WalkEvent::Leave(node) => Some(node),
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})
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.filter_map(ast::Path::cast)
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.collect::<Vec<_>>();
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for path in paths {
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self.transform_path(path);
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}
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}
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fn transform_path(&self, path: ast::Path) -> Option<()> {
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if path.qualifier().is_some() {
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return None;
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}
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if path.segment().map_or(false, |s| {
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s.param_list().is_some() || (s.self_token().is_some() && path.parent_path().is_none())
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}) {
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// don't try to qualify `Fn(Foo) -> Bar` paths, they are in prelude anyway
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// don't try to qualify sole `self` either, they are usually locals, but are returned as modules due to namespace clashing
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return None;
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}
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let resolution = self.source_scope.speculative_resolve(&path)?;
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match resolution {
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hir::PathResolution::TypeParam(tp) => {
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if let Some(subst) = self.substs.get(&tp.merge()) {
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let parent = path.syntax().parent()?;
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if let Some(parent) = ast::Path::cast(parent.clone()) {
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// Path inside path means that there is an associated
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// type/constant on the type parameter. It is necessary
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// to fully qualify the type with `as Trait`. Even
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// though it might be unnecessary if `subst` is generic
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// type, always fully qualifying the path is safer
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// because of potential clash of associated types from
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// multiple traits
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let trait_ref = find_trait_for_assoc_item(
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self.source_scope,
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tp,
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parent.segment()?.name_ref()?,
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)
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.and_then(|trait_ref| {
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let found_path = self.target_module.find_use_path(
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self.source_scope.db.upcast(),
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hir::ModuleDef::Trait(trait_ref),
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false,
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)?;
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match ast::make::ty_path(mod_path_to_ast(&found_path)) {
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ast::Type::PathType(path_ty) => Some(path_ty),
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_ => None,
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}
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});
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let segment = ast::make::path_segment_ty(subst.clone(), trait_ref);
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let qualified =
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ast::make::path_from_segments(std::iter::once(segment), false);
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ted::replace(path.syntax(), qualified.clone_for_update().syntax());
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} else if let Some(path_ty) = ast::PathType::cast(parent) {
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ted::replace(
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path_ty.syntax(),
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subst.clone_subtree().clone_for_update().syntax(),
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);
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} else {
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ted::replace(
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path.syntax(),
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subst.clone_subtree().clone_for_update().syntax(),
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);
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}
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}
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}
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hir::PathResolution::Def(def) if def.as_assoc_item(self.source_scope.db).is_none() => {
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if let hir::ModuleDef::Trait(_) = def {
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if matches!(path.segment()?.kind()?, ast::PathSegmentKind::Type { .. }) {
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// `speculative_resolve` resolves segments like `<T as
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// Trait>` into `Trait`, but just the trait name should
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// not be used as the replacement of the original
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// segment.
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return None;
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}
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}
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let found_path =
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self.target_module.find_use_path(self.source_scope.db.upcast(), def, false)?;
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let res = mod_path_to_ast(&found_path).clone_for_update();
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if let Some(args) = path.segment().and_then(|it| it.generic_arg_list()) {
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if let Some(segment) = res.segment() {
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let old = segment.get_or_create_generic_arg_list();
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ted::replace(old.syntax(), args.clone_subtree().syntax().clone_for_update())
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}
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}
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ted::replace(path.syntax(), res.syntax())
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}
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hir::PathResolution::Local(_)
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| hir::PathResolution::ConstParam(_)
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| hir::PathResolution::SelfType(_)
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| hir::PathResolution::Def(_)
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| hir::PathResolution::BuiltinAttr(_)
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| hir::PathResolution::ToolModule(_)
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| hir::PathResolution::DeriveHelper(_) => (),
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}
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Some(())
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}
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}
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// FIXME: It would probably be nicer if we could get this via HIR (i.e. get the
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// trait ref, and then go from the types in the substs back to the syntax).
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fn get_syntactic_substs(impl_def: ast::Impl) -> Option<Vec<ast::Type>> {
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let target_trait = impl_def.trait_()?;
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let path_type = match target_trait {
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ast::Type::PathType(path) => path,
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_ => return None,
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};
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let generic_arg_list = path_type.path()?.segment()?.generic_arg_list()?;
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get_type_args_from_arg_list(generic_arg_list)
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}
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fn get_type_args_from_arg_list(generic_arg_list: ast::GenericArgList) -> Option<Vec<ast::Type>> {
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let mut result = Vec::new();
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for generic_arg in generic_arg_list.generic_args() {
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if let ast::GenericArg::TypeArg(type_arg) = generic_arg {
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result.push(type_arg.ty()?)
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}
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}
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Some(result)
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}
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fn find_trait_for_assoc_item(
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scope: &SemanticsScope<'_>,
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type_param: hir::TypeParam,
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assoc_item: ast::NameRef,
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) -> Option<hir::Trait> {
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let db = scope.db;
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let trait_bounds = type_param.trait_bounds(db);
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let assoc_item_name = assoc_item.text();
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for trait_ in trait_bounds {
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let names = trait_.items(db).into_iter().filter_map(|item| match item {
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hir::AssocItem::TypeAlias(ta) => Some(ta.name(db)),
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hir::AssocItem::Const(cst) => cst.name(db),
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_ => None,
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});
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for name in names {
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if assoc_item_name.as_str() == name.as_text()?.as_str() {
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// It is fine to return the first match because in case of
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// multiple possibilities, the exact trait must be disambiguated
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// in the definition of trait being implemented, so this search
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// should not be needed.
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return Some(trait_);
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}
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}
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}
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None
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}
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