feat: add preliminary support for + use<..> precise_capturing syntax

[winstxnhdw]

Summary

This PR adds basic support for the following syntax.

fn captures<'a: 'a, 'b: 'b, T>() -> impl Sized + use<'b, T> {}
//                                  ~~~~~~~~~~~~~~~~~~~~~~~
//                          This opaque type does not capture `'a`.

fn outlives<'o, T: 'o>(_: T) {}

fn caller<'o, 'a, 'b: 'o, T: 'o>() {
    //        ~~
    //        ^ Note that we don't need `'a: 'o`.
    outlives::<'o>(captures::<'a, 'b, T>());
}

Related to #17598

[rustbot]

There are merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.

You can start a rebase with the following commands:

$ # rebase
$ git pull --rebase https://github.com/rust-lang/rust-analyzer.git master
$ git push --force-with-lease

The following commits are merge commits:

• d07bd22

[Veykril]

rust-analyzer/crates/syntax/src/ast/node_ext.rs

Lines 791 to 814 in eb5da56

	#[derive(Clone, Debug, PartialEq, Eq, Hash)]
	pub enum TypeBoundKind {
	/// Trait
	PathType(ast::PathType),
	/// for<'a> ...
	ForType(ast::ForType),
	/// 'a
	Lifetime(ast::Lifetime),
	}
	impl ast::TypeBound {
	pub fn kind(&self) -> TypeBoundKind {
	if let Some(path_type) = support::children(self.syntax()).next() {
	TypeBoundKind::PathType(path_type)
	} else if let Some(for_type) = support::children(self.syntax()).next() {
	TypeBoundKind::ForType(for_type)
	} else if let Some(lifetime) = self.lifetime() {
	TypeBoundKind::Lifetime(lifetime)
	} else {
	unreachable!()
	}
	}
	}

needs a change as well

[winstxnhdw]

rust-analyzer/crates/syntax/src/ast/node_ext.rs

Lines 791 to 814 in eb5da56

	#[derive(Clone, Debug, PartialEq, Eq, Hash)]
	pub enum TypeBoundKind {
	/// Trait
	PathType(ast::PathType),
	/// for<'a> ...
	ForType(ast::ForType),
	/// 'a
	Lifetime(ast::Lifetime),
	}
	impl ast::TypeBound {
	pub fn kind(&self) -> TypeBoundKind {
	if let Some(path_type) = support::children(self.syntax()).next() {
	TypeBoundKind::PathType(path_type)
	} else if let Some(for_type) = support::children(self.syntax()).next() {
	TypeBoundKind::ForType(for_type)
	} else if let Some(lifetime) = self.lifetime() {
	TypeBoundKind::Lifetime(lifetime)
	} else {
	unreachable!()
	}
	}
	}

needs a change as well

It's a lot more complex than I thought. Few things I'd like to discuss. What should this new use TypeBoundKind be named? I am not sure if we can just reuse the old ast::Use. And if we do, I'll have to add the generic_param_list method which may add some confusion as it isn't used in use declarations.

[Veykril]

Use(ast::GenericParamList) should work fine, note that we can ignore this when lowering later for now. We just want this here to prevent the panics

[Veykril]

rust-analyzer/crates/hir-def/src/hir/type_ref.rs

Lines 355 to 385 in 62a7468

	match node.kind() {
	ast::TypeBoundKind::PathType(path_type) => {
	let m = match node.question_mark_token() {
	Some(_) => TraitBoundModifier::Maybe,
	None => TraitBoundModifier::None,
	};
	lower_path_type(path_type)
	.map(|p| TypeBound::Path(p, m))
	.unwrap_or(TypeBound::Error)
	}
	ast::TypeBoundKind::ForType(for_type) => {
	let lt_refs = match for_type.generic_param_list() {
	Some(gpl) => gpl
	.lifetime_params()
	.flat_map(|lp| lp.lifetime().map(|lt| Name::new_lifetime(&lt)))
	.collect(),
	None => Box::default(),
	};
	let path = for_type.ty().and_then(|ty| match ty {
	ast::Type::PathType(path_type) => lower_path_type(path_type),
	_ => None,
	});
	match path {
	Some(p) => TypeBound::ForLifetime(lt_refs, p),
	None => TypeBound::Error,
	}
	}
	ast::TypeBoundKind::Lifetime(lifetime) => {
	TypeBound::Lifetime(LifetimeRef::new(&lifetime))
	}
	}

needs to handle the new variant, can just return TypeBound::Error in there

[Veykril]

CI failure should be unrelated now
@bors r+

[bors]

📌 Commit 9f74787 has been approved by Veykril

It is now in the queue for this repository.

[bors]

⌛ Testing commit 9f74787 with merge 0ba6f4e...

[bors]

☀️ Test successful - checks-actions
Approved by: Veykril
Pushing 0ba6f4e to master...