131 lines
4.4 KiB
Rust
131 lines
4.4 KiB
Rust
//! Builtin attributes.
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use crate::{db::AstDatabase, name, ExpandResult, MacroCallId, MacroCallKind};
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macro_rules! register_builtin {
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( $(($name:ident, $variant:ident) => $expand:ident),* ) => {
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#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
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pub enum BuiltinAttrExpander {
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$($variant),*
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}
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impl BuiltinAttrExpander {
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pub fn expand(
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&self,
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db: &dyn AstDatabase,
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id: MacroCallId,
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tt: &tt::Subtree,
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) -> ExpandResult<tt::Subtree> {
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let expander = match *self {
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$( BuiltinAttrExpander::$variant => $expand, )*
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};
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expander(db, id, tt)
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}
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fn find_by_name(name: &name::Name) -> Option<Self> {
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match name {
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$( id if id == &name::name![$name] => Some(BuiltinAttrExpander::$variant), )*
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_ => None,
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}
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}
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}
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};
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}
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impl BuiltinAttrExpander {
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pub fn is_derive(self) -> bool {
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matches!(self, BuiltinAttrExpander::Derive)
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}
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pub fn is_test(self) -> bool {
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matches!(self, BuiltinAttrExpander::Test)
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}
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pub fn is_bench(self) -> bool {
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matches!(self, BuiltinAttrExpander::Bench)
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}
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}
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register_builtin! {
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(bench, Bench) => dummy_attr_expand,
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(cfg_accessible, CfgAccessible) => dummy_attr_expand,
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(cfg_eval, CfgEval) => dummy_attr_expand,
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(derive, Derive) => derive_attr_expand,
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(global_allocator, GlobalAllocator) => dummy_attr_expand,
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(test, Test) => dummy_attr_expand,
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(test_case, TestCase) => dummy_attr_expand
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}
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pub fn find_builtin_attr(ident: &name::Name) -> Option<BuiltinAttrExpander> {
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BuiltinAttrExpander::find_by_name(ident)
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}
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fn dummy_attr_expand(
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_db: &dyn AstDatabase,
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_id: MacroCallId,
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tt: &tt::Subtree,
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) -> ExpandResult<tt::Subtree> {
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ExpandResult::ok(tt.clone())
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}
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/// We generate a very specific expansion here, as we do not actually expand the `#[derive]` attribute
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/// itself in name res, but we do want to expand it to something for the IDE layer, so that the input
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/// derive attributes can be downmapped, and resolved as proper paths.
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/// This is basically a hack, that simplifies the hacks we need in a lot of ide layer places to
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/// somewhat inconsistently resolve derive attributes.
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///
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/// As such, we expand `#[derive(Foo, bar::Bar)]` into
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/// ```
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/// #[Foo]
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/// #[bar::Bar]
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/// ();
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/// ```
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/// which allows fallback path resolution in hir::Semantics to properly identify our derives.
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/// Since we do not expand the attribute in nameres though, we keep the original item.
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///
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/// The ideal expansion here would be for the `#[derive]` to re-emit the annotated item and somehow
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/// use the input paths in its output as well.
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/// But that would bring two problems with it, for one every derive would duplicate the item token tree
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/// wasting a lot of memory, and it would also require some way to use a path in a way that makes it
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/// always resolve as a derive without nameres recollecting them.
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/// So this hacky approach is a lot more friendly for us, though it does require a bit of support in
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/// [`hir::Semantics`] to make this work.
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fn derive_attr_expand(
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db: &dyn AstDatabase,
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id: MacroCallId,
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tt: &tt::Subtree,
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) -> ExpandResult<tt::Subtree> {
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let loc = db.lookup_intern_macro_call(id);
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let derives = match &loc.kind {
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MacroCallKind::Attr { attr_args, is_derive: true, .. } => &attr_args.0,
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_ => return ExpandResult::ok(Default::default()),
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};
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pseudo_derive_attr_expansion(tt, derives)
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}
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pub fn pseudo_derive_attr_expansion(
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tt: &tt::Subtree,
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args: &tt::Subtree,
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) -> ExpandResult<tt::Subtree> {
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let mk_leaf = |char| {
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tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct {
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char,
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spacing: tt::Spacing::Alone,
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id: tt::TokenId::unspecified(),
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}))
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};
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let mut token_trees = Vec::new();
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for tt in (&args.token_trees)
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.split(|tt| matches!(tt, tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: ',', .. }))))
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{
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token_trees.push(mk_leaf('#'));
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token_trees.push(mk_leaf('['));
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token_trees.extend(tt.iter().cloned());
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token_trees.push(mk_leaf(']'));
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}
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token_trees.push(mk_leaf('('));
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token_trees.push(mk_leaf(')'));
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token_trees.push(mk_leaf(';'));
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ExpandResult::ok(tt::Subtree { delimiter: tt.delimiter, token_trees })
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}
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