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https://github.com/rust-lang/rust-analyzer
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simplify and document
This commit is contained in:
Lukas Wirth
parent
94e59c9c56
commit
8db88df758
6 changed files with 53 additions and 48 deletions
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@ -675,15 +675,24 @@ impl<'db> SemanticsImpl<'db> {
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ast::MacroCall(mcall) => mcall,
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// attribute we failed expansion for earlier, this might be a derive invocation
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// so try downmapping the token into the pseudo derive expansion
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// see [hir_expand::builtin_attr_macro] for how the pseudo derive expansion works
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ast::Meta(meta) => {
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let attr = meta.parent_attr()?;
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let adt = attr.syntax().parent().and_then(ast::Adt::cast)?;
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let call_id = self.with_ctx(|ctx| {
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let (_, call_id, _) = ctx.attr_to_derive_macro_call(token.with_value(&adt), token.with_value(attr))?;
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let (_, call_id, _) = ctx.attr_to_derive_macro_call(
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token.with_value(&adt),
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token.with_value(attr),
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)?;
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Some(call_id)
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})?;
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let file_id = call_id.as_file();
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return process_expansion_for_token(&mut stack,file_id,Some(adt.into()),token.as_ref(),);
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return process_expansion_for_token(
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&mut stack,
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file_id,
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Some(adt.into()),
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token.as_ref(),
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);
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},
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_ => return None,
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}
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@ -1170,6 +1170,9 @@ impl DefCollector<'_> {
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len = idx;
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}
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// We treat the #[derive] macro as an attribute call, but we do not resolve it for nameres collection.
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// This is just a trick to be able to resolve the input to derives as proper paths.
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// Check the comment in [`builtin_attr_macro`].
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let call_id = attr_macro_as_call_id(
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self.db,
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file_ast_id,
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@ -82,30 +82,47 @@ fn dummy_attr_expand(
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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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// 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
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// This is basically a hack, to get rid of hacks in the IDE layer that slowly accumulate more and more
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// in various places.
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// we transform the token tree of `#[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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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, .. } => &attr_args.0,
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_ => return ExpandResult::ok(tt.clone()),
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};
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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 (comma, group) in &derives
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.token_trees
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@ -119,38 +136,13 @@ fn derive_attr_expand(
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if comma {
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continue;
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}
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let wrap = |leaf| tt::TokenTree::Leaf(tt::Leaf::Punct(leaf));
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token_trees.push(wrap(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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token_trees.push(wrap(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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token_trees.push(mk_leaf('#'));
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token_trees.push(mk_leaf('['));
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token_trees.extend(group.cloned().map(tt::TokenTree::Leaf));
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token_trees.push(wrap(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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token_trees.push(wrap(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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token_trees.push(wrap(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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token_trees.push(wrap(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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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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@ -166,6 +166,7 @@ pub enum MacroCallKind {
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/// Outer attributes are counted first, then inner attributes. This does not support
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/// out-of-line modules, which may have attributes spread across 2 files!
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invoc_attr_index: u32,
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/// Whether this attribute is the `#[derive]` attribute.
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is_derive: bool,
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},
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}
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@ -16,7 +16,7 @@ use hir::{ItemInNs, MacroDef, ModuleDef, Name, Semantics};
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use itertools::Itertools;
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use syntax::{
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ast::{self, make, HasLoopBody},
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AstNode, SyntaxKind, SyntaxToken, TokenAtOffset, WalkEvent, T,
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AstNode, AstToken, SyntaxKind, SyntaxToken, TokenAtOffset, WalkEvent, T,
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};
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use crate::{defs::Definition, RootDatabase};
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@ -111,7 +111,7 @@ env UPDATE_EXPECT=1 cargo qt
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After adding a new inline test you need to run `cargo test -p xtask` and also update the test data as described above.
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Note [`api_walkthrough`](https://github.com/rust-analyzer/rust-analyzer/blob/2fb6af89eb794f775de60b82afe56b6f986c2a40/crates/ra_syntax/src/lib.rs#L190-L348)
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Note [`api_walkthrough`](https://github.com/rust-analyzer/rust-analyzer/blob/2fb6af89eb794f775de60b82afe56b6f986c2a40/crates/ra_syntax/src/lib.rs#L190-L348)
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in particular: it shows off various methods of working with syntax tree.
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See [#93](https://github.com/rust-analyzer/rust-analyzer/pull/93) for an example PR which fixes a bug in the grammar.
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