Remove tt -> ast -> tt round trips in attrs lowering

7 files changed, 95 insertions, 73 deletions

diff --git a/crates/cfg/src/cfg_expr.rs b/crates/cfg/src/cfg_expr.rs
index fb7505ba2dd..4be6ae7481d 100644
--- a/crates/cfg/src/cfg_expr.rs
+++ b/crates/cfg/src/cfg_expr.rs
@@ -18,28 +18,6 @@ pub enum CfgAtom {
     KeyValue { key: SmolStr, value: SmolStr },
 }
 
-impl CfgAtom {
-    /// Returns `true` when the atom comes from the target specification.
-    ///
-    /// If this returns `true`, then changing this atom requires changing the compilation target. If
-    /// it returns `false`, the atom might come from a build script or the build system.
-    pub fn is_target_defined(&self) -> bool {
-        match self {
-            CfgAtom::Flag(flag) => matches!(&**flag, "unix" | "windows"),
-            CfgAtom::KeyValue { key, value: _ } => matches!(
-                &**key,
-                "target_arch"
-                    | "target_os"
-                    | "target_env"
-                    | "target_family"
-                    | "target_endian"
-                    | "target_pointer_width"
-                    | "target_vendor" // NOTE: `target_feature` is left out since it can be configured via `-Ctarget-feature`
-            ),
-        }
-    }
-}
-
 impl fmt::Display for CfgAtom {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
diff --git a/crates/cfg/src/lib.rs b/crates/cfg/src/lib.rs
index 6b178e7b04a..3b41de14335 100644
--- a/crates/cfg/src/lib.rs
+++ b/crates/cfg/src/lib.rs
@@ -131,11 +131,9 @@ impl CfgDiff {
     /// of both.
     pub fn new(enable: Vec<CfgAtom>, disable: Vec<CfgAtom>) -> Option<CfgDiff> {
         let mut occupied = FxHashSet::default();
-        for item in enable.iter().chain(disable.iter()) {
-            if !occupied.insert(item) {
-                // was present
-                return None;
-            }
+        if enable.iter().chain(disable.iter()).any(|item| occupied.insert(item)) {
+            // was present
+            return None;
         }
 
         Some(CfgDiff { enable, disable })
diff --git a/crates/hir-def/src/attr.rs b/crates/hir-def/src/attr.rs
index 8fbfcc81d28..a8e081705e3 100644
--- a/crates/hir-def/src/attr.rs
+++ b/crates/hir-def/src/attr.rs
@@ -32,6 +32,7 @@ use crate::{
     VariantId,
 };
 
+/// Desugared attributes of an item post `cfg_attr` expansion.
 #[derive(Default, Debug, Clone, PartialEq, Eq)]
 pub struct Attrs(RawAttrs);
 
@@ -228,7 +229,6 @@ pub enum DocAtom {
     KeyValue { key: SmolStr, value: SmolStr },
 }
 
-// Adapted from `CfgExpr` parsing code
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum DocExpr {
     Invalid,
@@ -448,10 +448,7 @@ impl AttrsWithOwner {
                 let map = db.fields_attrs_source_map(id.parent);
                 let file_id = id.parent.file_id(db);
                 let root = db.parse_or_expand(file_id);
-                let owner = match &map[id.local_id] {
-                    Either::Left(it) => ast::AnyHasAttrs::new(it.to_node(&root)),
-                    Either::Right(it) => ast::AnyHasAttrs::new(it.to_node(&root)),
-                };
+                let owner = ast::AnyHasAttrs::new(map[id.local_id].to_node(&root));
                 InFile::new(file_id, owner)
             }
             AttrDefId::AdtId(adt) => match adt {
@@ -634,7 +631,7 @@ fn attrs_from_item_tree_assoc<'db, N: ItemTreeModItemNode>(
 pub(crate) fn fields_attrs_source_map(
     db: &dyn DefDatabase,
     def: VariantId,
-) -> Arc<ArenaMap<LocalFieldId, Either<AstPtr<ast::TupleField>, AstPtr<ast::RecordField>>>> {
+) -> Arc<ArenaMap<LocalFieldId, AstPtr<Either<ast::TupleField, ast::RecordField>>>> {
     let mut res = ArenaMap::default();
     let child_source = def.child_source(db);
 
@@ -643,7 +640,7 @@ pub(crate) fn fields_attrs_source_map(
             idx,
             variant
                 .as_ref()
-                .either(|l| Either::Left(AstPtr::new(l)), |r| Either::Right(AstPtr::new(r))),
+                .either(|l| AstPtr::new(l).wrap_left(), |r| AstPtr::new(r).wrap_right()),
         );
     }
 
diff --git a/crates/hir-def/src/db.rs b/crates/hir-def/src/db.rs
index c9789ceb207..708abb53693 100644
--- a/crates/hir-def/src/db.rs
+++ b/crates/hir-def/src/db.rs
@@ -194,7 +194,7 @@ pub trait DefDatabase: InternDatabase + ExpandDatabase + Upcast<dyn ExpandDataba
     fn fields_attrs_source_map(
         &self,
         def: VariantId,
-    ) -> Arc<ArenaMap<LocalFieldId, Either<AstPtr<ast::TupleField>, AstPtr<ast::RecordField>>>>;
+    ) -> Arc<ArenaMap<LocalFieldId, AstPtr<Either<ast::TupleField, ast::RecordField>>>>;
 
     #[salsa::invoke(AttrsWithOwner::attrs_query)]
     fn attrs(&self, def: AttrDefId) -> Attrs;
diff --git a/crates/hir-expand/src/attrs.rs b/crates/hir-expand/src/attrs.rs
index 67a318afd06..b7c50fd82aa 100644
--- a/crates/hir-expand/src/attrs.rs
+++ b/crates/hir-expand/src/attrs.rs
@@ -117,14 +117,10 @@ impl RawAttrs {
                 None => return smallvec![attr.clone()],
             };
             let index = attr.id;
-            let attrs =
-                parts.enumerate().take(1 << AttrId::CFG_ATTR_BITS).filter_map(|(idx, attr)| {
-                    let tree = Subtree {
-                        delimiter: tt::Delimiter::invisible_spanned(attr.first()?.first_span()),
-                        token_trees: attr.to_vec(),
-                    };
-                    Attr::from_tt(db, &tree, index.with_cfg_attr(idx))
-                });
+            let attrs = parts
+                .enumerate()
+                .take(1 << AttrId::CFG_ATTR_BITS)
+                .filter_map(|(idx, attr)| Attr::from_tt(db, attr, index.with_cfg_attr(idx)));
 
             let cfg_options = &crate_graph[krate].cfg_options;
             let cfg = Subtree { delimiter: subtree.delimiter, token_trees: cfg.to_vec() };
@@ -222,12 +218,41 @@ impl Attr {
         Some(Attr { id, path, input, span })
     }
 
-    fn from_tt(db: &dyn ExpandDatabase, tt: &tt::Subtree, id: AttrId) -> Option<Attr> {
-        // FIXME: Unecessary roundtrip tt -> ast -> tt
-        let (parse, map) = mbe::token_tree_to_syntax_node(tt, mbe::TopEntryPoint::MetaItem);
-        let ast = ast::Meta::cast(parse.syntax_node())?;
-
-        Self::from_src(db, ast, SpanMapRef::ExpansionSpanMap(&map), id)
+    fn from_tt(db: &dyn ExpandDatabase, tt: &[tt::TokenTree], id: AttrId) -> Option<Attr> {
+        dbg!(tt);
+        let span = tt.first()?.first_span();
+        let path_end = tt
+            .iter()
+            .position(|tt| {
+                !matches!(
+                    tt,
+                    tt::TokenTree::Leaf(
+                        tt::Leaf::Punct(tt::Punct { char: ':' | '$', .. }) | tt::Leaf::Ident(_),
+                    )
+                )
+            })
+            .unwrap_or_else(|| tt.len());
+
+        let (path, input) = tt.split_at(path_end);
+        let path = Interned::new(ModPath::from_tt(db, path)?);
+
+        let input = match input.get(0) {
+            Some(tt::TokenTree::Subtree(tree)) => {
+                Some(Interned::new(AttrInput::TokenTree(Box::new(tree.clone()))))
+            }
+            Some(tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: '=', .. }))) => {
+                let input = match input.get(1) {
+                    Some(tt::TokenTree::Leaf(tt::Leaf::Literal(tt::Literal { text, .. }))) => {
+                        //FIXME the trimming here isn't quite right, raw strings are not handled
+                        Some(Interned::new(AttrInput::Literal(text.trim_matches('"').into())))
+                    }
+                    _ => None,
+                };
+                input
+            }
+            _ => None,
+        };
+        Some(Attr { id, path, input, span })
     }
 
     pub fn path(&self) -> &ModPath {
@@ -277,29 +302,8 @@ impl Attr {
             .token_trees
             .split(|tt| matches!(tt, tt::TokenTree::Leaf(tt::Leaf::Punct(Punct { char: ',', .. }))))
             .filter_map(move |tts| {
-                if tts.is_empty() {
-                    return None;
-                }
-                // FIXME: This is necessarily a hack. It'd be nice if we could avoid allocation
-                // here or maybe just parse a mod path from a token tree directly
-                let subtree = tt::Subtree {
-                    delimiter: tt::Delimiter::invisible_spanned(tts.first()?.first_span()),
-                    token_trees: tts.to_vec(),
-                };
-                let (parse, span_map) =
-                    mbe::token_tree_to_syntax_node(&subtree, mbe::TopEntryPoint::MetaItem);
-                let meta = ast::Meta::cast(parse.syntax_node())?;
-                // Only simple paths are allowed.
-                if meta.eq_token().is_some() || meta.expr().is_some() || meta.token_tree().is_some()
-                {
-                    return None;
-                }
-                let path = meta.path()?;
-                let call_site = span_map.span_at(path.syntax().text_range().start());
-                Some((
-                    ModPath::from_src(db, path, SpanMapRef::ExpansionSpanMap(&span_map))?,
-                    call_site,
-                ))
+                let span = tts.first()?.first_span();
+                Some((ModPath::from_tt(db, tts)?, span))
             });
 
         Some(paths)
diff --git a/crates/hir-expand/src/mod_path.rs b/crates/hir-expand/src/mod_path.rs
index 47a587e407c..9b72e034103 100644
--- a/crates/hir-expand/src/mod_path.rs
+++ b/crates/hir-expand/src/mod_path.rs
@@ -10,6 +10,7 @@ use crate::{
     hygiene::{marks_rev, SyntaxContextExt, Transparency},
     name::{known, AsName, Name},
     span_map::SpanMapRef,
+    tt,
 };
 use base_db::CrateId;
 use smallvec::SmallVec;
@@ -53,6 +54,10 @@ impl ModPath {
         convert_path(db, None, path, span_map)
     }
 
+    pub fn from_tt(db: &dyn ExpandDatabase, tt: &[tt::TokenTree]) -> Option<ModPath> {
+        convert_path_tt(db, tt)
+    }
+
     pub fn from_segments(kind: PathKind, segments: impl IntoIterator<Item = Name>) -> ModPath {
         let segments = segments.into_iter().collect();
         ModPath { kind, segments }
@@ -281,6 +286,46 @@ fn convert_path(
     Some(mod_path)
 }
 
+fn convert_path_tt(db: &dyn ExpandDatabase, tt: &[tt::TokenTree]) -> Option<ModPath> {
+    let mut leafs = tt.iter().filter_map(|tt| match tt {
+        tt::TokenTree::Leaf(leaf) => Some(leaf),
+        tt::TokenTree::Subtree(_) => None,
+    });
+    let mut segments = smallvec::smallvec![];
+    let kind = match leafs.next()? {
+        tt::Leaf::Punct(tt::Punct { char: ':', .. }) => match leafs.next()? {
+            tt::Leaf::Punct(tt::Punct { char: ':', .. }) => PathKind::Abs,
+            _ => return None,
+        },
+        tt::Leaf::Ident(tt::Ident { text, span }) if text == "$crate" => {
+            resolve_crate_root(db, span.ctx).map(PathKind::DollarCrate).unwrap_or(PathKind::Crate)
+        }
+        tt::Leaf::Ident(tt::Ident { text, .. }) if text == "self" => PathKind::Super(0),
+        tt::Leaf::Ident(tt::Ident { text, .. }) if text == "super" => {
+            let mut deg = 1;
+            while let Some(tt::Leaf::Ident(tt::Ident { text, .. })) = leafs.next() {
+                if text != "super" {
+                    segments.push(Name::new_text_dont_use(text.clone()));
+                    break;
+                }
+                deg += 1;
+            }
+            PathKind::Super(deg)
+        }
+        tt::Leaf::Ident(tt::Ident { text, .. }) if text == "crate" => PathKind::Crate,
+        tt::Leaf::Ident(ident) => {
+            segments.push(Name::new_text_dont_use(ident.text.clone()));
+            PathKind::Plain
+        }
+        _ => return None,
+    };
+    segments.extend(leafs.filter_map(|leaf| match leaf {
+        ::tt::Leaf::Ident(ident) => Some(Name::new_text_dont_use(ident.text.clone())),
+        _ => None,
+    }));
+    Some(ModPath { kind, segments })
+}
+
 pub fn resolve_crate_root(db: &dyn ExpandDatabase, mut ctxt: SyntaxContextId) -> Option<CrateId> {
     // When resolving `$crate` from a `macro_rules!` invoked in a `macro`,
     // we don't want to pretend that the `macro_rules!` definition is in the `macro`
diff --git a/crates/proc-macro-srv/src/server/token_id.rs b/crates/proc-macro-srv/src/server/token_id.rs
index 12526ad4f3a..f3da01cb104 100644
--- a/crates/proc-macro-srv/src/server/token_id.rs
+++ b/crates/proc-macro-srv/src/server/token_id.rs
@@ -206,7 +206,7 @@ impl server::TokenStream for TokenIdServer {
                     stream: if subtree.token_trees.is_empty() {
                         None
                     } else {
-                        Some(subtree.token_trees.into_iter().collect())
+                        Some(subtree.token_trees)
                     },
                     span: bridge::DelimSpan::from_single(subtree.delimiter.open),
                 }),