29 files changed, 788 insertions, 507 deletions

diff --git a/Cargo.lock b/Cargo.lock
index ba0b8e083..7f89fc580 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -418,9 +418,9 @@ checksum = "37ab347416e802de484e4d03c7316c48f1ecb56574dfd4a46a80f173ce1de04d"
 
 [[package]]
 name = "flate2"
-version = "1.0.19"
+version = "1.0.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7411863d55df97a419aa64cb4d2f167103ea9d767e2c54a1868b7ac3f6b47129"
+checksum = "cd3aec53de10fe96d7d8c565eb17f2c687bb5518a2ec453b5b1252964526abe0"
 dependencies = [
  "cfg-if",
  "crc32fast",
@@ -785,9 +785,9 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.83"
+version = "0.2.84"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7eb0c4e9c72ee9d69b767adebc5f4788462a3b45624acd919475c92597bcaf4f"
+checksum = "1cca32fa0182e8c0989459524dc356b8f2b5c10f1b9eb521b7d182c03cf8c5ff"
 
 [[package]]
 name = "libloading"
@@ -1312,9 +1312,9 @@ checksum = "b5eb417147ba9860a96cfe72a0b93bf88fee1744b5636ec99ab20c1aa9376581"
 
 [[package]]
 name = "rowan"
-version = "0.12.2"
+version = "0.12.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5e05df24c035422fb2b845d66ef3542d6c4f8572eafe077175a30787b0254207"
+checksum = "437240cd341f96c5a09924912a221726989c919f69ebce2e289f3adfbce36443"
 dependencies = [
  "countme",
  "hashbrown",
diff --git a/crates/completion/src/completions/flyimport.rs b/crates/completion/src/completions/flyimport.rs
index 6591127b1..9c6a5a40c 100644
--- a/crates/completion/src/completions/flyimport.rs
+++ b/crates/completion/src/completions/flyimport.rs
@@ -68,7 +68,10 @@ pub(crate) fn import_on_the_fly(acc: &mut Completions, ctx: &CompletionContext)
     if !ctx.config.enable_imports_on_the_fly {
         return None;
     }
-    if ctx.attribute_under_caret.is_some() || ctx.mod_declaration_under_caret.is_some() {
+    if ctx.use_item_syntax.is_some()
+        || ctx.attribute_under_caret.is_some()
+        || ctx.mod_declaration_under_caret.is_some()
+    {
         return None;
     }
     let potential_import_name = {
@@ -664,4 +667,22 @@ fn main() {
             "#]],
         );
     }
+
+    #[test]
+    fn no_completions_in_use_statements() {
+        check(
+            r#"
+//- /lib.rs crate:dep
+pub mod io {
+    pub fn stdin() {}
+};
+
+//- /main.rs crate:main deps:dep
+use stdi$0
+
+fn main() {}
+"#,
+            expect![[]],
+        );
+    }
 }
diff --git a/crates/hir_def/src/item_tree.rs b/crates/hir_def/src/item_tree.rs
index 1e5c94660..42d9f0947 100644
--- a/crates/hir_def/src/item_tree.rs
+++ b/crates/hir_def/src/item_tree.rs
@@ -98,15 +98,17 @@ impl ItemTree {
                     ctx.lower_module_items(&items)
                 },
                 ast::MacroStmts(stmts) => {
-                    ctx.lower_inner_items(stmts.syntax())
+                    // The produced statements can include items, which should be added as top-level
+                    // items.
+                    ctx.lower_macro_stmts(stmts)
                 },
-                // Macros can expand to expressions. We return an empty item tree in this case, but
-                // still need to collect inner items.
                 ast::Expr(e) => {
+                    // Macros can expand to expressions. We return an empty item tree in this case, but
+                    // still need to collect inner items.
                     ctx.lower_inner_items(e.syntax())
                 },
                 _ => {
-                    panic!("cannot create item tree from {:?}", syntax);
+                    panic!("cannot create item tree from {:?} {}", syntax, syntax);
                 },
             }
         };
diff --git a/crates/hir_def/src/item_tree/lower.rs b/crates/hir_def/src/item_tree/lower.rs
index 8a71376b9..acc001add 100644
--- a/crates/hir_def/src/item_tree/lower.rs
+++ b/crates/hir_def/src/item_tree/lower.rs
@@ -61,6 +61,32 @@ impl Ctx {
         self.tree
     }
 
+    pub(super) fn lower_macro_stmts(mut self, stmts: ast::MacroStmts) -> ItemTree {
+        self.tree.top_level = stmts
+            .statements()
+            .filter_map(|stmt| match stmt {
+                ast::Stmt::Item(item) => Some(item),
+                _ => None,
+            })
+            .flat_map(|item| self.lower_mod_item(&item, false))
+            .flat_map(|items| items.0)
+            .collect();
+
+        // Non-items need to have their inner items collected.
+        for stmt in stmts.statements() {
+            match stmt {
+                ast::Stmt::ExprStmt(_) | ast::Stmt::LetStmt(_) => {
+                    self.collect_inner_items(stmt.syntax())
+                }
+                _ => {}
+            }
+        }
+        if let Some(expr) = stmts.expr() {
+            self.collect_inner_items(expr.syntax());
+        }
+        self.tree
+    }
+
     pub(super) fn lower_inner_items(mut self, within: &SyntaxNode) -> ItemTree {
         self.collect_inner_items(within);
         self.tree
diff --git a/crates/hir_def/src/nameres.rs b/crates/hir_def/src/nameres.rs
index 005b36e02..6169b3bbc 100644
--- a/crates/hir_def/src/nameres.rs
+++ b/crates/hir_def/src/nameres.rs
@@ -199,16 +199,10 @@ impl DefMap {
 
     pub(crate) fn block_def_map_query(db: &dyn DefDatabase, block_id: BlockId) -> Arc<DefMap> {
         let block: BlockLoc = db.lookup_intern_block(block_id);
-        let item_tree = db.item_tree(block.ast_id.file_id);
-        let block_items = item_tree.inner_items_of_block(block.ast_id.value);
-
         let parent = block.module.def_map(db);
 
-        if block_items.is_empty() {
-            // If there are no inner items, nothing new is brought into scope, so we can just return
-            // the parent DefMap. This keeps DefMap parent chains short.
-            return parent;
-        }
+        // FIXME: It would be good to just return the parent map when the block has no items, but
+        // we rely on `def_map.block` in a few places, which is `Some` for the inner `DefMap`.
 
         let block_info =
             BlockInfo { block: block_id, parent, parent_module: block.module.local_id };
@@ -216,7 +210,7 @@ impl DefMap {
         let mut def_map = DefMap::empty(block.module.krate, block_info.parent.edition);
         def_map.block = Some(block_info);
 
-        let def_map = collector::collect_defs(db, def_map, Some(block.ast_id.value));
+        let def_map = collector::collect_defs(db, def_map, Some(block.ast_id));
         Arc::new(def_map)
     }
 
diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index 761b29c86..ae98fadac 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -48,7 +48,7 @@ const FIXED_POINT_LIMIT: usize = 8192;
 pub(super) fn collect_defs(
     db: &dyn DefDatabase,
     mut def_map: DefMap,
-    block: Option<FileAstId<ast::BlockExpr>>,
+    block: Option<AstId<ast::BlockExpr>>,
 ) -> DefMap {
     let crate_graph = db.crate_graph();
 
@@ -261,11 +261,10 @@ impl DefCollector<'_> {
         }
     }
 
-    fn seed_with_inner(&mut self, block: FileAstId<ast::BlockExpr>) {
-        let file_id = self.db.crate_graph()[self.def_map.krate].root_file_id;
-        let item_tree = self.db.item_tree(file_id.into());
+    fn seed_with_inner(&mut self, block: AstId<ast::BlockExpr>) {
+        let item_tree = self.db.item_tree(block.file_id);
         let module_id = self.def_map.root;
-        self.def_map.modules[module_id].origin = ModuleOrigin::CrateRoot { definition: file_id };
+        self.def_map.modules[module_id].origin = ModuleOrigin::BlockExpr { block };
         if item_tree
             .top_level_attrs(self.db, self.def_map.krate)
             .cfg()
@@ -275,11 +274,11 @@ impl DefCollector<'_> {
                 def_collector: &mut *self,
                 macro_depth: 0,
                 module_id,
-                file_id: file_id.into(),
+                file_id: block.file_id,
                 item_tree: &item_tree,
                 mod_dir: ModDir::root(),
             }
-            .collect(item_tree.inner_items_of_block(block));
+            .collect(item_tree.inner_items_of_block(block.value));
         }
     }
 
diff --git a/crates/hir_def/src/nameres/path_resolution.rs b/crates/hir_def/src/nameres/path_resolution.rs
index 419e465ed..2a0f8ec2b 100644
--- a/crates/hir_def/src/nameres/path_resolution.rs
+++ b/crates/hir_def/src/nameres/path_resolution.rs
@@ -103,7 +103,7 @@ impl DefMap {
         &self,
         db: &dyn DefDatabase,
         mode: ResolveMode,
-        original_module: LocalModuleId,
+        mut original_module: LocalModuleId,
         path: &ModPath,
         shadow: BuiltinShadowMode,
     ) -> ResolvePathResult {
@@ -130,7 +130,10 @@ impl DefMap {
             result.segment_index = result.segment_index.min(new.segment_index);
 
             match &current_map.block {
-                Some(block) => current_map = &block.parent,
+                Some(block) => {
+                    current_map = &block.parent;
+                    original_module = block.parent_module;
+                }
                 None => return result,
             }
         }
diff --git a/crates/hir_def/src/nameres/tests/block.rs b/crates/hir_def/src/nameres/tests/block.rs
index 470ca593e..6cc659513 100644
--- a/crates/hir_def/src/nameres/tests/block.rs
+++ b/crates/hir_def/src/nameres/tests/block.rs
@@ -121,3 +121,66 @@ struct Struct {}
         "#]],
     );
 }
+
+#[test]
+fn legacy_macro_items() {
+    // Checks that legacy-scoped `macro_rules!` from parent namespaces are resolved and expanded
+    // correctly.
+    check_at(
+        r#"
+macro_rules! hit {
+    () => {
+        struct Hit {}
+    }
+}
+
+fn f() {
+    hit!();
+    $0
+}
+"#,
+        expect![[r#"
+            block scope
+            Hit: t
+            crate
+            f: v
+        "#]],
+    );
+}
+
+#[test]
+fn macro_resolve() {
+    check_at(
+        r#"
+//- /lib.rs crate:lib deps:core
+use core::mark;
+
+fn f() {
+    fn nested() {
+        mark::hit!(Hit);
+        $0
+    }
+}
+//- /core.rs crate:core
+pub mod mark {
+    #[macro_export]
+    macro_rules! _hit {
+        ($name:ident) => {
+            struct $name {}
+        }
+    }
+
+    pub use crate::_hit as hit;
+}
+"#,
+        expect![[r#"
+            block scope
+            Hit: t
+            block scope
+            nested: v
+            crate
+            f: v
+            mark: t
+        "#]],
+    );
+}
diff --git a/crates/mbe/src/mbe_expander.rs b/crates/mbe/src/expander.rs
index 802c8fb0f..e7e14b3cc 100644
--- a/crates/mbe/src/mbe_expander.rs
+++ b/crates/mbe/src/expander.rs
@@ -16,13 +16,8 @@ pub(crate) fn expand_rules(
 ) -> ExpandResult<tt::Subtree> {
     let mut match_: Option<(matcher::Match, &crate::Rule)> = None;
     for rule in rules {
-        let new_match = match matcher::match_(&rule.lhs, input) {
-            Ok(m) => m,
-            Err(_e) => {
-                // error in pattern parsing
-                continue;
-            }
-        };
+        let new_match = matcher::match_(&rule.lhs, input);
+
         if new_match.err.is_none() {
             // If we find a rule that applies without errors, we're done.
             // Unconditionally returning the transcription here makes the
diff --git a/crates/mbe/src/mbe_expander/matcher.rs b/crates/mbe/src/expander/matcher.rs
index d32e60521..800931cd1 100644
--- a/crates/mbe/src/mbe_expander/matcher.rs
+++ b/crates/mbe/src/expander/matcher.rs
@@ -1,7 +1,7 @@
 //! FIXME: write short doc here
 
 use crate::{
-    mbe_expander::{Binding, Bindings, Fragment},
+    expander::{Binding, Bindings, Fragment},
     parser::{Op, RepeatKind, Separator},
     subtree_source::SubtreeTokenSource,
     tt_iter::TtIter,
@@ -70,69 +70,38 @@ pub(super) struct Match {
 }
 
 impl Match {
-    pub(super) fn add_err(&mut self, err: ExpandError) {
+    fn add_err(&mut self, err: ExpandError) {
         let prev_err = self.err.take();
         self.err = prev_err.or(Some(err));
         self.err_count += 1;
     }
 }
 
-// General note: These functions have two channels to return errors, a `Result`
-// return value and the `&mut Match`. The returned Result is for pattern parsing
-// errors; if a branch of the macro definition doesn't parse, it doesn't make
-// sense to try using it. Matching errors are added to the `Match`. It might
-// make sense to make pattern parsing a separate step?
-
-pub(super) fn match_(pattern: &MetaTemplate, src: &tt::Subtree) -> Result<Match, ExpandError> {
-    assert!(pattern.delimiter == None);
-
+/// Matching errors are added to the `Match`.
+pub(super) fn match_(pattern: &MetaTemplate, src: &tt::Subtree) -> Match {
     let mut res = Match::default();
     let mut src = TtIter::new(src);
 
-    match_subtree(&mut res, pattern, &mut src)?;
+    match_tokens(&mut res, pattern, &mut src);
 
     if src.len() > 0 {
         res.unmatched_tts += src.len();
         res.add_err(err!("leftover tokens"));
     }
 
-    Ok(res)
+    res
 }
 
-fn match_subtree(
-    res: &mut Match,
-    pattern: &MetaTemplate,
-    src: &mut TtIter,
-) -> Result<(), ExpandError> {
+fn match_tokens(res: &mut Match, pattern: &MetaTemplate, src: &mut TtIter) {
     for op in pattern.iter() {
-        match op.as_ref().map_err(|err| err.clone())? {
+        match op {
             Op::Leaf(lhs) => {
-                let rhs = match src.expect_leaf() {
-                    Ok(l) => l,
-                    Err(()) => {
-                        res.add_err(err!("expected leaf: `{}`", lhs));
-                        continue;
-                    }
-                };
-                match (lhs, rhs) {
-                    (
-                        tt::Leaf::Punct(tt::Punct { char: lhs, .. }),
-                        tt::Leaf::Punct(tt::Punct { char: rhs, .. }),
-                    ) if lhs == rhs => (),
-                    (
-                        tt::Leaf::Ident(tt::Ident { text: lhs, .. }),
-                        tt::Leaf::Ident(tt::Ident { text: rhs, .. }),
-                    ) if lhs == rhs => (),
-                    (
-                        tt::Leaf::Literal(tt::Literal { text: lhs, .. }),
-                        tt::Leaf::Literal(tt::Literal { text: rhs, .. }),
-                    ) if lhs == rhs => (),
-                    _ => {
-                        res.add_err(ExpandError::UnexpectedToken);
-                    }
+                if let Err(err) = match_leaf(lhs, src) {
+                    res.add_err(err);
+                    continue;
                 }
             }
-            Op::Subtree(lhs) => {
+            Op::Subtree { tokens, delimiter: delim } => {
                 let rhs = match src.expect_subtree() {
                     Ok(s) => s,
                     Err(()) => {
@@ -140,12 +109,12 @@ fn match_subtree(
                         continue;
                     }
                 };
-                if lhs.delimiter_kind() != rhs.delimiter_kind() {
+                if delim.map(|it| it.kind) != rhs.delimiter_kind() {
                     res.add_err(err!("mismatched delimiter"));
                     continue;
                 }
                 let mut src = TtIter::new(rhs);
-                match_subtree(res, lhs, &mut src)?;
+                match_tokens(res, tokens, &mut src);
                 if src.len() > 0 {
                     res.add_err(err!("leftover tokens"));
                 }
@@ -171,14 +140,170 @@ fn match_subtree(
                     res.add_err(err);
                 }
             }
-            Op::Repeat { subtree, kind, separator } => {
-                match_repeat(res, subtree, *kind, separator, src)?;
+            Op::Repeat { tokens: subtree, kind, separator } => {
+                match_repeat(res, subtree, *kind, separator, src);
             }
         }
     }
+}
+
+fn match_leaf(lhs: &tt::Leaf, src: &mut TtIter) -> Result<(), ExpandError> {
+    let rhs = match src.expect_leaf() {
+        Ok(l) => l,
+        Err(()) => {
+            return Err(err!("expected leaf: `{}`", lhs));
+        }
+    };
+    match (lhs, rhs) {
+        (
+            tt::Leaf::Punct(tt::Punct { char: lhs, .. }),
+            tt::Leaf::Punct(tt::Punct { char: rhs, .. }),
+        ) if lhs == rhs => (),
+        (
+            tt::Leaf::Ident(tt::Ident { text: lhs, .. }),
+            tt::Leaf::Ident(tt::Ident { text: rhs, .. }),
+        ) if lhs == rhs => (),
+        (
+            tt::Leaf::Literal(tt::Literal { text: lhs, .. }),
+            tt::Leaf::Literal(tt::Literal { text: rhs, .. }),
+        ) if lhs == rhs => (),
+        _ => {
+            return Err(ExpandError::UnexpectedToken);
+        }
+    }
+
     Ok(())
 }
 
+fn match_repeat(
+    res: &mut Match,
+    pattern: &MetaTemplate,
+    kind: RepeatKind,
+    separator: &Option<Separator>,
+    src: &mut TtIter,
+) {
+    // Dirty hack to make macro-expansion terminate.
+    // This should be replaced by a proper macro-by-example implementation
+    let mut limit = 65536;
+    let mut counter = 0;
+
+    for i in 0.. {
+        let mut fork = src.clone();
+
+        if let Some(separator) = &separator {
+            if i != 0 && !fork.eat_separator(separator) {
+                break;
+            }
+        }
+
+        let mut nested = Match::default();
+        match_tokens(&mut nested, pattern, &mut fork);
+        if nested.err.is_none() {
+            limit -= 1;
+            if limit == 0 {
+                log::warn!(
+                    "match_lhs exceeded repeat pattern limit => {:#?}\n{:#?}\n{:#?}\n{:#?}",
+                    pattern,
+                    src,
+                    kind,
+                    separator
+                );
+                break;
+            }
+            *src = fork;
+
+            if let Err(err) = res.bindings.push_nested(counter, nested.bindings) {
+                res.add_err(err);
+            }
+            counter += 1;
+            if counter == 1 {
+                if let RepeatKind::ZeroOrOne = kind {
+                    break;
+                }
+            }
+        } else {
+            break;
+        }
+    }
+
+    match (kind, counter) {
+        (RepeatKind::OneOrMore, 0) => {
+            res.add_err(ExpandError::UnexpectedToken);
+        }
+        (_, 0) => {
+            // Collect all empty variables in subtrees
+            let mut vars = Vec::new();
+            collect_vars(&mut vars, pattern);
+            for var in vars {
+                res.bindings.push_empty(&var)
+            }
+        }
+        _ => (),
+    }
+}
+
+fn match_meta_var(kind: &str, input: &mut TtIter) -> ExpandResult<Option<Fragment>> {
+    let fragment = match kind {
+        "path" => Path,
+        "expr" => Expr,
+        "ty" => Type,
+        "pat" => Pattern,
+        "stmt" => Statement,
+        "block" => Block,
+        "meta" => MetaItem,
+        "item" => Item,
+        _ => {
+            let tt_result = match kind {
+                "ident" => input
+                    .expect_ident()
+                    .map(|ident| Some(tt::Leaf::from(ident.clone()).into()))
+                    .map_err(|()| err!("expected ident")),
+                "tt" => input.expect_tt().map(Some).map_err(|()| err!()),
+                "lifetime" => input
+                    .expect_lifetime()
+                    .map(|tt| Some(tt))
+                    .map_err(|()| err!("expected lifetime")),
+                "literal" => {
+                    let neg = input.eat_char('-');
+                    input
+                        .expect_literal()
+                        .map(|literal| {
+                            let lit = tt::Leaf::from(literal.clone());
+                            match neg {
+                                None => Some(lit.into()),
+                                Some(neg) => Some(tt::TokenTree::Subtree(tt::Subtree {
+                                    delimiter: None,
+                                    token_trees: vec![neg, lit.into()],
+                                })),
+                            }
+                        })
+                        .map_err(|()| err!())
+                }
+                // `vis` is optional
+                "vis" => match input.eat_vis() {
+                    Some(vis) => Ok(Some(vis)),
+                    None => Ok(None),
+                },
+                _ => Err(ExpandError::UnexpectedToken),
+            };
+            return tt_result.map(|it| it.map(Fragment::Tokens)).into();
+        }
+    };
+    let result = input.expect_fragment(fragment);
+    result.map(|tt| if kind == "expr" { tt.map(Fragment::Ast) } else { tt.map(Fragment::Tokens) })
+}
+
+fn collect_vars(buf: &mut Vec<SmolStr>, pattern: &MetaTemplate) {
+    for op in pattern.iter() {
+        match op {
+            Op::Var { name, .. } => buf.push(name.clone()),
+            Op::Leaf(_) => (),
+            Op::Subtree { tokens, .. } => collect_vars(buf, tokens),
+            Op::Repeat { tokens, .. } => collect_vars(buf, tokens),
+        }
+    }
+}
+
 impl<'a> TtIter<'a> {
     fn eat_separator(&mut self, separator: &Separator) -> bool {
         let mut fork = self.clone();
@@ -206,7 +331,7 @@ impl<'a> TtIter<'a> {
         ok
     }
 
-    pub(crate) fn expect_tt(&mut self) -> Result<tt::TokenTree, ()> {
+    fn expect_tt(&mut self) -> Result<tt::TokenTree, ()> {
         match self.peek_n(0) {
             Some(tt::TokenTree::Leaf(tt::Leaf::Punct(punct))) if punct.char == '\'' => {
                 return self.expect_lifetime();
@@ -267,7 +392,7 @@ impl<'a> TtIter<'a> {
         }
     }
 
-    pub(crate) fn expect_lifetime(&mut self) -> Result<tt::TokenTree, ()> {
+    fn expect_lifetime(&mut self) -> Result<tt::TokenTree, ()> {
         let punct = self.expect_punct()?;
         if punct.char != '\'' {
             return Err(());
@@ -284,13 +409,13 @@ impl<'a> TtIter<'a> {
         .into())
     }
 
-    pub(crate) fn expect_fragment(
+    fn expect_fragment(
         &mut self,
         fragment_kind: parser::FragmentKind,
     ) -> ExpandResult<Option<tt::TokenTree>> {
-        pub(crate) struct OffsetTokenSink<'a> {
-            pub(crate) cursor: Cursor<'a>,
-            pub(crate) error: bool,
+        struct OffsetTokenSink<'a> {
+            cursor: Cursor<'a>,
+            error: bool,
         }
 
         impl<'a> TreeSink for OffsetTokenSink<'a> {
@@ -346,7 +471,7 @@ impl<'a> TtIter<'a> {
         ExpandResult { value: res, err }
     }
 
-    pub(crate) fn eat_vis(&mut self) -> Option<tt::TokenTree> {
+    fn eat_vis(&mut self) -> Option<tt::TokenTree> {
         let mut fork = self.clone();
         match fork.expect_fragment(Visibility) {
             ExpandResult { value: tt, err: None } => {
@@ -357,7 +482,7 @@ impl<'a> TtIter<'a> {
         }
     }
 
-    pub(crate) fn eat_char(&mut self, c: char) -> Option<tt::TokenTree> {
+    fn eat_char(&mut self, c: char) -> Option<tt::TokenTree> {
         let mut fork = self.clone();
         match fork.expect_char(c) {
             Ok(_) => {
@@ -369,134 +494,3 @@ impl<'a> TtIter<'a> {
         }
     }
 }
-
-pub(super) fn match_repeat(
-    res: &mut Match,
-    pattern: &MetaTemplate,
-    kind: RepeatKind,
-    separator: &Option<Separator>,
-    src: &mut TtIter,
-) -> Result<(), ExpandError> {
-    // Dirty hack to make macro-expansion terminate.
-    // This should be replaced by a proper macro-by-example implementation
-    let mut limit = 65536;
-    let mut counter = 0;
-
-    for i in 0.. {
-        let mut fork = src.clone();
-
-        if let Some(separator) = &separator {
-            if i != 0 && !fork.eat_separator(separator) {
-                break;
-            }
-        }
-
-        let mut nested = Match::default();
-        match_subtree(&mut nested, pattern, &mut fork)?;
-        if nested.err.is_none() {
-            limit -= 1;
-            if limit == 0 {
-                log::warn!(
-                    "match_lhs exceeded repeat pattern limit => {:#?}\n{:#?}\n{:#?}\n{:#?}",
-                    pattern,
-                    src,
-                    kind,
-                    separator
-                );
-                break;
-            }
-            *src = fork;
-
-            if let Err(err) = res.bindings.push_nested(counter, nested.bindings) {
-                res.add_err(err);
-            }
-            counter += 1;
-            if counter == 1 {
-                if let RepeatKind::ZeroOrOne = kind {
-                    break;
-                }
-            }
-        } else {
-            break;
-        }
-    }
-
-    match (kind, counter) {
-        (RepeatKind::OneOrMore, 0) => {
-            res.add_err(ExpandError::UnexpectedToken);
-        }
-        (_, 0) => {
-            // Collect all empty variables in subtrees
-            let mut vars = Vec::new();
-            collect_vars(&mut vars, pattern)?;
-            for var in vars {
-                res.bindings.push_empty(&var)
-            }
-        }
-        _ => (),
-    }
-    Ok(())
-}
-
-fn match_meta_var(kind: &str, input: &mut TtIter) -> ExpandResult<Option<Fragment>> {
-    let fragment = match kind {
-        "path" => Path,
-        "expr" => Expr,
-        "ty" => Type,
-        "pat" => Pattern,
-        "stmt" => Statement,
-        "block" => Block,
-        "meta" => MetaItem,
-        "item" => Item,
-        _ => {
-            let tt_result = match kind {
-                "ident" => input
-                    .expect_ident()
-                    .map(|ident| Some(tt::Leaf::from(ident.clone()).into()))
-                    .map_err(|()| err!("expected ident")),
-                "tt" => input.expect_tt().map(Some).map_err(|()| err!()),
-                "lifetime" => input
-                    .expect_lifetime()
-                    .map(|tt| Some(tt))
-                    .map_err(|()| err!("expected lifetime")),
-                "literal" => {
-                    let neg = input.eat_char('-');
-                    input
-                        .expect_literal()
-                        .map(|literal| {
-                            let lit = tt::Leaf::from(literal.clone());
-                            match neg {
-                                None => Some(lit.into()),
-                                Some(neg) => Some(tt::TokenTree::Subtree(tt::Subtree {
-                                    delimiter: None,
-                                    token_trees: vec![neg, lit.into()],
-                                })),
-                            }
-                        })
-                        .map_err(|()| err!())
-                }
-                // `vis` is optional
-                "vis" => match input.eat_vis() {
-                    Some(vis) => Ok(Some(vis)),
-                    None => Ok(None),
-                },
-                _ => Err(ExpandError::UnexpectedToken),
-            };
-            return tt_result.map(|it| it.map(Fragment::Tokens)).into();
-        }
-    };
-    let result = input.expect_fragment(fragment);
-    result.map(|tt| if kind == "expr" { tt.map(Fragment::Ast) } else { tt.map(Fragment::Tokens) })
-}
-
-fn collect_vars(buf: &mut Vec<SmolStr>, pattern: &MetaTemplate) -> Result<(), ExpandError> {
-    for op in pattern.iter() {
-        match op.as_ref().map_err(|e| e.clone())? {
-            Op::Var { name, .. } => buf.push(name.clone()),
-            Op::Leaf(_) => (),
-            Op::Subtree(subtree) => collect_vars(buf, subtree)?,
-            Op::Repeat { subtree, .. } => collect_vars(buf, subtree)?,
-        }
-    }
-    Ok(())
-}
diff --git a/crates/mbe/src/mbe_expander/transcriber.rs b/crates/mbe/src/expander/transcriber.rs
index 59a3c80a8..78368a33e 100644
--- a/crates/mbe/src/mbe_expander/transcriber.rs
+++ b/crates/mbe/src/expander/transcriber.rs
@@ -2,10 +2,11 @@
 //! `$ident => foo`, interpolates variables in the template, to get `fn foo() {}`
 
 use syntax::SmolStr;
+use tt::Delimiter;
 
 use super::ExpandResult;
 use crate::{
-    mbe_expander::{Binding, Bindings, Fragment},
+    expander::{Binding, Bindings, Fragment},
     parser::{Op, RepeatKind, Separator},
     ExpandError, MetaTemplate,
 };
@@ -54,10 +55,9 @@ pub(super) fn transcribe(
     template: &MetaTemplate,
     bindings: &Bindings,
 ) -> ExpandResult<tt::Subtree> {
-    assert!(template.delimiter == None);
     let mut ctx = ExpandCtx { bindings: &bindings, nesting: Vec::new() };
     let mut arena: Vec<tt::TokenTree> = Vec::new();
-    expand_subtree(&mut ctx, template, &mut arena)
+    expand_subtree(&mut ctx, template, None, &mut arena)
 }
 
 #[derive(Debug)]
@@ -80,23 +80,18 @@ struct ExpandCtx<'a> {
 fn expand_subtree(
     ctx: &mut ExpandCtx,
     template: &MetaTemplate,
+    delimiter: Option<Delimiter>,
     arena: &mut Vec<tt::TokenTree>,
 ) -> ExpandResult<tt::Subtree> {
     // remember how many elements are in the arena now - when returning, we want to drain exactly how many elements we added. This way, the recursive uses of the arena get their own "view" of the arena, but will reuse the allocation
     let start_elements = arena.len();
     let mut err = None;
     for op in template.iter() {
-        let op = match op {
-            Ok(op) => op,
-            Err(e) => {
-                err = Some(e.clone());
-                break;
-            }
-        };
         match op {
             Op::Leaf(tt) => arena.push(tt.clone().into()),
-            Op::Subtree(tt) => {
-                let ExpandResult { value: tt, err: e } = expand_subtree(ctx, &tt, arena);
+            Op::Subtree { tokens, delimiter } => {
+                let ExpandResult { value: tt, err: e } =
+                    expand_subtree(ctx, &tokens, *delimiter, arena);
                 err = err.or(e);
                 arena.push(tt.into());
             }
@@ -105,7 +100,7 @@ fn expand_subtree(
                 err = err.or(e);
                 push_fragment(arena, fragment);
             }
-            Op::Repeat { subtree, kind, separator } => {
+            Op::Repeat { tokens: subtree, kind, separator } => {
                 let ExpandResult { value: fragment, err: e } =
                     expand_repeat(ctx, subtree, *kind, separator, arena);
                 err = err.or(e);
@@ -115,7 +110,7 @@ fn expand_subtree(
     }
     // drain the elements added in this instance of expand_subtree
     let tts = arena.drain(start_elements..arena.len()).collect();
-    ExpandResult { value: tt::Subtree { delimiter: template.delimiter, token_trees: tts }, err }
+    ExpandResult { value: tt::Subtree { delimiter, token_trees: tts }, err }
 }
 
 fn expand_var(ctx: &mut ExpandCtx, v: &SmolStr, id: tt::TokenId) -> ExpandResult<Fragment> {
@@ -169,7 +164,7 @@ fn expand_repeat(
     let mut counter = 0;
 
     loop {
-        let ExpandResult { value: mut t, err: e } = expand_subtree(ctx, template, arena);
+        let ExpandResult { value: mut t, err: e } = expand_subtree(ctx, template, None, arena);
         let nesting_state = ctx.nesting.last_mut().unwrap();
         if nesting_state.at_end || !nesting_state.hit {
             break;
diff --git a/crates/mbe/src/lib.rs b/crates/mbe/src/lib.rs
index 35cde5f10..d80bd7a33 100644
--- a/crates/mbe/src/lib.rs
+++ b/crates/mbe/src/lib.rs
@@ -4,7 +4,7 @@
 //! `TokenTree`s as well!
 
 mod parser;
-mod mbe_expander;
+mod expander;
 mod syntax_bridge;
 mod tt_iter;
 mod subtree_source;
@@ -24,7 +24,9 @@ use crate::{
 
 #[derive(Debug, PartialEq, Eq)]
 pub enum ParseError {
+    UnexpectedToken(String),
     Expected(String),
+    InvalidRepeat,
     RepetitionEmptyTokenTree,
 }
 
@@ -34,7 +36,6 @@ pub enum ExpandError {
     UnexpectedToken,
     BindingError(String),
     ConversionError,
-    InvalidRepeat,
     ProcMacroError(tt::ExpansionError),
     UnresolvedProcMacro,
     Other(String),
@@ -53,7 +54,6 @@ impl fmt::Display for ExpandError {
             ExpandError::UnexpectedToken => f.write_str("unexpected token in input"),
             ExpandError::BindingError(e) => f.write_str(e),
             ExpandError::ConversionError => f.write_str("could not convert tokens"),
-            ExpandError::InvalidRepeat => f.write_str("invalid repeat expression"),
             ExpandError::ProcMacroError(e) => e.fmt(f),
             ExpandError::UnresolvedProcMacro => f.write_str("unresolved proc macro"),
             ExpandError::Other(e) => f.write_str(e),
@@ -92,18 +92,11 @@ struct Rule {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
-struct MetaTemplate {
-    delimiter: Option<Delimiter>,
-    tokens: Vec<Result<Op, ExpandError>>,
-}
+struct MetaTemplate(Vec<Op>);
 
 impl<'a> MetaTemplate {
-    fn iter(&self) -> impl Iterator<Item = &Result<Op, ExpandError>> {
-        self.tokens.iter()
-    }
-
-    fn delimiter_kind(&self) -> Option<DelimiterKind> {
-        self.delimiter.map(|it| it.kind)
+    fn iter(&self) -> impl Iterator<Item = &Op> {
+        self.0.iter()
     }
 }
 
@@ -209,7 +202,7 @@ impl MacroRules {
         // apply shift
         let mut tt = tt.clone();
         self.shift.shift_all(&mut tt);
-        mbe_expander::expand_rules(&self.rules, &tt)
+        expander::expand_rules(&self.rules, &tt)
     }
 
     pub fn map_id_down(&self, id: tt::TokenId) -> tt::TokenId {
@@ -260,7 +253,7 @@ impl MacroDef {
         // apply shift
         let mut tt = tt.clone();
         self.shift.shift_all(&mut tt);
-        mbe_expander::expand_rules(&self.rules, &tt)
+        expander::expand_rules(&self.rules, &tt)
     }
 
     pub fn map_id_down(&self, id: tt::TokenId) -> tt::TokenId {
@@ -288,47 +281,38 @@ impl Rule {
             .expect_subtree()
             .map_err(|()| ParseError::Expected("expected subtree".to_string()))?;
 
-        let lhs = MetaTemplate { tokens: parse_pattern(&lhs), delimiter: None };
-        let rhs = MetaTemplate { tokens: parse_template(&rhs), delimiter: None };
+        let lhs = MetaTemplate(parse_pattern(&lhs)?);
+        let rhs = MetaTemplate(parse_template(&rhs)?);
 
         Ok(crate::Rule { lhs, rhs })
     }
 }
 
-fn to_parse_error(e: &ExpandError) -> ParseError {
-    let msg = match e {
-        ExpandError::InvalidRepeat => "invalid repeat".to_string(),
-        _ => "invalid macro definition".to_string(),
-    };
-    ParseError::Expected(msg)
-}
-
 fn validate(pattern: &MetaTemplate) -> Result<(), ParseError> {
     for op in pattern.iter() {
-        let op = op.as_ref().map_err(|e| to_parse_error(&e))?;
-
         match op {
-            Op::Subtree(subtree) => validate(&subtree)?,
-            Op::Repeat { subtree, separator, .. } => {
+            Op::Subtree { tokens, .. } => validate(&tokens)?,
+            Op::Repeat { tokens: subtree, separator, .. } => {
                 // Checks that no repetition which could match an empty token
                 // https://github.com/rust-lang/rust/blob/a58b1ed44f5e06976de2bdc4d7dc81c36a96934f/src/librustc_expand/mbe/macro_rules.rs#L558
 
                 if separator.is_none() {
                     if subtree.iter().all(|child_op| {
-                        match child_op.as_ref().map_err(to_parse_error) {
-                            Ok(Op::Var { kind, .. }) => {
+                        match child_op {
+                            Op::Var { kind, .. } => {
                                 // vis is optional
                                 if kind.as_ref().map_or(false, |it| it == "vis") {
                                     return true;
                                 }
                             }
-                            Ok(Op::Repeat { kind, .. }) => {
+                            Op::Repeat { kind, .. } => {
                                 return matches!(
                                     kind,
                                     parser::RepeatKind::ZeroOrMore | parser::RepeatKind::ZeroOrOne
                                 )
                             }
-                            _ => {}
+                            Op::Leaf(_) => {}
+                            Op::Subtree { .. } => {}
                         }
                         false
                     }) {
diff --git a/crates/mbe/src/parser.rs b/crates/mbe/src/parser.rs
index f3047972d..f891ec29c 100644
--- a/crates/mbe/src/parser.rs
+++ b/crates/mbe/src/parser.rs
@@ -3,15 +3,16 @@
 
 use smallvec::SmallVec;
 use syntax::SmolStr;
+use tt::Delimiter;
 
-use crate::{tt_iter::TtIter, ExpandError, MetaTemplate};
+use crate::{tt_iter::TtIter, MetaTemplate, ParseError};
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub(crate) enum Op {
     Var { name: SmolStr, kind: Option<SmolStr>, id: tt::TokenId },
-    Repeat { subtree: MetaTemplate, kind: RepeatKind, separator: Option<Separator> },
+    Repeat { tokens: MetaTemplate, kind: RepeatKind, separator: Option<Separator> },
     Leaf(tt::Leaf),
-    Subtree(MetaTemplate),
+    Subtree { tokens: MetaTemplate, delimiter: Option<Delimiter> },
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -46,12 +47,12 @@ impl PartialEq for Separator {
     }
 }
 
-pub(crate) fn parse_template(template: &tt::Subtree) -> Vec<Result<Op, ExpandError>> {
-    parse_inner(&template, Mode::Template)
+pub(crate) fn parse_template(template: &tt::Subtree) -> Result<Vec<Op>, ParseError> {
+    parse_inner(&template, Mode::Template).into_iter().collect()
 }
 
-pub(crate) fn parse_pattern(pattern: &tt::Subtree) -> Vec<Result<Op, ExpandError>> {
-    parse_inner(&pattern, Mode::Pattern)
+pub(crate) fn parse_pattern(pattern: &tt::Subtree) -> Result<Vec<Op>, ParseError> {
+    parse_inner(&pattern, Mode::Pattern).into_iter().collect()
 }
 
 #[derive(Clone, Copy)]
@@ -60,7 +61,7 @@ enum Mode {
     Template,
 }
 
-fn parse_inner(tt: &tt::Subtree, mode: Mode) -> Vec<Result<Op, ExpandError>> {
+fn parse_inner(tt: &tt::Subtree, mode: Mode) -> Vec<Result<Op, ParseError>> {
     let mut src = TtIter::new(&tt);
     std::iter::from_fn(move || {
         let first = src.next()?;
@@ -71,7 +72,7 @@ fn parse_inner(tt: &tt::Subtree, mode: Mode) -> Vec<Result<Op, ExpandError>> {
 
 macro_rules! err {
     ($($tt:tt)*) => {
-        ExpandError::UnexpectedToken
+        ParseError::UnexpectedToken(($($tt)*).to_string())
     };
 }
 
@@ -81,7 +82,7 @@ macro_rules! bail {
     };
 }
 
-fn next_op<'a>(first: &tt::TokenTree, src: &mut TtIter<'a>, mode: Mode) -> Result<Op, ExpandError> {
+fn next_op<'a>(first: &tt::TokenTree, src: &mut TtIter<'a>, mode: Mode) -> Result<Op, ParseError> {
     let res = match first {
         tt::TokenTree::Leaf(leaf @ tt::Leaf::Punct(tt::Punct { char: '$', .. })) => {
             // Note that the '$' itself is a valid token inside macro_rules.
@@ -92,17 +93,17 @@ fn next_op<'a>(first: &tt::TokenTree, src: &mut TtIter<'a>, mode: Mode) -> Resul
             match second {
                 tt::TokenTree::Subtree(subtree) => {
                     let (separator, kind) = parse_repeat(src)?;
-                    let delimiter = subtree.delimiter;
-                    let tokens = parse_inner(&subtree, mode);
-                    let subtree = MetaTemplate { tokens, delimiter };
-                    Op::Repeat { subtree, separator, kind }
+                    let tokens = parse_inner(&subtree, mode)
+                        .into_iter()
+                        .collect::<Result<Vec<Op>, ParseError>>()?;
+                    Op::Repeat { tokens: MetaTemplate(tokens), separator, kind }
                 }
                 tt::TokenTree::Leaf(leaf) => match leaf {
                     tt::Leaf::Punct(punct) => {
                         static UNDERSCORE: SmolStr = SmolStr::new_inline("_");
 
                         if punct.char != '_' {
-                            return Err(ExpandError::UnexpectedToken);
+                            return Err(ParseError::Expected("_".to_string()));
                         }
                         let name = UNDERSCORE.clone();
                         let kind = eat_fragment_kind(src, mode)?;
@@ -134,16 +135,15 @@ fn next_op<'a>(first: &tt::TokenTree, src: &mut TtIter<'a>, mode: Mode) -> Resul
         }
         tt::TokenTree::Leaf(tt) => Op::Leaf(tt.clone()),
         tt::TokenTree::Subtree(subtree) => {
-            let delimiter = subtree.delimiter;
-            let tokens = parse_inner(&subtree, mode);
-            let subtree = MetaTemplate { tokens, delimiter };
-            Op::Subtree(subtree)
+            let tokens =
+                parse_inner(&subtree, mode).into_iter().collect::<Result<Vec<Op>, ParseError>>()?;
+            Op::Subtree { tokens: MetaTemplate(tokens), delimiter: subtree.delimiter }
         }
     };
     Ok(res)
 }
 
-fn eat_fragment_kind<'a>(src: &mut TtIter<'a>, mode: Mode) -> Result<Option<SmolStr>, ExpandError> {
+fn eat_fragment_kind<'a>(src: &mut TtIter<'a>, mode: Mode) -> Result<Option<SmolStr>, ParseError> {
     if let Mode::Pattern = mode {
         src.expect_char(':').map_err(|()| err!("bad fragment specifier 1"))?;
         let ident = src.expect_ident().map_err(|()| err!("bad fragment specifier 1"))?;
@@ -156,12 +156,12 @@ fn is_boolean_literal(lit: &tt::Literal) -> bool {
     matches!(lit.text.as_str(), "true" | "false")
 }
 
-fn parse_repeat(src: &mut TtIter) -> Result<(Option<Separator>, RepeatKind), ExpandError> {
+fn parse_repeat(src: &mut TtIter) -> Result<(Option<Separator>, RepeatKind), ParseError> {
     let mut separator = Separator::Puncts(SmallVec::new());
     for tt in src {
         let tt = match tt {
             tt::TokenTree::Leaf(leaf) => leaf,
-            tt::TokenTree::Subtree(_) => return Err(ExpandError::InvalidRepeat),
+            tt::TokenTree::Subtree(_) => return Err(ParseError::InvalidRepeat),
         };
         let has_sep = match &separator {
             Separator::Puncts(puncts) => !puncts.is_empty(),
@@ -169,7 +169,7 @@ fn parse_repeat(src: &mut TtIter) -> Result<(Option<Separator>, RepeatKind), Exp
         };
         match tt {
             tt::Leaf::Ident(_) | tt::Leaf::Literal(_) if has_sep => {
-                return Err(ExpandError::InvalidRepeat)
+                return Err(ParseError::InvalidRepeat)
             }
             tt::Leaf::Ident(ident) => separator = Separator::Ident(ident.clone()),
             tt::Leaf::Literal(lit) => separator = Separator::Literal(lit.clone()),
@@ -182,11 +182,11 @@ fn parse_repeat(src: &mut TtIter) -> Result<(Option<Separator>, RepeatKind), Exp
                         match &mut separator {
                             Separator::Puncts(puncts) => {
                                 if puncts.len() == 3 {
-                                    return Err(ExpandError::InvalidRepeat);
+                                    return Err(ParseError::InvalidRepeat);
                                 }
                                 puncts.push(punct.clone())
                             }
-                            _ => return Err(ExpandError::InvalidRepeat),
+                            _ => return Err(ParseError::InvalidRepeat),
                         }
                         continue;
                     }
@@ -196,5 +196,5 @@ fn parse_repeat(src: &mut TtIter) -> Result<(Option<Separator>, RepeatKind), Exp
             }
         }
     }
-    Err(ExpandError::InvalidRepeat)
+    Err(ParseError::InvalidRepeat)
 }
diff --git a/crates/mbe/src/tests.rs b/crates/mbe/src/tests.rs
index 8d978163d..1c467facd 100644
--- a/crates/mbe/src/tests.rs
+++ b/crates/mbe/src/tests.rs
@@ -33,19 +33,18 @@ mod rule_parsing {
 
     #[test]
     fn test_invalid_arms() {
-        fn check(macro_body: &str, err: &str) {
+        fn check(macro_body: &str, err: ParseError) {
             let m = parse_macro_arm(macro_body);
-            assert_eq!(m, Err(ParseError::Expected(String::from(err))));
+            assert_eq!(m, Err(err.into()));
         }
+        check("invalid", ParseError::Expected("expected subtree".into()));
 
-        check("invalid", "expected subtree");
+        check("$i:ident => ()", ParseError::Expected("expected subtree".into()));
+        check("($i:ident) ()", ParseError::Expected("expected `=`".into()));
+        check("($($i:ident)_) => ()", ParseError::InvalidRepeat);
 
-        check("$i:ident => ()", "expected subtree");
-        check("($i:ident) ()", "expected `=`");
-        check("($($i:ident)_) => ()", "invalid repeat");
-
-        check("($i) => ($i)", "invalid macro definition");
-        check("($i:) => ($i)", "invalid macro definition");
+        check("($i) => ($i)", ParseError::UnexpectedToken("bad fragment specifier 1".into()));
+        check("($i:) => ($i)", ParseError::UnexpectedToken("bad fragment specifier 1".into()));
     }
 
     fn parse_macro_arm(arm_definition: &str) -> Result<crate::MacroRules, ParseError> {
diff --git a/crates/project_model/src/build_data.rs b/crates/project_model/src/build_data.rs
index 3ff347e2c..a5c564e0a 100644
--- a/crates/project_model/src/build_data.rs
+++ b/crates/project_model/src/build_data.rs
@@ -5,10 +5,11 @@ use std::{
     io::BufReader,
     path::{Path, PathBuf},
     process::{Command, Stdio},
+    sync::Arc,
 };
 
 use anyhow::Result;
-use cargo_metadata::{BuildScript, Message, Package, PackageId};
+use cargo_metadata::{BuildScript, Message};
 use itertools::Itertools;
 use paths::{AbsPath, AbsPathBuf};
 use rustc_hash::FxHashMap;
@@ -16,150 +17,195 @@ use stdx::JodChild;
 
 use crate::{cfg_flag::CfgFlag, CargoConfig};
 
-#[derive(Debug, Clone, Default)]
-pub(crate) struct BuildDataMap {
-    data: FxHashMap<PackageId, BuildData>,
-}
 #[derive(Debug, Clone, Default, PartialEq, Eq)]
-pub struct BuildData {
+pub(crate) struct BuildData {
     /// List of config flags defined by this package's build script
-    pub cfgs: Vec<CfgFlag>,
+    pub(crate) cfgs: Vec<CfgFlag>,
     /// List of cargo-related environment variables with their value
     ///
     /// If the package has a build script which defines environment variables,
     /// they can also be found here.
-    pub envs: Vec<(String, String)>,
+    pub(crate) envs: Vec<(String, String)>,
     /// Directory where a build script might place its output
-    pub out_dir: Option<AbsPathBuf>,
+    pub(crate) out_dir: Option<AbsPathBuf>,
     /// Path to the proc-macro library file if this package exposes proc-macros
-    pub proc_macro_dylib_path: Option<AbsPathBuf>,
+    pub(crate) proc_macro_dylib_path: Option<AbsPathBuf>,
 }
 
-impl BuildDataMap {
-    pub(crate) fn new(
-        cargo_toml: &AbsPath,
-        cargo_features: &CargoConfig,
-        packages: &Vec<Package>,
-        progress: &dyn Fn(String),
-    ) -> Result<BuildDataMap> {
-        let mut cmd = Command::new(toolchain::cargo());
-        cmd.args(&["check", "--workspace", "--message-format=json", "--manifest-path"])
-            .arg(cargo_toml.as_ref());
-
-        // --all-targets includes tests, benches and examples in addition to the
-        // default lib and bins. This is an independent concept from the --targets
-        // flag below.
-        cmd.arg("--all-targets");
-
-        if let Some(target) = &cargo_features.target {
-            cmd.args(&["--target", target]);
-        }
+#[derive(Clone, Debug)]
+pub(crate) struct BuildDataConfig {
+    cargo_toml: AbsPathBuf,
+    cargo_features: CargoConfig,
+    packages: Arc<Vec<cargo_metadata::Package>>,
+}
 
-        if cargo_features.all_features {
-            cmd.arg("--all-features");
-        } else {
-            if cargo_features.no_default_features {
-                // FIXME: `NoDefaultFeatures` is mutual exclusive with `SomeFeatures`
-                // https://github.com/oli-obk/cargo_metadata/issues/79
-                cmd.arg("--no-default-features");
-            }
-            if !cargo_features.features.is_empty() {
-                cmd.arg("--features");
-                cmd.arg(cargo_features.features.join(" "));
-            }
-        }
+impl PartialEq for BuildDataConfig {
+    fn eq(&self, other: &Self) -> bool {
+        Arc::ptr_eq(&self.packages, &other.packages)
+    }
+}
 
-        cmd.stdout(Stdio::piped()).stderr(Stdio::null()).stdin(Stdio::null());
-
-        let mut child = cmd.spawn().map(JodChild)?;
-        let child_stdout = child.stdout.take().unwrap();
-        let stdout = BufReader::new(child_stdout);
-
-        let mut res = BuildDataMap::default();
-        for message in cargo_metadata::Message::parse_stream(stdout) {
-            if let Ok(message) = message {
-                match message {
-                    Message::BuildScriptExecuted(BuildScript {
-                        package_id,
-                        out_dir,
-                        cfgs,
-                        env,
-                        ..
-                    }) => {
-                        let cfgs = {
-                            let mut acc = Vec::new();
-                            for cfg in cfgs {
-                                match cfg.parse::<CfgFlag>() {
-                                    Ok(it) => acc.push(it),
-                                    Err(err) => {
-                                        anyhow::bail!("invalid cfg from cargo-metadata: {}", err)
-                                    }
-                                };
-                            }
-                            acc
-                        };
-                        let res = res.data.entry(package_id.clone()).or_default();
-                        // cargo_metadata crate returns default (empty) path for
-                        // older cargos, which is not absolute, so work around that.
-                        if out_dir != PathBuf::default() {
-                            let out_dir = AbsPathBuf::assert(out_dir);
-                            res.out_dir = Some(out_dir);
-                            res.cfgs = cfgs;
-                        }
+impl Eq for BuildDataConfig {}
 
-                        res.envs = env;
-                    }
-                    Message::CompilerArtifact(message) => {
-                        progress(format!("metadata {}", message.target.name));
-
-                        if message.target.kind.contains(&"proc-macro".to_string()) {
-                            let package_id = message.package_id;
-                            // Skip rmeta file
-                            if let Some(filename) =
-                                message.filenames.iter().find(|name| is_dylib(name))
-                            {
-                                let filename = AbsPathBuf::assert(filename.clone());
-                                let res = res.data.entry(package_id.clone()).or_default();
-                                res.proc_macro_dylib_path = Some(filename);
-                            }
-                        }
-                    }
-                    Message::CompilerMessage(message) => {
-                        progress(message.target.name.clone());
-                    }
-                    Message::Unknown => (),
-                    Message::BuildFinished(_) => {}
-                    Message::TextLine(_) => {}
-                }
-            }
+#[derive(Debug, Default)]
+pub struct BuildDataCollector {
+    configs: FxHashMap<AbsPathBuf, BuildDataConfig>,
+}
+
+#[derive(Debug, Default, PartialEq, Eq)]
+pub struct BuildDataResult {
+    data: FxHashMap<AbsPathBuf, BuildDataMap>,
+}
+
+pub(crate) type BuildDataMap = FxHashMap<String, BuildData>;
+
+impl BuildDataCollector {
+    pub(crate) fn add_config(&mut self, workspace_root: &AbsPath, config: BuildDataConfig) {
+        self.configs.insert(workspace_root.to_path_buf().clone(), config);
+    }
+
+    pub fn collect(&mut self, progress: &dyn Fn(String)) -> Result<BuildDataResult> {
+        let mut res = BuildDataResult::default();
+        for (path, config) in self.configs.iter() {
+            res.data.insert(
+                path.clone(),
+                collect_from_workspace(
+                    &config.cargo_toml,
+                    &config.cargo_features,
+                    &config.packages,
+                    progress,
+                )?,
+            );
         }
-        res.inject_cargo_env(packages);
         Ok(res)
     }
+}
+
+impl BuildDataResult {
+    pub(crate) fn get(&self, root: &AbsPath) -> Option<&BuildDataMap> {
+        self.data.get(&root.to_path_buf())
+    }
+}
 
-    pub(crate) fn with_cargo_env(packages: &Vec<Package>) -> Self {
-        let mut res = Self::default();
-        res.inject_cargo_env(packages);
-        res
+impl BuildDataConfig {
+    pub(crate) fn new(
+        cargo_toml: AbsPathBuf,
+        cargo_features: CargoConfig,
+        packages: Arc<Vec<cargo_metadata::Package>>,
+    ) -> Self {
+        Self { cargo_toml, cargo_features, packages }
     }
+}
 
-    pub(crate) fn get(&self, id: &PackageId) -> Option<&BuildData> {
-        self.data.get(id)
+fn collect_from_workspace(
+    cargo_toml: &AbsPath,
+    cargo_features: &CargoConfig,
+    packages: &Vec<cargo_metadata::Package>,
+    progress: &dyn Fn(String),
+) -> Result<BuildDataMap> {
+    let mut cmd = Command::new(toolchain::cargo());
+    cmd.args(&["check", "--workspace", "--message-format=json", "--manifest-path"])
+        .arg(cargo_toml.as_ref());
+
+    // --all-targets includes tests, benches and examples in addition to the
+    // default lib and bins. This is an independent concept from the --targets
+    // flag below.
+    cmd.arg("--all-targets");
+
+    if let Some(target) = &cargo_features.target {
+        cmd.args(&["--target", target]);
     }
 
-    fn inject_cargo_env(&mut self, packages: &Vec<Package>) {
-        for meta_pkg in packages {
-            let resource = self.data.entry(meta_pkg.id.clone()).or_default();
-            inject_cargo_env(meta_pkg, &mut resource.envs);
+    if cargo_features.all_features {
+        cmd.arg("--all-features");
+    } else {
+        if cargo_features.no_default_features {
+            // FIXME: `NoDefaultFeatures` is mutual exclusive with `SomeFeatures`
+            // https://github.com/oli-obk/cargo_metadata/issues/79
+            cmd.arg("--no-default-features");
+        }
+        if !cargo_features.features.is_empty() {
+            cmd.arg("--features");
+            cmd.arg(cargo_features.features.join(" "));
+        }
+    }
+
+    cmd.stdout(Stdio::piped()).stderr(Stdio::null()).stdin(Stdio::null());
 
-            if let Some(out_dir) = &resource.out_dir {
-                // NOTE: cargo and rustc seem to hide non-UTF-8 strings from env! and option_env!()
-                if let Some(out_dir) = out_dir.to_str().map(|s| s.to_owned()) {
-                    resource.envs.push(("OUT_DIR".to_string(), out_dir));
+    let mut child = cmd.spawn().map(JodChild)?;
+    let child_stdout = child.stdout.take().unwrap();
+    let stdout = BufReader::new(child_stdout);
+
+    let mut res = BuildDataMap::default();
+    for message in cargo_metadata::Message::parse_stream(stdout) {
+        if let Ok(message) = message {
+            match message {
+                Message::BuildScriptExecuted(BuildScript {
+                    package_id,
+                    out_dir,
+                    cfgs,
+                    env,
+                    ..
+                }) => {
+                    let cfgs = {
+                        let mut acc = Vec::new();
+                        for cfg in cfgs {
+                            match cfg.parse::<CfgFlag>() {
+                                Ok(it) => acc.push(it),
+                                Err(err) => {
+                                    anyhow::bail!("invalid cfg from cargo-metadata: {}", err)
+                                }
+                            };
+                        }
+                        acc
+                    };
+                    let res = res.entry(package_id.repr.clone()).or_default();
+                    // cargo_metadata crate returns default (empty) path for
+                    // older cargos, which is not absolute, so work around that.
+                    if out_dir != PathBuf::default() {
+                        let out_dir = AbsPathBuf::assert(out_dir);
+                        res.out_dir = Some(out_dir);
+                        res.cfgs = cfgs;
+                    }
+
+                    res.envs = env;
+                }
+                Message::CompilerArtifact(message) => {
+                    progress(format!("metadata {}", message.target.name));
+
+                    if message.target.kind.contains(&"proc-macro".to_string()) {
+                        let package_id = message.package_id;
+                        // Skip rmeta file
+                        if let Some(filename) = message.filenames.iter().find(|name| is_dylib(name))
+                        {
+                            let filename = AbsPathBuf::assert(filename.clone());
+                            let res = res.entry(package_id.repr.clone()).or_default();
+                            res.proc_macro_dylib_path = Some(filename);
+                        }
+                    }
+                }
+                Message::CompilerMessage(message) => {
+                    progress(message.target.name.clone());
                 }
+                Message::Unknown => (),
+                Message::BuildFinished(_) => {}
+                Message::TextLine(_) => {}
             }
         }
     }
+
+    for package in packages {
+        let build_data = res.entry(package.id.repr.clone()).or_default();
+        inject_cargo_env(package, build_data);
+        if let Some(out_dir) = &build_data.out_dir {
+            // NOTE: cargo and rustc seem to hide non-UTF-8 strings from env! and option_env!()
+            if let Some(out_dir) = out_dir.to_str().map(|s| s.to_owned()) {
+                build_data.envs.push(("OUT_DIR".to_string(), out_dir));
+            }
+        }
+    }
+
+    Ok(res)
 }
 
 // FIXME: File a better way to know if it is a dylib
@@ -173,7 +219,9 @@ fn is_dylib(path: &Path) -> bool {
 /// Recreates the compile-time environment variables that Cargo sets.
 ///
 /// Should be synced with <https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates>
-fn inject_cargo_env(package: &cargo_metadata::Package, env: &mut Vec<(String, String)>) {
+fn inject_cargo_env(package: &cargo_metadata::Package, build_data: &mut BuildData) {
+    let env = &mut build_data.envs;
+
     // FIXME: Missing variables:
     // CARGO_PKG_HOMEPAGE, CARGO_CRATE_NAME, CARGO_BIN_NAME, CARGO_BIN_EXE_<name>
 
diff --git a/crates/project_model/src/cargo_workspace.rs b/crates/project_model/src/cargo_workspace.rs
index c8a5333c4..f47898b9b 100644
--- a/crates/project_model/src/cargo_workspace.rs
+++ b/crates/project_model/src/cargo_workspace.rs
@@ -1,6 +1,6 @@
 //! FIXME: write short doc here
 
-use std::{convert::TryInto, ops, process::Command};
+use std::{convert::TryInto, ops, process::Command, sync::Arc};
 
 use anyhow::{Context, Result};
 use base_db::Edition;
@@ -9,7 +9,7 @@ use la_arena::{Arena, Idx};
 use paths::{AbsPath, AbsPathBuf};
 use rustc_hash::FxHashMap;
 
-use crate::build_data::{BuildData, BuildDataMap};
+use crate::build_data::BuildDataConfig;
 use crate::utf8_stdout;
 
 /// `CargoWorkspace` represents the logical structure of, well, a Cargo
@@ -27,6 +27,7 @@ pub struct CargoWorkspace {
     packages: Arena<PackageData>,
     targets: Arena<TargetData>,
     workspace_root: AbsPathBuf,
+    build_data_config: BuildDataConfig,
 }
 
 impl ops::Index<Package> for CargoWorkspace {
@@ -55,9 +56,6 @@ pub struct CargoConfig {
     /// This will be ignored if `cargo_all_features` is true.
     pub features: Vec<String>,
 
-    /// Runs cargo check on launch to figure out the correct values of OUT_DIR
-    pub load_out_dirs_from_check: bool,
-
     /// rustc target
     pub target: Option<String>,
 
@@ -94,8 +92,8 @@ pub struct PackageData {
     pub features: FxHashMap<String, Vec<String>>,
     /// List of features enabled on this package
     pub active_features: Vec<String>,
-    /// Build script related data for this package
-    pub build_data: BuildData,
+    // String representation of package id
+    pub id: String,
 }
 
 #[derive(Debug, Clone, Eq, PartialEq)]
@@ -228,12 +226,6 @@ impl CargoWorkspace {
             )
         })?;
 
-        let resources = if config.load_out_dirs_from_check {
-            BuildDataMap::new(cargo_toml, config, &meta.packages, progress)?
-        } else {
-            BuildDataMap::with_cargo_env(&meta.packages)
-        };
-
         let mut pkg_by_id = FxHashMap::default();
         let mut packages = Arena::default();
         let mut targets = Arena::default();
@@ -241,10 +233,7 @@ impl CargoWorkspace {
         let ws_members = &meta.workspace_members;
 
         meta.packages.sort_by(|a, b| a.id.cmp(&b.id));
-        for meta_pkg in meta.packages {
-            let id = meta_pkg.id.clone();
-            let build_data = resources.get(&id).cloned().unwrap_or_default();
-
+        for meta_pkg in &meta.packages {
             let cargo_metadata::Package { id, edition, name, manifest_path, version, .. } =
                 meta_pkg;
             let is_member = ws_members.contains(&id);
@@ -252,24 +241,24 @@ impl CargoWorkspace {
                 .parse::<Edition>()
                 .with_context(|| format!("Failed to parse edition {}", edition))?;
             let pkg = packages.alloc(PackageData {
-                name,
+                id: id.repr.clone(),
+                name: name.clone(),
                 version: version.to_string(),
-                manifest: AbsPathBuf::assert(manifest_path),
+                manifest: AbsPathBuf::assert(manifest_path.clone()),
                 targets: Vec::new(),
                 is_member,
                 edition,
                 dependencies: Vec::new(),
-                features: meta_pkg.features.into_iter().collect(),
+                features: meta_pkg.features.clone().into_iter().collect(),
                 active_features: Vec::new(),
-                build_data,
             });
             let pkg_data = &mut packages[pkg];
             pkg_by_id.insert(id, pkg);
-            for meta_tgt in meta_pkg.targets {
+            for meta_tgt in &meta_pkg.targets {
                 let is_proc_macro = meta_tgt.kind.as_slice() == ["proc-macro"];
                 let tgt = targets.alloc(TargetData {
                     package: pkg,
-                    name: meta_tgt.name,
+                    name: meta_tgt.name.clone(),
                     root: AbsPathBuf::assert(meta_tgt.src_path.clone()),
                     kind: TargetKind::new(meta_tgt.kind.as_slice()),
                     is_proc_macro,
@@ -308,7 +297,13 @@ impl CargoWorkspace {
         }
 
         let workspace_root = AbsPathBuf::assert(meta.workspace_root);
-        Ok(CargoWorkspace { packages, targets, workspace_root: workspace_root })
+        let build_data_config = BuildDataConfig::new(
+            cargo_toml.to_path_buf(),
+            config.clone(),
+            Arc::new(meta.packages.clone()),
+        );
+
+        Ok(CargoWorkspace { packages, targets, workspace_root, build_data_config })
     }
 
     pub fn packages<'a>(&'a self) -> impl Iterator<Item = Package> + ExactSizeIterator + 'a {
@@ -334,6 +329,10 @@ impl CargoWorkspace {
         }
     }
 
+    pub(crate) fn build_data_config(&self) -> &BuildDataConfig {
+        &self.build_data_config
+    }
+
     fn is_unique(&self, name: &str) -> bool {
         self.packages.iter().filter(|(_, v)| v.name == name).count() == 1
     }
diff --git a/crates/project_model/src/lib.rs b/crates/project_model/src/lib.rs
index 525c336e6..d712095a6 100644
--- a/crates/project_model/src/lib.rs
+++ b/crates/project_model/src/lib.rs
@@ -19,6 +19,7 @@ use paths::{AbsPath, AbsPathBuf};
 use rustc_hash::FxHashSet;
 
 pub use crate::{
+    build_data::{BuildDataCollector, BuildDataResult},
     cargo_workspace::{
         CargoConfig, CargoWorkspace, Package, PackageData, PackageDependency, Target, TargetData,
         TargetKind,
diff --git a/crates/project_model/src/workspace.rs b/crates/project_model/src/workspace.rs
index 559f4e7bf..c30861976 100644
--- a/crates/project_model/src/workspace.rs
+++ b/crates/project_model/src/workspace.rs
@@ -16,8 +16,13 @@ use proc_macro_api::ProcMacroClient;
 use rustc_hash::{FxHashMap, FxHashSet};
 
 use crate::{
-    cargo_workspace, cfg_flag::CfgFlag, rustc_cfg, sysroot::SysrootCrate, utf8_stdout, CargoConfig,
-    CargoWorkspace, ProjectJson, ProjectManifest, Sysroot, TargetKind,
+    build_data::{BuildData, BuildDataMap, BuildDataResult},
+    cargo_workspace,
+    cfg_flag::CfgFlag,
+    rustc_cfg,
+    sysroot::SysrootCrate,
+    utf8_stdout, BuildDataCollector, CargoConfig, CargoWorkspace, ProjectJson, ProjectManifest,
+    Sysroot, TargetKind,
 };
 
 /// `PackageRoot` describes a package root folder.
@@ -153,7 +158,7 @@ impl ProjectWorkspace {
     /// Returns the roots for the current `ProjectWorkspace`
     /// The return type contains the path and whether or not
     /// the root is a member of the current workspace
-    pub fn to_roots(&self) -> Vec<PackageRoot> {
+    pub fn to_roots(&self, build_data: Option<&BuildDataResult>) -> Vec<PackageRoot> {
         match self {
             ProjectWorkspace::Json { project, sysroot, rustc_cfg: _ } => project
                 .crates()
@@ -179,7 +184,12 @@ impl ProjectWorkspace {
                     let pkg_root = cargo[pkg].root().to_path_buf();
 
                     let mut include = vec![pkg_root.clone()];
-                    include.extend(cargo[pkg].build_data.out_dir.clone());
+                    include.extend(
+                        build_data
+                            .and_then(|it| it.get(cargo.workspace_root()))
+                            .and_then(|map| map.get(&cargo[pkg].id))
+                            .and_then(|it| it.out_dir.clone()),
+                    );
 
                     let mut exclude = vec![pkg_root.join(".git")];
                     if is_member {
@@ -219,6 +229,7 @@ impl ProjectWorkspace {
 
     pub fn to_crate_graph(
         &self,
+        build_data: Option<&BuildDataResult>,
         proc_macro_client: Option<&ProcMacroClient>,
         load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
     ) -> CrateGraph {
@@ -241,8 +252,10 @@ impl ProjectWorkspace {
                 &proc_macro_loader,
                 load,
                 cargo,
+                build_data.and_then(|it| it.get(cargo.workspace_root())),
                 sysroot,
                 rustc,
+                rustc.as_ref().zip(build_data).and_then(|(it, map)| map.get(it.workspace_root())),
             ),
         };
         if crate_graph.patch_cfg_if() {
@@ -252,6 +265,18 @@ impl ProjectWorkspace {
         }
         crate_graph
     }
+
+    pub fn collect_build_data_configs(&self, collector: &mut BuildDataCollector) {
+        match self {
+            ProjectWorkspace::Cargo { cargo, rustc, .. } => {
+                collector.add_config(&cargo.workspace_root(), cargo.build_data_config().clone());
+                if let Some(rustc) = rustc {
+                    collector.add_config(rustc.workspace_root(), rustc.build_data_config().clone());
+                }
+            }
+            _ => {}
+        }
+    }
 }
 
 fn project_json_to_crate_graph(
@@ -324,8 +349,10 @@ fn cargo_to_crate_graph(
     proc_macro_loader: &dyn Fn(&Path) -> Vec<ProcMacro>,
     load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
     cargo: &CargoWorkspace,
+    build_data_map: Option<&BuildDataMap>,
     sysroot: &Sysroot,
     rustc: &Option<CargoWorkspace>,
+    rustc_build_data_map: Option<&BuildDataMap>,
 ) -> CrateGraph {
     let _p = profile::span("cargo_to_crate_graph");
     let mut crate_graph = CrateGraph::default();
@@ -351,6 +378,7 @@ fn cargo_to_crate_graph(
                 let crate_id = add_target_crate_root(
                     &mut crate_graph,
                     &cargo[pkg],
+                    build_data_map.and_then(|it| it.get(&cargo[pkg].id)),
                     &cfg_options,
                     proc_macro_loader,
                     file_id,
@@ -427,6 +455,7 @@ fn cargo_to_crate_graph(
                     let crate_id = add_target_crate_root(
                         &mut crate_graph,
                         &rustc_workspace[pkg],
+                        rustc_build_data_map.and_then(|it| it.get(&rustc_workspace[pkg].id)),
                         &cfg_options,
                         proc_macro_loader,
                         file_id,
@@ -475,6 +504,7 @@ fn cargo_to_crate_graph(
 fn add_target_crate_root(
     crate_graph: &mut CrateGraph,
     pkg: &cargo_workspace::PackageData,
+    build_data: Option<&BuildData>,
     cfg_options: &CfgOptions,
     proc_macro_loader: &dyn Fn(&Path) -> Vec<ProcMacro>,
     file_id: FileId,
@@ -485,19 +515,22 @@ fn add_target_crate_root(
         for feature in pkg.active_features.iter() {
             opts.insert_key_value("feature".into(), feature.into());
         }
-        opts.extend(pkg.build_data.cfgs.iter().cloned());
+        if let Some(cfgs) = build_data.as_ref().map(|it| &it.cfgs) {
+            opts.extend(cfgs.iter().cloned());
+        }
         opts
     };
 
     let mut env = Env::default();
-    for (k, v) in &pkg.build_data.envs {
-        env.set(k, v.clone());
+    if let Some(envs) = build_data.map(|it| &it.envs) {
+        for (k, v) in envs {
+            env.set(k, v.clone());
+        }
     }
 
-    let proc_macro = pkg
-        .build_data
-        .proc_macro_dylib_path
+    let proc_macro = build_data
         .as_ref()
+        .and_then(|it| it.proc_macro_dylib_path.as_ref())
         .map(|it| proc_macro_loader(&it))
         .unwrap_or_default();
 
diff --git a/crates/rust-analyzer/src/bin/args.rs b/crates/rust-analyzer/src/bin/args.rs
index 2a532361d..3a7db6a18 100644
--- a/crates/rust-analyzer/src/bin/args.rs
+++ b/crates/rust-analyzer/src/bin/args.rs
@@ -50,6 +50,8 @@ FLAGS:
     -vv, --spammy
     -q,  --quiet      Set verbosity
 
+    --print-config-schema
+                      Dump a LSP config JSON schema
     --log-file <PATH> Log to the specified file instead of stderr
     --no-log-buffering
                       Flush log records to the file immediately
diff --git a/crates/rust-analyzer/src/cli/load_cargo.rs b/crates/rust-analyzer/src/cli/load_cargo.rs
index dbab4f5f4..e12e87180 100644
--- a/crates/rust-analyzer/src/cli/load_cargo.rs
+++ b/crates/rust-analyzer/src/cli/load_cargo.rs
@@ -6,7 +6,9 @@ use anyhow::Result;
 use crossbeam_channel::{unbounded, Receiver};
 use ide::{AnalysisHost, Change};
 use ide_db::base_db::CrateGraph;
-use project_model::{CargoConfig, ProcMacroClient, ProjectManifest, ProjectWorkspace};
+use project_model::{
+    BuildDataCollector, CargoConfig, ProcMacroClient, ProjectManifest, ProjectWorkspace,
+};
 use vfs::{loader::Handle, AbsPath, AbsPathBuf};
 
 use crate::reload::{ProjectFolders, SourceRootConfig};
@@ -18,11 +20,7 @@ pub fn load_cargo(
 ) -> Result<(AnalysisHost, vfs::Vfs)> {
     let root = AbsPathBuf::assert(std::env::current_dir()?.join(root));
     let root = ProjectManifest::discover_single(&root)?;
-    let ws = ProjectWorkspace::load(
-        root,
-        &CargoConfig { load_out_dirs_from_check, ..Default::default() },
-        &|_| {},
-    )?;
+    let ws = ProjectWorkspace::load(root, &CargoConfig::default(), &|_| {})?;
 
     let (sender, receiver) = unbounded();
     let mut vfs = vfs::Vfs::default();
@@ -39,14 +37,26 @@ pub fn load_cargo(
         None
     };
 
-    let crate_graph = ws.to_crate_graph(proc_macro_client.as_ref(), &mut |path: &AbsPath| {
-        let contents = loader.load_sync(path);
-        let path = vfs::VfsPath::from(path.to_path_buf());
-        vfs.set_file_contents(path.clone(), contents);
-        vfs.file_id(&path)
-    });
+    let build_data = if load_out_dirs_from_check {
+        let mut collector = BuildDataCollector::default();
+        ws.collect_build_data_configs(&mut collector);
+        Some(collector.collect(&|_| {})?)
+    } else {
+        None
+    };
+
+    let crate_graph = ws.to_crate_graph(
+        build_data.as_ref(),
+        proc_macro_client.as_ref(),
+        &mut |path: &AbsPath| {
+            let contents = loader.load_sync(path);
+            let path = vfs::VfsPath::from(path.to_path_buf());
+            vfs.set_file_contents(path.clone(), contents);
+            vfs.file_id(&path)
+        },
+    );
 
-    let project_folders = ProjectFolders::new(&[ws], &[]);
+    let project_folders = ProjectFolders::new(&[ws], &[], build_data.as_ref());
     loader.set_config(vfs::loader::Config { load: project_folders.load, watch: vec![] });
 
     log::debug!("crate graph: {:?}", crate_graph);
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 37487b6ac..cc0b22bff 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -469,6 +469,9 @@ impl Config {
     pub fn cargo_autoreload(&self) -> bool {
         self.data.cargo_autoreload
     }
+    pub fn load_out_dirs_from_check(&self) -> bool {
+        self.data.cargo_loadOutDirsFromCheck
+    }
     pub fn cargo(&self) -> CargoConfig {
         let rustc_source = self.data.rustcSource.as_ref().map(|it| self.root_path.join(&it));
 
@@ -476,7 +479,6 @@ impl Config {
             no_default_features: self.data.cargo_noDefaultFeatures,
             all_features: self.data.cargo_allFeatures,
             features: self.data.cargo_features.clone(),
-            load_out_dirs_from_check: self.data.cargo_loadOutDirsFromCheck,
             target: self.data.cargo_target.clone(),
             rustc_source,
             no_sysroot: self.data.cargo_noSysroot,
diff --git a/crates/rust-analyzer/src/global_state.rs b/crates/rust-analyzer/src/global_state.rs
index 442fbd14c..6374a9f3c 100644
--- a/crates/rust-analyzer/src/global_state.rs
+++ b/crates/rust-analyzer/src/global_state.rs
@@ -11,7 +11,9 @@ use ide::{Analysis, AnalysisHost, Change, FileId};
 use ide_db::base_db::{CrateId, VfsPath};
 use lsp_types::{SemanticTokens, Url};
 use parking_lot::{Mutex, RwLock};
-use project_model::{CargoWorkspace, ProcMacroClient, ProjectWorkspace, Target};
+use project_model::{
+    BuildDataCollector, BuildDataResult, CargoWorkspace, ProcMacroClient, ProjectWorkspace, Target,
+};
 use rustc_hash::FxHashMap;
 use vfs::AnchoredPathBuf;
 
@@ -33,7 +35,7 @@ use crate::{
 #[derive(Eq, PartialEq, Copy, Clone)]
 pub(crate) enum Status {
     Loading,
-    Ready,
+    Ready { partial: bool },
     Invalid,
     NeedsReload,
 }
@@ -79,7 +81,9 @@ pub(crate) struct GlobalState {
     pub(crate) source_root_config: SourceRootConfig,
     pub(crate) proc_macro_client: Option<ProcMacroClient>,
     pub(crate) workspaces: Arc<Vec<ProjectWorkspace>>,
-    pub(crate) fetch_workspaces_queue: OpQueue,
+    pub(crate) fetch_workspaces_queue: OpQueue<()>,
+    pub(crate) workspace_build_data: Option<BuildDataResult>,
+    pub(crate) fetch_build_data_queue: OpQueue<BuildDataCollector>,
     latest_requests: Arc<RwLock<LatestRequests>>,
 }
 
@@ -133,6 +137,8 @@ impl GlobalState {
             proc_macro_client: None,
             workspaces: Arc::new(Vec::new()),
             fetch_workspaces_queue: OpQueue::default(),
+            workspace_build_data: None,
+            fetch_build_data_queue: OpQueue::default(),
             latest_requests: Default::default(),
         }
     }
diff --git a/crates/rust-analyzer/src/lsp_ext.rs b/crates/rust-analyzer/src/lsp_ext.rs
index a85978737..670ca9a45 100644
--- a/crates/rust-analyzer/src/lsp_ext.rs
+++ b/crates/rust-analyzer/src/lsp_ext.rs
@@ -234,6 +234,7 @@ pub enum StatusNotification {}
 #[derive(Serialize, Deserialize)]
 pub enum Status {
     Loading,
+    ReadyPartial,
     Ready,
     NeedsReload,
     Invalid,
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 6d2475a59..f4fd1ac13 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -21,7 +21,7 @@ use crate::{
     global_state::{file_id_to_url, url_to_file_id, GlobalState, Status},
     handlers, lsp_ext,
     lsp_utils::{apply_document_changes, is_canceled, notification_is, Progress},
-    reload::ProjectWorkspaceProgress,
+    reload::{BuildDataProgress, ProjectWorkspaceProgress},
     Result,
 };
 
@@ -63,6 +63,7 @@ pub(crate) enum Task {
     Diagnostics(Vec<(FileId, Vec<lsp_types::Diagnostic>)>),
     PrimeCaches(PrimeCachesProgress),
     FetchWorkspace(ProjectWorkspaceProgress),
+    FetchBuildData(BuildDataProgress),
 }
 
 impl fmt::Debug for Event {
@@ -226,12 +227,33 @@ impl GlobalState {
                                 }
                                 ProjectWorkspaceProgress::End(workspaces) => {
                                     self.fetch_workspaces_completed();
-                                    self.switch_workspaces(workspaces);
+                                    self.switch_workspaces(workspaces, None);
                                     (Progress::End, None)
                                 }
                             };
                             self.report_progress("fetching", state, msg, None);
                         }
+                        Task::FetchBuildData(progress) => {
+                            let (state, msg) = match progress {
+                                BuildDataProgress::Begin => (Some(Progress::Begin), None),
+                                BuildDataProgress::Report(msg) => {
+                                    (Some(Progress::Report), Some(msg))
+                                }
+                                BuildDataProgress::End(collector) => {
+                                    self.fetch_build_data_completed();
+                                    let workspaces = (*self.workspaces)
+                                        .clone()
+                                        .into_iter()
+                                        .map(|it| Ok(it))
+                                        .collect();
+                                    self.switch_workspaces(workspaces, Some(collector));
+                                    (Some(Progress::End), None)
+                                }
+                            };
+                            if let Some(state) = state {
+                                self.report_progress("loading", state, msg, None);
+                            }
+                        }
                     }
                     // Coalesce multiple task events into one loop turn
                     task = match self.task_pool.receiver.try_recv() {
@@ -287,7 +309,11 @@ impl GlobalState {
                                     Progress::Report
                                 } else {
                                     assert_eq!(n_done, n_total);
-                                    self.transition(Status::Ready);
+                                    let status = Status::Ready {
+                                        partial: self.config.load_out_dirs_from_check()
+                                            && self.workspace_build_data.is_none(),
+                                    };
+                                    self.transition(status);
                                     Progress::End
                                 };
                                 self.report_progress(
@@ -372,13 +398,14 @@ impl GlobalState {
         }
 
         let state_changed = self.process_changes();
-        if prev_status == Status::Loading && self.status == Status::Ready {
+        let is_ready = matches!(self.status, Status::Ready { .. } );
+        if prev_status == Status::Loading && is_ready {
             for flycheck in &self.flycheck {
                 flycheck.update();
             }
         }
 
-        if self.status == Status::Ready && (state_changed || prev_status == Status::Loading) {
+        if is_ready && (state_changed || prev_status == Status::Loading) {
             self.update_file_notifications_on_threadpool();
 
             // Refresh semantic tokens if the client supports it.
@@ -408,6 +435,7 @@ impl GlobalState {
         }
 
         self.fetch_workspaces_if_needed();
+        self.fetch_build_data_if_needed();
 
         let loop_duration = loop_start.elapsed();
         if loop_duration > Duration::from_millis(100) {
diff --git a/crates/rust-analyzer/src/op_queue.rs b/crates/rust-analyzer/src/op_queue.rs
index 51d66f4b3..761b9ad39 100644
--- a/crates/rust-analyzer/src/op_queue.rs
+++ b/crates/rust-analyzer/src/op_queue.rs
@@ -1,22 +1,26 @@
 //! Bookkeeping to make sure only one long-running operation is executed.
 
-#[derive(Default)]
-pub(crate) struct OpQueue {
-    op_scheduled: bool,
+pub(crate) struct OpQueue<D> {
+    op_scheduled: Option<D>,
     op_in_progress: bool,
 }
 
-impl OpQueue {
-    pub(crate) fn request_op(&mut self) {
-        self.op_scheduled = true;
+impl<D> Default for OpQueue<D> {
+    fn default() -> Self {
+        Self { op_scheduled: None, op_in_progress: false }
     }
-    pub(crate) fn should_start_op(&mut self) -> bool {
-        if !self.op_in_progress && self.op_scheduled {
-            self.op_in_progress = true;
-            self.op_scheduled = false;
-            return true;
+}
+
+impl<D> OpQueue<D> {
+    pub(crate) fn request_op(&mut self, data: D) {
+        self.op_scheduled = Some(data);
+    }
+    pub(crate) fn should_start_op(&mut self) -> Option<D> {
+        if self.op_in_progress {
+            return None;
         }
-        false
+        self.op_in_progress = self.op_scheduled.is_some();
+        self.op_scheduled.take()
     }
     pub(crate) fn op_completed(&mut self) {
         assert!(self.op_in_progress);
diff --git a/crates/rust-analyzer/src/reload.rs b/crates/rust-analyzer/src/reload.rs
index ef73099cf..031a0cef4 100644
--- a/crates/rust-analyzer/src/reload.rs
+++ b/crates/rust-analyzer/src/reload.rs
@@ -4,7 +4,7 @@ use std::{mem, sync::Arc};
 use flycheck::{FlycheckConfig, FlycheckHandle};
 use ide::Change;
 use ide_db::base_db::{CrateGraph, SourceRoot, VfsPath};
-use project_model::{ProcMacroClient, ProjectWorkspace};
+use project_model::{BuildDataCollector, BuildDataResult, ProcMacroClient, ProjectWorkspace};
 use vfs::{file_set::FileSetConfig, AbsPath, AbsPathBuf, ChangeKind};
 
 use crate::{
@@ -22,6 +22,13 @@ pub(crate) enum ProjectWorkspaceProgress {
     End(Vec<anyhow::Result<ProjectWorkspace>>),
 }
 
+#[derive(Debug)]
+pub(crate) enum BuildDataProgress {
+    Begin,
+    Report(String),
+    End(anyhow::Result<BuildDataResult>),
+}
+
 impl GlobalState {
     pub(crate) fn update_configuration(&mut self, config: Config) {
         let _p = profile::span("GlobalState::update_configuration");
@@ -41,7 +48,7 @@ impl GlobalState {
         }
         match self.status {
             Status::Loading | Status::NeedsReload => return,
-            Status::Ready | Status::Invalid => (),
+            Status::Ready { .. } | Status::Invalid => (),
         }
         if self.config.cargo_autoreload() {
             self.fetch_workspaces_request();
@@ -89,7 +96,8 @@ impl GlobalState {
         if self.config.status_notification() {
             let lsp_status = match new_status {
                 Status::Loading => lsp_ext::Status::Loading,
-                Status::Ready => lsp_ext::Status::Ready,
+                Status::Ready { partial: true } => lsp_ext::Status::ReadyPartial,
+                Status::Ready { partial: false } => lsp_ext::Status::Ready,
                 Status::Invalid => lsp_ext::Status::Invalid,
                 Status::NeedsReload => lsp_ext::Status::NeedsReload,
             };
@@ -99,11 +107,37 @@ impl GlobalState {
         }
     }
 
+    pub(crate) fn fetch_build_data_request(&mut self, build_data_collector: BuildDataCollector) {
+        self.fetch_build_data_queue.request_op(build_data_collector);
+    }
+
+    pub(crate) fn fetch_build_data_if_needed(&mut self) {
+        let mut build_data_collector = match self.fetch_build_data_queue.should_start_op() {
+            Some(it) => it,
+            None => return,
+        };
+        self.task_pool.handle.spawn_with_sender(move |sender| {
+            sender.send(Task::FetchBuildData(BuildDataProgress::Begin)).unwrap();
+
+            let progress = {
+                let sender = sender.clone();
+                move |msg| {
+                    sender.send(Task::FetchBuildData(BuildDataProgress::Report(msg))).unwrap()
+                }
+            };
+            let res = build_data_collector.collect(&progress);
+            sender.send(Task::FetchBuildData(BuildDataProgress::End(res))).unwrap();
+        });
+    }
+    pub(crate) fn fetch_build_data_completed(&mut self) {
+        self.fetch_build_data_queue.op_completed()
+    }
+
     pub(crate) fn fetch_workspaces_request(&mut self) {
-        self.fetch_workspaces_queue.request_op()
+        self.fetch_workspaces_queue.request_op(())
     }
     pub(crate) fn fetch_workspaces_if_needed(&mut self) {
-        if !self.fetch_workspaces_queue.should_start_op() {
+        if self.fetch_workspaces_queue.should_start_op().is_none() {
             return;
         }
         log::info!("will fetch workspaces");
@@ -154,7 +188,11 @@ impl GlobalState {
         self.fetch_workspaces_queue.op_completed()
     }
 
-    pub(crate) fn switch_workspaces(&mut self, workspaces: Vec<anyhow::Result<ProjectWorkspace>>) {
+    pub(crate) fn switch_workspaces(
+        &mut self,
+        workspaces: Vec<anyhow::Result<ProjectWorkspace>>,
+        workspace_build_data: Option<anyhow::Result<BuildDataResult>>,
+    ) {
         let _p = profile::span("GlobalState::switch_workspaces");
         log::info!("will switch workspaces: {:?}", workspaces);
 
@@ -176,7 +214,20 @@ impl GlobalState {
             })
             .collect::<Vec<_>>();
 
-        if &*self.workspaces == &workspaces {
+        let workspace_build_data = match workspace_build_data {
+            Some(Ok(it)) => Some(it),
+            Some(Err(err)) => {
+                log::error!("failed to fetch build data: {:#}", err);
+                self.show_message(
+                    lsp_types::MessageType::Error,
+                    format!("rust-analyzer failed to fetch build data: {:#}", err),
+                );
+                return;
+            }
+            None => None,
+        };
+
+        if &*self.workspaces == &workspaces && self.workspace_build_data == workspace_build_data {
             return;
         }
 
@@ -189,7 +240,7 @@ impl GlobalState {
                 let registration_options = lsp_types::DidChangeWatchedFilesRegistrationOptions {
                     watchers: workspaces
                         .iter()
-                        .flat_map(ProjectWorkspace::to_roots)
+                        .flat_map(|it| it.to_roots(workspace_build_data.as_ref()))
                         .filter(|it| it.is_member)
                         .flat_map(|root| {
                             root.include.into_iter().map(|it| format!("{}/**/*.rs", it.display()))
@@ -215,7 +266,8 @@ impl GlobalState {
         let mut change = Change::new();
 
         let files_config = self.config.files();
-        let project_folders = ProjectFolders::new(&workspaces, &files_config.exclude);
+        let project_folders =
+            ProjectFolders::new(&workspaces, &files_config.exclude, workspace_build_data.as_ref());
 
         self.proc_macro_client = match self.config.proc_macro_srv() {
             None => None,
@@ -257,15 +309,28 @@ impl GlobalState {
                 res
             };
             for ws in workspaces.iter() {
-                crate_graph.extend(ws.to_crate_graph(self.proc_macro_client.as_ref(), &mut load));
+                crate_graph.extend(ws.to_crate_graph(
+                    workspace_build_data.as_ref(),
+                    self.proc_macro_client.as_ref(),
+                    &mut load,
+                ));
             }
 
             crate_graph
         };
         change.set_crate_graph(crate_graph);
 
+        if self.config.load_out_dirs_from_check() && workspace_build_data.is_none() {
+            let mut collector = BuildDataCollector::default();
+            for ws in &workspaces {
+                ws.collect_build_data_configs(&mut collector);
+            }
+            self.fetch_build_data_request(collector)
+        }
+
         self.source_root_config = project_folders.source_root_config;
         self.workspaces = Arc::new(workspaces);
+        self.workspace_build_data = workspace_build_data;
 
         self.analysis_host.apply_change(change);
         self.process_changes();
@@ -323,12 +388,13 @@ impl ProjectFolders {
     pub(crate) fn new(
         workspaces: &[ProjectWorkspace],
         global_excludes: &[AbsPathBuf],
+        build_data: Option<&BuildDataResult>,
     ) -> ProjectFolders {
         let mut res = ProjectFolders::default();
         let mut fsc = FileSetConfig::builder();
         let mut local_filesets = vec![];
 
-        for root in workspaces.iter().flat_map(|it| it.to_roots()) {
+        for root in workspaces.iter().flat_map(|it| it.to_roots(build_data)) {
             let file_set_roots: Vec<VfsPath> =
                 root.include.iter().cloned().map(VfsPath::from).collect();
 
diff --git a/docs/dev/lsp-extensions.md b/docs/dev/lsp-extensions.md
index 78d86f060..d7f287894 100644
--- a/docs/dev/lsp-extensions.md
+++ b/docs/dev/lsp-extensions.md
@@ -1,5 +1,5 @@
 <!---
-lsp_ext.rs hash: 91f2c62457e0a20f
+lsp_ext.rs hash: 7609fd6d7b4ab231
 
 If you need to change the above hash to make the test pass, please check if you
 need to adjust this doc as well and ping this  issue:
@@ -423,7 +423,7 @@ Reloads project information (that is, re-executes `cargo metadata`).
 
 ```typescript
 interface StatusParams {
-    status: "loading" | "ready" | "invalid" | "needsReload",
+    status: "loading" | "readyPartial" | "ready" | "invalid" | "needsReload",
 }
 ```
 
diff --git a/editors/code/src/ctx.ts b/editors/code/src/ctx.ts
index e7585184b..c07583cfa 100644
--- a/editors/code/src/ctx.ts
+++ b/editors/code/src/ctx.ts
@@ -74,6 +74,12 @@ export class Ctx {
                 this.statusBar.command = undefined;
                 this.statusBar.color = undefined;
                 break;
+            case "readyPartial":
+                this.statusBar.text = "rust-analyzer";
+                this.statusBar.tooltip = "Ready (Partial)";
+                this.statusBar.command = undefined;
+                this.statusBar.color = undefined;
+                break;
             case "ready":
                 this.statusBar.text = "rust-analyzer";
                 this.statusBar.tooltip = "Ready";
diff --git a/editors/code/src/lsp_ext.ts b/editors/code/src/lsp_ext.ts
index d21a3db86..2de1e427d 100644
--- a/editors/code/src/lsp_ext.ts
+++ b/editors/code/src/lsp_ext.ts
@@ -10,7 +10,7 @@ export interface AnalyzerStatusParams {
 export const analyzerStatus = new lc.RequestType<AnalyzerStatusParams, string, void>("rust-analyzer/analyzerStatus");
 export const memoryUsage = new lc.RequestType0<string, void>("rust-analyzer/memoryUsage");
 
-export type Status = "loading" | "ready" | "invalid" | "needsReload";
+export type Status = "loading" | "ready" | "readyPartial" | "invalid" | "needsReload";
 export interface StatusParams {
     status: Status;
 }