20 files changed, 259 insertions, 38 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 10ea55550..3bb1df05b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -928,6 +928,7 @@ dependencies = [
  "ra_cfg",
  "ra_prof",
  "ra_syntax",
+ "ra_tt",
  "relative-path",
  "rustc-hash",
  "salsa",
@@ -1082,6 +1083,13 @@ dependencies = [
 ]
 
 [[package]]
+name = "ra_proc_macro"
+version = "0.1.0"
+dependencies = [
+ "ra_tt",
+]
+
+[[package]]
 name = "ra_prof"
 version = "0.1.0"
 dependencies = [
@@ -1102,6 +1110,7 @@ dependencies = [
  "ra_cargo_watch",
  "ra_cfg",
  "ra_db",
+ "ra_proc_macro",
  "rustc-hash",
  "serde",
  "serde_json",
diff --git a/crates/ra_db/Cargo.toml b/crates/ra_db/Cargo.toml
index 878c22ba9..8ab409158 100644
--- a/crates/ra_db/Cargo.toml
+++ b/crates/ra_db/Cargo.toml
@@ -15,4 +15,5 @@ rustc-hash = "1.1.0"
 ra_syntax = { path = "../ra_syntax" }
 ra_cfg = { path = "../ra_cfg" }
 ra_prof = { path = "../ra_prof" }
+ra_tt = { path = "../ra_tt" }
 test_utils = { path = "../test_utils" }
diff --git a/crates/ra_db/src/fixture.rs b/crates/ra_db/src/fixture.rs
index 5e3e9203c..7777ce81e 100644
--- a/crates/ra_db/src/fixture.rs
+++ b/crates/ra_db/src/fixture.rs
@@ -70,6 +70,7 @@ fn with_single_file(db: &mut dyn SourceDatabaseExt, ra_fixture: &str) -> FileId
             meta.cfg,
             meta.env,
             Default::default(),
+            Default::default(),
         );
         crate_graph
     } else {
@@ -81,6 +82,7 @@ fn with_single_file(db: &mut dyn SourceDatabaseExt, ra_fixture: &str) -> FileId
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         crate_graph
     };
@@ -130,6 +132,7 @@ fn with_files(db: &mut dyn SourceDatabaseExt, fixture: &str) -> Option<FilePosit
                 meta.cfg,
                 meta.env,
                 Default::default(),
+                Default::default(),
             );
             let prev = crates.insert(krate.clone(), crate_id);
             assert!(prev.is_none());
@@ -167,6 +170,7 @@ fn with_files(db: &mut dyn SourceDatabaseExt, fixture: &str) -> Option<FilePosit
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
     } else {
         for (from, to) in crate_deps {
diff --git a/crates/ra_db/src/input.rs b/crates/ra_db/src/input.rs
index e371f849d..5ddce98c6 100644
--- a/crates/ra_db/src/input.rs
+++ b/crates/ra_db/src/input.rs
@@ -10,6 +10,7 @@ use std::{
     fmt, ops,
     path::{Path, PathBuf},
     str::FromStr,
+    sync::Arc,
 };
 
 use ra_cfg::CfgOptions;
@@ -19,6 +20,7 @@ use rustc_hash::FxHashSet;
 
 use crate::{RelativePath, RelativePathBuf};
 use fmt::Display;
+use ra_tt::TokenExpander;
 
 /// `FileId` is an integer which uniquely identifies a file. File paths are
 /// messy and system-dependent, so most of the code should work directly with
@@ -115,6 +117,22 @@ impl Display for CrateName {
     }
 }
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct ProcMacroId(pub u32);
+
+#[derive(Debug, Clone)]
+pub struct ProcMacro {
+    pub name: SmolStr,
+    pub expander: Arc<dyn TokenExpander>,
+}
+
+impl Eq for ProcMacro {}
+impl PartialEq for ProcMacro {
+    fn eq(&self, other: &ProcMacro) -> bool {
+        self.name == other.name && Arc::ptr_eq(&self.expander, &other.expander)
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct CrateData {
     pub root_file_id: FileId,
@@ -127,6 +145,7 @@ pub struct CrateData {
     pub env: Env,
     pub extern_source: ExternSource,
     pub dependencies: Vec<Dependency>,
+    pub proc_macro: Vec<ProcMacro>,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
@@ -166,7 +185,11 @@ impl CrateGraph {
         cfg_options: CfgOptions,
         env: Env,
         extern_source: ExternSource,
+        proc_macro: Vec<(SmolStr, Arc<dyn ra_tt::TokenExpander>)>,
     ) -> CrateId {
+        let proc_macro =
+            proc_macro.into_iter().map(|(name, it)| ProcMacro { name, expander: it }).collect();
+
         let data = CrateData {
             root_file_id: file_id,
             edition,
@@ -174,6 +197,7 @@ impl CrateGraph {
             cfg_options,
             env,
             extern_source,
+            proc_macro,
             dependencies: Vec::new(),
         };
         let crate_id = CrateId(self.arena.len() as u32);
@@ -345,6 +369,7 @@ mod tests {
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         let crate2 = graph.add_crate_root(
             FileId(2u32),
@@ -353,6 +378,7 @@ mod tests {
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         let crate3 = graph.add_crate_root(
             FileId(3u32),
@@ -361,6 +387,7 @@ mod tests {
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         assert!(graph.add_dep(crate1, CrateName::new("crate2").unwrap(), crate2).is_ok());
         assert!(graph.add_dep(crate2, CrateName::new("crate3").unwrap(), crate3).is_ok());
@@ -377,6 +404,7 @@ mod tests {
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         let crate2 = graph.add_crate_root(
             FileId(2u32),
@@ -385,6 +413,7 @@ mod tests {
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         let crate3 = graph.add_crate_root(
             FileId(3u32),
@@ -393,6 +422,7 @@ mod tests {
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         assert!(graph.add_dep(crate1, CrateName::new("crate2").unwrap(), crate2).is_ok());
         assert!(graph.add_dep(crate2, CrateName::new("crate3").unwrap(), crate3).is_ok());
@@ -408,6 +438,7 @@ mod tests {
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         let crate2 = graph.add_crate_root(
             FileId(2u32),
@@ -416,6 +447,7 @@ mod tests {
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         assert!(graph
             .add_dep(crate1, CrateName::normalize_dashes("crate-name-with-dashes"), crate2)
diff --git a/crates/ra_db/src/lib.rs b/crates/ra_db/src/lib.rs
index bac24e218..a06f59c14 100644
--- a/crates/ra_db/src/lib.rs
+++ b/crates/ra_db/src/lib.rs
@@ -12,7 +12,7 @@ pub use crate::{
     cancellation::Canceled,
     input::{
         CrateGraph, CrateId, CrateName, Dependency, Edition, Env, ExternSource, ExternSourceId,
-        FileId, SourceRoot, SourceRootId,
+        FileId, ProcMacroId, SourceRoot, SourceRootId,
     },
 };
 pub use relative_path::{RelativePath, RelativePathBuf};
diff --git a/crates/ra_hir_def/src/nameres/collector.rs b/crates/ra_hir_def/src/nameres/collector.rs
index 9c125f32f..8fe3f8617 100644
--- a/crates/ra_hir_def/src/nameres/collector.rs
+++ b/crates/ra_hir_def/src/nameres/collector.rs
@@ -11,7 +11,7 @@ use hir_expand::{
     HirFileId, MacroCallId, MacroDefId, MacroDefKind,
 };
 use ra_cfg::CfgOptions;
-use ra_db::{CrateId, FileId};
+use ra_db::{CrateId, FileId, ProcMacroId};
 use ra_syntax::ast;
 use rustc_hash::FxHashMap;
 use test_utils::tested_by;
@@ -53,6 +53,16 @@ pub(super) fn collect_defs(db: &dyn DefDatabase, mut def_map: CrateDefMap) -> Cr
     }
 
     let cfg_options = &crate_graph[def_map.krate].cfg_options;
+    let proc_macros = &crate_graph[def_map.krate].proc_macro;
+    let proc_macros = proc_macros
+        .iter()
+        .enumerate()
+        .map(|(idx, it)| {
+            // FIXME: a hacky way to create a Name from string.
+            let name = tt::Ident { text: it.name.clone(), id: tt::TokenId::unspecified() };
+            (name.as_name(), ProcMacroExpander::new(def_map.krate, ProcMacroId(idx as u32)))
+        })
+        .collect();
 
     let mut collector = DefCollector {
         db,
@@ -65,9 +75,7 @@ pub(super) fn collect_defs(db: &dyn DefDatabase, mut def_map: CrateDefMap) -> Cr
         unexpanded_attribute_macros: Vec::new(),
         mod_dirs: FxHashMap::default(),
         cfg_options,
-
-        // FIXME: pass proc-macro from crate-graph
-        proc_macros: Default::default(),
+        proc_macros,
     };
     collector.collect();
     collector.finish()
diff --git a/crates/ra_hir_expand/src/proc_macro.rs b/crates/ra_hir_expand/src/proc_macro.rs
index a8dee2052..4d270e0de 100644
--- a/crates/ra_hir_expand/src/proc_macro.rs
+++ b/crates/ra_hir_expand/src/proc_macro.rs
@@ -1,33 +1,32 @@
 //! Proc Macro Expander stub
 
-use crate::{db::AstDatabase, LazyMacroId, MacroCallKind, MacroCallLoc};
-use ra_db::CrateId;
+use crate::{db::AstDatabase, LazyMacroId};
+use ra_db::{CrateId, ProcMacroId};
 
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
 pub struct ProcMacroExpander {
     krate: CrateId,
+    proc_macro_id: ProcMacroId,
 }
 
 impl ProcMacroExpander {
-    pub fn new(krate: CrateId) -> ProcMacroExpander {
-        ProcMacroExpander { krate }
+    pub fn new(krate: CrateId, proc_macro_id: ProcMacroId) -> ProcMacroExpander {
+        ProcMacroExpander { krate, proc_macro_id }
     }
 
     pub fn expand(
         &self,
         db: &dyn AstDatabase,
-        id: LazyMacroId,
-        _tt: &tt::Subtree,
+        _id: LazyMacroId,
+        tt: &tt::Subtree,
     ) -> Result<tt::Subtree, mbe::ExpandError> {
-        let loc: MacroCallLoc = db.lookup_intern_macro(id);
-        let name = match loc.kind {
-            MacroCallKind::FnLike(_) => return Err(mbe::ExpandError::ConversionError),
-            MacroCallKind::Attr(_, name) => name,
-        };
+        let krate_graph = db.crate_graph();
+        let proc_macro = krate_graph[self.krate]
+            .proc_macro
+            .get(self.proc_macro_id.0 as usize)
+            .clone()
+            .ok_or_else(|| mbe::ExpandError::ConversionError)?;
 
-        log::debug!("Proc-macro-expanding name = {}", name);
-
-        // Return nothing for now
-        return Ok(tt::Subtree::default());
+        proc_macro.expander.expand(&tt, None).map_err(mbe::ExpandError::from)
     }
 }
diff --git a/crates/ra_ide/src/lib.rs b/crates/ra_ide/src/lib.rs
index 5ab06c6cf..e43414985 100644
--- a/crates/ra_ide/src/lib.rs
+++ b/crates/ra_ide/src/lib.rs
@@ -213,6 +213,7 @@ impl Analysis {
             cfg_options,
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         change.add_file(source_root, file_id, "main.rs".into(), Arc::new(text));
         change.set_crate_graph(crate_graph);
diff --git a/crates/ra_ide/src/mock_analysis.rs b/crates/ra_ide/src/mock_analysis.rs
index 2cf77a31f..2c13f206a 100644
--- a/crates/ra_ide/src/mock_analysis.rs
+++ b/crates/ra_ide/src/mock_analysis.rs
@@ -103,6 +103,7 @@ impl MockAnalysis {
                     cfg_options,
                     Env::default(),
                     Default::default(),
+                    Default::default(),
                 ));
             } else if path.ends_with("/lib.rs") {
                 let crate_name = path.parent().unwrap().file_name().unwrap();
@@ -113,6 +114,7 @@ impl MockAnalysis {
                     cfg_options,
                     Env::default(),
                     Default::default(),
+                    Default::default(),
                 );
                 if let Some(root_crate) = root_crate {
                     crate_graph
diff --git a/crates/ra_ide/src/parent_module.rs b/crates/ra_ide/src/parent_module.rs
index 76d130b9b..958b92bed 100644
--- a/crates/ra_ide/src/parent_module.rs
+++ b/crates/ra_ide/src/parent_module.rs
@@ -137,6 +137,7 @@ mod tests {
             CfgOptions::default(),
             Env::default(),
             Default::default(),
+            Default::default(),
         );
         let mut change = AnalysisChange::new();
         change.set_crate_graph(crate_graph);
diff --git a/crates/ra_mbe/src/lib.rs b/crates/ra_mbe/src/lib.rs
index 6a9037bfc..535b7daa0 100644
--- a/crates/ra_mbe/src/lib.rs
+++ b/crates/ra_mbe/src/lib.rs
@@ -28,6 +28,13 @@ pub enum ExpandError {
     BindingError(String),
     ConversionError,
     InvalidRepeat,
+    ProcMacroError(tt::ExpansionError),
+}
+
+impl From<tt::ExpansionError> for ExpandError {
+    fn from(it: tt::ExpansionError) -> Self {
+        ExpandError::ProcMacroError(it)
+    }
 }
 
 pub use crate::syntax_bridge::{
diff --git a/crates/ra_proc_macro/Cargo.toml b/crates/ra_proc_macro/Cargo.toml
new file mode 100644
index 000000000..bc2c37296
--- /dev/null
+++ b/crates/ra_proc_macro/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+edition = "2018"
+name = "ra_proc_macro"
+version = "0.1.0"
+authors = ["rust-analyzer developers"]
+publish = false
+
+[lib]
+doctest = false
+
+[dependencies]
+ra_tt = { path = "../ra_tt" }
diff --git a/crates/ra_proc_macro/src/lib.rs b/crates/ra_proc_macro/src/lib.rs
new file mode 100644
index 000000000..5e21dd487
--- /dev/null
+++ b/crates/ra_proc_macro/src/lib.rs
@@ -0,0 +1,59 @@
+//! Client-side Proc-Macro crate
+//!
+//! We separate proc-macro expanding logic to an extern program to allow
+//! different implementations (e.g. wasm or dylib loading). And this crate
+//! is used to provide basic infrastructure  for communication between two
+//! processes: Client (RA itself), Server (the external program)
+
+use ra_tt::{SmolStr, Subtree};
+use std::{
+    path::{Path, PathBuf},
+    sync::Arc,
+};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ProcMacroProcessExpander {
+    process: Arc<ProcMacroProcessSrv>,
+    name: SmolStr,
+}
+
+impl ra_tt::TokenExpander for ProcMacroProcessExpander {
+    fn expand(
+        &self,
+        _subtree: &Subtree,
+        _attr: Option<&Subtree>,
+    ) -> Result<Subtree, ra_tt::ExpansionError> {
+        // FIXME: do nothing for now
+        Ok(Subtree::default())
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ProcMacroProcessSrv {
+    path: PathBuf,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ProcMacroClient {
+    Process { process: Arc<ProcMacroProcessSrv> },
+    Dummy,
+}
+
+impl ProcMacroClient {
+    pub fn extern_process(process_path: &Path) -> ProcMacroClient {
+        let process = ProcMacroProcessSrv { path: process_path.into() };
+        ProcMacroClient::Process { process: Arc::new(process) }
+    }
+
+    pub fn dummy() -> ProcMacroClient {
+        ProcMacroClient::Dummy
+    }
+
+    pub fn by_dylib_path(
+        &self,
+        _dylib_path: &Path,
+    ) -> Vec<(SmolStr, Arc<dyn ra_tt::TokenExpander>)> {
+        // FIXME: return empty for now
+        vec![]
+    }
+}
diff --git a/crates/ra_project_model/Cargo.toml b/crates/ra_project_model/Cargo.toml
index 22300548a..cdcdd63c9 100644
--- a/crates/ra_project_model/Cargo.toml
+++ b/crates/ra_project_model/Cargo.toml
@@ -17,6 +17,7 @@ ra_arena = { path = "../ra_arena" }
 ra_db = { path = "../ra_db" }
 ra_cfg = { path = "../ra_cfg" }
 ra_cargo_watch = { path = "../ra_cargo_watch" }
+ra_proc_macro =  { path = "../ra_proc_macro" }
 
 serde = { version = "1.0.104", features = ["derive"] }
 serde_json = "1.0.48"
diff --git a/crates/ra_project_model/src/cargo_workspace.rs b/crates/ra_project_model/src/cargo_workspace.rs
index c7f9bd873..291594e2a 100644
--- a/crates/ra_project_model/src/cargo_workspace.rs
+++ b/crates/ra_project_model/src/cargo_workspace.rs
@@ -83,6 +83,7 @@ pub struct PackageData {
     pub edition: Edition,
     pub features: Vec<String>,
     pub out_dir: Option<PathBuf>,
+    pub proc_macro_dylib_path: Option<PathBuf>,
 }
 
 #[derive(Debug, Clone)]
@@ -158,8 +159,11 @@ impl CargoWorkspace {
         })?;
 
         let mut out_dir_by_id = FxHashMap::default();
+        let mut proc_macro_dylib_paths = FxHashMap::default();
         if cargo_features.load_out_dirs_from_check {
-            out_dir_by_id = load_out_dirs(cargo_toml, cargo_features);
+            let resources = load_extern_resources(cargo_toml, cargo_features);
+            out_dir_by_id = resources.out_dirs;
+            proc_macro_dylib_paths = resources.proc_dylib_paths;
         }
 
         let mut pkg_by_id = FxHashMap::default();
@@ -183,6 +187,7 @@ impl CargoWorkspace {
                 dependencies: Vec::new(),
                 features: Vec::new(),
                 out_dir: out_dir_by_id.get(&id).cloned(),
+                proc_macro_dylib_path: proc_macro_dylib_paths.get(&id).cloned(),
             });
             let pkg_data = &mut packages[pkg];
             pkg_by_id.insert(id, pkg);
@@ -246,10 +251,13 @@ impl CargoWorkspace {
     }
 }
 
-pub fn load_out_dirs(
-    cargo_toml: &Path,
-    cargo_features: &CargoFeatures,
-) -> FxHashMap<PackageId, PathBuf> {
+#[derive(Debug, Clone, Default)]
+pub struct ExternResources {
+    out_dirs: FxHashMap<PackageId, PathBuf>,
+    proc_dylib_paths: FxHashMap<PackageId, PathBuf>,
+}
+
+pub fn load_extern_resources(cargo_toml: &Path, cargo_features: &CargoFeatures) -> ExternResources {
     let mut args: Vec<String> = vec![
         "check".to_string(),
         "--message-format=json".to_string(),
@@ -267,14 +275,21 @@ pub fn load_out_dirs(
         args.extend(cargo_features.features.iter().cloned());
     }
 
-    let mut acc = FxHashMap::default();
+    let mut acc = ExternResources::default();
     let res = run_cargo(&args, cargo_toml.parent(), &mut |message| {
         match message {
             Message::BuildScriptExecuted(BuildScript { package_id, out_dir, .. }) => {
-                acc.insert(package_id, out_dir);
+                acc.out_dirs.insert(package_id, out_dir);
             }
 
-            Message::CompilerArtifact(_) => (),
+            Message::CompilerArtifact(message) => {
+                if message.target.kind.contains(&"proc-macro".to_string()) {
+                    let package_id = message.package_id;
+                    if let Some(filename) = message.filenames.get(0) {
+                        acc.proc_dylib_paths.insert(package_id, filename.clone());
+                    }
+                }
+            }
             Message::CompilerMessage(_) => (),
             Message::Unknown => (),
         }
diff --git a/crates/ra_project_model/src/json_project.rs b/crates/ra_project_model/src/json_project.rs
index 336446e58..b030c8a6a 100644
--- a/crates/ra_project_model/src/json_project.rs
+++ b/crates/ra_project_model/src/json_project.rs
@@ -23,6 +23,7 @@ pub struct Crate {
     pub(crate) atom_cfgs: FxHashSet<String>,
     pub(crate) key_value_cfgs: FxHashMap<String, String>,
     pub(crate) out_dir: Option<PathBuf>,
+    pub(crate) proc_macro_dylib_path: Option<PathBuf>,
 }
 
 #[derive(Clone, Copy, Debug, Deserialize)]
diff --git a/crates/ra_project_model/src/lib.rs b/crates/ra_project_model/src/lib.rs
index a3ef9acdc..444d3bb3f 100644
--- a/crates/ra_project_model/src/lib.rs
+++ b/crates/ra_project_model/src/lib.rs
@@ -23,6 +23,7 @@ pub use crate::{
     json_project::JsonProject,
     sysroot::Sysroot,
 };
+pub use ra_proc_macro::ProcMacroClient;
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub struct CargoTomlNotFoundError {
@@ -173,6 +174,29 @@ impl ProjectWorkspace {
         }
     }
 
+    pub fn proc_macro_dylib_paths(&self) -> Vec<PathBuf> {
+        match self {
+            ProjectWorkspace::Json { project } => {
+                let mut proc_macro_dylib_paths = Vec::with_capacity(project.crates.len());
+                for krate in &project.crates {
+                    if let Some(out_dir) = &krate.proc_macro_dylib_path {
+                        proc_macro_dylib_paths.push(out_dir.to_path_buf());
+                    }
+                }
+                proc_macro_dylib_paths
+            }
+            ProjectWorkspace::Cargo { cargo, sysroot: _sysroot } => {
+                let mut proc_macro_dylib_paths = Vec::with_capacity(cargo.packages().len());
+                for pkg in cargo.packages() {
+                    if let Some(dylib_path) = &cargo[pkg].proc_macro_dylib_path {
+                        proc_macro_dylib_paths.push(dylib_path.to_path_buf());
+                    }
+                }
+                proc_macro_dylib_paths
+            }
+        }
+    }
+
     pub fn n_packages(&self) -> usize {
         match self {
             ProjectWorkspace::Json { project } => project.crates.len(),
@@ -186,6 +210,7 @@ impl ProjectWorkspace {
         &self,
         default_cfg_options: &CfgOptions,
         extern_source_roots: &FxHashMap<PathBuf, ExternSourceId>,
+        proc_macro_client: &ProcMacroClient,
         load: &mut dyn FnMut(&Path) -> Option<FileId>,
     ) -> CrateGraph {
         let mut crate_graph = CrateGraph::default();
@@ -219,7 +244,10 @@ impl ProjectWorkspace {
                                 extern_source.set_extern_path(&out_dir, extern_source_id);
                             }
                         }
-
+                        let proc_macro = krate
+                            .proc_macro_dylib_path
+                            .clone()
+                            .map(|it| proc_macro_client.by_dylib_path(&it));
                         // FIXME: No crate name in json definition such that we cannot add OUT_DIR to env
                         crates.insert(
                             crate_id,
@@ -231,6 +259,7 @@ impl ProjectWorkspace {
                                 cfg_options,
                                 env,
                                 extern_source,
+                                proc_macro.unwrap_or_default(),
                             ),
                         );
                     }
@@ -270,6 +299,8 @@ impl ProjectWorkspace {
 
                         let env = Env::default();
                         let extern_source = ExternSource::default();
+                        let proc_macro = vec![];
+
                         let crate_id = crate_graph.add_crate_root(
                             file_id,
                             Edition::Edition2018,
@@ -280,6 +311,7 @@ impl ProjectWorkspace {
                             cfg_options,
                             env,
                             extern_source,
+                            proc_macro,
                         );
                         sysroot_crates.insert(krate, crate_id);
                     }
@@ -327,6 +359,12 @@ impl ProjectWorkspace {
                                     extern_source.set_extern_path(&out_dir, extern_source_id);
                                 }
                             }
+                            let proc_macro = cargo[pkg]
+                                .proc_macro_dylib_path
+                                .as_ref()
+                                .map(|it| proc_macro_client.by_dylib_path(&it))
+                                .unwrap_or_default();
+
                             let crate_id = crate_graph.add_crate_root(
                                 file_id,
                                 edition,
@@ -334,6 +372,7 @@ impl ProjectWorkspace {
                                 cfg_options,
                                 env,
                                 extern_source,
+                                proc_macro.clone(),
                             );
                             if cargo[tgt].kind == TargetKind::Lib {
                                 lib_tgt = Some((crate_id, cargo[tgt].name.clone()));
diff --git a/crates/ra_tt/src/lib.rs b/crates/ra_tt/src/lib.rs
index 1e2fb8b91..1015ce0a6 100644
--- a/crates/ra_tt/src/lib.rs
+++ b/crates/ra_tt/src/lib.rs
@@ -14,9 +14,12 @@ macro_rules! impl_froms {
     }
 }
 
-use std::fmt;
+use std::{
+    fmt::{self, Debug},
+    panic::RefUnwindSafe,
+};
 
-use smol_str::SmolStr;
+pub use smol_str::SmolStr;
 
 /// Represents identity of the token.
 ///
@@ -184,3 +187,11 @@ impl Subtree {
 }
 
 pub mod buffer;
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum ExpansionError {}
+
+pub trait TokenExpander: Debug + Send + Sync + RefUnwindSafe {
+    fn expand(&self, subtree: &Subtree, attrs: Option<&Subtree>)
+        -> Result<Subtree, ExpansionError>;
+}
diff --git a/crates/rust-analyzer/src/cli/load_cargo.rs b/crates/rust-analyzer/src/cli/load_cargo.rs
index 54e2fa1a7..832f04226 100644
--- a/crates/rust-analyzer/src/cli/load_cargo.rs
+++ b/crates/rust-analyzer/src/cli/load_cargo.rs
@@ -7,7 +7,9 @@ use anyhow::Result;
 use crossbeam_channel::{unbounded, Receiver};
 use ra_db::{ExternSourceId, FileId, SourceRootId};
 use ra_ide::{AnalysisChange, AnalysisHost};
-use ra_project_model::{get_rustc_cfg_options, CargoFeatures, PackageRoot, ProjectWorkspace};
+use ra_project_model::{
+    get_rustc_cfg_options, CargoFeatures, PackageRoot, ProcMacroClient, ProjectWorkspace,
+};
 use ra_vfs::{RootEntry, Vfs, VfsChange, VfsTask, Watch};
 use rustc_hash::{FxHashMap, FxHashSet};
 
@@ -67,7 +69,9 @@ pub(crate) fn load_cargo(
             (source_root_id, project_root)
         })
         .collect::<FxHashMap<_, _>>();
-    let host = load(&source_roots, ws, &mut vfs, receiver, extern_dirs);
+
+    let proc_macro_client = ProcMacroClient::dummy();
+    let host = load(&source_roots, ws, &mut vfs, receiver, extern_dirs, &proc_macro_client);
     Ok((host, source_roots))
 }
 
@@ -77,6 +81,7 @@ pub(crate) fn load(
     vfs: &mut Vfs,
     receiver: Receiver<VfsTask>,
     extern_dirs: FxHashSet<PathBuf>,
+    proc_macro_client: &ProcMacroClient,
 ) -> AnalysisHost {
     let lru_cap = std::env::var("RA_LRU_CAP").ok().and_then(|it| it.parse::<usize>().ok());
     let mut host = AnalysisHost::new(lru_cap);
@@ -143,12 +148,16 @@ pub(crate) fn load(
         opts
     };
 
-    let crate_graph =
-        ws.to_crate_graph(&default_cfg_options, &extern_source_roots, &mut |path: &Path| {
+    let crate_graph = ws.to_crate_graph(
+        &default_cfg_options,
+        &extern_source_roots,
+        proc_macro_client,
+        &mut |path: &Path| {
             let vfs_file = vfs.load(path);
             log::debug!("vfs file {:?} -> {:?}", path, vfs_file);
             vfs_file.map(vfs_file_to_id)
-        });
+        },
+    );
     log::debug!("crate graph: {:?}", crate_graph);
     analysis_change.set_crate_graph(crate_graph);
 
diff --git a/crates/rust-analyzer/src/world.rs b/crates/rust-analyzer/src/world.rs
index c4244fee2..de85bb017 100644
--- a/crates/rust-analyzer/src/world.rs
+++ b/crates/rust-analyzer/src/world.rs
@@ -16,7 +16,7 @@ use ra_ide::{
     Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, InlayHintsOptions, LibraryData,
     SourceRootId,
 };
-use ra_project_model::{get_rustc_cfg_options, ProjectWorkspace};
+use ra_project_model::{get_rustc_cfg_options, ProcMacroClient, ProjectWorkspace};
 use ra_vfs::{LineEndings, RootEntry, Vfs, VfsChange, VfsFile, VfsRoot, VfsTask, Watch};
 use relative_path::RelativePathBuf;
 
@@ -150,9 +150,19 @@ impl WorldState {
             vfs_file.map(|f| FileId(f.0))
         };
 
+        let proc_macro_client =
+            ProcMacroClient::extern_process(std::path::Path::new("ra_proc_macro_srv"));
+
         workspaces
             .iter()
-            .map(|ws| ws.to_crate_graph(&default_cfg_options, &extern_source_roots, &mut load))
+            .map(|ws| {
+                ws.to_crate_graph(
+                    &default_cfg_options,
+                    &extern_source_roots,
+                    &proc_macro_client,
+                    &mut load,
+                )
+            })
             .for_each(|graph| {
                 crate_graph.extend(graph);
             });