2 files changed, 17 insertions, 4 deletions

diff --git a/crates/base_db/src/input.rs b/crates/base_db/src/input.rs
index cda5e57dc..9567bcc42 100644
--- a/crates/base_db/src/input.rs
+++ b/crates/base_db/src/input.rs
@@ -6,12 +6,12 @@
 //! actual IO. See `vfs` and `project_model` in the `rust-analyzer` crate for how
 //! actual IO is done and lowered to input.
 
-use std::{fmt, iter::FromIterator, ops, str::FromStr, sync::Arc};
+use std::{fmt, iter::FromIterator, ops, panic::RefUnwindSafe, str::FromStr, sync::Arc};
 
 use cfg::CfgOptions;
 use rustc_hash::{FxHashMap, FxHashSet};
 use syntax::SmolStr;
-use tt::TokenExpander;
+use tt::{ExpansionError, Subtree};
 use vfs::{file_set::FileSet, FileId, VfsPath};
 
 /// Files are grouped into source roots. A source root is a directory on the
@@ -150,11 +150,20 @@ pub enum ProcMacroKind {
     Attr,
 }
 
+pub trait ProcMacroExpander: fmt::Debug + Send + Sync + RefUnwindSafe {
+    fn expand(
+        &self,
+        subtree: &Subtree,
+        attrs: Option<&Subtree>,
+        env: &Env,
+    ) -> Result<Subtree, ExpansionError>;
+}
+
 #[derive(Debug, Clone)]
 pub struct ProcMacro {
     pub name: SmolStr,
     pub kind: ProcMacroKind,
-    pub expander: Arc<dyn TokenExpander>,
+    pub expander: Arc<dyn ProcMacroExpander>,
 }
 
 impl Eq for ProcMacro {}
@@ -413,6 +422,10 @@ impl Env {
     pub fn get(&self, env: &str) -> Option<String> {
         self.entries.get(env).cloned()
     }
+
+    pub fn iter(&self) -> impl Iterator<Item = (&str, &str)> {
+        self.entries.iter().map(|(k, v)| (k.as_str(), v.as_str()))
+    }
 }
 
 #[derive(Debug)]
diff --git a/crates/base_db/src/lib.rs b/crates/base_db/src/lib.rs
index 595f28ada..5f77a0b1f 100644
--- a/crates/base_db/src/lib.rs
+++ b/crates/base_db/src/lib.rs
@@ -14,7 +14,7 @@ pub use crate::{
     change::Change,
     input::{
         CrateData, CrateDisplayName, CrateGraph, CrateId, CrateName, Dependency, Edition, Env,
-        ProcMacro, ProcMacroId, ProcMacroKind, SourceRoot, SourceRootId,
+        ProcMacro, ProcMacroExpander, ProcMacroId, ProcMacroKind, SourceRoot, SourceRootId,
     },
 };
 pub use salsa;