Move TokenExpander to base_db and rename it

It's only used to break the dependency to proc_macro_api

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 +150,16 @@ pub enum ProcMacroKind {
     Attr,
 }
 
+pub trait ProcMacroExpander: fmt::Debug + Send + Sync + RefUnwindSafe {
+    fn expand(&self, subtree: &Subtree, attrs: Option<&Subtree>)
+        -> 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 {}

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;

crates/proc_macro_api/src/lib.rs

@@ -39,7 +39,7 @@ impl PartialEq for ProcMacroProcessExpander {
     }
 }
 
-impl tt::TokenExpander for ProcMacroProcessExpander {
+impl base_db::ProcMacroExpander for ProcMacroProcessExpander {
     fn expand(
         &self,
         subtree: &Subtree,
@@ -90,7 +90,7 @@ impl ProcMacroClient {
                     ProcMacroKind::FuncLike => base_db::ProcMacroKind::FuncLike,
                     ProcMacroKind::Attr => base_db::ProcMacroKind::Attr,
                 };
-                let expander: Arc<dyn tt::TokenExpander> = Arc::new(ProcMacroProcessExpander {
+                let expander = Arc::new(ProcMacroProcessExpander {
                     process: self.process.clone(),
                     name: name.clone(),
                     dylib_path: dylib_path.into(),

crates/tt/src/lib.rs

@@ -1,7 +1,7 @@
 //! `tt` crate defines a `TokenTree` data structure: this is the interface (both
 //! input and output) of macros. It closely mirrors `proc_macro` crate's
 //! `TokenTree`.
-use std::{fmt, panic::RefUnwindSafe};
+use std::fmt;
 
 use stdx::impl_from;
 
@@ -247,8 +247,3 @@ impl fmt::Display for ExpansionError {
         }
     }
 }
-
-pub trait TokenExpander: fmt::Debug + Send + Sync + RefUnwindSafe {
-    fn expand(&self, subtree: &Subtree, attrs: Option<&Subtree>)
-        -> Result<Subtree, ExpansionError>;
-}